3 ways energy can travel

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Three ways to travel at (nearly) the speed of light.

Katy Mersmann

1) electromagnetic fields, 2) magnetic explosions, 3) wave-particle interactions.

One hundred years ago today, on May 29, 1919, measurements of a solar eclipse offered verification for Einstein’s theory of general relativity. Even before that, Einstein had developed the theory of special relativity, which revolutionized the way we understand light. To this day, it provides guidance on understanding how particles move through space — a key area of research to keep spacecraft and astronauts safe from radiation.

The theory of special relativity showed that particles of light, photons, travel through a vacuum at a constant pace of 670,616,629 miles per hour — a speed that’s immensely difficult to achieve and impossible to surpass in that environment. Yet all across space, from black holes to our near-Earth environment, particles are, in fact, being accelerated to incredible speeds, some even reaching 99.9% the speed of light.

One of NASA’s jobs is to better understand how these particles are accelerated. Studying these superfast, or relativistic, particles can ultimately help protect missions exploring the solar system, traveling to the Moon, and they can teach us more about our galactic neighborhood: A well-aimed near-light-speed particle can trip onboard electronics and too many at once could have negative radiation effects on space-faring astronauts as they travel to the Moon — or beyond.

Here are three ways that acceleration happens.

Most of the processes that accelerate particles to relativistic speeds work with electromagnetic fields — the same force that keeps magnets on your fridge. The two components, electric and magnetic fields, like two sides of the same coin, work together to whisk particles at relativistic speeds throughout the universe.

In essence, electromagnetic fields accelerate charged particles because the particles feel a force in an electromagnetic field that pushes them along, similar to how gravity pulls at objects with mass. In the right conditions, electromagnetic fields can accelerate particles at near-light-speed.

On Earth, electric fields are often specifically harnessed on smaller scales to speed up particles in laboratories. Particle accelerators, like the Large Hadron Collider and Fermilab, use pulsed electromagnetic fields to accelerate charged particles up to 99.99999896% the speed of light. At these speeds, the particles can be smashed together to produce collisions with immense amounts of energy. This allows scientists to look for elementary particles and understand what the universe was like in the very first fractions of a second after the Big Bang. 

Download related video from NASA Goddard’s Scientific Visualization Studio

Magnetic fields are everywhere in space, encircling Earth and spanning the solar system. They even guide charged particles moving through space, which spiral around the fields.

When these magnetic fields run into each other, they can become tangled. When the tension between the crossed lines becomes too great, the lines explosively snap and realign in a process known as magnetic reconnection. The rapid change in a region’s magnetic field creates electric fields, which causes all the attendant charged particles to be flung away at high speeds. Scientists suspect magnetic reconnection is one way that particles — for example, the solar wind, which is the constant stream of charged particles from the Sun — is accelerated to relativistic speeds.

Those speedy particles also create a variety of side-effects near planets.  Magnetic reconnection occurs close to us at points where the Sun’s magnetic field pushes against Earth’s magnetosphere — its protective magnetic environment. When magnetic reconnection occurs on the side of Earth facing away from the Sun, the particles can be hurled into Earth’s upper atmosphere where they spark the auroras. Magnetic reconnection is also thought to be responsible around other planets like Jupiter and Saturn, though in slightly different ways.

NASA’s Magnetospheric Multiscale spacecraft were designed and built to focus on understanding all aspects of magnetic reconnection. Using four identical spacecraft, the mission flies around Earth to catch magnetic reconnection in action. The results of the analyzed data can help scientists understand particle acceleration at relativistic speeds around Earth and across the universe.

Particles can be accelerated by interactions with electromagnetic waves, called wave-particle interactions. When electromagnetic waves collide, their fields can become compressed. Charged particles bouncing back and forth between the waves can gain energy similar to a ball bouncing between two merging walls.

These types of interactions are constantly occurring in near-Earth space and are responsible for accelerating particles to speeds that can damage electronics on spacecraft and satellites in space. NASA missions, like the Van Allen Probes , help scientists understand wave-particle interactions.

Wave-particle interactions are also thought to be responsible for accelerating some cosmic rays that originate outside our solar system. After a supernova explosion, a hot, dense shell of compressed gas called a blast wave is ejected away from the stellar core. Filled with magnetic fields and charged particles, wave-particle interactions in these bubbles can launch high-energy cosmic rays at 99.6% the speed of light. Wave-particle interactions may also be partially responsible for accelerating the solar wind and cosmic rays from the Sun.

Download this and related videos in HD formats from NASA Goddard’s Scientific Visualization Studio

By Mara Johnson-Groh NASA’s Goddard Space Flight Center , Greenbelt, Md.

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Heat Transfer – Conduction, Convection, Radiation

Heat transfer occurs when thermal energy moves from one place to another. Atoms and molecules inherently have kinetic and thermal energy, so all matter participates in heat transfer. There are three main types of heat transfer, plus other processes that move energy from high temperature to low temperature.

What Is Heat Transfer?

Heat transfer is the movement of heat due to a temperature difference between a system and its surroundings. The energy transfer is always from higher temperature to lower temperature, due to the second law of thermodynamics . The units of heat transfer are the joule (J), calorie (cal), and kilocalorie (kcal). The unit for the rate of heat transfer is the kilowatt (KW).

The Three Types of Heat Transfer With Examples

The three types of heat transfer differ according to the nature of the medium that transmits heat:

• Conduction requires contact.
• Convection requires fluid flow.
• Radiation does not require any medium.
• Conduction is heat transfer directly between neighboring atoms or molecules. Usually, it is heat transfer through a solid. For example, the metal handle of a pan on a stove becomes hot due to convection. Touching the hot pan conducts heat to your hand.
• Convection is heat transfer via the movement of a fluid, such as air or water. Heating water on a stove is a good example. The water at the top of the pot becomes hot because water near the heat source rises. Another example is the movement of air around a campfire. Hot air rises, transferring heat upward. Meanwhile, the partial vacuum left by this movement draws in cool outside air that feeds the fire with fresh oxygen.
• Radiation is the emission of electromagnetic radiation. While it occurs through a medium, it does not require one. For example, it’s warm outside on a sunny day because solar radiation crosses space and heats the atmosphere. The burner element of a stove also emits radiation. However, some heat from a burner comes from conduction between the hot element and a metal pan. Most real-life processes involve multiple forms of heat transfer.

Conduction requires that molecules touch each other, making it a slower process than convection or radiation. Atoms and molecules with a lot of energy have more kinetic energy and engage in more collisions with other matter. They are “hot.” When hot matter interacts with cold matter, some energy gets transferred during the collision. This drives conduction. Forms of matter that readily conduct heat are called thermal conductors .

Examples of Conduction

Conduction is a common process in everyday life. For example:

• Holding an ice cube immediately makes your hands feel cold. Meanwhile, the heat transferred from your skin to the ice melts it into liquid water.
• Walking barefoot on a hot road or sunny beach burns your feet because the solid material transmits heat into your foot.
• Iron clothes transfers heat from the iron to the fabric.
• The handle of a coffee cup filled with hot coffee becomes warm or even hot via conduction through the mug material.

Conduction Equation

One equation for conduction calculates heat transfer per unit of time from thermal conductivity, area, thickness of the material, and the temperature difference between two regions:

Q = [K ∙ A ∙ (T hot – T cold )] / d

• Q is heat transfer per unit time
• K is the coefficient of thermal conductivity of the substance
• A is the area of heat transfer
• T hot  is the temperature of the hot region
• T cold  is the temperature of the cold region
• d is the thickness of the body

Convection is the movement of fluid molecules from higher temperature to lower temperature regions. Changing the temperature of a fluid affects its density, producing convection currents. If the volume of a fluid increases, than its density decreases and it becomes buoyant.

Examples of Convection

Convection is a familiar process on Earth, primarily involving air or water. However, it applies to other fluids, such as refrigeration gases and magma. Examples of convection include:

• Boiling water undergoes convection as less dense hot molecules rise through higher density cooler molecules.
• Hot air rises and cooler air sinks and replaces it.
• Convection drives global circulation in the oceans between the equators and poles.
• A convection oven circulates hot air and cooks more evenly than one that only uses heating elements or a gas flame.

Convection Equation

The equation for the rate of convection relates area and the difference between the fluid temperature and surface temperature:

Q = h c  ∙ A ∙ (T s  – T f )

• Q is the heat transfer per unit time
• h c  is the coefficient of convective heat transfer
• T s  is the surface temperature
• T f  is the fluid temperature

Radiation is the release of electromagnetic energy. Another name for thermal radiation is radiant heat. Unlike conduction or convection, radiation requires no medium for heat transfer. So, radiation occurs both within a medium (solid, liquid, gas) or through a vacuum.

Examples of Radiation

There are many examples of radiation:

• A microwave oven emits microwave radiation, which increases the thermal energy in food
• The Sun emits light (including ultraviolet radiation) and heat
• Uranium-238 emits alpha radiation as it decays into thorium-234

Radiation Equation

The Stephan-Boltzmann law describes relationship between the power and temperature of thermal radiation:

P = e ∙ σ ∙ A· (Tr – Tc) 4

• P is the net power of radiation
• A is the area of radiation
• Tr is the radiator temperature
• Tc is the surrounding temperature
• e is emissivity
• σ is Stefan’s constant (σ = 5.67 × 10 -8 Wm -2 K -4 )

More Heat Transfer – Chemical Bonds and Phase Transitions

While conduction, convection, and radiation are the three modes of heat transfer, other processes absorb and release heat. For example, atoms release energy when chemical bonds break and absorb energy in order to form bonds. Releasing energy is an exergonic process, while absorbing energy is an endergonic process. Sometimes the energy is light or sound, but most of the time it’s heat, making these processes exothermic and endothermic .

Phase transitions between the states of matter also involve the absorption or release of energy. A great example of this is evaporative cooling, where the phase transition from a liquid into a vapor absorbs thermal energy from the environment.

• Faghri, Amir; Zhang, Yuwen; Howell, John (2010). Advanced Heat and Mass Transfer . Columbia, MO: Global Digital Press. ISBN 978-0-9842760-0-4.
• Geankoplis, Christie John (2003). Transport Processes and Separation Principles (4th ed.). Prentice Hall. ISBN 0-13-101367-X.
• Peng, Z.; Doroodchi, E.; Moghtaderi, B. (2020). “Heat transfer modelling in Discrete Element Method (DEM)-based simulations of thermal processes: Theory and model development”. Progress in Energy and Combustion Science . 79: 100847. doi: 10.1016/j.pecs.2020.100847
• Welty, James R.; Wicks, Charles E.; Wilson, Robert Elliott (1976). Fundamentals of Momentum, Heat, and Mass Transfer (2nd ed.). New York: Wiley. ISBN 978-0-471-93354-0.

Related Posts

Energy Transfers and Transformations

Energy cannot be created or destroyed, but it can be transferred and transformed. There are a number of different ways energy can be changed, such as when potential energy becomes kinetic energy or when one object moves another object.

Earth Science, Physics

Water Boiling Pot

There are three types of thermal energy transfer: conduction, radiation, and convection. Convection is a cyclical process that only occurs in fluids.

Photograph by Liu Kuanxi

Energy cannot be created or destroyed, meaning that the total amount of energy in the universe has always been and will always be constant. However, this does not mean that energy is immutable; it can change form and even transfer between objects. A common example of energy transfer that we see in everyday life is the transfer of kinetic energy —the energy associated with motion—from one moving object to a stationary object via work. In physics, work is a measure of energy transfer and refers to the force applied by an object over a distance. When a golf club is swung and hits a stationary golf ball, some of the club’s kinetic energy transfers to the ball as the club does “work” on the ball. In an energy transfer such as this one, energy moves from one object to another, but stays in the same form. A kinetic energy transfer is easy to observe and understand, but other important transfers are not as easy to visualize. Thermal energy has to do with the internal energy of a system due to its temperature. When a substance is heated, its temperature rises because the molecules it is composed of move faster and gain thermal energy through heat transfer. Temperature is used as a measurement of the degree of “hotness” or “coldness” of an object, and the term heat is used to refer to thermal energy being transferred from a hotter system to a cooler one. Thermal energy transfers occur in three ways: through conduction , convection , and radiation . When thermal energy is transferred between neighboring molecules that are in contact with one another, this is called conduction . If a metal spoon is placed in a pot of boiling water, even the end not touching the water gets very hot. This happens because metal is an efficient conductor , meaning that heat travels through the material with ease. The vibrations of molecules at the end of the spoon touching the water spread throughout the spoon, until all the molecules are vibrating faster (i.e., the whole spoon gets hot). Some materials, such as wood and plastic, are not good conductors —heat does not easily travel through these materials—and are instead known as insulators . Convection only occurs in fluids, such as liquids and gases. When water is boiled on a stove, the water molecules at the bottom of the pot are closest to the heat source and gain thermal energy first. They begin to move faster and spread out, creating a lower density of molecules at the bottom of the pot. These molecules then rise to the top of the pot and are replaced at the bottom by cooler, denser water. The process repeats, creating a current of molecules sinking, heating up, rising, cooling down, and sinking again. The third type of heat transfer— radiation —is critical to life on Earth and is important for heating bodies of water. With radiation , a heat source does not have to touch the object being heated; radiation can transfer heat even through the vacuum of space. Nearly all thermal energy on Earth originates from the sun and radiates to the surface of our planet, traveling in the form of electromagnetic waves, such as visible light. Materials on Earth then absorb these waves to be used for energy or reflect them back into space. In an energy transformation , energy changes form. A ball sitting at the top of a hill has gravitational potential energy , which is an object’s potential to do work due to its position in a gravitational field. Generally speaking, the higher on the hill this ball is, the more gravitational potential energy it has. When a force pushes it down the hill, that potential energy transforms into kinetic energy . The ball continues losing potential energy and gaining kinetic energy until it reaches the bottom of the hill. In a frictionless universe, the ball would continue rolling forever upon reaching the bottom, since it would have only kinetic energy . On Earth, however, the ball stops at the bottom of the hill due to the kinetic energy being transformed into heat by the opposing force of friction. Just as with energy transfers , energy is conserved in transformations. In nature, energy transfers and transformations happen constantly, such as in a coastal dune environment. When thermal energy radiates from the sun, it heats both the land and ocean, but water has a specific high heat capacity, so it heats up slower than land. This temperature difference creates a convection current, which then manifests as wind. This wind possesses kinetic energy , which it can transfer to grains of sand on the beach by carrying them a short distance. If the moving sand hits an obstacle, it stops due to the friction created by the contact and its kinetic energy is then transformed into thermal energy , or heat. Once enough sand builds up over time, these collisions can create sand dunes, and possibly even an entire dune field. These newly formed sand dunes provide a unique environment for plants and animals. A plant may grow in these dunes by using light energy radiated from the sun to transform water and carbon dioxide into chemical energy , which is stored in sugar. When an animal eats the plant, it uses the energy stored in that sugar to heat its body and move around, transforming the chemical energy into kinetic and thermal energy . Though it may not always be obvious, energy transfers and transformations constantly happen all around us and are what enable life as we know it to exist.

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10.13: Thermal Energy Transfer in the Atmosphere

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Can you see energy moving?

Energy constantly moves all around us! Anything that moves has kinetic energy, and you can see light energy and feel thermal energy in a chemical reaction or a campfire. Moving energy in the atmosphere sometimes makes itself visible in the way it moves air. In this photo, differences in temperature are causing air to move—in fantastic ways!

How Energy Moves Through the Atmosphere

Energy travels through space or material. Thermal energy is transferred in three ways: radiation , conduction , and convection .

Radiation is the transfer of energy by waves. Energy can travel as electromagnetic waves through air or empty space. The Sun's energy travels through space by radiation. After sunlight heats the planet's surface, some heat radiates back into the atmosphere.

In conduction , thermal energy is transferred from molecule to molecule by contact. Warmer molecules vibrate faster than cooler ones. They bump into the cooler molecules. When they do, they transfer some of their energy. Conduction happens mainly in the lower atmosphere. Can you explain why?

Convection is the transfer of thermal energy by a current. Convection happens in a liquid or a gas. Air near the ground is warmed by heat radiating from Earth's surface. The warm air is less dense, so it rises. As it rises, it cools. The cool air is dense, so it sinks to the surface. This creates a convection current ( Figure below). Convection is the most important way that heat travels in the atmosphere.

Convection currents are the main way that heat moves through the atmosphere. Why does warm air rise?

• In conduction, heat moves from areas of more heat to areas of less heat. The substances must be in direct contact.
• In convection, materials move depending on their heat relative to nearby materials.
• In radiation, energy moves by waves.
• What is moving in conduction?
• What is moving in convection?
• What is radiation?

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Science Struck

Conduction, Convection, and Radiation – 3 Modes of Heat Transfer

As the name suggests, heat transfer is the travel of heat or thermal energy from one object or entity to another. This transfer takes place in three ways - conduction, convection, and radiation. This ScienceStruck post discusses the methods of heat transfer and its applications in detail.

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As the name suggests, heat transfer is the travel of heat or thermal energy from one object or entity to another. This transfer takes place in three ways – conduction, convection, and radiation. This ScienceStruck post discusses the methods of heat transfer and its applications in detail.

What is Heat?

Heat can be defined as the process of transfer of thermal energy from or to an object. And as it is a process, objects or bodies do not contain heat but thermal energy.

Why do you burn your hand when you touch a hot pan placed on a burner? How does the cooling system of an automobile engine work? Why do you feel warm when you stand in the sun for a while? The answers to all these questions lie in the concept of heat transfer and the three modes of heat transfer. But before we discuss heat transfer, let us take a brief look at the branch of physics known as ‘thermodynamics’.

Thermodynamics is the study of relationship between heat and other forms of energy. Thermal equilibrium occurs when macroscopic changes in the system cease to occur with time. If you put ice in a glass of water, the water being at a higher temperature will transfer heat energy to the ice cube. This will continue till the ice cube melts into water which is at the same temperature as the water in the glass. Thus, a state of thermal equilibrium is reached. Thermodynamics is applicable to systems that are in thermal equilibrium. The phenomenon of heat transfer deals with systems that are not in thermal equilibrium.

Heat transfer analyzes the rate of transfer of heat. Temperature difference or temperature gradient between the systems in consideration is a prerequisite for heat transfer. Temperature gradient is defined as the temperature difference per unit length or the rate of change of temperature. Heat transfer in any direction depends on the magnitude of temperature gradient in that direction. Heat transfer is based on the following fundamental laws

• Law of conservation of mass
• Newton’s laws of motion
• Laws of Thermodynamics

Modes of Heat Transfer

● Conduction can occur in solids and fluids. It is the transfer of heat across a medium or objects which are in physical contact.

● A hot pan placed on a burner burns your hand if you touch it because conduction of heat takes place between the heated pan and your hand. Consider a gas that is in steady state (i.e., state variables like pressure, density, temperature are constant). Conduction can be imagined as the energy transfer from more energetic to less energetic particles (here, molecules) due to interaction between them. This energy is related to translation motion, as well as internal rotational and vibration motions of the molecules.

● This can also be termed as ‘diffusion’ due to the presence of temperature gradient and transfer of energy from molecules at a higher temperature and concentration to those at a lower temperature and concentration.

● An example of conduction of heat is a thermocouple. It is a temperature measuring device made up of two dissimilar metals joined together to form two junctions. The temperature of the hot junction is measured with respect to a reference cold junction. An electromotive force (emf) is generated at the two junctions due to the presence of a temperature gradient ,which is measured.

● As mentioned earlier, heat transfer analyzes the rate of exchange of heat.. The rate equation for heat conduction is known as ‘Fourier’s Law’. For a one-dimensional plane wall it is given by:

q” x = -k dT/dx

where, q” x = heat transfer rate in x-direction per unit area perpendicular to the direction of transfer Proportionality constant k is a transport property known as thermal conductivity (W/m K) and is characteristic of the material. dT = temperature difference between two faces of the wall of thickness dx Minus sign indicates that the heat transfer is in the direction of decreasing temperature.

● Convection is the transfer of heat from a fluid to a solid surface or within a fluid.

● It is a combination of bulk fluid motion (advection) and random molecular motion (diffusion)

● Convection currents is the best example of this mode of heat transfer. When a cast iron skillet containing water is placed on a burner, convection currents are formed in the water. Warmer, less dense molecules move up while the colder ones sink down. The convection currents set up in a room with a radiator are shown in the adjoining figure. The radiator draws the cool air at the bottom, which is warmed over its fins. The hot air is discharged at the top keeping the room warm.

● Convection is of two types:

• Natural Convection: It occurs due to density difference caused by temperature gradient present between the fluid and the surface.
• Forced Convection: External means like fans, pumps, compressors are used to set the fluid in motion.

● The rate equation for convection is known as Newton’s law of cooling.

q” = h (T s – T ∞ )

where, q” = convective heat flux (W/m 2 ) h = convection heat transfer coefficient.

● Matter that is at finite temperature emits energy in space in the form of electromagnetic waves. This is known as ‘radiation’.

● Radiation from the surface of the Sun is a well-known example. People can sit around a campfire and warm their hands over it because of the heat radiated from the fire.

● Presence of a medium is immaterial for the propagation of these electromagnetic waves. In fact, radiation occurs most effectively in a vacuum.

● It occurs in solids, liquids, and gases.

● Emissive power “E” is defined as the rate at which thermal energy is released per unit area by the matter of a surface. The upper limit to this emissive power is given by Stefan-Boltzmann Law:

E b = σ T s 4

where, T s = absolute temperature K of the surface σ = 5.57 X 10 -8 W/m 2 K 4 = Stefan-Boltzmann constant.

Heat Transfer Co-efficient

● Convective heat transfer co-efficient ‘h’ is the quantity of heat transferred in unit time through unit area at a temperature difference of one degree between the surface and the surroundings. Unit = W/ m 2 K

● The term 1/h is called thermal resistance.

● Overall heat transfer coefficient: Heat flow rate through a composite wall and considering all modes of heat transfer (i.e. by conduction, convection, and radiation) can be expressed as:

Q = U × A (T i – T o ) = (T i – T o )/ ΣR

where T i , T o are temperatures at inner and outer sides of a composite wall, respectively A = Area of heat flow normal to heat flow direction (m 2 ) U = Overall heat transfer coefficient ΣR= 1/UA = Overall or combined thermal resistance of the wall.

Applications

● Cooling of the human body, home heating, household energy use, involve all three modes of heat transfer.

● Applications of convection include the cooling system of an automobile engine, blood flow rate in peripheral vessels, etc.

● Thermocouple is a device which uses conduction as a mode of heat transfer.

● Black body radiators, Greenhouse effect, are some examples of radiation.

● A vacuum flask is designed by taking heat transfer calculations into consideration

● Heat engines, refrigerators, and heat pumps.

Thus, in practice, heat transfer is usually a combination of two or all three modes. This was a brief description of these modes.

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Science News Explores

Explainer: how heat moves.

Here are the three processes by which energy can be transferred from one place to another

Heat is being transferred from the hot end of this rod to the cold end via conduction, but the hot end of the rod is also radiating heat via that orange glow.

Dvoinik/iStockphoto

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By Sid Perkins

September 30, 2016 at 6:15 am

Throughout the universe, it’s natural for energy to flow from one place to another. And unless people interfere, thermal energy — or heat — naturally flows in one direction only: from hot toward cold.

Heat moves naturally by any of three means. The processes are known as conduction, convection and radiation. Sometimes more than one may occur at the same time.

First, a little background. All matter is made from atoms — either single ones or those bonded in groups known as molecules. These atoms and molecules are always in motion. If they have the same mass, hot atoms and molecules move, on average, faster than cold ones. Even if atoms are locked in a solid, they still vibrate back and forth around some average position.

In a liquid, atoms and molecules are free to flow from place to place. Within a gas, they are even more free to move and will completely spread out within the volume in which they are trapped.

Some of the most easily understood examples of heat flow occur in your kitchen.  

Put a pan on a stovetop and turn on the heat. The metal sitting over the burner will be the first part of the pan to get hot. Atoms in the pan’s bottom will start to vibrate faster as they warm. They also vibrate farther back and forth from their average position. As they bump into their neighbors, they share with that neighbor some of their energy. (Think of this as a very tiny version of a cue ball slamming into other balls during a game of billiards. The target balls, previously sitting still, gain some of the cue ball’s energy and move.)

As a result of collisions with their warmer neighbors, atoms start moving faster. In other words, they are now warming. These atoms, in turn, transfer some of their increased energy to neighbors even farther from the original source of heat. This conduction of heat through a solid metal is how the handle of a pan gets hot even though it may be nowhere near the source of heat.

Convection occurs when a material is free to move, such as a liquid or a gas. Again, consider a pan on the stove. Put water in the pan, then turn on the heat. As the pan gets hot, some of that heat transfers to the molecules of water sitting on the bottom of the pan via conduction. That speeds up the motion of those water molecules — they are warming.

As the water warms, it now begins to expand. That makes it less dense. It rises above denser water, carrying  away heat from the bottom of the pan. Cooler water flows down to take its place next to the hot bottom of the pan. As this water warms, it expands and rises, ferrying its newly-gained energy with it. In short order, a circular flow of rising warm water and falling cooler water sets up. This circular pattern of heat transfer is known as convection .

It’s also what largely warms food in an oven. Air that’s warmed by a heating element or gas flames at the top or bottom of the oven carries that heat to the central zone where the food sits.

Air that’s warmed at Earth’s surface expands and rises just like the water in the pan on the stove. Large birds such as frigate birds (and human flyers riding engineless gliders) often ride these thermals — rising blobs of air — to gain altitude without using any energy of their own. In the ocean, convection caused by heating and cooling helps to drive ocean currents. These currents move water around the globe.

The third type of energy transfer is in some ways the most unusual. It can move through materials — or in the absence of them. This is radiation.

Consider visible light, a form of radiation. It passes through some types of glass and plastic. X-rays, another form of radiation, readily pass through flesh but are largely blocked by bone. Radio waves pass through the walls of your home to reach the antenna on your stereo. Infrared radiation, or heat, passes through the air from fireplaces and light bulbs. But unlike conduction and convection, radiation doesn’t require a material to transfer its energy. Light, X-rays, infrared waves and radio waves all travel to Earth from the far reaches of the universe. Those forms of radiation will pass through plenty of empty space along the way.

X-rays, visible light, infrared radiation, radio waves are all different forms of electromagnetic radiation . Each type of radiation falls into a particular band of wavelengths. Those types differ in the amount of energy they have. In general, the longer the wavelength, the lower the frequency of a particular type of radiation and the less energy it will carry.

To complicate things, it’s important to note that more than one form of heat transfer may occur at the same time. A stove’s burner not only heats a pan but also the nearby air and makes it less dense. That carries warmth upward via convection. But the burner also radiates heat as infrared waves, making things nearby warm up. And if you’re using a cast-iron skillet to cook a tasty meal, be sure to grab the handle with a potholder: It’s gonna be hot, thanks to conduction!

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NOTIFICATIONS

Waves as energy transfer.

• + Create new collection

‘Wave’ is a common term for a number of different ways in which energy is transferred:

• In electromagnetic waves, energy is transferred through vibrations of electric and magnetic fields.
• In sound waves, energy is transferred through vibration of air particles or particles of a solid through which the sound travels.
• In water waves, energy is transferred through the vibration of the water particles.

Waves transfer energy but not mass

When we watch surf waves coming into shore, it’s easy to think that individual water particles are moving towards us, but that’s not actually the case. The particles involved in waves move back and forth perpendicularly to the way the wave is going, but don’t move significantly in the direction of the wave. The particles ‘take part’ in the wave by bumping into one another and transferring energy. This is why energy can be transferred, even though the average position of the particles doesn’t change.

How does this work? It can help to think of a buoy bobbing in the ocean. The buoy is moved up and down by the waves that pass by it, but doesn’t move directionally across the water.

You could also think about a Mexican wave at a sports match. The wave moves around the arena, but the audience members don’t move around with it – they only stand up and sit down (a perpendicular movement to the wave direction).

Particles in a water wave exchange kinetic energy for potential energy

When particles in water become part of a wave, they start to move up or down. This means that kinetic energy (energy of movement) has been transferred to them. As the particles move further away from their normal position (up towards the wave crest or down towards the trough), they slow down. This means that some of their kinetic energy has been converted into potential energy – the energy of particles in a wave oscillates between kinetic and potential energy.

Thinking about potential energy can help us understand why tsunamis can be so damaging. When a tsunami approaches the shore, it shoals (becomes much higher), so the water particles are displaced further from equilibrium. They acquire a lot of potential energy, and this is released when the wave interacts with land.

Measuring the energy in a wave

Why do some waves have more energy than others? A wave’s frequency and wavelength are both indicators of its energy, but this differs for different types for waves.

For water waves, those with a high speed and long wavelength (like a tsunami) have the most energy. For electromagnetic waves, speed is constant, so waves with a high frequency and a short wavelength (like X-rays) are the most energetic.

For all waves, a greater amplitude means more energy.

In the electromagnetic spectrum interactive you can click on various wavelengths to learn more about the waves that make up the spectrum.

Harnessing wave energy

Scientists in New Zealand and elsewhere are looking at how to turn the energy of water waves into electricity. The oceans around New Zealand are promising places to generate wave power because we have large waves and strong currents. Generating wave power would involve an underwater device (like a paddle, for example) that would move in response to waves and drive a turbine that would produce electricity.

The idea of wave power is appealing because waves are a sustainable resource – they can’t be used up (unlike other resources, like coal, that are used for making electricity in New Zealand). However, they are quite inefficient – they need a lot of coastal space to generate useful quantities of energy. Using mathematical modelling and physical model building, Kiwi scientists are investigating how to harness wave power, but it will be some time before we’re using electricity from wave power in our homes.

Between 2007 and 2011 the Energy Efficiency and Conservation Authority (EECA) administered the Marine Energy Deployment Fund which funded marine energy projects. After a review none of the projects were selected to progress further and, as of 2016, EECA believe that the abundance of cheaper renewable energy resources in New Zealand makes it unlikely marine energy will contribute to the national grid in the foreseeable future. Investigations into harnessing the energy of ocean waves continues in other countries.

From 2017 to 2019, as part of a Sustainable Seas Innovation Fund project, NIWA investigated whether generating electricity from the strong tidal currents within the Cook Strait would be viable for Aotearoa. To find out more, see Energy from tidal currents – Kick-starting a new marine industry with huge potential from NIWA's website.

Activity ideas

Use a Mexican wave to demonstrate how waves transfer energy and to help your students visualise the wave behaviours of reflection, constructive interference and shoaling.

Use an interactive or paper-based Venn diagram to illustrate the key similarities and differences between tsunami waves and surf waves .

More on waves

Explore more about waves, such as sound and energy by browsing the resources under our waves concept .

Useful links

In 2021 NIWA ran a webinar: A step closer to a future powered by tidal current energy , in which the results of the Energy from tidal currents project are presented.This project investigated the viability of generation electricity from the strong tidal currents within Cook Strait.

Find out more about using waves as an energy source in this Wikipedia article .

Watch this 2011 video from NIWA: Current conversion – tidal and wave energy in New Zealand .

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What is heat? What could go wrong on DS1 if it gets too cold? What could go wrong on DS1 if there's too much heat?

Will DS1 get heated directly by the Sun? Does heat travel differently in space than it does on Earth? What role does the Sun play in space missions like DS1's?

What other forms of energy does a spacecraft releases into space? What makes EM radiation? Where does energy come from and go? What happens to the heat once it is released into space?

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May 31, 2019

Three ways to travel at (nearly) the speed of light

by Mara Johnson-Groh, NASA's Goddard Space Flight Center

One hundred years ago today, on May 29, 1919, measurements of a solar eclipse offered verification for Einstein's theory of general relativity. Even before that, Einstein had developed the theory of special relativity, which revolutionized the way we understand light. To this day, it provides guidance on understanding how particles move through space—a key area of research to keep spacecraft and astronauts safe from radiation.

The theory of special relativity showed that particles of light, photons, travel through a vacuum at a constant pace of 670,616,629 miles per hour—a speed that's immensely difficult to achieve and impossible to surpass in that environment. Yet all across space, from black holes to our near-Earth environment, particles are, in fact, being accelerated to incredible speeds, some even reaching 99.9% the speed of light.

One of NASA's jobs is to better understand how these particles are accelerated. Studying these superfast, or relativistic, particles can ultimately help protect missions exploring the solar system, traveling to the Moon, and they can teach us more about our galactic neighborhood: A well-aimed near-light-speed particle can trip onboard electronics and too many at once could have negative radiation effects on space-faring astronauts as they travel to the Moon—or beyond.

Here are three ways that acceleration happens.

1. Electromagnetic Fields

Most of the processes that accelerate particles to relativistic speeds work with electromagnetic fields—the same force that keeps magnets on your fridge. The two components, electric and magnetic fields, like two sides of the same coin, work together to whisk particles at relativistic speeds throughout the universe.

In essence, electromagnetic fields accelerate charged particles because the particles feel a force in an electromagnetic field that pushes them along, similar to how gravity pulls at objects with mass. In the right conditions, electromagnetic fields can accelerate particles at near-light-speed.

On Earth, electric fields are often specifically harnessed on smaller scales to speed up particles in laboratories. Particle accelerators, like the Large Hadron Collider and Fermilab, use pulsed electromagnetic fields to accelerate charged particles up to 99.99999896% the speed of light. At these speeds, the particles can be smashed together to produce collisions with immense amounts of energy. This allows scientists to look for elementary particles and understand what the universe was like in the very first fractions of a second after the Big Bang.

2. Magnetic Explosions

Magnetic fields are everywhere in space, encircling Earth and spanning the solar system. They even guide charged particles moving through space, which spiral around the fields.

When these magnetic fields run into each other, they can become tangled. When the tension between the crossed lines becomes too great, the lines explosively snap and realign in a process known as magnetic reconnection. The rapid change in a region's magnetic field creates electric fields, which causes all the attendant charged particles to be flung away at high speeds. Scientists suspect magnetic reconnection is one way that particles—for example, the solar wind, which is the constant stream of charged particles from the sun—is accelerated to relativistic speeds.

Those speedy particles also create a variety of side-effects near planets. Magnetic reconnection occurs close to us at points where the sun's magnetic field pushes against Earth's magnetosphere—its protective magnetic environment. When magnetic reconnection occurs on the side of Earth facing away from the sun, the particles can be hurled into Earth's upper atmosphere where they spark the auroras. Magnetic reconnection is also thought to be responsible around other planets like Jupiter and Saturn, though in slightly different ways.

NASA's Magnetospheric Multiscale spacecraft were designed and built to focus on understanding all aspects of magnetic reconnection. Using four identical spacecraft, the mission flies around Earth to catch magnetic reconnection in action. The results of the analyzed data can help scientists understand particle acceleration at relativistic speeds around Earth and across the universe.

3. Wave-Particle Interactions

Particles can be accelerated by interactions with electromagnetic waves, called wave-particle interactions. When electromagnetic waves collide, their fields can become compressed. Charged particles bouncing back and forth between the waves can gain energy similar to a ball bouncing between two merging walls.

These types of interactions are constantly occurring in near-Earth space and are responsible for accelerating particles to speeds that can damage electronics on spacecraft and satellites in space. NASA missions, like the Van Allen Probes, help scientists understand wave-particle interactions.

Wave-particle interactions are also thought to be responsible for accelerating some cosmic rays that originate outside our solar system. After a supernova explosion, a hot, dense shell of compressed gas called a blast wave is ejected away from the stellar core. Filled with magnetic fields and charged particles , wave-particle interactions in these bubbles can launch high-energy cosmic rays at 99.6% the speed of light. Wave-particle interactions may also be partially responsible for accelerating the solar wind and cosmic rays from the sun.

Provided by NASA's Goddard Space Flight Center

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Physics library

Course: physics library   >   unit 10.

• Specific heat and latent heat of fusion and vaporization

Thermal conduction, convection, and radiation

• Thermal conduction
• Thermal conductivity of metal and wood
• Intuition behind formula for thermal conductivity
• What is thermal conductivity?

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Video transcript

An official website of the United States government

Official websites use .gov A .gov website belongs to an official government organization in the United States.

• JetStream home
• Layers of the Atmosphere
• Air Pressure
• The Transfer of Heat Energy
• Energy Balance
• Hydrologic Cycle
• Precipitation
• Layers of the Ocean
• Ocean Circulations
• The Sea Breeze
• The Marine Layer
• Rip Current Safety
• Global Atmospheric Circulations
• The Jet Stream
• Climate vs. Weather
• Climate Zones
• How clouds form
• The Core Four
• The Basic Ten
• Cloud Chart
• Color of Clouds
• Parcel Theory
• Stability-Instability
• Radiosondes
• Skew-T Log-P Diagrams
• Skew-T Plots
• Skew-T Examples
• Pressure vs. Elevation
• Longwaves and Shortwaves
• Basic Wave Patterns
• Common Features
• Thickness Charts
• Weather Models
• Surface Weather Plots
• Norwegian Cyclone Model
• Types of Weather Phenomena
• Electromagnetic waves
• The Atmospheric Window
• Weather Satellites
• How radar works
• Volume Coverage Patterns (VCP)
• Radar Images: Reflectivity
• Radar Images: Velocity
• Radar Images: Precipitation
• Inter-Tropical Convergence Zone
• Classification
• NHC Forecasts
• Hazards & Safety
• Damage Potential
• ENSO Pacific Impacts
• ENSO Weather Impacts
• Ingredients for a Thunderstorm
• Life Cycle of a Thunderstorm
• Types of Thunderstorms
• Hazard: Hail
• Hazard: Damaging wind
• Hazard: Tornadoes
• Hazard: Flash Floods
• Staying Ahead of the Storms
• How Lightning is Created
• The Positive and Negative Side of Lightning
• The Sound of Thunder
• Lightning Safety
• Frequently Asked Questions
• Types of Derechos
• Where and When
• Notable Derechos
• Keeping Yourself Safe
• Historical Context
• Causes: Earthquakes
• Causes: Landslides
• Causes: Volcanoes
• Causes: Weather
• Propagation
• Detection, Warning, and Forecasting
• Preparedness and Mitigation: Communities
• Preparedness and Mitigation: Individuals (You!)
• Select NOAA Tsunami Resources
• Weather Forecast Offices
• River Forecast Centers
• Center Weather Service Units
• Regional Offices
• National Centers for Environmental Prediction
• NOAA Weather Radio
• NWS Careers: Educational Requirements
• Weather Glossary
• Weather Acronyms
• Learning Lessons
• The Ionosphere
• What-a-cycle

It is not the heat you feel but ultraviolet radiation from the sun that causes sunburns that lead to skin cancer. The warmth of the sun does not lead to a sunburn.

From the American Academy of Dermatology, sunlight consists of two types of harmful rays that reach the earth - ultraviolet A (UVA) rays and ultraviolet B (UVB) rays. Overexposure to either can lead to skin cancer. In addition to causing skin cancer, here's what each of these rays do:

• UVA rays can prematurely age your skin, causing wrinkles and age spots, and can pass through window glass.
• UVB rays are the primary cause of sunburn and are blocked by window glass.

There is no safe way to tan. This includes radiation from artificial sources, such as tanning beds and sun lamps. Every time you tan, you damage your skin. As this damage builds, you speed up the aging of your skin and increase your risk for all types of skin cancer.

Even on cloudy days, ultraviolet radiation can pass through clouds and cause a sunburn if you remain outdoors long enough.

The Sun generates energy, which is transferred through space to the Earth's atmosphere and surface. Some of this energy warms the atmosphere and surface as heat. There are three ways energy is transferred into and through the atmosphere:

If you have stood in front of a fireplace or near a campfire, you have felt the heat transfer known as radiation. The side of your body nearest the fire warms while your other side remains unaffected by the heat. Although you are surrounded by air, the air has nothing to do with this transfer of heat. Heat lamps that keep food warm work in the same way. Radiation is the transfer of heat energy through space by electromagnetic radiation.

Electromagnetic radiation is made of waves of different frequencies. The frequency is the number of instances that a repeated event occurs over a set time. In other words, the frequency of electromagnetic radiation is the number of electromagnetic waves moving past a point each second. Most wavelengths of electromagnetic radiation are invisible. However, much of the electromagnetic radiation that reaches the Earth from the Sun is visible light.

Our brains interpret some of these frequencies as colors, including red, orange, yellow, green, blue, indigo, and violet. When the eye views all these different frequencies at the same time, it is interpreted as white. Infrared and ultraviolet are two of the waves we can't see. Infrared had a lower frequency than red, and ultraviolet has a higher frequency than violet [ more on electromagnetic radiation ]. It is infrared radiation that produces the warm feeling on our bodies.

Most of the solar radiation is absorbed by the atmosphere, and much of what reaches the Earth's surface is radiated back into the atmosphere to become heat energy. Dark colored objects, such as asphalt, absorb radiant energy faster than light colored objects. However, they also radiate their energy faster than lighter colored objects. (The variations in how Earth's surface absorbs heat from the Sun is called differential heating.)

Learning Lesson:   Melts in your bag, not in your hand

Conduction is the transfer of heat energy from one substance to another or within a substance. Have you ever left a metal spoon in a pot of soup being heated on a stove? After a short time, the handle of the spoon will become hot.

Conduction is a very effective method of heat transfer in metals. However, air conducts heat poorly.

Convection is the transfer of heat energy in a fluid. In the kitchen, this type of heating is most commonly seen as the circulation that develops in a boiling liquid.

Air in the atmosphere acts as a fluid. The Sun's radiation strikes the Earth's surface, thus warming it. As the surface's temperature rises due to conduction, heat energy is released into the atmosphere, forming a bubble of air that is warmer than the surrounding air. This bubble of air rises into the atmosphere. As it rises, the bubble cools, with its heat moving into the surrounding atmosphere.

As the hot air mass rises, it is replaced by the surrounding cooler, more dense air, which we feel as wind. These movements of air masses can be small in a certain region, such as local cumulus clouds, or large cycles in the troposphere, covering large sections of the Earth. The large cycles are called convection currents and are responsible for many weather patterns in the troposphere.

How is heat transferred? Conduction - Convection - Radiation

What is Heat?

All matter is made up of molecules and atoms. These atoms are always in different types of motion (translation, rotational, vibrational). The motion of atoms and molecules creates heat or thermal energy. All matter has this thermal energy. The more motion the atoms or molecules have the more heat or thermal energy they will have.

This is an animation made from a short molecular dynamics simulation of water. The green lines represent hydrogen bonds between oxygen and hydrogen. Notice the tight structure of water

Hydrogen bonds are much weaker than covalent bonds. However, when a large number of hydrogen bonds act in unison they will make a strong contributory effect. This is the case in water shown here.

What is temperature?

From the video above that shows movement of atoms and molecules it can be seen that some move faster than others. Temperature is an average value of energy for all the atoms and molecules in a given system. Temperature is independent of how much matter there is in the system. It is simply an average of the energy in the system.

How is heat transferred?

Heat can travel from one place to another in three ways: Conduction, Convection and Radiation. Both conduction and convection require matter to transfer heat. 

If there is a temperature difference between two systems heat will always find a way to transfer from the higher to lower system.

CONDUCTION- -

Conduction is the transfer of heat between substances that are in direct contact with each other. The better the conductor, the more rapidly heat will be transferred. Metal is a good conduction of heat. Conduction occurs when a substance is heated, particles will gain more energy, and vibrate more. These molecules then bump into nearby particles and transfer some of their energy to them. This then continues and passes the energy from the hot end down to the colder end of the substance.

CONVECTION --

Thermal energy is transferred from hot places to cold places by convection. Convection occurs when warmer areas of a liquid or gas rise to cooler areas in the liquid or gas. Cooler liquid or gas then takes the place of the warmer areas which have risen higher. This results in a continous circulation pattern. Water boiling in a pan is a good example of these convection currents. Another good example of convection is in the atmosphere. The earth's surface is warmed by the sun, the warm air rises and cool air moves in.

RADIATION- -

Radiation is a method of heat transfer that does not rely upon any contact between the heat source and the heated object as is the case with conduction and convection. Heat can be transmitted through empty space by thermal radiation often called  infrared radiation . This is a type  electromagnetic radiation  . No mass is exchanged and no medium is required in the process of radiation. Examples of radiation is the heat from the sun, or heat released from the filament of a light bulb.

SOURCES AND READERS CHOICES --

Heat and Temperature from Cool Cosmo -- NASA

Here is a good applet to show  motion in molecules  -- you can control the temperature and see in this applet how to movements of the molecules change.

Important Temperatures in Cooking and Culinary Skills

What were the 100 Greatest Inventions?

See the list--Greatest Inventions of all Time

Related Activies

• Mass Volume Density
• Molecular Modeling-- An NGSS Activity
• Water and Ice Module
• States of Matter
• How do molecules of solids, liquids and gas behave differently?
• Science of Fluids
• Buoyancy and Archimedes Principle
• Speed Velocity and Acceleration
• Gifted and Talented STEM
• EDinformatics Science Challenge
• How does a battery work?

What are three ways heat can travel?

Conduction (through e.g. solid materials like metals that allow heat through - like a saucepan base) It is transformed into another object by touch

Convection - in liquids and gases. Hot substances expand and so are less dense than cold substances. These less dense liquids and gases rise and cool ones fall forming a current. as an example, convector heaters in your home, the Gulf Stream that brings warm water from the Caribbean to Europe .

Radiation - the method by which energy is transferred through a vacuum e.g. in the infra red heat energy from the sun as it travels across the vacuum of space.

radiation, convection and conduction.

Three ways heat can travel is Radiation,Convection ,Conduction.

1- Radiation:-

It doesn't require any medium. The best example of radiation is heat travelling from Sun to Earth.

2- Convection:-

Convection requires a liquid medium. It's best example is the heating of water in a beaker.

3- Conduction:-

It requires a solid or material medium. The heat is transferred by the vibration of molecules for example the heating of a metal rod after putting candle on the other side.

Conduction, Convection and Radiation

For example, for conduction you can use a boiling pot of water.

For convection you can use a blender.

For radiation you can use the sun or another one is your cell phone.

• Convection, warm water or air or any other gas or fluid, rises cold falls and a heat source creates the system. (Ice water in a glass on a warm day)
• Conduction, cold object touches hot (My hand and my frying pan last night)
• Radiation is when you can feel the heat coming off something with out touching it (the sun is a good example)

Conduction, convection, radiation

Convection, radiation, conduction

Conduction, convection, radiation.

Anonymous ∙

Conduction Convestion Radiation

Add your answer:

What is the three ways heat can travel?

radiant, conductive, and convection.

Heat can travel by?

Heat can travel in 3 ways by conduction in solids, convection of fluids (liquids or gases), and radiation.

What are the three ways that heat can move from one substance to another?

Heat moves in three ways: Radiation, conduction, and convection.

Which way heat travel?

There are three modes for heat travel:conductionconvectionradiation

What are the three major ways of heat transfer?

heat can be transfered in three ways... 1. conduction 2.convection 3. radiation

What are ways energy can travel?

What are three ways energy can travel

Heat can be transferred by what?

There are three ways in which heat can be transferred from one surface to another. These three ways are conduction, convection and radiation.

Describe three ways heat can be transferred in a boiler?

what are the 3 ways to transferred heat into a boiler

How many ways can heat transfer?

Three. Conduction, convection and radiation.There are three ways heat can be transferred. Two ways include convection and radiation. The third way is conduction.

What are three ways that heat transfers from hot objects to cool objects?

The three ways are: radiation, conduction, and convection.

What are the three ways heat energy is transfered?

ConductionConvectionRadiation

What were the three ways people could travel in the 1800s?

Horse, wagon, and walking were the three ways people travels in the 1800s.

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The Sun's Energy: An Essential Part of the Earth System

Solar radiation, or energy produced by the Sun, is the primary energy source for most processes in the Earth system and drives Earth’s energy budget .

The Sun is the primary energy source for our planet’s energy budget and contributes to processes throughout Earth.

UCAR/The COMET Program

Energy from the Sun is studied as part of heliophysics, which relates to the Sun’s physics and the Sun’s connection with the solar system.

How Does Energy from the Sun Reach Earth?

It takes solar energy an average of 8 ⅓ minutes to reach Earth from the Sun. This energy travels about 149 million km (93 million miles) through space to reach the top of Earth’s atmosphere. Waves of solar energy radiate, or spread out, from the Sun and travel at the speed of light through the vacuum of space as electromagnetic radiation. The majority of the Sun’s radiation reaching Earth is in the form of visible light we can see and invisible infrared energy that we can’t see. A smaller portion of sunlight is made up of ultraviolet radiation, which is also invisible to our eyes.

Most of the Sun’s energy reaching Earth includes visible light and infrared radiation but some is in the form of plasma and solar wind particles. 

Other forms of radiation from the Sun can reach Earth as part of the solar wind , but in smaller quantities and with longer travel times. The solar wind contains plasma and particles and can also include gamma rays and x-rays resulting from solar storms or other bursts of energy from the Sun’s surface.

The Energy We Receive Depends on Distance From the Sun

The Sun’s energy we receive is electromagnetic radiation that travels through space or a medium in the form of waves or particles. The visible light we see from the Sun is similar to the visible light from a light bulb, but the Sun provides much more of it. The energy released from the Sun is mind-bogglingly large, equal to about 36 octillion (3.6 x 10 28 ) or 36 thousand trillion trillion lumens, where a lumen is a measure of the total amount of visible light. This brightness (or intensity) falls off with distance from the source by a factor of 1/d 2 , where d 2 is the square of the distance. From the surface of Mercury, depending on the planet's position in its orbit, the Sun would appear from seven to eleven times brighter as it does when viewed from Earth. By the time the Sun's energy reaches Earth's surface, it has an average brightness of about 127,000 lumens per square meter, or about 127 light bulbs if we consider that a typical light bulb produces about 650-1600 lumens of visible light.

The Sun is 93 million miles from Earth, yet it still provides us with all of the energy needed to sustain life.

The Sun’s Energy is Important to Life on Earth

Energy from the Sun makes it possible for life to exist on Earth. It is responsible for photosynthesis in plants, vision in animals, and many other natural processes, such as the movements of air and water that create weather. Most plants need at least some sunlight to grow, so without light, there would be no plants, and without plants, there would not be oxygen for us to breathe. Infrared radiation from the Sun is responsible for heating the Earth’s atmosphere and surface. Without energy from the Sun, Earth would freeze. There would be no winds, ocean currents, or clouds to transport water.

Energy from the Sun enables photosynthesis in plants, which provides the oxygen we breathe and helps grow the food we eat.

Creative Commons Stephen Bowler

How do Humans Benefit from the Sun's Energy?

Throughout history, humans have used technology to harness the Sun’s energy as a source of light and heat and for growing crops. As early as 30 CE, people were constructing greenhouses to grow plants out of season. Did you know that one of the earliest greenhouses was built for the Roman emperor Tiberius using translucent sheets of mica, all so that he could eat cucumbers in any season?

Early civilizations knew that setting up shelters to capture or block sunlight could help with heating and cooling. In cold climates, they would position buildings to face southward, allowing interior spaces to gather heat and light. In warm climates, shelters might be constructed under cliffs or natural overhangs to protect the residents from the Sun’s radiation in the hottest part of the day. Using energy from the Sun effectively also helped with growing crops.

The cliff dwellings at Mesa Verde National Park in Colorado, USA, were built in the shadows of rock overhangs to help keep the structures cool in the hot desert sunlight.

Creative Commons Steven Zucker

Today, we can intentionally position windows and skylights to help heat or cool our homes through passive solar design. Solar panels can also capture energy from the Sun by gathering sunlight and converting it to electricity. As of 2023, solar power is the third largest source of renewable energy worldwide, behind hydropower and wind.

How is Energy from the Sun Harmful?

UV radiation can damage skin and cause sunburn, but simple actions such as wearing a hat and sunscreen provide essential protection from the Sun’s harmful UV rays. 

Some of the Sun’s energy reaches Earth in the form ultraviolet (or UV) radiation. Fortunately, the ozone layer high in Earth’s atmosphere absorbs a lot of this UV radiation and blocks it from reaching Earth’s surface. But some UV still makes it through. UV radiation from the Sun causes sunburn and skin damage but can be blocked with clothes and sunscreen. Wearing hats and sunglasses in bright sunlight and trying to stay in the shade when possible can also help protect you from harmful UV rays. Note that it’s not realistic or advisable to avoid all exposure to sunlight, as sunlight also helps our bodies produce vitamin D, which we need to be healthy.

UV radiation can damage plants and limit photosynthesis. Scientists have found that overexposure to UV radiation reduces size, productivity, and quality in several crop species, including many varieties of rice, soybeans, winter wheat, cotton, and corn. Sometimes, UV can cause bleaching of plants, visible as damage or discoloration. Planting tender young plants in the shadow of larger plants can help protect them from UV radiation.

• Electromagnetic Spectrum
• Types of Light from the Sun
• Visible Light
• Ultraviolet Radiation
• What is Space Weather and How Does it Affect the Earth?

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This Graphic Maps the Greenest Modes of Transportation

What's the most energy efficient way to go from New York City to Toronto? You might be surprised.

There are many ways to go from here to there.

And the mode of transportation we choose can have a big impact. It can affect time, comfort, cost, and other factors. But how we travel can also have a big impact on the planet.

In the U.S., the transportation sector is responsible for about 28 percent of total greenhouse gases, according to the EPA . That's the largest contributor, just edging out the energy sector.

And although cleaner alternatives are coming on board, such as electric cars and biofuels, over 90 percent of the fuel used for transportation in the U.S. remains derived from petroleum.

In this graphic, we break down the most efficient ways to travel on a typical trip:

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Life on Other Planets: What is Life and What Does It Need?

One day, perhaps in the not-too-distant future, a faraway planet could yield hints that it might host some form of life – but surrender its secrets reluctantly.

Our space telescopes might detect a mixture of gases in its atmosphere that resembles our own. Computer models would offer predictions about the planet’s life-bearing potential. Experts would debate whether the evidence made a strong case for the presence of life, or try to find still more evidence to support such a groundbreaking interpretation.

“We are in the beginning of a golden era right now,” said Ravi Kopparapu, a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who studies habitable planets. “For the first time in the history of civilization we might be able to answer the question: Is there life beyond Earth?”

For exoplanets – planets around other stars – that era opens with NASA’s James Webb Space Telescope. Instruments aboard the spacecraft are detecting the composition of atmospheres on exoplanets. As the power of telescopes increases in the years ahead, future advanced instruments could capture possible signs of life – “biosignatures” – from a planet light-years away.

Within our solar system, the Perseverance rover on Mars is gathering rock samples for eventual return to Earth, so scientists can probe them for signs of life. And the coming Europa Clipper mission will visit an icy moon of Jupiter. Its goal: to determine whether conditions on that moon would allow life to thrive in its global ocean, buried beneath a global ice shell.

But any hints of life beyond Earth would come with another big question: How certain could any scientific conclusions really be?

“The challenge is deciding what is life – when to say, ‘I found it,’” said Laurie Barge of the Origins and Habitability Lab at NASA’s Jet Propulsion Laboratory in Southern California.

With so much unknown about what even constitutes a “sign of life,” astrobiologists are working on a new framework to understand the strength of the evidence. A sample framework, proposed in 2021, includes a scale ranging from 1 to 7, with hints of other life at level 1, to increasingly substantial evidence, all the way to certainty of life elsewhere at level 7. This framework, which is being discussed and revised, acknowledges that scientific exploration in the search for life is a twisted, winding road, rather than a straightforward path.

And identifying definitive signs remains difficult enough for “life as we know it.” Even more uncertain would be finding evidence of life as we don’t know it, made of unfamiliar molecular combinations or based on a solvent other than water.

Still, as the search for life begins in earnest, among the planets in our own solar system as well as far distant systems known only by their light, NASA scientists and their partners around the world have some ideas that serve as starting points.

Life That Evolves

First, there’s NASA’s less-than-formal, non-binding but still helpful working definition of life: “A self-sustaining chemical system capable of Darwinian evolution.” Charles Darwin famously described evolution by natural selection, with characteristics preserved across generations leading to changes in organisms over time.

Derived in the 1990s by a NASA exobiology working group, the definition is not used to design missions or research projects. It does help to set expectations, and to focus debate on the critical issues around another thorny question: When does non-life become life?

“Biology is chemistry with history,” says Gerald Joyce, one of the members of the working group that helped create the NASA definition and now a research professor at the Salk Institute in La Jolla, California.

That means history recorded by the chemistry itself – in our case, inscribed in our DNA, which encodes genetic data that can be translated into the structures and physical processes that make up our bodies.

The DNA record must be robust, complex, self-replicating and open-ended, Joyce suggests, to endure and adapt over billions of years.

“That would be a smoking gun: evidence for information having been recorded in molecules,” Joyce said.

Such a molecule from another world in our solar system, whether DNA, RNA or something else, might turn up in a sample from Mars, say from the Mars sample-return mission now being planned by NASA.

Or it might be found among the “ocean worlds” in the outer solar system – Jupiter’s moon, Europa, Saturn’s Enceladus or one of the other moons of gas giants that hide vast oceans beneath shells of ice.

We can’t obtain samples of such information-bearing molecules from planets beyond our solar system, since they are so far away that it would take tens of thousands of years to travel there even in the fastest spaceships ever built. Instead, we’ll have to rely on remote detection of potential biosignatures, measuring the types and quantities of gases in exoplanet atmospheres to try to determine whether they were generated by life-forms. That likely will require deeper knowledge of what life needs to get its start – and to persist long enough to be detected.

A Place Where Life Emerges

There is no true consensus on a list of requirements for life, whether in our solar system or the stars beyond. But Joyce, who researches life’s origin and development, suggests a few likely “must-haves.”

Topping the list is liquid water. Despite a broad spectrum of environmental conditions inhabited by living things on Earth, all life on the planet seems to require it. Liquid water provides a medium for the chemical components of life to persist over time and come together for reactions, in a way that air or the surface of a rock don’t do as well.

Also essential: an energy source, both for chemical reactions that produce structures and to create “order” against the universal tendency toward “disorder” – also known as entropy.

An imbalance in atmospheric gases also might offer a tell-tale sign of the presence of life.

“In Earth’s atmosphere, oxygen and methane are highly reactive with each other,” Kopparapu said. Left to themselves, they would quickly cancel each other out.

“They should not be seen together,” he said. “So why are we seeing methane, why are we seeing oxygen? Something must be constantly replenishing these compounds.”

On Earth, that “something” is life, pumping more of each into the atmosphere and keeping it out of balance. Such an imbalance, in these compounds or others, could be detected on a distant exoplanet, suggesting the presence of a living biosphere. But scientists also will have to rule out geological processes like volcanic or hydrothermal activity that could generate molecules that we might otherwise associate with life.

Careful laboratory work and precision modeling of possible exoplanet atmospheres will be needed to tell the difference.

Going Through Changes

Barge also places high on the list the idea of “gradients,” or changes that occur over time and distance, like wet to dry, hot to cold, and many other possible environments. Gradients create places for energy to go, changing along the way and generating molecules or chemical systems that later might be incorporated into life-forms.

Plate tectonics on Earth, and the cycling of gases like carbon dioxide – buried beneath Earth’s crust by subduction, perhaps, or released back into the atmosphere by volcanoes – represent one kind of gradient.

Barge’s specialty, the chemistry of hydrothermal vents on the ocean floor billions of years ago, is another. It’s one possible pathway to have created a kind of primitive metabolism – the translation of organic compounds into energy – as a potential precursor to true life-forms.

“What gradients existed before life?” she asks. “If life depends so much on gradients, could the origin of life also have benefited from these gradients?”

Clearer mapping of possible pathways to life ultimately could inform the design of future space telescopes, tasked with parsing the gases in the atmospheres of potentially habitable exoplanets.

“If we want to be sure it’s coming from biology, we have to not only look for gases; we have to look at how it’s being emitted from the planet, if it’s emitted in the right quantities, in the right way,” Kopparapu said. “With future telescopes, we’ll be more confident because they’ll be designed to look for life on other planets.”

Search for Life

This article is one in a series about how NASA is searching for life in the cosmos.

Beginnings: Life on Our World and Others

The Hunt for Life on Mars – and Elsewhere in the Solar System

'Life' in the Lab

Searching for Signs of Intelligent Life: Technosignatures

Finding Life Beyond Earth: What Comes Next?

Related Terms

• Terrestrial Exoplanets
• The Search for Life

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Black Holes

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Here’s How To Become a Travel Agent and Earn $3,000 Monthly

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No matter the type of travel you enjoy doing travel planning takes attention to detail mixed with a bit of the spirit of adventure. Every once in a while when the stars align you can take what you love to do and turn it into a living. It’s time to pack your go bag and explore the travel agency world .

See Also: 6 Unusual Ways To Make Extra Money (That Actually Work)

How To Become a Travel Agent

Just because someone has travel experience does not mean they can automatically become a travel agent. However, if you are interested in becoming a travel agent there are many programs you can take to help you become one, or even start your own business. Skills you will learn include how to organize travel arrangements, business ethics, customer service, itinerary planning and the ins and outs of travel insurance.

No matter your career goals, whether you want to focus on luxury travel or more of a local tour operation, the following programs and certifications, which can be done in person or remotely, can get you started on the right path.

• Departure Lounge: Learn how to navigate the hotel industry as an independent contractor as well as get tips on tour operating.
• Premier Cruise Lines: Many lines such as Virgin Voyages, Cunard or Ritz-Carlton Yachts provide training programs for travel agents to help them sell their products and services more efficiently.
• Get Certified: When your training and coursework are complete a certification helps distinguish you in the field with these designations. Some popular ones include the International Air Transport Association, Cruise Line International Association or Travel Industry Designator Service. Be sure to research which certification makes the most sense for you as it will imply different things for your business.

How Much Do Travel Agents Make?

The median pay for what travel agents get paid in the United States is estimated to be about $46,400 annually which is over $3,000 monthly. This may seem underwhelming, but this is an estimate by the U.S. Bureau of Labor Statistics which means is only based on what full-time employees make and not self-employed people. In other words, you can make a lot more money as an independent travel advisor as opposed to working for a host agency. 

Travel agents make money by earning commissions on trips they book as well as charging fees such as booking or service fees. This is a great way to also set your own schedule and only choose the gigs you like. 

Final Take To GO: Love To Travel?

When it comes to starting as a travel agent, a good rule to follow is to try to sell and book trips you yourself would want to take. If you already love to travel this could be a natural next step in your career or a budding side business. 

A great way to sell yourself as a travel agent is to define your unique selling point. Essentially what is it about you that will make people want to book trips with you? It also helps to optimize your website, create high-quality content from trips you’ve booked or been on and leverage your social media platforms. Once you have your foundation firmly established, everything else is booking a day at the beach. 

• Full-time travel agents make roughly $46,400 a year which is over $3,000 a month. However, there is a chance to make more money than this estimate by starting your own travel agency and working for yourself. This way you can set your own schedule and don't have to worry about splitting your commissions.
• You don't need a specific degree to get started as a travel agent, but finding a training program and getting certified with varying destinations does help distinguish you as a trusted travel agent to your potential clients.
• Selling yourself as a travel agent, much like with any job or small business, starts with defining your unique selling point. Essentially what is it about you that will make people want to book trips with you? It also helps to optimize your website, create high-quality content from trips you've booked or been on and leverage your social media platforms.
• Get Certified: When your training and coursework are complete a certification helps distinguish you in the field with these designations. Some popular ones include the International Air Transport Association, Cruise Line International Association or Travel Industry Designator Service. Research which certification makes the most sense for you as it will imply different things for your business.

Our in-house research team and on-site financial experts work together to create content that’s accurate, impartial, and up to date. We fact-check every single statistic, quote and fact using trusted primary resources to make sure the information we provide is correct. You can learn more about GOBankingRates’ processes and standards in our editorial policy .

• Condé Nast Traveler. 2023. "How to Become a Travel Agent—Because, Believe It or Not, the Industry Is on the Rise."
• U.S. Bureau of Labor Statistics. 2024. "Travel Agents: Occupational Outlook Handbook."
• Host Agency Reviews®. 2024. "How Much Do Travel Agents Make? | 2024 Travel Agent Salary."

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5 ways sustainable forestry can support climate action, development and biodiversity

Sustainable forestry can catalyse climate action. Image:  Timberland Investment Group

.chakra .wef-1c7l3mo{-webkit-transition:all 0.15s ease-out;transition:all 0.15s ease-out;cursor:pointer;-webkit-text-decoration:none;text-decoration:none;outline:none;color:inherit;}.chakra .wef-1c7l3mo:hover,.chakra .wef-1c7l3mo[data-hover]{-webkit-text-decoration:underline;text-decoration:underline;}.chakra .wef-1c7l3mo:focus,.chakra .wef-1c7l3mo[data-focus]{box-shadow:0 0 0 3px rgba(168,203,251,0.5);} Charlotte Kaiser

.chakra .wef-9dduvl{margin-top:16px;margin-bottom:16px;line-height:1.388;font-size:1.25rem;}@media screen and (min-width:56.5rem){.chakra .wef-9dduvl{font-size:1.125rem;}} Explore and monitor how .chakra .wef-15eoq1r{margin-top:16px;margin-bottom:16px;line-height:1.388;font-size:1.25rem;color:#F7DB5E;}@media screen and (min-width:56.5rem){.chakra .wef-15eoq1r{font-size:1.125rem;}} SDG 15: Life on Land is affecting economies, industries and global issues

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Stay up to date:, sdg 15: life on land.

• Sustainable forestry can catalyze climate action through reforestation and sustainable management of working forests.
• By increasing demand for sustainably produced forest products, we can incentivize reforestation on a meaningful scale.
• Innovative financing models could combine commercial forestry with the protection and restoration of natural ecosystems.

Envisioning a climate-stable future requires a dual strategy as far as the world’s forests are concerned: protecting and restoring natural forests for all of their ecological and climate benefits while also sustainably managing working forests to drive the global transformation to a sustainable, circular bioeconomy.

Many are uncomfortable at the thought of cutting down a tree. While wood is a useful material, people don't like the idea that it should be harvested from a forest. In a 2017 study commissioned by the North American Forest Partnership, nearly four out of five respondents thought wood was a renewable material; however, fewer than one in five associated the forest sector with sustainability.

That’s an unfortunate misconception and in our current era of climate disasters, it’s becoming a dangerous one. The reality is that sustainable forestry and forest products can help us save the planet from ourselves. Here are five ways how.

Have you read?

Why companies must invest in innovative solutions for forest conservation and restoration, why forest restoration needs a 100-year plan and indigenous multi-gen leadership, 1. investing in reforestation.

The forest sector holds both the responsibility and opportunity to advance some of the solutions the world needs to minimize waste and ensure nature thrives – putting it on the frontline of climate action.

Firstly, forestry’s carbon footprint is already quite low compared with other industries and increasing demand for sustainably produced forest products can drive reforestation at meaningful scales, delivering significant climate benefits. A durable market for sustainable wood products creates economic support for landowners to plant trees, manage the growing forests and replant new trees as they are harvested. Research has shown that when forest product prices rise in the United States, landowners plant more trees.

There is often public concern that increasing demand for forest products drives deforestation of natural forests, yet the opposite is often true. Most deforestation is driven by conversion to agriculture . Driving up the economic value of sustainable working forests is a proven way to prevent the conversion of forests to alternative forms of land use. Research has also found that forests managed for sustained timber production can be more resistant to deforestation, from the Democratic Republic of Congo to Guatemala .

Of course, a small share of deforestation results from the demand for forest products. To address this, producers and consumers of these products must make and adhere to firm commitments to deforestation-free operations and supply chains.

2. Investing in natural forest restoration

Given its close relationship with nature, the forest sector is crucial in contributing to regenerating and restoring nature globally through management practices that meaningfully improve the health and resilience of ecosystems, species and people.

Driven by the growing demand among investors for greater climate and nature impact and high-quality nature-based carbon credits, companies, NGOs and communities are innovating new approaches that link financing for commercial forestry with efforts to protect and restore natural ecosystems. These efforts include restoring peatland and wetlands, reintroducing native and endangered tree species on degraded lands, creating wildlife corridors and enhancing soil carbon stocks.

For example, the Timberland Investment Group, where I work, with Conservation International’s support , is undertaking a $1 billion strategy to invest in properties in Latin America that have been previously deforested to protect and restore natural forest on half the land acquired under the strategy and establish sustainably managed commercial tree farms on the other half.

3. Supporting Indigenous peoples and local communities

The traditional territories of Indigenous and local communities cover a quarter of the Earth’s lands but contain 80% of Earth’s remaining biodiversity . It is estimated that nearly 200 million Indigenous people depend on forests for their livelihoods. Support for sustainable forest products can direct capital into Indigenous-managed landscapes while supporting livelihoods that represent an alternative to expanding the agricultural frontier.

There are a growing number of examples of this strategy’s success, including the work being supported by the Nature Conservancy within the Moomba community in Zambia, which has won the right to sustainably harvest and profit from its forest resources.

4. Reducing pressure on intact forests and their biodiversity

Deforestation is a critical threat to biodiversity, and protecting our existing forests is one of the best ways to preserve the world’s remaining forest ecosystems.

Planted forests comprise only 7% of the world’s forest area but provide almost half its commercial timber. Sustainable management of these planted forests can help meet the growing demand for renewable materials while reducing pressure on natural forests and their rich biodiversity.

5. Reducing the carbon footprint of construction

The forest sector is well-positioned to grow the circular bioeconomy using wood from sustainable working forests as a renewable material. Turning sustainably harvested trees into long-lived wood products like mass timber can substitute for carbon-intensive concrete and steel and turn new buildings' walls, floors and ceilings into carbon vaults that persist for decades or longer.

A recent study suggests that widespread adoption of mass timber worldwide could, by 2100, reduce annual global emissions by an amount equivalent to nearly half the total emissions of the entire United States. Scaling up this alternative economic model requires deliberate and collaborative action along the entire forest products value chain and within the broader operating environment.

In short, the forest sector lies at the heart of the needed transition to a low-carbon, circular bioeconomy due to the ability of working forests and sustainable forest products to capture and store carbon; to reduce pressure on intact ecosystems and the species that call them home; to support equitable development across rural landscapes; and provide new funding models for natural restoration at large scales.

Indeed, in the right circumstances, cutting down trees – and replanting them – can deliver all these benefits and more.

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Governments could be the gateway to industrial electrification and a sustainable future

Jan Rosenow, Cristina Oyón, Natalia Zabolotnikova and Xabier Mugarza Zorriqueta

Agritech: Shaping Agriculture in Emerging Economies, Today and Tomorrow

Electric vehicles are key to the energy transition - but the switch must be sustainable. Here's why

Lisa Donahue and Vance Scott

April 28, 2024

What is Arbor Day and why is it important?

April 24, 2024

The green skills gap: Educational reform in favour of renewable energy is now urgent

Roman Vakulchuk