can radio waves travel through a vacuum

How do electromagnetic waves travel in a vacuum?

Explore how electromagnetic waves propagate in a vacuum, their unique characteristics, and their critical role in interstellar communication.

Understanding Electromagnetic Waves in Vacuum

Electromagnetic waves, a fundamental aspect of the physical world, include a broad spectrum of waves such as radio waves, microwaves, infrared waves, visible light, ultraviolet light, X-rays, and gamma rays. In a vacuum, the propagation of these waves becomes particularly interesting due to the lack of a medium.

Propagating Electromagnetic Waves

Electromagnetic waves are created when an electric charge vibrates or accelerates. Each wave is characterized by an electric and a magnetic field. These fields oscillate perpendicular to each other and to the direction of the wave’s motion, forming a three-dimensional wave pattern.

Crucially, unlike mechanical waves (such as sound waves), electromagnetic waves do not require a medium to propagate. This allows them to travel in the emptiness of space – a vacuum – at a constant speed, known as the speed of light (c). In a vacuum, this speed is approximately 299,792 kilometers per second.

Why Do Electromagnetic Waves Travel in Vacuum?

Understanding why electromagnetic waves can travel in a vacuum involves delving into the fundamentals of electromagnetic theory, most comprehensively described by James Clerk Maxwell’s equations.

Maxwell’s equations show that a changing electric field generates a changing magnetic field, and vice versa. When an electric charge vibrates, it creates a changing electric field. This changing electric field in turn generates a changing magnetic field, which then induces another changing electric field. This process repeats, allowing the electromagnetic wave to propagate forward as a self-sustaining entity, even in a vacuum.

Impact on Interstellar Communication

The ability of electromagnetic waves to propagate in a vacuum has profound implications for interstellar communication and observation. For instance, light from distant stars and galaxies reaches Earth across the vacuum of space, providing astronomers with invaluable data about the universe. Similarly, radio signals sent from Earth can travel through space to reach distant spacecraft.

In conclusion, electromagnetic waves exhibit fascinating behavior in a vacuum, propagating as self-sustaining entities due to the mutual generation of electric and magnetic fields. This characteristic enables them to serve as crucial messengers across the vast expanses of the cosmos.

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Anatomy of an Electromagnetic Wave

Energy, a measure of the ability to do work, comes in many forms and can transform from one type to another. Examples of stored or potential energy include batteries and water behind a dam. Objects in motion are examples of kinetic energy. Charged particles—such as electrons and protons—create electromagnetic fields when they move, and these fields transport the type of energy we call electromagnetic radiation, or light.

What are Electromagnetic and Mechanical waves?

Mechanical waves and electromagnetic waves are two important ways that energy is transported in the world around us. Waves in water and sound waves in air are two examples of mechanical waves. Mechanical waves are caused by a disturbance or vibration in matter, whether solid, gas, liquid, or plasma. Matter that waves are traveling through is called a medium. Water waves are formed by vibrations in a liquid and sound waves are formed by vibrations in a gas (air). These mechanical waves travel through a medium by causing the molecules to bump into each other, like falling dominoes transferring energy from one to the next. Sound waves cannot travel in the vacuum of space because there is no medium to transmit these mechanical waves.

ELECTROMAGNETIC WAVES

Electricity can be static, like the energy that can make your hair stand on end. Magnetism can also be static, as it is in a refrigerator magnet. A changing magnetic field will induce a changing electric field and vice-versa—the two are linked. These changing fields form electromagnetic waves. Electromagnetic waves differ from mechanical waves in that they do not require a medium to propagate. This means that electromagnetic waves can travel not only through air and solid materials, but also through the vacuum of space.

In the 1860's and 1870's, a Scottish scientist named James Clerk Maxwell developed a scientific theory to explain electromagnetic waves. He noticed that electrical fields and magnetic fields can couple together to form electromagnetic waves. He summarized this relationship between electricity and magnetism into what are now referred to as "Maxwell's Equations."

Heinrich Hertz, a German physicist, applied Maxwell's theories to the production and reception of radio waves. The unit of frequency of a radio wave -- one cycle per second -- is named the hertz, in honor of Heinrich Hertz.

His experiment with radio waves solved two problems. First, he had demonstrated in the concrete, what Maxwell had only theorized — that the velocity of radio waves was equal to the velocity of light! This proved that radio waves were a form of light! Second, Hertz found out how to make the electric and magnetic fields detach themselves from wires and go free as Maxwell's waves — electromagnetic waves.

WAVES OR PARTICLES? YES!

Light is made of discrete packets of energy called photons. Photons carry momentum, have no mass, and travel at the speed of light. All light has both particle-like and wave-like properties. How an instrument is designed to sense the light influences which of these properties are observed. An instrument that diffracts light into a spectrum for analysis is an example of observing the wave-like property of light. The particle-like nature of light is observed by detectors used in digital cameras—individual photons liberate electrons that are used for the detection and storage of the image data.

POLARIZATION

One of the physical properties of light is that it can be polarized. Polarization is a measurement of the electromagnetic field's alignment. In the figure above, the electric field (in red) is vertically polarized. Think of a throwing a Frisbee at a picket fence. In one orientation it will pass through, in another it will be rejected. This is similar to how sunglasses are able to eliminate glare by absorbing the polarized portion of the light.

DESCRIBING ELECTROMAGNETIC ENERGY

The terms light, electromagnetic waves, and radiation all refer to the same physical phenomenon: electromagnetic energy. This energy can be described by frequency, wavelength, or energy. All three are related mathematically such that if you know one, you can calculate the other two. Radio and microwaves are usually described in terms of frequency (Hertz), infrared and visible light in terms of wavelength (meters), and x-rays and gamma rays in terms of energy (electron volts). This is a scientific convention that allows the convenient use of units that have numbers that are neither too large nor too small.

The number of crests that pass a given point within one second is described as the frequency of the wave. One wave—or cycle—per second is called a Hertz (Hz), after Heinrich Hertz who established the existence of radio waves. A wave with two cycles that pass a point in one second has a frequency of 2 Hz.

Electromagnetic waves have crests and troughs similar to those of ocean waves. The distance between crests is the wavelength. The shortest wavelengths are just fractions of the size of an atom, while the longest wavelengths scientists currently study can be larger than the diameter of our planet!

An electromagnetic wave can also be described in terms of its energy—in units of measure called electron volts (eV). An electron volt is the amount of kinetic energy needed to move an electron through one volt potential. Moving along the spectrum from long to short wavelengths, energy increases as the wavelength shortens. Consider a jump rope with its ends being pulled up and down. More energy is needed to make the rope have more waves.

Next: Wave Behaviors

National Aeronautics and Space Administration, Science Mission Directorate. (2010). Anatomy of an Electromagnetic Wave. Retrieved [insert date - e.g. August 10, 2016] , from NASA Science website: http://science.nasa.gov/ems/02_anatomy

Science Mission Directorate. "Anatomy of an Electromagnetic Wave" NASA Science . 2010. National Aeronautics and Space Administration. [insert date - e.g. 10 Aug. 2016] http://science.nasa.gov/ems/02_anatomy

Discover More Topics From NASA

James Webb Space Telescope

Perseverance Rover

Parker Solar Probe

Electromagnetic Waves

Introduction to electromagnetic waves.

Figure 1. Human eyes detect these orange “sea goldie” fish swimming over a coral reef in the blue waters of the Gulf of Eilat (Red Sea) using visible light. (credit: Daviddarom, Wikimedia Commons)

The beauty of a coral reef, the warm radiance of sunshine, the sting of sunburn, the X-ray revealing a broken bone, even microwave popcorn—all are brought to us by electromagnetic waves . The list of the various types of electromagnetic waves, ranging from radio transmission waves to nuclear gamma-ray ( γ -ray) emissions, is interesting in itself.

Even more intriguing is that all of these widely varied phenomena are different manifestations of the same thing—electromagnetic waves. (See Figure 2.) What are electromagnetic waves? How are they created, and how do they travel? How can we understand and organize their widely varying properties? What is their relationship to electric and magnetic effects? These and other questions will be explored.

Misconception Alert: Sound Waves vs. Radio Waves

Many people confuse sound waves with radio waves , one type of electromagnetic (EM) wave. However, sound and radio waves are completely different phenomena. Sound creates pressure variations (waves) in matter, such as air or water, or your eardrum. Conversely, radio waves are electromagnetic waves , like visible light, infrared, ultraviolet, X-rays, and gamma rays. EM waves don’t need a medium in which to propagate; they can travel through a vacuum, such as outer space.

A radio works because sound waves played by the D.J. at the radio station are converted into electromagnetic waves, then encoded and transmitted in the radio-frequency range. The radio in your car receives the radio waves, decodes the information, and uses a speaker to change it back into a sound wave, bringing sweet music to your ears.

Discovering a New Phenomenon

Figure 2. The electromagnetic waves sent and received by this 50-foot radar dish antenna at Kennedy Space Center in Florida are not visible, but help track expendable launch vehicles with high-definition imagery. The first use of this C-band radar dish was for the launch of the Atlas V rocket sending the New Horizons probe toward Pluto. (credit: NASA)

It is worth noting at the outset that the general phenomenon of electromagnetic waves was predicted by theory before it was realized that light is a form of electromagnetic wave. The prediction was made by James Clerk Maxwell in the mid-19th century when he formulated a single theory combining all the electric and magnetic effects known by scientists at that time. “Electromagnetic waves” was the name he gave to the phenomena his theory predicted.

Such a theoretical prediction followed by experimental verification is an indication of the power of science in general, and physics in particular. The underlying connections and unity of physics allow certain great minds to solve puzzles without having all the pieces. The prediction of electromagnetic waves is one of the most spectacular examples of this power. Certain others, such as the prediction of antimatter, will be discussed in later modules.

• College Physics. Authored by : OpenStax College. Located at : http://cnx.org/contents/031da8d3-b525-429c-80cf-6c8ed997733a/College_Physics . License : CC BY: Attribution . License Terms : Located at License

How Sound, Light, and Radio Waves Travel

What exactly does the term “wave” imply? A wave is a disturbance that moves or spreads from its source. Waves transfer energy, but they do not necessarily carry any mass along with them.

Waves are a form of longitudinal motion. Sound and water waves are mechanical waves, which means they need a medium to travel through. A solid, liquid, or gas may be the medium, and the speed of the wave is determined by the physical characteristics of the medium in which it is traveling.

However, light and radio are not mechanical waves; they can propagate through a vacuum, such as the voids in outer space.

Why Can’t Sound Travel in Space?

Sound waves are caused by air vibrations. We humans hear them when the frequencies range from 20 to 20,000 Hz.

Sound waves are produced when particles in a medium vibrate. These vibrations are transmitted to the following molecules in the medium, thus sound waves cannot travel through space without a medium. The reason we can’t hear anything in outer space is because there isn’t any such thing as a sufficient medium.

We may debate about gases serving as media in space, but gases are unevenly distributed throughout the space. Furthermore, gases are generally less dense in space, so there is too much of a gap between the particles for vibrations to travel effectively.

In basic terms, sound cannot travel in space.

Why Do Sound Waves Require a Medium to Travel?

The water wave is a familiar phenomenon that you can readily picture. The disturbance in water waves occurs at the surface of the water, as evidenced by a rock thrown into a pond or a swimmer splashing the water’s surface repeatedly.

The disturbance in sound waves is caused by a variation in air pressure, as demonstrated by the following: When a speaker’s oscillating cone creates an uproar. There are several types of disturbances associated with earthquakes, some of which are the surface disturbance and pressure changes beneath the surface.

Water waves are one of the most well-known types of waves, and for good reason. Water waves are often and readily observable, so thinking about water waves might help you understand other sorts of waves that aren’t as apparent.

Do Radio Waves Require a Medium to Travel?

No, radio waves are electromagnetic radiation. Electromagnetic waves differ from mechanical waves in that they do not need a medium to travel. This implies that electromagnetic radiation may propagate through both air and solid materials as well as vacuum space.

The wave is the oscillation of some variable within a body in many types of waves, such as sound waves or water waves. The pressure of the air is responsible for sound waves, while the height of the water in a lake or ocean causes water waves.

However, the electric and magnetic fields in space are oscillating which are electromagnetic waves . The electric and magnetic fields are force fields that exist without a medium. They’re simply there. Electric charges and currents give rise to them, and they span the vacuum from their origins through the cosmos.

When an electric charge or current fluctuates, the accompanying magnetic and electric fields likewise fluctuate. However, these waves don’t appear instantly everywhere; instead, they spread at the speed of light from the original source.

Why Doesn’t Light Need a Medium to Travel?

A light wave is an electromagnetic wave. It does not require any medium because it travels through space without relying on medium particles. Light, in a nutshell, is an electromagnetic radiation caused by the disruption of electric and magnetic fields.

The direction of propagation of the electric and magnetic fields which are mutually perpendicular supports each other to travel in a perpendicular direction. Light is capable of traveling without medium because it may be generated and propagated through vacuum (or no medium).

The concept of light’s particles, originally developed by German philosopher and physicist Ernst Mach in the 19th century, implies that light is made up of tiny energy bundle packets known as “photons.” Because light follows the principles of wave-particle duality, it exists in two states: particle and wave. From this perspective, these energized photons travel alone without the assistance of a medium.

Also, it’s from these photons that color is visible to us humans.

Think of it another way.

We understand that light does not require a medium to travel since the speed of light is experimentally constant: it does not vary regardless of the source, detector, or direction in which it travels.

Light and sound clash, the latter which is transmitted through the air (or some other material medium). The speed of sound in all directions is the same if you’re stationary with respect to the air. But if you’re moving with respect to the air, the speed of sound will be the same in all directions relative to the air—which means that sound coming up ahead of you will seem faster, and sounds catching up from behind will appear slower.

Light would act in the same way if it were a disturbance in a medium. However, light’s speed will always be constant under all circumstances. It is a the universal constant after all.

Related posts:

• Radio Waves in Space
• Why does Radar Use Radio Waves?
• How Far Can a Laser Travel?
• How and Why We See Colors

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Turns out you can transmit sound in a vacuum, just not very far

For the first time, researchers were able to transmit, or "tunnel," sound waves across extremely small distances between two crystals in a vacuum.

For the first time, scientists have shown that sound can travel through the emptiness of a vacuum. However, the rule-breaking trick requires specific circumstances and can only be carried out over extremely small distances.

The iconic tagline of the 1979 sci-fi film "Alien" tells us that "in space no one can hear you scream." This was based on the fact that space is a vacuum, a region devoid of any particles. Sound waves travel by vibrating through the particles of a medium, such as air or water, from a source to a receiver. So in a vacuum, there is no travel medium. (Outer space is not actually a total vacuum because it does contain small amounts of gas, plasma and other particles. But this matter is surrounded by vast swathes of emptiness.)

But in a new study, published July 14 in the journal Communications Physics , researchers showed that sound can move through a vacuum. Unfortunately for space explorers being hunted by aliens, this does not extend to human screams.

In the new experiment, researchers transmitted, or "tunneled," sound waves across a vacuum between two zinc oxide crystals by transforming the vibrating waves into ripples within an electric field between the objects.

Related: Physicists mimic gravity inside the sun using sound waves

A zinc oxide crystal is a piezoelectric material, which means that when force or heat is applied to it, the material produces an electrical charge. Therefore, when sound is applied to one of these crystals, it creates an electrical charge that disrupts nearby electric fields. If the crystal shares an electric field with another crystal, then the magnetic disruption can travel from one to the other across a vacuum. The disruptions mirror the frequency of the sound waves, so the receiving crystal can turn the disruption back into a sound on the other side of the vacuum.

However, the disruptions cannot travel a distance greater than the wavelength of a single sound wave. In theory, this works with any sound no matter how small the wavelength of that sound is, as long as the gap between the crystals is small enough. 

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The method is not always reliable. In a large percentage of the experiments, the sound was not perfectly transmitted between the two crystals: parts of the wave were warped, or reflected, as it passed through the electric field, the researchers found. However, occasionally the piezoelectric crystals perfectly transmitted the entire sound wave.

— Listen to the sound of 3 stars playing 'Twinkle Twinkle Little Star' (video)

—  Ancient star that crashed hot young star party could solve solar system mystery

—  Sounds in space: What noises do planets make?

"In most cases the effect [sound transmitted] is small, but we also found situations, where the full energy of the wave jumps across the vacuum with 100 % efficiency, without any reflections," study co-author Ilari Maasilta , a material physicist at the University of Jyväskylä in Finland, said in a statement .

The finding could one day help develop microelectromechanical components, like those found in smartphones and other technology, the researchers said. 

This story was originally published on Live Science .

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Harry is a U.K.-based staff writer at Live Science. He studied Marine Biology at the University of Exeter (Penryn campus) and after graduating started his own blog site "Marine Madness," which he continues to run with other ocean enthusiasts. He is also interested in evolution, climate change, robots, space exploration, environmental conservation and anything that's been fossilized. When not at work he can be found watching sci-fi films, playing old Pokemon games or running (probably slower than he'd like). 

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13.1 Types of Waves

Section learning objectives.

By the end of this section, you will be able to do the following:

• Define mechanical waves and medium, and relate the two
• Distinguish a pulse wave from a periodic wave
• Distinguish a longitudinal wave from a transverse wave and give examples of such waves

Teacher Support

The learning objectives in this section will help your students master the following standards:

• (A) examine and describe oscillatory motion and wave propagation in various types of media.

Section Key Terms

Mechanical waves.

What do we mean when we say something is a wave? A wave is a disturbance that travels or propagates from the place where it was created. Waves transfer energy from one place to another, but they do not necessarily transfer any mass. Light, sound, and waves in the ocean are common examples of waves. Sound and water waves are mechanical waves ; meaning, they require a medium to travel through. The medium may be a solid, a liquid, or a gas, and the speed of the wave depends on the material properties of the medium through which it is traveling. However, light is not a mechanical wave; it can travel through a vacuum such as the empty parts of outer space.

A familiar wave that you can easily imagine is the water wave. For water waves, the disturbance is in the surface of the water, an example of which is the disturbance created by a rock thrown into a pond or by a swimmer splashing the water surface repeatedly. For sound waves, the disturbance is caused by a change in air pressure, an example of which is when the oscillating cone inside a speaker creates a disturbance. For earthquakes, there are several types of disturbances, which include the disturbance of Earth’s surface itself and the pressure disturbances under the surface. Even radio waves are most easily understood using an analogy with water waves. Because water waves are common and visible, visualizing water waves may help you in studying other types of waves, especially those that are not visible.

Water waves have characteristics common to all waves, such as amplitude , period , frequency , and energy , which we will discuss in the next section.

Misconception Alert

Many people think that water waves push water from one direction to another. In reality, however, the particles of water tend to stay in one location only, except for moving up and down due to the energy in the wave. The energy moves forward through the water, but the water particles stay in one place. If you feel yourself being pushed in an ocean, what you feel is the energy of the wave, not the rush of water. If you put a cork in water that has waves, you will see that the water mostly moves it up and down.

[BL] [OL] [AL] Ask students to give examples of mechanical and nonmechanical waves.

Pulse Waves and Periodic Waves

If you drop a pebble into the water, only a few waves may be generated before the disturbance dies down, whereas in a wave pool, the waves are continuous. A pulse wave is a sudden disturbance in which only one wave or a few waves are generated, such as in the example of the pebble. Thunder and explosions also create pulse waves. A periodic wave repeats the same oscillation for several cycles, such as in the case of the wave pool, and is associated with simple harmonic motion. Each particle in the medium experiences simple harmonic motion in periodic waves by moving back and forth periodically through the same positions.

[BL] Any kind of wave, whether mechanical or nonmechanical, or transverse or longitudinal, can be in the form of a pulse wave or a periodic wave.

Consider the simplified water wave in Figure 13.2 . This wave is an up-and-down disturbance of the water surface, characterized by a sine wave pattern. The uppermost position is called the crest and the lowest is the trough . It causes a seagull to move up and down in simple harmonic motion as the wave crests and troughs pass under the bird.

Longitudinal Waves and Transverse Waves

Mechanical waves are categorized by their type of motion and fall into any of two categories: transverse or longitudinal. Note that both transverse and longitudinal waves can be periodic. A transverse wave propagates so that the disturbance is perpendicular to the direction of propagation. An example of a transverse wave is shown in Figure 13.3 , where a woman moves a toy spring up and down, generating waves that propagate away from herself in the horizontal direction while disturbing the toy spring in the vertical direction.

In contrast, in a longitudinal wave , the disturbance is parallel to the direction of propagation. Figure 13.4 shows an example of a longitudinal wave, where the woman now creates a disturbance in the horizontal direction—which is the same direction as the wave propagation—by stretching and then compressing the toy spring.

Tips For Success

Longitudinal waves are sometimes called compression waves or compressional waves , and transverse waves are sometimes called shear waves .

Teacher Demonstration

Transverse and longitudinal waves may be demonstrated in the class using a spring or a toy spring, as shown in the figures.

Waves may be transverse, longitudinal, or a combination of the two . The waves on the strings of musical instruments are transverse (as shown in Figure 13.5 ), and so are electromagnetic waves, such as visible light. Sound waves in air and water are longitudinal. Their disturbances are periodic variations in pressure that are transmitted in fluids.

Sound in solids can be both longitudinal and transverse. Essentially, water waves are also a combination of transverse and longitudinal components, although the simplified water wave illustrated in Figure 13.2 does not show the longitudinal motion of the bird.

Earthquake waves under Earth’s surface have both longitudinal and transverse components as well. The longitudinal waves in an earthquake are called pressure or P-waves, and the transverse waves are called shear or S-waves. These components have important individual characteristics; for example, they propagate at different speeds. Earthquakes also have surface waves that are similar to surface waves on water.

Energy propagates differently in transverse and longitudinal waves. It is important to know the type of the wave in which energy is propagating to understand how it may affect the materials around it.

Watch Physics

Introduction to waves.

This video explains wave propagation in terms of momentum using an example of a wave moving along a rope. It also covers the differences between transverse and longitudinal waves, and between pulse and periodic waves.

• After a compression wave, some molecules move forward temporarily.
• After a compression wave, some molecules move backward temporarily.
• After a compression wave, some molecules move upward temporarily.
• After a compression wave, some molecules move downward temporarily.

Fun In Physics

The physics of surfing.

Many people enjoy surfing in the ocean. For some surfers, the bigger the wave, the better. In one area off the coast of central California, waves can reach heights of up to 50 feet in certain times of the year ( Figure 13.6 ).

How do waves reach such extreme heights? Other than unusual causes, such as when earthquakes produce tsunami waves, most huge waves are caused simply by interactions between the wind and the surface of the water. The wind pushes up against the surface of the water and transfers energy to the water in the process. The stronger the wind, the more energy transferred. As waves start to form, a larger surface area becomes in contact with the wind, and even more energy is transferred from the wind to the water, thus creating higher waves. Intense storms create the fastest winds, kicking up massive waves that travel out from the origin of the storm. Longer-lasting storms and those storms that affect a larger area of the ocean create the biggest waves since they transfer more energy. The cycle of the tides from the Moon’s gravitational pull also plays a small role in creating waves.

Actual ocean waves are more complicated than the idealized model of the simple transverse wave with a perfect sinusoidal shape. Ocean waves are examples of orbital progressive waves , where water particles at the surface follow a circular path from the crest to the trough of the passing wave, then cycle back again to their original position. This cycle repeats with each passing wave.

As waves reach shore, the water depth decreases and the energy of the wave is compressed into a smaller volume. This creates higher waves—an effect known as shoaling .

Since the water particles along the surface move from the crest to the trough, surfers hitch a ride on the cascading water, gliding along the surface. If ocean waves work exactly like the idealized transverse waves, surfing would be much less exciting as it would simply involve standing on a board that bobs up and down in place, just like the seagull in the previous figure.

Additional information and illustrations about the scientific principles behind surfing can be found in the “Using Science to Surf Better!” video.

• The surfer would move side-to-side/back-and-forth vertically with no horizontal motion.
• The surfer would forward and backward horizontally with no vertical motion.

Check Your Understanding

Use these questions to assess students’ achievement of the section’s Learning Objectives. If students are struggling with a specific objective, these questions will help identify such objective and direct them to the relevant content.

• A wave is a force that propagates from the place where it was created.
• A wave is a disturbance that propagates from the place where it was created.
• A wave is matter that provides volume to an object.
• A wave is matter that provides mass to an object.
• No, electromagnetic waves do not require any medium to propagate.
• No, mechanical waves do not require any medium to propagate.
• Yes, both mechanical and electromagnetic waves require a medium to propagate.
• Yes, all transverse waves require a medium to travel.
• A pulse wave is a sudden disturbance with only one wave generated.
• A pulse wave is a sudden disturbance with only one or a few waves generated.
• A pulse wave is a gradual disturbance with only one or a few waves generated.
• A pulse wave is a gradual disturbance with only one wave generated.

What are the categories of mechanical waves based on the type of motion?

• Both transverse and longitudinal waves
• Only longitudinal waves
• Only transverse waves
• Only surface waves

In which direction do the particles of the medium oscillate in a transverse wave?

• Perpendicular to the direction of propagation of the transverse wave
• Parallel to the direction of propagation of the transverse wave

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Sound Really Can Travel in a Vacuum, And We Can Finally Explain How

August 16, 2023 by admin 0 Comments

Given the right circumstances, it is possible for sound to travel through a perfect vacuum. Now two physicists have worked out what those conditions need to be.

Zhuoran Geng and Ilari Maasilta of the University of Jyväskylä in Finland say their findings represent the first rigorous proof of complete acoustic tunneling in a vacuum.

To achieve it, you’ll need two piezoelectric materials, which are capable of turning movements into voltages (and vice versa). The objects need to be separated by a gap that’s smaller than the wavelength of the sound you want to send, which will then completely jump – or ‘tunnel’ – across that space.

We’ve known about acoustic wave tunneling since the 1960s , but scientists have only begun to investigate the phenomenon relatively recently, which means we don’t yet have a very good understanding of how it works.

Geng and Maasilta have been working on fixing that, first by describing a formalism for the study of acoustic tunneling, and now by applying it.

In order to propagate, sound requires a medium to travel through. Sound is generated by vibrations, which causes atoms and molecules in the medium to vibrate; that vibration is passed on to adjacent particles . We sense these vibrations via a sensitive membrane in our ears.

A perfect vacuum is a complete absence of a medium. Since there are no particles to vibrate, sound shouldn’t be able to propagate.

But there are loopholes. What qualifies as a vacuum can still buzz with electrical fields, which makes piezoelectric crystals an intriguing material for the study of sound across otherwise empty spaces.

These are materials that convert mechanical energy into electrical energy , and vice versa. In other words, if you place a mechanical stress on the crystal, it will produce an electric field. And if you expose the crystal to an electrical field, the crystal will deform. That’s known as the inverse piezoelectric effect .

OK this is where it gets fun. A sound vibration exerts mechanical stress. Using zinc oxide as their piezoelectric crystals, Geng and Maasilta found that a crystal can convert this stress into an electrical field if certain conditions are met.

If there is a second crystal within range of the first, it can convert the electrical energy back into mechanical energy – et voila, the sound wave has traversed the vacuum. In order to do this, the two crystals have to be separated by a gap no wider than the length of the initial acoustic wave.

And the effect scales with frequency. As long as the vacuum gap is scaled accordingly, even ultrasound and hypersound frequencies can tunnel through the vacuum between the two crystals.

Because the phenomenon is analogous to the quantum mechanical effect of tunneling , the results of the research could help scientists study quantum information science, as well as other areas of physics.

“In most cases the effect is small, but we also found situations where the full energy of the wave jumps across the vacuum with 100 percent efficiency, without any reflections,” Maasilta says .

“As such, the phenomenon could find applications in microelectromechanical components (MEMS, smartphone technology) and in the control of heat.”

The research has been published in Communications Physics .

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How Fast Do Radio Waves Travel In A Vacuum-Air-Space

Last Updated: February 1, 2024

The effective use of radio waves in communication technologies today is based on how fast radio waves travel.

Radio waves play a significant role in most of the technology solutions we see around us.

But, as common as they are, very little is known about them. For most people, they don’t even know the meaning of radio waves.

There is a lot of misconception out there regarding radio waves. From what they are to how they function, only a handful of people know anything about this wave type.

As a result, this post will be breaking down everything you need to know about radio waves.

By the time you are done reading this, you should be confident enough to tell someone else exactly what radio waves are and how they function.

What are radio waves?

Unlike what many people think, radio waves are not the sounds you hear coming out of your radio speakers. That is sound waves, not radio waves.

Radio waves are electromagnetic radiation. Radio waves are quite similar to light waves. The only difference is that you cannot see them as light.

Think of them as being produced by charged particles going through acceleration, like in time-changing electric currents.

Transmitters artificially generate them. You need a radio receiver to intercept and receive the radio waves with the help of an antenna.

The application of radio waves is used in many technologies.

They are employed in mobile and fixed radio communication, radar & navigation systems, broadcasting, wireless computer network, communication satellites, and a host of others.

Radio waves were discovered by James Clerk Maxwell, the physicist who was known for the famous Maxwell’s Equation around the 1870s.

A German physicist known as Heinrich Hertz was the one who advanced Maxwell’s prediction of radio waves.

He was the first to apply Maxwell’s equation to the transmission and reception of radio waves.

The unit of frequency for EM waves was unanimously agreed to be Hertz by the American Association For The Advancement of Science, in honor of Heinrich Hertz.

Properties of radio waves

Radio waves have got some highly distinct properties that you ought to be aware of. Those properties will be outlined below

• They are a form of electromagnetic waves. They have got a wavelength longer than the wavelength of infrared light.
• Radio waves can go through materials or obstacles.
• They can travel extremely long distances.
• Radio waves are invisible and cannot be felt either.
• When they move through a vacuum, they do so at the speed of light. But, their speed drops when they move through a medium, depending on the medium’s permeability.
• Radio waves have a wavelength range between thousands of meters and 30cm.
• Radio waves can be formed as a result of changing electric currents. Naturally, they can be emitted by lightning and astronomical objects that can exhibit magnetic field changes.
• Radio waves possess both magnetic and electric components
• They can experience absorption, refraction, reflection, as well as polarization.

Types of Radio Wave

Radio waves are subdivided into various categories. This section of this post will be discussing the different radio waves, as seen below.

Low to medium frequencies

This frequency range is the first category in the radio frequency spectrum. It is composed of extremely low to medium radio waves.

ELF and VLF stand for extremely low frequency and very low frequency, respectively. This class of radio waves operates with a frequency of between 0.1 and 30 kHz.

They are classified as the lowest radio frequencies. They’ve got long-range capabilities that make them suitable for communication items in submarines.

That is because they can penetrate water and rocks. They have also found useful applications in caves and mines.

Higher frequencies

HF, VHF, and UHF bands comprise public service radio, broadcast television sound, cellphones, FM, and GPS.

These bands employ FM or frequency modulation to impress or encode a data or audio signal upon the carrier wave.

In FM, the signal’s amplitude is kept constant, while the frequency is varied along with the magnitude and rate that corresponds to the data or audio signal.

That is why the signal quality of FM is better than that of AM. Environmental factors do not have a similar influence on frequency as they do on amplitude.

Furthermore, the FM receivers are built to ignore any amplitude variations so long as the signal maintains the least threshold value.

Shortwave radio

Shortwave radio makes use of frequencies between 1.7 kHz and 30 MHz.

This frequency range is what is used to transmit radio signals from shortwave stations across the globe.

Stations like the BBC, VOA, Voice of Russia, and hundreds of other stations use this frequency range for broadcast purposes.

Shortwaves are preferred for long-distance broadcast due to their signals’ ability to reflect on the ionosphere and rebound back far away from where the signal has been broadcast.

Highest frequencies

Super high frequency (SHF) and extremely high frequency (EHF) are considered among the microwave band of the radio-frequency spectrum.

With the help of this frequency range, high-bandwidth, short-range communications can happen between fixed locations.

SHF is used in applications such as Wi-Fi, wireless USB, and Bluetooth. They are also employed for radar purposes because they possess the ability to bounce off obstacles.

It is noteworthy that SHF can only function in straight paths. They bounce off any obstacle they come in contact with.

How Fast Do Radio Waves Travel? Through Space, Air or Vacuum

How fast do radio waves travel has been answered so many times, yet some people are still confused about the subject.

Earlier, we were able to establish that radio waves are electromagnetic. That means they are going to behave like electromagnetic waves too.

One thing that is common to all electromagnetic waves is that they all travel at the speed of light in a vacuum. They travel at an approximate speed of 186,000 miles per second in a vacuum.

Unlike radio waves, sound waves cannot travel through a vacuum. They can only travel through a medium.

In other words, without a medium, you cannot have sound. Radio waves do not necessarily need any medium for their propagation.

Radio waves travel at the same speed as light because they are like light waves, except that they are unseen.

Radio waves can equally travel through various mediums at different speeds. How fast they are going to travel through a specific medium will be determined by some factors.

Some of those factors include the permittivity and permeability of the medium in question.

Radio waves are much faster than sound waves, even if you have to pass them through the same medium for the sake of comparison.

How do radio waves work?

The best way to answer how do radio waves work is by using antennas to explain the concept.

For radio waves to be effectively broadcast and received, we will need two antennas. One will be the transmitter, while the other will be the receiver.

Let’s use a radio station as an example. At the radio station, voice can be captured by a mic, where the system will convert it into a form of electrical energy.

That electricity is then sent through an antenna (transmitter) with great height. The transmitter will boost the power of the electricity so it can travel as far as possible.

The tiny particles within the electric current continuously move back and forth within the antenna, and radio waves are automatically produced.

The radio waves then travel at the speed of light or close to that value, with the voices trapped within them.

Therefore, when someone puts on their radio set, the electrons in their antenna are made to move back and forth (vibrated) by the incoming radio waves.

That resonating action brings about an electric current. The electronics component then converts that electric signal to sound, allowing you to hear the voice recorded at the station.

Why do radio waves travel at the speed of light and not sound?

Sound waves need a medium before they can travel between locations.

For example, let’s take the air; sound waves can travel through the air because it is composed of molecules.

Without any molecules in the air, it will be impossible to transmit sound waves across the atmosphere. That is where radio waves differ from sound waves.

Radio waves travel at the speed of light because both light and radio waves belong to electromagnetic waves.

Sound waves do not belong to this class. Instead, they are grouped in the class of mechanical waves.

All electromagnetic waves can travel through a vacuum at the speed of light. So that is the simple reason radio waves tend to travel at the speed of light and not sound waves.

FAQs Regarding The Speed of Radio Waves

Do all the different types of radio waves travel at the same speed.

The radio frequency spectrum is a composition of the different types of radio waves.

But because the radio waves are a part of an electromagnetic spectrum, they will all travel at the same speed across a vacuum.

That speed is the speed of light. Having said that, if they are to travel across different mediums, then their speeds will vary.

Do radio waves continue in outer space?

Yes, radio waves continue indefinitely until they come in contact with something.

But, even before that happens, they usually become weak and blend with the universe’s background noise.

That means the first set of radio waves emitted into outer space must be over a hundred light-years old by now.

What is the speed of red light in a vacuum?

Light travels through a vacuum at a constant speed. The speed at which light travels through a vacuum has nothing to do with its polarization, frequency, or other light wave characteristics.

In other words, the color of the wave does not affect its speed in a vacuum. Whether it is blue or red light, it will travel at an approximate speed of 300,000 km per second.

Does Wi-Fi make use of radio waves?

Just like other wireless devices, Wi-Fi implements radio frequencies for sending signals between devices.

The range of radio frequencies employed by Wi-Fi is quite different from devices like cell phones, car radios, weather radios, or walky-talkies.

For instance, your car radio receives frequencies in the range of between Kilohertz and Megahertz, suitable for AM and FM stations, respectively.

Wi-Fi, on the other hand, implements its data transmission in the region of Gigahertz. So, in general, you can say that Wi-Fi uses radio waves for transmitting data between devices.

What are some of the uses of radio waves?

Radio waves possess the longest wavelengths in the EM spectrum. Radio waves aren’t just used for transmitting radio signals that your radio can pick up.

They are actively responsible for carrying the signals you use for your cell phones and TV.

The moment your TV antenna picks up an incoming signal from a TV station, it does that in the form of radio waves or EM waves.

Are radio waves the only type of electromagnetic wave?

The answer to this question is No! Radio waves are not the only component of the electromagnetic spectrum.

Other forms of electromagnetic waves include Bluetooth, radar, microwaves, ultraviolet light waves, infra-red, and X-rays.

So it is right for you to assume all these components as electromagnetic waves.

Waves are generally classified into two groups – mechanical waves and electromagnetic waves.

Radio waves belong to the group of the latter. That explains the reason behind their ability to travel through a vacuum.

In stark contrast, sound waves are unable to travel through a vacuum due to their mechanical properties.

Sound waves require a medium for them to be propagated from one point to another.

Radio waves, just like other electromagnetic waves, travel through a vacuum at the speed of light.

Radio waves are employed in a wide range of technology applications. They make up the very core of communication technology.

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Can radio waves travel in a vacuum?

Electromagnetic waves: electromagnetic(em) waves can travel through a vacuum. em waves do not require a medium to propagate. since radio waves are electromagnetic waves, so they can pass through a vacuum..

1. Sound wave comprises of a series of compressions and rarefactions.

Can Humans Hear Sound in Space?

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Is it possible to hear sounds in space? The short answer is "No." Yet, misconceptions about sound in space continue to exist, mostly due to the sound effects used in sci-fi movies and TV shows. How many times have we "heard" the starship Enterprise or the Millennium Falcon whoosh through space? It's so ingrained our ideas about space that people are often surprised to find out that it doesn't work that way. The laws of physics explain that it can't happen, but often enough producers don't really think about them. They're going for "effect."

Plus, it's not just a problem in TV or movies. There are mistaken ideas out there that planets make sounds , for example. What's really happening is that specific processes in their atmospheres (or rings) are sending out emissions that can be picked up by sensitive instruments. In order to understand them, scientists take the emissions and "heterodyne" them (that is, process them) to create something we can "hear" so they can try to analyze what they are. But, the planets themselves aren't making sounds.

The Physics of Sound

It is helpful to understand the physics of sound. Sound travels through the air as waves. When we speak, for example, the vibration of our vocal cords compresses the air around them. The compressed air moves the air around it, which carries the sound waves. Eventually, these compressions reach the ears of a listener, whose brain interprets that activity as sound. If the compressions are high frequency and moving fast, the signal received by the ears is interpreted by the brain as a whistle or a shriek. If they're lower frequency and moving more slowly, the brain interprets it as a drum or a boom or a low voice.

Here's the important thing to remember: without anything to compress, sound waves can't be transmitted. And, guess what? There's no "medium" in the vacuum of space itself that transmits sound waves. There is a chance that sound waves can move through and compress clouds of gas and dust, but we wouldn't be able to hear that sound. It would be too low or too high for our ears to perceive. Of course, if someone were in space without any protection against the vacuum, hearing any sound waves would be the least of their problems. 

Light waves (that aren't radio waves) are different. They do not require the existence of a medium in order to propagate. So light can travel through the vacuum of space unimpeded. This is why we can see distant objects like planets , stars , and galaxies . But, we can't hear any sounds they might make. Our ears are what pick up sound waves, and for a variety of reasons, our unprotected ears aren't going to be in space.

Haven't Probes Picked Up Sounds From the Planets?

This is a bit of a tricky one. NASA, back in the early 90s, released a five-volume set of space sounds. Unfortunately, they were not too specific about how the sounds were made exactly. It turns out the recordings weren't actually of sound coming from those planets. What was picked up were interactions of charged particles in the magnetospheres of the planets; trapped radio waves and other electromagnetic disturbances. Astronomers then took these measurements and converted them into sounds. It is similar to the way that a radio captures the radio waves (which are long-wavelength light waves) from radio stations and converts those signals into sound.

Why Apollo Astronauts Report Sounds Near the Moon

This one is truly strange. According to NASA transcripts of the Apollo moon missions, several of the astronauts reported hearing "music" when orbiting the Moon . It turns out that what they heard was entirely predictable radio frequency interference between the lunar module and the command modules.

The most prominent example of this sound was when the Apollo 15 astronauts were on the far side of the Moon. However, once the orbiting craft was over the near side of the Moon, the warbling stopped. Anyone who has ever played with a radio or done HAM radio or other experiments with radio frequencies would recognize the sounds at once. They were nothing abnormal and they certainly didn't propagate through the vacuum of space. 

Why Movies Have Spacecrafts Making Sounds

Since we know that no one can physically hear sounds in the vacuum of space, the best explanation for sound effects in TV and movies is this: if producers didn't make the rockets roar and the spacecraft go "whoosh", the soundtrack would be boring. And, that's true. It doesn't mean there's sound in space. All it means is that sounds are added to give the scenes a little drama. That's perfectly fine as long as people understand it doesn't happen in reality. 

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Inside the quest to map the universe with mysterious bursts of radio energy

Astronomers still don’t know what causes fast radio bursts, but they’re starting to use them to illuminate the space between galaxies.

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When our universe was less than half as old as it is today, a burst of energy that could cook a sun’s worth of popcorn shot out from somewhere amid a compact group of galaxies. Some 8 billion years later, radio waves from that burst reached Earth and were captured by a sophisticated low-frequency radio telescope in the Australian outback. 

The signal, which arrived on June 10, 2022, and lasted for under half a millisecond, is one of a growing class of mysterious radio signals called fast radio bursts. In the last 10 years, astronomers have picked up nearly 5,000 of them. This one was particularly special: nearly double the age of anything previously observed, and three and a half times more energetic. 

But like the others that came before, it was otherwise a mystery. No one knows what causes fast radio bursts. They flash in a seemingly random and unpredictable pattern from all over the sky. Some appear from within our galaxy , others from previously unexamined depths of the universe. Some repeat in cyclical patterns for days at a time and then vanish; others have been consistently repeating every few days since we first identified them. Most never repeat at all. 

Despite the mystery, these radio waves are starting to prove extraordinarily useful. By the time our telescopes detect them, they have passed through clouds of hot, rippling plasma, through gas so diffuse that particles barely touch each other, and through our own Milky Way. And every time they hit the free electrons floating in all that stuff, the waves shift a little bit. The ones that reach our telescopes carry with them a smeary fingerprint of all the ordinary matter they’ve encountered between wherever they came from and where we are now. 

This makes fast radio bursts, or FRBs, invaluable tools for scientific discovery—especially for astronomers interested in the very diffuse gas and dust floating between galaxies, which we know very little about. 

“We don’t know what they are, and we don’t know what causes them. But it doesn’t matter. This is the tool we would have constructed and developed if we had the chance to be playing God and create the universe,” says Stuart Ryder, an astronomer at Macquarie University in Sydney and the lead author of the Science paper that reported the record-breaking burst. 

Many astronomers now feel confident that finding more such distant FRBs will enable them to create the most detailed three-dimensional cosmological map ever made—what Ryder likens to a CT scan of the universe. Even just five years ago making such a map might have seemed an intractable technical challenge: spotting an FFB and then recording enough data to determine where it came from is extraordinarily difficult because most of that work must happen in the few milliseconds before the burst passes.

But that challenge is about to be obliterated. By the end of this decade, a new generation of radio telescopes and related technologies coming online in Australia, Canada, Chile, California, and elsewhere should transform the effort to find FRBs—and help unpack what they can tell us. What was once a series of serendipitous discoveries will become something that’s almost routine. Not only will astronomers be able to build out that new map of the universe, but they’ll have the chance to vastly improve our understanding of how galaxies are born and how they change over time. 

Where’s the matter?

In 1998, astronomers counted up the weight of all of the identified matter in the universe and got a puzzling result. 

We know that about 5% of the total weight of the universe is made up of baryons like protons and neutrons— the particles that make up atoms, or all the “stuff” in the universe. (The other 95% includes dark energy and dark matter.) But the astronomers managed to locate only about 2.5%, not 5%, of the universe’s total. “They counted the stars, black holes, white dwarfs, exotic objects, the atomic gas, the molecular gas in galaxies, the hot plasma, etc. They added it all up and wound up at least a factor of two short of what it should have been,” says Xavier Prochaska, an astrophysicist at the University of California, Santa Cruz, and an expert in analyzing the light in the early universe. “It’s embarrassing. We’re not actively observing half of the matter in the universe.” 

All those missing baryons were a serious problem for simulations of how galaxies form, how our universe is structured, and what happens as it continues to expand. 

Astronomers began to speculate that the missing matter exists in extremely diffuse clouds of what’s known as the warm–hot intergalactic medium, or WHIM. Theoretically, the WHIM would contain all that unobserved material. After the 1998 paper was published, Prochaska committed himself to finding it. 

But nearly 10 years of his life and about $50 million in taxpayer money later, the hunt was going very poorly.

That search had focused largely on picking apart the light from distant galactic nuclei and studying x-ray emissions from tendrils of gas connecting galaxies. The breakthrough came in 2007, when Prochaska was sitting on a couch in a meeting room at the University of California, Santa Cruz, reviewing new research papers with his colleagues. There, amid the stacks of research, sat the paper reporting the discovery of the first FRB.

Duncan Lorimer and David Narkevic, astronomers at West Virginia University, had discovered a recording of an energetic radio wave unlike anything previously observed. The wave lasted for less than five milliseconds, and its spectral lines were very smeared and distorted, unusual characteristics for a radio pulse that was also brighter and more energetic than other known transient phenomena. The researchers concluded that the wave could not have come from within our galaxy, meaning that it had traveled some unknown distance through the universe. 

Here was a signal that had traversed long distances of space, been shaped and affected by electrons along the way, and had enough energy to be clearly detectable despite all the stuff it had passed through. There are no other signals we can currently detect that commonly occur throughout the universe and have this exact set of traits.

“I saw that and I said, ‘Holy cow—that’s how we can solve the missing-baryons problem,’” Prochaska says. Astronomers had used a similar technique with the light from pulsars— spinning neutron stars that beam radiation from their poles—to count electrons in the Milky Way. But pulsars are too dim to illuminate more of the universe. FRBs were thousands of times brighter, offering a way to use that technique to study space well beyond our galaxy.

There’s a catch, though: in order for an FRB to be an indicator of what lies in the seemingly empty space between galaxies, researchers have to know where it comes from. If you don’t know how far the FRB has traveled, you can’t make any definitive estimate of what space looks like between its origin point and Earth. 

Astronomers couldn’t even point to the direction that the first 2007 FRB came from, let alone calculate the distance it had traveled. It was detected by an enormous single-dish radio telescope at the Parkes Observatory (now called the Murriyang ) in New South Wales, which is great at picking up incoming radio waves but can pinpoint FRBs only to an area of the sky as large as Earth’s full moon. For the next decade, telescopes continued to identify FRBs without providing a precise origin, making them a fascinating mystery but not practically useful.

Then, in 2015, one particular radio wave flashed—and then flashed again. Over the course of two months of observation from the Arecibo telescope in Puerto Rico, the radio waves came again and again, flashing 10 times. This was the first repeating burst of FRBs ever observed (a mystery in its own right), and now researchers had a chance to determine where the radio waves had begun, using the opportunity to home in on its location.

In 2017, that’s what happened. The researchers obtained an accurate position for the fast radio burst using the NRAO Very Large Array telescope in central New Mexico. Armed with that position, the researchers then used the Gemini optical telescope in Hawaii to take a picture of the location, revealing the galaxy where the FRB had begun and how far it had traveled. “That’s when it became clear that at least some of these we’d get the distance for. That’s when I got really involved and started writing telescope proposals,” Prochaska says. 

That same year, astronomers from across the globe gathered in Aspen, Colorado, to discuss the potential for studying FRBs. Researchers debated what caused them. Neutron stars? Magnetars, neutron stars with such powerful magnetic fields that they emit x-rays and gamma rays? Merging galaxies? Aliens? Did repeating FRBs and one-offs have different origins, or could there be some other explanation for why some bursts repeat and most do not? Did it even matter, since all the bursts could be used as probes regardless of what caused them? At that Aspen meeting, Prochaska met with a team of radio astronomers based in Australia, including Keith Bannister, a telescope expert involved in the early work to build a precursor facility for the Square Kilometer Array, an international collaboration to build the largest radio telescope arrays in the world. 

The construction of that precursor telescope, called ASKAP, was still underway during that meeting. But Bannister, a telescope expert at the Australian government’s scientific research agency, CSIRO, believed that it could be requisitioned and adapted to simultaneously locate and observe FRBs. 

Bannister and the other radio experts affiliated with ASKAP understood how to manipulate radio telescopes for the unique demands of FRB hunting; Prochaska was an expert in everything “not radio.” They agreed to work together to identify and locate one-off FRBs (because there are many more of these than there are repeating ones) and then use the data to address the problem of the missing baryons. 

And over the course of the next five years, that’s exactly what they did—with astonishing success.

Building a pipeline

To pinpoint a burst in the sky, you need a telescope with two things that have traditionally been at odds in radio astronomy: a very large field of view and high resolution. The large field of view gives you the greatest possible chance to detect a fleeting, unpredictable burst. High resolution  lets you determine where that burst actually sits in your field of view. 

ASKAP was the perfect candidate for the job. Located in the westernmost part of the Australian outback, where cattle and sheep graze on public land and people are few and far between, the telescope consists of 36 dishes, each with a large field of view. These dishes are separated by large distances, allowing observations to be combined through a technique called interferometry so that a small patch of the sky can be viewed with high precision.  

The dishes weren’t formally in use yet, but Bannister had an idea. He took them and jerry-rigged a “fly’s eye” telescope, pointing the dishes at different parts of the sky to maximize its ability to spot something that might flash anywhere. 

“Suddenly, it felt like we were living in paradise,” Bannister says. “There had only ever been three or four FRB detections at this point, and people weren’t entirely sure if [FRBs] were real or not, and we were finding them every two weeks.” 

When ASKAP’s interferometer went online in September 2018, the real work began. Bannister designed a piece of software that he likens to live-action replay of the FRB event. “This thing comes by and smacks into your telescope and disappears, and you’ve got a millisecond to get its phone number,” he says. To do so, the software detects the presence of an FRB within a hundredth of a second and then reaches upstream to create a recording of the telescope’s data before the system overwrites it. Data from all the dishes can be processed and combined to reconstruct a view of the sky and find a precise point of origin. 

The team can then send the coordinates on to optical telescopes, which can take detailed pictures of the spot to confirm the presence of a galaxy—the likely origin point of the FRB. 

Ryder’s team used data on the galaxy’s spectrum, gathered from the European Southern Observatory, to measure how much its light stretched as it traversed space to reach our telescopes. This “redshift” becomes a proxy for distance, allowing astronomers to estimate just how much space the FRB’s light has passed through. 

In 2018, the live-action replay worked for the first time, making Bannister, Ryder, Prochaska, and the rest of their research team the first to localize an FRB that was not repeating. By the following year, the team had localized about five of them. By 2020, they had published a paper in Nature declaring that the FRBs had let them count up the universe’s missing baryons. 

The centerpiece of the paper’s argument was something called the dispersion measure—a number that reflects how much an FRB’s light has been smeared by all the free electrons along our line of sight. In general, the farther an FRB travels, the higher the dispersion measure should be. Armed with both the travel distance (the redshift) and the dispersion measure for a number of FRBs, the researchers found they could extrapolate the total density of particles in the universe. J-P Macquart, the paper’s lead author, believed that the relationship between dispersion measure and FRB distance was predictable and could be applied to map the universe.

As a leader in the field and a key player in the advancement of FRB research, Macquart would have been interviewed for this piece. But he died of a heart attack one week after the paper was published, at the age of 45 . FRB researchers began to call the relationship between dispersion and distance the “Macquart relation,” in honor of his memory and his push for the groundbreaking idea that FRBs could be used for cosmology. 

Proving that the Macquart relation would hold at greater distances became not just a scientific quest but also an emotional one. 

“I remember thinking that I know something about the universe that no one else knows.”

The researchers knew that the ASKAP telescope was capable of detecting bursts from very far away—they just needed to find one. Whenever the telescope detected an FRB, Ryder was tasked with helping to determine where it had originated. It took much longer than he would have liked. But one morning in July 2022, after many months of frustration, Ryder downloaded the newest data email from the European Southern Observatory and began to scroll through the spectrum data. Scrolling, scrolling, scrolling—and then there it was: light from 8 billion years ago, or a redshift of one, symbolized by two very close, bright lines on the computer screen, showing the optical emissions from oxygen. “I remember thinking that I know something about the universe that no one else knows,” he says. “I wanted to jump onto a Slack and tell everyone, but then I thought: No, just sit here and revel in this. It has taken a lot to get to this point.” 

With the October 2023 Science paper, the team had basically doubled the distance baseline for the Macquart relation, honoring Macquart’s memory in the best way they knew how. The distance jump was significant because Ryder and the others on his team wanted to confirm that their work would hold true even for FRBs whose light comes from so far away that it reflects a much younger universe. They also wanted to establish that it was possible to find FRBs at this redshift, because astronomers need to collect evidence about many more like this one in order to create the cosmological map that motivates so much FRB research.

“It’s encouraging that the Macquart relation does still seem to hold, and that we can still see fast radio bursts coming from those distances,” Ryder said. “We assume that there are many more out there.” 

Mapping the cosmic web

The missing stuff that lies between galaxies, which should contain the majority of the matter in the universe, is often called the cosmic web. The diffuse gases aren’t floating like random clouds; they’re strung together more like a spiderweb, a complex weaving of delicate filaments that stretches as the galaxies at their nodes grow and shift. This gas probably escaped from galaxies into the space beyond when the galaxies first formed, shoved outward by massive explosions.

“We don’t understand how gas is pushed in and out of galaxies. It’s fundamental for understanding how galaxies form and evolve,” says Kiyoshi Masui, the director of MIT’s Synoptic Radio Lab. “We only exist because stars exist, and yet this process of building up the building blocks of the universe is poorly understood … Our ability to model that is the gaping hole in our understanding of how the universe works.” 

Astronomers are also working to build large-scale maps of galaxies in order to precisely measure the expansion of the universe. But the cosmological modeling underway with FRBs should create a picture of invisible gasses between galaxies, one that currently does not exist. To build a three-dimensional map of this cosmic web, astronomers will need precise data on thousands of FRBs from regions near Earth and from very far away, like the FRB at redshift one. “Ultimately, fast radio bursts will give you a very detailed picture of how gas gets pushed around,” Masui says. “To get to the cosmological data, samples have to get bigger, but not a lot bigger.” 

That’s the task at hand for Masui, who leads a team searching for FRBs much closer to our galaxy than the ones found by the Australian-led collaboration. Masui’s team conducts FRB research with the CHIME telescope in British Columbia, a nontraditional radio telescope with a very wide field of view and focusing reflectors that look like half-pipes instead of dishes. CHIME (short for “Canadian Hydrogen Intensity Mapping Experiment)” has no moving parts and is less reliant on mirrors than a traditional telescope (focusing light in only one direction rather than two), instead using digital techniques to process its data. CHIME can use its digital technology to focus on many places at once, creating a 200-square-degree field of view compared with ASKAP’s 30-degree one. Masui likened it to a mirror that can be focused on thousands of different places simultaneously. 

Because of this enormous field of view, CHIME has been able to gather data on thousands of bursts that are closer to the Milky Way. While CHIME cannot yet precisely locate where they are coming from the way that ASKAP can (the telescope is much more compact, providing lower resolution), Masui is leading the effort to change that by building three smaller versions of the same telescope in British Columbia; Green Bank, West Virginia; and Northern California. The additional data provided by these telescopes, the first of which will probably be collected sometime this year, can be combined with data from the original CHIME telescope to produce location information that is about 1,000 times more precise. That should be detailed enough for cosmological mapping.

Telescope technology is improving so fast that the quest to gather enough FRB samples from different parts of the universe for a cosmological map could be finished within the next 10 years. In addition to CHIME, the BURSTT radio telescope in Taiwan should go online this year; the CHORD telescope in Canada, designed to surpass CHIME, should begin operations in 2025; and the Deep Synoptic Array in California could transform the field of radio astronomy when it’s finished, which is expected to happen sometime around the end of the decade. 

And at ASKAP, Bannister is building a new tool that will quintuple the sensitivity of the telescope, beginning this year. If you can imagine stuffing a million people simultaneously watching uncompressed YouTube videos into a box the size of a fridge, that’s probably the easiest way to visualize the data handling capabilities of this new processor, called a field-programmable gate array, which Bannister is almost finished programming. He expects the new device to allow the team to detect one new FRB each day.

With all the telescopes in competition, Bannister says, “in five or 10 years’ time, there will be 1,000 new FRBs detected before you can write a paper about the one you just found ... We’re in a race to make them boring.” 

Prochaska is so confident FRBs will finally give us the cosmological map he’s been working toward his entire life that he’s started studying for a degree in oceanography. Once astronomers have measured distances for 1,000 of the bursts, he plans to give up the work entirely. 

“In a decade, we could have a pretty decent cosmological map that’s very precise,” he says. “That’s what the 1,000 FRBs are for—and I should be fired if we don’t.”

Unlike most scientists, Prochaska can define the end goal. He knows that all those FRBs should allow astronomers to paint a map of the invisible gases in the universe, creating a picture of how galaxies evolve as gases move outward and then fall back in. FRBs will grant us an understanding of the shape of the universe that we don’t have today—even if the mystery of what makes them endures. 

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