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The History of Space Exploration

During the time that has passed since the launching of the first artificial satellite in 1957, astronauts have traveled to the moon, probes have explored the solar system, and instruments in space have discovered thousands of planets around other stars.

Earth Science, Astronomy, Social Studies, U.S. History, World History

Apollo 11 Astronauts on Moon

A less belligerent, but no less competitive, part of the Cold War was the space race. The Soviet Union bested its rival at nearly every turn, until the U.S. beat them to the finish line by landing astronauts on the moon.

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We human beings have been venturing into space since October 4, 1957, when the Union of Soviet Socialist Republics (U.S.S.R.) launched Sputnik, the first artificial satellite to orbit Earth. This happened during the period of political hostility between the Soviet Union and the United States known as the Cold War. For several years, the two superpowers had been competing to develop missiles, called intercontinental ballistic missiles (ICBMs), to carry nuclear weapons between continents. In the U.S.S.R., the rocket designer Sergei Korolev had developed the first ICBM, a rocket called the R7, which would begin the space race. This competition came to a head with the launch of Sputnik . Carried atop an R7 rocket, the Sputnik satellite was able to send out beeps from a radio transmitter. After reaching space, Sputnik orbited Earth once every 96 minutes. The radio beeps could be detected on the ground as the satellite passed overhead, so people all around the world knew that it was really in orbit. Realizing that the U.S.S.R. had capabilities that exceeded U.S. technologies that could endanger Americans, the United States grew worried. Then, a month later, on November 3, 1957, the Soviets achieved an even more impressive space venture. This was Sputnik II, a satellite that carried a living creature, a dog named Laika. Prior to the launch of Sputnik, the United States had been working on its own capability to launch a satellite. The United States made two failed attempts to launch a satellite into space before succeeding with a rocket that carried a satellite called Explorer on January 31, 1958. The team that achieved this first U.S. satellite launch consisted largely of German rocket engineers who had once developed ballistic missiles for Nazi Germany. Working for the U.S. Army at the Redstone Arsenal in Huntsville, Alabama, the German rocket engineers were led by Wernher von Braun and had developed the German V2 rocket into a more powerful rocket, called the Jupiter C, or Juno. Explorer carried several instruments into space for conducting science experiments. One instrument was a Geiger counter for detecting cosmic rays. This was for an experiment operated by researcher James Van Allen, which, together with measurements from later satellites, proved the existence of what are now called the Van Allen radiation belts around Earth. In 1958, space exploration activities in the United States were consolidated into a new government agency, the National Aeronautics and Space Administration (NASA). When it began operations in October of 1958, NASA absorbed what had been called the National Advisory Committee for Aeronautics (NACA), and several other research and military facilities, including the Army Ballistic Missile Agency (the Redstone Arsenal) in Huntsville. The first human in space was the Soviet cosmonaut Yuri Gagarin, who made one orbit around Earth on April 12, 1961, on a flight that lasted 108 minutes. A little more than three weeks later, NASA launched astronaut Alan Shepard into space, not on an orbital flight, but on a suborbital trajectory—a flight that goes into space but does not go all the way around Earth. Shepard’s suborbital flight lasted just over 15 minutes. Three weeks later, on May 25, President John F. Kennedy challenged the United States to an ambitious goal, declaring: “I believe that this nation should commit itself to achieving the goal, before the decade is out, of landing a man on the moon and returning him safely to Earth." In addition to launching the first artificial satellite, the first dog in space, and the first human in space, the Soviet Union achieved other space milestones ahead of the United States. These milestones included Luna 2, which became the first human-made object to hit the Moon in 1959. Soon after that, the U.S.S.R. launched Luna 3 . Less than four months after Gagarin’s flight in 1961, a second Soviet human mission orbited a cosmonaut around Earth for a full day. The U.S.S.R. also achieved the first spacewalk and launched the Vostok 6 mission, which made Valentina Tereshkova the first woman to travel to space. During the 1960s, NASA made progress toward President Kennedy’s goal of landing a human on the moon with a program called Project Gemini, in which astronauts tested technology needed for future flights to the moon, and tested their own ability to endure many days in spaceflight. Project Gemini was followed by Project Apollo, which took astronauts into orbit around the moon and to the lunar surface between 1968 and 1972. In 1969, on Apollo11, the United States sent the first astronauts to the Moon, and Neil Armstrong became the first human to set foot on its surface. During the landed missions, astronauts collected samples of rocks and lunar dust that scientists still study to learn about the moon. During the 1960s and 1970s, NASA also launched a series of space probes called Mariner, which studied Venus, Mars, and Mercury. Space stations marked the next phase of space exploration. The first space station in Earth orbit was the Soviet Salyut 1 station, which was launched in 1971. This was followed by NASA’s Skylab space station, the first orbital laboratory in which astronauts and scientists studied Earth and the effects of spaceflight on the human body. During the 1970s, NASA also carried out Project Viking in which two probes landed on Mars, took numerous photographs, examined the chemistry of the Martian surface environment, and tested the Martian dirt (called regolith ) for the presence of microorganisms . Since the Apollo lunar program ended in 1972, human space exploration has been limited to low-Earth orbit, where many countries participate and conduct research on the International Space Station. However, unpiloted probes have traveled throughout our solar system. In recent years, probes have made a range of discoveries, including that a moon of Jupiter, called Europa, and a moon of Saturn, called Enceladus, have oceans under their surface ice that scientists think may harbor life. Meanwhile, instruments in space, such as the Kepler Space Telescope , and instruments on the ground have discovered thousands of exoplanets , planets orbiting other stars. This era of exoplanet discovery began in 1995, and advanced technology now allows instruments in space to characterize the atmospheres of some of these exoplanets.

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History of Space Travel

Learn about the history of humans traveling into space.

The first earthling to orbit our planet was just two years old, plucked from the streets of Moscow barely more than a week before her historic launch. Her name was Laika. She was a terrier mutt and by all accounts a good dog. Her 1957 flight paved the way for space exploration back when scientists didn’t know if spaceflight was lethal for living things.

Humans are explorers. Since before the dawn of civilization, we’ve been lured over the horizon to find food or more space, to make a profit, or just to see what’s beyond those trees or mountains or oceans. Our ability to explore reached new heights—literally—in the last hundred years. Airplanes shortened distances, simplified travel, and showed us Earth from a new perspective. By the middle of the last century, we aimed even higher.

Our first steps into space began as a race between the United States and the former Soviet Union, rivals in a global struggle for power. Laika was followed into orbit four years later by the first human, Soviet Cosmonaut Yuri A. Gagarin. With Earth orbit achieved, we turned our sights on the moon. The United States landed two astronauts on its stark surface in 1969, and five more manned missions followed. The U.S.’s National Aeronautics and Space Administration (NASA) launched probes to study the solar system. Manned space stations began glittering in the sky. NASA developed reusable spacecraft—space shuttle orbiters—to ferry astronauts and satellites to orbit. Space-travel technology had advanced light-years in just three decades. Gagarin had to parachute from his spaceship after reentry from orbit. The space shuttle leaves orbit at 16,465 miles an hour (26,498 kilometers an hour) and glides to a stop on a runway without using an engine.

Space travel is nothing like in the movies. Getting from A to B requires complex calculations involving inertia and gravity—literally, rocket science—to "slingshot" from planet to planet (or moon) across the solar system. The Voyager mission of the 1970s took advantage of a rare alignment of Jupiter, Saturn, Uranus, and Neptune to shave off nearly 20 years of travel time. Space is also dangerous. More than 20 astronauts have died doing their job.

That hasn’t stopped people from signing up and blasting off. NASA’s shuttle program has ended, but private companies are readying their own space programs. A company called Planetary Resources plans to send robot astronauts to the Asteroid Belt to mine for precious metals. Another company named SpaceX is hoping to land civilian astronauts on Mars—the next human step into the solar system—in 20 years. NASA and other civilian companies are planning their own Mars missions. Maybe you’ll be a member of one? Don’t forget to bring your dog.

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Everything you need to know about space travel (almost)

We're a long way from home...

Paul Parsons

When did we first start exploring space?

The first human-made object to go into space was a German V2 missile , launched on a test flight in 1942. Although uncrewed, it reached an altitude of 189km (117 miles).

Former Nazi rocket scientists were later recruited by both America and Russia (often at gunpoint in the latter case), where they were instrumental in developing Intercontinental Ballistic Missiles (ICBMs) – rockets capable of carrying nuclear weapons from one side of the planet to the other.

It was these super-missiles that formed the basis for the space programmes of both post-war superpowers. As it happened, Russia was the first to reach Earth orbit, when it launched the uncrewed Sputnik 1 in October 1957, followed a month later by Sputnik 2, carrying the dog Laika – the first live animal in space.

The USA sent its first uncrewed satellite, Explorer 1, into orbit soon after, in January 1958. A slew of robotic spaceflights followed, from both sides of the Atlantic, before Russian cosmonaut Yuri Gagarin piloted Vostok 1 into orbit on 12 April 1961, to become the first human being in space . And from there the space race proper began, culminating in Neil Armstrong and Buzz Aldrin becoming the first people to walk on the Moon as part of NASA's Apollo programme .

Why is space travel important?

Space exploration is the future. It satisfies the human urge to explore and to travel, and in the years and decades to come it could even provide our species with new places to call home – especially relevant now, as Earth becomes increasingly crowded .

Extending our reach into space is also necessary for the advancement of science. Space telescopes like the Hubble Space Telescope and probes to the distant worlds of the Solar System are continually updating, and occasionally revolutionising, our understanding of astronomy and physics.

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But there are also some very practical reasons, such as mining asteroids for materials that are extremely rare here on Earth.

One example is the huge reserve of the chemical isotope helium-3 thought to be locked away in the soil on the surface of the Moon . This isotope is a potential fuel for future nuclear fusion reactors – power stations that tap into the same source of energy as the Sun. Unlike other fusion fuels, helium-3 gives off no hard-to-contain and deadly neutron radiation.

However, for this to happen the first challenge to overcome is how to build a base on the Moon. In 2019, China's Chang’e 4 mission marked the beginning of a new space race to conquer the Moon, signalling their intent to build a permanent lunar base , while the NASA Artemis mission plans to build a space station, called Lunar Orbital Platform-Gateway , providing a platform to ferry astronauts to the Moon's surface.

Could humans travel into interstellar space and how would we get there?

It’s entirely feasible that human explorers will visit the furthest reaches of our Solar System. The stars, however, are another matter. Interstellar space is so vast that it takes light – the fastest thing we know of in the Universe – years, centuries and millennia to traverse it. Faster-than-light travel may be possible one day, but is unlikely to become a reality in our lifetimes.

It’s not impossible that humans might one day cross this cosmic gulf, though it won’t be easy. The combustion-powered rocket engines of today certainly aren’t up to the job – they just don’t use fuel efficiently enough. Instead, interstellar spacecraft may create a rocket-like propulsion jet using electric and magnetic fields. This so-called ‘ ion drive ’ technology has already been tested aboard uncrewed Solar System probes.

Another possibility is to push spacecraft off towards the stars using the light from a high-powered laser . A consortium of scientists calling themselves Breakthrough Starshot is already planning to send a flotilla of tiny robotic probes to our nearest star, Proxima Centauri, using just this method.

Though whether human astronauts could survive such punishing acceleration, or the decades-long journey through deep space, remains to be seen.

How do we benefit from space exploration?

Pushing forward the frontiers of science is the stated goal of many space missions . But even the development of space travel technology itself can lead to unintended yet beneficial ‘spin-off’ technologies with some very down-to-earth applications.

Notable spin-offs from the US space programme, NASA, include memory foam mattresses, artificial hearts, and the lubricant spray WD-40. Doubtless, there are many more to come.

Read more about space exploration:

• The next giant leaps: The UK missions getting us to the Moon
• Move over, Mars: why we should look further afield for future human colonies
• Everything you need to know about the Voyager mission
• 6 out-of-this-world experiments recreating space on Earth

Space exploration also instils a sense of wonder, it reminds us that there are issues beyond our humdrum planet and its petty squabbles, and without doubt it helps to inspire each new generation of young scientists. It’s also an insurance policy. We’re now all too aware that global calamities can and do happen – for instance, climate change and the giant asteroid that smashed into the Earth 65 million years ago, leading to the total extinction of the dinosaurs .

The lesson for the human species is that we keep all our eggs in one basket at our peril. On the other hand, a healthy space programme, and the means to travel to other worlds, gives us an out.

Is space travel dangerous?

In short, yes – very. Reaching orbit means accelerating up to around 28,000kph (17,000mph, or 22 times the speed of sound ). If anything goes wrong at that speed, it’s seldom good news.

Then there’s the growing cloud of space junk to contend with in Earth's orbit – defunct satellites, discarded rocket stages and other detritus – all moving just as fast. A five-gram bolt hitting at orbital speed packs as much energy as a 200kg weight dropped from the top of an 18-storey building.

And getting to space is just the start of the danger. The principal hazard once there is cancer-producing radiation – the typical dose from one day in space is equivalent to what you’d receive over an entire year back on Earth, thanks to the planet’s atmosphere and protective magnetic field.

Add to that the icy cold airless vacuum , the need to bring all your own food and water, plus the effects of long-duration weightlessness on bone density, the brain and muscular condition – including that of the heart – and it soon becomes clear that venturing into space really isn’t for the faint-hearted.

When will space travel be available to everyone?

It’s already happening – that is, assuming your pockets are deep enough. The first self-funded ‘space tourist’ was US businessman Dennis Tito, who in 2001 spent a week aboard the International Space Station (ISS) for the cool sum of $20m (£15m).

Virgin Galactic has long been promising to take customers on short sub-orbital hops into space – where passengers get to experience rocket propulsion and several minutes of weightlessness, before gliding back to a runway landing on Earth, all for $250k (£190k). In late July 2020, the company unveiled the finished cabin in its SpaceShipTwo vehicle, suggesting that commercial spaceflights may begin shortly.

Meanwhile, Elon Musk’s SpaceX , which in May 2020 became the first private company to launch a human crew to Earth orbit aboard the Crew Dragon , plans to offer stays on the ISS for $35k (£27k) per night. SpaceX is now prototyping its huge Starship vehicle , which is designed to take 100 passengers from Earth to as far afield as Mars for around $20k (£15k) per head. Musk stated in January that he hoped to be operating 1,000 Starships by 2050.

10 Short Lessons in Space Travel by Paul Parsons is out now (£9.99, Michael O'Mara)

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A Brief History of Space Exploration

Humans have always looked up into the night sky and dreamed about space.

In the latter half of the 20th century, rockets were developed that were powerful enough to overcome the force of gravity to reach orbital velocities, paving the way for space exploration to become a reality.

In the 1930s and 1940s, Nazi Germany saw the possibilities of using long-distance rockets as weapons. Late in World War II, London was attacked by 200-mile-range V-2 missiles, which arched 60 miles high over the English Channel at more than 3,500 miles per hour. After World War II, the United States and the Soviet Union created their own missile programs.

On Oct. 4, 1957, the Soviets launched the first artificial satellite, Sputnik 1, into space. Four years later on April 12, 1961, Russian Lt. Yuri Gagarin became the first human to orbit Earth in Vostok 1. His flight lasted 108 minutes, and Gagarin reached an altitude of 327 kilometers (about 202 miles).

The first U.S. satellite, Explorer 1, went into orbit on Jan. 31, 1958. In 1961, Alan Shepard became the first American to fly into space. On Feb. 20, 1962, John Glenn’s historic flight made him the first American to orbit Earth.

Landing On The Moon

“Landing a man on the Moon and returning him safely to Earth within a decade” was a national goal set by President John F. Kennedy in 1961. On July 20, 1969, astronaut Neil Armstrong took “one giant leap for mankind” as he stepped onto the Moon. Six Apollo missions were made to explore the Moon between 1969 and 1972.

During the 1960s, unmanned spacecraft photographed and probed the Moon before astronauts ever landed. By the early 1970s, orbiting communications and navigation satellites were in everyday use, and the Mariner spacecraft was orbiting and mapping the surface of Mars. By the end of the decade, the Voyager spacecraft had sent back detailed images of Jupiter and Saturn, their rings, and their moons.

Skylab, America’s first space station, was a human-spaceflight highlight of the 1970s, as was the Apollo Soyuz Test Project, the world’s first internationally crewed (American and Russian) space mission.

In the 1980s, satellite communications expanded to carry television programs, and people were able to pick up the satellite signals on their home dish antennas. Satellites discovered an ozone hole over Antarctica, pinpointed forest fires, and gave us photographs of the nuclear power plant disaster at Chernobyl in 1986. Astronomical satellites found new stars and gave us a new view of the center of our galaxy.

Space Shuttle

In April 1981, the launch of the space shuttle Columbia ushered in a period of reliance on the reusable shuttle for most civilian and military space missions. Twenty-four successful shuttle launches fulfilled many scientific and military requirements until Jan. 28,1986, when just 73 seconds after liftoff, the space shuttle Challenger exploded. The crew of seven was killed, including Christa McAuliffe, a teacher from New Hampshire who would have been the first civilian in space.

The Columbia disaster was the second shuttle tragedy. On Feb. 1, 2003, the shuttle broke apart while reentering the Earth’s atmosphere, killing all seven crew members. The disaster occurred over Texas, and only minutes before it was scheduled to land at the Kennedy Space Center. An investigation determined the catastrophe was caused by a piece of foam insulation that broke off the shuttle’s propellant tank and damaged the edge of the shuttle’s left wing. It was the second loss of a shuttle in 113 shuttle flights. After each of the disasters, space shuttle flight operations were suspended for more than two years.

Discovery was the first of the three active space shuttles to be retired, completing its final mission on March 9, 2011; Endeavour did so on June 1. The final shuttle mission was completed with the landing of Atlantis on July 21, 2011, closing the 30-year space shuttle program.

The Gulf War proved the value of satellites in modern conflicts. During this war, allied forces were able to use their control of the “high ground” of space to achieve a decisive advantage. Satellites were used to provide information on enemy troop formations and movements, early warning of enemy missile attacks, and precise navigation in the featureless desert terrain. The advantages of satellites allowed the coalition forces to quickly bring the war to a conclusion, saving many lives.

Space systems continue to become more and more integral to homeland defense, weather surveillance, communication, navigation, imaging, and remote sensing for chemicals, fires, and other disasters.

International Space Station

The International Space Station is a research laboratory in low Earth orbit. With many different partners contributing to its design and construction, this high-flying laboratory has become a symbol of cooperation in space exploration, with former competitors now working together.

The station has been continuously occupied since the arrival of Expedition 1 in November of 2000. The station is serviced by a variety of visiting spacecraft: the Russian Soyuz and Progress; the American Dragon and Cygnus; the Japanese H-II Transfer Vehicle; and formerly the Space Shuttle and the European Automated Transfer Vehicle. It has been visited by astronauts, cosmonauts, and space tourists from 17 different nations.  

Space launch systems have been designed to reduce costs and improve dependability, safety, and reliability. Most U.S. military and scientific satellites are launched into orbit by a family of expendable launch vehicles designed for a variety of missions. Other nations have their own launch systems, and there is strong competition in the commercial launch market to develop the next generation of launch systems.

The Future Of Space Exploration

Modern space exploration is reaching areas once only dreamed about. Mars is focal point of modern space exploration, and manned Mars exploration is a long-term goal of the

United States. NASA is on a journey to Mars, with a goal of sending humans to the Red Planet in the 2030s. 

NASA and its partners have sent orbiters, landers, and rovers, increasing our knowledge about the planet. The Curiosity Rover has gathered radiation data to protect astronauts, and the MARS 2020 Rover will study the availability of oxygen and other Martian resources.

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An Introduction to Space Exploration

While the observation of objects in space, known as astronomy, predates reliable recorded history, it was the development of large and relatively efficient rockets during the early 20th century that allowed physical space exploration to become a reality. Common rationales for exploring space include advancing scientific research, uniting different nations, ensuring the future survival of humanity and developing military and strategic advantages against other countries.

Space exploration has often been used as a proxy competition for geopolitical rivalries such as the Cold War. The early era of space exploration was driven by a “Space Race” between the Soviet Union and the United States, the launch of the first man-made object to orbit the Earth, the USSR’s Sputnik 1, on 4 October 1957, and the first Moon landing by the American Apollo 11 craft on 20 July 1969 are often taken as landmarks for this initial period. The Soviet space program achieved many of the first milestones, including the first living being in orbit in 1957, the first human spaceflight (Yuri Gagarin aboard Vostok 1) in 1961, the first spacewalk (by Aleksei Leonov) on 18 March 1965, the first automatic landing on another celestial body in 1966, and the launch of the first space station (Salyut 1) in 1971.

After the first 20 years of exploration, focus shifted from one-off flights to renewable hardware, such as the Space Shuttle program, and from competition to cooperation as with the International Space Station (ISS).

With the substantial completion of the ISS following STS-133 in March 2011, plans for space exploration by the USA remain in flux. Constellation, a Bush Administration program for a return to the Moon by 2020 was judged inadequately funded and unrealistic by an expert review panel reporting in 2009. The Obama Administration proposed a revision of Constellation in 2010 to focus on the development of the capability for crewed missions beyond low earth orbit (LEO), envisioning extending the operation of the ISS beyond 2020, transferring the development of launch vehicles for human crews from NASA to the private sector, and developing technology to enable missions to beyond LEO, such as Earth/Moon L1, the Moon, Earth/Sun L2, near-earth asteroids, and Phobos or Mars orbit. As of March 2011, the US Senate and House of Representatives are still working towards a compromise NASA funding bill, which will probably terminate Constellation and fund development of a heavy lift launch vehicle (HLLV).

In the 2000s, the People’s Republic of China initiated a successful manned spaceflight program, while the European Union, Japan, and India have also planned future manned space missions. China, Russia, Japan, and India have advocated manned missions to the Moon during the 21st century, while the European Union has advocated manned missions to both the Moon and Mars during the 21st century.

From the 1990s onwards, private interests began promoting space tourism and then private space exploration of the Moon (see Google Lunar X Prize).

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We often refer to our expanding universe with one simple word: space. But where does space begin and, more importantly, what is it?

Space is an almost perfect vacuum, nearly void of matter and with extremely low pressure. In space, sound doesn't carry because there aren't molecules close enough together to transmit sound between them. Not quite empty, bits of gas, dust and other matter floats around "emptier" areas of the universe, while more crowded regions can host planets, stars and galaxies.

From our Earth -bound perspective, outer space is most often thought to begin about 62 miles (100 kilometers) above sea level at what is known as the Kármán line . This is an imaginary boundary at an altitude where there is no appreciable air to breathe or scatter light. Passing this altitude, blue starts to give way to black because oxygen molecules are not in enough abundance to make the sky blue.

Related: Where DOES Space Begin? Virgin Galactic Flies Right into the Debate

No one knows exactly how big space is. It's difficult to determine because of what we can see in our detectors. We measure long distances in space in "light-years," representing the distance it takes for light to travel in a year (roughly 5.8 trillion miles (9.3 trillion kilometers)). 

From the light that is visible in our telescopes, we have charted galaxies reaching almost as far back as the Big Bang, which is thought to have started our universe about 13.8 billion years ago. This means we can "see" into space at a distance of almost 13.8 billion light-years. But the universe continues to expand, making "measuring space," even more challenging. 

Additionally, astronomers are not totally sure if our universe is the only one that exists . This means that space could be a whole lot bigger than we even think.

Space radiation invisible to human eyes

The majority of space is relatively empty, with just stray bits of dust and gas floating around. This means that when humans send a probe to a distant planet or asteroid, the craft will not encounter "drag" in the same way that an airplane does as it sails through space.

In fact, the vacuum environment in space and on the moon, is one reason why the lunar lander of the Apollo program was designed to have an almost spider-like appearance , as it was described by the Apollo 9 crew. Because the spacecraft was designed to work in a zone with no atmosphere, it didn't need to have smooth edges or an aerodynamic shape.

In addition to the bits of debris that speckle the "emptier" regions of space, research has shown that these areas are also home to different forms of radiation. In our own solar system, the solar wind — charged particles that stream from the sun — emanate throughout the solar system and occasionally cause auroras near Earth's poles. Cosmic rays also fly through our neighborhood, stemming from supernovas outside of the solar system.

In fact, the universe as a whole is inundated with what is known as the cosmic microwave background (CMB), which is essentially the leftover radiation from the explosion mostly commonly known as the Big Bang. The CMB is the oldest radiation that our instruments can detect. 

Infographic: Cosmic Microwave Background Explained

There remain two giant mysteries about space: dark matter and dark energy . 

While scientists have provided extensive evidence for the existence of dark matter and dark energy, they are each still poorly understood as, so far, scientists cannot directly observe them and can only observe their effects. 

Roughly 80% of all of the mass in the universe is made up of what scientists have dubbed "dark matter," but it's not known what it actually is or if it is even matter by our current definition. However, while dark matter doesn't emit light or energy and cannot, therefore, be directly observed, scientists have found overwhelming evidence that it makes up the vast majority of the matter in the cosmos.

Dark energy might have a similar name to dark matter, but it's a whole different component entirely. 

Thought to make up nearly 75% of the universe, dark energy is a mysterious and unknown force or entity that scientists think is responsible for the universe's ongoing expansion.

Smaller black holes can form from the gravitational collapse of a gigantic star, which forms a singularity from which nothing can escape — not even light, hence the name of the object. No one is quite sure what lies within a black hole, or what would happen to a person or object who fell into it – but research is ongoing.

An example is gravitational waves, or ripples in space-time that come from interactions between black holes. This was first predicted by Albert Einstein at the turn of the last century, when he showed that time and space are linked; time speeds up or slows down when space is distorted.

As of mid-2017, the Laser Interferometer Gravitational-Wave Observatory (LIGO) Scientific Collaboration has announced three black-hole interactions and mergers detected through gravitational waves, in just two years.

The team found these three events in about two years, indicating that when LIGO is implemented at full sensitivity, the observatory may be able to find these sorts of events frequently, scientists said in May 2017. Should a bunch of these black hole events be detected, it could help scientists learn how black holes of a certain size (several tens of sun masses) are born, and later merge into new black holes.

Stars (like our own sun) are immense balls of gas that produce their own radiation. They can range from red supergiants to cooling white dwarfs that are the leftovers of supernovas, or star explosions that occur when a big one runs out of gas to burn. These explosions spread elements throughout the universe and are the reason that elements such as iron exist. Star explosions can also give rise to incredibly dense objects called neutron stars . If these neutron stars send out pulses of radiation, they are called pulsar stars.

Planets are objects whose definition came under scrutiny in 2006, when astronomers were debating whether Pluto could be considered a planet or not . At the time, the International Astronomical Union (the governing body on Earth for these decisions) ruled that a planet is a celestial body that orbits the sun, is massive enough to have a nearly round shape, and has cleared its orbit of debris. Under this designation, Pluto and similar small objects are considered "dwarf planets," although not everyone agrees with the designation. After the New Horizons spacecraft flew by Pluto in 2015, principal investigator Alan Stern and others again opened up the debate, saying the diversity of terrain on Pluto makes it more like a planet.

The definition of extrasolar planets, or planets outside the solar system, is still not firmed up by the IAU, but essentially astronomers understand it to mean objects that behave like planets in our neighborhood. The first such planet was found in 1992 (in the constellation Pegasus ) and since that time, thousands of alien planets have been confirmed — with many more suspected. In solar systems that have planets under formation, these objects are often called "protoplanets" because they aren't quite the maturity of those planets we have in our own solar system.

Asteroids are rocks that are not quite big enough to be dwarf planets. We've even found asteroids with rings around them, such as 10199 Charilko. Their small size often leads to the conclusion that they were remnants from when the solar system was formed. Most asteroids are concentrated in a belt between the planets Mars and Jupiter, but there are also many asteroids that follow behind or ahead of planets, or can even cross in a planet's path. NASA and several other entities have asteroid-searching programs in place to scan for potentially dangerous objects in the sky and monitor their orbits closely. 

In our solar system, comets (sometimes called dirty snowballs) are objects believed to originate from a vast collection of icy bodies called the Oort Cloud. As a comet approaches the sun, the heat of our star causes ices to melt and stream away from the comet. The ancients often associated comets with destruction or some sort of immense change on Earth, but the discovery of Halley's Comet and related "periodic" or returning comets showed that they were ordinary solar system phenomena.

Among the biggest cosmic structures we can see are galaxies, which essentially are vast collections of stars. Our own galaxy is called the Milky Way , and is considered a "barred spiral" shape. There are several types of galaxies, ranging from spiral to elliptical to irregular, and they can change as they come close to other objects or as stars within them age.

Often galaxies have supermassive black holes embedded in the center of their galaxies, which are only visible through the radiation that each black hole emanates as well as through its gravitational interactions with other objects. If the black hole is particularly active, with a lot of material falling into it, it produces immense amounts of radiation. This kind of a galactic object is called a quasar (just one of several types of similar objects.)

Large groups of galaxies can form in clusters that are groups as large as hundreds or thousands of galaxies bound together gravitationally. Scientists consider these the largest structures in the universe.

This page was updated in Jan. 2022 by Space.com senior writer Chelsea Gohd.

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Elizabeth Howell (she/her), Ph.D., is a staff writer in the spaceflight channel since 2022 covering diversity, education and gaming as well. She was contributing writer for Space.com for 10 years before joining full-time. Elizabeth's reporting includes multiple exclusives with the White House and Office of the Vice-President of the United States, an exclusive conversation with aspiring space tourist (and NSYNC bassist) Lance Bass, speaking several times with the International Space Station, witnessing five human spaceflight launches on two continents, flying parabolic, working inside a spacesuit, and participating in a simulated Mars mission. Her latest book, " Why Am I Taller ?", is co-written with astronaut Dave Williams. Elizabeth holds a Ph.D. and M.Sc. in Space Studies from the University of North Dakota, a Bachelor of Journalism from Canada's Carleton University and a Bachelor of History from Canada's Athabasca University. Elizabeth is also a post-secondary instructor in communications and science at several institutions since 2015; her experience includes developing and teaching an astronomy course at Canada's Algonquin College (with Indigenous content as well) to more than 1,000 students since 2020. Elizabeth first got interested in space after watching the movie Apollo 13 in 1996, and still wants to be an astronaut someday. Mastodon: https://qoto.org/@howellspace

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The Space Race

By: History.com Editors

Updated: February 21, 2020 | Original: February 22, 2010

After World War II drew to a close in the mid-20th century, a new conflict began. Known as the Cold War, this battle pitted the world’s two great powers—the democratic, capitalist United States and the communist Soviet Union—against each other. Beginning in the late 1950s, space became another dramatic arena for this competition, as each side sought to prove the superiority of its technology, its military firepower and–by extension–its political-economic system.

Causes of the Space Race

By the mid-1950s, the U.S.-Soviet Cold War had worked its way into the fabric of everyday life in both countries, fueled by the arms race and the growing threat of nuclear weapons, wide-ranging espionage and counter-espionage between the two countries, war in Korea and a clash of words and ideas carried out in the media. These tensions would continue throughout the space race, exacerbated by such events as the construction of the Berlin Wall in 1961, the Cuban missile crisis of 1962 and the outbreak of war in Southeast Asia.

Space exploration served as another dramatic arena for Cold War competition. On October 4, 1957, a Soviet R-7 intercontinental ballistic missile launched Sputnik (Russian for “traveler”), the world’s first artificial satellite and the first man-made object to be placed into the Earth’s orbit. Sputnik’s launch came as a surprise, and not a pleasant one, to most Americans. In the United States, space was seen as the next frontier, a logical extension of the grand American tradition of exploration, and it was crucial not to lose too much ground to the Soviets. In addition, this demonstration of the overwhelming power of the R-7 missile–seemingly capable of delivering a nuclear warhead into U.S. air space–made gathering intelligence about Soviet military activities particularly urgent.

Did you know? After Apollo 11 landed on the moon's surface in July 1969, six more Apollo missions followed by the end of 1972. Arguably the most famous was Apollo 13, whose crew managed to survive an explosion of the oxygen tank in their spacecraft's service module on the way to the moon.

NASA Is Created

In 1958, the United States launched its own satellite, Explorer I, designed by the U.S. Army under the direction of rocket scientist Wernher von Braun . That same year, President Dwight D. Eisenhower signed a public order creating the National Aeronautics and Space Administration ( NASA ), a federal agency dedicated to space exploration.

Eisenhower also created two national security-oriented space programs that would operate simultaneously with NASA’s program. The first, spearheaded by the U.S. Air Force, dedicated itself to exploiting the military potential of space. The second, led by the Central Intelligence Agency ( CIA ), the Air Force and a new organization called the National Reconnaissance Office (the existence of which was kept classified until the early 1990s) was code-named Corona; it would use orbiting satellites to gather intelligence on the Soviet Union and its allies.

Space Race Heats Up: Men (And Chimps) Orbit Earth

In 1959, the Soviet space program took another step forward with the launch of Luna 2, the first space probe to hit the moon. In April 1961, the Soviet cosmonaut Yuri Gagarin became the first person to orbit Earth , traveling in the capsule-like spacecraft Vostok 1. For the U.S. effort to send a man into space, dubbed Project Mercury, NASA engineers designed a smaller, cone-shaped capsule far lighter than Vostok; they tested the craft with chimpanzees  and held a final test flight in March 1961 before the Soviets were able to pull ahead with Gagarin’s launch. On May 5, astronaut Alan Shepard became the first American in space (though not in orbit).

Later that May, President John F. Kennedy made the bold, public claim that the U.S. would land a man on the moon before the end of the decade. In February 1962, John Glenn became the first American to orbit Earth, and by the end of that year, the foundations of NASA’s lunar landing program–dubbed Project Apollo –were in place.

Achievements of Apollo

From 1961 to 1964, NASA’s budget was increased almost 500 percent, and the lunar landing program eventually involved some 34,000 NASA employees and 375,000 employees of industrial and university contractors. Apollo suffered a setback in January 1967, when three astronauts were killed after their spacecraft caught fire during a launch simulation. Meanwhile, the Soviet Union’s lunar landing program proceeded tentatively, partly due to internal debate over its necessity and to the untimely death (in January 1966) of Sergey Korolyov, chief engineer of the Soviet space program.

December 1968 saw the launch of Apollo 8, the first manned space mission to orbit the moon, from NASA’s massive launch facility on Merritt Island, near Cape Canaveral, Florida . On July 16, 1969, U.S. astronauts Neil Armstrong , Edwin “Buzz” Aldrin and Michael Collins set off on the Apollo 11 space mission, the first lunar landing attempt. After landing successfully on July 20, Armstrong became the first man to walk on the moon’s surface; he famously called the momen t “one small step for man, one giant leap for mankind.”

Who Won the Space Race?

By landing on the moon, the United States effectively “won” the space race that had begun with Sputnik’s launch in 1957. For their part, the Soviets made four failed attempts to launch a lunar landing craft between 1969 and 1972, including a spectacular launch-pad explosion in July 1969. From beginning to end, the American public’s attention was captivated by the space race, and the various developments by the Soviet and U.S. space programs were heavily covered in the national media. This frenzy of interest was further encouraged by the new medium of television. Astronauts came to be seen as the ultimate American heroes, and earth-bound men and women seemed to enjoy living vicariously through them. Soviets, in turn, were pictured as the ultimate villains, with their massive, relentless efforts to surpass America and prove the power of the communist system.

With the conclusion of the space race, U.S. government interest in lunar missions waned after the early 1970s. In 1975, the joint Apollo-Soyuz mission sent three U.S. astronauts into space aboard an Apollo spacecraft that docked in orbit with a Soviet-made Soyuz vehicle. When the commanders of the two crafts officially greeted each other, their “ handshake in space ” served to symbolize the gradual improvement of U.S.-Soviet relations in the late Cold War era.

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