outer space
What is outer space?
What is the Kármán line?
What is the composition of outer space?
Who was the first human in space?
What is the Outer Space Treaty?
outer space, the region beyond Earth’s atmosphere—thus, the entire universe (including planets, stars, and galaxies) except Earth and its immediate surroundings.
Definition
Investigating the limits of aerospace design in the 1950s, Hungarian-born American engineer Theodore von Kármán assessed the distance from Earth at which aircraft flying at a given velocity could no longer rely on the force of lift for staying aloft. On the basis of this work, rough calculations arrived at a figure close to 84 km (52 miles). This number, later dubbed the Kármán line, has come to be widely used to indicate the boundary between the atmosphere and outer space.
Other figures have been proposed over time. In the early 1960s the Fédération Aéronautique Internationale (FAI) adopted a 100-km (62-mile) boundary, and NASA prefers to use an 80-km (50-mile) boundary. In reality, the boundary cannot be precisely defined, because Earth’s atmosphere thins out gradually rather than ending abruptly. However, it roughly corresponds to the 80-km upper limit of the mesosphere.
" height="20" alt="HEW Logo">
Outer space extends in all directions, and distances across space are typically measured using the light-year, the distance traveled by light in a year (about 9.46 trillion km [5.88 trillion miles]). The observable universe, the part of outer space that can be viewed from Earth, is about 93 billion light-years across. (The universe itself is about 13.8 billion years old. However, because it is expanding, objects that emitted light 13.8 billion years ago, from a distance of 13.8 billion light-years, are now even farther away from Earth—approximately 46 billion light-years away).
Composition
The matter-energy content of outer space is 68.3 percent dark energy (a repulsive force), 26.8 percent dark matter (known only through its gravitational influence), and 4.9 percent ordinary matter. The ordinary matter is concentrated mostly in stars in galaxies. There are about 100 billion to 2 trillion galaxies, each containing about 100 billion to 1 trillion stars.
However, most of outer space is nearly empty. Nevertheless, it is not a perfect vacuum: even the intergalactic medium, the space between galaxies, contains about one atom per cubic meter. (By comparison, air has about 2 × 1019 molecules per cubic cm.)
Human exploration in outer space
The first artificial object to reach outer space was a German V-2 rocket, which reached an apogee of 176 km (109 miles) on June 22, 1944. Following further years of research and advances in rocketry, the first artificial Earth satellite, Sputnik 1, was launched by the Soviet Union on October 4, 1957. Soviet cosmonaut Yuri Gagarin became the first human in space, on April 12, 1961. Within 10 years of that first human flight, on July 20, 1969, American astronauts Neil Armstrong and Edwin (“Buzz”) Aldrin made the first lunar landing.
The trusted destination for professionals, college students, and lifelong learners.
SUBSCRIBE
Although no humans have gone to the Moon since 1972, a series of space stations has been set up since the late 1970s. The International Space Station (ISS), completed in 2011, currently serves as a base for humans living and working in space on a permanent basis.
In addition, Earth-orbiting satellites and robotic spacecraft have been used to gather valuable data about the Sun, Earth, other bodies in the solar system, and the universe beyond. The space probes Voyager 1 and Voyager 2, launched in 1977, became in 2012 and 2018, respectively, the first spacecraft to pass out of the solar system into interstellar space.
Outer space is governed by the 1967 Outer Space Treaty, which binds all signatories to use outer space only for peaceful purposes. Parties are prohibited from placing nuclear arms or other weapons of mass destruction in orbit, on the Moon, or on other bodies in space. Countries cannot claim sovereignty over the Moon or other celestial bodies. However, airspace on Earth remains part of countries’ sovereign territory, and this has kept the debate on the exact altitude of the Kármán line open, as it brings into question the legality of satellites above a country’s airspace.