Outer space is the space between celestial bodies, including planet Earth.

Space is not completely empty but consists of a relativistic vacuum consisting of a low density of particles (particles), mostly hydrogen and helium plasmas, as well as electromagnetic radiation, magnetic fields, and neutrons.

Recent observations prove that it contains dark matter and energy as well. The baseline temperature, determined by the residual radiation from the Big Bang, is 2.7 K. Plasma with extremely low density (less than one hydrogen atom per cubic meter) and high temperature (millions of degrees Kelvin) in intergalactic space accounts for most of the ordinary baryonic problem in outer space; Local concentrations have been condensed into stars and galaxies. The space between galaxies occupies a larger volume than the universe, and even galaxies and star systems are mostly empty and planets occupy almost the empty space.

There is no specific limit to the beginning of outer space, but in general, the Karman line, located at an altitude of 100 km (62 mi) above sea level, has been adopted as the beginning of outer space in order to record atmospheric measurements and space-related treaties and agreements. The general framework of international space law was established by the Outer Space Convention, which was passed through the United Nations in 1967. This convention prohibits any country from claiming sovereignty over space and allows all countries to explore space freely. In 1979, the Moon Agreement was established, which placed the surfaces of the planets and the space orbits around them under the authority of the international community. Where other articles were added to the agreement related to the peaceful use of outer space, prepared by the United Nations, however, it did not prohibit the deployment of weapons in space, including live tests of anti-satellite missiles.


Humans began to explore physical space during the 20th century through altitude balloon flights, followed by the launch of individual rockets in multiple stages. Yuri Kakarin of the Soviet Union was the first to discover the Earth's orbit in 1961, and since then unmanned spacecraft have reached all known planets in the solar system. Because of the high cost of access to space, manned flights did not go beyond the limits of the moon. In 2012, Voyager 1 became the first man-made spacecraft to reach the interstellar field.

It calls for reaching the lowest orbit around the Earth at a speed of 28,100 km/h (17,500 mph), which is much faster than any conventional vehicle. Outer space is also a challenging environment suitable for human exploration due to the dangers of double vacuum and radiation. Zero gravity has a detrimental effect on the functions of human organs, leading to muscle atrophy and osteoporosis. Manned spaceflights were limited to the orbit of the low Earth, the Moon, and the vicinity of the Solar System for unmanned flights; The rest of outer space remains inaccessible to humans

space definition

Space is defined as the space between celestial bodies, and it is called the term outer space to distinguish it from the air space that resides around the globe, and space can also be defined from a physical perspective as an unlimited, three-dimensional space in which objects take a relative position and direction.

Outer Space

Outer space is about 100 km or more from Earth, and it lacks air that helps all living things breathe, and light is also not scattered in it, and black prevails over blue, due to the lack of oxygen in outer space, which makes the sky blue. It is worth noting that it is not possible to accurately determine the area of ​​outer space, due to the difficulty faced by specialized detectors, as long distances in space are measured in light-years, which means the distance that light travels in one year, and is estimated at about 9.3 trillion km. Astronomers using telescopes and conducting studies have redrawn galaxies since the universe began 13.7 billion years ago, that is, before the Big Bang phenomenon occurred in the universe.

space components

Outer space contains a lot of gases, and small dust plankton, in addition to some particles and radiation, and magnetic and electric fields. Space is not empty as many people think, as it contains a lot of materials. And the rest of the elements of the death of the stars. The empty regions surrounding stars are described as cold and fragile, as the number of molecules present varies from one medium to another, in some regions every 1 cm2 contains only one molecule, while other regions contain many molecules, and hydrogen and helium molecules are widely spread in stellar circles, as It makes up 98% of the molecules, and some other elements are available, but with a lower density than hydrogen and helium, and they are as follows:

  • oxygen.
  • Nitrogen.
  • Calcium.
  • carbon.
  • some other metals.

Explorations and applications

For most of human history, space has been explored through remote observation; Starting with the naked eye, then using a telescope. Before the advent of rocket technology, the farthest human reach from outer space was done by balloons.

In 1935, the American airship "Explorer 2" reached an altitude of 22 km (14 mi). This number was significantly exceeded in 1942 when the Germans launched an A-4 missile that reached an altitude of 80 km (50 mi). In 1957, the Sputnik 1 satellite was launched by the Russian R-7 rocket, which was able to orbit the Earth at an altitude of 215-939 km (134-583 miles).

This was followed by the first human spaceflight in 1961 when Yuri Gagarin was sent into orbit around the Earth aboard the Vostok 1 spacecraft. The first to cross Earth orbit were Frank Bormann, Jim Lovell, and William Anders in 1968 aboard the Apollo 8 spacecraft, which achieved a lunar orbit and managed to escape from Earth at a distance of 377,349 km (234,474 miles).

The Soviet "Luna 1" was the first spacecraft to reach escape velocity, during a flight near the moon in 1959. In 1961, Venera 1 became the first planetary probe; Which discovered the presence of the solar wind and was able to fly close to Venus, despite losing the ability to communicate before it reached Venus.

The first successful planetary mission was the Mariner 2 mission that flew to Venus in 1962. Mariner 4 was the first spacecraft to pass Mars in 1964. Since that time, unmanned spacecraft have successfully studied all the planets of the solar system, in addition to Its moons and many minor planets and comets. To this day, these vehicles remain an essential tool for outer space exploration and Earth observation as well. In August 2012, Voyager 1 became the first human industry to leave the solar system and enter interstellar space.

The absence of air from outer space (the surface of the Moon) makes it an ideal location for astronomy at all wavelengths in the electromagnetic spectrum. As evidenced by the stunning images returned by the Hubble Space Telescope. This allowed us to see lights from 13.8 billion years ago - roughly to the time of the Big Bang.

However, not every location in space is suitable for placing a telescope observatory. Interplanetary dust emits near-infrared radiation that can mask emission from faint sources such as exoplanets.

Moving the infrared observatory to a location outside the dust location would increase the instrument's effectiveness in a similar way, a location like the Daedalus impact crater on the far side of the moon could shield a radio telescope from radio-frequency interference that hampers observations from Earth, and the deep void in space could create Attractive environment for some industrial processes, such as those that require ultra-clean surfaces.

The deep vacuum of space makes it an attractive factor for many industries, especially industries that require ultra-cleanliness such as the electronic chip industry. However, realizing this dream is still costly and unproductive for now.

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