On Earth, space begins at the Kármán line (100 km above sea level). This is where Earth's atmosphere is said to stop and outer space begins. This is not a firm boundary but is a convention used by scientists and diplomats.
Items in space are free to move back and forth; up and down; and left and right. These three dimensions are what make 3D space. Items also move forward through time, which is sometimes called the fourth dimension.
According to the big bang theory, all matter and energy in the Universe was compressed into a very small space. Then it exploded and started expanding. Space is still growing in size today; this means the distance from one galaxy to distant galaxies is getting longer.
Gravity is the force that keeps the Moon in orbit around the Earth and the planets in orbit around the Sun. Gravity can stretch and bend space similar to how a heavy ball placed on a stretched sheet of rubber will cause the rubber to stretch. The scientist who discovered that space can bend is named Albert Einstein. How gravity bends space is part of his theory of general relativity.
Regions[change | change source]
Geospace extends from Earth's atmosphere to the outer parts of Earth's magnetic field. There, it gives way to the solar wind of interplanetary space. Interplanetary space is the space around the Sun and planets of the Solar System. It extends to the heliopause, where the solar wind gives way to the winds of the interstellar medium. Interstellar space is the physical space within a galaxy not occupied by stars or their planetary systems. It continues to the edges of the galaxy, where it fades into the intergalactic void.
Exploration[change | change source]
Exploring space is very difficult because it contains no air and is so large that even the fastest ships can only explore a tiny part of it. It takes 3 days of traveling to reach the Moon and, depending on speed, it would take a long time to reach the closest star Proxima Centauri.
We gain most of our information about the items in space from different kinds of telescopes. Space probes also explore planets, comets and other space objects that are not too far. In 1998, NASA launched the Deep Space 1, a space probe that explored the planet Mars and the comet Borrelly.
Other pages[change | change source]
References[change | change source]
- Daintith, John; Gould, William (2012) . Collins Dictionary of Astronomy (Fifth ed.). HarperCollins. p. 414. ISBN 9780007918485.
- "Where does space start?", All About Space (Imagine Publishing) (1): 84, 2012-06-28
- GCSE Physics: The Revision Guide. Coordination Group Publications. 2006. p. 44. ISBN 9781841466415.
- Woolley, Steve (2011). Edexcel IGCSE Physics Revision Guide. Pearson Education. p. 13. ISBN 9780435046736.
- Schrijver, Carolus J.; Siscoe, George L. (2010), Heliophysics: Evolving Solar Activity and the Climates of Space and Earth, Cambridge University Press, ISBN 0-521-11294-X, http://books.google.com/books?id=M8NwTYEl0ngC&pg=PA363
- "Deep Space 1". National Space Science Data Center. 2012 [last update]. http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1998-061A. Retrieved 26 March 2012.