Download What is space? In space, no one can hear you scream. This is

What is space?
In space, no one can hear you scream. This is because there is no air in space – it is a vacuum. Sound
waves cannot travel through a vacuum.
'Outer space' begins about 200 km above the Earth, where the shell of air around our planet disappears.
With no air to scatter sunlight and produce a blue sky, space appears as a black blanket dotted with
stars.
Space is usually regarded as being completely empty. But this is not true. The vast gaps between the
stars and planets are filled with huge amounts of thinly spread gas and dust. Even the emptiest parts of
space contain at least a few hundred atoms or molecules per cubic metre.
Space is also filled with many forms of radiation that are dangerous to astronauts. Much of this infrared
and ultraviolet radiation comes from the Sun. High energy X-rays, gamma rays and cosmic rays –
particles travelling close to the speed of light – arrive from distant star systems.
http://www.esa.int/esaKIDSen/SEMVY5WJD1E_OurUniverse_0.html
Solar Systems
Our solar neighborhood is an exciting place. The Solar System is full of planets, moons, asteroids,
comets, minor planets, and many other exciting objects. Learn about Io, the explosive moon that orbits
the planet Jupiter, or explore the gigantic canyons and deserts on Mars.
http://www.kidsastronomy.com/
Welcome to the
Beginner's Guide to
Propulsion What is
propulsion? The
word is derived from
two Latin words: pro
meaning before or
forwards and pellere
meaning to drive.
Propulsion means
to push forward or
drive an object
forward. A propulsion
system is a machine
that produces thrust to push an object forward. On airplanes, thrust is usually
generated through some application of Newton's third law of action and
reaction. A gas, or working fluid, is accelerated by the engine, and the
reaction to this acceleration produces a force on the engine.
http://www.grc.nasa.gov/WWW/K-12/airplane/bgp.html