Outer space begins about 100 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. 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. In space, no one can hear you scream. This is because there is no air in space. Sound waves cannot travel through a vacuum.
Outer
space
begins
about 100 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.
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. In
space
, no one can hear you scream. This is
because
there is no air in
space
. Sound waves cannot travel through a vacuum.