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Stars and the Universe
The Universe - Life on Other Planets.
wondered for a long time
about the possibility of extraterrestrial life.
"Extraterrestrial" means "beyond the Earth".
to look for life on other planets (or moons).
The direct observation of life or fossils from
samples or pictures.
People have been to the moon and collected samples of rock
and dust which have been brought back to Earth for analysis.
Robots can land on planets and send pictures back to the Earth.
This has been done on Mars and Europa (a moon of Jupiter).
space also arrives on the Earth
when meteorites land.
Some of these may contain fossils of extraterrestrial life.
If you are not sure what a fossil is, see the GCSE Chemistry site.
Living organisms change the
chemical composition of a planet
(see how the evolution of life
has changed the Earth on the GCSE Chemistry site).
Scientists using telescopes can tell about the composition of
other planets by looking at the wavelengths of light which
are reflected from them.
A large amount of oxygen in the atmosphere of a planet
would indicate that life (photosynthesis) was present.
Scientists look at radio signals from space.
There is a project called SETI which stands for
the 'search for extraterrestrial intelligence' that looks for
meaningful signals within a narrow band of wavelengths.
SETI has been running for 50 years
but has not found signs of life on other planets yet.
there is no hard
evidence that life exists
outside of the Earth
from any of the methods listed above.
In view of
the fact that there are a huge number of
and that many of these planets may be suitable for life,
it seems highly likely that some forms
of life exist somewhere else in the Universe.
size and the age of the
Universe, it seems
unlikely that people on Earth will ever contact other life forms.
Still, who knows? By the time
you are reading this the aliens might already have landed!
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