GCSE SCIENCE PHYSICS HIGH SCHOOL - The Universe - Life on Other Planets - SETI

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The Universe - Life on Other Planets.

People have wondered for a long time
about the possibility of extraterrestrial life.
"Extraterrestrial" means "beyond the Earth".

Scientists use three approaches to look for life on other planets (or moons).

1. 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 have also collected samples or sent pictures back to the Earth
from Europa for example (a moon of Jupiter).

Material from 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.

2. 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 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.

3. Scientists look at radio signals from space.
There is a project called SETI which stands for
the search for extraterrestrial intelligence
which looks for meaningful signals within a narrow band of wavelengths.
SETI has been running for 40 years
but has not found signs of life on other planets yet.

So far, 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 stars and planets
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.

Given the 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!

Headings The Earth and Beyond Universe Search Questions

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