Are we alone in this world?

We just don't know. We know that life exists on Earth, but what about elsewhere in the universe?Most astronomers believe in extraterrestrial life—we just haven’t found it yet. All Earth’s living things are made out of chemical elements found throughout the universe, so it would be extraordinary if some
form of life hadn't developed elsewhere.

Messages from Earth
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Launched in 1972, Pioneer 10 was the
first spacecraft set on a course that would
take it out of the solar system. A plaque on board
indicates where it has come from and explains
how to get in touch in case intelligent
life should find the craft
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The farthest artificial body from Earth
is Voyager 1, which launched in 1977.
It carried a gold-plated disk of sounds and
images of life on Earth. It will be 40,000 years

before it approaches another planetary system.
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The first deliberate radio message
intended for extraterrestrials was sent in
1974. The Arecibo radio telescope in Puerto
Rico transmitted a three-minute radio message
toward the star cluster M13. It will arrive in
around 25,000 years’ time.

Questions of life:

In 1961, astronomer Frank Drake drew up a list of questions to help calculate
how many intelligent communicating civilizations
live in our Milky Way Galaxy:

01: How many stars does our galaxy contain?

02: What fraction of stars have planets?

03: How many wet, warm planets occur in each planetary system?

04: If the planet is wet and warm, what is the chance of life breaking out?

05: What is the chance of this life becoming intelligent?

06: What is the chance of this intelligent life being able to communicate with
life elsewhere?

07: During what fraction of a planet’s existence will intelligent,communicating
life exist?

In 1997, scientist Carl Sagan figured out that one million intelligent, communicating life forms exist in our galaxy, and the nearest is only 300 light-years away.

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