How to find Earth 2.0?! | Space with Sarah #11 | @spacewsarah


Hi and welcome to Space with Sarah. A very popular question to ask an astrophysicist
seems to be: Is there life elsewhere? Do aliens exist? Have we been visited by aliens? One answer could be “of course there is life
elsewhere, there are so many galaxies, stars and planets, why would earth be so special? If it started here, it must have started elsewhere”. But the truth is that *we don’t know*. We have one data point to work with and that
is life here on Earth. We have not found life elsewhere, and equally
as important we have never been able to produce life out of non-life. The verdict on how life forms is still out. Here on Earth, the first form
of life started as a single-cell-organism in the very early in the history of the solar system. It is thought that life formed roughly 4 billion
years ago, and the Earth is only 4.6 billion years old. It seems that when life could start on Earth,
it did. It is pretty important to keep in mind that
the human race as we know it now (homo sapiens) have only existed for ~200.000 years, which
is only a tiny fraction of the time that Earth has existed. So intelligent life seems to take a while
to form. You can define intelligent life however you
like, but, we do indeed seem to be the only species
who have ever explored the origin of the Universe here from Earth. It’s a big unknown whether or not there is
life out there, but one thing that we have learnt a lot about in the last decades is
planets around other stars than the Sun. Maybe you remember this term from a previous
video? That’s right – exoplanets. We also talked about how we think a planet
needs liquid water, a rocky surface and an atmosphere for life to start. In our lifetime it will probably be hard
to prove that there is life out there, unless we find fossil life on one of the nearby planets
(for example Mars). However, what we CAN do in the very near future
is start probing the atmospheres of other rocky planets. We can search for rocky planets around other
stars, at the right distance from their host star to be able to have liquid water and probe
what their atmosphere is made of. This is all a very new and active field of
research. When we point a telescope to a star that has
a planet orbiting it, we can analyze the light from the star alone and the light from the
star with the planet in front of it. By investigating the differences between those
two observations we can figure out what the planet’s atmosphere is made of. This is done by subtracting the observation
of the star from the observation of the star AND planet. This is not as simple as it sounds, because
the star is A LOT brighter than the planet and many other technicalities, but these experiments
are starting to be made. This will enable us to find atmospheres with
for example water vapor, oxygen, ozone, and carbon dioxid which can help us in the search
for signs of life. So my answer would be: we have not found life
other places than on Earth, and we might not actually prove the existence of life elsewhere
in our lifetimes, but we WILL be able to find Earth 2.0 with the right distance from its
star and with a similar atmosphere to what we have here on Earth,
if it exists. That to me is very exciting. The fact that we probably won’t be able to
go there anytime soon is a whole other discussion on the feasibility of interstellar travel,
which I’ll get into some other time. Thanks for watching Space with Sarah. If you are still curious about Universe, please
subscribe to the channel and as always: keep wondering.

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