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Hello Andrea,
I am a graduate student here at Lick Observatory, and I am happy to answer
your questions about the Earth.
1. Why is the Earth the only planet with life on it?
We think that several environmental factors have to be just right for life
to exist on a planet. First, there has to be lots of energy available for
the living organisms to use for their survival. Another way of saying this
is that the planet can't be too cold. If it's too cold, then no life could
survive just because there wouldn't be enough energy available. You also
probably need to have liquid water present in order to have life. Again,
this means the planet can't be too cold, or any water present would be
frozen ice. Also, the planet can't be too hot, or the water would all be
in its gas form: steam. Finally, you need to have an atmosphere to have
life; not too thick, and not too thin. The atmosphere is important for
keeping liquid water at the surface (otherwise the water would quickly
evaporate away), and it is also important for blocking deadly forms of
radiation from the Sun and other cosmic sources, such as X-rays. However,
too much atmosphere can be a bad thing for life. On Venus, the atmosphere
is very thick. So thick, that it acts like a very thick, wooly blanket for
Venus, making the surface very hot (hot enough to melt lead!).
The Earth is the only planet that we know of (so far) that meets all of
these requirements for life. However, don't make the mistake of jumping to
the conclusion that this means that the Earth is definitely the only place
that life exists! There are millions and billions of planets that we don't
know anything about. Most of these could very well be home to other life
forms, we just don't know.
2. Who named the continents and oceans?
Sorry, I don't know. I think they were named by many people.
3. Who made the Earth?
Hmm....there are two answers to this question. If you are religious, the
answer is God. If you are not, the answer is no one made the Earth.
Either way, the earth formed out of a big cloud of gas and debris that
collapsed and formed the Sun and the rest of the planets, over 4 billion
years ago. Whether the material that would form the Earth was guided by
the hand of God is unanswered and unanswerable. It depends on your own
belief system.
4. Where did all the water for the Oceans come from?
This is a really good question! There are two theories for this. One is
that the water always existed on the Earth, but it was mostly hidden at
first, mixed up with rocks and minerals deep inside the Earth's interior.
The water was released to the surface during a time when many volcanoes
were erupting billions of years ago. The other is that small comets and
asteroids containing ice hit the Earth, and deposited their water at the
surface. You may think that it would take an awful lot of comet and
asteroid impacts to make all that water, and you'd be right. But just look
at a picture of the moon and all of its craters. Each crater was caused by
such an impact, and the Earth has had just as many. (The moon has no water
today because it never had an atmosphere, so the water left by these comet
impacts would evaporate away into space).
5. What is the Earth made out of?
The Earth is made out of many things, and its "ingredients" depend on where
you look. Inside the Earth, deep near the center, the Earth is mostly
molten nickel and iron. Above that, it's mostly molten rock, containing
lots of silicon and other minerals and metals. At the surface, it's mostly
water and solid rock. In the atmosphere, it's mostly Nitrogen, Oxygen,
Carbon Dioxide, water vapor and other gases.
I hope these help answer your questions! Good luck on your project.
--
Jason Harris
Grad Student
UCO/Lick Observatory
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