I learned in class recently that the Earth is 4.6 billion years old, but our oldest rocks are 3.9 billion.
First, do we know how old the Earth is by dating asteroids? Since they were formed at the same time as the planet that would make sense.
Second, does that mean it took .7 billion years for the Earth to cool down? What made it cool?
Cite sources please.
2006-12-22 04:43:12 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Astronomy & Space
When something expands, it cools. Because the heat it contains is 'spread out' more. The whole universe is expanding, so the whole universe is cooling. I just think they haven't found a rock older yet, but there may be one around here somewhere. Maybe not.
Actually billionths of a second after the Big Bang, the temperature dropped dramatically, and the next billionth second even more. In the first second after the Big Bang, the universe went from infinitely small to a size of a BB. The next instant it was as large as the earth. What's really eerie is that the center of our universe is the universe.
2006-12-22 04:53:49 · answer #1 · answered by Anonymous · 3⤊ 1⤋
It is generally accepted (theory and computer simulator agree) that the entire solar system formed at 'about' the same time ... so, yes the asteroids were created at the same time as the Earth.
And yes, if the oldest rocks on earth are 'younger' that the age of the Earth then it is reasonable to assume that this is because at some stage the rocks were all molten.
The asteroids cooled down almost immediately because they are so small (and never very hot to start with). The Earth took longer to cool down - it is a lot bigger and every asteroid impact added a bit more heat.
However the Earth may have cooled down to a solid body well before the 0.7 billion year mark - but at some point before 3.9 billion years ago it was hit by a VERY large asteroid ...
This not only melted the entire planet but a large lump was 'scooped' out to form the moon .... and both Earth & Moon then cooled down more or less together by 3.9 billion years ago.
Bodies cool down because they radiate away more heat than they are generating or is coming in from outside.
Mars is able to radiate away heat better than the Earth (so it's a lot colder) - but Venus is not able to radiate away heat so easily, so it stays very hot :-)
2006-12-22 06:04:53 · answer #2 · answered by Steve B 7 · 2⤊ 0⤋
Yep, that's about right. Asteriod dating helps us figure out about when our solar system formed, or at least when it cooled enough for rocks to form. They are dated using uranium dating - like carbon dating, but good for billion year time scales instead of thousands of years. The Earth cooled by radiating heat energy, in the form of photons, into space.
2006-12-22 07:22:29 · answer #3 · answered by eri 7 · 0⤊ 0⤋
Tell us what your theories are. You only asked questions.
2006-12-22 05:26:16 · answer #4 · answered by Gene 7 · 1⤊ 0⤋
everything cools when it dissipates its energy
2006-12-22 04:46:53 · answer #5 · answered by Anonymous · 0⤊ 2⤋