Pilbara in context of universe

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Pilbara in the context of the universe

This is a transcript of a QuickTime movie (22.6 MB) recorded in the Pilbara in 2005. Dr Seth Shostak, Senior Astronomer at the SETI Institute in California, places the Pilbara in the context of the formation of the universe.


There are some pretty old rocks here, some of them three and a half billion years old. Of course there are old rocks everywhere on Earth but the ones here in the Pilbara are better preserved because they haven’t been chewed up quite as much as elsewhere.

So that is why we are here, trying to find the first signs of life on Earth. But you know, as old as these rocks are, they are not as old as the stars in the night sky. If you know where to look for the oldest stars, you can find stars that are three and four times as old as these rocks.

Those stars were built right at the start of the universe, the so-called Big Bang. Now we know when that was. We know it pretty accurately. 13.7 billion years ago. Call it 14 billion years ago. 14 billion years ago something happened. A little distortion of time and space and BAM suddenly there was this enormous explosion if you will that produced space, that produced time, that produced matter and then 10 billion years later produced the sun, the planets and including this one, the Earth.

So we’re kind of newcomers, the Earth that is. The Earth has been around for about 4.6 billion of the past 13.7 billion years, so the universe is three times as old as the Earth. That’s somewhat remarkable to me, because it could have been the universe was a thousand times, or a million times older than the Earth. But it’s not. So if you were around here – not here, because there was no here then in this part of the universe four and half…4.6 billion years ago…you would have seen a very strange thing. You would have this star forming….the star that ultimately became our sun. But it didn’t look like the sun in the beginning. It was just like a hot spot in a big disk of dust and gas. The sun formed in the center of that disk and the leftover material that didn’t go into forming the sun became Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto…all the planets you learned about in junior high school, including this one.

So that was 4.6 billion years ago. Now you might think ‘well okay, if the Earth is that old, maybe there’s life that’s older than three and a half billion years. Maybe…maybe there is, but you see for the first billion years the Earth was not such a great place to be.

There was still left over material from the formation of the solar system that was regularly slamming into the Earth and all the other planets as well. Big asteroids big rocks made it pretty tough to have anything here on Earth other than hot rock. Now if you doubt that all you have to do is take a pair of binoculars and look at the moon sometime. You’ll see it is pock-marked. Bad complexion. Most of those pock marks, most of those craters were rocks that hit the moon about 3.8 billion years ago. About 3.8 billion years ago there was what’s called the heavy bombardment – rocks slamming into the planets – we were like ducks in a shooting gallery here in the solar system – those rocks were hitting the Earth too. Nothing could live here.

That was 3.8 billion years ago. And then suddenly things got better. All the big rocks were used up. Oh sure, there’s the occasional asteroid or comet today, but nothing like there was 3.8 billion years ago. So things got better, the Earth cooled down, big rocks from space weren’t destroying any chances that life might have had.

These old rocks that we’re looking at here suggest – not yet proven yet - but they certainly strongly suggest that there was life on this planet 3.5 billion years ago. That heavy bombardment ended 3.8 billion years ago. The difference isn’t very much. 300 million years. Might be a long time if you are waiting for a bus. But for geologists, 300 million years isn’t very much.

What does this say? It seems that life got started like that, right away – very quickly – as if it’s not hard to get started. And if that’s the case, then we can expect that life has gotten started on many worlds out there, and that life is as common as telephone poles in the universe.




Early Life



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