Home » Why We are Alone in the Galaxy: Marc Defant (Full Transcript)

Why We are Alone in the Galaxy: Marc Defant (Full Transcript)

Marc Defant

Marc Defant is a tenured professor of geochemistry at the University of South Florida and studies volcanoes and the origin of the continental crust.

Here is the full text of Marc’s talk titled “Why We are Alone in the Galaxy” at TEDxUSF.


Marc Defant – TEDx Talk Transcript

I wrote a book about the history of life, and I started noticing when I did my research that there were the statistically improbable events seemingly that had to occur in order for us to get intelligent life here on our planet.

And SETI has been now searching for the extraterrestrial intelligence, they’ve been searching for life for 54 years and they, of course, haven’t found any intelligent life.

And so I got to thinking maybe they weren’t finding it because it’s extremely difficult to occur, evolutionary or whatever.

So tonight what I’d like to do is, I’d like to give you 3 examples of these statistically improbable events but please keep in mind that there are literally hundreds of these events which need to occur in order to get intelligent life on this planet, in my opinion.

Well, I need to go back to the Big Bang and talk a little bit about the Big Bang Theory, and I hope to god that when I said the Big Bang Theory, the first thing that came to your mind wasn’t the television show, because we’re all in trouble if that’s the case, and it could be a long talk, too.

Well, in the Big Bang, 13.8 billion years ago, there was hydrogen and helium, that’s it. So scientists recognize that we need another source for all the other elements that we find in our universe and we now know that source is a supernova.

And a supernova is literally the death of a giant star. It collapses in on itself, it forms all of the elements in the periodic table, other than hydrogen and helium, and then, it explodes and it sends that material out and into its local space.

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Well, now I want you to picture something called a solar nebula. This is a gaseous cloud that once existed out there that later collapses to form our solar system. And that cloud was originally enriched only in hydrogen and helium.

So we have to have all of these supernovae erupting out there and enriching that solar nebula in all of the elements requisite for intelligent life in particular on our planet. And if we don’t have that, then we can’t get an intelligent life. And then at some point, there has to be a supernova nearby our solar nebula which forces it to collapse.

Now how do I know that there was a supernova out there that forced our solar nebula to collapse?

Well, I think that’s one of the most interesting scientific discoveries of all time and it doesn’t get much press, so I’d like to share it with you tonight.

The Allende Meteorite is believed to be material that formed from our solar nebula as it was collapsing to form our solar system. One of the reasons we know that is it has calcium-aluminum inclusion in it that dated to 4.56730 billion years ago. So, that’s the oldest date that we find in our solar system, and we now use that date as the beginning or the origin of our solar system.

Well, in this calcium-aluminum inclusion is a strange thing. We find an isotope of magnesium, called magnesium 26, and we shouldn’t have magnesium in calcium-aluminum inclusion. So scientists were puzzled over this, and they recognized though at some point that magnesium 26 is the decay product of aluminum 26.

Aluminum 26 has a relativity short half-life of 717,000 years, so that means that in 7 to 10 million years, all of the aluminum 26 is going to decay away to magnesium 26, we don’t have any aluminum 26 on the planet today that’s because it all decayed away billions of years ago, when it first formed from a supernova.

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So, I think you can see here what’s happening. We had a supernova nearby our solar nebula, and injected it with all of the requisite elements including aluminum 26 and forced it to collapse, and as it collapsed, the calcium aluminum inclusion is formed, rich in aluminum 26, and that aluminum 26 is then, decayed to magnesium 26, hence the reason we have magnesium in this calcium-aluminum inclusion.

So, I don’t know, I think that is an incredible scientific discovery. I’m a little prejudiced, but think about that, we can take things that we see today, we can look at them, we can study them, and then, we can extrapolate back to things that were happening 4.5 billion years ago. It’s amazing, I think.

And where does the statistical improbability come into play here?

Well, think about what has to happen. You have to have our solar nebula out there with just hydrogen and helium in it, to begin with. And then, you have to have all the supernovae going off which inject it with all of these elements bigger than hydrogen and helium, and just the right amount, and none of them can force our solar nebula to collapse.

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