Date: July 10, 2009

Title: How Amazingingly Unlikely is Your Birth

Podcaster: Larry Sessions

Links: North American Skies, NASkies on Twitter
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Description: Eric Idle’s wonderful “Galaxy Song” is an exuberant, if a bit dated, introduction to various aspects of astronomy filled with facts about the Universe. Idle concludes with a reference about how “amazingly unlikely” is your (or specifically, Mrs. Brown’s) birth. The chances against all the untold things that need to happen for a baby (or a planet or star) to be born are indeed astronomically large, a fact that some have used to used to argue in favor of divine creation. But how reasonable is that?

Bio: Larry Sessions is a former director and staff astronomer at Denver’s Gates and Fort Worth’s Noble planetariums, and now is an instructor for Metropolitan State College and the Community College of Aurora, Colorado. He also is the webmaster and editor for the Southwestern Association of Planetariums, as well as his own website, North American Skies, and a contributor to both Space.com and EarthSky.org. A NASA/JPL “Solar System Amabassador,” he has every copy of the Royal Astronomical Society’s annual handbook since 1971.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Mark DeVito and dedicated to his best friend the late Jeffery Medkeff, also known as the “Blue Collar Scientist.” Jeff’s dedication and commitment to science and astronomy is well known through out the professional and amateur astronomy field. Thank you Jeff for your commitment and belief in me. Your friendship and teaching will never be forgotten and the entire family misses you deeply. You can read more about Jeff and Mark at www.stargazersfield.com.

Transcript:

Welcome to this edition of “Strange and Wonderful Facts about the Universe,” or perhaps you know it by its more prosaic title “365 Days of Astronomy” podcast. I’m Larry Sessions, former planetarium director and now a “Cosmic Awareness Facilitator” — ahem, that is, I teach astronomy in Denver. I also write a little, occasionally lecture at Gates Planetarium, produce the website North American Skies, tweet frequently at NASkies, blog on the EarthSky website, serve as a NASA/JPL Solar System Ambassador, and when things get boring, I set fire to my hair.

For years one of my favorite songs has been the “Galaxy” song by Eric Idle and John Du Prez. Given a little poetic license and the nearly 30 years since it was written, the song contains a good deal of reasonably accurate astronomical information. However, the part I like most is the section the end, that includes:

“So remember, when you’re feeling very small and insecure,
How amazingly unlikely is your birth…

( I would have included the actual audio from the song, but failing at my feeble attempts get official permission to use it, I’ll defer to the copyright safe side and just leave you to your own devices. The MP3 can be found easily on the Internet.)

So, how amazingly unlikely is your birth? There are several ways to look at this. Given the chromosomes in human DNA, and the possible ways of combining them (2 raised to the 46th power), there are more than 70 trillion combinations. (For anyone not using the American system, that’s 70 million times a million!). This, of course, is far greater than the total number of people who have ever lived. Thus you are a one-in-70 trillion occurrence. Out of 70 trillion chances, you became you. One out of 70 trillion is pretty poor odds, but amazingly enough, you are actually here, listening to or reading this — a true wonder of nature.

But to be fair, I had a one out of 70 trillion chance of being me as well, Barack Obama had the same odds, as did Abraham, Vlad the Impaler and … well, you get the point. We are all the result of absurdly unlikely odds, but in truth, any combination is unlikely.

Now, what about the Universe as a whole? What are the chances that our Universe would have just the right conditions not simply for stars to form, but for planets with appropriate combinations of elements, warmth and so on for the development of life as we know it? Turns out that the odds are pretty small. So small in fact that there really are no good estimates. There is no reason, in physics, for the Universe to be suitable for human, or any life in general. No reason at all. Oddly, our Universe seems to have conditions that are precisely tuned to allow planets such as ours, and life, such as ours, to evolve. In fact a number of scientists have outlined several physical parameters, thought to be the same throughout the Universe, that are exactly what they should be for life to exist and grow. The odds for this to happen by chance are phenomenally small — far smaller that the one in 70 trillion odds of getting the exact combination of chromosomes that you, as a unique individual, have.

This is an odd situation indeed. So unusual and unexpected that some use it as an argument that there must surely have been a Creator fiddling with the controls of the Creation Machine to make everything work out precisely for us. Creationists use the argument that this apparent fine tuning could simply not happen by chance. But that’s not the only possibility.

What if it did happen purely by chance, unlikely though it is mathematically. After all, you are very unlikely, but you exist along with billions of others whose odds were just as small. The chances of getting an apparently fine tuned Universe such as ours are even smaller, but there still is a chance. And if we are simply a fluke, a byproduct of lucky happenstance, how would we know? We have nothing to compare our Universe to, and if it had been different, we likely would not be around to ask the question.

Go out to a beach and pick out one single grain of sand. Considering the probable number of sand grains on that beach, the chance that you would pick up that particular grain are trillions to one. Yet you did pick up that grain. It was just “happenstance” — I prefer not to say “luck,” as that word has other connotations. It could be that our Universe is as it is simply by pure happenstance and nothing else.

Now, what are the actual odds of our particular Universe, with the exact combination of factors compatible with life? As I said before, we can’t say for sure. However, the number of other possibilities is quite large. In fact, physicist Leonard Susskind and others think that the number of possibilities is truly mind boggling, 10^500. Now, I can’t even begin to express this number in any way other than mathematically. I’ll give you a completely inadequate analogy. Imagine grains of fine sand about 0.2 millimeters in diameter. Then imagine the entire known Universe, the visible part of which occupies a spherical volume some 27 billion light years across. Then imagine that you fill that entire known Universe with the fine sand grains mentioned. There would be something of the order of 2 * 10^90 grains of sand. Thus the number of possible Universes would be at least a trillion trillion trillion trillion — oh, well I’m not going to say it all out or you would fall asleep before I finished. Just imagine multiplying a trillion by itself 33 times. (trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion.) The number of possible Universes would be that absurdly large number of times greater than all the sand grains that could fill a sphere the size of the known Universe.

So, if there were 10^500 possible Universes, not only is ours unimaginably unlikely, but consider the fact that even once our Universe formed against such odds, the chance of our Sun, the Earth and you would form exactly as they have are all that much less likely. And frankly, it doesn’t get much more unlikely than that.

Thanks for listening.

End of podcast:

365 Days of Astronomy
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