Deep Six podcast: "The Goldilocks Zone"

TOP FLOOR OF 6ABC STUDIOS, PHILADELPHIA - December 8, 2008 This is probably one of the most uninhabitable places in our entire building. It is loud, it is dark, it is dusty, and it is a bit cold. An uncomfortable place to be, to say the least. ________________________________________________________________________

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So why am I here? Well, it's not to make repairs on our climate control system. It is to help explain why we, as Earthlings, are so darn lucky. Really.

We, as humans, tend to focus on our problems. Why? Well, maybe it's because we've been programmed to try and fix them, to make our lives better. Things can always improve on this planet, despite how good we have it already.

I mean, we've got it really good. If we didn't, we wouldn't be here to appreciate it - or take it for granted.

Introducing the Goldilocks Zone. It is a phrase that - at least in my own research on the internet - seems to be credited to British astronomer James Lovelock. We live in the Goldlilocks Zone, because, like the porridge in the story of Goldilocks and the Three Bears, our planet's conditions are "not too hot, not too cold, but just right."

So many things have come together for our planet to be hospitable for the development - and the flourishing - of life.

Dr. Michio Kaku, our favorite theoretical physicist in the entire world, wrote a book called "Parallel Worlds" which discusses this phenomenon. Dr. Kaku will help me explain what we mean when we say we live in the Goldilocks Zone.

We start with the sun, and go outward.

The sun, the center of our solar system, is just perfect in size for us. If it were bigger, conditions would be too hot for a planet of our size. If it were smaller, it wouldn't be hot enough. If it were more massive, it would destabilize the planets of our solar system, sending them into tighter orbits, perhaps causing a few of them to crash into each other. If the sun were less massive, the planets would orbit further out, with some of them possibly being flung out into space. In addition, if the sun was a lot older, and near the time of its death, things would be pretty miserable for us on Earth. If it were in the early stages of its life, it probably wouldn't provide the warmth we need to survive. The sun, my friends, is just about perfect.

Now to the Earth.

Our planet dwells in a region of the solar system that provides favorable conditions for the formation of liquid water. It is possible to have liquid water in other places of our solar system, but only because of massive tidal forces from the larger planets, like Jupiter. For instance, the Jovian moon Europa may have liquid water beneath its frozen crust, the possible result of the massive gravitational force from its planet. NASA hopes to find out for sure by crashing a probe into Europa. Perhaps we will know one day if Europa has water, and extraterrestrial life. But that discussion is for another day.

The bottom line is, because of our position from the sun, our planet is a good place for liquid water to exist. In fact, a great place - it covers more than 2/3rds of our surface. If our orbit was a little further out, the oceans would freeze. If it was a little closer to the Sun, the oceans would evaporate. Our position as the third planet of our solar system is primo.

The Goldilocks Zone seems to also require a moon, like the one we have. By the way, why did we name our orbital partner "the Moon?" Why couldn't we come up with a name like the other moons of the solar system? Oh well.

Anyway, our Moon provides stability, for one thing. Unlike the other planets, our Moon is quite large relative to our planet's size - almost a quarter of the Earth's size. Because of this, it keeps the Earth from wobbling too much when it rotates. In fact, the Moon is locked in a dance with the Earth - as the Moon rotates, its one side continually faces the Earth. You've heard of the Dark Side of the Moon - well, that refers to the opposite side that we on Earth never see. It is not always dark, though. Because it always faces away from our planet, it gets hit by meteors and comets a lot more often, leaving it with far more craters than the side of the Moon we always see.

There is another fascinating coincidence as part of our Goldilocks Zone. You can observe this phenomenon during a lunar eclipse. Think about the reason why the Moon is just big enough to cover the sun, but not so big that it obscures the Sun's outer rays. It is because, relative to our eyes, the Moon is almost exactly the size of the Sun. If you could somehow place the Moon and the Sun next to each other in the sky, they would appear to have the same diameter.

The reason for that is, in an amazing coincidence, the Sun is 400 times bigger than the Moon, and 400 times further away. That is the essence of something being "not too hot, not too cold, but just right." By the way, some believe having lunar and solar eclipses somehow benefits life on Earth. How it does, has not exactly been proven yet.

We listed several reasons why we live in a Goldilocks Zone. And yet, we are not done. Here is another:

The presence of Jupiter, the largest planet in our solar system. We've already mentioned the fact that the "dark side" of the Moon gets hit by meteors and comets a lot. That helps protect the Earth from suffering the same fate. Well, Jupiter does the same thing, but to a much larger degree. Because it is so big, and because its gravitational pull is so massive - so massive, that a 200 pound man on Earth would weigh 63,600 pounds - it actually sucks comets away from us. Some call the presence of a large planet like Jupiter a "comet sweeper." If it wasn't for the big guy, we here on Earth would be bombarded by space stuff.

Still, we are not done describing how lucky we are in this Goldilocks Zone. Our solar system is about 26 thousand light years away from the center of the Milky Way Galaxy, the galaxy that we inhabit. This area is in the outer area of one of its spiral arms. Because we are so far away from the center, it is more spread out. Fewer comets, fewer space rocks, and therefore, an even lesser chance of getting smacked by something from out there.

We could go on and on. Dr. Kaku, in his book Parallel Worlds, mentions how two astronomers noted reason after reason after reason that living on Earth is so special: having the right amount of oceans, having the right amount of oxygen in the atmosphere, having the right amount of tilt in the planet's axis to allow our four seasons to take place. There were so many reasons, Dr. Kaku writes, that the astronomers wondered if intelligent life is unique to the galaxy, because we live in so many narrow bands of our Goldilocks Zone - just a little bit each way, and life does not exist.

If Dr. Kaku's works interest you - and believe me, they are interesting, go to and do a search for "michio kaku." You can watch my interview with him, and learn more about his latest book, which explores the possibilities of seemingly impossible things.

I'm Matt O'Donnell, and that's your Deep Six.
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