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For example, the Earth's axial tilt, the angle of Earth's axis to the ecliptic, have very

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precise numbers.

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The universe is full of such specific values.

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Can you inform us about the fine-tuning in the universe?

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Yeah, when it comes to fine-tuning, there is sort of two levels of fine-tuning we want

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to make a distinction about.

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The first level of fine-tuning is we can ask the question, why do the laws of physics have

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to have the constants that they have?

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For example, the speed of light is 300 million, 3 times 10 to the 8 meters per second.

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So we can ask the question, okay, it had to be some value, maybe it would have been 2,

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you know, it could have been 2 times 10 to the 8 meters per second.

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Maybe it could have been 4, and is it, you know, we just happen to have 3, is that maybe

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not very special.

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It turns out it is special.

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It turns out you cannot deviate from 3 times 10 to the 8 meters per second very far before

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the conditions for life in the universe are not favorable.

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That is one example.

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The gravitational constant is another one.

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If the gravitational constant is too strong or too weak, it has very big effect on the formation

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of planets.

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There are forces inside the nucleus, the strong nuclear force and the weak nuclear force.

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Those forces, those parameters are also fine tuned.

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The sun is powered by a nuclear process where hydrogen and helium and beryllium and carbon

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and oxygen are formed in a few theories of nuclear interactions.

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It turns out that these energy levels are well connected, well matched to each other to make

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this happen.

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If they were just a little bit different, there would be no production of oxygen, for example,

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or very little production of oxygen.

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And so what we find is that the universe is very fine tuned in terms of the constants of

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nature.

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Those things that are expected to be the same all over the universe, but the value itself

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is a very special value.

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And the value is conducive to life in the universe.

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And that's the fine tuning of the parameters of the universe.

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But even in a universe that is so spectacularly fine tuned, as ours seems to be, extremely fine

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tuned, even when you have this kind of a universe, you can ask the question, how easy is it?

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How expected is it to have a planet like the Earth in this kind of universe?

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Can you be talking about, well, what are the processes that produce a planet?

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You know, there is a protoplanetary disk.

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There is a, you know, aggregation of materials.

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There is the formation of the planet.

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There is the bombardment that occurs because of the material in the universe, in the protoplanetary

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disk.

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Then there is the stellar formation that is going on.

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What kind of star are you forming?

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And it turns out that those conditions are also rare.

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In other words, even if you have a very friendly universe like ours, exceedingly well designed

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universe as ours, even then, when you ask the question, the laws that are operating in

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this universe, would they easily produce many, many Earths?

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Like if we go to the next star, are we going to find another Earth?

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Well, we have a very good understanding now of what are the conditions and what does it

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mean when we say an Earth?

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First we want a terrestrial planet, for example.

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In our own solar system, the Earth is a terrestrial planet, meaning it has rock, it's rocky.

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It has water, but it has rocks.

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But if I go to Jupiter, it's not that kind of a planet.

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If I go, you know, if you arrive at Jupiter, it is just a gas and the pressure builds up very

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rapidly as you descend into the gas, completely unfriendly to life.

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So you need a terrestrial planet, you need water, but you don't want too much water because

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you have to have those interfaces between land and water where the water thickness is

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small enough that there is a combination of moisture and sunlight that penetrates the water to keep

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the warm waters.

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That much of the food production in the sea occurs in the places where water is touching

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the land.

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When you go really deep, there's not enough sunlight in the deep to produce abundant life,

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essentially.

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And then you can ask, you know, what does it take to have a climate that is stable?

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And the Earth's axial tilt gives us the seasons, but it also is an axial tilt that is not doing

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this as we go around.

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This is not the case for our planetary neighbors.

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Mars, for example, does not have a stable axial tilt.

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Where does this axial tilt stability come from?

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We have this very large moon relative to the Earth.

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Our moon is actually part of our, the Earth-Moon system is actually part of a system that is

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really designed to keep us having a stable climate.

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So the moon is doing multiple things for us.

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It's not just there randomly.

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It has a job.

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We can talk about Jupiter.

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Jupiter has a job relative to the Earth, and the job is that Jupiter's mass is so high

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that it absorbs to itself.

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Its gravitational attraction essentially sweeps up and cleans up the debris in the inner

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solar system.

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For example, I was much younger, maybe 20 years ago, there was a comet that was viewable

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in the sky, the Shoemaker-Levy comet.

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And everybody was excited.

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It was in the news.

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And people would get out their telescopes and watch this comet.

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Well, eventually what happened to this comet?

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It crashed into Jupiter.

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And that's what Jupiter does.

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We are thankful to Jupiter because things crash into it.

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Asteroids and near-Earth objects that could potentially and sometimes do, you know, collide

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with the Earth.

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You know, the fact that they don't do that much more often is because of a massive gas

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giant, which Jupiter is, at a five astronomical unit orbit with very small eccentricity.

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What I mean by eccentricity is that the orbit of Jupiter is almost a perfect circle.

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If Jupiter had high eccentricity orbit, it would be an elliptical orbit.

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What does that mean?

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That means that here is the Earth orbit of the Earth.

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Now, orbit of Jupiter, if it comes in and out over a very long period of time, over millions

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of years, it can collide with the Earth and send us out of the solar system.

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This never happens because Jupiter's orbit is so well-behaved.

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So, high mass gas giant at a large, low eccentricity orbit is what we have with Jupiter, which is

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perfectly made for our convenience.

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And so, it is, you know, there's this principle that is supposed to be there that, what's called

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the principle of mediocrity, that says that we are nothing special.

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We shouldn't have this high view of ourselves.

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You know, but what we find is, in reality, that things are extremely well-matched to our

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health.

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You know, our planet is well-protected.

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We have the Moon doing what it's doing.

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We have the Earth.

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The Earth has a magnetosphere.

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The magnetosphere is protecting us from the solar activity.

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So the list is a very long list.

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And so there is, one could go a very long time talking about all the things that are true,

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in this case, you know, about the Earth's survivability.

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Absolutely.