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YERVANT TERZIAN: Greetings, everyone. My name is Yervant Terzian. I'm a professor in astronomy and space sciences at Cornell University. Today, I'm going to talk to you about the universe and our human relation to it.
The most important question anyone can ask at any time is why there is a universe, why there is something rather than nothing. Perhaps this is immodest and arrogant, to think that human beings on this little planet, the Earth, will ever be able to answer such a question. Yet, haven't we made progress in the last few thousand years in understanding how nature works, from the ancient Greeks to the present time? And this progress, of course, is going to continue.
Now, today observations and measurements that we make of the sky, of the stars and galaxies, indicate that the universe has had a beginning 13.7 billion years ago, where a fireball explosion started and the universe began. We don't know exactly why this happened, but we can follow the evolution of the universe since that time to the present.
Part of this energy of the explosion was converted into particles, of quartz and electrons. The quartz quickly coalesced, combined, and formed the first protons and neutrons in the universe that form all the matter that we observe today. As this fireball continued to expand, it cooled. And within a few seconds, it cooled to millions of degrees. Within 100 seconds, the protons and neutrons were able to combine to form the light elements, like helium, beryllium, and lithium.
Then the universe continued to expand and cool faster. And some 300,000 years after the beginning, it had cooled enough to about 10,000 degrees or so, where now the electrons were able to combine with the protons to form the first hydrogen-- neutron hydrogen atoms.
Today, with our powerful space telescopes we have been able to map the sky the way it looked at that particular time. The universe continued to expand and cool. And today's fireball temperature has cooled to only three degrees above absolute zero. We now observe the whole universe is in a bath of three degrees temperature, but it is not entirely uniform. To a fraction of one part in a million, the temperature is slightly different from place to place, which indicates that at the beginning, these were the seeds of forming galaxies and clusters of galaxies.
Here you see that at the beginning there was nothing. A dark slide, an easy one to make. And suddenly, there was light. The Big Bang, which we still don't understand why it began. But soon after, here is a map of the sky where it's the background, what we called microwave radiation, the remnant of the fireball of the Big Bang, where the different colors that you see there are slightly different temperatures from place to place in the sky, by one fraction of a degree, one part in a million or so. These were the seeds that later on formed the galaxies.
And here you see a small part of the sky that we have mapped. And every dot you see there is a galaxy, like the Milky Way. Millions of them. In fact, in this small, little piece there are mapped 2 million galaxies. Take one little dot, that could be the Milky Way. And each galaxy made out of hundreds of billions of stars. The sun, remember, as we shall see, is just one star out of this immensity in the universe we observe today.
This photograph is taken with the Hubble Space Telescope. It's a deep photograph of the sky. And every object in it, except one which is a nearby star, is a far away galaxy, as big as the Milky Way galaxy, each one containing hundreds of billions of stars. It is a cluster of galaxies, where at the beginning they were clustered together. Some are large galaxies, some are smaller galaxies. Some have shapes, like elliptical galaxies. Some have spiral arms.
It is another cluster of galaxies. In the very center on the left, you can see huge elliptical galaxy. You also see some arcs around these galaxies. These arcs are a very important discovery. Albert Einstein, more than 100 years ago, taught us-- about 100 years ago-- taught us that when you have large masses, the influence of the mass is to curve space around it. And here you have huge massive galaxies, and their influence is to curve space around them.
Now, if you have some light that has to pass through that space, light cannot travel in a straight line but has to follow the curved space. Here you see those curves around the large masses, indicating indeed that space is curved. Very fine, Albert Einstein's General Theory of Relativity with a single beautiful photograph. If Albert Einstein was alive today, he would just jump up and down with joy. Very fine theory with a beautiful photograph taken with the Hubble Space Telescope.
At the beginning, galaxies were closer to one another when they formed by gravitational instabilities of breaking up the Big Bang material into clumps. And galaxies disturbed one another by gravitational pools and tides. Here are two galaxies, spiral galaxies. Strong, bright nuclei. They're trying to collide. Their gravity are going to bring them together and disturb the galaxies. Here are a couple more trying to collide.
Here are now some other spiral galaxies that the universe formed. Trillions of galaxies. The universe is trillions and trillions of galaxies. Sometime there is a bar coming from the center before the spiral arms begin.
Here is another beautiful galaxy that was zoomed in with the Hubble Space Telescope. Very far away. Sometimes the galaxies are inclined in the line of sight, so you see them incline in space. Some have spiral arms that are very open. Some are tighter in. There are flat systems, like pancakes. Some of them we see them from the top down, or bottom up, as you wish. And some of them we can see them in their equatorial plane.
Here is in other spiral. And there are galaxies all over the universe that we observe. Here is one that we see its equatorial plane, but it is somewhat warped because of nearby galaxies pulling on one side and disturbing the plane of the galaxy. Here is one that we see face on and interacting with a smaller irregular galaxy on its side. You can see how well the spiral arms are winding around the center of the galaxy as the galaxy rotates.
And this is almost an edge-on galaxy where you can see the spiral arms a little bit. And the dark band that you see in the middle, it is due to the dust that exists between the stars and the [INAUDIBLE] Primarily the dust that actually absorbs starlight. And as a result, it appears to us to be dark. We call this, by the way, the Sombrero Galaxy.
Here is another galaxy where you can see in the spiral arms there is a lot of activity. In fact, this is what we call a starburst galaxy. Many stars are being formed very quickly, almost at the same time. That is because another galaxy passed by, compressed the interstellar material at higher densities. It was easier to collapse the material gravitationally to form many new stars.
Now we're coming closer to the Milky Way, to our home in the universe. This is a nearby galaxy. And the dots that you see in the general photograph here are really stars in our solar neighborhood within the Milky Way. We photograph the outside of the Milky Way through the sea of the nearby stars.
This is another spiral galaxy and not very far away. And here is the closest galaxy to the Milky Way, the Andromeda Galaxy. This galaxy is 2 million light years away. That is to say, if you had a flashlight in the Andromeda galaxy and you wanted to say hello to us and you turn it on, light will have to travel 2 million years to get to us. It is that far away.
And the speed of light is very fast. It is 7.5 times around the Earth in one second. With that speed, a signal from the Andromeda Galaxy will take 2 million years to get to us, and that is the nearest galaxy. This is a vast and huge universe. So the light we see from the Andromeda Galaxy today, as we turn our eyes to the sky and our telescopes, really left the Andromeda Galaxy 2 million years ago. So it's all very old stories.
If this was the Milky Way, then the sun, with its solar system, will be about 2/3 of the way from the center to one side in one of the spiral arms, mixed up with millions of other stars, going around the center of the Milky Way Galaxy, once every 250 million years. The sun was formed some 5 billion years ago. So actually we have gone around the center of the Milky Way 20 times since the sun and the earth were formed.
This is a photograph of our neighborhood within the Milky Way galaxy, in our little corner of the galaxy, in one of the spiral arms where the sun is, moving around among all these stars that you see. The very central star you see is actually the closest star to the sun, Alpha Centauri. All the other stars are farther away.
We think today that most stars have planets around them, much, much smaller objects that are remnants of the formation of the stars from the collapse of interstellar clouds. Recently, with large telescopes and new techniques, we have been able to identify more than 250 planets around nearby stars. We don't seem to be alone in the universe.
Here is a constellation that we see with the naked eye, the Orion constellation, a winter constellation. Bright stars in the sky that we can see with our unaided eye, but we cannot take a photograph of the Milky Way like the other galaxies I showed you because we're inside it. So what we can do is take parts of the Milky Way, a photograph of a spiral arm, of another spiral arm, but put the picture together. And we know we are a spiral galaxy, very much like the Andromeda galaxy I showed you.
Different parts of the sky will show different parts of the Milky Way. You're looking at thousands and millions of stars in the spiral arms of the Milky Way. Here is a very busy area towards the center of the galaxy where you can see the millions of stars, but also you see between the stars some interstellar clouds. Clouds of dust and gas and molecular species.
Here is one, a large interstellar cloud. These are the factories where new stars are made in new planets. In our galaxy, we think from the collapse of interstellar clouds, about one new star forms every year. And the age of the galaxy is about 10 billion years old. So we've formed many stars and many more to come.
Here is another interstellar cloud we called the Rosetta clouds. You can see in the center, material has been emptied and new baby stars have formed, a cluster of stars. The sun was formed that way in the Milky Way about 5 billion years ago.
And then we wanted to see things clearer and we built the Hubble Space Telescope. And we put it out in space above the Earth's atmosphere so that we don't get the scintillating atmosphere disturbing the beautiful photographs and the images, the clarity of the sky that we want to see. And we had great hopes.
Unfortunately, when we made our first observations with the Hubble Space Telescope, it looked like that. This is a Van Gogh. It was a myopic sky. Unfortunately, the engineers had made an error of the mirror surface in the mirror and it didn't look very clear. It took us three years to find a way of correcting this myopic mirror by putting actually glasses to the telescope. The astronauts did that and successfully now we were able to zoom in into interstellar clouds and see things, as we hoped to, very clearly.
Here we see the extremities of an interstellar cloud where the densities are now very high. And sure enough, they're going to collapse soon to form baby stars. And we have explored many other interstellar clouds in the Milky Way. This is zooming in into the Orion cloud, the Orion nebula, where now you can see two or three pockets that gravitationally are collapsing, forming protostars.
We do understand quite well how stars form. We also understand very well how a star evolves. Stars evolve because they heat up in the center because of all the mass that is pushing down, and particles move very, very fast at temperatures of the order of 10 million, 15 million degrees. And as a result, they collide, and they fuse, and they cause nuclear reactions.
For example, hydrogen atoms, protons, get together to form helium. And as a result, they emit a nuclear energy, according to Einstein's famous equation that energy equals mass times the square of the velocity of light, E equals MC squared, that we call it. Energy then is released inside the star and flows out to keep the star stable-- and hot, for our benefit, of course, in the case of the sun.
But the nuclear fuel doesn't last forever. We calculate that a star like the sun can live about 9 or 10 billion years, but then it can exhaust its nuclear fuel and they die. When they die, they don't like it. They explode. This photograph here is a dying star that exploded in 1054 AD. We actually saw it. So human beings saw the explosion in 1054 AD. The Chinese astrologers of that time recorded these observations and they said it was so bright that they could see it for a month in the daytime. Big stars, bigger than the sun, will have these very energetic explosions. Now with large telescopes, we can photograph many remnants of these explosions. So we understand how stars die, and particularly large stars.
Here we can zoom in into some of the filaments and you can see how they radiate energy. We call this synchrotron radiation, a specific physical process that makes electrons that travel with very high speeds around lines of magnetic field. We know they will emit energy. And sure enough, we observe it.
Now, when stars are smaller, like perhaps the size of the sun, they also explode when they die. Like in this photograph here, the very central star you see is dying. About half of it has exploded out. And we have many such examples in the Milky Way galaxies, thousands of them. Many of the stars are older than the sun and they are dying right now so we can actually observe these explosions and study them very carefully.
It just so happens that this is part of my research. As a result, I have many beautiful photographs of these explosions taken with the Hubble Space Telescope, together with my students and my colleagues. We study the shape of the explosions, the plasma, and the atomic physics of it, because they radiate according to the laws of physics.
Here is another one. You can see the central star. Now it is contracting down, but half of it has exploded outwards. This is another one. You can see how symmetric is the explosion on both sides.
Let me say a word about colors here. The blue that you see surrounding the central star is very hot. It's of the order of 20,000 degrees. The green that you see is about 10,000 degrees. And the red is about 5,000 degrees. So these are temperature indicators.
As I mentioned, the explosions are very symmetric. We call this the butterfly explosion. What you see on the one side is almost mirror imaged on the other side. So the star really knows how to explode. We're trying to find out. The physics is very difficult, but we're making a lot of progress to learn how stars explode.
Look at this very symmetric object. Every aspect on one side is almost the same as on the other side. The star explodes in a very symmetric fashion. Here is another one that has exploded twice. And here is a new one that we have discovered recently with all its complexities.
And this looks like a firecracker here. The sun will do this, 4 or 5 billion years from now when it exhausts all its fuel or its nuclear fuel and will explode in this fashion. Well, by that time I hope human species will be much more intelligent and capable than we are today. They would have found another beautiful paradises in the universe and on other stars perhaps that will be more hospitable. We should not be around 4 or 6 billion years from now to see these explosions.
Join Yervant Terzian in a discussion of "why is there a universe? Why is there something rather than nothing?" and examine how humans think about their place in it.
This video is part 1 of 3 in the Cosmology and the Anthropic Principle series.
