We now have evidence from many directions
that the universe is about 13.8 billion years old, beginning with an enormously spectacular burst of energy. And that energy transforming over time into a mix of matter and energy, and that matter becoming atoms, gas, stars, and galaxies. And then within these galaxies, generations
of stars producing heavier elements, those heavier elements enabled the formation of planets around stars. And then on at least one planet, we have life. We are very intimately connected with the rest of the universe
in a very practical way. Our bodies actually do contain atoms that were forged in stars. In fact, most of the elements that we are familiar with,
we don’t know how to create them originally other than in stars. So, it’s not us here and the universe out there.
We are all part of the same wonderful physical entity. Astronomy is an entirely observational science. What we do is
we can listen to the universe, basically through our telescopes. We can gather light from distant objects. And through studying light, we’re able to puzzle out the properties
of objects that we can never go to directly. There are many astronomers who study light from 10 billion years ago, and basically we are allowed to look back in time
through using our telescopes. So, telescopes are sort of like a time machine. Everything we look at, we are looking at it
as it was when the light began its journey to us. Astronomers use this wonderful time machine tool
to help us understand how the universe has matured from a burst of energy to a place
teeming with galaxies, stars, and planets. The early solar system was a very violent place
where planets were being formed and broken up constantly. We know that the planets form from a cloud of gas and dust. Where does this dust and gas come from? So, stars themselves are little factories that start with mostly hydrogen collapsed into a dense clump of gas. And then that pressure creates a fusion reaction in the core of stars
that can result in the production of heavier elements. Then when stars die, they actually release all of
that material they’ve created into the interstellar medium, and the next generation of stars incorporates
some of that richer material. So you have generations of stars that create
heavier and heavier elements. All of this has served over the 13.8 billion-year
history of the universe to enrich galaxies with more and more varieties of elements that
we now enjoy on places like planet Earth. The distances between things in our own solar system is tiny
compared to the distances between different solar systems. If you go to a football field and you have a beach ball
at the goal line, at about the 30 yard line, there will be a pebble. That’s the earth. At the other goal line is
maybe a golf ball, that’s Jupiter. If you travel from there to the other side of the earth,
from America to Russia, that distance would be one light year. And the nearest star is four and a half light years away.
And that’s our nearest star. We also see that the universe is still expanding. Space between galaxy clusters is growing. It’s not that these galaxies
are going out into empty space, but the space itself is actually expanding. So, we don’t really know a crisp answer to how big the universe is.
We know its age, and we know it’s enormous. And we know the content of the universe is enormous.
In the visible universe, there are something like 400 billion galaxies, and each galaxy can have hundreds of billions of stars.
So, it’s mindboggling. As we are realizing more and more the enormous size and
scale of the universe and its enormously rich content, it begs the question of whether there could be
life outside our own solar system. If you had asked me 10 years ago how common are small,
rocky planets like the Earth, I would have said we really had no idea. Humans have been asking
that question for hundreds, arguably thousands of years. What’s so exciting is that we are the first generation
in human history that actually can answer that question. An exoplanet is a planet that orbits another star, and we really didn’t know anything about exoplanets about 20 years ago and that situation has changed dramatically. In the last ten years, we had something called the Kepler Space Telescope which allowed us to focus on one particular part of the Milky Way.
Very, very narrow field, but study it very intently. At this point, astronomers have found about 5,000 planets
orbiting many different stars throughout the galaxy. Because of all these planets, there’s a lot
of speculation that life might be common. Why should Earth be the only place where there’s life? So, it certainly seems in some sense just by the statistics
that life could be very common, at least simple life. An active, current question is what is the
minimum set of things you need to measure to really conclude that the only explanation is life? And it may be that there’s other molecules, such as methane,
directly seeing that there are liquid oceans, maybe seeing the green, the photosynthetic color.
But is that enough? Will we ever be able to make a conclusive statement that we really know that there’s life on another planet? I do think in the next even 10 years,
it’s possible we’re going to answer that question. And of course, these are just the scientific questions. There are the bigger philosophical questions of why capital W,
why is life existing and is there purpose in it? Those are the kinds of questions beyond
the tools of our microscopes and telescopes, but this type of science does beg all
these interesting types of questions. Astronauts have commented on looking back at Earth from space, it gives them an entirely new perspective when they see all of humanity in one unified space. I think you can have a similar reorienting
experience looking the other direction. Looking out in the larger cosmos and realizing
that we are a tiny part of an extraordinary system. I had a little telescope I’d take up country and
everybody in the village would come out and they’d look through the telescope and see the craters on the moon,
or the rings of Saturn, and they’d go, “Ooh and ahh,” just like my family and friends back in Michigan do. And it finally hit me – this is what makes us human,
this ability to look at the sky with wonder.