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WATCH: Ways of Knowing – Introduction to Cosmology

Professor Tim McKay introduces the fascinating field of cosmology, explaining how scientists use light to study the universe's history. He discusses the mysteries of dark matter and dark energy, the Big Bang's origins, and the potential for life elsewhere in the universe. Created by Big History Project.

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  • male robot hal style avatar for user Wudaifu
    I agree with L. Galina. Why should we be so eager to discover alien life? My concern is that our "discovering" alien life or having alien life "discover" us is going to be similar to the native inhabitants of Africa, Australia, Asia, South America and North America after they were "discovered" by Europeans. Don't be surprised if some future alien life "discovers" us only to exploit our natural resources or even use earth life as a food source. Remember that Twilight Zone episode called "Serving Mankind" that turned out to be a cook book.
    (15 votes)
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    • leaf grey style avatar for user Michœl
      I think the discovery of life on other planets (not necessarily super-intelligent beings life), even if it is just single-celled organisms, will go a long way in helping answer a lot of our big philosophical questions. Are we along in the universe? Are we unique? The discovery of any kind of life outside of our planet would open the possibility to a universe FILLED with life. There is so much distance between objects in the universe that interacting with other intelligent beings seems impossible, but knowing life in any form can exist outside of our planet would be, in my opinion, one of the biggest discoveries of human history.
      (7 votes)
  • blobby green style avatar for user L Galina
    Despite your claim (~), I submit that we do not NEED to verify the existence of life elsewhere in the universe; how do you justify such a claim?
    (4 votes)
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    • mr pink red style avatar for user jlcebrian
      Just before that point, he mentions that all the other phenomena, forces and laws we have found seem to be present everywhere in the universe. I think science would need a lot of revising if life happens to be unique to Earth, since its components are common, and present everywhere. So I read the affirmation as 'if we want to validate our current knowledge, we need to find life elsewhere'.

      You can read it as a generic affirmation (as in 'we humans just have an intrinsic need to increase our knowledge') which I find is still arguably true if you care for our long-term survival, but I think that was not the intended meaning.
      (11 votes)
  • piceratops ultimate style avatar for user Gabe W.
    There could be the case in which there is no life in the universe besides us, so you wouldn't have the moment to look forwards too. Of course how could we answer this question with a no? We, as humans which are naturally curious would keep on searching everywhere for eons!
    (5 votes)
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    • orange juice squid orange style avatar for user Caoimhe M
      i don't know if it will be possible, within the next century at least, to ascertain completely that there is no life at all besides us in the universe, because we can only observe such a small amount of what's out there, and not in any great detail. So while we may be able to find that there is no other life anywhere near us, that is not to say that there is no other life at all - it may be there, but so distant, and so different, from us that we don't discover it
      (1 vote)
  • hopper jumping style avatar for user I love football    ; )
    Why do they call it the Big Bang?
    (2 votes)
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  • orange juice squid orange style avatar for user Ala
    Wouldn't it be cool if we were the aliens. Like what if there is other life out there but its not yet as advanced as us? So to them we are the aliens and we are someday going to invade there home and destroy them, and then, what if when we finally do land on their planet, what should we expect, a warm welcome or war?
    (1 vote)
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  • blobby green style avatar for user Valentin Lavric
    If our planet originates from the Big Bang, how comes that light also coming from the early stages of the Universe is still behind us after so many billions of years?
    (1 vote)
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  • starky ultimate style avatar for user sirus
    Has the 'Big Bang' become the decided beginning of the universe?
    (1 vote)
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  • hopper cool style avatar for user Dawson Huynh
    Since the universe is so big, isn't there pretty much 100% sureness that there is more life in the universe?
    (1 vote)
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  • female robot ada style avatar for user Katey Gordon
    In the video its said that the speed of light is fast but not infinitely fast right now we only know that the speed of light is the fatest is there any theorys that there may be something faster then the speed of light?

    Also the discovery for life on on other planets are we all looking for specifics as we want to know there indeed is Intelligent life forms or are some looking for cellular life forms etc. ? My mind is wondering off into the far future but I can imagine as our ancestors traveled by boat to discover new lands ,species like mamals etc. I could see whether robotic or mandkind landing on mars or traveling through space on a spaceship and researching planets just thinking about new species that are intelligent like new animals imagine humans actually documenting these new exciting life forms etc. Our future is for sure exciting I could only imagine the future of science will have a deeper understanding. ....
    (1 vote)
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  • piceratops ultimate style avatar for user Eugene
    How do we know that 'everything that can happen should happen' @ ?
    I think I've heard this attributed to Einstein? Also sounds similar to Murphy's law.
    (1 vote)
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Video transcript

My name is Professor Tim McKay and I am a professor of physics and astronomy here at the University of Michigan where I study observational cosmology. The purpose of cosmology is to try and explain the origin and evolution of everything that's in the Universe from the earliest possible time all the way down to today. Cosmology is a very nice kind of historical science because we have the rare chance to see history. We actually get to see the Universe as as it was at different times and watch what happens in it. The way we do this is to take advantage of the finite speed of light. Light travels not infinitely fast, very fast, but not infinitely fast. And so, when we look at a distant object, we see it as it was in the past. The light has spent a long time traveling to it... to us, and when it gets here, we see light that left it a long time ago. If we look at a still more distant object, we see it as it was even farther in the past. So, when we're studying cosmology, we look at the light that has come to us from objects from the recent past, the more distant past, and the very earliest times by looking at things that are farther and farther away. This lets us see the evolution of the Universe from what it was like at the earliest times when we look at the most distant things all the way down to today. It's like the history of the Universe is laid out around for... around us for us to look at. Since we're gonna try and use the light that travels to us from very remote objects, we need to augment the minimal things that we can do just by looking at the sky with our eyes. And throughout the history of science, we found a whole series of different ways to improve people's vision. The simplest one is to put glasses on your eyes to give you a little bit better vision using still the eyes that you start with. A next stage of this is to build things like telescopes, telescopes that both magnify distant objects and make them appear larger than they would just to your eyes. But telescopes also let you collect more light than your eyes would. Your eyes have a very small aperture and let in only a little bit of light. Using a telescope like this is like having an eye that's about that big. But we've since made, of course, much bigger telescopes, telescopes that have eyes that are meters in size and the very largest telescopes that we use today have apertures of about 10 meters or about 35 feet. You can see much more distant, much fainter things with such a large telescope than you can see with just your eyes. And it's largely that improvement in instrumentation which has led to the great advances in cosmology and being able to understand the history of the Universe because with these instruments, we can see that history so much better than the ancient Greeks could looking at it with just their eyes. The reason I got into cosmology was a mix of interest and opportunity. I have always liked observing nature at every scale and in every way, from the time I walk down the street to when I'm using a super fancy scientific instrument. The reason I got involved in cosmology, though, is that I took a job at a place called Fermilab, a particle physics laboratory, and they told me I could do anything I wanted. And they were starting a new project there called the Sloan Digital Sky Survey and it was gonna observe so many things that it seems so scientifically rich, I couldn't resist working on it. So, I joined it then and I've been working on cosmology ever since. Observational Cosmology has had a really great 15 years because we now really know the basic history of the Universe from the Big Bang all the way down to today. It's been observed repeatedly, it's very well understood. But there remained some big mysteries and I'll tell you about just four important mysteries that remain in cosmology. The first has to do with the very earliest moments of the Big Bang. Everyone wants to know what was there before the Big Bang. Was there anything there before the Big Bang? How did it happen? Why did the Big Bang happen? What initiated it? Those are very difficult questions. We don't have much observational evidence about them. But everyone will always be fascinated by them. The next two big questions have to do with constituents of the Universe, with stuff that's in the Universe. There are two big mystery components to the Universe. The first is called dark matter and dark matter is a kind of material, a substance that seems to be very widespread through the Universe. There's more of it than there is ordinary matter, the kinds of atoms that we're made of. And it seems to be something that interacts gravitationally but never interacts with light. The other mysterious component of the Universe is something that seems to be causing accelerated expansion. The expansion rate of the Universe used to be slower than it is today. It's actually speeding up with time. We really have no idea what's causing it to speed up like that, what's causing accelerated expansion. But we've given a name to it even though we don't really know what it is. We call it dark energy. So, dark matter and dark energy are both very mysterious aspects of cosmology that we're hoping to understand. The fourth big question is, for me, the most intriguing question. We know that everything that can happen in the Universe should happen and should happen freely anywhere it's possible. And there's one thing that has happened here on earth that we've never seen anywhere else, and that's the emergence of life. Everything about our picture of cosmology suggests that if life could emerge here on earth, it should have done so freely in many places in the Universe. So, we need to find out whether that's really true. Our instruments right now are not quite capable of telling us whether there's life on other planets but in the next few decades, we should be able to settle that question with some level of confidence. And I really look forward to the discovery of life in other places in the Universe.