Earthsky
Private: Flipping through the “photo album” of the cosmos
05-05-2006 - Uncategorized
“Avi Loeb”:http://cfa-www.harvard.edu/~loeb/ is a theoretical astrophysicist at Harvard University. He wants to know what makes the universe tick. He wonders, how did the first stars form? What causes mysterious explosions in space called gamma-ray bursts? Can we detect planets by looking through so-called “gravitational lenses”? Where do the magnetic fields between galaxies come from? Avi Loeb spoke with Earth & Sky’s Jorge Salazar.
*Salazar:* What’s known about the first stars of the universe?
*Loeb:* At the moment, we have a photo album of the universe. We have an image of what the universe looks like, only about half a million years after the Big Bang. This is in the form of the cosmic microwave background, the leftover radiation from the Big Bang. So we have an image of when the universe became transparent, we can see this relic radiation.
We also have, using the big telescopes, images of the universe out to when it was about a billion years old, and later. But we are missing some pages of this photo album of the universe. Basically, we know what the universe looked like as an infant, and we also know what it looked like as an adult, more than a billion years after the Big Bang. But we are missing some pages, between half a million years and a billion years. We haven’t yet imaged, we haven’t seen the universe in this intermediate epoch. And it’s very important, because that’s the time when an infant grows and becomes an adult. So if we want to understand the big galaxies, like the ones that we are residing in, the Milky Way galaxy, we really have to image this very early epoch. Only then will we have a complete photo album of the universe.
*Salazar:* How does thinking about astrophysics, things like the first stars and galaxies ever to form, how does that translate into your everyday life?
*Loeb:* It puts things in perspective. You just look up into the sky at night and you see all of these stars and you wonder if maybe we are too preoccupied with ourselves, that there is much more out there, and we should think about it every now and then. If you look at animals, they are not even aware of what is outside of their area of where they live. We are aware of it, of what happens around the globe. But we don’t often think about beyond the Earth.
As an astrophysicist, I have the privilege of being paid for thinking about these things. And it’s a great experience, and it puts things in perspective for me. There are things that I would be otherwise bothered by, my own death, for example. Everyone will die at some time, and it’s obvious that this will happen. But when I see the universe as a whole, it’s giving me a better sense of longevity. I don’t care so much about myself as much as I would otherwise, because I see the big picture of what is going on. When you see the picture and the wonderful images that are produced, for example, by the “Hubble Space Telescope”:http://hubblesite.org/ and other telescopes from the ground, you feel much more humble about your successes and your failures.
*Salazar:* How do you know what’s true in the world, who or what to trust?
*Loeb:* Personally at a young age I was mostly interested in philosophy, because it deals with the most difficult and the most fundamental questions that we address. But the problem with philosophy is that you don’t have the scientific tools of answering these questions in the way that everyone else who is addressing these questions would agree with you. And the nice thing about science is that there is this way of making progress.
At a later age, in my twenties, I was very much attracted to science because of that. And one thing led to another, and then I ended up in astrophysics. As a young person, I was not particularly attracted just to astrophysics. I was attracted to science more generally. As an astrophysicist, that sort of closed the circle for me, because we are addressing some of the fundamental questions that people try to address over the centuries in philosophy, but we are doing it with scientific tools. We have a world model that is based on scientific evidence and scientific tools. And that is perhaps the greatest triumph of the past century, that we developed this model about the universe, which is supported by so much data. And we can be confident that these things happened in the past. And to get the evidence you just need to attend an introductory course in cosmology in any university and you will get most of the information that I am referring to.
*Salazar:* Earlier you mentioned the photo album of the universe, and how we’re missing a few pages from the beginning. Do you think the universe itself will ever be a closed book, something completely known and understood?
*Loeb:* What we can definitely have is a photo album of what happened in the past. Then we can make some predictions about what will happen in the future. But until we see the history unfold, we don’t know if that will be the case. So there will always be an open question about the future. And actually, I should say that the universe started without having us in mind. We are made of mainly water, for example, and water contains oxygen. Oxygen was not produced in the Big Bang. It was produced inside stars, after stars started to form in the universe. We are an afterthought. After a while, planets formed, and then on this planet we know there is life and we exist. So we came into the scene relatively recently.
The interesting question is what will happen to us in the future. And the most conservative prediction for the future is that the universe will expand much more rapidly in the future, its expansion is accelerating. And we will be left alone in a vast vacuum with a cold universe surrounding us. But until we see that happening, we will not know for sure if that will be the case. There are some interesting questions that people are talking about right now, about what happens outside of our universe. We can only see out to some distance. And that’ s the distance that is traversed by light, that light can propagate since the Big Bang. And we cannot see farther than that, because it takes some time. So all we can do is speculate about what happens outside the volume that we can actually see. And these are questions that we might never be able to answer, because we cannot really see outside of our universe.
_Avi Loeb is an astronomy professor at Harvard University and a member of the Institute for Theory and Computation of the Harvard-Smithsonian Center for Astrophysics._