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An Interview with Claude Canizares

by WKT
July 31, 2002 ::
Claude Canizares
Claude Canizares
July 31, 2002 :: Claude Canizares is Associate Provost and the Bruno Rossi Professor of Experimental Physics at the Massachusetts Institute of Technology in Cambridge, Mass., and is a Professor at its Center for Space Research. He is also a principal investigator on NASA's Chandra X-ray Observatory, leading the development of the High Resolution Transmission Grating Spectrometer.

Professor Canizares recently sat down to discuss results from Chandra that show that the Universe is filled with hot, diffuse material in between the galaxies. When added together, this material far outweighs all of the stars and galaxies and planets combined that can be seen in visible light. By probing this material, scientists hope to gain a better understanding of the structure and evolution of the universe.

Hot Intergalactic Gas
Illustration of Hot Intergalactic Gas
Q: Can you describe what is new about the Chandra results you and the other scientists have reported?
A: What Chandra has allowed us to do now is to actually probe [the hot, intergalactic material]. For the first time, shows the tip of the iceberg, if you like, and this says that there is a lot of material out there in between the galaxies that is very hot, but so incredibly diffuse that it simply had escaped detection before.

This is good news, because it means that we really understand this piece of the puzzle of what the universe is all about. We think we really have taken a major step now towards having a complete picture.

Q: Please describe the technique used to make this discovery with Chandra.
A: Chandra measures X-rays and the reason that measuring X-rays is important is that material we're looking for -- this very thin gossamer, or diffuse material between the galaxies -- is very hot. And the only thing it emits very feebly is X-rays, and the only thing it absorbs very feebly is X-rays from bright sources farther away in the universe.

Both of those techniques were combined in this series of studies to show that there is something there -- very diffuse, spread throughout space, very hot. But when added up, this hot gas accounts for more material by many times all the stars in all of the galaxies that we see with optical telescopes.

Q: Can you put this result into context in terms of the 'big picture' of cosmology?
A: I think the process of understanding the universe as a whole is very much like the parable of the blind man and the elephant, all trying to touch different parts of the elephant and trying to put together a picture of what the elephant looks like. There's never any single blind man that is going to have the complete picture. But every so often you get a significant new discovery like an ear or a trunk or, maybe even the whole body. In a sense, we have found a significant portion of the whole body, when it comes to understanding the matter in the universe. To me, that's why this is such an important discovery.

Q: Why are these results exciting for you personally?
A: One of things that's interesting about cosmology -- on the biggest scale and start with Copernicus -- is that there has been this long series of demotions that humankind has had to suffer. We're not the center of the Solar System, and we're not the center of the universe. When first dark matter and then dark energy were discovered, it became obvious that even the stuff we were made out of was a minor constituent in the universe. Now what we're saying is that even all of stars and galaxies and so forth are just a minor constituent of the 'normal' matter. That's sobering and that's a demotion, if you like. Maybe we can say that this means we're getting less and less significant.

However, the thing that inverts that and makes us the most significant is that we can understand all of this. Out of all of those other parts of the universe, we're the only thing out there that really has the knowledge to build a Chandra, to know what to look for, and how to look for it. So, we may be a small speck, but we're doing alright.

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