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GEORGE ELLERY HALE
GEORGE ELLERY HALE
USA (1868 - 1938)
George Ellery Hale was an American solar astronomer, born in Chicago. He was educated at MIT, at the Observatory of Harvard College, (1889-90), and at Berlin (1893-94). As an undergraduate at MIT, he invented the spectroheliograph, with which he made his discoveries of the solar vortices and magnetic fields of sun spots.
 

Enjoy these insightful and educational video clips drawn from over 70 hours of interviews with the world's leading figures in astronomy, shot during the filming of 400 Years of the Telescope.

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Lawrence Krauss

Einstein's blunder
Lawrence Krauss - Arizona State University

Shortly after Einstein had developed his general theory of relativity, there was a problem. Itís the same problem that Newtonís law of gravity has, and any physics student knows that gravity sucks. It always pulls, it never pushes.

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Lawrence Krauss

Empty space has energy
Lawrence Krauss - Arizona State University

Now, if you ask how much energy empty space could have, if you asked a four-year-old how much energy empty space should have, the four-year-old would say Ďnoneí. A good answer except the four-year-old hasnít taken quantum mechanics. And the point is that when you allow quantum mechanics to work together with relativity, empty space isnít empty at all.

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Lawrence Krauss

Energy density and our existence
Lawrence Krauss - Arizona State University

The fact that the energy of empty space is almost equal to the energy density of everything else in the universe today is, from a fundamental physics perspective, completely inexplicable. We donít understand it. And that has caused some people to think of an extreme solution. A solution which, if itís right, is equally depressing, at least to many physicists like myself.

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Lawrence Krauss

Expanding dark energy in an expanding universe
Lawrence Krauss - Arizona State University

The weird thing is that, if empty space is expanding exponentially as it does due to this repulsion produced by dark energy, and if empty space maintains a constant amount of energy per unit volume, and the volume is increasing, then it appears that youíre violating the law of conservation of energy Ė the total energy of the universe seems to be growing exponentially.

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Lawrence Krauss

Further observations on dark energy
Lawrence Krauss - Arizona State University

The discovery of dark energy was amazing. Now the question that really matters is, what is the dark energy? Is it a cosmological constant, like Einstein predicted, or is it some weird energy of empty space thatís changing in time and then may go away? The reason we care is that - first of all from a fundamental physics perspective - itís vitally important to know if empty space fundamentally has energy or if this is just some transient that is going to go away.

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Lawrence Krauss

How I came to my conclusions on dark energy
Lawrence Krauss - Arizona State University

When dark energy was first discovered Ė experimentally, observationally Ė it was discovered by looking at distant exploding stars and measuring, using them to determine the distance to distant galaxies and then measuring their speed and seeing that the expansion of the universe is speeding up.

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Lawrence Krauss

The enigma of dark energy
Lawrence Krauss - Arizona State University

One of the greatest revolutions in cosmology in the 20th century, if not in the entire history of cosmology, has been the discovery of what we call dark energy.

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Lawrence Krauss

Is our view of the universe right or wrong?
Lawrence Krauss - Arizona State University

The amazing thing is, our picture of the universe has changed a lot. So you could ask, 'could everything we know today be wrong?' And the answer is, potentially, yes.

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Lawrence Krauss

IYA Greeting
Lawrence Krauss - Arizona State University

Well, welcome to 2009, and the 400th anniversary of the invention of the telescope, which represented for me what science is all about.

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Lawrence Krauss

The large scale universe
Lawrence Krauss - Arizona State University

In the far, far future, when dark energy dominates the universe completely, all the galaxies that we now see will have moved so far away that we canít see them Ė theyíll be moving faster than the speed of light away from us and the rest of the universe will literally disappear and we will live in an island universe.

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