Thursday, April 26, 2007

Hawking Closer to the Sun


Our Sun imaged by STEREO, the Solar Terrestrial Relations Observatory. The twin STEREO spacecraft allow 3-D images of the Sun and surroundings. Best wishes to Stephen Hawking, for today was the day of his long-awaited zero-G flight. Desire to slip the surly bonds of Earth is far older than humanity, as symbolised by Icarus' flight. Hawking's biggest discovery may have a lot to do with the Sun.

There are many unsolved mysteries about the Sun. The temperature of its surface is thousands of degrees, yet the corona is millions of degrees. The corona is laced with magnetic fields which contribute to its high temperature. The sunspots which Galileo saw mark the locations of magnetic field lines. Solar flares related to sunspots affect communications on Earth and could be a great hazard for interplanetary flights. Solar variations are part of the debate on Earth's climate. Though life on Earth depends on the Sun, we are far from understanding it.

According to the standard solar model, when Earth was formed the Sun shone with only 70% of its present luminosity. Earth’s surface would have been frozen solid, making evolution of life very unlikely. Geology and the fossil record contradict this prediction. The very appearance of life on Earth conflicts with the model. This conflict with observations was the Faint Young Sun paradox. Because the Sun turns fuel into energy according to E=mc^2, change in c precisely accounts for this paradox. If c had not changed in precisely the amounts predicted, life would not have evolved to read this post.

Hawking's biggest discovery was that Black Holes are not completely black--they tend to radiate as blackbodies. Hawking first presented his results in a talk entitled "Black Hole Explosions?" When he had finished, the moderator said, "Sorry Stephen, but this is absolute rubbush." At least Hawking was allowed to finish. Within a few years people realised that Stephen was right, and scientific fame followed.

One big mystery about the Sun is how it formed in the first place. We know that stars form from collapsing disks of gas, but how the fusion reaction begins has been a complete mystery. If the gas cloud were heated, it would dissipate before a sustained fusion raction could begin. The disk's angular momentum would also be carried off into Space. Something else is needed to trigger a cloud's collapse into a star.

If tiny Black Holes collided with a gas cloud, they would not suck everything up. The tiny amount that they did eat would produce an immense amount of Hawking radiation. Heat and the gravitational pull of a singularity would ignite a star and keep it steadily burning for billions of years. A Black Hole could exist in the second last place humans would look for one, in front of our face each morning.

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5 Comments:

Blogger Kea said...

Heh, heh! It sounds like he had a lot of fun! And this simple aircraft venture is something many could afford.

5:52 PM  
Blogger QUASAR9 said...

Hi Louise, Interesting a tiny blackhole inside the Sun

I hear if we were to travel to the centre of the earth (and there is no tiny blackhole) we would experience a sort of weightlessness, since the gravity all around - all things being equal - would pull us with equal strength in all directions

6:48 AM  
Blogger QUASAR9 said...

PS - If Hawking had his way
he'd probably live in a zero gravity bubble
at the moment his body feels like it is being drawn not just by earth's gravity, but the gravity from some massive tiny blackhole inside his shell.

6:50 AM  
Blogger L. Riofrio said...

Nice to hear from both of you. Q9, being at Earth's centre night be a lot like Hawking's flight, only hotter.

6:53 AM  
Blogger nige said...

It's on the news that Hawking has just been in zero gravity. See http://www.theregister.co.uk/2007/04/27/hawking_flies/

Hawking amazed by weightlessness

By Lucy Sherriff

Friday 27th April 2007 14:04

Stephen Hawking is back on solid ground after completing eight "zero gravity" plunges aboard the vomit comet.

In total, the professor spent around four minutes weightless. On his return, he described the experience as "amazing", proving that even a genius can have his vocabulary humbled by free-fall. "The zero-G part was wonderful and the higher-G part was no problem. I could have gone on and on," he told the BBC.

"Space here I come," he added, referring to his plans to fly aboard one of Richard Branson's first Virgin Galactic sub-orbital flights, which are slated to start in 2009.

Peter Diamandis, chairman and CEO of Zero Gravity Corporation, the firm that took Hawking up on the specially modified Boeing 727, said that the flight had been beyond all their expectations.

"The doctors felt he was in tremendous condition. His heart rate, blood pressure, oxygen levels were all normal and perfect," he said.

You can have a look at the good professor spinning like a turbine here on YouTube. ®

4:30 AM  

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