Death of John Wheeler

I was going to post that, but figured someone else would have already. Sure enough.

Speaking about black holes,... if light has no mass as they claim, then how can the extreme gravity of a collapsed star, or black hole, pull on the light, holding it back, if light has no mass? Is it holding back on the photons? How, if they have no mass?
 
Iamme said:
I was going to post that, but figured someone else would have already. Sure enough.

Speaking about black holes,... if light has no mass as they claim, then how can the extreme gravity of a collapsed star, or black hole, pull on the light, holding it back, if light has no mass? Is it holding back on the photons? How, if they have no mass?
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They have no rest mass, but they aren't at rest, so they have mass.
 
ErkDemon said:
Ack. I really enjoyed reading his old paper on geons.
Still, I suppose that 96 is a good innings.
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Yep, it sure is a good innings, and he used it so well, taught so many good students, ... what a glorious life.
 
A brilliant man and a brilliant career.

John A. Wheeler

“If you haven't found something strange during the day, it hasn't been much of a day.”

“We live on an island surrounded by a sea of ignorance. As our island of knowledge grows, so does the shore of our ignorance.”

“Time is what prevents everything from happening at once”
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Iamme said:
....Speaking about black holes,... if light has no mass as they claim, then how can the extreme gravity of a collapsed star, or black hole, pull on the light, holding it back, if light has no mass? Is it holding back on the photons? How, if they have no mass?
Click to expand...

My understanding is that space-time is curved by mass, which provides a force we call gravity. Everything that is not being accelerated by another force travels in a straight line. A massive object causes a curvature in space itself, and the straight line turns out to be a curve. So light curves along this path.

In earth's gravitational field we don't notice this curvature for light because it is traveling so fast. It's like a rifle bullet traveling faster than a baseball. The bullet falls just as far in 1 second as the baseball does, but the bullet travels further in that 1 second.
 
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We will not forget you, John Wheeler.

I exchanged a series of letters with Wheeler when I was about 17 and 18. It's not every brilliant scientist who will talk seriously with an ignorant kid.

~~ Paul
 
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I've read a bunch of John Wheeler, as well as others, and he had been consistently easy to understand. A great scientist.

Apropos to the stuff about light travelling in a straight line, see this picture of light travelling through the cosmos:
http://antwrp.gsfc.nasa.gov/apod/ap080330.html
 
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Olowkow said:
My understanding is that space-time is curved by mass, which provides a force we call gravity. Everything that is not being accelerated by another force travels in a straight line. A massive object causes a curvature in space itself, and the straight line turns out to be a curve. So light curves along this path.

In earth's gravitational field we don't notice this curvature for light because it is traveling so fast. It's like a rifle bullet traveling faster than a baseball. The bullet falls just as far in 1 second as the baseball does, but the bullet travels further in that 1 second.
Click to expand...

A fair summation to some extent, but a little off point, what relativity demonstrated is that gravity is a fictitious or inertial force. Like the Coriolis force or centrifugal force. It is not that light is traveling so fast in a weak gravitational field, it is that the space time curvature is essentially flat in that field so that light (the observationally defining space time element) or other weakly gravitational coupled elements continue on an apparently straight path. It is not velocity but mass or energy that determines ones generation of and interactions with gravitational fields (dark matter and dark energy not with standing, at least for now). I wish I could explain it as eloquently and completely for you as Wheeler might, but I am no where in his league.
 
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