I've been thinking....

[[1ponders] (Paul)]

It'll be interesting to see how they finally do it, if they ever do.

[netwolf]

As i understand it Light is on the E side of the equation E = MC squared. Hence it has no mass. I dont see any contradiction there. Light photons are emited, when electrons move from a higher orbit to a lower more stable orbit. The photo electric effect is the inverse process.

The thoughts i have on the matter are that

1. Gravity of star increases the refractive index of space such that light curves.
2. The Refractive index is porpertional to the distance from the mass generating it. And hence falls away sharply. And hence you have a curved path for light around the Gravity field.

I could be wrong..

[[1ponders] (Paul)]

I like that idea netwolf. The refractive index of space(/time?). Proportional Distance squared, cubed to the fourth???

But, you could be right

[netwolf]

I recall one of my High School asignment that I did on Principle of Equivalence. I had just read at that time the book called "Relativity and Common Sense" By Herman Bondi. A very intresting read, and simple explanations to complex theories. But if you consider it Einstiens postualtions all came from his infamous gendaken "Thought Experiments". The train, the twins. Principle of Equivalence by comparing an Elevator and a Space craft.

Perhaps the fingerprint of the universe is within the mind, and it only requires thought to draw it out.

[[1ponders] (Paul)]

Ah now we come to the thought shaping the universe we live in. Being considered quite seriously in some circles these days.

[netwolf]

Hizenberg Uncertainty principle, the observer affects the observerd. Time is also affected by our consiousness of it, hence the old saying time flies when your having fun. I think we have moved the discussions into the relms of Metaphysics.. However no Science will withstand that does not asscess the bias of the observer.

[Sausageman (Mike Boggan)]

Can I take you back to Einstien's gravitational lensing?
If light is travelling in all directions, why do we see Einstien's Cross and not a halo effect around the star?
Surely the gravitational effect would affect light from every direction, not just from 4 points. Result: a halo.

Mike

[netwolf]

The Quasar may not be exactly in line with the Galaxy in line with earth. The symetry may not be perfect.

[slice of heaven]

Originally Posted by Mike Boggan

Can I take you back to Einstien's gravitational lensing?
If light is travelling in all directions, why do we see Einstien's Cross and not a halo effect around the star?
Surely the gravitational effect would affect light from every direction, not just from 4 points. Result: a halo.

Mike

http://spiff.rit.edu/classes/phys240...grav_lens.html
Explains it fairly well

[netwolf]

Ok so here you go a near perfect ring.
http://www.universetoday.com/am/publ...tein_ring.html

And another one from Huble..
http://antwrp.gsfc.nasa.gov/apod/ap980330.html

[janoskiss (Steve H)]

Great thread guys. A lot of topics touched on. Just a couple of quick points:

Light does "bend" due to gravity in the flat spacetime approximation suggested by our immediate experience, but in the spacetime of General Relativity, it merely follows the curvature of spacetime itself.

A body absorbing light will increase in mass, though the increase will be small. All forms of energy have mass; e.g., (all else being equal) a hotter body weighs more than a colder one, two hydrogen atoms have more mass than a helium atom (despite being made of the same particles), a moving car has (ever so slightly) more mass than a stationary one, etc...

[netwolf]

I like that litle saying all else being equal.. never worked out what should be equal to what..

The curvurture of space is analogus to the curvurture of the earth, it can not immedietly be seen it has to be understood. Our 5 senses are limiting in what they provide, but our brain has far more ability than we can fathom..

[janoskiss (Steve H)]

Originally Posted by netwolf

I like that litle saying all else being equal.. never worked out what should be equal to what..

Let me try to clarify with an example... Take a rock or some other macroscopic object. Measure its mass without disturbing it (e.g., measure its gravitational pull on something very small). Now heat the object whilst making sure it neither loses nor gains material (e.g., irradiate it with infrared or microwave light). Measure the mass again. If the measurements are precise enough, the second measurement will yield a larger mass than the first. The difference in mass will be equal to the heat energy gained by the object, as per E=mc^2.

"All else being equal" means simply that besides the temperature of the object being higher during the second measurement, nothing else is different; i.e., you have the same object and same amount of material; you didn't melt or boil the stuff (then its mass would be even more), it's the same arrangement of atoms but they're moving a bit more briskly.

Precision in language usually gets tedious and people tend to ignore me after a while most times I attempt it. So I often resort to somewhat vague expressions such as "all else being equal".

[netwolf]

Here is something to think about..
If the Solar system moves around the Galaxy, would it be possible to see the past Earth?
I mean to say if we have moved significantly from our location, could wee see our old light?? even as a woble around the sun..

[RAJAH235]

Steve, there's only one thing wrong with your eg. & that is, that every time you try to MEASURE anything,(electron's position etc), you influence the outcome, simply by introducing that external source/device. L.

[janoskiss (Steve H)]

That's why I said "macroscopic" object, L. ... system is large enough so that the uncertainty principle has no detectable consequence. The same energy-mass equivalence principle would still apply in the quantum world though, but that gets more tedious to explain and understand since us humans are not small enough to appreciate the weirdness quantum world directly. It all looks very deterministic from up here...

[slice of heaven]

Steve and Phil
You've both stated light can be affected by gravity other than the effect gravity has on space/time.
Can you give us proof of this ?
I'm not saying it doesn't or cant, as gravity does have an effect on massless objects.
Space and time are both massless (as long as the space is empty) and are affected by gravity.
Any examples??????

[netwolf]

Slice,

Have a look at this.. see examples at the end specificaly "Precessing Orbit of Mercury".
And also the bending of light was confirmed durin a Solar Eclipse in 1919, this was a prediction of Einstein's theory or spacetime curvurture caused by Gravity.

http://www-astronomy.mps.ohio-state..../Unit5/gr.html

[janoskiss (Steve H)]

Slice, One cannot really say that gravity affects spacetime, because there is no gravitational field or force in the classical Newtonian sense. In general relativity (which is the best description we have of gravitation and the large scale structure of the universe), space is no longer the canvas on which the world is painted. Instead the mass and energy content of the universe defines spacetime and determines its geometric structure. The resulting curvature of spacetime is what we experience and normally think of as a gravitational force one massive object exerts on another, but that is just a simplification useful in the reasonably flat spacetime of our immediate experience. To say space and time are massless is akin to saying something like verbs and nouns are odourless, or lengths are colourless. All true I guess but not very useful. Here is the Wikipedia entry on general relativity:
http://en.wikipedia.org/wiki/General_relativity... Lots more info there.