mass affecting light

[bl4ster]

I was watching posts about mass affecting space-time and things like that,and i found a variety of answers,but i didnt saw anyone explaining it totaly.

So by my opinion best explanation for this is:if we imagine a space like a trampoline that has no middle part.When we drop heavy object like bowling ball it bends trampoline and all the small balls fall to the recess what the big ball made.But if they have speed they wont fall closer to the middle.But why does the light curves? Well again imagine trampoline and bowling ball,and put a laser at the flat part of trampoline.Beam wont follow the hollow,but to

the object that is in the hollow it is going to look like the beam has curved,while it remained straight.My conclusion:light beam stays flat,and objects are irregular.

Sorry for grammar!

Whats your opinion?

[ajb]

The usual understanding is that light beams follow very special paths called null geodesics (also seehere).

 

These paths are an analogue of "straight lines" on spaces (or space-times) that have a non-trivial local geometry, i.e. "curved".

[timo]

My opinion is that the Einstein equations, which are in principle supposed to determine the geometry of spacetime as caused by the mass in it, in conjecture with the geodesic equations, which describe the movement of objects (including light) in a given spacetime geometry, do explain the effect totally. I don't quite see what you consider missing.

[bl4ster]

To us light seems curved and objects with great mass normal,and i think its the opposite,light stays intact while "objects bend" space near them.

Its because i was reading some article about mass curving light beam.I googled it and found some resarches about objects curving light beams and Einsteins gravity lensing,so i put my opinion here to see what you are thinking.

 

I was also watching Michio on Sci-Fi and he said he would curve laser beam with magnets? Is it possible to bend light beam with magnets?

[immortal]

 

 

Let us assume an accelerating frame since an appropriate accelerating frame is nothing but a gravitational field. Here the Observer is placed in an elevator and is accelerated upwards and he sends a beam of light on the wall of the elevator. For an Observer who is in a inertial frame outside the elevator the light would appear in a straight line but for the Observer on the elevator the light beam will bend downward. It is because the Observer has a record of the beam at different times and he recieves the reflected light from the beam at the same time and hence those light which are far away from the Observer will leave its position earlier than the light which is nearer to the observer and therefore the beam appears to bend downward as shown from the first figure. (Since it has to travel more distance it takes more time and therefore moving clocks run slower). The light is bent just as any other object.

 

Now if we assume that the light stays flat and it is the object that is bent then the following situation is shown in the second figure. Since the Observer on the elevator is at rest with respect to the walls or the object there can not be any distortion to the object. The situation can not be realized. So the frame of reference of an Observer will determine the nature of the event to an Observer and the laws of nature have the same form in any reference frame. Therefore light is indeed bent by the gravitational field as seen from the point of view of an Observer from an accelerated reference frame which is equivalent to a gravitational field.

Edited May 4, 2011 by savithru

[bl4ster]

For an Observer who is in a inertial frame outside the elevator the light would appear in a straight line but for the Observer on the elevator the light beam will bend downward.

Observer inside sees bended light and from outside it looks normal.What if we assume that observer/whole elevator has also been bended due acceleration/gravitational field?

And i was thinking about light going pass objecs(cause theory was that a object with a great mass bends light that passes near it) not from them like this light inside.

[immortal]

Observer inside sees bended light and from outside it looks normal.What if we assume that observer/whole elevator has also been bended due acceleration/gravitational field?

 

When the elevator is accelerated to speeds near C say around 0.8c and it passes at those great speeds relative to the observer who is outside then the whole elevator will appear distorted but an Observer who is inside doesn't observe any distortion of the object, as he is at rest with respect to the object(elevator). Hence space-time is relative to an observer, it is space and time which is altered to keep the laws of physics same in all inertial frames and also since the speed of light is constant.

 

"Therefore light is indeed bent by the gravitational field as seen from the point of view of an Observer from an accelerated reference frame which is equivalent to a gravitational field."

Light is no more than any other freely falling object and therefore it takes a path as dictated by the curvature of space created by a body of large mass or for an observer who is in an accelerated reference frame.

 

And i was thinking about light going pass objecs(cause theory was that a object with a great mass bends light that passes near it) not from them like this light inside.

 

The theory also says that any gravitational field can be easily substituted by an accelerated frame. So is the reason for me to choose this elevator case as a model to easily comprehend the theory.

[bl4ster]

->I was also watching Michio on Sci-Fi and he said he would curve laser beam with magnets? Is it possible to bend light beam with magnets?<-

What about this?

[immortal]

AFAIK, magnetic fields are capable of accelerating charged particles (bending them or driving them in a parabolic motion) but photons are not charged particles and magnets can not bend light beams.

 

I think what Michio Kaku might be talking about (in his book 'Physics of the Impossible') is 'magnetic metamaterials' which is used to bend light rays by electromagnets which interact with the magnetic field of the light. Remember it is not the magnets which is bending the light rays in the literally sense rather the incident light carrying a magentic field of its own induces an electric current in the materials and therefore kicks in a chain of interacting magnetic fields oscillating at different frequencies in the artificial material and there by we change the magnetic and electric field of light waves and we can control its flow or the direction of its momentum.

 

nano-magnets interacting through the magnetic field of light

 

Journey of Invisible cloaking devices