Why light is bending?

[alpha2cen]

Everybody knows well light is bending when it passes nearby the very big mass star.

But photon has no mass.

Why light is bended by very big gravity star?

Any related equation about it?

Edited December 29, 2010 by alpha2cen

[timo]

Of course. The Geodesic Equation. The mass doesn't even explicitly appear there. What does appear though is the connectivities (edit: I am not completely certain that "connectivities" is the correct English term; WP seems to call is "connection coefficients"), usually called [math]\Gamma[/math], which describe the local structure of spacetime (in the current coordinates), and can be considered something akin to the gravitational field in Newtonian Gravity.

Edited December 29, 2010 by timo

[Janus]

Everybody knows well light is bending when it passes nearby the very big mass star.

But photon has no mass.

Why light is bended by very big gravity star?

Any related equation about it?

 

But light does have energy and momentum and in GR these also contribute to gravitational interaction.

[alpha2cen]

If gravity affected electromagnetic wave forward direction, it would possible to control the gravity by using electromagnetic waves. When we pass through the big gravity place, we can easily pass that place by using electromagnetic wave emitting apparatus. If there were no interaction between electromagnetic wave and gravity, the light passing experiment would be something wrong.

Edited December 30, 2010 by alpha2cen

[Janus]

If gravity affected electromagnetic wave forward direction, it would possible to control the gravity by using electromagnetic waves. When we pass through the big gravity place, we can easily pass that place by using electromagnetic wave emitting apparatus. If there were no interaction between electromagnetic wave and gravity, the light passing experiment would be something wrong.

 

This makes absolutely no sense whatsoever. It does not follow that if electromagnetic waves are subject to gravity, then electromagnetic waves can control gravity. Billiard balls are subject to gravity, but a "billiard ball emitting apparatus" would not allow us to control gravity.

[alpha2cen]

This makes absolutely no sense whatsoever. It does not follow that if electromagnetic waves are subject to gravity, then electromagnetic waves can control gravity. Billiard balls are subject to gravity, but a "billiard ball emitting apparatus" would not allow us to control gravity.

If gravity had an attraction force of the electromagnetic waves, this relationship should be existed.

We assume there is an object which is surrounded by electromagnetic waves.

How about this relationship?

Total gravity attraction force = electromagnetic wave attraction force + object attraction force

But problem is which pattern electromagnetic wave is related to the gravity. The parameter is like this, such as intensity, wavelength.

If Sun had attraction of electromagnetic waves, this wave, sun emitting wave lengths, would be very effective for reducing gravity.

[Janus]

If gravity had an attraction force of the electromagnetic waves, this relationship should be existed.

We assume there is an object which is surrounded by electromagnetic waves.

How about this relationship?

Total gravity attraction force = electromagnetic wave attraction force + object attraction force

But problem is which pattern electromagnetic wave is related to the gravity. The parameter is like this, such as intensity, wavelength.

If Sun had attraction of electromagnetic waves, this wave, sun emitting wave lengths, would be very effective for reducing gravity.

 

Absolute nonsense.

[alpha2cen]

Absolute nonsense.

 

Think about this case.

The case when you play a rope pulling game with other people. The moment when someone is pulling the rope, you give him sufficient rope cord, then what happen? Your rope tension is lower than before.

Electromagnetic emitting is the same concept.

Important thing is that gravity attracts electromagnetic waves or not.

Edited December 31, 2010 by alpha2cen

[alpha2cen]

This does not have the rule, but see the rocket which is leaving the Earth.

The end of the rocket emits electromagnetic waves - light.

The rocket power would be roughly proportional to that temperature.

At any rate, the thing that gravity attracts electromagnetic wave or not is important.

[lemur]

Don't lower frequency wavelengths bend more through a prism than those of higher frequency? Doesn't that also suggest that the lower frequency waves follow a more curved path as the higher frequency ones? Could that also be related to the greater amount of power in the higher frequency waves?

 

Also, since every action has an equal and opposite reaction, I would think that the bending of light would have the counter-effect of straightening spacetime-curvature for other nearby photons. I.e. a lower frequency wave traveling near a higher frequency wave could follow a straighter path than it would if the higher frequency wave were absent. Has this already be observed/tested?

[swansont]

Don't lower frequency wavelengths bend more through a prism than those of higher frequency? Doesn't that also suggest that the lower frequency waves follow a more curved path as the higher frequency ones? Could that also be related to the greater amount of power in the higher frequency waves?

 

In general, index increases with frequency (it's not true near an absorption resonance). The path isn't curved and this has nothing to do with gravity.

[IM Egdall]

If gravity had an attraction force of the electromagnetic waves, this relationship should be existed.

We assume there is an object which is surrounded by electromagnetic waves.

How about this relationship?

Total gravity attraction force = electromagnetic wave attraction force + object attraction force

But problem is which pattern electromagnetic wave is related to the gravity. The parameter is like this, such as intensity, wavelength.

If Sun had attraction of electromagnetic waves, this wave, sun emitting wave lengths, would be very effective for reducing gravity.

 

The key here is energy. The frequency of the electromagnetic (light) wave is proportional to its energy. (E = hf where E is energy, h is Planck's constant and f is frequency.) So light has energy. And the presence of energy produces spacetime curvature (gravity). But gravity is additive. So the light emitted by the Sun, for example, adds to the gravity in its neighborhood.

[Janus]

Think about this case.

The case when you play a rope pulling game with other people. The moment when someone is pulling the rope, you give him sufficient rope cord, then what happen? Your rope tension is lower than before.

Electromagnetic emitting is the same concept.

No, it isn't

Consider two people holding on to a rope while swing in a circle. If one or the other let's up on the tension, you will separate some. This is because you reduced the centripetal force but not their mass and momentum.

 

Now imagine an object in orbit around another. It releases electromagnetic waves. While the release of these waves will slightly reduce the mass of the object and thus its gravitational attraction to the other, However, at the same time you are reducing the mass and momentum of the object. This loss of momentum exactly compensates for the lessening of the gravitational attraction, and the orbit does not change.

 

A case where "throwing weight overboard" would be on any help would be a rocket climbing out of a gravity well. Lessening the mass would decrease the needed thrust. But as I alluded to in an earlier post. Throwing that weight overboard in the form of billiard ball, would work just as well as throwing it overboard as electromagnetic radiation. (In fact, it would make more sense to throw out the billiard ball. To get the same effect from electromagnetic radiation you would have to convert a billiard ball's mass worth of matter to energy. So just toss out the mass without messing with the conversion.)

 

But even then, it's a pointless exercise. If your rocket had extra mass that was there just for the purpose of being thrown overboard, you would be much better off just leaving it off the ship in the first place.

 

 

Important thing is that gravity attracts electromagnetic waves or not.

 

No, it isn't.

 

This does not have the rule, but see the rocket which is leaving the Earth.

The end of the rocket emits electromagnetic waves - light.

The rocket power would be roughly proportional to that temperature.

 

No, the thrust would be proportional to energy output. The temperature would be related to the wavelength of the light emitted. You could get the same thrust by outputing the same energy at different frequencies and temperatures.

 

At any rate, the thing that gravity attracts electromagnetic wave or not is important.

 

It is of no consequence at all. Once the light is emitted, how it interacts with the Earth via gravity has no bearing on the rocket. The only gravitational consequence is the loss of mass in the ship due to the mass equivalence of the emitted light. But you get that same effect from a standard chemical rocket. The mass of the exhaust gasses are removed from the ship, decreasing its mass as time goes on. IOW, there is nothing special about light's gravitational interaction that would affect this situation.

 

The only advantage using light emission as a rocket has is that the exhaust speed is very high which increases efficiency. The downside is that because the momentum of a photon is very small, it is very hard to produce enough light to generate any significant thrust.

[lemur]

So light has energy. And the presence of energy produces spacetime curvature (gravity). But gravity is additive. So the light emitted by the Sun, for example, adds to the gravity in its neighborhood.

So if the gravitational field of a star is extended beyond the majority of its matter due to radiation-density, does that "smooth" the topography of the star's spacetime-curvature? In other words, if you compared the curvature of spacetime surrounding two stars of equal mass but very different levels of energy-output, would spacetime curve more (and more abruptly) around the one emitting relatively little energy?

[alpha2cen]

Important thing is that gravity attracts electromagnetic waves or not.

No, it isn't.

 

Then, how we explain Black hole phenomena?

On the surface of the Black hole, researchers say, electromagnetic wave, light, is absorbed.

No light is emitted from there, either.

Another related phenomena is every stellar behavior is related to electromagnetic wave attraction by it's gravity.

If your saying were right, we would have to rewrite this part of paper again.

From the beginning my point is photons have no mass, but they are attracted by gravity.

It confues us like Higgs boson.

Edited January 1, 2011 by alpha2cen

[swansont]

Janus isn't saying that EM waves are not affected by gravity. His negation ("No, it isn't") referred to your claim that this was important to your hypothesis that we can control gravity. Your hypothesis is false, so gravity's effect on light is not important.

[alpha2cen]

Janus isn't saying that EM waves are not affected by gravity. His negation ("No, it isn't") referred to your claim that this was important to your hypothesis that we can control gravity. Your hypothesis is false, so gravity's effect on light is not important.

 

Happy New year Mr. swansort

.

So we can say like this.

.

Light is affected by gravity.

.

But gravity is not affected by light.

.

Is this right?

Edited January 1, 2011 by alpha2cen

[swansont]

Depends on what you mean by "gravity is not affected by light." As Janus pointed out way back in post #3, light has energy and momentum, and is a source of gravity. Since you have continued past that with other hypotheses, one assumes that you mean light has some other effect, above and beyond that contribution. It doesn't.

[alpha2cen]

On the surface of the Sun, solar lay leaves the surface.

 

That means the light's repelling force against the Sun is bigger than attraction force of the Sun.

Why the light from the far away star is bended by the solar gravity?

Does the unseen particles or electromagnetic waves around the Sun affect the bending event?

Near the sun light density is very high. And solar charged particle concentration is high, too.

 

[lemur]

It seems like gravity-field modeling fails to pay attention to interactions between/among conflicting/competing gravitation. What I mean by this is that we know, for example, that gravity cancels itself at the center of the planet but outside of the center, that effect is not really considered. I think it is called a lagrangian point where two gravity-fields interact to produce a zero-gravity point not drawn into either gravity-well, but shouldn't every point in every gravity well be determined by all interacting fields present in the region? Likewise, shouldn't all energy be taken into account in describing/defining a given gravitational field-topography?

[swansont]

It seems like gravity-field modeling fails to pay attention to interactions between/among conflicting/competing gravitation. What I mean by this is that we know, for example, that gravity cancels itself at the center of the planet but outside of the center, that effect is not really considered. I think it is called a lagrangian point where two gravity-fields interact to produce a zero-gravity point not drawn into either gravity-well, but shouldn't every point in every gravity well be determined by all interacting fields present in the region? Likewise, shouldn't all energy be taken into account in describing/defining a given gravitational field-topography?

 

No, it doesn't fail to do that. In Newtonian terms, you do add the forces together.

[lemur]

No, it doesn't fail to do that. In Newtonian terms, you do add the forces together.

I have also read that Newton described gravity, and I think force in general, as net force. What I don't understand is why I don't usually get the feeling that force fields are viewed in terms of interactions and overlaps. It seems as though force-fields are always treated as a context in which some other object expresses the force. Yet isn't any object influenced by a field of force itself constituted of force-fields? Thus, an electron traversing Earth's atmosphere is intersecting/interacting with Earth's gravitational and magnetic fields (correct?) along with the various EM fields of other particles it encounters and all radiating energy. So don't all these forces together and their overlaps/interactions determine an overall topography of spacetime-curvature at any given moment?

Edited January 3, 2011 by lemur

[swansont]

There are no intersections and overlaps of forces, there is the resultant vector you get when you add all of the forces together. A particle's acceleration is due to the resultant force on it.

 

Curvature is the geometric interpretation of gravity, not other forces.

[alpha2cen]

Does the Space -time curvature only influence gravity, electromagnetic wave path way or time delay?

[swansont]

The curvature is gravity.