Does light produce a gravitational field?

OK, prior to beginning this little rant, I should probably point out that it is late, and my brain does some scary things at this stage in the morning.

Also, my additional disclaimer to my ATS brethren is that gravity is very much still a paradox. From a scientific standpoint, we can observe the effects of gravity, but as far as what produces it, there is no conclusive certainly. I am willing to admit that there are numerous theories around (including a semi-prominent one by a Prof. here at KU) that attempt to account for this, but for the sake of this post, lets assume that I do not have a particular adherence to any of them.

Now that the ground rules are established, lets delve a little deeper shall we?

All matter produces a gravity field, butdoes light as a form of matter also produce a (greatly diminished) gravity field?

I’ve been trying to think this out. Here’s my thought experiment.

Let’s start with something I think we would agree on.

Let’s say we have perfectly empty area of space, complete nothingness. No stray matter, or stray photons running around. Away from major gravity sources. Basically a pure void that couldn’t exist in our universe as we know it.

Into that void let’s place two hydrogen atoms 10 cm apart; perfectly at rest within the void. I think everyone would agree, that over time gravity of the two hydrogen atoms would pull themselves together. Both have gravity fields, both have mass.

Keeping the same setting in the void. Let’s replace one of the atoms with a beam of coherent light. Now we have one hydrogen atom, and a beam of light passing next to it, 10 cm away from the single atom.

I’m thinking of three possible ways of looking at this.

a) The gravity field of the atom bends the coherent beam of light a very insignificant amount and nothing else happens.
b) The gravity field of the atom bends the coherent beam of light a very insignificant amount, but because the atom is free floating; the atom\'s own gravity field pulls itself over to the beam.
c) Both the atom and the beam of light have gravity fields and the atom moves over to the beam of light quicker than choice (b).


That’s the three I came up with; feel free to add your own. This is thought experiment, and not a real world case obviously.

What do you think? Also (and if at all possible) try to keep ideas in the realm of the conceptual (meaning only basic mathematics)

While I am always impressed by ATS folks that posses mathematical skills, I think a conceptual base needs to be established before we can crunch numbers.

Are we talking about any light or just the visible spectrum that humans can see?

Either way my point is that all matter emits light whether we see it or not.
So it would be more amazing to have an empty void of space with light.
the light would technically would not be moving as it never had a starting point or anything to hit...

I love these sort of questions!! just leads to more

This doesn't answer your question, but I think its worth noting that gravity is not what will bring two hydrogen atoms together. If anything, it will be the electromagnetic force (felt by protons and electrons) which drives them together. You see, the electromagnetic force is over 1000 times stronger than the gravitational force. Photons it turns out are the carriers of this electromagnetic force- exchanging photons is what communicates the attraction between atoms. I am not a physicist, so don't take my word for it.

My theory...Both the light and the atom having gravity would make them connect with each other.
Look around you, every light particle is sucking into atoms . This is how we can see.
The light would bend after meeting the single atom.

If there was no atoms. Light particles would "eventually" be sucked into the black matter.



- MORE COFFEE!


[edit on 8-6-2010 by Theone2000]

reply to post by supaflyrobby

Did you think of this a few years ago too?

If not someone else has posed the same question (suspiciously similar wording ) ... have a read, it's very interesting>
www.advancedphysics.org...

Posted: 2004 March 29th, 20:42

...I’ve been trying to think this out. Here’s my thought experiment.

Let’s start with something I think we would agree on.

Let’s say we have perfectly empty area of space, complete nothingness. No stray matter, or stray photons running around. Away from major gravity sources. Basically a pure void that couldn’t exist in our universe as we know it.

Into that void let’s place two hydrogen atoms 10 cm apart; perfectly at rest within the void. I think everyone would agree, that over time gravity of the two hydrogen atoms would pull themselves together. Both have gravity fields, both have mass.

Keeping the same setting in the void. Let’s replace one of the atoms with a beam of coherent light. Now we have one hydrogen atom, and a beam of light passing next to it, 10 cm away from the single atom.

I’m thinking of three possible ways of looking at this....

[edit on 8-6-2010 by and14263]

I thought gravity needed mass? And photons are apparently mass-less, the reason they can travel at the speed they do?

I think the poster who said about the electromagnetic force could be on to something, makes sense.

However, your thought experiment is interesting. I can't really envision something existing yet having no mass, it just seems to make no sense to me.

[edit on 8-6-2010 by Frakkerface]

I have been thinking about this over the past couple of months,
(as well as doing some research into the relationship between an Hydrogen nucleus (Proton) with a tightly-bound ground-state Electron; and a Neutron).

I have this strange feeling that gravitational effects may be due to the un-finite aspects of electrons surrounding large positively-charged "bodies".

Most atoms have what is called a Dipole Moment, that is a small window of time when all (or most) of its electrons are on one side, and it develops a spontaneous and directed electron-magnetic field, and I think this may have crazy probabilistic effects when we reach planetary scales.

Also, if you think of yourself as a sponge of protons, filled with electrons for a moment:
Some of your protons are super-absorbent, and actually suck electrons to them (those whose waveforms conform I guess) and become effectively "Neutrons".
The electrons in this model move to areas of greatest positive charge, of-course; however, the electrons don't actually have a defined boundary.
We use the Fine-Structure Constant, and the Speed of Light to construct Probability-Fields around atoms which are effectively finite, but not quite, and the electrons can be anywhere/everywhere... probabilistically of course and restricted by how fast they can move, E=MC^2, Plank's constant something.
In actuality they have to be somewhere, and they WILL be somewhere, though that 'somewhere' maybe outside of its proton's field of influence.
Larger things will loose more electrons (and gain, but gain less than lose =P) than smaller things, and this I think may cause 'gravity', if this were true we would expect to see strange electromagnetic currents form in large bodies, as well as weird lightning effects on their surfaces (like Earth, Venus or anything else that has electric wind blowing on it).

As for light, I think that is when an electron becomes "Bound" or entangled to two protons at once, and becomes stretched over time. Like probabilistic lightning.

[edit on 8-6-2010 by myster0]

reply to post by supaflyrobby

Does light produce a gravitational field?

Simply put, no; Light is mass-less, so even if you had only one atom and shot a coherent beam of light 10cm away, it wouldn't affect the atom at all. Regarding what another member said, yes light is part of the electromagnetic spectrum, but it is not *the* carrier of the electromagnetic force that would bring two atoms together, the coherent beam of light would have no effect unless shot directly at the atom.

If you would like further explanation, ask your science teacher as I'm sure he would appreciate the show of initiative and that your questioning thing's and making up thought experiments to determine the validity of those idea's.

Originally posted by and14263
reply to post by supaflyrobby

 

Did you think of this a few years ago too?

If not someone else has posed the same question (suspiciously similar wording

) ... have a read, it's very interesting>
www.advancedphysics.org...

Posted: 2004 March 29th, 20:42

...I’ve been trying to think this out. Here’s my thought experiment.

It looks like he did or else he plagiarized someone elses posting without attribution which is a no-no so hopefully it's not the latter. By the way another post in that thread I think has the correct answer:

Post #11 by Xerxes314:

The question is one of principle, not practice. The gravitational effect of light is completely negligible,

Originally posted by sirnex
reply to post by supaflyrobby

 

Does light produce a gravitational field?

Simply put, no;

If the question is: "Does light produce a gravitational field?", then the answer "no" may be a little too simply put, not quite correct but close enough for many calculations.

If you would like further explanation, ask your science teacher

OK I'll take a crack at it:

www.physicsforums.com...

the beam of light does generate a gravitational field. This was first in the article On the Gravitational Field Produced by Light, Richard C. Tolman, Paul Ehrenfest and Boris Podolsky, Phys. Rev, 37, March 1931. The abstract reads

Expressions are obtained, in accordance with Einstein's approximate solution of the equations of general relativity in weak fields, for the effect of steady pencils and passing pulses of light on the line element of their neighborhood. The gravitational fields implied by these line elements are then studied by examining the velocity of test rays of light and the acceleration of test particles in such fields. Test rays moving parallel to the pencil or pulse do so with uniform unit velocity the same as that in the pencil or pulse itself. Test rays moving in other directions experience a gravitational action.

So I look at this question a little bit like the ball dropping analogy. When you drop a ball from shoulder height, does the ball accelerate toward the Earth or does the Earth accelerate toward the ball?

It's a trick question so most people get the wrong answer. The correct answer is both. However the reason we think the ball only accelerates toward the Earth is that the acceleration of the Earth toward the ball is negligible. Likewise, I think the gravitational field exerted by light is typically negligible.

So I go with essentially answer a:

a) The gravity field of the atom bends the coherent beam of light a very insignificant amount and nothing else happens.

Any acceleration of the atom toward the beam of the light would be like the acceleration of the Earth toward the dropped ball, it might exist but it's probably too small an effect to measure.

As regards gravity and light you are not alone in thinking there is a connection :

Hall Photon Theory Paper

Summary:
Hall Photon Theory logically explains the failure of the Michelson-Morley
experiment without invoking Einstein’s theory of relativity.
In addition, Hall Photon Theory hypothesizes equally far reaching changes to Maxwell’s 1864 equations relating to electromagnetic disturbances.
Hall Photon Theory is expected to lead to revolutionary advances in physics, astronomy, and science in general.
Hall Photon Theory strongly recommends that American Atomic scientists
study carefully the behavior of toroidal coils and electromagnetic devices,
especially those constructed using fiber optics instead of copper wire, and
using photons or subatomic particles other than electrons. Possible subatomic particles include mesons, and baryons.
Spacecraft designed in accordance with an understanding of these physical
laws and Hall Photon Theory would be capable of taking off from earth,
quickly accelerating within a few hours to velocities greater than the speed of light without having any negative impact on the well being of the occupants.
Such spacecraft out in the vastness of space would be capable of maintaining speeds greatly in excess of the speed of light for long durations.
They would be able to quickly slow down to ordinary sub-light speeds, and then, land at their destination. During the entire process, time would not slow down nor would it flow backwards.
The energy and fuel requirements would not march off to infinity.
Neither would the mass of the spacecraft march off to infinity.
Such spacecraft would have a double hull construction with several sets of
optical fiber windings between the two hulls.
One set of windings is used to create a uniform surrounding force field that streamlines the spacecraft.
This streamlining allows the craft to move smoothly through space itself. The other sets of windings generate the force fields that are used to propel and guide the craft on its journey.
Spacecraft of this type of construction could readily be built and placed into service using today’s technology.

edit for format

[edit on 8-6-2010 by sherpa]

Light do produce a gravitational field. It is very small though.

Although photons have no rest mass because they're never at rest, they DO exhibit 'relativistic mass' as a function of their high velocity and that causes light to be affected by gravity (attracted to other mass). Light also has an infinitesimal gravitational affect on other mass but it's so weak it may as well be zero. Gravitational lensing in astronomy is proof of gravity attracting light (large mass of a star bending the beams passing close to it) and black holes (if they exist) would have sufficient gravity to actually trap photons that ventured closer than the event horizon.

In the case of a single photon passing within 10cm of a single hydrogen atom in a total vacuum, the photon's mass being vastly smaller than the single proton of the atom means there would be no noticeable affect on the photon's path but there would be some, however unmeasurable. Also, the inertia of the photon's kinetic energy 1/2 mv^2 at the speed of light is a huge factor in this experiment.

reply to post by Arbitrageur

I know, I hate to be a snitch/busy-body but I really think epic thoughts like this should be contributed to the mind which created them. As the OP states in his intro post he is currently 21 he would have had to have thought of this in 2004, when he was around 15. I wish I were contemplating the physical aspects of light at such an early age...

Light is a very mystique stuff. The observer defines it's appearance. As far known, light has no gravity - and also does not react on gravity. Light can be bend, but not from gravity.

en.wikipedia.org...

reply to post by Arbitrageur

If the question is: "Does light produce a gravitational field?", then the answer "no" may be a little too simply put, not quite correct but close enough for many calculations.

Light is mass-less and unable to produce a gravitational field of any strength, even a negligible one. Einsteinian physics correlates gravity to mass, mass to gravity. Without mass, there is no gravity.

The though experiment postulated by the OP was a stationary and solitary atom with zero velocity, then shooting a coherent beam (as in laser) of light past this atom at a distance of 10 cm. A coherent beam of light would have no effect (gravitationally) upon this atom as it does not have any mass in which to induce a gravitational field.

If light is capable of inducing gravity by it's own right, then Einstein was wrong.

Any acceleration of the atom toward the beam of the light would be like the acceleration of the Earth toward the dropped ball, it might exist but it's probably too small an effect to measure.

That's assuming a non zero velocity *towards* the beam of light. This is not the case for the thought experiment. The atom is stationary with zero velocity while the coherent beam of light is 10 cm away and not placed in the atom's direct path. Under the pretense of the thought experiment, there is nothing insightful enough to 'assume' a negligible gravitational field being induced directly by the coherent beam of light, as light has no mass and mass is correlated to gravity. Unless Einstein is wrong and light does indeed have sufficient mass to generate a negligible gravitational field, then the answer to the OP is a strict 'no'.

Originally posted by Archirvion
Light do produce a gravitational field. It is very small though.

No, light can be acted upon by gravity due to it's relativistic mass, but it does not generate any gravitational field of it's own accord. It has no 'real mass' in which to do such a physics defying act.

Originally posted by sirnex
That's assuming a non zero velocity *towards* the beam of light. This is not the case for the thought experiment. The atom is stationary with zero velocity while the coherent beam of light is 10 cm away and not placed in the atom's direct path. Under the pretense of the thought experiment, there is nothing insightful enough to 'assume' a negligible gravitational field being induced directly by the coherent beam of light, as light has no mass and mass is correlated to gravity. Unless Einstein is wrong and light does indeed have sufficient mass to generate a negligible gravitational field, then the answer to the OP is a strict 'no'.

I see that you have a major problem with mathematical expression E=mc2.

Any time there is a volume with non-zero energy density, there will be extra gravitational field. Indeed, in most cases this will be quite negligible, but we are talking about principles here.

And ponder this -- Sun is losing mass by emitting massless photons... Who of course do possess energy.

Originally posted by sirnex
Light is mass-less and unable to produce a gravitational field of any strength, even a negligible one. Einsteinian physics correlates gravity to mass, mass to gravity. Without mass, there is no gravity.

You are confusing rest mass with relativistic mass. The photon has no rest mass, but that doesn't mean its relativistic mass is zero.

If E is the energy of the photon, plug that into E=mc^2 and you get the relativistic mass, m=E/(c^2)

Right?

[edit on 8-6-2010 by Arbitrageur]

Originally posted by sirnex

Originally posted by Archirvion
Light do produce a gravitational field. It is very small though.

No, light can be acted upon by gravity due to it's relativistic mass, but it does not generate any gravitational field of it's own accord. It has no 'real mass' in which to do such a physics defying act.

Then how do you explain the source I cited earlier regarding the gravitational effect of light beams on other light beams?

reply to post by supaflyrobby


As others have noted there's an identically worded question/thought experiment dated six years ago here -

www.advancedphysics.org...

It's an interesting read and I'm glad to have seen it. I don't think I can add anything better than the erudite answers given there, but I'll quote one relevant reply.

You asked -

All matter produces a gravity field, butdoes light as a form of matter also produce a (greatly diminished) gravity field?

reply -

Light is not matter , light is considered a BOSON , a force carrying particle , and not a FERMION , a matter particle.

But light is affected by gravitional effects on macroscopic scales.

Which states the case nicely. Light is electomagnetic radiation - energy, not matter (although I suppose matter is condensed/collapsed energy really). It has no mass. It sometimes behaves as a wave, sometimes as a particle - it has the properties of both (wave–particle duality). Amazing stuff and quite mind bending to think about


I'd just like to try to clear up a couple of misconceptions -

Originally posted by GallopingFish
Either way my point is that all matter emits light whether we see it or not.

Not all matter by any means. Light is emitted by some matter through cold Luminescence (eg chemical reactions, electrons hitting coatings on TV screens etc) or hot Incandescence (sparks, candles, stars). These are termed light sources.

Originally posted by Theone2000
Look around you, every light particle is sucking into atoms . This is how we can see.

No we either see light directly emitted by light sources (see above)

or we see things because they reflect light (from a light source) into our eyes. This is how I can see my mouse for example. It isn't emitting its own light but is reflecting sunlight into my optical sensors

Originally posted by Frakkerface
I can't really envision something existing yet having no mass, it just seems to make no sense to me.

Lots of real things have no mass. Electricity, magnetism, and other forces, some sub-atomic particles ...

Originally posted by myster0
Also, if you think of yourself as a sponge of protons, filled with electrons for a moment:
Some of your protons are super-absorbent, and actually suck electrons to them (those whose waveforms conform I guess) and become effectively "Neutrons".

This is a bit baffling. I'm not made of protons 'filled with electrons'. I'm made of atoms which contain nuclei made of protons and neutrons, with electrons outside that. True enough the protons and electrons have opposite charges which attract each other, but I don't follow the super-absorbent protons bit, or how it would only apply to some of them.