One way to see it is "Since light has an energy density (which is relativistically equivalent to mass) it WILL create a gravitational field (local distortion in the metric), which will cause another nearby laser beam to bend.".

So what is gravity?

It the weakest 'force' we know, about 100 000 000 000 000 000 000 000 000 000 000 000 000 000 weaker than the electromagnetic force, but with an 'infinite reach' meaning that it never stops existing. It 'propagates' with the speed of light, if you want to think of it in terms of 'gravitons'. Its strength diminish "with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them." in accordance with

Newton's law of universal gravitation.So is it a 'force'?

Not according to Einstein. As he saw it gravity was a result of mass distorting the SpaceTime. With the 'gravitational force' then just becoming the way space 'curved/wrinkled' around it, depending on the objects mass/energy/speed/velocity. Entering his world you will find that all gravity-induced accelerations just are the results of them following a so called geodesic (which represent the shortest line possible in a curved SpaceTime, or if you like, the most 'energy saving' path). And so it is equivalent to a free fall, just like that apple falling of the branch. So the orbits of satellites above you are in reality them being in a constant free fall, due to the way gravity curves the space around our Earth.

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[attachment=12909]

A NASA image depicting gravity's variation on Earth.

A low spot can be seen just off the coast of India, while a relative high occurs in the South Pacific Ocean.

Scientists hypothesize that Earth's deep underground structures are creating the distortions, related to Earth's past.

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There are those wanting it to be a singular 'force', expecting that it somehow will resemble the electromagnetic force, but, as for me, I find Einsteins definition the better one.

So, knowing this, can light bend light?

Well, maybe? I don't doubt light have a gravitational 'impact' on the space surrounding itself, and if we assume that the two laser beams are parallel and extremely close to each other, the space will 'dip' around each on making it possible, possibly, for them to converge towards each other, maybe?

But as LeeE pointed out to me, there are no actual experiments that I, or him, know of testing it? Also one have to remember that they do not 'bend', not if you believe Einstein at least. They just take the straightest/shortest path there is inside SpaceTime.

For one, I can't even decide how to think of how that 'space bending' will express itself around a beam? And considering that light is a 'boson', having no size, it is in theory possible to collect all 'photons' there are, and then superimpose them upon each other. Making them into just 'one' photon, without that one taking any place either. But if we tried to do that one, I would definitely expect space to become extremely bent around that 'particle/photon'.

You can of course assume some sort of geometrical center to each part of the beam, as we all know it is 'there' after all, visible for us or at least our instruments. Then you can count on the momentum expected from that amount of energy and define it as the equivalence of a certain amount of invariant mass (matter) being defined at each part of your beam. But as light always will need an interaction to be proved, meaning that you either destroy it by measuring, or measure its interactions through inferring it from other processes taking place around it, it's a very slippery subject to me.

The simplest way is naturally to assume that light 'travel' inside our space, but I expect it possible to consider it not traveling too, just becoming 'interactions'. That makes for a very different way of looking at it naturally. But what may imply it, is the way time-dilation and Lorenz-contraction works, redefining space and time when comparing 'frames of reference' depending on acceleration, motion and mass/energy. And in that case, without 'moving parts', there will be other rules defining space's behavior, although, equivalent to what we call lights momentum. And if that is correct it seems that 'fixed distances' are a somewhat 'artificial' definition, open for redefinitions depending on 'frames of reference'.

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Take a look

Gravity probe B, from 2007. And "The accuracy of the GP-B experimental results has improved seventeen-fold since our preliminary results announcement at the American Physical Society annual meeting in April 2007. At that time, only the larger, geodetic effect was clearly visible in the data. Over the past two and one half years, we have made extraordinary progress in understanding, modeling and removing three Newtonian sources of error—all due to patch potentials on the gyroscope rotor and housing surfaces. The latest results, based upon treatment of 1) damped polhode motion, 2) misalignment torques and 3) roll-polhode resonance torques, now clearly show both frame-dragging and geodetic precession in all four gyroscopes. The combined four-gyro result in the figure gives a statistical uncertainty of 14% (~5 marcsec/yr) for the frame-dragging (EW). The gyroscope-to-gyroscope variation gives a measure of the current systematic uncertainty. The standard deviation of this variation for all four gyroscopes is 10% (~4 marcsec/yr) of the frame-dragging effect, suggesting that the systematic uncertainty is similar in size (or smaller) than the statistical uncertainty. " From their homepage at

http://einstein.stanford.edu/highlights/status1.html.

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