How Cn Gravity Affect Light When Light Has No Mass?

[Rhondazvous]

This is the $50 million question

If gravity only affects objects that have mass and photons are massless, why does light curve around a planet or get trapped in a black hole?

Energy and mass are interchangeable directly, and for the purpose of gravity.   Photons have energy, E=MC^2, hence photons have equivalent of mass.  

Think of it this way, by E=MC^2, all forms of energy have equivalent of mass, and therefore are both affected by gravity, and exert their own gravity.    If global warming heat the earth up, the gravity of the earth actually increase because the added kenetic energy of the molecules makes the earth slightly more massive.  

If you annihilate a mass particle with its anti-partlcle, the mass of those two particles will convert into photons.  If you somehow trap the photons so they don’t speed away, you will find the gravity well around the these photons remains exactly the same as before the annihilation.

This explains a lot, with one nagging caveat. Photons mediate the electromagnetic field. While the mediator of the gravitational field has not yet been discovered. So we have mediators in two separate fields affecting one another. If photons create gravity, then the electromagnetic field is also the mediator for the gravitational field. Is it possible there is no gravitational field? Like heat, maybe gravity is just a property of matter or a property of spacetime when massive or energy particles come close.

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General relativity: Mass warps spacetime. Photons travel in spacetime so to an outside observer they follow a warped path when passing an object with mass.

Special relativity: E=MC2. Photons have relative mass even if they don't have resting mass.

And this explains why although photons existed before recombination, there was no matter and therefore no gravity to counter the dark energy pushing everything apart. only after things got so apart that they lost energy was the strong force able to bring quanta together to form atoms and then large bodies with measurable gravity.