# Can a black hole be made from light if photons have no mass?

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• D g
Lv 7
1 month ago

No the mass of photons is from kinetic energy of the motion the photons never have speed 0 do they are never at rest so they never have Rest mass

Black holes are created by the mass compressing into a small point by its own gravity

Mass from matter stays in on point so this can happen

Imagine that it takes the mass larger than our Sun to create a black hole

• 1 month ago

Yes it can. Photons have energy and energy has gravity. you would have to put a lot of light in one place. I don't know how you could do that, but I guess it's possible.

• YKhan
Lv 7
1 month ago

Yes! This type of black hole is called a Kugelblitz, German term for "Ball Lightening". As we know from Einstein, that mass and energy are equivalent through the equation:

E = m*c^2

Now, all mass is energy, but not all energy is mass Only the type of energy that travels at less than the speed of light is mass. That means mass is a type of energy that is confined to a certain region of space for an extended period of time. An extended period of time means anything that is travelling through space at less than the speed of light, even if it's 99% the speed of light, it's still considered to have mass.

So whenever light gets captured by a black hole, it's energy gets added to the black hole, and because the energy is trapped inside the black hole, it gets detected as mass, since it's confined to a region of space. All black holes are not only made of matter, but also of energy, and at the end of the day, you can't tell how much of it is matter and how much is energy, it all looks the same outside the black hole, it all looks like some form of mass.

• 1 month ago

It's more correct to say that photons have no rest mass.

• Tom S
Lv 7
1 month ago

No, mass at extreme density is needed.

• 1 month ago

No. You'd need mass - a lot of it, in a very small volume - to form a black hole.

• 1 month ago

No, it takes a mass no less than 10 solar masses to collapse to a singularity forming a black hole.

That aside, Crooks radiometer shows photons do have mass as they can exert force to the vane causing it to spin.

The electromagnetic spectrum is strange, Photons a wavefront somewhere in this spectrum,they consist of sub atomic particles traveling at the speed of light in free space. If they had no propagation, there would be no spectrum or photons.

The can be refracted, reflected and absorbed, and passing event horizon of a black hole, there is no return. They too become more black hole, but look how tiny the mass is, far less than an atom.

• neb
Lv 7
1 month agoReport

Virtually every answer you’ve posted is partially or completely incorrect. You know little or nothing about astronomy or physics. Are you trying intentionally to mislead people? Are you utterly unaware how little you know? I’m completely stumped why you do this.

• 1 month ago

Black holes are not "made" from light.  The fact that their gravitation is too strong to allow the escape of electromagnetic radiation (light) other than ultra-low frequencies, does not mean that light is the "material" constituting the black hole.  Black holes are expected to form from the collapse of very massive stars, and a black is expected to continue to absorb gas and dust from its surroundings.  Thus, it is "made" of protons, neutrons, and electrons, just like other things.

• Anonymous
1 month ago

where did you dream up the idea that black holes are made from light?

• neb
Lv 7
1 month ago

In principle - yes, in practice - not naturally.

The source of gravity in general relativity is much more complex than Newton’s theory. The source of gravity in general relativity is something called the stress-energy tensor. It has 10 independent components. The time-time component is the energy density of mass OR the energy density of massless fields. Three of the components are due to momentum density (from special relativity), and 6 components are due to stress/pressure.

Specifically, there is a stress-energy for electromagnetism so the time-time component is the energy density of the electromagnetic field. Electromagnetic waves carry momentum, so the other 9 components are related to that momentum.

A light blackhole actually even has a name ‘kugelblitz’. It would be hard to imagine how to construct one but keep in mind that electromagnetic fields that fall into normal ‘mass’ black holes will contribute to the gravity of the black hole.