Is there a limit to how bright things can get?



Is there a limit to how bright things can get?

In: Physics

Yes and no.

Yes, because human eye’s can only perceive brightness to a certain extent.

No, because the brightness of something does not care how much of it can be perceived by the human eye.

The only real limit is the total amount of available energy. The Big Bang was, in practical terms, the brightest thing that ever happened. It released all of the energy that currently exists in the universe as (sort of) light (What, exactly, happened is really technical. You can look up timelines on the Big Bang and see at what point the energy turned into matter and how.)

Supernovas are the brightest things that currently still happen- a massive amount of their energy is released as light. When black holes eventually decay- far, far into the future, long after our sun is dead- they will be the brightest events in the universe.

On Earth, the brightest things you’re going to see are nuclear explosions, which release their energy primarily as gamma radiation (ie, light) which then turns into heat when it is absorbed into the immediate environment, which in turn creates a shockwave as the superheated air expands.

Not really. The “brightness” of an object is how many particles of light it can put out, and there isn’t a physical limit to this. The only limit would be how much energy you can pump into the object, since more energy = more light.

I’m not sure if I’m mistaken. But if we define brightness simply by how much light is in a given volume of space. Then I think the theoretical maximum would be something like a Kugelblitz black hole. A black hole made from light. I don’t think that can naturally occur or any object can ever emit or concentrate that much light just by the sheer amount of light needed.

If we start with the assumption space is mostly empty (which it currently is), and also define “brightness” as the energy contained in the photons exiting the object, than the limit to how bright something can be would the the maximum amount of photons that can exist in the same location in space before they create a black hole. Any “brighter” and the photons would collapse space into a black hole and it would be darker.,with%20the%20no%2Dhair%20theorem.

A black hole can only form if there is a gradient in the curvature of space (a difference between locations) so if all of space were equally filled with photons it wouldn’t matter how many there were because they wouldn’t be able to collapse into a black hole and there would be no maximum brightness.

So how bright something can get quickly leads you to black body radiation. Its the radiation that any so called black body (something that isn’t making its own light like the sun but like your body emitting infrared) emmits if it has a temperature abow 0 kelvin. So the hotter an object is the brighter it radiates. You add more and more heat/energy to a rock or something and it’ll glow brighter and brighter like hot iron. So as you add more energy the radiation gets more energetic so the EM waves have shorter and shorter wavelengths. When the wavelengths reach a Plank length (theoretically the shortest possible distance) nobody knows what will happen. Chances are it forms a black hole since you added so much energy/mass. Such a balck hole has a special name a Kugelblitz, a black hole made out of light.

Yep. My roommate during grad school worked on it. It comes from some wacky bits of quantum mechanics combined with the extremely powerful electric field that makes up an intense light.

So the quantum part is weird, but basically vacuum isn’t actually empty all the time, sometimes a particle and antiparticle will flitter into existence completely randomly, for no specific reason. Most of the time they’re just taking a Heisenberg vacation, and pop back into nothingness before physics catches them breaking the law of conservation of mass and energy.

However, with a sufficiently powerful electric field, you can shove those two charged bits far enough away that they don’t annihilate, and are now free particles living their happy particle lives. Only that pesky energy that they now have needs to come from somewhere, and it comes from the light field, dimming it slighlty.

So this effect actually puts an upper limit on the intensity of a light beam.

I asked him if he had just proved you can’t make a Death Star scale planet-destroying laser. He paused. “You know, I’m not sure.”

So we reviewed the historical footage to determine the length of the pulse that destroyed Alderaan, made the assumption that it was Earth-like and so had a similar gravtitational binding energy. That gives us the total energy the shot had to deliver, and the time it had to deliver it in, which if you divide is power.

The specifications for the Death Star exist in published literature, including the limiting aperture of the main beam. So that gives power divided by area, which is irradiance, which is what goes into his calculations.

Turns out his upper limit was higher than the Death Star laser by quite a few orders of magnitude. He turns to me and says “The rest is engineering. Have fun!”

“…” (me, the optical engineer)