Is there a limit to how bright things can get?
In: Physics
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)
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