Yes, phase/group velocity is an alternate term.
I’d be a lot clearer here. The phase velocity of a tachyonic field is always greater than c. The group velocity of a localizable solution to the field equations of the field is always less than c. Obviously, the phase velocity of the electron field is subluminal. Similarly, the group velocities of non-localizable solutions to tachyonic wave equations are superluminal.
There is no known maximum energy for a photon. Every definition of gamma rays is something like “a photon with an energy of Y or higher”, where Y is some arbitrary cutoff between X-Rays and gamma rays. The key there is the phrase “or higher”. So if you take a gamma ray and blueshift it (which is perfectly possible), then what you have will be even higher energy, but it would still get the label “gamma ray”. This says nothing about physics, but only about human terminology.
Note that I said there’s no known upper limit. It’s possible that there is an upper limit, but that we just don’t know it yet. If this is in fact the case, then the simplest guess for what that upper limit might be is the Planck energy. The Planck energy, like the Planck mass, Planck length, Planck time, Planck temperature, etc., is a quantity which is obtained by cobbling together Newton’s constant (G, which relates to the strength of the graviational field), Planck’s constant (h, the quantum of action or angular momentum), and Einstein’s constant (c, the speed of light and of any other massless particle). For any system involving the Planck scales, both General Relativity and Quantum Mechanics are likely to be relevant, but those theories as we understand them are incompatible. In order to understand what happens at the Planck scales, we would need a theory of quantum gravity, which we don’t yet have (string theory is one candidate for the theory of quantum gravity, and it looks a bit promising, but it’s neither well-established nor well-developed). It may be that once we have a theory of quantum gravity, it’ll tell us that the Planck length or something close to it is the shortest length possible in nature. But it may also not tell us that, and we don’t have any way yet of knowing one way or the other.
So I guess maybe it would be gamma rays? And of unlimited energy? So would the radiation just go through any detector like **** through a physicked goose?
I’m having a hard time dealing with unlimited energy. The object presumeably is emitting energy in all directions and that coming toward the earth is unlimited. So wouldn’t the radiation fry everything on the earth to a crisp?
I’m not sure what you mean. The energy of a gamma-ray photon can be arbitrarily high (as far as we know), but it’s still a finite number.
So you are saying that the energy isn’t unlimited. That’s probably the solution to my dilemma. I guess arbitrarily high is the cause of my difficulty. To me arbitrarily high means that no matter how big a number I choose, the energy is higher than that. In terms of mathematical limits.
energy - limit = e
if energy has a limit then the difference between energy and limit , e, will become and remain less than some arbritrary number no matter how small that arbitrary number is. To me the term arbitrarily high means that there is no limit that will produce an e that will satisfy that condition.
Maybe I’m misinterpreting things, which wouldn’t be all that uncommon.
What’s meant is close. It means that no matter how big a number you choose, the energy of a gamma ray may be higher than that. Alternately, there exists a gamma ray with higher energy than that. Apply your mathematical concept of “arbitrarily large” to the set of gamma ray energies rather than to the energy of one particular gamma ray.
Speaking of limits, I’ve about reached mine. Does this mean that scr4’s analysis that although arbitrarily large it is still finite is correct, or that we would all be boiled alive in gamma rays?
Each photon has a finite energy. When I said the energy can be arbitrarily high, I meant that no matter which photon you pick, it’s possible to create another photon that has more energy. It doesn’t necessarily mean such a photon exists anywhere in the universe.
Similarly you can say the wealth of an individual can be arbitrarily high. That means there’s no reason someone can’t acquire more money than Bill Gates. But it doesn’t necessarily mean there is such a person, and it certainly doesn’t mean one individual can have unlimited wealth.
okay, trying again.
Consider the set of natural numbers. They can be arbitrarily large, in that for any natural number you pick there exists one larger than that. Each element is still finite, though
One can have a gamma ray of whatever energy one chooses. That does not necessarily imply that one does have a gamma ray of that energy. Asking “How much energy does a gamma ray have” is comparable to asking “how big is a rock”. A rock can be very big. A rock can be the size of the Earth. That does not mean that when I’m hiking up a mountain and a few rocks fall onto the path that the path is getting smothered in planets.