In other words, are there any other massless, but detectable, objects that are not referred to as “light”?
You’re better off asking if only photons (the carrier particle for the electromagnetic force) are massless. The answer is no. It appears that gluons (carrier particle for the strong force) are also massless however you don’t really find single gluons floating about. cite
If the graviton, the hypothesized particle carrier of gravity, exists then it will be massless because gravity propagates at the speed of light.
I’ve read some speculations that a new flavor of neutrino would be massless.
And then there’s this:
Mar 16, 2018 - Herein, we propose — the simplest imaginable — alternative mecha- nism which operates via coupling the massless neutrino to a massive Dirac …
by GG Nyambuya - 2018 - Cited by 1 - Related articles
No. When people thought that neutrinos were massless, no one called them light.
I certainly wouldn’t call them heavy.
Yes, but like the odds of a single Powerball ticket winning there is a distinction between very tiny and zero.
To the limits of our ability to measure, photons, gravitons, and gluons are all massless (though it’s not very relevant for gluons). And it’s only in the past few decades that we’ve been able to determine that neutrinos have mass, and strictly speaking, it’s still possible that one of the three neutrino masses is 0, also. It’s also possible that any or all of the photon, gluon, or graviton does have a mass, just one that’s too small for our experiments to measure.
Even some photons aren’t called “light”. The words are not synonymous.
The word “light” evolved from meaning visible light to also including infrared and ultraviolet, and then stretching a bit more and finding a number of niches usages in other bands. (For example, high-intensity X-ray sources are often called “light sources”).
But no one talks about using light to cook food in the microwave. No one talks about picking up light signals with their car stereo. If a radioactive source is emitting gamma rays, no one would talk about the light being emitted. In these contexts, photons are not referred to as “light”.
The usage of “light” is (like all English words) dependent on context and culture. It never gets applied to other massless particles, and only sometimes gets applied to photons.
Personally, I would say that the entire electromagnetic spectrum is “light” (though only a very small portion of it is “visible light”). But that usage certainly isn’t universal.
No, and the term “object” wouldn’t apply. The designation is energy.
Wouldn’t that result in all neutrinos quickly moving into that state and never leaving it, since time would no longer pass for them?
A bit of background for that question, which you might know but not everyone does: There are three kinds of neutrinos, but what those three kinds are depends on how you’re asking. You can think of them by flavor, as electron neutrinos, mu neutrinos, and tau neutrinos, according to how they interact with the charged leptons. Or you can think of them as nu-1, nu-2, and nu-3, according to their masses. They’re like two different coordinate systems describing the same three-dimensional space. Last I heard, the consensus was that the electron and mu axes were in almost the same plane as nu-1 and nu-2, but rotated by 45º, while the tau is almost lined up with the nu-3.
So anyway, each flavor of neutrino is some linear combination of the three masses. But the three masses would have different wavelengths, so as they propagate through space, which linear combination of masses you have will change. And so the neutrinos will oscillate between the three flavors. But if you somehow had a source of neutrinos of a pure mass state, they’d all have the same wavelength, and so wouldn’t oscillate. And just as you can’t oscillate out of a pure mass state, so you also can’t oscillate into one.
Incidentally, these oscillations are also how we know that neutrinos have mass to begin with, because they tell us the splittings, or difference in masses (strictly speaking, differences in the squares of the masses). With one known mass and the splittings, we could determine the other two. But we don’t have one known mass, and so all three remain unknown.
Personally, my guess is that all three masses are of the order of 1 eV, since most experiments (even very different sorts of measurements) come up with upper bounds in that vicinity. This would make the splittings comparably very small, and mean that there is no massless neutrino. But that’s just a guess.
In all contexts, though? Seems hard to operate that way. The word “light” is very nuanced. Would you miss a beat at all if someone said, “I’m not going in that cave. There’s no light in there”? Would you find it normal if someone said, “The light coming off that tower is how I get music in my car” or “This isotope decays by emitting light”?
Right idea, but somewhat jumbled. No single flavor state is nearly aligned with any single mass state. They are all hearty superpositions of at least two. nu-e is nearly in the nu-1/nu-2 plane, though not near 45º (points toward nu-1 more). The near-45º rotation is that nu-3 is largely in the nu-mu/nu-tau plane and oriented roughly between them. (Of course, one rarely tries to articulate it all this way. You just look at the matrix.)
Combining cosmological data with oscillation data means that no neutrino is heavier than 0.08 eV and that there exists a neutrino at least as heavy as 0.05 eV. So, signs are that you can safely lower your guess by at least an order of magnitude. (And the terrestrial limits that have lived recently in the 1 eV range live there due to experimental limitations, not implied physical importance of that mass scale.)
OK, then, it looks like the “last I heard” information is now badly out of date. It’s been a while since I’ve been active in the field.
And obviously I don’t expect non-scientists, speaking in a non-scientific context, to use words in their scientific meanings. But if someone asked me if radio waves or gamma rays are light, I would say yes, of a sort.
I just wanted to add that we should use caution when we describe any subatomic particle as an “object.” They are really more of a mathematical abstraction than they are an “object.” Non-scientists often want to know what an object “looks like.” Subatomic particles don’t really “look like” anything, at least not in the sense that humans perceive objects in the ordinary day-to-day macroscopic world. Even the term “particle” can be a problem. Most people, upon hearing "subatomic “particle”, imagine something like an itty-bitty, teeny, tiny ball bearing.
Or as I’ve heard it said (by Feynman, maybe? One of the greats, I think), “Particles can’t be made out of stuff, because stuff is made out of particles.”.