What is the current understanding and what the hell are children calling it these days?
Back in the 1800’s, “Luminous Aether” was proposed, then discarded.
I’ve heard terms like “quantum foam” in the past and read descriptions of a basic energy state where virtual particles pop in and out of existence. Zero point energy is supposed to make use of this state. Another article I read recently was talking about it being packed with both matter and anti-matter pairs, which sounded a bit odd.
On the phone right now and don’t feel like thumbing a long post, but you would do good to look at the Wiki articles on pair production and on virtual particles. Also, this article.
Here’s an article about virtual particles I particularly like:
So, what’s this field? It’s the quantum field relevant to the particular kind of particle we’re talking about: Electrons have an electron field, photons have a photon field, and so on. Those fields are the fields wavefunctions exist in the context of; modern quantum physics is done entirely in the context of those wavefunctions, and mathematics to turn their properties into probabilities they’ll enter a certain state.
This is a picture-heavy introduction to what a quantum field is; it comes down to imagining the field as a lot of balls on springs, each of which can vibrate, but each of which is hooked to its neighbors so when one vibrates, the vibrations spread. This is useful in the context of the article on virtual particles I just linked to, in that some waves are coherent and some are not, but all waves are field excitations which can carry energy, both through the same field and into other fields, as certain fields are coupled to each other. For example, the electron field and the photon field are coupled, so electrons can interact with photons and vice-versa: The energy in the photon field can get transferred into the electron field, and the energy in the electron field can get transferred into the photon field.
The difference between these fields and the aether is easy to observe, BTW: Aether theory makes a few predictions about the speed of light, which come down to it behaving like sound and going faster in some directions than others depending on how someone is moving relative to the aether itself. That experiment’s negative result is one of the most celebrated negative results in all physics and, in short, if your theory doesn’t make the same disproven prediction, it isn’t an aether theory.
Thanks Derleth.
I also realize that nowhere is really empty of particles. There’s so many photons, neutrinos and other things flying around that if you were able to freeze even a cubic centimeter of space in time, there’s a really good chance there would be a few of them in that cube. Which seems to me would have at least a (very?) small effect on the quantum fluctuations as they zoom through.
It’s better to think more in terms of fields: If you took a chunk of the Universe, the fields in that chunk are always, constantly vibrating with energy. It’s impossible for them to be at rest in the way most people use that term, because their lowest-energy rest state is one where they’re still vibrating.
Therefore, there are always “particles” in the modern definition of the term (field vibrations) but those vibrations might not be strong enough to matter very much depending on what the observer is doing.
And, yes, particle number depends on the observer: If an observer in an inertial reference frame observes a vacuum, an accelerating observer sees a gas of particles at a temperature proportional to their acceleration. This is called the Unruh effect.