If you know pretty much nothing and thought of this as easily as you did, I'd say it's certain that scientists who have dedicated their whole lives to answering that question have also had the same idea by now or understand why the idea is flawed.
We think we have accounted for all the ordinary energy in stars, galaxies, intergalactic dust, etc., but things at the very largest scales we can observe, galaxies seem to be drifting apart from each other. Our model of physics tells us that the energy (which is also mass; e=mc^2 mass and energy are equivalent 'things,' just in different forms) we're familiar with is gravitationally attractive, so we surmise there must be some sort of exotic repulsive energy counteracting the attractive stuff we've accounted for. And if we use our model to estimate how much of this so-called 'dark energy' there is pushing the galaxies away from each other (based on things like galactic mass, apparent rates of recession, and so on), we get that there is something like 15 times more of this 'stuff' pushing things apart than there are actual things. We dont know what this exotic energy might be, we cannot confirm our hypothesis because no way of detecting this stuff in a lab has ever been devised. It's entirely possible our model is simply flawed, or that our observations are incorrect or incomplete.
The problem is Dark Energy is the majority of energy in the universe, by ~3x (very roughly, I of course forget the exact proportions).
That immediately excludes ALL energy given off by stars/etc, as not only is it way more than would ever be possible, but traditional energies would DECREASE the expansion rate, not accelerate it.
There is also the massive problem of how it appears: between galaxies. NOT within galaxies, but on a larger scale. If it were caused by stars, it would be concentrated around denser galaxies, not literally the opposite of that.
I didn't realize how significant the issue is, at most I was thinking maybe just barely double but not significantly beyond it.
On it being in the "empty" space or void between galaxies, could it be some of quirk of gravity? What I mean is that the absence of sufficient mass would lead to these voids "expanding". Using the typical example of a stretched elastic sheet, the demonstration is to show how mass pulls space in upon itself. Except this would be the inverse with the mass collecting on the border of the void, causing it to be stretched apart instead.
Any chance you could recommend reading material on this?
Yes, someone has.
I think you're mixing up dark matter and dark energy. Dark energy isn't a real thing, it's the placeholder to make certain math come out to work in reality. Dark matter, on the other hand, is, as far as we can tell, a very real thing, but very hard to measure since it only mostly only interacts with other matter via gravity. That gravity is what's affecting the formation, motion, and expansion of the universe.
While stars are blasting out matter, black holes are blasting out jets, and everything is emitting energy, yes it does affect some bodies, but that effect pales in comparison to the sheer mass of the bodies themselves. Look at spacecraft with solar sails. They need to be small and light, with huge sails, and even then they take a long time to get up to speed. Now compare that imparted energy to even a nearby planet: even Mercury isn't significantly affected in its orbit.
The universe is expanding. The rate at which it's expanding is increasing. It should be increasing a lot more; something is holding it back, some kind of energy. We have no clue what that energy is or where it comes from because we can't detect it. We only it know it has to exist because nothing else makes the equation balance. Since we don't know anything about it other than it (theoretically) exists, we call it "dark" energy.
Relativity tells us that matter and energy are equivalent. Therefore, all energy has a corresponding particle. Particles have mass. All things with mass are "matter". We have no information about the matter corresponding to dark energy, we only know it (theoretically) exists. Since we don't know anything about it, we call it "dark" matter.
Nope. Wrong.
BOTH are not "real" things, as far as you describe. They BOTH describe phenomenon we have no precise explanations for.
Dark matter: Many (NOT all) galaxies rotate or otherwise act like they have a LOT more mass around them than we can observe. Mostly visible by further out objects rotating faster than they should. If there were only as much mass as we can see, outer objects should mostly be waaaay slower.
Dark energy: The furthest distances in the universe are accelerating away from us. That acceleration requires energy from somewhere. It does NOT happen within galaxies, but of course we can see millions of galaxies with the ultra-sensitive telescopes we have today.
In BOTH cases, we do not have a detailed explanation for, but we DO have MANY observations that confirm the effects. They are BOTH real phenomenon, and neither have solid explanations, yet. Hence the "dark xxx" names.
Dark matter is not just a mathematical construct to explain velocity curves, even though historically that was the first step. Since then, we found compelling evidence of dark matter acting as gravitational lenses. It is a very real phenomenon, as we absolutely know that there is an excess of matter that is dark, i. e. not radiating or absorbing light. Some open questions still exist about dark matter, such as whether it is made up of particles and how they are generated. But the question of whether it is real is settled.
Dark energy is more of a placeholder name at the moment to explain the accelerating expansion of the universe. It is more contested in the scientific community and there is no direct evidence of this energy yet, some cosmologists deny the existence of dark energy at all and claim that is a mathematical flaw in general relativity (the equivalent explanation of dark matter as a flaw in current models called modified Newtonian dynamics or short MOND, is a very fringe theory by now). As such, the question of whether dark energy is real is not settled, it is currently a prediction to explain some observations but lacks further evidence.
The name "dark", in reference to dark matter or dark energy, has nothing to do with light or photons; it refers to the fact that they can't be detected. We haven't been able to build any kind of device that can measure either or even determine whether they are or are not present within a certain area of space.
As far as we know, they either exist somewhere within our universe, or the equations we've "proven" to represent the fundamental reality of the universe as we know it are wrong in some way.
If you ask me, either prospect is equally exciting and interesting.
Yeah it is sort of like a physics in-joke, it doesn't really mean that anyone believes there is actual matter or energy that we would recognize sneaking around right under our noses, there's no obvious explanation for it, it makes the math work the way we expect but it doesn't seem to really be there. But it's sort of fun to ironically pretend it is a familiar and practical physical phenomenon, and for lack of a better explanation why not run with it, but that doesn't mean it IS the explanation. It's sort of like how you might pretend your car has feelings. You know everything about it that tells you it actually doesn't, there's no actual sign of it at all. You might be able to make it fit the facts from time to time, but it doesn't mean you're going to make sure to go ask how your car is doing after every major life event. It's fun, it's harmless, but it's not real.
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