So i’m somewhat skeptical about dark matter and dark energy. Not in the way a creationist doesn’t believe in evolution (which is proven, DM and DE are vague quasi-hypotheses, nothing more at this point), I’m certainly a believer in science.
Anyway, so the universe is expanding faster than we expect. A mysterious dark energy force? Ehh. Could it merely be that the universe as a whole is rotating and the expansion is due to centripetal force? Rotation seems to be a norm in our universe, from the atomic scale up to galaxies. Why couldn’t the universe itself be rotating?
And if it were rotating, even very quickly, would we be able to tell? Seems to me there wouldn’t be any frame of reference from which to discern that rotation. It wouldn’t be orbiting around some huge center of gravitation. Unless that rotation is causing everything in the universe to move apart, to expand. Perhaps someone could calculate how quickly the universe would need to spin in order to be congruent with the degree of unexplained accelerated expansion we seem to identify (at least on one plane)
Now, obviously if the universe were rotating around one plane like a planet, there wouldn’t be even acceleration in every direction (is there?). Things on the universal equator would move faster than things near the ‘poles’. But with all the talk of 11 dimensions and whatnot, if I read an article that says the universe is rotating equally fast in all possible directions, it wouldn’t sound any stranger than ‘dark energy’ or light having a speed limit or quantum entanglement or virtual particles or black holes.
So, is it possible the unexplained expansion of the universe is due to some form of universal rotation?
Assume for a moment that it is rotating: what’s causing it, why is it accelerating rather than slowing, and why is it expanding and accelerating simultaneously?
Objects nearer the center of a rotating body tend to revolve faster around its center than objects further away. Think of a Mercury year VS a Neptune year.
IANAA but I assume we’ve been watching the movement of stars long enough to conclude that there is no universal unidirectional rotation involved.
I don’t think it does anything to explain the accelerating expansion that “dark energy” is supposed to explain, however (and which was not known to exist in Göedel’s time).
The notion of “centrifugal force”, inasmuch as it is a real thing at all, applies to systems rotating within some spatial framework. The universe as a whole, however, is not within such a spatial framework, it is the overarching spatial framework. That being so, I don’t think the notion of a centrifugal force being produced by a rotating universe makes any sense, even if (as Gödel apparently showed) it is possible to make sense of the notion of a rotating universe.
The Milky Way galaxy, of which all the individual stars we can see are are a part, is rotating, as are all (or most) other galaxies. This has nothing to do, however, with whether the universe as a whole is rotating, or with the universe’s overall expansion (although I think galactic rotations are thought to be affected by dark matter, and maybe by dark energy too).
The Bad Astronomer (bless his little oblate spheroids!) talks about rotating universes now and then, sometimes in the context of alternative notions of a non-rotating earth. (The earth doesn’t rotate; the cosmos whirls around it.)
He has pointed out that this is a perfectly valid model of the cosmos: relativistic effects such as frame-dragging cause all the equations to balance, just as they would in a non-rotating universe. Any point in the cosmos could be the “center,” and almost any rate of rotation, can be supported. The equations don’t care.
(It doesn’t even matter that the most distant stars would be moving very much faster than light, since it is the cosmos itself that it moving, not the stars.)
Given that the equations all balance out the same for any rotation, it would seem that it would not successfully model cosmic expansion. But…perhaps I’m confusing two different kinds of rotation? One is the rotation of the known cosmos about a point within it, and the other is the rotation of the cosmos within some bigger, extra-cosmic frame of reference?
> Anyway, so the universe is expanding faster than we expect.
That’s not what dark energy is supposed to explain. The reason that it was proposed was that it was found that the expansion of the universe is speeding up, not that it was expanding faster than expected. You can’t explain that just by rotation.
“speeding up” was my possibly inartful way of saying expanding faster than expected. I figure a spinning universe would cause everything to accelerate outward. Isn’t that the force (and the direction) DE is meant to explain?
As for what’s causing such a rotation, who knows. Why would I have to explain that? The nothingness before the Big Bang was rotating in non-space, and when the big bang occurred the universe as a whole took that rotation. There I explained it.
NJTT: but everything within the universe that we see accelerating IS within that spacial framework.
Dark matter is not a vague quasi hypothesis. It is not surprising at all that we can’t see all the matter in the universe. We’re just lucky that some of the matter is clumped together and really hot (we call the clumps stars). We can measure the effect of the dark matter because of the gravitational attraction that affects the hot clumps. So we know that most matter is not in hot glowing clumps. We don’t know much at all about what form that matter takes, which is why we simply call it dark matter.
Dark energy is an entirely different matter (no pun intended). It is just a code name for the fact that the expansion is accelerating. We could just as well call it the cosmological constant, which is what Einstein called it when he modified his original theory of gravitation. We know virtually nothing about what is causing the acceleration, but it is pretty well established that it is happening. If the name bothers you, call it quintessence, another code name for our ignorance. Again it is not a quasi hypothesis, it is a pretty well established fact that the acceleration is occurring.
I won’t address your rotating universe quasi hypothesis (nice term, that), because I don’t understand how it could possibly explain the observations.
No, things would spin outward but wouldn’t accelerate unless some other force was acting on them. Rotational force decelerates once energy causing the rotation is no longer being put into the system. The earth will have a 25 hour say in a few million years unless something sets us to spinning faster.
What I was hinting at was what Wendall Wagner said outright: the key isn’t that the universe is expanding faster than we expected, it’s that it’s accelerating and we don’t know exactly why. It’s as mind boggling as if you tossed a ball straight up and instead of it slowing down and falling to the ground, it inexplicably speeded up and kept going straight up into the sky faster and faster. Things don’t normally speed up like that unless something is acting on them. That’s why I asked what it was that caused the rotation; if it was the Big Bang, rotation isn’t much different than things expanding outwards as far as what you’d expect for deceleration. If it’s some other force causing the rotation to speed up instead of slow down, that’s pretty much what they’re currently calling dark energy. It’s more or less a placeholder name for whatever force is causing the acceleration.
The bigger problem with trying to explain the acceleration this way is that it’s isotropic: That is, no matter what direction we look, we always see the same acceleration. If it were due to rotation, it would be at a maximum in the direction of some equator, zero towards the poles, and somewhere in between in all other directions.
That said, though, it’s perfectly sane and reasonable to be uncomfortable with the notion of dark energy. We know almost nothing about it, and understand less. It’s really mostly just a label for our ignorance.
Chronos: yes I mentioned this about the equator and poles in the 4th paragraph of my initial post.
Anyway, I know two things for sure. Dark Energy and Dark Matter are both extremely mysterious. And the word “accelerate” should have two L’s in it dammit. I’ve been misspelling that word forever, and it just doesn’t look right with one L. Why it doesn’t have the two L’s it so obviously should is an equally great mystery.
kaltkalt, you need to quit this acceleration of your writing. Slow down and think very carefully before you post anything. Your posts aren’t very coherent. You wrote:
> “speeding up” was my possibly inartful way of saying expanding faster than
> expected.
In that sentence, you’ve turned around what you said and what other people said here. You didn’t use the term “speeding up” in your original post. I used it originally. You didn’t quite say “expanding faster than expected” either, but you said “expanding faster than we expect.” So what you did in the above quoted sentence was to attribute what you said to other people and what I said to you.
Henceforth, think very carefully before you post. Make sure you understand what other people are saying. Make sure other people can understand what you are saying. Posting on the SDMB is not a race. You should re-read your posts several times before posting them to make sure you’re saying what you want to say.
Yea i typed it backwards, put the wrong thing in quotes. You obviously knew what I meant.
And I don’t see any difference between “expanding faster than we expect” and “expanding faster than expected.” Are you claiming there’s a difference between those two phrases?
There is a flaw in your OP. You claim to be 'certainly a believer in science ’ though your post indicates otherwise. You seem to be looking for answers from your observations and try to be fitting the science to it - much like creationists do.
So from a scientific POV I believe your answer is currently NO, can you force the scientific observations to your view, possibly, but that does not make it science.
Also, the way people tend to talk about dark energy - it exists even though we can’t see it and can’t explain it and we don’t know for sure it even exists - sounds extremely faith-based to me. Why not just call it “god” instead of dark energy? So you bet i’m going to try to think of some explanations for the accelerated expansion of the universe that doesn’t involve something so transcendent and illusory. I’m nearly certain I’m wrong re: the rotation theory, but that’s no reason I shouldn’t ask the question to get a bit of feedback.
The way I explain it to non-scientists is that we know what Dark Energy does, but we do not yet know what is - what it’s made of. The expansion of the universe is accelerating. This was discovered in the early 1990s - about 20 years ago. It’s not new to Astronomers. When they couldn’t find a cause for this observation, Astronomers started referring to is as “Dark” (i.e., unseen) energy. They could have called it “Cryptic Acceleration”. Calling it a “Negative Cosmological Constant” would have been reasonable, but requires explaining both the phenomenon and the name to the general public.
The term “Dark Energy” may have been developed as an analogy to the term “Dark Matter”. Dark Matter is another thing where we know what it does, but not what it’s made of. Astronomers have known since the late 1950s that the orbits of stars in galaxies were faster than could be explained by the total mass of the other stars within the orbits. But if the matter (the stuff that causes gravity) isn’t giving off light (like stars) and isn’t blocking or filtering light (like cloud of gas or dust) then we can’t see it. Since we can’t see it, the Matter holding the stars in their galactic orbits is Dark, hence the name. It is a difficult problem to determine the composition of something we can’t see, when the only observable fact is that it causes gravitational attraction. Since the 50s the Astronomical community has learned a lot about Dark Matter (it’s an inter-galactic phenomenon), but we still don’t know what it’s composed of. Neutrinos? Exotic matter? Sub-atomic particles that only interact with the Weak Nuclear Force and with gravity? The guesses are wide open. Nature has not been so forthcoming with answers.
I think you’re thinking of the phrase “dark energy” wrong. It’s not faith based at all, because the phrase “dark energy” originated as simply a placeholder name for whatever is causing a phenomenon we can observe, the acceleration of the expanding universe. Like Typo Knig said, we know what it does, but we don’t know what it is - we’re observing a phenomenon but we can’t explain it. “Dark energy” is what we call it in lieu of an explanation, not the explanation itself.
> Also, the way people tend to talk about dark energy - it exists even though we
> can’t see it and can’t explain it and we don’t know for sure it even exists - sounds
> extremely faith-based to me.
We can go back one hundred years and say the same thing - we didn’t know what mechanism explains quantum physics. There were formulas that showed what it predicted in any particular case, but no one knew what phenomenon was behind it. There are still many interpretations of it:
We can go back a further two hundred years and say the same thing. Newton didn’t know what gravity was. He had a formula that predicted what would happen in any particular case, but he didn’t know what it was.
This is how science works. It doesn’t give large philosophical explanations of anything. It gives formulas and scenarios that show what’s happening physically and the mathematical relationships between the things we observe, but it doesn’t explain them in any deeper sense. “Dark energy” is no more or less an arbitrary name for a formula to explain what is observed than “gravity” is. Gravity is now a more basic part of physics than dark energy is, but it’s still mostly just a formula to characterize the world.