Another nail in the coffin of Dark Matter and in favour of MOND and similar explanations here.
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Dark Energy is a different topic, and is a placeholder name for whatever causes galaxies to all be moving away from each other, unless they are fairly close and gravitational attraction over-rides it (by several orders of magnitude).
The clever scientists don't really know why this is happening, and there are different ways of calculating the rate of expansion which give different results (although they all seem to be within +/- 10% of each other).
I have spent a couple of weeks reading and trying to understand the page on Ozone Depletion Theory titled What is Electromagnetic Radiation?. I still only vaguely understand most of it, but this sentence grabbed my attention:
Light illuminates matter, but light itself is not visible, it is dark, until it interacts with matter. Given that Earth receives less than 5 x 10-8 % of Sun’s radiation, there must be a lot of dark energy in space that changes in time...
Woo hoo! That might be it. As a matter of fact, there is such a thing as solar sails, as popularised by Arthur C Clark, which use 'photon pressure' to gently but firmly accelerate a spacecraft. The rate of acceleration is painfully slow, but it is constant and cumulative, so they can get up to fair old speeds after a few years or a few decades.
So the logic is this: only a teeny-tiny amount of light emitted by a star hits solid matter in its own solar system or even its host galaxy; most of the light goes out into intergalactic space. A teeny-tiny amount of starlight leaving each galaxy hits solid matter in its own galaxy cluster, and so on and so forth. And in turn, each galaxy is being hit by light from all other galaxies; so they all act as giant solar sails.
As star light is nearly as old as the universe, those billions and billions of years worth of starlight from each galaxy (or galaxy cluster) is pushing each other galaxy (or galaxy cluster) gently but firmly away from itself and the cumulative effect is (just about) measurable (if you call ≈70 km/second per megaparsec distance measurable). By definition the rate of expansion must also be gently but firmly increasing.
Whether or not the universe has a "centre" (and I am prepared to accept that it doesn't, and it is not expanding into anything larger), this leads to its gradual expansion!
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This might be complete nonsense, but it's an entertaining thought at least. And seeing as its the only explanation I've ever seen, I'm going to stick with it for now until a better one comes along.
I'm So Glad I Never Clapped For Them...
1 hour ago
15 comments:
I like this theory- it fits with my desire for nice simple explanations, so is probably wrong
TBH, ta and agreed.
But....but..... if the universe is increasing its rate of expansion at extreme distance, and the space between stars, galaxies, objects whatever is expanding at a speed approaching lightspeed at those distances, and the expansion is happening in all directions equally relative to any single point - therefore the distances between stars are increasing - then pressure of photons to act on objects and propel them must be getting smaller (inverse square law?). On the face of it that's not consistent with a universe whose expansion is increasing.
Well doesn't seem like it to me, anyway, though I claim no expertise at all. I just got fascinated some time ago about how it can be that the 13.7 billion-year-old universe can have a (mostly unseen) total diameter of something over 92 billion light years (46 bn lightyear radius, not the 14 bn lightyear radius that it was said to be) so did some reading. The idea of an event horizon at a distance of just under 14 bn light years, with another 30 or 32 bn light years behind it in every direction was a bit mindblowing to an old fart who spends rather a lot of time wishing he'd worked harder at his education.
I'm not arguing for dark matter, either; from what I understand of the MOND alternative, I rather like that as an explanation simply because it "feels" more elegant and "more right". But as I said - what do I know? :)
«Light illuminates matter, but light itself is not visible, it is dark, until it interacts with matter.»
There is a little gem here, and in the idea that floods of background radiation can interact with galaxies to the point of pushing them around, that I only fully understood when reading a particularly good particle physics book:
* We cannot "see" or measure anything except by probing the anything with an interaction.
* In order for the probing to be "accurate" the probing object must be in some sense much smaller than the probed object, so most of the effects of the interaction happen to the probing object rather than the probed object.
* For probes light is pretty good because photons are pretty small.
* Unfortunately for particle physics photons are pretty big, so interactions are ambiguous.
* So we have ended up trying to "measure" particles by probing them with particles of much the same "size" (mass or momentum), so too bad about that.
FT, clearly, once galaxies are beyond our event horizon, they have no effect us any more.
But...
a) they must have been within our event horizon earlier on, so gave us a push (and we gave them a push), and that motion continues for ever.
b) there are still plenty of galaxies within each event horizon to continually gently push on each other
c) the ones on the edge of our event horizon are within the event horizon of galaxies OUTSIDE our event horizon and they are all pushing each other.
B2, so you reckon it's vaguely plausible?
But...
a) they must have been within our event horizon earlier on, so gave us a push (and we gave them a push), and that motion continues for ever.
Agreed, of course.
b) there are still plenty of galaxies within each event horizon to continually gently push on each other
c) the ones on the edge of our event horizon are within the event horizon of galaxies OUTSIDE our event horizon and they are all pushing each other.
Also agreed. However the size of the universe is increasing at velocity approaching lightspeed but so the total amount of matter is spread through a larger and larger volume of space. So "pushing" must get weaker, surely. And yet rate of expansion is said to be accelerating. So some other factor must be involved?
FT, no.
Imagine a crowd of people, each pushing the people next to them a bit further away. Assuming minimal inertial mass, no friction between people's feet and the ground, the people at the edge will be moving away from the "centre" (i.e. any given starting point) much faster than the people near the "centre" are moving away from the "centre". Which is what we observe.
This "push" is cumulative, it's gentle but steady acceleration "away" from everybody else.
I assume that there is a terminal velocity. Once a galaxy has disappeared from our event horizon, we can ignore it. But we are still being pushed away from galaxies within the event horizons, so we are still being accelerated away and the rate of expansion is increasing...
Until such a time as all galaxies have disappeared from our event horizon (or merged with our galaxy), after which rate of expansion is constant. But we are still nowhere near that stage, as there are plenty of galaxies within the observable universe/event horizon.
(OK, I made this up this theory in half an hour on the basis of a throwaway comment in an unrelated article, but hey...).
there is a terminal velocity.
Yes, for matter or radiation it's presumably the speed of light, ultimately. There's no such limit on the speed at which spacetime can expand and I can't help feeling that your theory only works if the universe were envisaged as a vast "empty" space with galaxies and star clusters and gas all speeding through it under your mutual repulsion.
But the moment a universe which expands because spacetime is expanding comes into play, with all the galaxies and what-have-you also speeding through it but hitching a ride on the expanding spacetime, the idea of solar sail effects driving the "expansion" stops working. In reality of course, I have no idea; like you, I'm just making it up as I go along.
FT, you are asking too many questions.
The clever scientists tell us that galaxies are moving away from each other, and that the speed is increasing etc etc.
I'm just suggesting a reason why this is happening and not delving into the ramifications.
The clever scientists also tell us that the further away a galaxy is from us, the faster it is moving away from us. Fine - it's quoted as 70 km/sec per megaparsec. The logic of this is that really far away galaxies are moving away from us faster than the speed of light, again I take that as a given and not questioning whether it is possible or not (I see no reason why it shouldn't be).
Show me what an atom looks like please?
Not the images science has created, question begging style.
As soon as science confesses, it too is a religion fundamentally, then we may start to make progress.
RS, it's a conspiracy man!
What is spacetime expanding into?
Dark matter and dark energy cannot be detected directly. They are constructs as we know to explain observations that do not stack up against our current physics. Ergo that physics is missing something.
You can actually have an infinity of infinities. I read that the mathematician who proved this went insane.
I hope you have a Merry Christmas. God knows what the New Year will bring.
Dr E "What is spacetime expanding into?"
Apparently, it's just expanding without expanding into anything.
"Dark matter and dark energy cannot be detected directly"
Dark matter doesn't exist. They made it up. And wasted $ billions on huge detectors to try and find it.
Dark energy does exist. As I explained, a likely candidate is star light IMHO. Or maybe it's something completely different.
"Ergo that physics is missing something"
Yes - something like MOND and the cumulative effective of billions of years of starlight. Sorted.
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