I think the Universe started expanding right on the Big Bang. Isn't that correct?
So why do you need a 'Dark force'?
Well, the red-shift observed in galaxies beyond the local group, strongly suggests that the universe is expanding. The Big Bang hypothesis also accounts for why the universe isn't collapsing because of gravity. Until fairly recently, it was assumed that gravity would slow down the expansion, and possibly reverse it, so that all the matter would be pulled back into a Big Crunch. When the red-shift of distant galaxies was analysed, the results strongly suggested that, far from slowing down, the expansion of the universe is actually speeding up. Assuming Newton's first law of motion applies to galaxies, on the cosmic scale, some force is counteracting gravity. We don't know what it is, so we give it a fairy-tale name, but the red-shift, whatever the cause, is real.
That's interesting indeed. I don't read about it since some time.
You've highlighted one of the difficulties with the language used to describe the universe. If the universe is just the star and two planets, then in order that the universe gets bigger, the planets have to move to more distant orbits, because that would be what it meant for the universe to get bigger.
This kind of gets to the heart of the problem. I think what you are assuming is that there is some stuff that would be the universe, even if there were nothing in it. In a way, that is what 'Dark Energy' appears to be, it is something that applies an apparently mechanical force on stars and planets; but on less than gargantuan scales, it's effect is swamped by gravity and we simply don't notice it on the scale of the solar system.
If the simplified universe you are suggesting behaves the same way that 'our' universe appears to, then the gravity that binds the planets in orbit around the star would continue to do so, up to a point. The speed of orbit decreases the further out you go; so for example the Earth is going round the Sun at roughly 30km per second, whereas Jupiter is only going at 13km per second. Eventually dark energy would be pushing the planets away from the star, faster than they were going round it, so they would never complete an orbit, and effectively move away from the star in a straight line. I'm not sure that answers your question though.
Until the acceleration of the universe was discovered, it was common for physicists to dismiss Einstein's idea of 'spacetime' as a substance with mechanical properties and treat 'space' simply as the gap between objects. Most now accept that space really is some sort of stuff that can push galaxies apart.
Better than some of the native English speakers.
Thanks for your comments and patience UWOT.
The thing is, we simply don't know whether the universe we see is all there is. Lawrence Krauss wrote a book recently, A Universe from nothing, which basically argues that our universe began as a fluctuation in a pre-existing quantum field, which resulted in a chain reaction. Maybe so. It might also be the case that the same quantum field was created in the Big Bang, but as the evidence is beyond the visible universe, we may never know. Either way, the quantum field (or fields) do appear to have mechanical properties.PauloL wrote: ↑Thu Aug 31, 2017 4:45 pmLet's suppose quite simplistically again that the universe is twice the orbit of the farthest planet. So if next time it's four times that size, universe expanded. If the planets depart to farther positions, but the universe size remain the same I wouldn't say universe expanded.
Personally, I think 'dimensions' are relational; I don't think there is any solid evidence that they exist as anything other than a means of locating events. If you just mean the universe is getting bigger, I would agree that is by far the best explanation of the data, but again, this is a subtlety of language that even native English speakers are confused by.
The theory is that space, as you suggest, is some sort of stuff. Matter is tiny blobs of this stuff, which have been warped and twisted into particular patterns, and squeezed together. As the stuff expands, it carries matter along with it; a (very) little bit like a sailing ship in the wind.PauloL wrote: ↑Thu Aug 31, 2017 4:45 pm...and not just 2) expanding distances between bodies. Both things are accepted. The universe is expanding and there's a red shift (Doppler's effect from bodies changing relative positions). So expansion is 1) or 2) or both and there's a relation (interaction) between both?
That's interesting indeed.uwot wrote: ↑Thu Aug 31, 2017 8:46 pmThe thing is, we simply don't know whether the universe we see is all there is. Lawrence Krauss wrote a book recently, A Universe from nothing, which basically argues that our universe began as a fluctuation in a pre-existing quantum field, which resulted in a chain reaction. Maybe so. It might also be the case that the same quantum field was created in the Big Bang, but as the evidence is beyond the visible universe, we may never know. Either way, the quantum field (or fields) do appear to have mechanical properties.PauloL wrote: ↑Thu Aug 31, 2017 4:45 pmLet's suppose quite simplistically again that the universe is twice the orbit of the farthest planet. So if next time it's four times that size, universe expanded. If the planets depart to farther positions, but the universe size remain the same I wouldn't say universe expanded.
Part of the excitement around the 'discovery' of the Higgs boson was that a field with mechanical properties was predicted. One of the predictions was that if you hit this field hard enough, you will create a 'ripple' in it that is detectable. The LHC walloped the field, and lo and behold, there was a ripple that looked very like the one predicted.
So yes, empty space is not empty and it does exert a force. My personal hunch is that, regardless of whether the Big Bang started in a true vacuum, or some 'field', 'space' is expanding, and it exerts a push on the things we can see. In effect, it's like a cosmic wind (which is a very loose analogy).
Personally, I think 'dimensions' are relational; I don't think there is any solid evidence that they exist as anything other than a means of locating events. If you just mean the universe is getting bigger, I would agree that is by far the best explanation of the data, but again, this is a subtlety of language that even native English speakers are confused by.The theory is that space, as you suggest, is some sort of stuff. Matter is tiny blobs of this stuff, which have been warped and twisted into particular patterns, and squeezed together. As the stuff expands, it carries matter along with it; a (very) little bit like a sailing ship in the wind.PauloL wrote: ↑Thu Aug 31, 2017 4:45 pm...and not just 2) expanding distances between bodies. Both things are accepted. The universe is expanding and there's a red shift (Doppler's effect from bodies changing relative positions). So expansion is 1) or 2) or both and there's a relation (interaction) between both?
That's interesting indeed.
I'm afraid 'dimensions' really can mean different things. Three spring to mind:
As far as I can tell, you are using 'dimension' in the third sense. Personally, I think it is plausible to think of 'space' as being a substance, Big Bang stuff in my blog, which expands, so that its dimensions in the first sense get bigger. But that is very different to saying that dimensions, in the third sense, expand.
Which is dimensions in the second sense.
Ain't that the truth.
Hi Greta. Hopefully what I've said above answers your questions. Short answer: Not much. But I could be wrong.
Actually, the post did not address the issues I raised at all
Oh. Ok.
Well, of the three I suggested, I think it is reasonable to accept dimensions as a description of spatial extension. I also think it is reasonable to accepts dimensions as descriptions of spatial and temporal location.
I don't think it's really illogical, insofar as there is no logical reason why you shouldn't, I just don't think it is a sound move.
Time makes sense in terms of location. Like spatial dimensions, you start from some arbitrary point; the time now is 2017 and a bit years after some supposed event in the life of a man, who may or may not have existed for example.
No, I don't much care for it myself. What I don't get is where these dimensions are supposed to be. If you went into space and brought back a bucketful of it, is there anywhere in the place you got the bucketful from that now isn't in the bucket? If not, then since you can describe any point within that bucket using 3 dimensions, who needs extra dimensions? If there is somewhere missing in the bucket, then the extra dimensions are not related to x, y and z and anything that exists in the extra dimensions isn't part of what we normally think of as the physical universe.
I've said before that the Planck scale is epistemological rather than ontological. It's the shortest distance, in space or in time, that we could physically measure. It doesn't follow that it is the smallest distance that exists. There could be all sorts of structure beyond the Planck scale; the point Planck was making is that we cannot see it, at least not using light.
I think you are introducing a different concept of dimension, and if it makes sense to you, go for it.
Well, again, time is in one sense simply the number of events, (orbits of Earth, swinging of pendulums, vibrations of caesium etc) either side of t=0. What seems to confuse mathematicians is that you can do the sums either way. So if you analyse a pool break, for instance, the sums are the same for the balls bouncing around the table, as they are for bringing them back into the triangle. Why then, wonder some mathematicians, can't we go back in time? The simple answer is that you are not going to get the universe back into its box.
Height and width and depth are classical dimensions while the curled up ones are [ hypothetical ] quantum dimensions. But wereGreta wrote:
It seems illogical to me to posit height and width and depth and time and then jump to the notion of tiny
curled up dimensions ( usually accompanied by a graphic of an ant crawling around a thin cylindrical surface )
Late ex-forum member and friend, Obvious Leo, said this about the map and territory:surreptitious57 wrote: ↑Fri Sep 01, 2017 9:53 pmHeight and width and depth are classical dimensions while the curled up ones are [ hypothetical ] quantum dimensions. But were they real then there would be no incompatibility between the two. For the worlds happily co exist. There is of course the famous incompatibility between GR and QM but that only pertains to the theories themselves rather than the actual phenomena. And it is why one should never confuse the map with the terrain. Because one is only an approximation of the other. They are not the sameGreta wrote:
It seems illogical to me to posit height and width and depth and time and then jump to the notion of tiny
curled up dimensions ( usually accompanied by a graphic of an ant crawling around a thin cylindrical surface )
I think that is what is happening now. The current models make no explanatory sense. Extend outwards in one direction - a line, dimension one. Move parallel to the line and we have 2D Flatland. Add depth and we have a 3D reality that is locked in stasis until "dimension 4", time, is added. None of these things would seem to exist in themselves in reality, only as approximate correlates and mathematical constructs.Mistaking the map for the territory has been a subject dear to the heart of every philosopher in history because it is an aspect of human perception integral to our make-up and one which has meaning at a great many levels. Entire rainforests have been laid waste for the purpose of producing literature which explores the distinctions between subjective and objective reality, and thus the role of human consciousness in our understanding of the world around us.