| how is the universe expanding?
Posted: 5/3/2009 7:08:32 PM | | The universe is defined by what we can observe. What we can observe is expanding. You'll have to cope with it because the evidence disagrees with you. | |
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| how is the universe expanding?
Posted: 5/3/2009 7:47:50 PM | Further to comments about dark energy and dark matter...although neither have ever been observed directly, their presence can be inferred from observations made. Dark energy is pushing the universe apart faster than normal expansion should. Also, dark matter has been observed to be bending the light of background galaxies in specific ways.
None of this is in dispute in most scientific circles although there are some who offer alternative explanations...MOND or Modified Newtonian Dynamics to name one.
the best explanation for the universe is a brief period of hyperexpansion or "inflation." But we are talking within the first few nanoseconds of the universe's existence. | |
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| how is the universe expanding?
Posted: 5/3/2009 9:59:37 PM | | The effects of Dark Matter have been seen as the effects from it's gravity on light has bent it. The only evidence for Dark Energy is the fact that the galaxies that are farther away appear to be traveling faster than those galaxies that are closer to us. As there has been absolutely no other evidence found in the 10 years the Dark Energy hypothesis has been around scientists as a whole are beginning to look elsewhere for explanations. One of those explanations is the hypothesis that separate parts of the universe are expanding at different rates. Hyper expansion really has nothing with either of these hypothesis and is generally accepted amongst the scientific community. | |
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| how is the universe expanding?
Posted: 5/3/2009 10:31:38 PM |
Err no, that's not how it works. Consider the theory of epicycles. I won't bore you with an explanation, but in general (although not always), the newer theory explains more with less. Occam's Razor.
Occam's Razor isn't used like that. There's an another name for that; the appeal to novelty. | |
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| how is the universe expanding?
Posted: 5/3/2009 10:46:00 PM |
Gravity is the thing keeping it all together both microscopic and macroscopic.
Gravity is in fact the weakest fundamental force in universe.
Simple magnet shows that Electromagnetism is stronger than gravity.
Gravity isn't keeping our bodies together, but the Electromagnetic forces between molecules. | |
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| how is the universe expanding?
Posted: 5/4/2009 4:16:11 AM | There are various lines of evidence that indicate the (observable) universe is expanding. The universe may or may not be infinite, or it may be a subset of a number of universes, possibly infinite in number. No-one seems to know, and no-one seems to have devised a method of determining if our universe is the only physical world that exists.
There is the CMBR and redshifts. The ways these are calculated are quite complex and good explanations (either at the layman's level or in more sophisticated books) can be found elsewhere in good astronomy books. The poster who said GR has solutions that admit expanding (or shrinking) rather than stable universes is correct, though I don't have the math skills to prove it. Again, you can find pretty good treatments in various books on physics, relativity, cosmology, astronomy etc, if you can use calculus and above. A basic grasp of why the universe expands doesn't require mathematical genius. The universe also appears to be accelerating in expansion, perhaps due to 'dark energy' or a nonzero cosmological constant.
There is a lot we don't understand about the universe (such as how it emerged from a singularity or why, and also most of what it is made of) but expansion seems pretty well established on the evidence. | |
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| how is the universe expanding?
Posted: 5/4/2009 11:58:41 AM |
the universe is expanding. And it's not just the material in the universe, it's spacetime as well. That's an observed and observable fact.
Sorry, the theory that spacetime is expanding is just a theory, there is no proof, nor is it considered fact. All we know is that the further away we can see, objects are accelerating. At the 'hubble limit' we no longer can observe anything. Some say its because the expansion past this point is faster than the speed of light, and therefore light beyond this limit cannot reach us.
To make this congruent with relativity, where light speed is the ultimate speed, some theorize that spacetime itself is expanding rather than any objects moving faster than the speed of light.
Just theory. No one knows. | |
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| how is the universe expanding?
Posted: 5/4/2009 12:03:51 PM |
Gravity is in fact the weakest fundamental force in universe.
Don't be too sure about that. If the Apollo astronauts had left a magnet on the moon, there is no way you could build a magnet here to attract that magnet back home. Yet, the earth holds the moon in orbit over that distance. Sounds like in this case gravity is far stronger than magnetism. | |
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| how is the universe expanding?
Posted: 5/4/2009 12:36:50 PM | We don't even know they are moving away - we infer it from red/blue-shift. There was a "tired light" theory knocking around a few years ago, but it doesn't fit well with other observations. It would be a brave physicist indeed who challenged the theory now however, given the weight of evidence in favour of it.
Occam's Razor isn't used like that. There's an another name for that; the appeal to novelty.
With respect to Occam's Razor, somethink like "do not multiply entities beyond neccessity" most certainly does apply to physics, like everything else. Scientists are deeply uneasy about the increasing appeal to "dark stuff" that theoretical physics needs to explain observational fact. It seems to me, that supporting the paradigm `just because' is a rather nonsensical philosophy to have. Why not recognise there's a problem?! | |
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| how is the universe expanding?
Posted: 5/4/2009 1:28:20 PM | Space is created as the universe expands. It started as a singularity, and has grown from there over billions of years.
It is also likely - and this is now generally accepted by most cosmologists - that our universe is only one of a multiverse. This is implied by string theory, and people are working on ways to find ways to test this. If so, there are an infinite number of possible universes, few if any just like our own. Some expand, some are stable, some eventually contract. | |
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| how is the universe expanding?
Posted: 5/4/2009 2:15:01 PM |
Gravity is in fact the weakest fundamental force in universe.
Don't be too sure about that. If the Apollo astronauts had left a magnet on the moon, there is no way you could build a magnet here to attract that magnet back home. Yet, the earth holds the moon in orbit over that distance. Sounds like in this case gravity is far stronger than magnetism.
If they left a giant, moon-sized magnet you'd have to hold on to you braces. | |
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| how is the universe expanding?
Posted: 5/4/2009 4:54:30 PM | Sorry, the theory that spacetime is expanding is just a theory, there is no proof, nor is it considered fact.
The theory that atoms exist is just a theory, too. The redshifts of galxies are observable facts. The microwave background radiation is an observable fact. The anomalous precession of mercury is an observable fact. General relativity is the only theory consistent with the facts. The alternatives all strive to be indistinguishable from general relativity in the hope of ruling out one or the other in the future. However, just like general relativity reduces to newtonian gravity in the limit of small velocities and weak gravitational fields, any theory which supercedes general relativity must reduce to general relativity in some limit. The extent to which the expansion of the universe is not considered to be a fact by the physics community is pretty much limited to the likelyhood of some stunning revelation that has no precedent in science.
To make this congruent with relativity, where light speed is the ultimate speed, some theorize that spacetime itself is expanding rather than any objects moving faster than the speed of light.
That isn't true at all. The postulated expansion of the universe predicted the existence of the microwave background radiation prior to its discovery by Penzias and Wilson, (who weren't looking for it when they discovered it). The observed redshift is another indicator. It's not ``some theorize.'' It's widely accepted by physicists. Anybody can be a skeptic.
Don't be too sure about that. If the Apollo astronauts had left a magnet on the moon, there is no way you could build a magnet here to attract that magnet back home. Yet, the earth holds the moon in orbit over that distance. Sounds like in this case gravity is far stronger than magnetism.
That's a bizarre comment. First of all, gravity is not a force in general relativity. Second, if you characterize the strenght of the gravitational field relative to the electromagnetic field, the difference in strength is a factor of about 10^39, with gravity being the weaker. However, it's easy enough to calculate for yourself. Figure out the difference in the gravitational and electromagnetic interactions for two protons separated by the same distance. Scale that up to the moon and earth masses for two balls of protons.
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| how is the universe expanding?
Posted: 5/4/2009 5:58:05 PM |
Sorry, the theory that spacetime is expanding is just a theory, there is no proof
Once again, we confuse "theory" with "hypothesis." Established theory such as the Big Bang is far more robust because it has observation to back it up.
An expanding spacetime is part and parcel to Big Bang cosmology and General Relativity, not the least of which comes from the observation that this expansion is accelerating. | |
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| how is the universe expanding?
Posted: 5/4/2009 6:02:14 PM |
The observed redshift is another indicator. It's not ``some theorize.'' It's widely accepted by physicists. Anybody can be a skeptic.
Yep, redshift has been proven to work in labs and at much shorter distances than far away galaxies. Data from redshift has been compared with other methods of measuring distances of stars/galaxies and they agree within 10%.
As hard as it is to accept dark energy, the implications alternate explanations redshift such MOND or bubble in space with do not share our physical constants are even more bizzare. | |
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| how is the universe expanding?
Posted: 5/4/2009 6:03:57 PM |
If the Apollo astronauts had left a magnet on the moon, there is no way you could build a magnet here to attract that magnet back home.
Obviously, "strength" is scaled. On the subatomic scale, gravity is the weakest by several factors. | |
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| how is the universe expanding?
Posted: 5/4/2009 6:12:20 PM |
Obviously, "strength" is scaled. On the subatomic scale, gravity is the weakest by several factors.
If you jump off a building that acceleration you feel on the way down is gravity, that splat you feel when you hit the pavement is acceleration(deacceleration in this case) atomic electromagnetic bonding energy. | |
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| how is the universe expanding?
Posted: 5/4/2009 11:24:00 PM |
With respect to Occam's Razor, somethink like "do not multiply entities beyond neccessity" most certainly does apply to physics, like everything else. Scientists are deeply uneasy about the increasing appeal to "dark stuff" that theoretical physics needs to explain observational fact. It seems to me, that supporting the paradigm `just because' is a rather nonsensical philosophy to have. Why not recognise there's a problem?!
Of course it applies to physics, but it doesn't mean that newer theories are better than old or that unverified simpler theory is better than highly verified theory with calculable but unidentified variable.
Problem is to indentify the unknown variables.
There are similar problems with gravity as well. We know pretty much how it works, but no idea why it works. That's why there's hypothesized to be a particle called graviton. However graviton is much more hypothetical than dark energy, because we can calculate the force dark energy is creating based on observations. | |
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| how is the universe expanding?
Posted: 5/5/2009 12:19:32 PM |
Of course it applies to physics, but it doesn't mean that newer theories are better than old or that unverified simpler theory is better than highly verified theory with calculable but unidentified variable.
The beauty of general relativity is that it can derived from only one assumption, that inertial mass is equiavlent to gravitational mass. This is exactly the assumption Newton made, but Newton newton made a further assumption that general relativity does NOT make. Newton assumed the geometry of the universe was invariant under Galilean transformations. That was what led Einstein to realize that the full consequences of the equivalence principle. General relativity makes no assumption about the geometry of the universe. The mathematics apply to a n-dimensional space of arbitrary signature (although there might be an upper limit on the number of dimensions.) Eliminating the restriction to a Galilean universe eliminated gravity as a force. General relativity is generally covariant and one can always find a local coordinate system in which the gravitational foece disappears. Since a real force cannot be made to vanish by a change of coordinates, gravity is not a force.
Problem is to indentify the unknown variables.
There is only one unknown variable in general relativity, the cosmological constant. But the reason for that can be made obvious by noting that the integral of some function always contains an arbitrary constant. The constant G is not intriniscally relevant to general relativity. It only has meaning when including the electromagnetic, weak and strong forces.
We know pretty much how it works, but no idea why it works.
But asking that question is exactly the same question as ``Why can't I flatten a sphere into a plane?'' The reason is that a sphere has an intrinsic curvature so no coordinate transformation can map the points of a sphere to a plane (which has no intrinsic curvature). By contrast, a cylinder has no intrinsic curvature. It can be ``unrolled'' into a plane. If you and anothe person follow walk along the meridians of a sphere (the geodesics or ``straightest lines''), at a constant velocity, you will each see the other as accelerating towrds you as you meet at one of the poles, yet there is no force exerted ny either of you upon the other. However, if you did not realize your two-dimensional universe was really curved, you would invent a force to explain what you naively observed in the same way Newton did. | |
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| how is the universe expanding?
Posted: 5/5/2009 1:24:52 PM |
The theory that atoms exist is just a theory, too. You are awrae the most powerful microscopes can see atoms right? There have been pictures of atoms in various recent scientific journals. You probably mean that the nucleus of an atom is just a theory. This is because we can't actually see the nucleus of the atom as it is completely enshrouded in an electron cloud. However we know it exists because energy passed through that electron cloud mostly passes through. However there is a small point in the center where it is bounced back.
The point in the center is so small, I've read, that, if expanded to the size of a solar system, the cloud would be hundreds of times farther out than the farthest object in our solar system is from the Sun. | |
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| how is the universe expanding?
Posted: 5/5/2009 1:56:07 PM | Simplest answer:
The universe is being compressed and divided within a finite space. It's fractal. People always think of infinity as only infinitely large and not infinitely small at the same time.
Check the work of Nassim Haramein, pretty cool stuff. Did you know inside every atom/sun/planet there's a black hole? :) | |
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| how is the universe expanding?
Posted: 5/5/2009 2:27:36 PM | Tooters in half smashed
its fractal? is it! personally i dont think you actually know what that means
check the works of that boxer? no thank you maam.( Naseem Hamed joke get it?)
Perhaps you meant its infinite and almost impossible to imagine in that guiser scenerio of infinity ( i can assure you its most definitively measurable to us mere mortals) and we be but a humble grain of sand formed by molecules through chance.and indeed through fractal geometry,lobs in the lizard king too. into what we are, and best shape if no solely round _ though I doubt that fits in with in any gravitational laws spliced of dissected to the fundamental quantum particles and there bestest arrangement cos everything is fractal is is.. posh word aint it
staggers back oot
what? tis valid to ramblings surely not!
eek so am no too cheeky or obtuse bes test shape is round :) which is perhaps why i consume so many muffins, as frankly wicked wants to obrtain perfection..and believe fractal geometry has its own thread on this forum at least twice ( i forget their names)
Personally i didnt understand the gist of one. mind u the other weren't bad at all.
sprites off into the ether at a gallop | |
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| how is the universe expanding?
Posted: 5/6/2009 10:24:00 AM | Atoms do exist, but there not the smallest particle. Not even close. In truth there can not be a smallest particle, cause this would mean that where those two particles met, non-existence would have to be. Non-existence is impossible! There is no seperation, all of existence is ONE. Dont confuse the term matter with the term existence. Existence is all there is, the definition of non-existence is that it does not exist. So we are all connected through existence.
I know this contradicts motion:
My theory is that what we call energy runs through all existence, including ourselves. Since there is no seperation, motion is impossible. So motion must be just a transfer of that energy. Motion is an oppitcal illusion, since we cant see the essence of existence/energy, it appears to our eyes, that things move from one unoccupied space to the next, but this is impossible, cause existence/energy is always there. | |
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| how is the universe expanding?
Posted: 5/6/2009 4:08:09 PM |
My theory is that what we call energy runs through all existence, including ourselves...etc.
Okay then. Get thee to the next astrophysics conference and offer up a paper. Quite frankly, on the surface, your theory sounds not much different from some of the musings of the world's top physicists. However, the one thing they have on their side is the actual math that expresses what they propose.
Good luck and have fun. | |
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| how is the universe expanding?
Posted: 5/6/2009 6:37:18 PM | stargazer1000, don't all mathematical expressions of existence point out that properties can only be transfered in balancing steps, rather than outright moved.
I don't believe math allows one to just pluck out and move values across that big old = sign. | |
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| how is the universe expanding?
Posted: 5/7/2009 7:42:53 AM | Think of it this way: the universe is a large a balloon being blown up by a nondenominational deity. Someday, it will burst.
If the big bang theory is correct, the universe has expanded many times, reaching its "potential" and then imploding. Maybe there are many universes out there, exploding, expanding, imploding on a regular basis. | |
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