In its original form the density parameter Omega represented the ratio of the actual density of the universe to the critical density; i.e. the density required to halt the universe’s expansion and that would then cause it to contract. If Omega is greater than one the universe is said to be finite and closed with positive curvature. If Omega is less than one the universe is said to be infinite and open with negative curvature. If Omega is equal to one the universe is said to be open and infinite with zero curvature. According to the Big Bang Theory, the universe contains all the volume that exists and it is not expanding into previously unoccupied space. Regardless of whether the overall geometry is flat, negative or positive the universe has no edge and does not need additional room to expand. This seems to imply that the existing space is being stretched out as the universe expands. However, if space is a something – a substance of sorts - that is influenced by the presence of mass, it would seem that space itself may in a sense possess a certain amount of mass. But if space does possess a certain amount of mass, what happens as this space is thinned out over time? As galaxies are gravitationally stable this does not seem to pose a problem but on an intergalactic scale it would seem that gravitationally the influence of a massive structure such as a galaxy on other galaxies would be changing over time. I am not sure if this was what Einstein was thinking when he made his self-described “greatest blunder” by proposing a cosmological term that acted in opposition to gravity and produced a static universe. As this cosmological term – the cosmological constant - is now a prime candidate for the source of the accelerating expansion of the universe, Einstein may have been right from the beginning. However, the questions I have are: If space is indeed a substance of some sort that can expand and contract, as space expands (intergalactically) would these changes in density affect the predictions of the theory of general relativity? Or is it possible that rather than expanding, new space is somehow constantly being created to maintain a constant density?
According to my meagre understanding, dark energy is increasing as space expands keeping the critical density constant.
That is beautiful were are you going to get the energy , I suppose you are going to get it from the vacuum, or perhaps you are borrowing it from the next big bang, to fit your created equation ? God help you in providing wisdom to create a better model.
The thing that always puzzled me is, we can get a red shift using a moving object in fixed space, such as a train moving away from us. How do you tell the difference between motion in fixed space and motion due to expanding space, since both look the same?
This statement is not very scientific in its wording. What do you mean by "in a sense"? A thing either does or does not have mass. Photons have no mass; that's why light can travel at the speed of light. Protons, electrons and neutrons have mass; that's why matter can't travel at the speed of light.
That's true in the theory of special relativity, not in the general theory. Anyhoo, I believe current theories that are being looked at do include the idea that new space is being created, which explains the expansion. Some names to google are: Rovelli, Smolin and Susskind. I think Smolin wrote an article in SciAm some years ago called "Atoms of Space and Time" which was about spin networks.
One thing to keep in mind is that local forces are stronger than space-fabric expansion. In other words, the forces that bind things (i.e. quarks, atoms, molecules, planets, solar systems, galaxies, et al) are far stronger than cosmic expansion. On most scales... although space itself is expanding, the bound constituents embedded within space will retain their cohesive integrity. Unless something drastic happens, this is how it shall remain.
Relativity doesn't work for all situations so i wouldn't be surprised if it didn't take into account the expansion of space.
The Big Bang Theory is based on Einstein’s general theory of relativity. In order to address the flatness and horizon problems in the original theory, the idea of a short period of rapid inflation was proposed to smooth and flatten the early universe. It is now being questioned that inflation produces the observed universe. In addition the inflation originally proposed was eternal indicating that our universe is not unique but rather that there are an infinity of other universes. Not only is this rather inelegant, but it seems to violate Occams’ razor in that we need to accept an infinity of other universe’s in order to justify our universe. There is also the issue of dark matter. In order to explain the observed rotational velocities of galaxies, a yet to be identified new form of matter is introduced in order for our current theories to be consistent. Absent the introduction of this dark matter it has also been suggested that our current theories of gravitation may need to be modified – at least on the intergalactic scale. There is also the recent observation that the expansion of the universe is accelerating in contradiction to what was previously understood. In order to account for this the idea of a yet to be identified form of energy called dark energy was introduced to match the observed expansion. The most common explanation for this energy is the cosmological constant that was introduced by Einstein in order to produce a stationary universe. The cosmological constant represents the intrinsic vacuum energy of empty space. The problem is that most quantum field theories predict a vacuum energy that would produce an expansion rate that is 120 orders of magnitude greater than the observed expansion. It has been called the worst theoretical prediction in physics. At the dawn of the twenty first century, our understanding of how the universe was born and evolved is still in question. Furthermore we have identified only 3 % of the matter and energy content of the universe. The other 97 % is comprised of yet to be determined dark matter (22%) and dark energy (75%). In addition we do not yet understand what time is or what space is. So no I do not think the science is at all settled on this.
True. Meanwhile no one has found anything to show general relativity is incorrect. The only exception is explaining what is going on inside a black hole, where general relativity and quantum theory clash.
I agree and I think this issue will not be resolved until we have a better understanding of the nature of space and time. More problematic is that our widely accepted understanding of the creation and evolution of the universe – the Big Bang theory – is also based on the general theory of relativity and there is a similar clash between Einstein’s theory and quantum theory in the early universe. But I think the problems here are not limited to this conflict but involve the issues of inflation, dark matter and dark energy I mentioned in my earlier post (#11). The point I was trying to make is that I think there are holes in the Big Bang theory that are significant enough to bring into question the validity of this approach.
Dear conscienta In my opinion, [ Space Doesn't Expand ] After the expansion of universe was observed in the 1920s, physicists and astronomers introduced the concept of "space expands" into physics and many observations and research results were used based on this. However, we can't explain why space expands and why it has a specific velocity and is no observations of expansion of space. This study proves that the expansion of the universe and Hubble's law doesn't result from the expansion of space, but is a dynamical result from the movement of galaxies in space. We could confirm that Hubble's law was always valid when the effect of acceleration was smaller than initial velocity. Also, this shows that cosmological red shift comes out from the Doppler effect of light. Expansion of space was explained that it was related to red shift and scale factor. Therefore, if this discovery is true, all matters related to red shift and scale factor should be reviewed. ~~~~~~~~~~~~~~~~ E. Direct meaning of proof 1) Hubble's law is valid is a very wide area in 3 dimensional space when the initial speed of galaxies is much larger than the velocity change by deceleration and acceleration (in the same meaning, when velocity change by deceleration and acceleration is smaller compared to initial speed). 2) Even though initial velocity isn't much bigger than the effect by deceleration and acceleration, Hubble's law can be valid in some specific condition. For example, xxx 3) Even though Earth isn't the center of the universe, the belief (something not experienced such as "expansion of space”) isn't necessarily needed to explain the reason all galaxies recede from Earth. http://www.sciforums.com/showthread.php?t=112934
Very recently I saw an article that dark matter does not exist at all, according to german scientists (I think). If they cannot say if this something is dark matter than they are playing with fog... https://emsnews.wordpress.com/2012/04/22/dark-matter-does-not-exist-as-i-predicted/ http://www.newscientist.com/article/dn21732-nearby-darkmatterfree-zone-poses-cosmic-conundrum.html
