Universe expansion

[ACG52]

You are linking to 'Lifeslittilemysteries.com' as though it was a legitimate source?

 

 

I have been studying cosmology for a long time, mostly from the papers I have read on the internet

 

I have a hard time beliving that. OTOH, if your internet studying has been on crank sites, without any background or educational background which would allow you to discriminate between fact and woo-woo, I can see how you would be confused.

[Jdizz]

Red shift value did not appear in the past post.

Without any acceleration, the expansion or contraction speed can not approach to the certain value.

Always initial velocity is zero.

 

Check out this pdf:

 

http://docs.google.com/open?id=0B_6N6Q10PWKhVkdLTlZUYjd3Vj

 

Earth would be at the center of the universe due to the ACCELERATION of the expansion since it is combined with Hubble's law according to which the cosmological redshift of galaxies is the same for all galaxies having the same distance from Earth in all radial directions.

[Spyman]

A diagram depicting the expansion of the universe and the appearance of galaxies moving away from a single galaxy. The phenomenon is relative to the observer. Object t1 is a smaller expansion than t2. Each section represents the movement of the red galaxies over the white galaxies for comparison. The blue and green galaxies are markers to show which galaxy is the same one (fixed center point) in the subsequent box. t = time.

http://en.wikipedia.org/wiki/Metric_expansion_of_space

 

 

In physical cosmology, the Copernican principle, named after Nicolaus Copernicus, states that the Earth is not in a central, specially favored position. More recently, the principle has been generalized to the relativistic concept that humans are not privileged observers of the universe.

/../

Measurements of the effects of the cosmic microwave background radiation in the dynamics of distant astrophysical systems in 2000 proved the Copernican principle on a cosmological scale. The radiation that pervades the universe was demonstrably warmer at earlier times. Uniform cooling of the cosmic microwave background over billions of years is explainable only if the universe is experiencing a metric expansion.

http://en.wikipedia.org/wiki/Copernican_Principle

Edited December 20, 2012 by Spyman

[Roger_XR]

Ok AGC52,

I've been doing a bit more studying. This time I got some material from astro.ucla.edu. This particular paper was rather well written but there is more I need to study. For example; It stated that "The high redshift supernovae (Type 1A) are fainter than would be expected." They did not write their paper to answer my particular question but the question would be: If we look outward and the furthermost object (what we see at 13 billion light years say) had a particular speed, then when we look at another object closer to us in time at say about 11 billion light years is slower in speed, and another object at about 9 billion light years is slower in speed, and continuing in this way all the back to our local group, which is slower still, then why could we not say that the Universe is in fact slowing down not speeding up? Could we not say that the very early Universe was indeed moving at a fast speed (relatively) but as time goes on the Universe has slowed down to the speed we notice today? (and No I do not mean just our local group).

[ACG52]

 

If we look outward and the furthermost object (what we see at 13 billion light years say) had a particular speed, then when we look at another object closer to us in time at say about 11 billion light years is slower in speed, and another object at about 9 billion light years is slower in speed, and continuing in this way all the back to our local group, which is slower still, then why could we not say that the Universe is in fact slowing down not speeding up?

 

 

No, because from the pov of the 13 billion ly galaxy, the closer you get to our galaxy, the faster everything is receeding.

 

This is not about objects moving through spacetime, this is about more space continually appearing between all (non-gravitationally bound) objects. The further apart two points in space are, the more new space appears between them , and so the faster the objects appears to be receeding.

[Roger_XR]

 

No, because from the pov of the 13 billion ly galaxy, the closer you get to our galaxy, the faster everything is receeding.

 

But would not that part of the galaxy that you say is receding have occured first and started its outward travel at that point. (Time equal zero) That part of the galaxy was there long before even our local group was created?

 

You and I will just have to disagree on that part about "new space" being formed from nothing. I understand that there are people that believe that but it sounds more like science fiction to me.

 

One other thing I thought of, If we can "see" an object at 13.7 billion light years and it took the light 13.7 billion years to reach us (less perhaps because we were closer to that point at one time - though still billions of years) then the age of the Universe would have to be greater than 13.7 billion years old.

[ACG52]

The light from the 13 billion ly object started traveling towards us when it was only about 400 million lys away. As it traveled toward us, the expansion of space streatched it into a 13 billion year trip.

 

 

 

You and I will just have to disagree on that part about "new space" being formed from nothing. I understand that there are people that believe that but it sounds more like science fiction to me.

 

 

This is an argument from incredulity.

 

 

 

But would not that part of the galaxy that you say is receding have occured first and started its outward travel at that point. (Time equal zero) That part of the galaxy was there long before even our local group was created?

 

 

No, everything started receeding from everything else at the same time. There is no 'outward travel'. Just continuing spatial expansion.

[zapatos]

I have read that the Universe began with a Big Bang and grew in size from there. I have read that there was no single place that the Universe started and therefore had no center or no edge. Which to believe?

Actually these two statements are not at odds with each other. The Big Bang is not similar to an explosion where debris is thrown out from the center. The Big Bang started everywhere at once and the universe grew in size.

[Roger_XR]

 

 

 

This is an argument from incredulity.

 

 

I also don't necessarily believe in God - another argument from incredulity - but I'll need more proof than just your word for it. Know a website that can offer proof for me to read?

Edited December 22, 2012 by Roger_XR

[zapatos]

Know a website that can offer proof for me to read?

You might want to try this:

 

The metric expansion of space is the increase of the distance between two distant parts of the universe with time. It is an intrinsic expansion whereby the scale of space itself is changed. That is, a metric expansion is defined by an increase in distance between parts of the universe even without those parts "moving" anywhere. This is not the same as any usual concept of motion, or any kind of expansion of objects "outward" into other "preexisting" space, or any kind of explosion of matter which is commonly experienced on earth.

http://en.wikipedia.org/wiki/Metric_expansion_of_space

[Roger_XR]

Actually these two statements are not at odds with each other. The Big Bang is not similar to an explosion where debris is thrown out from the center. The Big Bang started everywhere at once and the universe grew in size.

Yeah, I've heard that. I just don't think even our best minds can know that for a fact. I feel that to many people take what someone else has said as the absolute truth. Is it true? Maybe. But what if it's wrong? Then we will continue to believe that and stop all effort to research any other thought that might not fit with the current thinking but which may in fact be right. The scientists that come up with any given theory have a vested interest in making sure that theory is maintained. But of course it won't really matter. If there's a Big Crunch or an Infinite Expansion we'll be long dead.

[zapatos]

 

Yeah, I've heard that. I just don't think even our best minds can know that for a fact. I feel that to many people take what someone else has said as the absolute truth. Is it true? Maybe. But what if it's wrong? Then we will continue to believe that and stop all effort to research any other thought that might not fit with the current thinking but which may in fact be right. The scientists that come up with any given theory have a vested interest in making sure that theory is maintained. But of course it won't really matter. If there's a Big Crunch or an Infinite Expansion we'll be long dead.

The best minds certainly don't know that for a fact, and don't make such a claim. They could be wrong and there are people who disagree. However, the evidence and the interpretation of the evidence makes a very solid case that this is indeed what is happening.

 

And I wouldn't worry about efforts being stopped to confirm whether or not it is true. There would be no greater glory and discovery in a scientist's career than to find a major problem with a generally accepted theory. Scientists who have a vested interest in the current theory hold no sway over the research of others.

[Roger_XR]

You might want to try this:

 

http://en.wikipedia.org/wiki/Metric_expansion_of_space

I do hate to be a doubting Thomas but your link says in part, "This model is valid in the present era only on large scales (roughly the scale of galaxy clusters and above). At smaller scales matter has become bound together under the influence of gravitational attraction and such bound objects clumps do not expand at the metric expansion rate as the universe ages, though they continue to recede from one another."

Do you see how this explanation tries to hedge its bet by saying that it is but it isn't valid. The Universe is the same through out. At one time everything was VERY close together and would have had a certain degree of attraction to everything else. Yet the Universe expanded anyway. And I HAVE read other theories that say it was indeed a Big Bang.

 

You might want to try this:

 

http://en.wikipedia.org/wiki/Metric_expansion_of_space

I do hate to be a doubting Thomas but your link says in part, "This model is valid in the present era only on large scales (roughly the scale of galaxy clusters and above). At smaller scales matter has become bound together under the influence of gravitational attraction and such bound objects clumps do not expand at the metric expansion rate as the universe ages, though they continue to recede from one another."

Do you see how this explanation tries to hedge its bet by saying that it is but it isn't valid. The Universe is the same through out. At one time everything was VERY close together and would have had a certain degree of attraction to everything else. Yet the Universe expanded anyway. And I HAVE read other theories that say it was indeed a Big Bang.

 

The best minds certainly don't know that for a fact, and don't make such a claim. They could be wrong and there are people who disagree. However, the evidence and the interpretation of the evidence makes a very solid case that this is indeed what is happening.

 

And I wouldn't worry about efforts being stopped to confirm whether or not it is true. There would be no greater glory and discovery in a scientist's career than to find a major problem with a generally accepted theory. Scientists who have a vested interest in the current theory hold no sway over the research of others.

Wish that were all there was to the story. If you're a scientists, you likely work for a University. Now just frow what you said, the evidence "makes a very solid case" and everybody is going to believe that thinking. If you don't have tenure you had better believe it too. What if you had a theory that disproved Einstein? (and I've heard a few actually) Such theories don't hold up well because Einstein is almost sacrosanct so anything that goes against Einstein is obviously wrong. So maybe I don't trust the scientific community so much. I've lived a long time and I've seen a few things. It's what I think.

[StringJunky]

 

I do hate to be a doubting Thomas but your link says in part, "This model is valid in the present era only on large scales (roughly the scale of galaxy clusters and above). At smaller scales matter has become bound together under the influence of gravitational attraction and such bound objects clumps do not expand at the metric expansion rate as the universe ages, though they continue to recede from one another."

Do you see how this explanation tries to hedge its bet by saying that it is but it isn't valid. The Universe is the same through out. At one time everything was VERY close together and would have had a certain degree of attraction to everything else. Yet the Universe expanded anyway. And I HAVE read other theories that say it was indeed a Big Bang.

 

Wish that were all there was to the story. If you're a scientists, you likely work for a University. Now just frow what you said, the evidence "makes a very solid case" and everybody is going to believe that thinking. If you don't have tenure you had better believe it too. What if you had a theory that disproved Einstein? (and I've heard a few actually) Such theories don't hold up well because Einstein is almost sacrosanct so anything that goes against Einstein is obviously wrong. So maybe I don't trust the scientific community so much. I've lived a long time and I've seen a few things. It's what I think.

 

You are reading it wrong. In the very early universe the energies at that time (it was super-hot and very dense) were massive enough to overwhelm gravity and caused a very rapid expansion throughout the WHOLE universe...everything was affected but in the present day the expansion only dominates between galaxy clusters; within the boundaries of the clusters gravity dominates. That's why the expansion is only valid between between clusters now. Using the word 'valid' was a poor choice of word by the author, in my opinion, because of it's ambiguity...'expressed' would have been better, for example.

 

You are so far away from the truth about the scientific process. Einstein's theories are not sacrosanct. I bet right this minute there are many thousands of competent scientists working and dreaming of knocking him off his pedestal but to date his theories still stand, but, as has been learnt, GR is not applicable at the subatomic level so it's not the whole story.

 

Alternative ideas don't hold up because they don't hold up to scientific scrutiny...Einstein's got nothing to do with it .

Edited December 22, 2012 by StringJunky

[juanrga]

Yeah, I've heard that. I just don't think even our best minds can know that for a fact. I feel that to many people take what someone else has said as the absolute truth. Is it true? Maybe. But what if it's wrong? Then we will continue to believe that and stop all effort to research any other thought that might not fit with the current thinking but which may in fact be right. The scientists that come up with any given theory have a vested interest in making sure that theory is maintained. But of course it won't really matter. If there's a Big Crunch or an Infinite Expansion we'll be long dead.

 

Science does not deal with the "absolute truth" this is a task best left for religions, each one of the which has its own "absolute truth" . Science deals with evidence: observations and experiments.

 

Scientific knowledge is accumulative. Scientific theories are not shown to be wrong and abandoned, but older scientific theories are incorporated as special cases of newest theories.

[Roger_XR]

 

You are reading it wrong. In the very early universe the energies at that time (it was super-hot and very dense) were massive enough to overwhelm gravity and caused a very rapid expansion throughout the WHOLE universe...everything was affected but in the present day the expansion only dominates between galaxy clusters; within the boundaries of the clusters gravity dominates. That's why the expansion is only valid between between clusters now. Using the word 'valid' was a poor choice of word by the author, in my opinion, because of it's ambiguity...'expressed' would have been better, for example.

 

You are so far away from the truth about the scientific process. Einstein's theories are not sacrosanct. I bet right this minute there are many thousands of competent scientists working and dreaming of knocking him off his pedestal but to date his theories still stand, but, as has been learnt, GR is not applicable at the subatomic level so it's not the whole story.

 

Alternative ideas don't hold up because they don't hold up to scientific scrutiny...Einstein's got nothing to do with it .

I agree of course that the early Universe was very hot and the energy of that time easily overcame the effect of gravity. And it just now occured to me that perhaps we take gravity for granted. I've been hearing about the Higgs Boson. It is thought that this particle may be responsible for giving an object mass. Therefore, since "gravity is the agent that gives weight to objects with mass", (From Wikipedia, the free encyclopedia) can we know if gravity existed at the moment of the Big Bang. In other words did the Higgs Boson exist at the time of the Big Bang? Without the affect of gravity and in the presence of a huge explosive force, all matter (I assume in the form of subatomic particles) would have flown out at tremendous velocity. Before that can be answered I guess we'll have to wait for them to confirm the Higgs Boson and then try to figure if it could have existed at the moment before the Big Bang.

 

Now as for Einstein, He used GR to calculate the trajectory of a light particle around a massive object (such as our Sun or another Galaxy) instead of Newtonian physics. Very smart but the conclusion he drew from it I think is wrong. Wrapped space? A photon of light is not the same as the mass of a rock (of whatever size). A photon is affected by gravity, but of course a photon is also a wave particle so it could be expected that the effect on the photon would be very different. So as you can no doubt guess I do not believe in wrapped space.

[A Tripolation]

Now as for Einstein, He used GR to calculate the trajectory of a light particle around a massive object (such as our Sun or another Galaxy) instead of Newtonian physics. Very smart but the conclusion he drew from it I think is wrong. Wrapped space? A photon of light is not the same as the mass of a rock (of whatever size). A photon is affected by gravity, but of course a photon is also a wave particle so it could be expected that the effect on the photon would be very different. So as you can no doubt guess I do not believe in wrapped space.

 

Reality doesn't particularly care what you believe in.

Your issue seems to be with the fact that since photons are massless, they shouldn't be affected by gravity. A common source of confusion for laypeople, but I'm surprised someone with a chemistry degree is puzzled by this.

 

Photons aren't directly influenced by the gravitational field of an object, but they are still confined to the geodesics of the spacetime through which they travel. The light traveling around objects is bent due to the curvature of that particular area.

 

The empirical data for this phenomena is astounding and voluminous. We know it's true from gravitational lensing of celestial bodies, and tests performed within our own solar system (radio waves traversing near the sun took longer than they should have to come back).

 

Continuing to "not believe" in one of the primary ramifications of general relativity doesn't lend much credence to you.

[Roger_XR]

 

Reality doesn't particularly care what you believe in.

Your issue seems to be with the fact that since photons are massless, they shouldn't be affected by gravity. A common source of confusion for laypeople, but I'm surprised someone with a chemistry degree is puzzled by this.

 

Photons aren't directly influenced by the gravitational field of an object, but they are still confined to the geodesics of the spacetime through which they travel. The light traveling around objects is bent due to the curvature of that particular area.

 

The empirical data for this phenomena is astounding and voluminous. We know it's true from gravitational lensing of celestial bodies, and tests performed within our own solar system (radio waves traversing near the sun took longer than they should have to come back).

 

Continuing to "not believe" in one of the primary ramifications of general relativity doesn't lend much credence to you.

Go back and re-read what I wrote. NEVER did I say that photons shouldn't be affected by gravity. I know and have known about the experiment that Einstein did to visulize the light of stars behind a total eclipse. (about 1917 I think in Austrlia) First you say that, "Your issue seems to be with the fact that since photons are massless, they shouldn't be affected by gravity." But then you go on to say, "Photons aren't directly influenced by the gravitational field..." So I'm not real sure which one you believe. I DO believe that the photons ARE influenced directly by gravity. However you cannot (as I stated) us Netonian physics to compute the effect on photons. Occam's razor, which as you know states that, "among competing hypotheses, the one that makes the fewest assumptions should be selected." It is easier to believe that gravity, which we have known all our lives, is bending the light instead of the "warping" of space. Also I might point out that at one time it was believed that the Earth was flat. You would have pretty much have to be crazy to believe otherwise. Just because Einstein (who, don't get me wrong, was a VERY smart man) came up with the warping of space as a concept, does not mean he was right (at least about this one thing.) Nor am I the only one to ever question Einstein. Nevertheless, each of the examples you stated could also be explained by gravity effecting the light or radio waves. However, can you quote a experiment in which gravity was excluded as the cause? Everything I have heard is of light passing by a very massive object (the Sun, a galaxy, ect.) Which by the way have gravity.

Please if you're going to quote me, at least READ what it was I said. OKay?

 

 

 

[ACG52]

 

It is easier to believe...

 

 

This seems to sum up all your arguments.

 

 

[Roger_XR]

 

This seems to sum up all your arguments.

 

 

Okay big guy, if you have two competing hypotheses for which you CANNOT prove either one, How do YOU chose? The one that everyone else believes in or think for yourself? Have you ever had an original idea on the subject? The easier chose is to go with the mainstream dogma.

[ACG52]

Okay big guy, if you have two competing hypotheses for which you CANNOT prove either one, How do YOU chose? The one that everyone else believes in or think for yourself? Have you ever had an original idea on the subject? The easier chose is to go with the mainstream dogma.

 

I pick the one which does a better, more accurate job of describing how the physical universe works. To judge which one that is, I look at predictions each make and then compare them to the result of observation and experiment.

 

Cranks chant the 'original idea' mantra, but never seem concerned with 'educated idea'.

[StringJunky]

However, can you quote a experiment in which gravity was excluded as the cause? Everything I have heard is of light passing by a very massive object (the Sun, a galaxy, ect.) Which by the way have gravity.

 

Nobody's excluding gravity; gravity is warped spacetime (space and time) NOT warped space alone. Spacetime tells matter how to move and matter (mass-energy really) tells spacetime how to to bend. If you can visualise it you can see how objects (including photons) follow paths defined by the curvature in spacetime called 'geodesics' which are the shortest possible, paths in that environment. It's a *geometric description of how things behave, as described by General Relativity...to date, data and experiments support it rather well to the limit near singularities.

 

* GR doesn't say what spacetime is only how it behaves and it describes it mathematically....physics is only interested in how things behave and how they measure. It's only us novices that fret about a classical real-world description of difficult-to-grasp physical phenomena. The thing is that, in stuff like this, there are often no real-world correlates that accurately describe these things, instead, we have to rely on the approximate real-world analogies that the scientists give us. The hard truth is that if we want to really understand it we need strong university-level math skills and much time to wade through a book like Gravitation by Misner, Thorne and Wheeler, which is about 1200 pages of heavy-going and a good dent in your wallet...proper science books are dear!

 

 

How do YOU chose? The one that everyone else believes in or think for yourself? Have you ever had an original idea on the subject? The easier chose is to go with the mainstream dogma.

 

This brings to mind something Benjamin Franklin said that seems pertinent here: He who teaches himself has a fool for a master.

Edited December 23, 2012 by StringJunky

[zapatos]

The easier chose is to go with the mainstream dogma.

You seem for some reason to have a bias against currently accepted science, choosing alternatives simply because they are not part of the consensus. An indicator of your bias is your use of the word dogma and the insinuation that acceptance of a particularly well supported theory is done out of convenience.

[Roger_XR]

 

I pick the one which does a better, more accurate job of describing how the physical universe works. To judge which one that is, I look at predictions each make and then compare them to the result of observation and experiment.

 

Cranks chant the 'original idea' mantra, but never seem concerned with 'educated idea'.

Rather I think you mean educated guess, You did not address the conversation about warping of space versus the mere bending of light by gravity. Did you use to read a lot of science fiction? You use very few words with little fact of things that I've already (usually) seen on the internet but with a dose of really rude thrown in.

 

You seem for some reason to have a bias against currently accepted science, choosing alternatives simply because they are not part of the consensus. An indicator of your bias is your use of the word dogma and the insinuation that acceptance of a particularly well supported theory is done out of convenience.

To a certain extent we need "currently accepted science" upon which to build upon. However, when that "currently" accepted science stands in the way of (in my opinion) advancements in that science, then the current view must be questioned. As I've pointed out before, there were those that believed that the Earth was flat. That was the "currently accepted science" of that time. Okay, "science" is probably not the correct term. But it was the current belief at the time. To choose "warpped space" over simple gravity effect is done in part because it is the "currently accepted science" and probably because it was Einstein that said it. Is there a better reason to believe in warpped space? I always listen (even to ACG52 - he's a bit rude but he tries).

I probably wouldn't have used the term "convenience" but if I have a certain bias (as I am sure I must) I believe everyone else does also. No problem with that really. I only ask for an open mind. If I am right or if I am wrong, to me at least I try to put ideas out there that challenge the "currently accepted science".

 

 

Nobody's excluding gravity; gravity is warped spacetime (space and time) NOT warped space alone. Spacetime tells matter how to move and matter (mass-energy really) tells spacetime how to to bend. If you can visualise it you can see how objects (including photons) follow paths defined by the curvature in spacetime called 'geodesics' which are the shortest possible, paths in that environment. It's a *geometric description of how things behave, as described by General Relativity...to date, data and experiments support it rather well to the limit near singularities.

 

* GR doesn't say what spacetime is only how it behaves and it describes it mathematically....physics is only interested in how things behave and how they measure. It's only us novices that fret about a classical real-world description of difficult-to-grasp physical phenomena. The thing is that, in stuff like this, there are often no real-world correlates that accurately describe these things, instead, we have to rely on the approximate real-world analogies that the scientists give us. The hard truth is that if we want to really understand it we need strong university-level math skills and much time to wade through a book like Gravitation by Misner, Thorne and Wheeler, which is about 1200 pages of heavy-going and a good dent in your wallet...proper science books are dear!

 

 

 

This brings to mind something Benjamin Franklin said that seems pertinent here: He who teaches himself has a fool for a master.

Funny thing about math in this field is that (apparently) you can make it say whatever you want. I'll explain. I saw a show on TV where a scientist had an idea of - I believe he called them "banes" anyway these were like different realities of this Universe. But he went on to say that he had to invent a whole new math to explain it.

Space Time: In relativistic contexts, time cannot be separated from the three dimensions of space, because the observed rate at which time passes for an object depends on the object's velocity relative to the observer and also on the strength of gravitational fields, which can slow the passage of time. As for that other stuff you were saying - Spacetime tells matter how to move....ect. Sorry, that sounds pretty strange.

[StringJunky]

As for that other stuff you were saying - Spacetime tells matter how to move....ect. Sorry, that sounds pretty strange.

 

 

Here's a couple of animations that might make it clearer. It's worth reading the page they are from too:

 

Newton's Universe: http://einstein.stanford.edu/Media/Newtons_Universe_Anima-Flash.html

 

Einstein's Universe: http://einstein.stanford.edu/Media/Einsteins_Universe_Anima-Flash.html

 

From: http://einstein.stanford.edu/SPACETIME/spacetime2.html

Edited December 23, 2012 by StringJunky