Universe contracting

[pastori]

Hello,

I have a problem with the proof provided for universe expanding. Isn't it that any observation to support the expansion is based on light. Wouldn't it be that all the observations would be exactly the same if all the galaxies were heading towards a gravitational pull? Any object would seem to move further away because the light between the points bends towards the gravitational source with higher pace than the actual distance between the two points are contracting. (Hubbles redshift would happen etc.). Even the points in same contracting line.

Edited October 31, 2015 by pastori

[fiveworlds]

Isn't it that any observation to support the expansion is based on light.

 

It is based on the light from the observable universe. There is also the unobservable universe the rest of the universe we don't know about.

[Sorcerer]

I normally ask more questions here than answer, but if this were the case we would observe differences in red shifts between stars which are closer to the gravity source than us an stars which are further away from it than us. Gravity roughly follows an inverse square law stars closer would show greater red shift.

 

So basically we don't observe the universe as would be expected if your hypothesis was correct. Red shifts are pretty consistent in all directions.

[Strange]

I have a problem with the proof provided for universe expanding. Isn't it that any observation to support the expansion is based on light.

 

Not all the evidence for the big bang is based on light.

 

Wouldn't it be that all the observations would be exactly the same if all the galaxies were heading towards a gravitational pull?

 

If they were moving towards us, they would be blue shifted. If they were moving away they would be red-shifted. They are red0shifted and therefore moving away. I don't see how a contracting universe could produce the same effect.

 

Any object would seem to move further away because the light between the points bends towards the gravitational source with higher pace than the actual distance between the two points are contracting. (Hubbles redshift would happen etc.). Even the points in same contracting line.

 

I really don't understand what you are trying to say there. Perhaps you could show us the maths and/or a diagram to explain it?

[michel123456]

Not all the evidence for the big bang is based on light.

 

 

If they were moving towards us, they would be blue shifted. If they were moving away they would be red-shifted. They are red0shifted and therefore moving away. I don't see how a contracting universe could produce the same effect.

 

 

I really don't understand what you are trying to say there. Perhaps you could show us the maths and/or a diagram to explain it?

It is simple.

Take a law that says that an attractive force increases as the square of the distance. It means the more closer you get to an object, the more attracted you are. Then take an object that lies on the same attractive line with you. The object that is in front of you (closer to the attractive point) will be seen by you as going away from you. The object that is behind you (farther to the attractive point) will also be observed by you as going away.

Of course, another object, on the opposite side of the attractive point, will be observed as approaching.

The "trick" then is to put the attractive point sufficiently far away such that no opposite object can be observed. In this case, all observable objects are lying upon parallel paths. And they will observe each other as getting away from each other.

[Strange]

I'm still not clear why an object that is moving towards you would look as if it is moving away. What causes that illusion?

 

 

Take a law that says that an attractive force increases as the square of the distance. It means the more closer you get to an object, the more attracted you are.

 

Yes, but how is that relevant to apparent motion?

 

 

Then take an object that lies on the same attractive line with you. The object that is in front of you (closer to the attractive point) will be seen by you as going away from you.

 

Do you mean because it IS going away from you because it is attracted to the more distant object?

 

 

The object that is behind you (farther to the attractive point) will also be observed by you as going away.

 

So is this supposed to be some sort of tidal effect?

 

If so, then I can see this might apply in a very limited case in a single direction (but I would like to see that math that confirms this). I fail to see how it could apply to every object in every direction.

[michel123456]

I'm still not clear why an object that is moving towards you would look as if it is moving away. What causes that illusion?

It is not about an object going towards you. It is about 3 objects going in the same direction towards a center of attraction. All 3 objects on the same line will observe as going away from each other. It is caused by acceleration and it is not an illusion.

[Strange]

It is not about an object going towards you. It is about 3 objects going in the same direction towards a center of attraction. All 3 objects on the same line will observe as going away from each other. It is caused by acceleration and it is not an illusion.

 

OK. But...

 

1. Will the speed be proportional to distance? (which is why I would like to see the maths)

 

2. Does this bear any relationship to anything we observe in the real world?

 

3. What does this have to do with a contracting universe?

Edited November 1, 2015 by Strange

[pastori]

My apologies for starting the thread on just an idea and nothing to back it up. Just a thought. So to respond i dont have the math nor I have the skills or mind to do it. I guess I'm in the wrong place.

The basic idea was that if two galaxies are accelerating towards the gravitational pull and the distance between them is closing but the light between the two observers is bending at a higher accelerating rate then would every object we observe seem getting away from us at an accelerating fashion (would gravitational redshift apply)?.

[Strange]

That's OK. It is fine to ask questions.

 

I'm not sure why you think gravity would have that effect; the bending or red-shift of light by gravity is a very small effect and only noticeable under very special situations.

 

However, the good news is that the same theory that explains gravity (General Relativity) also explains the expansion of the universe; so you are kinda on the right track!

[Strange]

Someone (maybe the OP under a different name) asked a very similar question on another forum; suggesting that all galaxies were falling towards a common point and that their increasing separation as they fall is what we observe.

 

It was easier to understand what was meant, but that fails for the same reasons outlined here but even more so - not only does it only work in one dimension, but the galaxies at right angles to the direction of fall would be converging.

[michel123456]

Someone (maybe the OP under a different name) asked a very similar question on another forum; suggesting that all galaxies were falling towards a common point and that their increasing separation as they fall is what we observe.

 

It was easier to understand what was meant, but that fails for the same reasons outlined here but even more so - not only does it only work in one dimension, but the galaxies at right angles to the direction of fall would be converging.

The delay combined with acceleration is the thing that cause the objects looking as expanding.

Because if all objects are not delayed, it ressemble a tsunami wave: all objects are forming a front.

Once you introduce a delay (meaning that some objects will reach the goal after some others) AND acceleration, THEN you obtain the increasing distance between the faling objects.

So you have to take count of the delay caused by the constancy of SOL.

And there is always such a delay. It is not possible to observe an hypothetical galaxy "at right angle" that would belong to the same front with us. Such a galaxy lies in our future.

Edited November 2, 2015 by michel123456

[Strange]

The delay combined with acceleration is the thing that cause the objects looking as expanding.

 

I don't see where the delay comes into it. I am also still not convinced there will be a linear relationship between distance and speed. Perhaps you need to show us the maths for that.

 

 

It is not possible to observe an hypothetical galaxy "at right angle" that would belong to the same front with us. Such a galaxy lies in our future.

 

Although I have no idea why you would claim that, you are back to only being able to see galaxies in a one dimensional line. This still doesn't match the universe we live in.

 

But if there are galaxies all around us falling to a common point then there is no reason we would not be able to see those which are not directly ahead and behind; these other galaxies would be getting closer to as as we all converge. And that doesn't match what we see either.

 

This model doesn't appear to match reality.

 

Also, how long have these galaxies been accelerating towards some central point without getting there?

 

And, if you are rejecting General Relativity (the current explanation for expansion) you need a new explanation for gravity.

Edited November 2, 2015 by Strange

[michel123456]

You are sitting in your car, waiting at the red light. There is a car in front of you, and another car behind you.
At T=0, the red light turns green, and the first car starts.
After one second, you start.
After 2 seconds, the car behind you starts. The one second gap is the delay.
What are you observing?
The car in front of you accelerates. You are accelerating too, but the gap of one second between the 2 cars provoques an increasing distance. If both cars have the same acceleration, you will observe the preceding car getting away.
What about the car behind you? If you look in the mirror, you will observe that the distance is also increasing, for the exact same reason.
So, in this situation, where all cars have the same acceleration combined with a 1 sec. delay, all observators will see the distance between the cars increase. The distance between the 3 cars is actually increasing, it is an expanding configuration.

Now, forget the cars.

In the universe, there are no red lights. But there is light.
Light propagates at SOL. Because SOL is a constant, the image we get of the universe is delayed. The further we look, the more the delay.
When we look at a galaxy 100 Light Years away, we are looking at the galaxy as it was 100 years ago. Exactly as if we looked at a car not 1 sec. behind us, but 100 years behind us. The delay is 100 years.

So, IF (if) we are accelerating, and IF (if) we are accelerating at the same rate, we should not be surprised to observe this galaxy receding from us. And what is most interesting, is that the further the Galaxy will be, the more receding it will be. The receding speed will observe a simple law increasing proportionaly in function of the distance. Exactly as predicted by Hubble's Law.

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Posted 28 May 2010 - 04:12 PM

Agree.
But because the delay is caused by C, we know that the distance & the delay are linked. The distance measured to an object is also the delay, because C is constant.
When D=1000 LY, T(delay) is 1 Year. Roughly.

So, 2 elements of the equation are known. When a is known, only v is unknown.

The equations give V (not D) as difference of velocity between 2 objects.

[math]v=d/t[/math]
[math]a=v/t[/math]
[math]d=1/2 at^2[/math]

Let's suppose 2 objects (p) & (q)

[math]D=d_p-d_q[/math] (4) where [math]D[/math] is the distance between the 2 accelerated objects.

We know that [math]T=t_p-t_q[/math] (5) where [math]T[/math] is the time interval, the delay.
and we know that
[math]D=c\ T[/math] (6) where [math]c[/math] is Speed Of Light

then

[math]D=c\ t_p-t_q[/math](7)
and thus
[math]t_p-t_q=D/c[/math](8)

The difference of velocity is [math]V=v_p-v_q[/math](9)
and
[math]v_p=at_p[/math](10)
[math]v_q=at_q[/math](11)
V=a(t_p-t_q)(12)

replacing [math](t_p-t_q)[/math] with [math]D/c[/math]see(8)

we obtain

[math]V=a D/c[/math] or

[math]V=\frac{a}{c} D[/math] (11)

Hubble's Law is [math]V=H_o D[/math] (1)

The speculation of this thread is that [math]\frac{a}{c}=H_o[/math] by comparison of (11) & (1) see also(2bis)

 

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All the above copy-pasted from an old thread of mine back in 2010

And as a note: it works in more than 1 dimension, because the delay is observed in 3D. There is no point nowhere around us that is not influenced by the delay caused by the constancy of SOL.

Edited November 2, 2015 by michel123456

[imatfaal]

 

I don't see where the delay comes into it. I am also still not convinced there will be a linear relationship between distance and speed. Perhaps you need to show us the maths for that.... snipped

 

 

 

Posit Galaxy A at set distance with a known redshift - we can establish a mass called M at a distance from Galaxy A that would provide a red-shift which is similar to that which we observe the light from Galaxy A being subject to.

 

Now put in place Galaxies A- and A+ respectively closer to and further from earth - the observed redshift is linear with distance between Earth and the observed galaxy; ie the change in redshift between A- and A will be

Change in redshift observed = Constant * [( Earth to A-) less (Earth to A)] . In the model proposed the

change in red shift predicted = Constant * [ (A- to M)^-1 - (A to M)^-1 ]

 

Whilst you might be able to finagle this with two galaxies - once you add in A+ and a wide range of distances there is no constant or manipulation that would allow a decreasing 1/[distance] mimic an increasing [distance]. So I think you are completely correct in your point that linearity will not be maintained

[Strange]

And as a note: it works in more than 1 dimension, because the delay is observed in 3D. There is no point nowhere around us that is not influenced by the delay caused by the constancy of SOL.

 

As imatfaal says, I don't accept that this works in the general case.

 

Also, I don't see how this works in more than 1 dimension. Extend your traffic lights to a cross roads. Now there are cars accelerating past you as well as in the same direction as you. How is it you see those cars passing in front of you to be moving away?

Also, F=ma. Where is the force coming from to accelerate all these galaxies?

 

 

All the above copy-pasted from an old thread of mine back in 2010

 

So having been shown that it doesn't work, you are repeating it anyway?

[michel123456]

 

Posit Galaxy A at set distance with a known redshift - we can establish a mass called M at a distance from Galaxy A that would provide a red-shift which is similar to that which we observe the light from Galaxy A being subject to.

 

Now put in place Galaxies A- and A+ respectively closer to and further from earth - the observed redshift is linear with distance between Earth and the observed galaxy; ie the change in redshift between A- and A will be

Change in redshift observed = Constant * [( Earth to A-) less (Earth to A)] . In the model proposed the

change in red shift predicted = Constant * [ (A- to M)^-1 - (A to M)^-1 ]

 

Whilst you might be able to finagle this with two galaxies - once you add in A+ and a wide range of distances there is no constant or manipulation that would allow a decreasing 1/[distance] mimic an increasing [distance]. So I think you are completely correct in your point that linearity will not be maintained

I understand only your first sentence. Please explain again the rest. Thanks.

There is no decreasing 1/[distance]. There is increasing distance between the objects. The distance to the attractive point is not considered, only the distance beween the attracted objects.

Like the distance between drops of rain.

 

As imatfaal says, I don't accept that this works in the general case.

 

Also, I don't see how this works in more than 1 dimension. Extend your traffic lights to a cross roads. Now there are cars accelerating past you as well as in the same direction as you. How is it you see those cars passing in front of you to be moving away?

Also, F=ma. Where is the force coming from to accelerate all these galaxies?

 

 

So having been shown that it doesn't work, you are repeating it anyway?

Because people believe it works only in the case where the objects are aligned.

But in this new case, the delay is not produced by an object having started before or after another. Here the delay is produced by observation.

 

The scenario is a huge set of objects travelling in parallel paths under a common acceleration, with the source of acceleration so far away that all paths are parallel.

It is about the same thing as considering a source of expansive push very very far away on the other side. Except that we have at hand no known force for a push, what we have is a force for a pull.

Edited November 2, 2015 by michel123456

[Strange]

The scenario is a huge set of objects travelling in parallel paths under a common acceleration, with the source of acceleration so far away that all paths are parallel.

 

If everything is moving in parallel paths, then you are back to a 1D model.

 

To take your traffic light analogy again. If there are multiple lanes on the road, then the cars in the adjacent lanes will stay the same distance away. The fact that the light is delayed will not make them appear to be receding.

 

It is about the same thing as considering a source of expansive push very very far away on the other side. Except that we have at hand no known force for a push, what we have is a force for a pull.

 

Whether it is a pull or a push, what is supposed to be causing this force (which appear to remain constant regardless of distance)?

There is no decreasing 1/[distance]. There is increasing distance between the objects. The distance to the attractive point is not considered, only the distance beween the attracted objects.

 

Please show the maths for the general case of N objects.

Edited November 2, 2015 by Strange

[Janus]

And there is always such a delay. It is not possible to observe an hypothetical galaxy "at right angle" that would belong to the same front with us. Such a galaxy lies in our future.

Of course it is possible to observe such a galaxy.

 

 

Start with the example of two spaceships traveling side by side. If one ship shoots a light at the other ship ( at a right angle to their motion), that light from the frame of the ships travels straight across and hits the other ship, regardless of the distance between the ships or the time delay between transmission and reception due to the SoL.

Now if the ships fie up their engines and are accelerating, that same light will appear to curve in the frame of the ships. The same happens to the light if they are firing their engines in order to stay stationary with respect to a gravity source.

Now what happens if the ships, in that gravity field cut their engines and repeat the experiment. To someone stationary to the gravity source they will accelerate towards it. But at the same time the light will follow a curve due to the gravity, and the end result will be that the light fired from one ship at a right angle will hit the other ship just like it did when the ships were in inertial motion. IOW, from the frame of the falling ships, the light goes straight across with no curve, just like the ships were at rest.

 

The same is true for two galaxies an equal distance from and falling side by side to a gravity source. The transmission delay due to the SoL has no effect on what they see of each other. They both see each other at right angles to the line of acceleration. and if they are falling perfectly parallel to each other they will see no Doppler shift.

You also get no net Doppler shift between the two if you examine things from the frame at rest with respect to the gravity source. In this frame there are two counteracting effects. The first is due to the difference in velocities between the transmitting and receiving galaxy. Since the receiving galaxy will have accelerated in the time it takes for the light to cross the distance between the two, it will be moving faster at reception than the other galaxy was at transmission, and this results in a red-shift from its perspective.

However, the transmitting galaxy was also higher in the gravity field when the light left it that the receiving galaxy is when it arrives, and that results in a perceived blue-shift. And since the both difference in velocity and thus the red-shift and the gravitational blue shift are dependent on the difference in gravitational potential, they cancel each other out leaving no net Doppler effect.

 

So, two galaxies falling inward side by side and parallel will see each other side by side and will see no Doppler shift regardless of the distance between them.

 

But what about two galaxies falling inward towards a central point? If we start with two galaxies, each an equal distance from the source and falling along radials an angle theta apart we can analyze it the flowing way:

 

If we draw a line between these galaxies, then from either galaxy, that line will be 90-theta/2 degrees from the radial pointing towards the central point. If we draw a third radial such that it crosses this line at a right angle, it will bisect the radials of the two galaxies. If we consider the motion of the galaxies with reference to this radial they will have two components: one along the radial and one along the line joining the two galaxies.

The motion along the radial is just like the example of two galaxies falling parallel to each other, in that it results in no net Doppler shift. The component along the line joining the two galaxies give them velocities towards each other and thus results in a net blue shift.

 

The upshot is that two galaxies falling inward along radials theta degrees apart and an equal distance from the central point will see each other at an angle of 90-theta/2 degrees from the line of their own acceleration and Blue-shifted.

Falling inward towards a central source will not result in equal red-shifts in all directions that are proportional with distance.

[michel123456]

Of course it is possible to observe such a galaxy.

Start with the example of two spaceships traveling side by side. If one ship shoots a light at the other ship ( at a right angle to their motion), that light from the frame of the ships travels straight across and hits the other ship, regardless of the distance between the ships or the time delay between transmission and reception due to the SoL.

Yes.

Now if the ships fie up their engines and are accelerating, that same light will appear to curve in the frame of the ships. The same happens to the light if they are firing their engines in order to stay stationary with respect to a gravity source.

?? Light appears always as traveling in straight line. There will exist an angle between the apparent source and the point where the source is calculated to be.

And that means that the source of the light is (was) not where the source currently is.

Now what happens if the ships, in that gravity field cut their engines and repeat the experiment. To someone stationary to the gravity source they will accelerate towards it. But at the same time the light will follow a curve due to the gravity, and the end result will be that the light fired from one ship at a right angle will hit the other ship just like it did when the ships were in inertial motion. IOW, from the frame of the falling ships, the light goes straight across with no curve, just like the ships were at rest.

I have to believe you.

The same is true for two galaxies an equal distance from and falling side by side to a gravity source.

The transmission delay due to the SoL has no effect on what they see of each other.

They both see each other at right angles to the line of acceleration.

and if they are falling perfectly parallel to each other they will see no Doppler shift.

I have to believe you.

You also get no net Doppler shift between the two if you examine things from the frame at rest with respect to the gravity source. In this frame there are two counteracting effects. The first is due to the difference in velocities between the transmitting and receiving galaxy. Since the receiving galaxy will have accelerated in the time it takes for the light to cross the distance between the two, it will be moving faster at reception than the other galaxy was at transmission, and this results in a red-shift from its perspective.

That was my point. Because acceleration is taking place, and delay occurs naturally in observation, both effects result in redshift.

However, the transmitting galaxy was also higher in the gravity field when the light left it that the receiving galaxy is when it arrives, and that results in a perceived blue-shift. And since the both difference in velocity and thus the red-shift and the gravitational blue shift are dependent on the difference in gravitational potential, they cancel each other out leaving no net Doppler effect.

Oh. Are they both dependent on the distance, or distance squared?

So, two galaxies falling inward side by side and parallel will see each other side by side and will see no Doppler shift regardless of the distance between them.

Oho. I must be wrong then. Wait: see each other side by side?? The one cannot see the other as it is today, but as it was a long time ago, thus not side by side (because side by side is what happens in the present)

But what about two galaxies falling inward towards a central point? If we start with two galaxies, each an equal distance from the source and falling along radials an angle theta apart we can analyze it the flowing way:

 

If we draw a line between these galaxies, then from either galaxy, that line will be 90-theta/2 degrees from the radial pointing towards the central point. If we draw a third radial such that it crosses this line at a right angle, it will bisect the radials of the two galaxies. If we consider the motion of the galaxies with reference to this radial they will have two components: one along the radial and one along the line joining the two galaxies.

The motion along the radial is just like the example of two galaxies falling parallel to each other, in that it results in no net Doppler shift. The component along the line joining the two galaxies give them velocities towards each other and thus results in a net blue shift.

 

The upshot is that two galaxies falling inward along radials theta degrees apart and an equal distance from the central point will see each other at an angle of 90-theta/2 degrees from the line of their own acceleration and Blue-shifted.

Falling inward towards a central source will not result in equal red-shifts in all directions that are proportional with distance.

Interesting. Not surprising. That was not my scenario though.

Edited November 3, 2015 by michel123456

[Mordred]

To add to an earlier comment by Strange. Redshift isn't the only evidence of an expanding universe. One of the most commonly and strangely enough biggest piece of evidence is thermodynamic evidence. An expanding universe cools.

 

Pv=nRt.

 

I'm often amazed how often the temperature history is overlooked. Lol

Edited November 10, 2015 by Mordred

[michel123456]

The misunderstanding is also elsewhere.

 

The drops of rain falling on Earth belong to a system that expands. I mean each drop is getting away from all the others (except the ones falling exactly side by side).

[Strange]

The drops of rain falling on Earth belong to a system that expands. I mean each drop is getting away from all the others (except the ones falling exactly side by side).

 

Not true. Firstly, the drops are all falling at (roughly) the same speed (terminal velocity). And the drops that are side by side are (in principle) getting closer together as they are falling radially.

[michel123456]

 

Not true. Firstly, the drops are all falling at (roughly) the same speed (terminal velocity). And the drops that are side by side are (in principle) getting closer together as they are falling radially.

Right. I should have stated without friction. And considering the drops falling in parallel, not radially.

The drops are in free fall accelerating towards the Earth surface

[Strange]

Right. I should have stated without friction. And considering the drops falling in parallel, not radially.

The drops are in free fall accelerating towards the Earth surface

 

And in this (physically unrealistic) scenario it is still not isotropic - there will be increasing separation between the drops in one direction but not the other. (And did you ever show us the maths to prove that speed of separation is proportional to distance? Or did I just miss it?)

 

Also, sooner or later, the drops will hit the ground.

 

So none of this seems relevant to cosmology.