Did Hubble get it wrong?

[between3and26characterslon]

Hi Everyone, this is my first post so hopefully the topic title got your attention.

 

I've been thinking about this for some time and I'm getting confused. Hubble's arguement is that the further away an object is the faster it is moving. I understand that type 1a supernovae are used to determine this because thay are standard candles. So it goes if you know how bright something is you can calculate its distance and then by measuring its red shift you can calculate its speed. The results are that the further away something is the faster it is moving so if its twice as far away its moving twice as fast. This would suggest that as an object it moves away it gets faster, it accelerates. Thus the conclusion the Universe is expanding at an accelerating rate.

 

To my knowledge no single object has been shown to have a greater red shift year on year (correct me if I'm wrong).

It's more a case of

 

object 'a' is 'x' distance away and moving at speed 'v' and

object 'b' is '2x' distance and moving at speed '2v'

 

So my problem is this:

 

Object 'b' is twice as far away but we're also seeing it as it was twice as long ago. This suggests that the further back in time you go the faster objects were travelling. Or to put it another way the nearer to the present you get the slower things are travelling. Does this not suggest the expansion of the Universe is slowing down with time?

Edited September 7, 2010 by between3and26characterslon

[Airbrush]

Object 'b' is twice as far away but we're also seeing it as it was twice as long ago. This suggests that the further back in time you go the faster objects were travelling. Or to put it another way the nearer to the present you get the slower things are travelling. Does this not suggest the expansion of the Universe is slowing down with time?

 

Hubble did not get it wrong, or someone would have noticed by now. The experts have had over 70 years to notice something wrong.

 

If something is twice as far away does not mean you are seeing light twice as old. The difference is small, however, and beyond my ability to explain. Some others here can explain better, but they choose not to. Google "Ned Wright Calculator". That explains it but it is hard to follow.

 

The expansion of the universe is speeding up with time. This is only noticeable over VERY great distances, maybe beyond a third the distance to the edge of the observable universe (the Cosmic Microwave Background).

Edited September 7, 2010 by Airbrush

[IM Egdall]

Think about it this way. An object very far away emits some light. Because the object is so very far away, it takes a considerable amount of time for that light to reach us here on Earth. During that time, the universe has expanded. So the frequency of that light has been stretched by the expansion! (And lower frequency is movement towards the red end of the spectrum or red-shift).

 

The object (galaxy) very far away is hardly moving with respect to us (on a cosmic scale). So its red-shift is not due to its motion, but due to the expansion of space itself. In other words, when we see the red-shift of the light from that distant object today; it is not because it is moving away from us, but because the space between the object and us has expanded during the time it took for its light to reach us.

Edited September 13, 2010 by I ME

[between3and26characterslon]

Ok my understanding (and I could be wrong here) is that distant galaxies are accelerating away from us, that this acceleration is due to a force and that this force comes from dark energy.

 

If space is expanding then galaxies are not accelerating and therefore there is no force and no need for dark energy.

 

The problem I have is that local galaxies are not receding from us due to the expansion of space because they are grvitionaly bound. If you were to transport to a galaxy 10bn lightyears away you would see that the local galaxies are not receding form each other because they are gravitionaly bound. If you went anywhere in the universe you would see local galaxies exhibiting the same behaviour.

 

So how can it be at all points in the universe local objects are not receding but at great distances they are receding.

 

 

Ok lets say you were at 1cm on a steel rule, when you look out you see 2cm is not receding, 3cm is not receding 4cm is not etc etc... but cm 90cm is receding. The same must be true at 90cm however, when you look out you see 89cm is not receding, 88cm is not etc etc...

 

Wherever you are on the steel rule you see nearby cm's remaining where they are but the most distant ones receding.

[Airbrush]

So how can it be at all points in the universe local objects are not receding but at great distances they are receding.

 

 

Galaxies are arranged in clusters and clusters of galaxies are arranged in superclusters. Superclusters are gravitationally bound and are not flying apart. The expansion takes place between superclusters. From our supercluster, Virgo, to the next there IS expansion of space. And from our supercluster to another supercluster twice as far away as the next nearest supercluster, space is expanding about twice as fast. The further the next supercluster is from here, the more space is expanding, proportionally.

Edited September 14, 2010 by Airbrush

[between3and26characterslon]

Galaxies are arranged in clusters and clusters of galaxies are arranged in superclusters. Superclusters are gravitationally bound and are not flying apart. The expansion takes place between superclusters. From our supercluster, Virgo, to the next there IS expansion of space. And from our supercluster to another supercluster twice as far away as the next nearest supercluster, space is expanding about twice as fast. The further the next supercluster is from here, the more space is expanding, proportionally.

 

But there are bigger structures in space than superclusters. Superclusters themselves form bigger structures (at least that's according to Prof Stephen Hawking in his documentry 'Universe' on TV the other night)

 

Otherwise what you're saying is there are discrete pockets of matter in the universe surrounded by huge expanses of empty space. The problem is that the distance that you need for space to expand is greater then the average distance between superclusters (that's an educated guess BTW).

 

Also if A (a supercluster) is gravitationaly bound to B (another supercluster) and B to C and C to D and D to..... W and W to X then although A is not bound to X it still can not be that X is receding from A.

 

Lets say for example that everything within 1bn lightyears from us is not receding from us

Andromeda is less than 1bn lightyears away and is bound to The Milkyway

there is another galaxy less than 1bn lightyears from Andromeda which is bound to Andromeda

another galaxy less than 1bn lightyears from that one and so on

 

So I still don't understand how everthing locally can be gravitationaly bound, that this is true wherever you are in the universe and yet the most distant objects are receding form us which is also true wherever you are in the universe.

 

What does make sense (to me) is that soon after the big bang galaxies were moving faster than they were longer after the big bang. When we look at distant galaxies we are seeing them as they were soon after the big bang. When we look at nearer galaxies we are seeing them longer after the big bang and they are moving slower.

 

Imagine you have 1000 big white balls and you place them receding form you in a straight line 1mn lightyears apart so that the one furthest from you is 1bn lightyears away. Now you suddenly expand the space between them. You would not see them all move at once you would observe a wave of movement propagate along the line of balls. It would take 1bn years before you would see the furthest one move. If before the information that the furthest ball has moved had reached you, the distance between the balls suddenly decreased, you would observe a wave of nearby balls getting closer but you would still observe the distant balls receding from you. Although the distant balls have moved closer to you again this information has not reached you yet.

 

Sticking with our white balls, they are all identical in every way, especially mass. Due to their mass they will all attract each other and the gaps between them will reduce equally. Yet due to the expansion of space the two end balls get further away from each other. From your observation point at one end of the line you will see nearby balls getting closer to you and the most distant balls getting further away from you. It is therefore a necessary consequence that one ball somewhere along the line will appear to not move. It is moving towards you due to gravity exactly as much as it is moving away from you due to the expansion of space (if gravity is an acceleration and the universe is expanding at an accelerating rate the net acceleration on this ball will be zero). This will be directly proportional to the sum of masses acting on it and its distance from you. Again this does not make sense. At least, if this phenomenon is proportional to the sum of masses over distance then there must be a constant to describe it and that constant should tell you something.

 

It still makes sense to me that the expansion of the universe is slowing down it just looks like it's expansion is speeding up because we're looking at the past.

 

Where am I going wrong?

Edited September 14, 2010 by between3and26characterslon

[Airbrush]

But there are bigger structures in space than superclusters. Superclusters themselves form bigger structures (at least that's according to Prof Stephen Hawking in his documentry 'Universe' on TV the other night)

 

Otherwise what you're saying is there are discrete pockets of matter in the universe surrounded by huge expanses of empty space. The problem is that the distance that you need for space to expand is greater then the average distance between superclusters (that's an educated guess BTW).

 

It still makes sense to me that the expansion of the universe is slowing down it just looks like it's expansion is speeding up because we're looking at the past.

 

Where am I going wrong?

 

What do they call the structures that are larger than Superclusters? I've never heard that, except the term "fillamentary structures". These are expanding, or stretching apart. All Superclusters are seen to be moving away from each other.

 

The expansion is not slowing down. Cosmologists have already factored into the formula the fact we're looking at the past. Where you're going wrong is the fact you have not studied the links Martin has provided at the top.

Edited September 14, 2010 by Airbrush

[between3and26characterslon]

What do they call the structures that are larger than Superclusters? I've never heard that, except the term "fillamentary structures". These are expanding, or stretching apart. All Superclusters are seen to be moving away from each other.

 

The expansion is not slowing down. Cosmologists have already factored into the formula the fact we're looking at the past. Where you're going wrong is the fact you have not studied the links Martin has provided at the top.

 

 

"Where you're going wrong is the fact you have not studied the links Martin has provided at the top."

 

Could you copy and paste them cos I can't see them.

[Airbrush]

Could you copy and paste them cos I can't see them.

 

Here you are pal. Also see the sticky topics at the top of this department. Martin has included other tutorials and useful sites.

 

http://www.astro.ucla.edu/~wright/cosmolog.htm

[between3and26characterslon]

Here you are pal. Also see the sticky topics at the top of this department. Martin has included other tutorials and useful sites.

 

http://www.astro.ucl...ht/cosmolog.htm

 

Thanks I've had a quick read but will carry on more thoroughly.

 

I am reasonably familiar with the theory and it all made perfect sense to me until a few days ago when it occured to me that the further away something is the longer ago you are seeing it. This has the effect of reversing time so if something is expanding in -t it must be contracting in +t.

 

When this thought happened the whole theory crumbled in my mind

 

So I am left with 3 possibilities

 

1) I don't have all the necessary facts to understand the theory

2) I have all the facts but don't understand them

3) The theory is wrong

 

You can see if 1 and 2 are true why I would think 3 is true

 

I have had a look on the internet and found there are other dessenters among the ranks who don't believe in the expanding universe theory such as proponants of NRI (though this doesn't hold much appeal either)

 

Something interesting I read though was that the expanding universe theory relies on (or implies) the wavelength of light increasing (frequency decreasing) over time and distance and therefore loosing energy whereas Einstein said the the frequency (and wavelength) of light is determined at emition and reception and therefore no loss of energy over time and distance.

[michel123456]

Go on between3and26characterslon(g). I'll call you "g" in the future, if you don't mind. Happy to see thinking people around here.

[Airbrush]

 

...it occured to me that the further away something is the longer ago you are seeing it. This has the effect of reversing time so if something is expanding in -t it must be contracting in +t.

 

When this thought happened the whole theory crumbled in my mind

 

So I am left with 3 possibilities

 

1) I don't have all the necessary facts to understand the theory

2) I have all the facts but don't understand them

3) The theory is wrong

 

 

I really don't understand your dissent. Maybe if you explain it in simpler terms someone can help you out. I think the answer is possibility #1, you don't have all the facts to understand the theory. Why are the experts agreeable with the theory? Are you smarter or more knowledgeable than they are?

[between3and26characterslon]

I really don't understand your dissent. Maybe if you explain it in simpler terms someone can help you out. I think the answer is possibility #1, you don't have all the facts to understand the theory. Why are the experts agreeable with the theory? Are you smarter or more knowledgeable than they are?

 

I completely admit I may not have all the facts but there is nothing wrong in challenging established theory. I am not going to believe something just because I'm told, I can only believe something when it makes sense to me and at the moment the expanding universe does not make sense as I understand it. Therefore I will ask and try to explain my confusion and hopefully reach a better understanding.

 

Not all the experts are agreeable with the theory (most maybe, but not all) and I'm not dissenting, I just said that to be dramatic.

 

Are you smarter or more knowledgeable than they are?

 

I haven't ruled out the possibility

 

What I'm struggling with is this

 

If an object is 1 lightyear away you are seeing it as it was one year ago (just to keep things simple)

 

1 lightyears away = 1 years ago = speed x

2 lightyears away = 2 years ago = speed 2x

4 lightyears away = 4 years ago = speed 4x

 

Based on that if we are looking at someting twice as far away we are seeing it as it was twice as long ago. If we see objects were travelling faster longer ago than objects are nearer to the present then they are slowing down with time not speeding up.

 

Basically Hubble's graph plotted speed against distance and had a "/" slope

 

but if you plot distance against time then from our point of view time would run from -13.7bn to 0 and the graph would have a "\" slope, this would show speed decrease with time. Could you not then change your time values to 0=the big bang and +13.7bn=today and you would still have the same slope on your graph.

 

If I can draw a graph and paste it here I will.

Edited September 17, 2010 by between3and26characterslon

[swansont]

For your scenario, the answer is probably easy: use data from 2 years ago for the 2 LY object and 3 years ago for the 1 LY object. At such distances the speeds are small, and the objects will not have moved much. The more distant object still moves faster.

 

For the broader picture, and more distant objects, the distances used are the distances now, not the distances when the light was emitted.

http://www.astro.ucla.edu/~wright/cosmology_faq.html#DN

[michel123456]

What I'm struggling with is this

 

If an object is 1 lightyear away you are seeing it as it was one year ago (just to keep things simple)

 

 

Step by step.

 

G, you must be ready to deal with a basic space-time diagram.

 

 

If you put yourself at the intersection, all objects you can observe are upon the yellow line.

 

For example (how I like this question), can you see an object 1 lightyear away as it was 2 years ago?

Edited September 17, 2010 by michel123456

[between3and26characterslon]

Swansont

 

I will read

 

 

 

Michel

For example (how I like this question), can you see an object 1 lightyear away as it was 2 years ago?

 

I don't know

Edited September 21, 2010 by between3and26characterslon

[michel123456]

 

For example (how I like this question), can you see an object 1 lightyear away as it was 2 years ago?

 

I don't know

 

Oh yes you know, that is not a very difficult question.

[between3and26characterslon]

Oh yes you know, that is not a very difficult question.

 

 

can you see an object 1 lightyear away as it was 2 years ago?

 

yes

 

 

can you see an object 2 lightyears away as it was 1 year ago?

 

no

[michel123456]

can you see an object 1 lightyear away as it was 2 years ago?

 

yes

 

Are you sure? How do you justify such a statement?

[between3and26characterslon]

Are you sure? How do you justify such a statement?

 

On the notion that the speed of light is finite, it can not travel 2 lightyears in one year but it's not impossible for it to travel 1 lightyear in two years. But ok, if the light has taken 1 year to reach us we will see the object 1 lightyear away.

[michel123456]

But ok, if the light has taken 1 year to reach us we will see the object 1 lightyear away.

 

Right.

SOL is not only finite. SOL is constant (in void).

At the question "can you see an object 1 lightyear away as it was 2 years ago?"

the answer is "no".

 

In other words, all observable objects coincide with the yellow line on the graph. Hypothetical objects that are not upon the yellow diagonal are simply not directly observable.

 

Now you can proceed on step 2 and draw on the graph the speeds of observable objects in function of their distance from us.

Edited September 24, 2010 by michel123456

[between3and26characterslon]

Right.

SOL is not only finite. SOL is constant (in void).

At the question "can you see an object 1 lightyear away as it was 2 years ago?"

the answer is "no".

 

In other words, all observable objects coincide with the yellow line on the graph. Hypothetical objects that are not upon the yellow diagonal are simply not directly observable.

 

Now you can proceed on step 2 and draw on the graph the speeds of observable objects in function of their distance from us.

 

Yep I understand that bit, that's Hubble's graph and the more distant the object the faster it's receding from us.

 

But if 1 lightyear away = 1 year ago (as we have agreed) then on Hubble's graph just substitute on the x axis' lightyears away' for 'years ago'. This will show objects slowing down over time.

 

Do you understand what I'm saying? (sorry if that sounds rude, but if I'm wrong you need to understand why I'm wrong so you can explain in a way I understand)

 

I'm not saying that if you compare data from 50 years ago to data today you will see the same object slow down over that period. What I'm saying is the more distant an object is the further back in time we see it and the further back in time we look the faster objects were receding.

 

Anyway you might be building a case "step by step" so I'll bite my tongue (or fingers in fact) for now.

[IM Egdall]

Yep I understand that bit, that's Hubble's graph and the more distant the object the faster it's receding from us.

 

But if 1 lightyear away = 1 year ago (as we have agreed) then on Hubble's graph just substitute on the x axis' lightyears away' for 'years ago'. This will show objects slowing down over time.

 

Do you understand what I'm saying? (sorry if that sounds rude, but if I'm wrong you need to understand why I'm wrong so you can explain in a way I understand)

 

I'm not saying that if you compare data from 50 years ago to data today you will see the same object slow down over that period. What I'm saying is the more distant an object is the further back in time we see it and the further back in time we look the faster objects were receding.

 

Anyway you might be building a case "step by step" so I'll bite my tongue (or fingers in fact) for now.

 

You say "the further back in time we look the faster objects were receding." The object is NOT receding. The space between the object and us is expanding. This is a fundamentally different point of view which must be taken into account to understand what's going on.

 

So why is there a cosmic red shift? Because expanding space stretches all light waves they propogate, not because receding galaxies are moving though space and exhibit Doppler shift. REF: C. H. Lineweaver, T. D. Davis, "Misconceptions about the Big Bang", SciAm Mar 05

In fact, "galaxies, on average, hardly move through space at all.Their motion is due almost completely to the stretching of space itself." REF: B. Greene, The Fabric of the Cosmos, p. 237.

Edited September 25, 2010 by I ME

[michel123456]

Its not that simple. In a spacetime diagram, look at this:

 

Time elapses from down to up.

At time T=0 you are at point Ao.

You look at Galaxy Bo, in the past, and at Galaxy Co.

After some time, you are at point A1, looking at Galaxy B1, and Galaxy C1.

You are observing that the distance between you & the Galaxies has increased: D1 is greater than Do.

 

Then you join the points B1 & Bo with a line, which is the trajectory of Galaxy B. You do the same for Galaxy C, and you find that the continuation of those lines in the past show a concentration. Reversely, going to the future, it shows an expansion.

 

That's the Theory.

The key point is that we are not in the situation where we can make such observations. The time between To and T1 is equal to million or even billions of years.

[between3and26characterslon]

You say "the further back in time we look the faster objects were receding." The object is NOT receding. The space between the object and us is expanding. This is a fundamentally different point of view which must be taken into account to understand what's going on.

 

So why is there a cosmic red shift? Because expanding space stretches all light waves they propogate, not because receding galaxies are moving though space and exhibit Doppler shift. REF: C. H. Lineweaver, T. D. Davis, "Misconceptions about the Big Bang", SciAm Mar 05

In fact, "galaxies, on average, hardly move through space at all.Their motion is due almost completely to the stretching of space itself." REF: B. Greene, The Fabric of the Cosmos, p. 237.

 

Ok but didn't the Hubble graph show the velocity of receding galaxies. Whether they are moving through space (no) or moving with expanding space (yes) the effect is the same; the distance between us and them increases.

 

 

"Because expanding space stretches all light waves they propogate" I can see that makes sense, I'm not saying that space is not expanding. Really what I'm saying is the universe was expanding faster in the past than it is now. The problem I have with Hubble theory is, as I understand,

 

1) The Hubble constant isn't predicted from theory, it is chosen to fit observations.

2) That gallaxies are accelerating away from us.

2) There must be some sort of force causing this and it's called dark energy (though if gallaxies are not accelerating through space then do we need a force?)

 

 

 

Its not that simple. In a spacetime diagram, look at this:

 

Time elapses from down to up.

At time T=0 you are at point Ao.

You look at Galaxy Bo, in the past, and at Galaxy Co.

After some time, you are at point A1, looking at Galaxy B1, and Galaxy C1.

You are observing that the distance between you & the Galaxies has increased: D1 is greater than Do.

 

Then you join the points B1 & Bo with a line, which is the trajectory of Galaxy B. You do the same for Galaxy C, and you find that the continuation of those lines in the past show a concentration. Reversely, going to the future, it shows an expansion.

 

That's the Theory.

The key point is that we are not in the situation where we can make such observations. The time between To and T1 is equal to million or even billions of years.

 

 

As you say I think that is the sticking point.

 

Anyway, if my graph appears below the righthand side shows Hubble's graph of velocity plotted against distance and, if 1 lightyear away = 1 year ago, the lefthand side shows my graph of velocity plotted against time ago. You'll notice the dots representing galaxies are mirrored (as best as I could) does this not show the expansion slowing down with time. The further back in time you lokk the faster space was expanding??

Edited September 26, 2010 by between3and26characterslon