The Naked Scientists

The Naked Scientists Forum

Author Topic: Can we measure 'expansion'  (Read 29497 times)

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11999
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Can we measure 'expansion'
« on: 13/03/2009 16:10:36 »
If space is expanding, shouldn't that be measurable inside our solarsystem?


 

Offline Vern

  • Neilep Level Member
  • ******
  • Posts: 2072
    • View Profile
    • Photonics
Can we measure 'expansion'
« Reply #1 on: 13/03/2009 16:26:42 »
I would be more inclined to accept the notion of expansion if there was even a measure of it within our own galaxy.
 

lyner

  • Guest
Can we measure 'expansion'
« Reply #2 on: 13/03/2009 17:06:53 »
Do you not accept Hubble's data? Remember, the attractive forces within a galaxy could mean that the mean expansion could be less than the effect between galaxies. Using the Hubble constant, you could work out how much you'd expect over galactic distances.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11999
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Can we measure 'expansion'
« Reply #3 on: 13/03/2009 18:40:44 »
Take a look here. http://www.thenakedscientists.com/forum/index.php?topic=20927.msg236644#msg236644
If that is correct, shouldn't the same phenomena happen here? Even if gravity 'won' I still think we should notice it as it seems to state that the gravitational effects should be weaker inside any 'mass' distribution, or am I thinking wrong here. Would it be as lights 'redshift' with the exception of us not noticing anything at all?
 

Offline Burt Brinn

  • First timers
  • *
  • Posts: 3
    • View Profile
Can we measure 'expansion'
« Reply #4 on: 13/03/2009 19:16:00 »
From what little I understand of expansion, I heard that it is the space in between molecules that is expanding.  So I would expect that your ruler would be experiencing expansion also.  But that is just me going out on a very fragile limb.
 

Offline Vern

  • Neilep Level Member
  • ******
  • Posts: 2072
    • View Profile
    • Photonics
Can we measure 'expansion'
« Reply #5 on: 13/03/2009 19:36:02 »
Do you not accept Hubble's data? Remember, the attractive forces within a galaxy could mean that the mean expansion could be less than the effect between galaxies. Using the Hubble constant, you could work out how much you'd expect over galactic distances.

I accept Hubble's data and the gigantic amount of data accumulated since. But I don't like the idea of space expanding. I keep looking for someone to come up with a better explanation that will fit the observations. I know that we do not presently have such a better explanation.
 

lyner

  • Guest
Can we measure 'expansion'
« Reply #6 on: 13/03/2009 20:09:11 »
Better? I think it's really quite satisfying. It's a lot less bollocks than many other ideas I've read on these pages!
But I'm increasingly convinced that there's no 'right' answer. The best answer is the one which ties most things together.
Why should there be an ultimate truth, in any case?
Time to turn off the switch when that happens.
« Last Edit: 13/03/2009 20:11:15 by sophiecentaur »
 

Offline Vern

  • Neilep Level Member
  • ******
  • Posts: 2072
    • View Profile
    • Photonics
Can we measure 'expansion'
« Reply #7 on: 13/03/2009 22:22:47 »
We have to accept the notion that empty space is not simply empty space. That is the part that don't sit well with me. Not only is space something; but it is something that can expand and an accelerating rate and take gigantibillions of galaxies worth of mass with it. Such space must generate unimaginable power to do that.

We don't know of anything in our physical experience that can do that, nor do we have any physical laws of nature that can predict that kind of expansion.
« Last Edit: 13/03/2009 22:29:07 by Vern »
 

lyner

  • Guest
Can we measure 'expansion'
« Reply #8 on: 13/03/2009 22:52:46 »
I think you are looking for a solution which involves very familiar concepts. That is too much to ask for. After all, if you lived in 1909, you wouldn't be able to understand what has happened in the subsequent 100 years using the familiar ideas of the day.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11999
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Can we measure 'expansion'
« Reply #9 on: 13/03/2009 23:36:50 »
We have to accept the notion that empty space is not simply empty space. That is the part that don't sit well with me. Not only is space something; but it is something that can expand and an accelerating rate and take gigantibillions of galaxies worth of mass with it. Such space must generate unimaginable power to do that.

We don't know of anything in our physical experience that can do that, nor do we have any physical laws of nature that can predict that kind of expansion.

I think you have a good point there Vern.  I wonder if anyone have counted on how much energy it would take to move the milky way :) But then again I'm not sure what energy  would be seen as before it's in our 'neighborhood'. I don't write 'spacetime' as I suspect that this vacuum may have a different view on it than we do? Even though it all should belong together, possibly :)
« Last Edit: 14/03/2009 11:18:33 by yor_on »
 

Offline Vern

  • Neilep Level Member
  • ******
  • Posts: 2072
    • View Profile
    • Photonics
Can we measure 'expansion'
« Reply #10 on: 13/03/2009 23:53:41 »
Quote from: sophiecentaur
I think you are looking for a solution which involves very familiar concepts. That is too much to ask for. After all, if you lived in 1909, you wouldn't be able to understand what has happened in the subsequent 100 years using the familiar ideas of the day.
I think that one idea that was popular around the year 1900, if we had incubated it, would have provided a much better view of nature than the current developments provide. That idea was: the final irreducible constituent of all physical reality is the electromagnetic field.

That idea is not incompatible with any experimental evidence that we can find. However that idea is incompatible with just about every modern theory.

I felt kinda blind sided when I woke up one morning and all of a sudden it was okay to consider the universe as expanding at an accelerating rate; I didn't see that coming. I didn't see any great study that defined the properties of space that would demand that expansion. The only properties of empty space that I know about are magnetic permeability and electric permittivity.
« Last Edit: 13/03/2009 23:59:52 by Vern »
 

Offline Vern

  • Neilep Level Member
  • ******
  • Posts: 2072
    • View Profile
    • Photonics
Can we measure 'expansion'
« Reply #11 on: 14/03/2009 00:07:56 »
Quote from: yor_on
I think you have a good point there Vern.  I wonder if anyone have counted on how much energy it would take to move the milky way :) But then again I'm not sure what energy  would be seen as before it's in our 'neighborhood'. I don't write 'sapcetime' as I suspect that this vacuum may have a different view on it than we do? Even though it all should belong together, possibly :)
I get the feeling when reading about new concepts that are accepted within the scientific community that some entity somewhere imagines themselves capable of describing nature such that nature gleefully becomes as they describe it. I suspect that we can only hope to discover what nature is like. We can not dictate that it must be this way or that way.
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
Can we measure 'expansion'
« Reply #12 on: 14/03/2009 10:42:55 »
We have to accept the notion that empty space is not simply empty space. That is the part that don't sit well with me. Not only is space something; but it is something that can expand and an accelerating rate and take gigantibillions of galaxies worth of mass with it. Such space must generate unimaginable power to do that.

We don't know of anything in our physical experience that can do that, nor do we have any physical laws of nature that can predict that kind of expansion.

I think you have a good point there Vern.  I wonder if anyone have counted on how much energy it would take to move the milky way :) But then again I'm not sure what energy  would be seen as before it's in our 'neighborhood'. I don't write 'sapcetime' as I suspect that this vacuum may have a different view on it than we do? Even though it all should belong together, possibly :)

But the Milky Way and other galaxies are not moving due to expansion. Nothing is pushing them apart. Space is expanding but the galaxies are stationary within space.

In any case, whole superclusters of galaxies are moving due to gravity and that is a very weak force compared to EM, and the weak & strong forces.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11999
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Can we measure 'expansion'
« Reply #13 on: 14/03/2009 11:28:07 »
DB you are correct in that it's space that is expanding, but that must 'push' on those galaxies too. So either it is a 'force' acting upon space. In that case the energy inherent in that force seems to be enormous, or else it's something totally different and 'force'  shouldn't be used for describing it, assuming that there is a expanding universe and that the culprit is vacuum.
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
Can we measure 'expansion'
« Reply #14 on: 14/03/2009 11:43:13 »
DB you are correct in that it's space that is expanding, but that must 'push' on those galaxies too.

But that implies the galaxies are moving due to the expansion and they aren't. Within their bit of space they are stationary apart from their movement due to gravity.
 

Offline Vern

  • Neilep Level Member
  • ******
  • Posts: 2072
    • View Profile
    • Photonics
Can we measure 'expansion'
« Reply #15 on: 14/03/2009 13:45:33 »
I don't think I have ever seen an in-detail description of just exactly how this expansion of space is taking place. Space is expanding, but galaxies are not? The concept seems to still be evolving. The scenario is a little different each time I get a description of it.
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
Can we measure 'expansion'
« Reply #16 on: 14/03/2009 14:14:40 »
The expansion is happening inside galaxies but the force of gravity is stronger and is holding it in check. At least, that is what the theory says.

Just a thought:

Could that explain why gravity is so weak compared to the other forces? That it is being acted against by (is in opposition to) expansion? If there is this other force trying to push everything apart while gravity is trying to pull it all together, that would surely have the effect of making gravity appear weaker than it really is.
« Last Edit: 14/03/2009 14:20:04 by DoctorBeaver »
 

Offline Vern

  • Neilep Level Member
  • ******
  • Posts: 2072
    • View Profile
    • Photonics
Can we measure 'expansion'
« Reply #17 on: 14/03/2009 14:21:33 »
Okay, that makes sense; I had heard that before. I didn't know if we had settled on that concept. If we know that much, we must also know how great is this force, and it must then be a fifth force of nature. Maybe it is mediated by an expansiton, or maybe even a Chronaton. Unification theorists should love that :)
« Last Edit: 14/03/2009 14:23:50 by Vern »
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
Can we measure 'expansion'
« Reply #18 on: 14/03/2009 14:24:14 »
Okay, that makes sense;

I made sense? Me? Made sense?  [:0]
 

Offline Vern

  • Neilep Level Member
  • ******
  • Posts: 2072
    • View Profile
    • Photonics
Can we measure 'expansion'
« Reply #19 on: 14/03/2009 14:39:16 »
I keep going back to the question; why are we forced into this weird concept of expanding space? It is because we see that starlight is Doppler shifted toward the red and that the amount of this red shift is consistently greater the farther the light source. But now, we're saying it is not Doppler shifted at all. Light is being stretched out by expanding space.

I keep thinking that surely there will soon be some reasonable explanation that will forgo all this weirdness.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11999
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Can we measure 'expansion'
« Reply #20 on: 14/03/2009 15:08:07 »
DB you are correct in that it's space that is expanding, but that must 'push' on those galaxies too.

But that implies the galaxies are moving due to the expansion and they aren't. Within their bit of space they are stationary apart from their movement due to gravity.


I don't agree DB, the galaxies are moving due to the expansion, relative any frame of reference. It may well be so (in fact, it must be so:) that they don't experience any expansion themselves, but just like floating islands in the ocean are moving so are those galaxies moving in spacetime.
Movement, is after all, when all is said and done, the distance between two frames of reference growing as seen in time, at least in our spacetime. Inflation was outside what we call spacetime today as I see it, expansion takes place inside it. ::))
« Last Edit: 14/03/2009 15:27:13 by yor_on »
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
Can we measure 'expansion'
« Reply #21 on: 14/03/2009 15:49:58 »
Quote
but just like floating islands in the ocean are moving so are those galaxies moving in spacetime.

No, it's very different. The ocean isn't expanding. It is currents (water & wind) that push floating objects around. These are no such ccurrents in space.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11999
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Can we measure 'expansion'
« Reply #22 on: 14/03/2009 16:09:28 »
Yes, it was only a analogue:) and you could say that there are forces of 'density' acting on the island but not on the galaxies, that is if we presume space to be a 'perfect vacuum'. But I still say that the galaxies are moving (accelerating in fact) relative us and that this should, in our spacetime at least, imply some 'force' being involved. What this idea say is that space is suddenly 'isolated' into islands of galaxies with all the 'normal' physics working. But outside those you have 'space' that somehow 'grows/expands', similar to how a underwater spring can 'push' objects aside as it sprouts under water. Either space has distance as a quality, and then the distance between objects are growing in space, or if distance is a outdated description I think I will leave it to you to define what a 'space' between two points represent, if not a distance.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11999
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Can we measure 'expansion'
« Reply #23 on: 14/03/2009 17:12:03 »
It's a strange 'force' if so, strong enough to push whole galaxies, but so weak that it can't do anything inside our solarsystem.
 

Offline DoctorBeaver

  • Naked Science Forum GOD!
  • *******
  • Posts: 12656
  • Thanked: 3 times
  • A stitch in time would have confused Einstein.
    • View Profile
Can we measure 'expansion'
« Reply #24 on: 14/03/2009 18:38:46 »
Quote
But outside those you have 'space' that somehow 'grows/expands', similar to how a underwater spring can 'push' objects aside as it sprouts under water

The space inside galaxies would expand if gravity were not holding it in check. The force is acting everywhere but in some places is more noticeable as there is less gravity.
 

The Naked Scientists Forum

Can we measure 'expansion'
« Reply #24 on: 14/03/2009 18:38:46 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums