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Author Topic:   Question About the Universe
Dr Adequate
Member (Idle past 275 days)
Posts: 16113
Joined: 07-20-2006


Message 61 of 373 (695646)
04-08-2013 12:50 PM
Reply to: Message 57 by Dogmafood
04-08-2013 8:06 AM


Re: Madly off in all directions
Sort of I guess but I was wondering if the expansion has any effect on light in directions other than down it's direction of travel. It stretches the light but does it bend it in any way?
Kind of, yes. And no. But if two beams of light start off parallel in (for the sake of simplicity) an otherwise empty expanding universe, then the distance between them will increase. In the geometry of GR, that doesn't stop them from being parallel ...
NoNUkes will correct me if I'm wrong.

This message is a reply to:
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NoNukes
Inactive Member


Message 62 of 373 (695664)
04-08-2013 3:36 PM
Reply to: Message 60 by Stile
04-08-2013 12:46 PM


Re: Expansion of Space, not Everything
I do not know if "the effect of the expansion of space" is considered "a force" or not. Can it be measured in Newtons? Because of that... I don't know if I can talk about it as "the force of the expansion of space."
I think the best way of looking at expansion is as the creation of more space in the separation between the galaxies. But it is a mistake to picture galaxies as somehow anchored in space and being carried along at some velocity with the expansion.
Or said another way, the increase in separation due to the expansion of space is not a movement through space, while the effects of gravity and other motion through space (and remember we don't need a force to justify motion, only acceleration motion) are a completely different phenomenon and is a movement through space.

Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)
I would say here something that was heard from an ecclesiastic of the most eminent degree; ‘That the intention of the Holy Ghost is to teach us how one goes to heaven, not how the heaven goes.’ Galileo Galilei 1615.
If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass

This message is a reply to:
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NoNukes
Inactive Member


Message 63 of 373 (695666)
04-08-2013 3:38 PM
Reply to: Message 61 by Dr Adequate
04-08-2013 12:50 PM


Re: Madly off in all directions
NoNUkes will correct me if I'm wrong.
Sounds right to me.

Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)
I would say here something that was heard from an ecclesiastic of the most eminent degree; ‘That the intention of the Holy Ghost is to teach us how one goes to heaven, not how the heaven goes.’ Galileo Galilei 1615.
If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass

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 Message 61 by Dr Adequate, posted 04-08-2013 12:50 PM Dr Adequate has not replied

  
Dogmafood
Member (Idle past 339 days)
Posts: 1815
From: Ontario Canada
Joined: 08-04-2010


Message 64 of 373 (695667)
04-08-2013 3:39 PM
Reply to: Message 59 by NoNukes
04-08-2013 12:32 PM


Re: Expansion of Space, not Everything
For at least the third time... with respect to galaxies, the answer is that both types of changes in separation are happening.
Sorry, it was clear to me what I was talking about but yes both types of motion are happening. I was trying to isolate the one type that I don't see everyday.

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NoNukes
Inactive Member


Message 65 of 373 (695671)
04-08-2013 3:48 PM
Reply to: Message 64 by Dogmafood
04-08-2013 3:39 PM


Re: Expansion of Space, not Everything
I was trying to isolate the one type that I don't see everyday.
A reasonable thing to do. I'm sure I over-reacted. It's pretty easy to tell the difference between posts from someone trying to learn something and the hubris laden posts of the righteously ignorant. Your posts are clearly not of the latter group.
Edited by NoNukes, : No reason given.

Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)
I would say here something that was heard from an ecclesiastic of the most eminent degree; ‘That the intention of the Holy Ghost is to teach us how one goes to heaven, not how the heaven goes.’ Galileo Galilei 1615.
If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass

This message is a reply to:
 Message 64 by Dogmafood, posted 04-08-2013 3:39 PM Dogmafood has seen this message but not replied

  
Dogmafood
Member (Idle past 339 days)
Posts: 1815
From: Ontario Canada
Joined: 08-04-2010


Message 66 of 373 (695676)
04-08-2013 4:59 PM
Reply to: Message 58 by Stile
04-08-2013 10:37 AM


Re: Expansion of Space, not Everything
That is, if two things are linked with other forces (gravity, electromagnetic, or any of the others...) it is possible that the forces that link them together will be greater than the "force" from the expansion of space. If so, then the objects will not move apart.
Sure, I get that part. The part that my brain seems unable to incorporate is the part where two discrete objects can become farther apart and yet neither one of them is moving. In fact it really surprises me how readily everyone else seems to accept this. This leads me to conclude that I have missed something. Probably several things.

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Replies to this message:
 Message 67 by Son Goku, posted 04-08-2013 5:19 PM Dogmafood has replied
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Son Goku
Inactive Member


Message 67 of 373 (695679)
04-08-2013 5:19 PM
Reply to: Message 66 by Dogmafood
04-08-2013 4:59 PM


Re: Expansion of Space, not Everything
A simple example might help.
Take a universe with only ten points, labelled by the integers from 1 to 10. This universe also has only two objects, labelled A and B. A sits at location 2 and B sits at location 8. The distance between A and B is obviously six points.
Distance traveled, for objects in this universe, is just the number of points they've past through. How far apart the points are in whatever fictional background you choose to visualize them in, is irrelevant as that background has no physical reality in this model.
Now simply add ten more points into the universe, the half-integers let's say (i.e. 0.5, 1.5, e.t.c.). There are now twelve points between A and B, so they are further apart, but they haven't moved, they're still located at points 2 and 8.
It's simply that more space has been created between them. It's the same with our universe.

This message is a reply to:
 Message 66 by Dogmafood, posted 04-08-2013 4:59 PM Dogmafood has replied

Replies to this message:
 Message 69 by Dogmafood, posted 04-08-2013 10:44 PM Son Goku has replied

  
AZPaul3
Member
Posts: 8493
From: Phoenix
Joined: 11-06-2006
Member Rating: 4.7


Message 68 of 373 (695681)
04-08-2013 5:28 PM
Reply to: Message 66 by Dogmafood
04-08-2013 4:59 PM


Re: Expansion of Space, not Everything
The part that my brain seems unable to incorporate is the part where two discrete objects can become farther apart and yet neither one of them is moving
But your brain is working just fine. The two objects are moving, in relation to each other.
Think of a mid-ocean ridge. Up-welling from the ridge, spreading both left and right, is new ocean floor. So you have a shell on either side of the ridge. The shells are not moving in relation to the part of the ocean floor, the dirt, mud and muck, they are on but, as the up-welling continues and new ocean floor is made the two shells get further apart. A 2-d example. In space-time this happens in 3-d, in every direction at once, a mid-ocean ridge in every speck of space welling up new space in all directions.

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Dogmafood
Member (Idle past 339 days)
Posts: 1815
From: Ontario Canada
Joined: 08-04-2010


Message 69 of 373 (695714)
04-08-2013 10:44 PM
Reply to: Message 67 by Son Goku
04-08-2013 5:19 PM


Re: Expansion of Space, not Everything
A simple example might help.
Hope springs eternal.
I seem to have a grasp of the idea that galaxies are receding from us at a velocity that is proportionate to their distance from us.
I would use the analogy of a strip of pleated fabric with a galaxy at each peak. We are in the middle of the strip. If we pull either end of the fabric then all of the peaks move apart by the same amount but in relation to us the last peak at either end has moved much further than the peaks closest to us. In the case of the universe the force is coming from in between each peak in the form of new space. (Incidentally, it is while trying to image this same thing happening along every possible vector simultaneously that my brain seizes.)
Doesn't this mean that the force that is driving the closest two galaxies away from us has to make some contribution to all of the other increasing gaps? That the expansion of space that is happening between us and the nearest receding galaxy is having an impact on the galaxy that is furthest away? I want to ask you if space is non compressible but it seems like such a nonsense question.
I appreciate that the expansion of the universe is a fairly unique thing. Is it so unique that it defies things like Newton's laws of motion. It is as if the expansion of space only obeys some of the rules in that it is having an effect without doing the work.

This message is a reply to:
 Message 67 by Son Goku, posted 04-08-2013 5:19 PM Son Goku has replied

Replies to this message:
 Message 70 by Son Goku, posted 04-16-2013 5:02 PM Dogmafood has replied

  
Son Goku
Inactive Member


Message 70 of 373 (696531)
04-16-2013 5:02 PM
Reply to: Message 69 by Dogmafood
04-08-2013 10:44 PM


Re: Expansion of Space, not Everything
Doesn't this mean that the force that is driving the closest two galaxies away from us has to make some contribution to all of the other increasing gaps? That the expansion of space that is happening between us and the nearest receding galaxy is having an impact on the galaxy that is furthest away?
In truth there is no force. New space is simply being created. Every second, for each cubic meter, about 10 cubic attometers are created and hence there is suddenly more distance/space between each object.
So just looking a one direction, rather than a volume, for every meter about two attometers are created.
The distance between here and the Andromeda galaxy is about 2.54 Mega light years, add two new attometers for every meter along that distance and you get an increase of about 2 centimeters per second (actually 1.8 centimeters).
Now, even though the reality is that 2 centimeters are being created, you can think of it like the Andromeda Galaxy moving away at a rate of 0.02 m/s. That's nowhere near enough to overcome the fact that it is approaching the Milky Way at ~120 km/s.

This message is a reply to:
 Message 69 by Dogmafood, posted 04-08-2013 10:44 PM Dogmafood has replied

Replies to this message:
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Dogmafood
Member (Idle past 339 days)
Posts: 1815
From: Ontario Canada
Joined: 08-04-2010


(1)
Message 71 of 373 (696642)
04-17-2013 12:48 PM
Reply to: Message 70 by Son Goku
04-16-2013 5:02 PM


Re: Expansion of Space, not Everything
In truth there is no force.
This universe is absofuckinglutely bizarre.

This message is a reply to:
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NoNukes
Inactive Member


Message 72 of 373 (696644)
04-17-2013 12:57 PM
Reply to: Message 71 by Dogmafood
04-17-2013 12:48 PM


Re: Expansion of Space, not Everything
bizarre
Yes. Bizarre such that when you find a concept difficult to picture, that can be an indication that your near to grasping it if you haven't already. People who think that they can actually mentally picture three dimensional space expanding but not expanding into anything are mistaken.

Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)
I would say here something that was heard from an ecclesiastic of the most eminent degree; ‘That the intention of the Holy Ghost is to teach us how one goes to heaven, not how the heaven goes.’ Galileo Galilei 1615.
If there is no struggle, there is no progress. Those who profess to favor freedom, and deprecate agitation, are men who want crops without plowing up the ground, they want rain without thunder and lightning. Frederick Douglass

This message is a reply to:
 Message 71 by Dogmafood, posted 04-17-2013 12:48 PM Dogmafood has seen this message but not replied

  
Son Goku
Inactive Member


(1)
Message 73 of 373 (696662)
04-17-2013 3:13 PM
Reply to: Message 71 by Dogmafood
04-17-2013 12:48 PM


Re: Expansion of Space, not Everything
This universe is absofuckinglutely bizarre.
It certainly is. Although at least with General Relativity you can at least "understand" what it is that you can't picture. In quantum mechanics you don't even have that!

This message is a reply to:
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Replies to this message:
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apoptosis
Junior Member (Idle past 3961 days)
Posts: 4
Joined: 11-30-2011


Message 74 of 373 (696798)
04-18-2013 5:03 PM
Reply to: Message 73 by Son Goku
04-17-2013 3:13 PM


Re: Expansion of Space, not Everything
Does this mean space is being 'created'
If space has an energy density (and mass properties), would this result in net energy and mass being created in the universe?

This message is a reply to:
 Message 73 by Son Goku, posted 04-17-2013 3:13 PM Son Goku has replied

Replies to this message:
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Son Goku
Inactive Member


Message 75 of 373 (696807)
04-18-2013 6:12 PM
Reply to: Message 74 by apoptosis
04-18-2013 5:03 PM


Re: Expansion of Space, not Everything
Does this mean space is being 'created'
Yes, essentially.
If space has an energy density (and mass properties), would this result in net energy and mass being created in the universe?
Space doesn't have an energy density or mass properties.

This message is a reply to:
 Message 74 by apoptosis, posted 04-18-2013 5:03 PM apoptosis has replied

Replies to this message:
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