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Author Topic:   Question About the Universe
Dogmafood
Member (Idle past 575 days)
Posts: 1815
From: Ontario Canada
Joined: 08-04-2010


Message 42 of 373 (694953)
03-31-2013 10:56 AM


Madly off in all directions
The expansion of space is detectable by the red shifting of light. This is expansion along the vector that the light is travelling. Can we see the expansion of space orthogonal to that vector?
To put it another way, would 2 streams of photons that are parallel at their sources remain parallel across big space?

Replies to this message:
 Message 44 by Stile, posted 04-01-2013 9:13 AM Dogmafood has replied

  
Dogmafood
Member (Idle past 575 days)
Posts: 1815
From: Ontario Canada
Joined: 08-04-2010


Message 46 of 373 (695040)
04-02-2013 6:54 AM
Reply to: Message 44 by Stile
04-01-2013 9:13 AM


Re: Madly off in all directions
Hey Stile, cheers.
I suppose that there is some basic aspect of optics that I am not remembering but I was wondering why distant objects do not appear much larger than they are if the light from them is spreading out in all directions. Larger and all fuzzy.
Either that or why we don't see distant stars getting farther apart from each other in directions other than directly down the line of sight. Or do we see that?
Edit; If there are 2 stars that are 100Mpc apart from each other today. Tomorrow they will be 10.6 million km farther apart. 100 million km in 10 days. If our line of sight is perpendicular to their separation, why do we not see that distance increasing? Or do we?
Edited by Prototypical, : No reason given.

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Replies to this message:
 Message 47 by Stile, posted 04-02-2013 9:21 AM Dogmafood has replied
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Dogmafood
Member (Idle past 575 days)
Posts: 1815
From: Ontario Canada
Joined: 08-04-2010


Message 51 of 373 (695255)
04-04-2013 4:39 AM
Reply to: Message 47 by Stile
04-02-2013 9:21 AM


Re: To see or not to see
Cheers again for all that typing you did there. That's like the mother of all answers!
Here's an example:
Let's say I'm on a mountain top with a flashlight.
I think that I have a grasp on diffusion and dimness. I guess what I am trying to understand is if my intuitive concept of expansion is the same as the way the universe is expanding.
I was trying to eliminate the 'normal' diffusion of light out of the question by considering streams of single photons on parallel vectors. Would those 2 streams experience diffusion caused by the expansion of space?
Or if you projected a stream of single photons at a receiver would the expansion of space require that you adjust the beam in order to maintain the line of sight?

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 Message 53 by Stile, posted 04-04-2013 9:24 AM Dogmafood has replied

  
Dogmafood
Member (Idle past 575 days)
Posts: 1815
From: Ontario Canada
Joined: 08-04-2010


Message 52 of 373 (695256)
04-04-2013 4:40 AM
Reply to: Message 50 by Dr Adequate
04-02-2013 10:29 AM


Re: Madly off in all directions
0.00000000000117 degrees....You couldn't see that, could you?
No I suppose not.
If I imagine an equilateral triangle consisting of my eye and any two stars. As the universe expands will that triangle remain equilateral?

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Dogmafood
Member (Idle past 575 days)
Posts: 1815
From: Ontario Canada
Joined: 08-04-2010


Message 56 of 373 (695601)
04-08-2013 7:53 AM
Reply to: Message 53 by Stile
04-04-2013 9:24 AM


Re: Expansion of Space, not Everything
Only space is expanding, everywhere and in every direction.
Think of it like a force.
I was under the impression that the increasing distance between galaxies is not the same as the increasing distance between me and a ball that I have thrown. Galaxies are not moving through space but rather new space is being created(?) or introduced between them.
Experience tells me that you need some kind of pressure to squeeze that new space in between those galaxies given that space is actually a thing. So if dark energy is responsible for the expansion of space and the increasing distance between galaxies, am I right to think of it behaving in the same way that forces work locally? Dark energy has to overcome the mass of all the galaxies in order to move them? In order to do that it must be pushing 'off of' something else.
edit;
The direction of travel of the two streams would always be parallel at any specific point in time you cared to look at them.
However, the distance between the two streams would, in fact, increase due to the expansion of space.
And it would increase equally down the entire length of the streams?
Edited by Prototypical, : No reason given.

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 Message 58 by Stile, posted 04-08-2013 10:37 AM Dogmafood has replied

  
Dogmafood
Member (Idle past 575 days)
Posts: 1815
From: Ontario Canada
Joined: 08-04-2010


Message 57 of 373 (695606)
04-08-2013 8:06 AM
Reply to: Message 54 by NoNukes
04-04-2013 10:34 AM


Re: Madly off in all directions
I understand that what you are really mean to is whether the expansion of space is isotropic (uniform at all points and 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?

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Dogmafood
Member (Idle past 575 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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Dogmafood
Member (Idle past 575 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:
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Dogmafood
Member (Idle past 575 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.

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

  
Dogmafood
Member (Idle past 575 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.

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Dogmafood
Member (Idle past 575 days)
Posts: 1815
From: Ontario Canada
Joined: 08-04-2010


Message 82 of 373 (697487)
04-26-2013 8:22 AM
Reply to: Message 81 by Son Goku
04-26-2013 4:54 AM


Re: Mass of spacetime.
Of course the spacetime does not actually have mass, you can just infer how much mass was involved in shaping it.
Don't you need mass/energy in order to have shape?

This message is a reply to:
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Dogmafood
Member (Idle past 575 days)
Posts: 1815
From: Ontario Canada
Joined: 08-04-2010


(3)
Message 136 of 373 (740103)
11-01-2014 9:11 AM
Reply to: Message 135 by New Cat's Eye
11-01-2014 9:07 AM


If science isn't uncovering truth, then why is it working so well?
Because reality is part of the conspiracy.

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