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#11560 - 07/30/06 03:16 AM Expanding Universe???
Pragmatist Offline
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Registered: 03/10/06
Posts: 84
Loc: N.W. U.S.
Something DA posted 'gave me to think.`
Given that the universe is curved, why do we assume
that time remains straight?
Consider a curved space, a sphere, (simplest case because doing this with a hyperbola would give me a headache), with time everywhere normal to space.
The observed redshift becomes a consequence of viewing time 'at a slant`.
Doesn't Hubbels Constant become a tangent function of distance for this configuration?
Could something like this explain the accelleration
recently observed in the expansion of space?
Before you tromp on this with both feet Al, remember where it was posted.

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#11561 - 07/30/06 04:49 AM Re: Expanding Universe???
dehammer Offline
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Registered: 03/23/06
Posts: 1089
As i understand it, space curves at gravity points. since there is not much gravity in deep space, i dont now how much space would curve there. where the light goes thought other galaxies, it looks to me like it could slant it. In intergalaxtic space, i dont see how it could. But then again, my lack of a degree in physics could be showing.
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#11562 - 07/30/06 07:50 PM Re: Expanding Universe???
DA Morgan Offline
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Registered: 10/17/04
Posts: 4136
Loc: Seattle, WA
Pragmatist ... The universe is not curved ... its geometry is flat ... at least to the best of our ability to measure it.

Amazingly enough dehammer got this one correct. It appears that curvature only exists where there is mass. But slant? Off into nonsense yet again. The word slant has no valid context.
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#11563 - 07/30/06 08:17 PM Re: Expanding Universe???
dehammer Offline
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Registered: 03/23/06
Posts: 1089
not nonsense, just open mindedness. a galaxy has a certain gravity field to it, which could effect the curvature of space in its vicinity. since to my knowledge no one else has suggested this theory, there is no name for the situation IF it exist. All the photos I've seen before were taken off galaxies on the far side of other galaxies. Could the mass of the galaxies in between have some effect on the timing of the light getting to earth? Personally, i don't see why it cant. I certainly will not say it cant happen. you would have to ask someone who had a lot more knowledge in the subject than me. If you have some way of asking this question to one of them, id love to hear the answer.
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the more man learns, the more he realises, he really does not know anything.

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#11564 - 07/30/06 11:02 PM Re: Expanding Universe???
Pragmatist Offline
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Registered: 03/10/06
Posts: 84
Loc: N.W. U.S.
When I spoke of curvature, I was talking of the overall shape of space,
Spherical if the universe is closed, (due to collapse,
Flat if steady state, (due to expand to a standstill),
Hyperbolic if open, (due to continue to expand).

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#11565 - 07/30/06 11:36 PM Re: Expanding Universe???
Pragmatist Offline
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Registered: 03/10/06
Posts: 84
Loc: N.W. U.S.
Cont'd.:(Sorry, wrong button)...
These are still 'gravity` shapes, but are presumed to be the result of the gravity of the entire mass of the universe.
Yes the shapes referred to are 'dimpled` by local
gravity, and are not true sphere, plane, or hyperbola, but refer to the 'open` 'flat` or 'closed` condition.
My understanding of current observations is that they indicate not only a hyerbolic, (open), configuration, but an accellerating expansion based on discrepancies between ranges measured by Hubbels red shift and those measured by supernova brightness. (The Big Rip).
If something like this is happening, the brightness ranges would be less, (and truer).
The attraction of this odd little notion is that the relativistic explanation of gravity is wrapped up with time
so that it looks, from a certain viewpoint,
like a trade off of time rate for a force vector.
If time 'slows` with distance, then gravity may
as well.
Suddenly the extra mass required to keep the galaxies stable may not be required.
The hard to explain accelleration of expansion
may not exist.
At any rate the concept was interresting enough
that I posted it here.

I wish I had the math to explore it, but I don't.

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#11566 - 07/31/06 01:30 AM Re: Expanding Universe???
DA Morgan Offline
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Registered: 10/17/04
Posts: 4136
Loc: Seattle, WA
Pragmatist wrote:
"Flat if steady state, (due to expand to a standstill)"

An easily understandable mistake but an error non-the-less. Flat does not refer to steady state. One could have a steady-state and be any shape. It does not relate to geometry.

Geometry, in essence, is as follows:
I shoot two laser beams 1 meter apart out into space. Do they diverge or converge or remain parallel? If they remain parallel the geometry is flat. And that is our universe as we understand it.

Hope this helps.
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#11567 - 08/02/06 04:57 AM Re: Expanding Universe???
Pragmatist Offline
Member

Registered: 03/10/06
Posts: 84
Loc: N.W. U.S.
Thanks for the correction D.A.
As to the measurement of 'flatness`, what is
our yardstick? Given the size of the universe,
and the supposition that the C+ inflation phase
after the Big Bang placed a lot of it beyond our
event horizon, (proper term??), we would require
a very long one. My understanding is that we only
mananged to measure the rather large curvature around the sun due to a near occultation of another
star by the sun in 1928(?), and it required astronomical telescopes to do that much.
As to my fanciful idea, I just can across an article
describing lensing by dark matter so the attraction
of removing same on the Occams Razor principle is
vastly diminished as it now agrees with observation.
In the immortal words of S.N.L.s Church Lady:
"OK, Never mind."

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#11568 - 08/02/06 05:01 PM Re: Expanding Universe???
DA Morgan Offline
Megastar

Registered: 10/17/04
Posts: 4136
Loc: Seattle, WA
Pragmatist asks:
"what is our yardstick?"

This may help:
http://news.bbc.co.uk/2/hi/science/nature/727073.stm

Note the quote:
"To astronomers, flat means that the usual rules of geometry are observed - light not being bent by gravity travels in straight lines, not curves."

A bit more technically:
http://en.wikipedia.org/wiki/Shape_of_the_universe

And more technically still:
http://www.astro.ucla.edu/~wright/cosmo_03.htm
-- be sure to click the links

You should find the answer you are looking for.
_________________________
DA Morgan

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#11569 - 08/02/06 06:06 PM Re: Expanding Universe???
Blacknad Offline
Superstar

Registered: 10/05/05
Posts: 901
Loc: Coventry, England
Excellent links Dan. Thanks.

Blacknad.

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#11570 - 08/02/06 06:07 PM Re: Expanding Universe???
Blacknad Offline
Superstar

Registered: 10/05/05
Posts: 901
Loc: Coventry, England
Whoops. Got a bit too click happy when it didn't respond quickly enough.

Blacknad.

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#11571 - 08/02/06 07:41 PM Re: Expanding Universe???
dehammer Offline
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Registered: 03/23/06
Posts: 1089
very interesting, da.
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the more man learns, the more he realises, he really does not know anything.

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#11572 - 08/03/06 02:29 AM Re: Expanding Universe???
Pragmatist Offline
Member

Registered: 03/10/06
Posts: 84
Loc: N.W. U.S.
Thanks DA, - Off to do some homework.

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