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Pess
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Reged: 09/12/07

Loc: Toledo, Ohio
Re: Is lightspeed really a limit? new [Re: scopethis]
      #5576060 - 12/17/12 05:10 PM

Quote:

where is the belly button of the Universe?




Pesse (Dunno, but it is pretty obvious the big bang left an 'Outie'.) Mist


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Mister T
Pooh-Bah


Reged: 02/01/08

Loc: Upstate NY
Re: Is lightspeed really a limit? new [Re: scopethis]
      #5576094 - 12/17/12 05:33 PM

Behind the lint

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FirstSightModerator
Duke of Deneb
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Reged: 12/26/05

Loc: Raleigh, NC
Re: Is lightspeed really a limit? new [Re: scopethis]
      #5577075 - 12/18/12 10:35 AM

The part of the two-raisins-in-a-loaf analogy for the universe's expansion which seems inadequate (incomplete) is this:

IF one raisin is moving toward another at 1mph but the overall expansion rate of the loaf is 2mph
THEN why isn't the raisin ITSELF expanding at the same rate as the overall loaf, thus offsetting any spatial effect of the loaf's overall expansion?

Removing the analogy, aren't matter and energy an integral part of the space itself that's expanding, i.e. the matter along with it? If not, why not?

Edited by FirstSight (12/18/12 10:37 AM)


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Jarad
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Reged: 04/28/03

Loc: Atlanta, GA
Re: Is lightspeed really a limit? new [Re: FirstSight]
      #5577089 - 12/18/12 10:42 AM

Scale.

The universe is expanding, but in order for the expansion to be significant two objects have to be many millions of light years apart. On smaller scales, the expansion is so tiny and slow that it gets overwhelmed by local forces like gravity and electro-magnetism.

A while back I think we ran through the calculation that at the orbit of Pluto, our solar system expands by a fraction of a millimeter per year. But the sun's gravity is more than capable of pulling Pluto back in by that much per year, so Pluto stays put.

But between us and another galaxy a few billion light years away, the expansion increases to a measureable fraction of C, and gravity fades by distance squared so it has dropped to insignificance. In that case, the expansion carries the galaxies away from each other.

Jarad


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Pess
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Reged: 09/12/07

Loc: Toledo, Ohio
Re: Is lightspeed really a limit? new [Re: Jarad]
      #5577662 - 12/18/12 06:01 PM

Quote:

Scale.

The universe is expanding, but in order for the expansion to be significant two objects have to be many millions of light years apart. On smaller scales, the expansion is so tiny and slow that it gets overwhelmed by local forces like gravity and electro-magnetism.

A while back I think we ran through the calculation that at the orbit of Pluto, our solar system expands by a fraction of a millimeter per year. But the sun's gravity is more than capable of pulling Pluto back in by that much per year, so Pluto stays put.

But between us and another galaxy a few billion light years away, the expansion increases to a measureable fraction of C, and gravity fades by distance squared so it has dropped to insignificance. In that case, the expansion carries the galaxies away from each other.

Jarad




I was trying to think of a good analgy for this but I can't so I came up with a real *BLEEP* one:

1) Put ten guys in a line.
2) Now place a deflated balloon between each guy and the guy next to him so you got guy-balloon-guy-bslloon-guy-balloon etc
3) Put an all-you can-eat buffet in front of each guy.

Now say "go!" while inflating all the balloons simultaneously..note that all the men get fatter stuffing their faces.

You will still note that the men on each end get farther apart from each other faster than any two men closer to each other.

Pesse (I want an award for worst analgy on CN. And, yeah, I got into the Scotch again...) Mist


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scopethis
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Re: Is lightspeed really a limit? new [Re: Pess]
      #5582817 - 12/21/12 04:50 PM

I am on a train's flatcar being pulled at 100mph..if I throw a baseball at 100mph in the direction the train is moving, will the baseball go anywhere or fall straight down?

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Starman1
Vendor (EyepiecesEtc.com)
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Reged: 06/24/03

Loc: Los Angeles
Re: Is lightspeed really a limit? new [Re: scopethis]
      #5582951 - 12/21/12 06:03 PM

Quote:

I am on a train's flatcar being pulled at 100mph..if I throw a baseball at 100mph in the direction the train is moving, will the baseball go anywhere or fall straight down?



In that analogy, the baseball in your hand already has a forward speed of 100mph. When you throw it forward, it will travel at 100mph relative to the train, or 200mph relative to a fixed point on the ground that the train is passing.

However, you cannot extrapolate such additive speed properties when you approach the speed of light. You see, the additional energy required to accelerate something grows exponentially as you approach the speed of light. If the train were traveling 99.99999999999999999% the speed of light relative to the fixed ground outside the train, and you fired a high velocity bullet forward on the train, the bullet would not be traveling faster than the speed of light relative to the ground outside the train. The reason is that it would be traveling with the energy required to travel 99.99999999999999999% the speed of light plus whatever speed the additional energy of the gun imparted, which, at that speed, wouldn't even be enough to add a 1 to the end of the 9's. That's why two objects cannot recede from one another relative to the fixed frame of the universe at light speed--because it would require an infinite amount of energy to accelerate two protons to light speed if traveling away from one another.

Another way to look at it is that the inertia resisting acceleration heads to infinity as the object nears light speed, i.e. its mass increases exponentially as you attempt to accelerate it to light speed until pushing a proton to really close to light speed would be like accelerating a planet, then a star, then a galaxy, then a cluster of galaxies and you still would not be at light speed. You could consume all the energy in the Universe and STILL not accelerate 1 proton to light speed.

Fortunately for us, we live and operate at really slow speeds, where newtonian physics works just fine. But, when we deal with sub atomic particles in particle accelerators, we do deal with relativistic speeds. And the amount of energy used to accelerate a handful of protons would power a small city.


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Mister T
Pooh-Bah


Reged: 02/01/08

Loc: Upstate NY
Re: Is lightspeed really a limit? new [Re: scopethis]
      #5583219 - 12/21/12 09:22 PM

the more important question is:

Why aren't closing games for the Red sox?


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CounterWeight
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Reged: 10/05/08

Loc: Palo alto, CA.
Re: Is lightspeed really a limit? [Re: Mister T]
      #5608172 - 01/06/13 11:49 AM

It's interesting to consider within say the visible light spectrum looking at the distance wavefronts travel 'per cycle' partitioned, red is a faster wavefront velocity component |covers more distance| than blue 'per cycle'.

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