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Is lightspeed really a limit?

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#26 Pess

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Posted 26 November 2012 - 12:19 PM

The interest compounds as you go.


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#27 scopethis

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Posted 26 November 2012 - 01:56 PM

we need to find the anti-light/photon...

#28 Carl Coker

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Posted 27 November 2012 - 04:47 PM

Photons are their own antiparticles, actually.

#29 deSitter

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Posted 28 November 2012 - 09:16 AM

Photons are their own antiparticles, actually.


While this is technically true, it doesn't really mean anything. It's sort of like saying 1 is a not a prime number because certain theorems depend on its not being prime. I've always suspected a deeper understanding of antimatter would lift this ambiguity. What is really meant is that you cannot distinguish matter from antimatter purely by examining the radiation field at a distance. An anti-star would look the same as a star (other than its envelope of annihilation with any ambient matter).

-drl

#30 Starman1

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Posted 15 December 2012 - 12:17 AM

C is only the "limit" of speed that two particles of matter could move away from each other in a non-expanding frame.
The frame itself has no such limit. Two particles at rest relative to the "frame" could move away from each other faster than light and relativity would not be violated.
Indeed, the Universe is expanding fast enough that some parts of it will never be visible.
But, as a matter of energy and inertia, two particles could never be accelerated to C relative to each other because it would take an infinity of energy to do so and that much energy doesn't exist in the universe.

#31 scopethis

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Posted 15 December 2012 - 01:15 PM

but the Universe is expanding faster than light...right?

#32 Starman1

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Posted 15 December 2012 - 04:30 PM

Points in the universe's frame far enough apart could be expanding away from each other faster than light. That still would not be a violation of relativity but it would mean that some of the universe is "beyond the horizon" and, hence, unknowable. IF universal expansion is accelerating, and the jury is still out on that with recent findings of some new types of Supernovae, then a gradually increasing percentage of the universe will be beyond the horizon until each proton is in its own universe, then quark, then.........................

#33 mistyridge

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Posted 16 December 2012 - 02:52 AM

If you and your ship had no mass in this universe you could go as fast as you want..."C" would be meaningless. Without mass you would not have to worry about running into solid matter stars planets etc, you and your ship would pass right through them just like a nutrino.

#34 Jarad

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Posted 16 December 2012 - 08:24 AM

Not necessarily. A photon has no rest mass, and travels at exactly C. But it does interact with matter, so if it runs into something it can be absorbed. Of course, in it's frame of reference, no time passes so it sees it as teleporting from the point of emission to the point of absorption.

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#35 mistyridge

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Posted 16 December 2012 - 01:52 PM

Well, we will just have to figure a way to warp into another universe where C is not the speed limit. :grin:

#36 llanitedave

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Posted 16 December 2012 - 10:44 PM

I did that some years ago. Problem is, I haven't found a way to unwarp.

#37 Pess

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Posted 17 December 2012 - 12:42 PM

If you and your ship had no mass in this universe you could go as fast as you want..."C" would be meaningless. Without mass you would not have to worry about running into solid matter stars planets etc, you and your ship would pass right through them just like a nutrino.


If you & your ship had no mass, than by definition you would be mere energy and you would shoot off at exactly 'c'.

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#38 Pess

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Posted 17 December 2012 - 12:47 PM

Think of the expanding universe as like two sentient raisins in a loaf of rising bread. One of the raisin is lovesick and wants to get to the location of the other raisin within the bread.

The problem is that the lovesick raisin can only travel through the bread at 1mph but the bread itself is expanding in all directions at 2mph.

From this prospective the lovesick raisin can never reach the object of his raisin-lust and, in fact, over time gets further and further away from his target despite not loafing along the way.


Pesse (Loafing Ha-Ha! Seriously I sometimes crack myself up!) Mist

#39 dyslexic nam

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Posted 17 December 2012 - 04:03 PM

I'm probably not being original, But at what point would it be impossible to accelerate an object any more in reality( not on paper)


Never. You can keep accellerating and getting closer to C.

In practical terms, from the point of view of a stationary observer, there isn't much point as you get past 90% or so. From the point of view of earth, a probe launched a 0.9C toward a star 100 light years away will arrive in 111 years, one moving at 0.99C will get there in 101 years, and one moving at 0.99999C will get there in just over 100 years (not much difference between 101 and 100).

But from the point of view of someone riding the probe, it's a huge difference. Most of the additional energy put in to accelleration ends up increasing your time dilation. On the ship, a 100 light year trip at 0.9C takes 48.5 years. At 0.99C it takes 14.25 years, and at 0.99999C it takes just over 5 months.

Costs a LOT of energy, though. With the best current technology, we'd be lucky to achieve 0.01C.

Jarad


I know when I am way (waaaaay) out of my depth, but I found this quite interesting. Thanks.

#40 scopethis

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Posted 17 December 2012 - 05:03 PM

where is the belly button of the Universe?

#41 Pess

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Posted 17 December 2012 - 05:10 PM

where is the belly button of the Universe?


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

#42 Mister T

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Posted 17 December 2012 - 05:33 PM

Behind the lint

#43 FirstSight

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Posted 18 December 2012 - 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?

#44 Jarad

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Posted 18 December 2012 - 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

#45 Pess

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Posted 18 December 2012 - 06:01 PM

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

#46 scopethis

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Posted 21 December 2012 - 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?

#47 Starman1

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Posted 21 December 2012 - 06:03 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?

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.

#48 Mister T

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Posted 21 December 2012 - 09:22 PM

the more important question is:

Why aren't closing games for the Red sox?

#49 CounterWeight

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Posted 06 January 2013 - 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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