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sirchz
super member


Reged: 09/21/09

Is lightspeed really a limit?
      #5463630 - 10/10/12 11:07 AM

Relativity and the speed of light is always a popular topic.

This was published in Proceedings of the Royal Society. The lack of any experimentally verifiable predictions is a problem. That aside, I wonder what would motivate the assumption that the product of velocities is limited to c^2? Maybe they just used something that would result in a "nice" mathematical solution?

Quote:

“Einstein started working from information where the relative velocity is zero – what we knew about, such as rest mass, kinetic energy and so on – and then extrapolated what is known in the Newtonian world for velocities lower than c.

“Our thinking was: how do we make use of the essential essence of Einstein’s theory for velocities above c?”

Mathematically, what the mathematicians assumed is that for infinite relative velocity, there is a fixed relationship between the velocities of the two observers: where u is the first observer’s velocity, v is the second, the product of the two velocities is always c2.

“What we have is an equivalent theory [to Special Relativity] that applies for velocities beyond the speed of light. That theory is different from Special Relativity, but it has many of the same characteristics.

And readers with an interest in either physics or maths will be delighted with the vital assumptions: there has to be one, and only one, speed of light; and in all cases, a mathematical singularity occurs at the speed of light.

“If you believe what we’ve done,” Professor Hill said, “there can only be one speed of light in a universe. If there was a second speed of light, our mathematics wouldn’t work.




Quote:

To get from the theory to any practical test is another matter entirely, and Professor Hill freely admits he doesn’t know how that might be achieved.



http://www.theregister.co.uk/2012/10/10/ftl_special_relativity_mathematics/


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deSitter
Still in Old School


Reged: 12/09/04

Re: Is lightspeed really a limit? new [Re: sirchz]
      #5463648 - 10/10/12 11:20 AM

Things are allowed to go faster than C, but only faster. Likewise less than C, but only less. Finally at C, and only at C. Thus, things going faster than C cannot interact with things going less than C, because one might cause the other to change its classification (e.g. annihilation into radiation). This is why tachyons are tacky.

-drl


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Qwickdraw
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Re: Is lightspeed really a limit? new [Re: deSitter]
      #5463770 - 10/10/12 12:29 PM

I have always had a suspicion that C is directly related to the expansion rate of the universe and could be slowly changing. Just a suspicion though.

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Napersky
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Re: Is lightspeed really a limit? new [Re: Qwickdraw]
      #5463990 - 10/10/12 02:57 PM

In Space C is the speed limit. Outside of Space who knows?

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scopethis
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Re: Is lightspeed really a limit? new [Re: Napersky]
      #5468554 - 10/13/12 04:12 PM

traveling faster than light one becomes "infinite mass", somewhat akin to a ghost(??). what would one "see"?

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Mister T
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Reged: 02/01/08

Loc: Upstate NY
Re: Is lightspeed really a limit? new [Re: scopethis]
      #5468907 - 10/13/12 08:45 PM

if you look ahead you see everything.
if you look behind you see nothing


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deSitter
Still in Old School


Reged: 12/09/04

Re: Is lightspeed really a limit? new [Re: scopethis]
      #5469443 - 10/14/12 09:20 AM

Quote:

traveling faster than light one becomes "infinite mass", somewhat akin to a ghost(??). what would one "see"?




Here's what happens at high speed. Three interconnected phenomena occur:

1) Crowding of things into the direction of motion. Things that were behind now appear to be in front. If say you were headed directly toward the Moon, the Moon would appear smaller from crowding. Likewise if you were headed directly away from it, it would appear larger. Near C this becomes extreme, and the entire universe appears to be crowded into a small cone about the direction of motion.

2) Blue shifting of light from the forward direction, and red shifting of that from the rear. Near C this becomes extreme and things behind disappear, their light having shifted all the way into the far infrared. Things ahead gradually become bluer and bluer until they disappear into the far ultraviolet.

3) Intensification of radiation from the forward direction, and attenuation of that from behind. Near C this becomes extreme and the entire universe devolves into an intensely bright pinpoint of light, like a tremendously bright star, in the direction of motion. Everything else appears inky black.

Here's a video

http://www.youtube.com/watch?v=JQnHTKZBTI4

-drl


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Kon Dealer
professor emeritus


Reged: 01/05/11

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Re: Is lightspeed really a limit? new [Re: deSitter]
      #5477517 - 10/18/12 06:21 PM

Einstein showed in his paper on Special Relativity the relationship between relativistic (M)and rest mass (Mo).

M is Mo divided by the square root of 1 minus (velocity squared divided by speed of light squared).

When V=C then you have Mo divided by zero, which is infinite. i.e. M becomes infinite, as does the energy needed to accelerate it.

Essentially as you accelerate a mass towards the speed of light an increasing amount of the energy used is converted into mass,according to Einstein's energy mass equivalence equation (E = M*C squared).

So nothing with rest mass can reach the speed of light. Only massless particles such as photons (light)

Try plotting the relationship between M and V on Excel- it is quite instructive


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DarkSkys
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Re: Is lightspeed really a limit? new [Re: Kon Dealer]
      #5477834 - 10/18/12 10:00 PM

Quote:

Einstein showed in his paper on Special Relativity the relationship between relativistic (M)and rest mass (Mo).

M is Mo divided by the square root of 1 minus (velocity squared divided by speed of light squared).

When V=C then you have Mo divided by zero, which is infinite. i.e. M becomes infinite, as does the energy needed to accelerate it.

Essentially as you accelerate a mass towards the speed of light an increasing amount of the energy used is converted into mass,according to Einstein's energy mass equivalence equation (E = M*C squared).

So nothing with rest mass can reach the speed of light. Only massless particles such as photons (light)

Try plotting the relationship between M and V on Excel- it is quite instructive




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)

When you reach the point that even matter/antimatter power isnt enough?


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Mister T
Pooh-Bah


Reged: 02/01/08

Loc: Upstate NY
Re: Is lightspeed really a limit? new [Re: DarkSkys]
      #5478327 - 10/19/12 07:28 AM

the only way to answer that Q is to try it and measure the results.

currently an impossible task

so we HAVE to rely on the "on paper" answer.

the LHC does 99.99(?)% of c with a tremendous amount of energy/mass


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Jarad
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Re: Is lightspeed really a limit? new [Re: DarkSkys]
      #5478339 - 10/19/12 07:39 AM

Quote:

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


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Pess
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Reged: 09/12/07

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Re: Is lightspeed really a limit? new [Re: scopethis]
      #5478554 - 10/19/12 10:40 AM

Quote:

traveling faster than light one becomes "infinite mass", somewhat akin to a ghost(??). what would one "see"?





Actually, something that approaches 'c' approaches infinite mass. The point of 'c' is never reached..only approached. Infinite mass is never reached...only approached.

That is why 'c' is an effective speed limit. It can't be reached by any object possessing mass even if the entire mass of the Universe (except the object) were converted to energy in an effort to accelerate the object.

Ways around 'c'?

1) Take the object outside of normal space and accelerate it in a universe with different physical constants. Then just drop it back into our universe at sub-c. I'll leave the details to you guys.

2) Figure out what it is about particles possessing mass that determines their spatial coordinates in the fabric of space-time. Quantum theory tells us that an electron has a percentage chance to be found on either side of a barrier around a nucleus. What is seldom said is that there is also a certain probability that that same electron can be found on the other side of the universe. This 'probability' of finding it there is vanishingly small but still very real. Build a star ship that can manipulate this quantum probability and you can 'pop-up' anywhere in the Universe you want. I leave the details to you guys,

3) Build a Higgs-Bosun shield generator. When robbed of mass any particle instantly travels at 'c'. I'll leave the details to you guys.

4) If my back-of-the-envelope Lorenz transformation math is correct, if we can get a ship up to 99.9% speed of light the crew would experience 1 year for every 22.36 years Earth side observers would experience. Still, the size of the Universe dwarfs this so that explorers--even though removed from Earth kin due to time dilation--would still only find a tiny fraction of star systems reachable in their own lifetimes. Still, just need to adapt a Hemi V8 to a space craft and we are good to go. I'll leave the details to you guys.

Pesse (Get to work, you guys.) Mist


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moynihan
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Reged: 07/22/03

Loc: Lake Michigan Watershed
Re: Is lightspeed really a limit? new [Re: sirchz]
      #5478567 - 10/19/12 10:47 AM

Matter cannot accelerate to meet or exceed the speed of light.
Matter can travel faster than the speed of light.
But perhaps most importantly, space itself may not be subject to the same limits.

A practical example?

Alcubierre Drive

Edited by moynihan (10/19/12 10:50 AM)


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Jarad
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Re: Is lightspeed really a limit? new [Re: Pess]
      #5478844 - 10/19/12 01:34 PM

Quote:

2) Figure out what it is about particles possessing mass that determines their spatial coordinates in the fabric of space-time. Quantum theory tells us that an electron has a percentage chance to be found on either side of a barrier around a nucleus. What is seldom said is that there is also a certain probability that that same electron can be found on the other side of the universe. This 'probability' of finding it there is vanishingly small but still very real. Build a star ship that can manipulate this quantum probability and you can 'pop-up' anywhere in the Universe you want. I leave the details to you guys,




Ah, yes, the old Improbability Drive. Excellent choice.

Quote:

4) If my back-of-the-envelope Lorenz transformation math is correct, if we can get a ship up to 99.9% speed of light the crew would experience 1 year for every 22.36 years Earth side observers would experience. Still, the size of the Universe dwarfs this so that explorers--even though removed from Earth kin due to time dilation--would still only find a tiny fraction of star systems reachable in their own lifetimes.




Why settle for 99.9% C? That's only good for local travel. The discerning intergalactic tourist will take nothing less than 99.9999999999999% C. If you want to keep your inter-galactic cruise time under 1 year, that's the only way to travel.

Jarad


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Andy Taylor
Twisted, but in a Good Way
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Re: Is lightspeed really a limit? new [Re: Jarad]
      #5478867 - 10/19/12 01:53 PM

>>>Ah, yes, the old Improbability Drive. Excellent choice.

Yup, and you would be in time for dinner at the Restaurant at the End of the Universe...


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Pess
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Re: Is lightspeed really a limit? new [Re: Andy Taylor]
      #5478960 - 10/19/12 02:50 PM

Why settle for 99.9% C? That's only good for local travel. {quote] The discerning intergalactic tourist will take nothing less than 99.9999999999999% C. If you want to keep your inter-galactic cruise time under 1 year, that's the only way to travel.

Jarad




Pesse (I always obey all posted speed limits.) Mist


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snowboycosmos
super member


Reged: 07/18/12

Re: Is lightspeed really a limit? new [Re: Pess]
      #5523331 - 11/16/12 07:08 PM

In 1999 observations by the Hubble Space Telescope, the motion of M 87's jet was measured at four to six times the speed of light.

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Carl Coker
member


Reged: 07/30/12

Loc: Ohio
Re: Is lightspeed really a limit? new [Re: snowboycosmos]
      #5523417 - 11/16/12 08:15 PM

Quote:

In 1999 observations by the Hubble Space Telescope, the motion of M 87's jet was measured at four to six times the speed of light.



True, but that's only an apparent speed caused by an optical illusion. If you correct for the light travel time and the fact that the jet is oriented towards us, the actual velocity you recover is lower than c.


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StupendousMan
super member


Reged: 08/21/05

Re: Is lightspeed really a limit? new [Re: Carl Coker]
      #5523472 - 11/16/12 09:11 PM

I spend one day in my relativity class talking about these superluminal motions; maybe you'd enjoy the material.

http://spiff.rit.edu/classes/phys200/lectures/superlum/superlum.html


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Joad
Wordsmith
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Reged: 03/22/05

Re: Is lightspeed really a limit? new [Re: StupendousMan]
      #5523641 - 11/16/12 11:27 PM

That's a pretty stupendous lecture. No fooling.

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InterStellarGuy
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Re: Is lightspeed really a limit? new [Re: Jarad]
      #5531343 - 11/20/12 11:47 PM

Quote:

Quote:

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





The Orion pulse drive theoretically could achieve .1C, which just relies on nuclear bombs, and if powered instead by pulses from antimatter/matter reactions, theoretically .5 - .8 C.


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Pess
(Title)
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Reged: 09/12/07

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Re: Is lightspeed really a limit? new [Re: InterStellarGuy]
      #5532342 - 11/21/12 02:06 PM

Quote:

The Orion pulse drive theoretically could achieve .1C, which just relies on nuclear bombs, and if powered instead by pulses from antimatter/matter reactions, theoretically .5 - .8 C.




If 'c' becomes an effective barrier to speed then colonization ships are our only fallback position. And, as a practical outcome, these ships would become permanent habitats by the time any planet fall is made. Which, incidentally, might be an explanation as to the lack of neighbors dropping in to borrow a cup of sugar.

We don't really understand 'gravity' well enough yet to say 'c' is an absolute limit..at least in my mind. No mass will ever be accelerated by raw energy to 'c' velocity...but there may be undetected loopholes. For example, theory says no mass can be accelerated exactly to 'c'. Doesn't say anything about objects traveling above 'c'.

Pesse (Just got to get around the Universes speed trap.) Mist


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llanitedave
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Re: Is lightspeed really a limit? new [Re: Pess]
      #5533147 - 11/21/12 11:42 PM

We don't yet have to say c is an absolute limit, since the practical limit occurs a lot earlier.

One of these days we'll face the fact -- speed is expensive, time is cheap. Live longer, go slower, enjoy the trip.


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Mister T
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Reged: 02/01/08

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Re: Is lightspeed really a limit? new [Re: llanitedave]
      #5533649 - 11/22/12 10:06 AM

where's the profit in THAT!?

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llanitedave
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Re: Is lightspeed really a limit? new [Re: Mister T]
      #5534068 - 11/22/12 02:53 PM

The interest compounds as you go.

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Pess
(Title)
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Re: Is lightspeed really a limit? new [Re: llanitedave]
      #5540222 - 11/26/12 12:19 PM

Quote:

The interest compounds as you go.




Pesse (Which Ferengi rule of Acquisition is that?) Mist


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scopethis
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Re: Is lightspeed really a limit? new [Re: Pess]
      #5540360 - 11/26/12 01:56 PM

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

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Carl Coker
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Re: Is lightspeed really a limit? new [Re: scopethis]
      #5542459 - 11/27/12 04:47 PM

Photons are their own antiparticles, actually.

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deSitter
Still in Old School


Reged: 12/09/04

Re: Is lightspeed really a limit? new [Re: Carl Coker]
      #5543447 - 11/28/12 09:16 AM

Quote:

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


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Starman1
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Re: Is lightspeed really a limit? new [Re: deSitter]
      #5571826 - 12/15/12 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.


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scopethis
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Re: Is lightspeed really a limit? new [Re: Starman1]
      #5572593 - 12/15/12 01:15 PM

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

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Starman1
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Re: Is lightspeed really a limit? new [Re: scopethis]
      #5572834 - 12/15/12 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.........................

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mistyridge
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Re: Is lightspeed really a limit? new [Re: Starman1]
      #5573574 - 12/16/12 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.

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Jarad
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Re: Is lightspeed really a limit? new [Re: mistyridge]
      #5573728 - 12/16/12 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.

Jarad


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mistyridge
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Re: Is lightspeed really a limit? new [Re: Jarad]
      #5574199 - 12/16/12 01:52 PM

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

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llanitedave
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Re: Is lightspeed really a limit? new [Re: mistyridge]
      #5574921 - 12/16/12 10:44 PM

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

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Pess
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Re: Is lightspeed really a limit? new [Re: mistyridge]
      #5575651 - 12/17/12 12:42 PM

Quote:

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'.

Pesse (Where is the throttle on this buggy??!!) Mist


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Pess
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Re: Is lightspeed really a limit? new [Re: Pess]
      #5575660 - 12/17/12 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


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dyslexic nam
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Re: Is lightspeed really a limit? new [Re: Jarad]
      #5575942 - 12/17/12 04:03 PM

Quote:

Quote:

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.


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scopethis
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Re: Is lightspeed really a limit? new [Re: dyslexic nam]
      #5576046 - 12/17/12 05:03 PM

where is the belly button of the Universe?

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

Behind the lint

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FirstSightModerator
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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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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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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
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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
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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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Re: Is lightspeed really a limit? new [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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