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InterStellarGuy
professor emeritus

Reged: 06/25/08

Loc: Overland Park, KS
Re: Is lightspeed really a limit? [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.

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)

Reged: 09/12/07

Loc: Toledo, Ohio
Re: Is lightspeed really a limit? [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
Humble Megalomaniac

Reged: 09/26/05

Loc: Amargosa Valley, NV, USA
Re: Is lightspeed really a limit? [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
Pooh-Bah

Reged: 02/01/08

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

where's the profit in THAT!?

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llanitedave
Humble Megalomaniac

Reged: 09/26/05

Loc: Amargosa Valley, NV, USA
Re: Is lightspeed really a limit? [Re: Mister T]
#5534068 - 11/22/12 02:53 PM

The interest compounds as you go.

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Pess
(Title)

Reged: 09/12/07

Loc: Toledo, Ohio
Re: Is lightspeed really a limit? [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
Postmaster

Reged: 05/30/08

Loc: Kingman, Ks
Re: Is lightspeed really a limit? [Re: Pess]
#5540360 - 11/26/12 01:56 PM

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

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Carl Coker
member

Reged: 07/30/12

Loc: Ohio
Re: Is lightspeed really a limit? [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? [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
Vendor (EyepiecesEtc.com)

Reged: 06/24/03

Loc: Los Angeles
Re: Is lightspeed really a limit? [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
Postmaster

Reged: 05/30/08

Loc: Kingman, Ks
Re: Is lightspeed really a limit? [Re: Starman1]
#5572593 - 12/15/12 01:15 PM

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

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Starman1
Vendor (EyepiecesEtc.com)

Reged: 06/24/03

Loc: Los Angeles
Re: Is lightspeed really a limit? [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
Post Laureate

Reged: 10/28/05

Loc: Loomis, CA
Re: Is lightspeed really a limit? [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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Postmaster

Reged: 04/28/03

Loc: Atlanta, GA
Re: Is lightspeed really a limit? [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.

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mistyridge
Post Laureate

Reged: 10/28/05

Loc: Loomis, CA
Re: Is lightspeed really a limit? [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
Humble Megalomaniac

Reged: 09/26/05

Loc: Amargosa Valley, NV, USA
Re: Is lightspeed really a limit? [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
(Title)

Reged: 09/12/07

Loc: Toledo, Ohio
Re: Is lightspeed really a limit? [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

 Post Extras:
Pess
(Title)

Reged: 09/12/07

Loc: Toledo, Ohio
Re: Is lightspeed really a limit? [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

 Post Extras:
dyslexic nam
Carpal Tunnel

Reged: 01/28/08

Re: Is lightspeed really a limit? [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.

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

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scopethis
Postmaster

Reged: 05/30/08

Loc: Kingman, Ks
Re: Is lightspeed really a limit? [Re: dyslexic nam]
#5576046 - 12/17/12 05:03 PM

where is the belly button of the Universe?

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