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FTL spaceships.

 
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Senmut
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Joined: 15 Jul 2006
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PostPosted: Fri Aug 15, 2008 12:38 am    Post subject: FTL spaceships. Reply with quote

Cool, huh?
Now, where do we mine the tylium?

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http://www.space.com/businesstechnology/080813-tw-warp-speed.html

Spaceship Could Fly Faster Than Light

By Jeremy Hsu
Staff Writer
posted: 13 August 2008
07:12 am ET


Travel by bubble might seem more appropriate for witches in Oz, but two physicists suggest that a future spaceship could fold a space-time bubble around itself to travel faster than the speed of light.

We're talking about the very distant future, of course.

The idea involves manipulating dark energy the mysterious force behind the universe's ongoing expansion to propel a spaceship forward without breaking the laws of physics.

"Think of it like a surfer riding a wave," said Gerald Cleaver, a physicist at Baylor University. "The ship would be pushed by the spatial bubble and the bubble would be traveling faster than the speed of light."

In theory, the universe grew faster than the speed of light for a very short time after the Big Bang, driven by the dark energy that represents about 74 percent of the total mass-energy budget in the universe. Dark matter constitutes 22 percent of the budget, and normal matter (stars, planets and everything you see) makes up the remaining 4 percent or so.

Strange as it sounds, current evidence supports the notion that the fabric of space-time can expand faster than the speed of light, because the reality in which light travels is itself expanding.

Cleaver and Richard Obousy, a Baylor graduate student, tapped the latest idea in string theory to devise how to manipulate dark energy and accelerate a spaceship. Their notion is based on the Alcubierre drive, which proposes expanding space-time behind the spaceship while also shrinking space-time in front.

String theorists had believed that a total of 10 dimensions exist, including height, width, length and time. The other six dimensions exist largely as unknowns, but everything is based on hypothetical one-dimensional strings. A newer theory, called M-theory, suggests that those strings all vibrate in yet another dimension.

Manipulating that additional dimension would alter dark energy in terms of height, width, and length, Cleaver and Obousy theorize. Such a capability would permit the altering of space-time for a spaceship, taking advantage of dark energy's effect on the universe.

"The dark energy is simultaneously decreased just in front of the ship to decrease (and bring to a stop) the expansion rate of the universe in front of the ship," Cleaver told SPACE.com. "If the dark energy can be made negative directly in front of the ship, then space in front of the ship would locally contract."

This loophole means that the spaceship would not conflict with Einstein's Theory of Relativity, which states that objects accelerating to the speed of light require an infinite amount of energy.

However, the Baylor physicists estimate that manipulating dark energy through the extra dimension requires energy equivalent to the converting the entire mass of Jupiter into pure energy enough to move a ship measuring roughly 33 feet by 33 feet by 33 feet.

"That is an enormous amount of energy," Cleaver said. "We are still a very long ways off before we could create something to harness that type of energy."

The workaround solution may leave fans of Einstein pleased. But for now, faster-than-light travel remains, like Oz, a pleasant fantasy.
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LZaza



Joined: 21 Jul 2006
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Location: Victoria, British Columbia, Canada

PostPosted: Sun Sep 14, 2008 5:19 am    Post subject: Reply with quote

Cool, Sen.

Reminds me of the wormhole theories to a certain degree, and the incredible energy needed to open the wormhole.
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Senmut
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PostPosted: Sun Sep 14, 2008 6:10 am    Post subject: Reply with quote

True, but recall...our civilization was once incapable of creating and harnessing the "tremendous energies" required to get a heavier-than-air vehicle into motion, let alone off the ground. Today, it happens all the time, and we have a permanent station in orbit. Once, using light to affect objects form great distances was unthinkable. Today, we have lasers that could incinerate whole buildings, if not cities, from hundreds of miles away. Science has opened new vistas in energy access, and will continue to do so.
Just a matter of time.
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Senmut
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PostPosted: Fri Oct 09, 2009 6:33 am    Post subject: Reply with quote

We are getting closer, folks. Love seeing this happen.



http://www.technologyreview.com/blog/arxiv/24211/


Hyperdrive Propulsion Could Be Tested at the Large Hadron Collider
The principle behind a novel form of spacecraft propulsion could be tested at the world's most powerful particle accelerator.

In 1924, the influential German mathematician David Hilbert published a paper called "The Foundations of Physics," in which he outlined an extraordinary side effect of Einstein's theory of relativity.

Hilbert was studying the interaction between a relativistic particle moving toward or away from a stationary mass. His conclusion was that if the relativistic particle had a velocity greater than about half the speed of light, a stationary mass should repel it. At least, that's how it would appear to a distant inertial observer.

That's an interesting result, and one that has been more or less forgotten, says Franklin Felber, an independent physicist based in the United States. (Hilbert's paper was written in German.)

Felber has turned this idea on its head, predicting that a relativistic particle should also repel a stationary mass. He says that this effect could be exploited to propel an initially stationary mass to a good fraction of the speed of light.

The basis for Felber's "hypervelocity propulsion" drive is that the repulsive effect allows a relativistic particle to deliver a specific impulse that is greater than its specific momentum, thereby achieving speeds greater than the driving particle's speed. He says this is analogous to the elastic collision of a heavy mass with a much lighter, stationary mass, from which the lighter mass rebounds with about twice the speed of the heavy mass.

What's more, Felber predicts that this speed can be achieved without generating the severe stresses that could damage a space vehicle or its occupants. That's because the spacecraft follows a geodetic trajectory, in which the only stresses arise from tidal forces (although it's not clear why those forces wouldn't be substantial).

That's a neat idea, but little better than science fiction, were it not for one further corollary: Felber is proposing an experiment that could prove his ideas or damn them.

It turns out that when it is up and running, the Large Hadron Collider (LHC) will accelerate particles to the kind of energies that generate this repulsive force. Felber's idea is to set up a test mass next to the beam line and measure the forces on it as the particles whiz past.

The repulsive force that Felber predicts will be tiny, but it could be detected using resonant test mass. And since the experiment wouldn't interfere with the LHC's main business of colliding particles, it could be run in conjunction with it.

While the huge energy of the LHC makes it first choice for such an experiment, Felber says the effect could also be seen at Fermilab's Tevatron, albeit with a signal strength that would be three orders of magnitude smaller.

Perhaps that's something to consider as a last hurrah for the old Tevatron, before they begin mothballing it sometime next year.

Ref: arxiv.org/abs/0910.1084: Test of Relativistic Gravity for Propulsion at the Large Hadron Collider
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MAD
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PostPosted: Sat Jun 26, 2010 8:53 am    Post subject: Reply with quote

Why FTL implies time travel (tachyon pistols)

The entire "FTL implies time travel" meme has to do with what's sometimes called "failure of simultaneity at a distance". In addition to the effects that pop treatments of relativity mention (that is, time dilation and length contraction), relativity proposes that the definition of "right now" is also different, depending on which observer's coordinate system you use. This is an effect much like the revolution of deciding that the direction "up" wasn't the same everywhere, but varied from place to place on earth. With relativity, the revolutionary notion is that the direction "futureward" (or "now-ward") isn't the same everywhere, and varies with velocity.

We can describe this effect by idealizing FTL to be "instantaneous", and describing how the more familar time dilation implies this effect. But remember, the same points apply to any FTL speed, you just have more messy arithmetic to grind through.

Consider a duel with tachyon pistols. Two duelists, A and B, are to stand back to back, then start out at 0.866 lightspeed for 8 seconds, turn, and fire. Tachyon pistol rounds move so fast, they are instantaneous for all practical purposes.

So, the duelists both set out --- at 0.866 lightspeed each relative to the other, so that the time dilation factor is 2 between them. Duelist A counts off 8 lightseconds, turns, and fires. Now, according to A (since in relativity all inertial frames are equally valid) B's the one who's moving, so B's clock is ticking at half-speed. Thus, the tachyon round hits B in the back as B's clock ticks 4 seconds.

Now B (according to relativity) has every right to consider A as moving, and thus, A is the one with the slowed clock. So, as B is hit in the back at tick 4, in outrage at A's firing before 8 seconds are up, B manages to turn and fire before being overcome by his fatal wound. And since in B's frame of reference it's A's clock that ticks slow, B's round hits A, striking A dead instantly, at A's second tick; a full six seconds before A fired the original round. A classic grandfather paradox.

Note, this is NOT a matter of when light gets to an observer, it is NOT an optical illusion. It is due to the fact that, in SR, the question of what occurs at the "same time as" something else is observer dependent.

As A fired that first show at tick 8, the bullet effectively teleported from A's gun to B's back instantly --- instantly according to A. But for B, who was moving at 0.866 lightspeed WRT A, B was hit in the back by the bullet 4 seconds BEFORE the bullet was fired. And again note, this is NOT due to the optical illusion of lightspeed delay in viewing A's turn-and-shoot; the light form that event wouldn't reach B until MUCH later, not tick 4.

Here's a spacetime diagram of a referee (O3) and two duelists (O1 and O2). Space is up/down, time is left/right, in the diagram.



The paths O1 and O2 take through spacetime are the colorcoded arrowed lines. The events in spacetime that each considers "simultaneous" and "8 seconds after the start" are along the thinner, non-arrowed colorcoded lines. So we see that, each of the three observers thinks the other two have slow clocks, and that if we are allowed to move faster than a lightcone, we'll end up going "pastward" in somebody's reckoning.

We can trace out the shots on this diagram, also. Step through it one more time: if green shoots at 8 seconds out, the shot will go along the green "line of simultaneity", and hit blue at 4 seconds elapsed. If blue returns fire from there, it will return along a line paralel to the blue "line of simultaneity", and catch green napping at 2 seconds elapsed.
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