Near Light Speed Travel Possible After All? 539
DrStrabismus writes "PhysOrg has a story about research that may indicate that close to light speed travel is possible. From the article: 'New antigravity solution will enable space travel near speed of light by the end of this century, he predicts. On Tuesday, Feb. 14, noted physicist Dr. Franklin Felber will present his new exact solution of Einstein's 90-year-old gravitational field equation to the Space Technology and Applications International Forum (STAIF) in Albuquerque. The solution is the first that accounts for masses moving near the speed of light.'"
Actual papers... (Score:5, Informative)
Weak 'Antigravity' Fields in General Relativity [arxiv.org]
Exact Relativistic 'Antigravity' Propulsion [arxiv.org]
Personally I'm a bit skeptical about his claims, however energy appears to be conserved. This method uses gravitationally-mediated kinetic energy exchange - this is the same principle that allows gravitational slingshot [wikipedia.org] to work.
Has Slashdot become crackpot central? (Score:5, Informative)
Re:Missing Something (Score:3, Informative)
What complete and utter nonsense. While I doubt I will see working antigravity in my lifetime (or if it is even possible at all), the idea that you must "know the exact cause" of something to manipulate it effectively is rubbish. Electromagnetic fields were not well explained until many decades after they had been successfully used in engineering applications (telegraph, lightbulb, radio). Even then it was much later that the much more accurate theory of Quantum Electrodynamics (widely considered to be the single most accurately tested theory in all of physics)...
Also you have to have good knowledge of the path involved. Imagine passing a asteroid 10m across at the speed of light. If your system cannot accomodate for the effects then most likely you'll be a smear inside the ship if the ship survives.
Ah ha, now there's a much more reasonable objection. The answer to this is simple - statistics. It's quite possible that near-lightspeed travel will be a tremendous gamble, one which will only be won by the use of massive redundancy. Instead of sending a single ship, we send hundreds or thousands, until one makes it. It's not like we're exactly running out of people any time soon.
Best bet is to hope that there's a nth demension you can pop into that allows you to travel the same spatime line without worrying about the mass of objects in the path.
That would be nice, but IIRC, there are no current theories that are either accepted or considered promising within the physics community that provide a mechanism for interdimensional transport using non-exotic mass/energy.
I dont see the two coming around anytime soon. It would be best to focus efforts on speedy travel between earth, mars, and the asteroid belt. Longer missions to the outer planets are fine but mars is our best bet for establishing a second colony of humans in case earth gets smeared by a large asteroid.
In 1900 people didn't see landing on the moon as coming any time soon, nevertheless it was written about and eventually studied. Our innate need to push the envelope in science and technology leads to many breakthroughs, intentional or not. More importantly it helps to inspire the next generation of scientists and engineers. When I interned at JPL, my supervisor said that that was the primary goal of NASA, and I believe it is a valid one.
Disclaimer: I am not a physicist, but I do have a B.S. in Physics.
Re:Pretty cool but useless (Score:2, Informative)
- If you travel fast enough you can get as far as you like in as short a time as you like. There's an effect called time dilation. Maybe you haven't heard of it?
- Have you every tried to compute the distance you can cover assuming a constant acceleration of, say, a tolerable 2G. The distance you can get in a time t in your own frame of reference grows exponentially (well, hyperbolically cosinusoidaly which is much the same thing) with t because of time dilation. When you've mastered the physics required you may be pleasantly surprised by how far that distance is.
Methinks you know not of what you speak.Re:Make sure you account for everything (Score:2, Informative)
Re:now (Score:2, Informative)
Regards,
Steve
Re:The subjunctive case (Score:5, Informative)
Nonono: he's saying that a mass travelling near the speed of light creates an "antigravity beam" in front of it. This sounds hokey, but it's not unprecedented - frame dragging is a similar situation where general relativity basically says that a moving body can "push" others nearby. So in this case the near-light-speed object is "dragging" its frame forward. Calling it an "antigravity beam" sounds wacko, but it's probably quite straightforward. It's almost like the objects would be riding the "wake" of the NLS object, caused by the fact that the object is moving faster than space can respond.
He's essentially saying that you can pretty much effortlessly accelerate something to really high velocities with little effort by hitching a ride on a bigger object.
(Where to find a star moving at greater than
Re:Make sure you account for everything (Score:5, Informative)
Re:The subjunctive case (Score:3, Informative)
Weight is more like mass * gravity.
Unfortunately the weight of the fuel doesn't determine how useful it is, its the mass. I actually thought up that several years ago, before I remembered that mass != weight.
Re:The subjunctive case (Score:3, Informative)
Re:name recognition (Score:2, Informative)
More immediately, Felber's new solution can be used to test Einstein's theory of gravity at low cost in a storage-ring laboratory facility by detecting antigravity in the unexplored regime of near-speed-of-light velocities.
I take it you're not very familiar with Dr. Franklin Felber's extensive background and work.
Re:WTF? (Score:5, Informative)
What if, after you have been accellerating for months, but are still at only 50% the speed of light, you hit a 1 lb chunk of rock/dust/ice that fell off some asteroid...
50% of speed of light = 1.5 x 10^8
1 pound = 0.4536 kg
Kinetic energy = (.5) (mass) (velocity) (velocity)
Kinetic energy = (.5) (.4536 kg) (1.5 x 10^8) (1.5 x 10^8)
Kinetic energy = (5.1 x 10^15)
Ouch.
The energy of the atomic bomb dropped on Hiroshima was only ~ 5.2 x 10^13
Even hitting a piece of sand at half the speed of light is gonna do waaaaaay more than just scratch your paint job. You want to get to get up to speed where you have the antigravity-clearing path for you as soon as possible, because every second going less than that speed is extremely dangerous. (That's if his theory isn't entirely bogus.)
Re:Make sure you account for everything (Score:2, Informative)
Re:Go fast enough to look like a black hole? (Score:4, Informative)
> would look like a black hole relative to a laboratory frame?
No [ucr.edu].
Re:name recognition (Score:3, Informative)
But interestingly, when I researched "Franklin S. Felber", I found conflicting dates for his degrees. At USC it says M.A. Physics, 1973; Ph.D. Physics, 1975. http://physics.usc.edu/Alumni/F.html [usc.edu]. But the University of Chicago notes an alumnus Franklin S. Felber, SM'74. http://magazine.uchicago.edu/0304/alumni/works.htm l [uchicago.edu]. Did he really get an MA in California in 1973 then a Masters in Chicago in 1974, then a PhD in 1975 in California?
How many Franklin S. Felbers are there? Perhaps he is well-known in some circles, and I could just be ignorant or mixed up. But I am getting the impression of an ambitious man here, and all that entails. Would someone who knows him well please straighten me out.
I did some calculations. (Score:3, Informative)
However, this is actually an underestimate since relativistic effects make it harder to get that close to the speed of light, the closer you get. If you could achieve a constant 1G, that is how long it would take, but this is physically impossible since effective mass increases with velocity.
I calculated it on Google calculator with the following formula (just type into search):
Re:Why not faster than light (Score:2, Informative)
That's bullshit. Theory is based on experimental evidence, and there is a century's worth of experimental evidence supporting relativity, including accelerating particles to enormous energies to within a tiny, tiny fraction of the speed of light. We find, just as relativity predicts, that as the particle's speed increases, additional inputs of energy give rise to less and less change in speed, so that its speed always asymptotically approaches that of light, never reaching it. First 99.999% of c, then 99.9999% of c, then 99.99999% of c, etc.
More nonsense. There are many things in science that are not merely "guesses" or "rough estimates", but rather are established beyond all credible doubt. There are guesses and rough estimates too, as well as things in between. (There is never proof in the mathematical sense, because it is logically impossible to prove a scientific theory 100%.)
That's also wrong. Scientists are encouraged to communicate with the lay public. You're simply not supposed to announce brand new results to the public before they've gone through peer review. Unfortunately, funding crunches have made "publication by press release" dismayingly common in recent years.
One quickly gets the idea that you not only don't know how science works or what it is, but you also don't know any scientists personally.
What the hell are you talking about? Nothing in science is totally authoritarian. There is nothing more contentious than a group of scientists arguing with each other about who's right.
Idiot. The word "law" as it is used in science does not imply that "laws" cannot have exceptions. Where did you get your knowledge of science, out of an elementary school textbook?
Regardless of what an individual scientist may claim, the truth of the matter is ultimately sorted out in the peer reviewed literature. That's the whole point of the scientific process: it's self-correcting.
Your are not the daring unconventional thinker you fancy yourself to be. In fact, kneejerk dismissal of perceived "authority" by self-proclaimed "freethinkers" is part of Slashdot groupthink. Intelligent people question claims (which has nothing to do with "authority"), but they also make sure they are informed, and you are not remotely informed about science, the scientific process, or the scientific community.
Re:Bah. (Score:1, Informative)
Except that experimentally, this is not true. The amount of energy to accelerate from v to v+dv increases as v approaches the speed of light (c), even for fixed dv. This is demonstrated in particle accelerators every day.
Near light speed weapons are desirable (Score:3, Informative)
They would be more difficult to intercept.
They could be smaller, same kinetic energy yield for less mass.
You do realize we nearly have light speed weapons? Lasers. One of the benefits is that for practical purposes flight time from weapon to target is zero. No more having to lead the target. It makes interception of fast moving things far more practical.
Re:I did some calculations. (Score:3, Informative)
try;
(c / g) in days = 353.823183 days
(the 'in days' is needed so g insn't taken to mean 'grams')
Re:WTF? (Score:2, Informative)
The speed of light is 299,792,458 meters per second.
29166 / 299792458 = 9.7287304 × 10-5
Therefore, in order for the Earth to remain in a constant orbit around the sun, it maintains a speed which is so small a percentage of the speed of light as to not be worth mentioning. So you might have a wee bit of trouble maintaining an orbit around a planet while booting along at 57% of the speed of light.
Just to illustrate the point even better, at 57% of the speed of light, you could hurtle on a straight-line trajectory between Pluto and the Sun in about 5 and a half hours. How much do you suppose a planets gravety field would deflect your trajectory during that time period? Or the Sun's gravity field for that matter?
Re:Make sure you account for everything (Score:5, Informative)
He's talking about this:
http://math.ucr.edu/home/baez/physics/Relativity/S peedOfLight/Superluminal/superluminal.html [ucr.edu]
And he's right, in that yes, sometimes things CAN appear to be moving faster than light at first calculation. I don't think it would work exactly as he described with an object coming straight at you, however.
Bruce
Re:Has Slashdot become crackpot central? (Score:1, Informative)
Re:Make sure you account for everything (Score:3, Informative)
Yeah, you're probably right. These sorts of things are sometimes called relativistic kill vehicles in sci-fi, and come in handy during fictional interstellar warfare:
http://en.wikipedia.org/wiki/Relativistic_kill_ve
A relativistic kill vehicle (RKV) or relativistic bomb is a hypothetical weapon system sometimes found in science fiction. The details of such systems vary widely, but the key common feature is the use of a massive impactor travelling at a significant fraction of light speed to strike the target. At these relativistic velocities the mass could carry immense amounts of kinetic energy, potentially several times that of its rest mass energy equivalent (ie, the amount of energy that would be released if its rest mass were totally converted into free energy).
RKVs have been proposed as a method of interstellar warfare, especially in settings where faster than light travel or sensors are impossible. By travelling near the speed of light an RKV could substantially limit the amount of early warning detection time. Furthermore, since the destructive effects of the RKV are carried by its kinetic energy, destroying the vehicle near its target would do little to reduce the damage; the cloud of particles or vapor would still be travelling at nearly the same speed and would have little time to disperse. Indeed, some versions of the RKV concept call for the RKV to explode shortly before impact to shower a wide region of space.
Since they would likely be difficult to provide much terminal guidance to, RKVs are usually proposed as a strategic weapon targeted against large and relatively immobile targets such as planets. Accelerating a mass to such velocities in the first place will likely require vast amounts of energy and large, unwieldy accelerators.
Re:Has Slashdot become crackpot central? (Score:5, Informative)
No. (For one thing, Cerenkov radiation is a physical phenomenon that operates only for masses travelling above a fixed speed.)
All this is saying is that if you've got an object (say object A) at rest, and another object (say object B) approaching object A at more than 0.577c in object A's reference frame, object A will be pushed forward (away from object B). Obviously if object A and object B are aligned exactly, they'll collide - but if object A is off-axis from object B, it will be "pushed along" with object B.
Since the relative velocity is measured in one object's rest frame, it's Lorentz invariant. (Object B sees object A approaching it at 0.577c, and sees object A pushing object B backwards).
It's very similar to frame dragging, actually. With frame dragging, there is likely a "critical rotational velocity" above which an object near the rotating object will be forced into an orbit. There's probably a "critical rotational velocity" above which an object deflects every incident object away from it.
And as with frame dragging, it likely exists for lower velocities - but the "push" is probably not along the axis of object A's direction, which means it won't "push" the object along.
Re:"noted physicist"? (Score:3, Informative)
In other words, 2+2 is not any more valid when posed by the pope than by Hitler. Or to go less concrete, Relativity would have been no more or less likely if Hitler has proposed it rather than Einstein.
Judge the good doctors ideas on their merits rather than on his merits.
Re:Huh? (Score:3, Informative)
For velocity-dependent relativistic effects such as time dilation and space contraction, it turns out that though observers apparently see different things their observations are all valid and consistent with each other. This is the truly astounding thing about relativity that takes a while to wrap your brain around.
For this guy's "anti-gravity beam" effect, people are complaining that it doesn't seem like the views of different observers can be reconciled. For example, people on a spaceship moving at .95c relative to Earth would observe Earth emitting an anti-gravity beam (it appears to be moving at .95c relative to them as all velocity is relative); yet the effects of such a beam would easily be noticed by us and we don't see any.
Of course, this is press-release science; undoubtedly the real issues are more complex and subtle.
Re:Make sure you account for everything (Score:2, Informative)
Re:Near light speed weapons are desirable (Score:2, Informative)
Right now we don't really need them, but they'd be awfully handy in a real space battle. Lasers and other beam weapons really suck for space weapons, since ships would be engaging each other light-seconds apart--by the time the laser reaches where it's aimed at, the other ship will have moved somewhere else. Even if you *do* manage to hit them (say if they were standing still or not evading . . . ) the beam will have spread out like a flashlight and not do very much damage.
On the other hand, if you have .9c missiles that can track and manuever with an evading enemy ship, they can be tiny (1 kg or so) and still pack the wallop of a nuclear weapon when they hit. =)