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Near Light Speed Travel Possible After All?
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.'"
Well, we have no problem running around in 1G for our whole live...
So weeks or months of acceleration wont hurt at all... in fact they would act as a convinient way of creating "artificial gravity" on the ship.
And even 1G adds up after a few days, and in a matter of a few months you are _highly_ relativistic.
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
Buick? You mean the size of a dust mote. If a dust particle weighs 1/100 of a gram, and you are going roughly the speed of light, the kinetic energy of the dust particle relative to you (assuming that the dust particle is roughtly standing still) is
.00001kg x (2.998 x 10^8 m/s)^2
898800400000 Newtons
9806 or so Newtons Per Ton
1,000,000 tons per MegaTon
20 Megatons per Hydrogen bomb
Thats 4.6 Hydrogen Bombs of energy that the dust particle has relative to you. Do you want to collide with 4.6 Hydrogen Bombs? I don't think that NLST is practicle, even if it turns out to be possible. What we need is a way to simultaniously transport stuff.
The density of interstellar space is about one atom per cubic centimeter. If the spaceship were going near the speed of light (3 x 10^10 cm/sec), it would be hit by 3 x 10^10 relativistic particles per cm^2/sec. This is about the equivalent of one Curie per cm^2, which would kill a human and cripple any electronics on board
A very heavy magnet could deflect the protons, but the neutral atoms would be unaffected by the magnetic field.
Moving faster than 57.7% of c? Relative to what?
Right now, the earth is moving through space at a speed greater than 57.7% relative to something. No, I don't know what, or where, but rest assured there's some body out there somewhere in whose frame of reference the Earth is moving at greater than 57.7% of c. And there's some other body in whose frame of reference the Earth is moving at greater than 10% of c, and another body where Earth is moving at 95% of c, and another body where Earth isn't moving at all (Hey, like me!).
So why isn't the Earth emitting such an antigravity beam, repelling masses in its path? Rest assured that if it were, we'd be seeing its effect, like ferinstance as it played havoc with GPS satellites.
Or, heck, there are cosmic rays which occasionally smack into the Earth's atmosphere at a speed that's only infinitesimally smaller than c in Earth's FOR. They should *definitely* be emitting some sort of antigravity, if this guy's correct. Should be trivial to observe, but we haven't seen it.
This smells like bullshit.
You make the assumption that the dust mote would actually stop, only then would the bulk of the KE go into the target space ship. More likely is that since the KE of each atom in the dust mote is so much larger than the atomic bond energy holding the grain together, the dust mote to the spacecraft really behaves like a very densely packed bundle of cosmic rays. If the spacecraft walls don't stop individual particles of that energy (ie like cosmic ray protons) then it won't stop the dust particle. The atoms would go in one side, out the other radiating a small fraction of their relative energy as gamma rays as cherenkov radiation and compton radiation. The dust would go out the other side as a diverging cone shaped spray of plasma.
Whatever you may personally think, he doesn't.
To an observer, the minimum time for another object to move from a point to another a light-year away is one year, yes; that's what makes c invariant. However, for the object moving, experinced time goes down asympotically as the speed of light is approached. If you were moving at c, you would experience literally no passage of time on the trip to Alpha Centauri from Earth, even though it would take you 4.3 years to an observer on Earth.
Another way to state it is that from the perspective of someone moving near the speed of light, the distance from Earth to Alpha Centauri shrinks; with the distance shorter, of course it takes less time to travel. However, the distance is still the same to the observer on Earth, and so the time for the trip as viewed by the observer is much longer.
(By the way, this is part of the reason why nothing can go faster than the speed of light; the distance between two points can't shrink to less than zero.)
This difference in space-or-time from different perspectives is why the theory is called relativity; space and time are not absolute constants for everyone evverywhere, but always exist relative to your reference frame.