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Boeing Joins In Anti-Gravity Search
SimcoFrappe writes: "BBC News reports that Boeing is trying to extend the research of Russian scientist Dr. Yevgeny Podkletnov to develop a device to shield against gravity. The military branch of the British BAe Systems announced a similar program in 2000. One step closer to cheap space travel or just more sci-fi jive?"
But I must be off now. I've got a YBa_2Cu_3O_{7-x} widget factory to get off the ground. :B
He pointed to the fact that an Irish university (sorry - don't remember which) had spent quite some time reproducing the experiment, and that this re-running of the experiment had failed to verify a single claim.
I'd love this to be true. Sadly however, at this moment I'd have to put myself in the non-believer camp.
Cheers,
Ian
Hmm, although I agree it's difficult to say that shielding against gravity is impossible, the above is not exactly sound logic. You need to look at the origin of the forces in question to see why.
The general relativistic model of gravity as the effect of warped spacetime would seem to indicate that blocking gravity could be a fundamentally different problem than blocking electromagnetic radiation.
Electromagnetic radiation travels through spacetime, i.e. it follows the curvature of spacetime. Blocking it is simply a matter of constructing the right kind of interfering device, such as a faraday cage, to prevent electromagnetic photons/wave packets from penetrating.
OTOH, according to GR, gravity as we perceive it is essentially a secondary effect due to the curvature of spacetime. To "block" it, you would have to be able to uncurve spacetime in the vicinity you wish to block. This is a little different from blocking photons. The only thing we've ever discovered that's capable of warping spacetime is "mass". So sure, we can counter the effects of gravity, there's no mystery about it: simply use a mass as large as the mass of the object whose gravitational effects you want to counter.
Unfortunately, in the case of gravity, this doesn't really work the way we want. Let's say I create a black hole with a similar mass to that of the Earth (I have a fairly well-equipped basement). In the vicinity of the black hole, I would feel a force towards the hole (please no goatse jokes) of approximately 1G (adjust masses to achieve appropriate effect outside the Schwarzchild radius, etc.) So if I hang the black hole from my ceiling, I could create a micro-gravity environment in my basement, with the force upward cancelling the force downward.
Astute readers have by now noticed a slight problem with this scenario. Despite my well-equipped basement, I don't happen to possess a means for suspending an Earth-mass object a few feet above another Earth-mass object (i.e. the Earth itself). There's not going to be a heck of a lot I can do about the fact that my black hole is going to shoot down towards the earth under a combined force of 2G and a momentum that would require numbers with "E" in them to describe. (I had better not be standing beneath it, if I want to avoid rather nasty tidal effects as the black hole travels through my body - that killed a guy on Mars once.)
Because of the nature of gravity, "shielding" against its effects may not even be meaningful. Even if it is possible, it's highly doubtful that we will stumble across the solution by random experimentation with e.g. spinning disks. Spinning disks might confuse researchers, but they don't confuse the universe.
So we have GMm/r^2 = GHm/s^2. The G and m cancel out, leaving M/r^2 = H/s^2. Using an Earth mass of 5.9736 x 10^24 kg, and a radius of 6370000m, and assuming s=1m, my calculations show that the black hole would need a mass of 1.472 x 10^11 kg (147 billion kilograms) to create a micro-gravity environment in my basement - however localized, and however briefly. That's hundredths of trillionths of the mass of the Earth - quite a lot lighter, as Rhombus guessed.
For those who are interested, Pascal's Wager actually involves something far more significant.
Got Wisdom?
Early theorys described gravity acting like a wind that would blow you towards the ground. It was later extended to include a wind from all directions blowing at the same time. Newtons gravity theorys were based on this concept and it was a problem that lead him to the idea of intergration. The integration of a pushing wind with the earth blocking it was much more difficult than the integration of just the earth sucking and the result was a bit of math seen in modern physics books.
The biggest problem with the gravity pushes theory was that things in space would slow down over time. Also as you speed up, you would need more energy to keep accelerating. Low orbit wouldn't be zero G, but zero differential G. Depending on how fast the gravity wind was and its strength, their would be no way to exceed its speed. The early attempts to quantify it thought there would be no way for the wind to go through the entire earth so the force you feel was considered its maxium which made it hard to explain higher gravity area like the sun and Saturn. There were a few other problems with the idea as well and it went away with the acceptance of the modern theory.
His latest paper came out last August - no more spinning superconductors, now he's playing with huge voltages on a fixed superconductor. It sounds interesting; I can't tell you if it's real or not, but maybe Boeing can figure something out. Here's a link to the more recent paper:
http://arxiv.org/abs/physics/0108005