In the future won’t it be possible to detect and measure gravity waves?
In theory couldn’t you measure the speed and mass of a particle by the gravity waves it gives off moving though space?
By measuring the gravity waves you could determine the particles direction and mass without interfering with it.
Doesn’t this make the Heisenberg’s Uncertainty Principle and old theory?
PerfectDark
The uncertainty principle states that the position and the velocity of an object cannot both be measured exactly, at the same time. The first question I’d raise is that your OP talks about recording direction and mass rather than position and velocity. Even using your hypothetical gravity meter, how are you going to record position and velocity at the same time?
Theoretically, but I won’t hold my breath… considering that scientists still aren’t exactly sure what gravity is. And gravity might not even “travel” or “wave”… both terms come with the implication that there’s some detectable motion to the gravity signal, but doesn’t current physics state that a change in a gravity field is instantly felt throughout the universe? Or is that just “old school” physics that’s been discarded?
In any case…
Nope. Something doesn’t become false just by saying that it might, one day, be proved false.
Ooops… sorry I was rushing the post because I had to go to dinner.
What I meant was position and momentum. The particle through space causes gravity waves which are collected by a detector all around the particle. The magnitude and the direction of the gravity waves given off are inputted into a 3 dimensional computer model and it determines the position and velocity.
And what I meant was “Won’t” this make the Heisenberg’s Uncertainty Principle an old theory? As in once it has been accomplished.
PerfectDark
I think gravity waves would themselves be subject to the uncertainty principle, and there will be a limitations on how accurately you can measure it.
A similar situation will arise if you shoot a particle into a magnetic or electric field, causing it to radiate electromagnetic radiation (photons). You can measure the radiation without direct interaction with the particle, but the measurement accuracy of the emitted photon is limited by the uncertainty principle.
scr4 if gravity waves exist then they will be distortions of space-time, not particles. Which I don’t think comes under the uncertainty principle.
PerfectDark
IANAP, but it would seem that the big problem here is your talk of modelling the position and velocity. It’s rather hard to come up with a model that gives you the exact position and velocity at the same instant that doesn’t involve either[list=1]
[li]approximating the position[/li][li]approximating the veolicty[/li][li]affecting one of the above[/li][/list=1]
Yes, if someone ever did manage to record both position and velocity at the same time that would invalidate the theory, but until that happens, it’s still valid.
The future is now. Several countries are building gravitational wave detectors. The US effort is called LIGO.
Definitely old school. Einstein’s General Theory of Relativity (GenThRel) predicts gravitational waves that propagate at the speed of Einstein’s constant (formerly known as “the speed of light in a vacuum”).
You are right, they will be distortions of space-time. However, the uncertainty priciple (UncPr) applies to all quantum-mechanical objects. GenThRel is currently only a classical theory (classical == non-quantum), but most physicists look forward to the day that a quantum theory of gravitation is understood. There will be much surprise if it turned out that gravitational waves don’t obey the UncPr.
It’s easy to measure both position and velocity. The UncPr only limits the accuracy you can measure them with. The simplest way is to have multiple position detectors. Note the time whenever the a gravity wave passes by each detector. The velocity is the distance between the detectors divided by the time it took the wave to get from one detector to the next. The more detectors you have the better precision you’ll get (limited by the UncPr).
Maybe. Maybe not.
rimshot
Okay, so I should have said “measured exactly”, but in fairness, I had just said that UncPR held that
But you’re quite right that measuring both is easy, to certain degrees of accuracy.
It has been a long time since I passed quantum mechanics but I think that something is not being understood here. The position of a particle is defined by the solution to its time-independent wave function psi. The momentum of the particle is related to the frequency of this wave function. the position of the particle is related to the position of the the wave packet.
If a particle has infinitely precise position, then its wave function would be described by a dirac function. But there is no frequency associated with a dirac function. This leaves the momentum infinitely unknown. Likewise, if the wave packet were stretched over infinite space so that its frequency were precisely defined. It’s location would be infinitely unknown.
There is no way around this. It doesn’t matter how the measurement was taken.
Perhaps you should define the properties you are attributing to this hypothetical graviton you are attempting to describe. It may be easier to explain why your theory doesn’t work if we know what it is.
As far as measurements go, gravity waves don’t give you anything that light doesn’t. To measure the position of an object to within some precision delta, you need waves of wavelength about delta or less. Short waves have high frequency, though, which means high energy and momentum, so when a particle interacts with such a wave (either by absorbing it or giving it off), its momentum changes greatly. It turns out that if you multiply the resulting uncetainties, you get the Heisenberg principle (or worse… Waves might not necessarily be the best way to measure a particle). This holds for any waves, electromagnetic, gravitational, or otherwise.
To add on to others posts (and not repeat what’s already been said), we should also note that gravity waves are hard to detect. The detector experiments are trying (and so far failing) to detect the gravitational effects of galaxies, stars, and planets.
The gravitational influence of a subatomic particle (even a very massy one, say a top quark), is amazingly tiny in comparison. It is a huge understatement to say that the experimental errors would tend to mask the actual data. Even in a future with reliable gravity detectors, they aren’t going to be using them in particle physics experiments.
Actually, waves are particles and particles are waves. When you are dealing with Quantum Stuff, the difference between particle and wave is blurred. And, the Uncertainty Princlple applies to any attempt to measure position and momentum.
As Christopher basically said:
If the momentum of a particle can be measured with absolute precision the particle does not, inherently, have a position and vice versa. It has nothing whatsoever to do with the measurement process.
It depends on how you look at it.
Okay, so I’m kind of a scientific kook around here, I got some crazy ideas. Here’s my take on HUP.
I think that the reason HUP holds up in common studies is because we can, so far, only measure certain variables of a particle’s characteristics. Because all the aspects of a particles characteristics are not known, being measured, or even measureable by modern science, we cannot accurately determine it’s exact velocity and position.
I would wager that the HUP begins to break down when you near either absolute zero or absolute one*. The reason for this is simple, the closer to zero energy that a particle has, the less variables are influencing it’s actions and position, because they all become ‘zeroed’ out as we near AZ, and a variable with a value of zero can be ignored. The problem with hitting AZ is that the particles in question disappear when we get there!** So we’re limited to about 3 thousandths of a degree above AZ, which still leaves us with quite a few variables to work with, however at this point enough have been eliminated that we can get a ‘pretty good estimate’ which isn’t exact, but hell, it’s pretty good. Of course, measuring the P/V of a particle at near AZ is pointless, why would you need to?*** This would also apply, then, at AO, because every variable is at or approaching AO, which means we know all of them and then measuring them becomes unnecessary. However, at this point, we don’t know what AO is.
–Tim
*Absolute One being the highest possible value of every variable acting on a particle. The ‘opposite’ of AZ, if you will humor me.
**My speculation on this is that once all the particle’s variables are zeroed out, the particle can no longer exist. It has no characteristics! How could it?
***Of course, at this low of a temperature, the variables are all so near zero that they become quite similar, in fact, if you look at a spectrograph of the atoms in question, their characteristics are so close as to be completely indistinguishable from each other. And this is millions of atoms we’re talking about!
killall -HUP gravitywaved
PLD, Pleonast… a million thank-yous for the updated info. I’ll add it to my personal knowledge vaults for later use (probably when the info will be out-of-date again… :D).