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#1
06-11-2001, 04:23 AM
 PerfectDark Guest Join Date: Sep 2000
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
#2
06-11-2001, 05:14 AM
 Gary Kumquat Guest Join Date: Sep 2000
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?
#3
06-11-2001, 05:31 AM
 SPOOFE Guest Join Date: Apr 2000
Quote:
 In the future won't it be possible to detect and measure gravity waves?
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...

Quote:
 Doesn't this make the Heisenberg's Uncertainty Principle and old theory?
Nope. Something doesn't become false just by saying that it might, one day, be proved false.
#4
06-11-2001, 05:42 AM
 PerfectDark Guest Join Date: Sep 2000
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
#5
06-11-2001, 05:53 AM
 scr4 Guest Join Date: Aug 1999
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.
#6
06-11-2001, 06:22 AM
 PerfectDark Guest Join Date: Sep 2000
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
#7
06-11-2001, 06:30 AM
 Gary Kumquat Guest Join Date: Sep 2000
Quote:
 Originally posted by PerfectDark 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.
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][*]approximating the position[*]approximating the veolicty[*]affecting one of the above[/list=1]
Quote:
 And what I meant was "Won't" this make the Heisenberg's Uncertainty Principle an old theory? As in once it has been accomplished.
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.
#8
06-11-2001, 08:12 AM
 pldennison Guest Join Date: Mar 1999
Quote:
Originally posted by SPOOFE
Quote:
 In the future won't it be possible to detect and measure gravity waves?
Theoretically, but I won't hold my breath...
Er . . .

http://www.gravity.pd.uwa.edu.au/

http://igec.lnl.infn.it/cgi-bin/browser.pl

http://gravity.phys.lsu.edu/
#9
06-11-2001, 08:14 AM
 Pleonast   Charter Member Join Date: Aug 1999 Location: Los Obamangeles Posts: 5,104
Quote:
 In the future won't it be possible to detect and measure gravity waves?
The future is now. Several countries are building gravitational wave detectors. The US effort is called LIGO.

Quote:
 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?
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").

Quote:
 if gravity waves exist then they will be distortions of space-time, not particles. Which I don't think comes under the uncertainty principle.
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.

Quote:
 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.
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).
#10
06-11-2001, 09:13 AM
 Alessan Guest Join Date: Jul 2000
Quote:
 Heisenberg's Uncertainty Principle, Wrong??
Maybe. Maybe not.

rimshot
#11
06-11-2001, 09:24 AM
 Gary Kumquat Guest Join Date: Sep 2000
Quote:
 Originally posted by Pleonast It's easy to measure both position and velocity. The UncPr only limits the accuracy you can measure them with.[/b]
Okay, so I should have said "measured exactly", but in fairness, I had just said that UncPR held that
Quote:
 the position and the velocity of an object cannot both be measured exactly, at the same time
But you're quite right that measuring both is easy, to certain degrees of accuracy.
#12
06-12-2001, 04:14 PM
 WarmNPrickly Member Join Date: Oct 1999 Posts: 5,439
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.
#13
06-12-2001, 04:44 PM
 Chronos Charter Member Join Date: Jan 2000 Location: The Land of Cleves Posts: 50,755
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.
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#14
06-12-2001, 05:15 PM
 Saltire Charter Member Join Date: Nov 1999 Location: Seattle, WA, USA Posts: 3,531
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.
#15
06-12-2001, 08:22 PM
 DrMatrix Charter Member Charter Member Join Date: Nov 1999 Location: New York State of Mind Posts: 3,299
Quote:
 Originally posted by PerfectDark 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.
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.
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#16
06-12-2001, 11:55 PM
 Ring Charter Member Join Date: Dec 2000 Location: South Carolina USA Posts: 1,561
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.
#17
06-13-2001, 01:10 AM
 5CentCigar Guest Join Date: Feb 2001
It depends on how you look at it.
#18
06-13-2001, 02:41 AM
 Homer Guest Join Date: Sep 1999
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!
#19
06-13-2001, 05:41 AM
 dylan_73 Guest Join Date: Aug 2000
Rubbish joke for the day

killall -HUP gravitywaved
#20
06-13-2001, 06:27 AM
 SPOOFE Guest Join Date: Apr 2000
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... ).
#21
06-13-2001, 12:14 PM
 Philbuck Guest Join Date: Apr 2000
It's worth pointing out that the Uncertainty Principle is not just postulated, and its proof is not limited to the hand-waving "if you hit a particle with a photon..." ideas with which it is usually explained. Rather, the UP is a mathematical consequence of the operator description of quantum mechanics, arising from the non-commutivity of the position and momentum operators and the mathematical descriptions of uncertainty (there are probably other proofs as well, but this is the one I'm familiar with). If a situation were found where the UP did not hold, there would have to be some rather deep flaws in the basics of quantum theory.
#22
06-13-2001, 01:36 PM
 Saltire Charter Member Join Date: Nov 1999 Location: Seattle, WA, USA Posts: 3,531
Homer, I usually talk myself out of commenting on your posts, because I really don't want to discourage you. Who knows, maybe you'll someday come up with a breakthrough insight.

However, I'm doing it now. First, many variables don't have a 'highest possible value', so your concept of Absolute One makes no sense whatsoever. Second, try to learn a bit more about the uncertainty relations.

You have made the same mistake as the OP, assuming that Heisenberg was just describing the limitations of our technology when it comes to studying particle interactions. In fact, he was showing a fundemental fact of the universe. It is the basic uncertainty of quantum physics that allows virtual particles to exist. Since these ghost particles have such a large part to play in our understanding of physics, we'd all better hope that some future gadget doesn't make the uncertainty principle go away. If it did, we'd suddenly have no idea where the basic forces of nature come from, just when we were starting to get it all nailed down.
#23
06-13-2001, 05:26 PM
 Giraffe Charter Member Charter Member Join Date: Aug 2000 Location: ♂ San Jose, CA Posts: 9,932

I think you're assigning too much importance to temperature. Particles don't lose their properties at zero temperature, they simply have no thermal kinetic energy. That's it.

However, you raise an interesting point when you say that if the particle's energy were known to be exactly zero, then that would make its velocity exactly known, giving infinite uncertainty in the position. If this were the case, as you cool to zero, your box of particles would disappear. But that's wrong. The mistake is in assuming you know that the energy of a box of particles is exactly zero at zero temperature. Actually, atoms have what is known as "zero-point energy", which is the energy associated with the uncertainty in the velocity.

Helium stays liquid even at exactly zero temperature, due to its large zero-point energy.
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#24
06-15-2001, 10:55 AM
 erislover Guest Join Date: Nov 2000
Most of what I have read implies that gravity will be adopted into a quantum framework, not the other way around. I don't think any physicists actively think that the HUP is wrong on some level, it has simply been confirmed in too many experiments.

The HUP has nothing to do with measurement.

I think the thing that is most illustrative of this are the "super atoms" that some team of scientists made (unfortunately the article was in my mother's scientific american and she live 10 hours away), otherwise known as Bose-Einstein Condensates. Supercooling atoms to just above absolute zero will indeed make their velocities(momentum) very precisely known. Their position, however, begins to be a bit murky and the effect, if it is done with a pure element, is that all the individual atoms disappear and one "large atom" is made. Others can fill in the necessary details, but the upshot is that the HUP ain't wrong.
#25
06-15-2001, 04:01 PM
 Homer Guest Join Date: Sep 1999
I'm just crazy enough to realize it.

Saltire, I appreciate your candor. However, how can we prove that there is not an absolute possible highest value for all variables? Such an idea, at this time, can only be theorized, correct? When I was speaking of Absolute Zero in the sense that reaching it removes all characteristics from a particle, I meant Absolute Zero inclusive of all known^h^h^h^h real forces, not 'just' heat energy. Such a thing would likely be found only in deep space, because we retain magnetic and gravitational influence on particulate matter here on earth. But by all means, in the future, tear my postulations to shreds. Unless I know that they are false, I cannot begin to construct true ones.

Giraffe: When cooled to as close as possible to absolute zero, particles do disappear, lending a slight credence to my posulation.
Quote:
 The condensate first shrinks as expected, but rather than gradually clumping together in a mass, there is instead a sudden explosion of atoms outward. This "explosion," which actually corresponds to a tiny amount of energy by normal standards, continues for a few thousandths of a second. Left behind is a small cold remnant condensate surrounded by the expanding gas of the explosion. About half the original atoms in the condensate seem to have vanished in that they are not seen in either the remnant or the expanding gas cloud.
http://www.nist.gov/public_affairs/releases/tn6240.htm Also interesting is their discussion of 'dark solitons', or a wave-form made up of the absence of something.

I speculate that these atoms have become removed from each variable and ceased to exist; their entirety was released in the explosion and absorbed as various energies by the measurment devices.

I cannot learn truth unless I also learn what is false. Hence, destroy my speculations so I may rebuild them correctly.

--Tim
#26
06-15-2001, 04:03 PM
 Homer Guest Join Date: Sep 1999
Also of interest:
Quote:
 The most surprising thing about the Bosenova is that the fundamental physical process behind the explosion is still a mystery.
Am I crazy, or am I completely sane and the rest of the world is nuts?

--Tim
#27
06-15-2001, 06:46 PM
 Cervaise Guest Join Date: Mar 1999
Homer: Blame it on the Bosenova.
#28
06-15-2001, 11:22 PM
 Pleonast   Charter Member Join Date: Aug 1999 Location: Los Obamangeles Posts: 5,104
From "Bosenova" (that's Homer's url)
Quote:
 The fate of the missing atoms is still an open question, but the researchers suspect that they wind up either accelerated so greatly that they escape the trap undetected, or perhaps form molecules that are invisible to the detection system.
and
Quote:
 This "explosion," which actually corresponds to a tiny amount of energy by normal standards, continues for a few thousandths of a second.
So, they don't know exactly where some of the atoms go after the explosion. But, if the atoms just "vanished", there would be more than a "tiny" amount of energy released (by Conservation of Mass-Energy).

About "zeroed-out" variables--in an atom, you can never zero these observables:
1. The variance of the position, or the variance of the momentum. Even in the lowest energy state, there is motion (as explained by Giraffe).
2. The nucleon number (count the number of protons and neutrons) is conserved. Unless you add anti-matter, nucleons are just going to vanish.
3. The lepton number (count the number of electrons) is conserved. Same thing as nucleons.

Even when an atom is in it's lowest energy state, there are still non-zero forces acting between the parts of the atom. You can't ignore these forces, and they don't ever become zero.
#29
06-15-2001, 11:32 PM
 Pleonast   Charter Member Join Date: Aug 1999 Location: Los Obamangeles Posts: 5,104
Homer, your ideas are crazy (but I'm reserving judgment on you ). However, the Absolute One idea is interesting. I've never really thought about it before in these terms, but current physics breaks down at the Planck scale. See this thread Planck length question. At some extremely high energy, the wavelength of a particle would be about the Planck length. I'm not sure what it'd mean for a particle to have a higher energy (and thus shorter wavelength). Any particle physicists want to tackle this one?
#30
06-16-2001, 02:01 AM
 Homer Guest Join Date: Sep 1999
Pleonast, if you'd like to read some of my more out-there ramblings from the height of my stoner-scientist days last semester, please read through this thread. I admit I was rather stoned during the length of it, either while thinking of the ideas or typing them. You should see the stuff I thought too crazy to submit! I've written up a lot about some stuff, and am trying to organize my thoughts on the four dimensional math model, the repeating -inf,-1...,0,1...,inf cycle, and the law of fours to demonstrate to a physics professor. He'll likely look at me funny then throw me from his office, but it's worth a try.

As for the value of AO, I think it's probably Einstein's Constant, but I can't prove it.

--Tim

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