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afterburner
2006-Jul-15, 01:22 AM
In one of Isaac Asimov's books, he mentioned that ALL mater can behave like a wave, as well as a particle. He went on further to say that we observe wave-like behaviour in electrons (which is technically matter) because they are made of very litle matter, and therefore we can observe its wave-like properties.

My question is...
1. If we do the double slit experiment, firing objects the size of Earth, would we observe the wave-like behaviour? The answer seems yes, since ALL matter behaves like a wave, however

2. What would the scale have to be, in order for us to observe the wave-like behaviour in the experiment that I proposed?

3. Would the wave-like behaviour be because of gravity? or some other "force", or something entirely different?

4. And finally...What would this look like for the people on these planets(assuming they had really advanced telescopes observing the experiment? (I feel as if they are NOT going to say the Earths/Planets are in TWO places at the same time, but i could be wrong...)

Ken G
2006-Jul-15, 03:00 AM
1. If we do the double slit experiment, firing objects the size of Earth, would we observe the wave-like behaviour? The answer seems yes, since ALL matter behaves like a wave, however
All matter does behave like a wave, it's the way the universe works. But the wavelength of that wave would be far too small to be able to resolve any fringelike behavior. There is simply no way to get interference effects from huge amounts of matter, so the wavelike nature is irrelevant and trajectory models work fine. (That's why the trajectory model was created long before wave mechanics, even though it is always an idealization of very short wavelength wave mechanics).

2. What would the scale have to be, in order for us to observe the wave-like behaviour in the experiment that I proposed?
You are really thinking like a physicist here. The way to estimate the wavelength is to use the "deBroglie wavelength", which is Planck's (tiny) constant h divided by the (huge) momentum of the Earth as it impinges on your "slits". The result will be mind bogglingly small, and impossible to measure.

3. Would the wave-like behaviour be because of gravity? or some other "force", or something entirely different?

The wavelike behavior is not "because" of anything, other than that this is how everything in the universe works.

4. And finally...What would this look like for the people on these planets(assuming they had really advanced telescopes observing the experiment? (I feel as if they are NOT going to say the Earths/Planets are in TWO places at the same time, but i could be wrong...)
Like the wave mechanics, the weirdness of quantum mechanics does not carry over to the huge mass of the Earth. The Heisenberg uncertainty principle says that the deBroglie wavelength is also the position uncertainty of the Earth if treated as a single object, so the scale over which it could be "in two places at the same time" is absurdly small.

Infinity Watcher
2006-Jul-15, 01:07 PM
You can actually work out the wavelength of some matter fairly simply, or at least get the De Broglie (pronounced de broy) wavelength which as I understand it amounts to pretty much the same thing, the equation is (I'm having an arguement with the posting system about putting various symbols in so these aren't quite the right symbols and wavelength is normally represented b) wavelength = h/p (the wikipedia entry here (http://en.wikipedia.org/wiki/De_Broglie_hypothesis) gives a slightly more complicated equation which I suspect is corrected for relativistic effects, but I don't know for certain, in any case at low particle velocities they give very similar answers) In the above equation h is planck's constant (6.63x10^-34 m^2 kg s^-1 according to the google calculator and rounded to 3 s.f) and p is the momentum of the particle given by mass x velocity. I've just noticed that Ken G actually covered this in his post but I don't want this post to go to waste so consider this a very long-winded way of linking to the wikipedia entry on the "De Broglie hypothesis" and to say that as ken said it is fairly obvious that as the mass of any given object increases the wavelength decreases, it also decreases with increasing velocity so for somehting like the earth it really is negligible, in short basically what Ken G said.

HenrikOlsen
2006-Jul-15, 03:15 PM
You could see this thead (http://bautforum.com/showthread.php?t=36528) and cut'n'paste from it to get the symbols:)
Take the earth, moving at 1 ms-1
λ=h/p≈6.63×10-34 m2s-1kg / (5.9742×1024 kg × 1 ms-1) = 1.1098×10-58m

So to do a doubleslit experiment with the earth, you have to push it through two slits ~1×10-58m wide.
It's going to be a very strange experience for the people living on it:)

afterburner
2006-Jul-15, 11:50 PM
1.1098x10^-58 huh?

Well, in that case, its not really surprising that Earth will behave likea wave. The stuff coming out the other side will most definitely NOT look like the stuff that went in, right?

WaxRubiks
2006-Jul-16, 01:39 AM
I had one of those lasers pointers a few years ago and I did the double slits experiment in the living room, and I got the correct wavelength from the measurements. I was quite impressed with myself.

clop
2006-Jul-16, 01:40 AM
You could see this thead (http://bautforum.com/showthread.php?t=36528) and cut'n'paste from it to get the symbols:)
Take the earth, moving at 1 ms-1
λ=h/p≈6.63×10-34 m2s-1kg / (5.9742×1024 kg × 1 ms-1) = 1.1098×10-58m

So to do a doubleslit experiment with the earth, you have to push it through two slits ~1×10-58m wide.
It's going to be a very strange experience for the people living on it:)

This explanation doesn't seem to have a practical application for an object like the earth. Surely this theory and these equations work only for point masses, rather than for something like the earth, which is an aggregate of masses.

The way I read your explanation it seems to make more applicable sense that if you had a point particle with a mass of 5.9742×1024 kg you would need to pass it through slits ~1×10-58m wide.

How does this theory apply to objects where the individual particles do not share a common centre.

clop

clop
2006-Jul-16, 01:42 AM
I had one of those lasers pointers a few years ago and I did the double slits experiment in the living room, and I got the correct wavelength from the measurements. I was quite impressed with myself.

How did you switch the pointer on and off quickly enough to allow only one photon to be released at a time?

clop

WaxRubiks
2006-Jul-16, 01:46 AM
How did you switch the pointer on and off quickly enough to allow only one photon to be released at a time?

clop

I used the force and a nearly dead battery.;)

Ken G
2006-Jul-16, 02:49 AM
How does this theory apply to objects where the individual particles do not share a common centre.

The point can also be stated that because the deBroglie wavelength is much smaller than the Earth itself, the constituent parts of the Earth would come into play if you tried the experiment. But since the purpose of the exercise is to show that the experiment is pointless (no pun intended), it hardly matters that our treatment of the Earth is idealized.

clop
2006-Jul-16, 03:54 AM
The point can also be stated that because the deBroglie wavelength is much smaller than the Earth itself, the constituent parts of the Earth would come into play if you tried the experiment. But since the purpose of the exercise is to show that the experiment is pointless (no pun intended), it hardly matters that our treatment of the Earth is idealized.

Of course it does. HenrikOlsen said that the earth going through the slit would be a very strange experience for the people living on it, and afterburner said that the earth would not look the same when it came out of the other side of the slit. You can't just say "assume the earth to be a single particle". The idealisation of the earth into a single particle is in conflict with the OP's seemingly macroscopic question about the earth as it really is. He asked about objects the size of the earth, not just the mass of the earth.

clop

Ken G
2006-Jul-16, 06:27 AM
I think you may have missed the humor in HenrikOlsen's and afterburner's posts.

clop
2006-Jul-16, 10:38 AM
No I didn't. I'm making a valid point. Sometimes things can't be idealised without losing the necessary conditions of the problem.

Ken G you're my idol. Duh.

clop

Ken G
2006-Jul-16, 11:29 AM
In that case, you win!

clop
2006-Jul-16, 12:23 PM
You said that in a very superficial way. You shouldn't resign your position as a result of simple flattery.

clop

Ken G
2006-Jul-16, 01:15 PM
Flattery is pretty potent, actually! But I'm not really resigning my position, as we are in agreement that the idealization of the Earth as a point particle is certainly not appropriate for discussing its wave properties. What I was saying was that if you first idealize the Earth as a single particle, you find a deBroglie wavelength that does two things: 1) it shows you can't observe it, and 2) it renders the idealization meaningless. So we are actually in agreement here, and I think HenrikOlsen and afterburner are in agreement too, they were just kidding around. I think you are saying that point (2) means there is no weight to point (1), but really the two are saying pretty much the same thing.

PhantomWolf
2006-Jul-16, 10:58 PM
I had one of those lasers pointers a few years ago and I did the double slits experiment in the living room, and I got the correct wavelength from the measurements. I was quite impressed with myself.

I've measured g using a pendulum made of paperclips and a large rubber (eraser for you US'ers) then measuring the swing period with an alarm clock. The result was spot on, though the error level was pretty big.