Einsteins last theory

[pgrmdave]

Maybe then I don't fully understand what the uncertainty principle is about. I understand it to be derived from the fact that any information that we can gather about a particle must come in the form of energy bounced off of it, which, in striking it, alters it in such a way that we can either know its position or velocity, but the energy required for either is mutually exclusive - i.e. we couldn't use the same energy to determine its velocity and position at the same time. Is this correct?

[Thelonious]

Is this correct?

 

Yes, the higher the energy you use to bounce something off a particle, the more you alter its velocity and the less energy you use the less you know about its position.

[TeleMad]

Maybe then I don't fully understand what the uncertainty principle is about. I understand it to be derived from the fact that any information that we can gather about a particle must come in the form of energy bounced off of it, which, in striking it, alters it in such a way that we can either know its position or velocity, but the energy required for either is mutually exclusive - i.e. we couldn't use the same energy to determine its velocity and position at the same time. Is this correct?

 

No, this is not correct. This is just the way the principle is usually explained. The uncertainty principle is not restricted to how the measurement is made: it is a basic fact of the way nature works at the quantum level.

[lindagarrette]

It's my understanding that at the quantum level, particles don't have a velocity. They jump from one energy level to another. So time is not a factor. I assume that's why we can't measure momentum when we identify the location of the particle. (There is none.) Am I even close?

[Thelonious]

It's my understanding that at the quantum level, particles don't have a velocity. They jump from one energy level to another. So time is not a factor. I assume that's why we can't measure momentum when we identify the location of the particle. (There is none.) Am I even close?

 

Particles DO have position and they DO have velocity. However, their movement is bound by probability.

[maddog]

Einsteins last theory was to prove the existance in a God (in a creator of some form)...

As others said here you are mixing your quotes. Einstein was working to unify (at first

both EM and Gravity, aka Kaluza-Klein theory). He despised QM whereupon he did make

a quote, "God does not play dice with universe", in respect to Heisenbergs Uncertaincy

Principle.

 

Maddog

[TeleMad]

Particles DO have position and they DO have velocity. However, their movement is bound by probability.

 

Can you provide support?

[Buffy]

Particles DO have position and they DO have velocity. However, their movement is bound by probability.

Can you provide support?

To clarify, Heisenberg said you can measure the position or the momentum of a particle but not both simultaneously. With electrons, you can make statements about them being in a specific "shell" surrounding a nucleus of an atom, but not say exactly where it is in that shell.

 

Cheers,

Buffy

[pgrmdave]

With electrons, you can make statements about them being in a specific "shell" surrounding a nucleus of an atom, but not say exactly where it is in that shell.

 

If I ask 'why not?', would the answer be too technical for me to understand? I haven't really been able to grasp the idea of quantum physics, but I think that may be because I don't understand why classical physics don't work at a quantum level. Do particles exists like you and I exist?

[Buffy]

If I ask 'why not?', would the answer be too technical for me to understand? I haven't really been able to grasp the idea of quantum physics, but I think that may be because I don't understand why classical physics don't work at a quantum level. Do particles exists like you and I exist?

Don't feel bad! Feynman and others have said: "If you think you understand quantum mechanics, you most definitely don't." It makes no sense at all, and Einstein spent most of his life trying to explain it away. The key element of Heisenberg is that particles at this scale behave "strangely" and if you do experiments that for example try to fix the position of a particle, the act of measurement will actually affect the velocity (and vice versa). Thus we can only say that if we know the velocity of an electron (which is actually dictated by which shell of the atom it is in) we can't possibly figure out where in that shell it is. The shell is just a "cloud" of the electrons at that energy state. Similarly if we try to fix the position, it will start to affect the energy state of the electron and it may bounce up or down into a different shell with a different momentum. This "inability to measure" can get misused, as you'll see in a different thread over in the Philosophy of Science....

 

That's about as colloquial as you can get on this topic, and I'll still get thrashed by the physicists for over simplifying...

 

My other favorite in trying to explain this quantum stuff is Schrodingers Cat (who Hawking always has said he wants to shoot--the cat, not Schrodinger), which you should look up, because its weird but it shows "quantum effects at normal scales", start here: http://en.wikipedia.org/wiki/Schrodingers_cat

 

Cheers,

Buffy

[pgrmdave]

I've read a little about Schrodinger's Cat before, although I took it as Schrodinger meant it, that Quantum Physics is incomplete. I remember stumbling across a similar impossible possibility when I searched for Schrodinger's Cat - the immortal scientist. It shows how, if, as some people suggest, different universes, or timelines, are created for every possibility, then somewhere/time a scientist cannot be killed by bullets. It starts off with a scientist deciding to test the lethality of a gun, so he shoots himself in the chest. Most of the timelines' scientist would die, but a few survive. The survivors test it again, to be sure of the results, and once again, a few survive, but most die. These scientists perform the test again, and again, and after a thousand tests, at least one of them has survived, and concludes that he is immortal.

[Buffy]

I've read a little about Schrodinger's Cat before, although I took it as Schrodinger meant it, that Quantum Physics is incomplete.

Actually, what he meant was that it was incomplete when you tried to apply it to the macroscopic world: No, a cat can't be "half-dead." But...

It shows how, if, as some people suggest, different universes, or timelines, are created for every possibility...

This is the "many-universes" theory (completely different from the "multiverse" theory of Andre Linde that I posted elsewhere)), and its shown up a lot in popular culture, like the finale of Star Trek:TNG. The notion is that *every* different decision/event can be represented in a different universe, not necessarily *created* but the possible combination is accounted for in a different universe, so the scenario you map out is uh, probably not one you actually want to *test.* Scientific American had an article in the last year (sorry too lazy to look it up right now) that talked about how much space would be taken up by all of the possible combinations of every particle in the universe, and its a humonguous number, but facinating to thing that its *finite*....

 

Cheers,

Buffy

[maddog]

It's my understanding that at the quantum level, particles don't have a velocity. They jump from one energy level to another. So time is not a factor. I assume that's why we can't measure momentum when we identify the location of the particle. (There is none.) Am I even close?

To clarify...

 

In QM the Heisenberg Uncertaincy Principle (HUP) has two derivations: one with

Momentum and Position and second with Energy and Time.

 

Let hbar = h/2*pi then

 

hbar / 2 <= ?x ?p = ?E ?t where

 

?x, ?p, ?E, ?t are the standard deviation for position, momentum, energy, time.

 

Maddog