What's the name of the theory....

[KTsRidin]

Okay, so I'm trying to explain to my SO the theory that states (paraphrase), "by studying something you alter it." But, I can't remember the name of the concept. And,... it's driving me nutz (yes, yes, I know... it's not a long drive).

 

So, all you people who are 'brainiacs' pipe up. Poor Jennifer got such a basic scientific training that she said she's never even heard of Occam's (Ockham's) Razor! There has to be a simple explanation.

 

Thanks oh great thinkers!

[YesMan]

Not sure what the name of the theory is, but I know it's a fact in the dealership.

 

I studied the RT, and then changed its home!

[KMG_365]

Hi KT!!

 

I'm no great thinker, but I seem to recall that when quantum physicists were trying to find the precise locations of electrons orbiting the nucleus of an atom they found that no matter where they looked--there they were! It turns out that certain types of energy have both particle-like and wave-like properties when you start dissecting them. The act of trying to pinpoint their exact location actually had an effect on their location!

 

It turned out that they could only estimate that certain probable number of electrons would be found within certain areas with a certain degree of probability a certain amount of the time! This was the famous "Heisenberg uncertainty principle" (or a rough approximation thereof), that I think is related to what you're looking for. You might throw that term into your Google search to get closer.

 

Even the Warp Drive engines on Star Trek's Starships have "Heisenberg Compensators" built in to make up for this little anomaly!

 

The other experiment I really thought was fascinating was if you shine a regular light through two slits in a piece of paper the light cast on the wall will show a diffraction pattern of lines as the wave-like properties of the two slits of light interfere with each other on the other side and cause bright lines and dark lines. If you shoot single very narrow beams of electrons straight through a single slit in the paper you get a solid pattern on the wall--BUT--if you open the second second slit--even if NONE of the beam is directed through the second slit--you'll get the diffraction pattern again!

 

Question is: How does the electron beam "KNOW" that the other slit is open if none of its electrons even pass through it??

 

If this intrigues you rather than bores you, there are some great books out that go into "string theory" and other breakthrough research in "Quantum Physics" that are fascinating reading. There was an older book (which is still relevant today) called the Tao of Physics which was drawing the similarities between what modern quantum physicists are now proving to be "true" about the subtle forms of matter in the the world and what the eastern "mystics" have always "known to be true". Heady stuff, but a very good read!

 

Good luck!

 

(We'll miss you guys in Death Valley this January, BTW! )

[DGuy]

Could this be it?

 

http://www.aip.org/history/heisenberg/

[fanosix]

http://en.wikipedia.org/wiki/Observer_effect

 

also known as the Heisenberg effect

[BUSTED]

I think this was discussed/explained by Buckaroo Bonzai!

[DavidEBSmith]

Wherever you go, there you are.

[RFW]

It's a result of Heisenberg's Uncertainty Principle.

 

Fortunately, it only works at a subatomic level.

 

Reminds me of a sign at in the Physics building in the University of BC here, which stated:

 

"HEISENBERG MAY HAVE SLEPT HERE".

 

Bob.

[KTsRidin]

It is with certainty that I can say, "You guys are TOOOOO funny!"

 

Thanks

[rfc1992]

Heisenberg's Uncertainty Principle works at the Macro and Microscopic Levels. The Macro effects are washed out (leaving us Newtonian Physics, due to Planck's Constant being so small (Planck's constant = 6.626068 × 10-34 m2 kg / s).

 

This means that the uncertainty level of position vs. speed is very small for massive objects.

 

I do however want to ask a LEO if he knows exactly where I was when he clocked me. If he answers yes, then he doesn't know how fast I was going.

 

A better argument would be to concede that he knows how fast I was going and then say I could be out of his jurisdiction.

 

I see a night-stick over my head in the future.

[RFW]

Heisenberg's Uncertainty Principle works at the Macro and Microscopic Levels.

 

Yes, agreed. I didn't mean it doesn't work at the macro level, only that its affects are not normally noticeable.

 

Bob.

[DogGone]

Are you thinking of Schroedinger's Cat?

 

"A cat is placed in a box, together with a radioactive atom. If the atom decays, and the geiger-counter detects an alpha particle, the hammer hits a flask of prussic acid (HCN), killing the cat. The paradox lies in the clever coupling of quantum and classical domains. Before the observer opens the box, the cat's fate is tied to the wave function of the atom, which is itself in a superposition of decayed and undecayed states. Thus, said Schroedinger, the cat must itself be in a superposition of dead and alive states before the observer opens the box, ``observes'' the cat, and ``collapses'' it's wave function. "

[Bob Palin]

The other experiment I really thought was fascinating was if you shine a regular light through two slits in a piece of paper the light cast on the wall will show a diffraction pattern of lines as the wave-like properties of the two slits of light interfere with each other on the other side and cause bright lines and dark lines. If you shoot single very narrow beams of electrons straight through a single slit in the paper you get a solid pattern on the wall--BUT--if you open the second second slit--even if NONE of the beam is directed through the second slit--you'll get the diffraction pattern again!

 

Question is: How does the electron beam "KNOW" that the other slit is open if none of its electrons even pass through it??

I remember doing that experiment in physics class, it still annoys me that I don't understand it. Can anybody point to an at least semi-laymen's explanation or tell me what the effect is called so I can look it up? (Physics class was a long time ago!) btw - wouldn't it be photons passing through not electrons?

[rfc1992]

You are referring to a diffraction grating...

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/grating.html

 

This works for quantum particles, electrons and photons.

 

The equations are self expanatory (iff this is a refresher). If not, well...

[BobFV1]

Okay, so I'm trying to explain to my SO the theory that states (paraphrase), "by studying something you alter it."

 

Not sure what theory you are referring to here, although it strikes me more as something from CSI than from quantum physics. I did take a class in molecular structure way back in college and I remember specifically looking at how Heisenberg's principle was applied to understanding molecular structure. But I don't see how position and momentum relate to something changing by studying it

[Bob Palin]

You are referring to a diffraction grating...

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/grating.html

 

This works for quantum particles, electrons and photons.

 

The equations are self expanatory (iff this is a refresher). If not, well...

Well OK, maybe if I studied that I would understand the equations again, but my real quandry is the case Jamie described where "particles" pass only through one of two slits but display the diffraction pattern for two slits. (Maybe that's explained by the web site but I couldn't see that case drawn out)

[rfc1992]

Okay... (knuckles cracking) From Concepts of Modern Physics, 4th Edition by Arthur Beiser...

 

"To regard a moving particle as a wave group implies that there are fundmental limits to the accuracy with which we can measure such "particle" properties as position and momentum."

 

Mass has both wave and particle characteristics. The Photon moves as a wave (think wavelength of light) as it passes through a prism or diffraction grating. The particle activity of the photon is that it has momentum (think solar sail or the light-bulb-thingy with the black and white diamonds in the center that rotated).

 

To describe (know) the position of a mass element and its momentum (mass*Velocity) we have limits.

 

First, to find a particle we must find the Probability Density, |(PSI)|^2. The maximum of |(PSI)|^2 in the middle of a gorup of particles, so it is most likely to be found there. The particle can exist anywhere |(PSI)|^2 <> 0.

 

The narrower the wave group, the more precisely a particle's position can be specified. However, the wavelength of the waves in a narrow packet is not well defined: there are not enough waves to measure (LAMBDA) {wavelength} accurately.

 

Picture a sine wave. The wider your picture, the more accurate your measurement of the wavelength. Now zoom in on the upward slope so all you see is a line - what is the wavelength? It is difficult to determine.

 

(LAMBDA) = h/mv where h is Plank's Constant, m is mass, and v is velocity. mv = p where p is the momentum.

 

If (LAMBDA) is not known, then neither is p.

 

delta k is the spread of wave numbers that correspond to the motion of your particle.

delta x is the area of interest (the distance that you zoomed out/in to to determine your wavelength)

 

delta x * delta k >= 0.5

 

(LAMBDA) = h/p

k = 2pi/(LAMBDA) = 2pi * p / h

 

solve for p then

 

delta p = h * delta k / 2pi

 

therefore...

 

delta x * delta p >= h/4pi

 

The product of uncertainty in position and uncertanty in momentum is greater than or equal to Plank's Constant / 4pi.

 

If you know exactly the position (delta x = 0) then delta p goes to infinity. This means you have no idea what the momentum (mass * velocity) is.

 

Conversely, if you know the mass and velocity, you have no clue as to the position.

 

Thankfully, Plank's Constant is 6.626 x 10^-34 Joule-seconds or very very small.

 

The impact on your knowing where you and your motorcycle are, and their associated mass and velocity, is negligible.

 

I skipped some Fourier integrals, but the concept is the same. You cannot know simultaneously the position and momentum of a particle. By derivation, you cannot know simultaneously the position, velocity, and mass of a particle.

[rfc1992]

The particles move as waves. It is the superposition of these waves upon each other than creates the interference patterns. One photon would make a single dot, or not, on the screen. Many of them would superimpose or interfere with one another.

 

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/dslit.html#c1

 

A single photon will either strike the screen or go through. Two photons may each go through the grate, but be 180deg out of phase with one another and cancel each other out.

[sgendler]

I remember doing that experiment in physics class, it still annoys me that I don't understand it. Can anybody point to an at least semi-laymen's explanation or tell me what the effect is called so I can look it up?

 

 

Yep - Check out The Elegant Universe' by Brian Greene, which gives a beautiful lay discussion of subatomic physics. I thoroughly enjoyed the book.

 

For another excellent layperson discussion of important physics concepts, check out E=MC^2, which gives an in-depth description of what Einstein's famous formula truly means. It is well worth the read.

 

--sam

[sgendler]

Well OK, maybe if I studied that I would understand the equations again, but my real quandry is the case Jamie described where "particles" pass only through one of two slits but display the diffraction pattern for two slits. (Maybe that's explained by the web site but I couldn't see that case drawn out)

 

Bob, check out the first book I referenced above. It will do a great job of explaining the particle/wave thing with photons without resorting to mathematical formulas, and it goes a long way toward explaining the physical mechanism of the effect via superstring theory. I doubt you'll find a better explanation outside of a physics text, and that would require heavy math.

 

--sam

[Mark Menard (Vita Rara)]

Yep - Check out The Elegant Universe' by Brian Greene,

 

I'll second the recomendation for "The Elegant Universe," as well as Brian Greene's next book, "The Fabric of the Cosmos." He goes over some of the same ground in the second book, but expands tremendously on the more advanced concepts with the new research that occured between the first and second book. Greene is consumately readable. Possibly the best expositor of advanced concepts in physics for the lay community.

 

Mark

[KTsRidin]

Oh my, but there sure are a bunch of egg-headed nerds on the DB Geez, I love you guys!

I swear I learn more here than I ever did in school sometimes.

 

Keep 'em coming - while trying to read some of your posts to me SO she interupted me and stated, "You know I don't find this interesting in the least." Of course there was a fun tone in her voice, but you can see why I love you guys and my SO too.

 

Cheers!

[Whip]

They're not "a bunch of egg-headed nerds" they're a bunch of mad scientist......

[rfc1992]

I keep opening boxes just to make sure that cat of Schroedinger's is dead.

 

Bumper Sticker: Ask Me About Microwaving Cats For Fun and Profit!

 

I don't know if I qualify as an egghead, nerd, or mad scientist. Perhaps a bit of all three. One thing is for certain though, I have a cool motorcycle.

[Bob Palin]

Yep - Check out The Elegant Universe' by Brian Greene, which gives a beautiful lay discussion of subatomic physics. I thoroughly enjoyed the book.

Thanks guys, Brian Greene did a 3 episode Nova version of his book which is available on DVD, I think I will start with that.

[sgendler]

I don't know if I qualify as an egghead, nerd, or mad scientist. Perhaps a bit of all three. One thing is for certain though, I have a cool motorcycle.

 

When you name yourself after an internet RFC, I think you qualify as a nerd, especially when it is the RFC for the 'Nimrod Routing Architecture.'

 

--sam

[rfc1992]

I know nothing of what you speak. My initials are R.F.C. 1992 is the year I graduated from the University of Cincinnati.

[BUSTED]

Is the 13 story erection known as Calhoun dorm still there?

 

 

 

Eeebie had the correct quote from Buckaroo, who was quoting Confucius!

[sgendler]

I know nothing of what you speak. My initials are R.F.C. 1992 is the year I graduated from the University of Cincinnati.

 

OK, you're excused from nerd-dom, and I'm clearly a lelever or 2 deeper into it than I thought.

 

--sam

[Bob Palin]

OK, you're excused from nerd-dom, and I'm clearly a lelever or 2 deeper into it than I thought.

 

--sam

Ouch, if we can believe him I'm a level deeper than I thought too, I saw rfc and thought Request For Comment. I think he changed his name just to get those initials

[RFW]

Can anybody point to an at least semi-laymen's explanation or tell me what the effect is called so I can look it up? (Physics class was a long time ago!) btw - wouldn't it be photons passing through not electrons?

 

First, yes it is photons, not electrons. But it will work with electrons too.

 

Second, there is a 3-part lecture series on the web at....

 

http://www.vega.org.uk/video/subseries/8

 

... where the speaker is none other than RICHARD FEYNMAN himself!!!

 

He addresses this subject and others, in this lecture on Quantum Electrodynamics.

 

Before you turn off completely (!) I should point out that this lecture series is REALLY entertaining as well. Not only was Feynman a total genius, it is generally agreed that he was the best scientific lecturer that has ever lived. And, he had a totally weird sense of humour. To watch him, is something not to be missed!!

 

To answer your basic question on how diffraction through the 2 slits can possibly occur when shooting only one photon at at time, the reason is that (as Feynman says) "Mother nature plays the odds". In other words even at this basic level, things work by probability.

 

But DO have a look at the lecture!! At least the first half of the first one. Not only is it hillarious at times, he can actually EXPLAIN things!

 

Bob.

[rfc1992]

Calhoun: I believe it is still there.

 

 

 

The stench as well.

[DogGone]

Great!,

 

You guys got me curious about the book "The Elegant Universe" so I checked it out of the ocal library today. I'm sitting here reading it and I come to the part about the constancy of the speed of light where they use the example of a person firing a laser at you, and you turning to run from it.

 

I've always heard the constancy of the speed of light applied to the speed of the SOURCE of the light. But never thought about it from the observer's point of view.

 

In the example, the laser is fired at you, the light is moving towards you at 670 million mph and you turn and run away from it at 100 million mph. You would think tht the speed of light relative to you would be 570 million mph but no, the book says it is still moving at 670 million mph relative to you. It's also moving at 670 million mph relative to the shooter. So, this seems to imply that the light "knows" how fast you are moving.

 

And how can the light be moving at two speeds? it's moving at 670 million mph according to the shooter, but it's moving at 770 million mph from the target's point of view.

 

I just put a pot of coffee on, it's gonna be a long night.

 

Thanks a lot!

pete

[KMG_365]

Great!,

 

You guys got me curious about the book "The Elegant Universe" so I checked it out of the ocal library today. I'm sitting here reading it and I come to the part about the constancy of the speed of light where they use the example of a person firing a laser at you, and you turning to run from it.

 

I've always heard the constancy of the speed of light applied to the speed of the SOURCE of the light. But never thought about it from the observer's point of view.

 

In the example, the laser is fired at you, the light is moving towards you at 670 million mph and you turn and run away from it at 100 million mph. You would think tht the speed of light relative to you would be 570 million mph but no, the book says it is still moving at 670 million mph relative to you. It's also moving at 670 million mph relative to the shooter. So, this seems to imply that the light "knows" how fast you are moving.

 

And how can the light be moving at two speeds? it's moving at 670 million mph according to the shooter, but it's moving at 770 million mph from the target's point of view.

 

I just put a pot of coffee on, it's gonna be a long night.

 

Thanks a lot!

pete

 

I'm sure they talk like this on the Harley and Yamaha boards as well!

 

I'm NOT alone after all!

 

God, I love you guys!

[RFW]

I'm sure they talk like this on the Harley and Yamaha boards as well!

 

I'm NOT alone after all!

 

I think that Relativity or Quantum Electrodynamics tends to be more of a useful subject on this "BMW" board, because BMWs (especially the new K-S) are just so fast, that relativistic effects need to be taken into account to ride them.

 

Yeah, right!

 

Bob.

[BobFV1]

I'm sure they talk like this on the Harley and Yamaha boards as well!

 

I'm NOT alone after all!

 

I think that Relativity or Quantum Electrodynamics tends to be more of a useful subject on this "BMW" board, because BMWs (especially the new K-S) are just so fast, that relativistic effects need to be taken into account to ride them.

 

Yeah, right!

 

Bob.

 

My Yamaha is faster than any stock BMW. And I can confirm - nothing like this is posted on the R1 board. And the average avatar on the R1 board would be deleted by mods on this board...

[Bob Palin]

I'm NOT alone after all!

Sadly you're not - today's physics lesson:

 

Two hydrogen atoms walk into a bar.

One says, "I've lost my electron."

"Are you sure?"

The first replies, "Yes, I'm positive..."

[KMG_365]

That's too funny!!!

 

Here's some more for you:

 

------------------

 

"I do not know what is wrong with Heisenberg. He seems so sure of himself

lately."

 

-- Sydney Harris Cartoon

 

--------------------

 

"Wanted, dead or alive : Schrödinger's cat."

 

--------------------

 

The Two Cat Experiment

 

A panel with two slits is set up in front of a measuring device--a cat scanner.

 

When numerous cats are fired at the panel, the scanner measures the expected interference pattern. But, when a single cat is fired through a single slit, the cat doesn't know if it's alive or dead.

 

----------------------

 

"Wanted, Dead AND Alive: Schrödinger's Cat."

 

----------------------

 

Historians have concluded that W.Heisenberg must have been contemplating his love life when he discovered the Uncertainty Principle:

 

-When he had the time, he didn't have the energy . . .

 

and,

 

-When the moment was right, he couldn't figure out the position...

 

--------------------------

 

"Wanted, |dead>, |alive> or 1/sqrt(2)(|dead> + |alive>): Schrödinger's cat."

 

-------------------------

 

Heisenberg is having a roadside interview with a LEO who asks: "Do you know how fast

you were going?"

 

Heisenberg replies: "No, but I know exactly where I am!"

 

-------------------------

 

Curiosity *may* have killed Schrödinger's cat.

 

-------------------------

 

Q: What's the difference between a quantum mechanic and an auto mechanic?

 

A: A quantum mechanic can get his car into the garage without opening the door.

 

------------------------------------------------

 

The Heineken Uncertainty Principle:

 

You can never be sure how many beers you had last night.

 

------------------------------

 

News Bulletin:

 

Earlier today Dr. Heisenberg stated unequivocally that he may or may not have been responsible for the Uncertainty Principle.

 

-----------------------------

 

Einstein walks into a bar and says to the bartender, "I'll take a beer, and a beer for my friend, Heisenberg."

 

The bartender looks around and asks, "Is your friend here?"

 

"Well," says Einstein, "he is and he isn't."

 

----------------------

 

Q: What is the definition of a tachyon?

 

A: It's a gluon that's not completely dry.

 

--------------------------------

 

I have a "quantum motorcycle". Every time I look at the speedometer I get lost . . . .

[KTsRidin]

Ohh, I just spit my beer reading this, but I don't know how fast I was, but I sure know where I've got to clean

 

Alas, my SO once again sat through me laughing and not quite getting there with me when I read a few choice ones.

 

THANKS

[rfc1992]

Theory of Relativity: The richer you are, the more relatives you have.

 

---------------

 

If you are travelling at the speed of light, how do you know when to turn?

 

---------------

I drove fast through a toll booth and might have changed lanes.

 

---------------

I am not overweight, I just move too fast.

[Ken H.]

One down a few notches from "The Elegant Universe," but no less entertaining, is Ian Marshall and Dahah Zohar's "Who's Afraid of Schrödinger’s Cat?”

[Joe Frickin' Friday]

Somewhere on the web there was a place that noted "on this day in history" events. For the anniversary of Heisenberg's death, the note simply said:

 

"Heisenberg may have died today."

[Couchrocket]

"Mother nature plays the odds".

In a book by Gerald Schroeder, he speculates that the ultimate substrate of the universe may be "information" and even "wisdom."

[DGuy]

"Mother nature plays the odds".

In a book by Gerald Schroeder, he speculates that the ultimate substrate of the universe may be "information" and even "wisdom."

 

Shall we start discussing Bell's Theorem? I find that to be absolutely mind bogling.

[Bob Palin]

Shall we start discussing Bell's Theorem? I find that to be absolutely mind bogling.

Bell's Theorem: If you are down the pub and just before closing time decide to have another shot of Bell's whisky, your wife will know about it instantly...

[BeemerBerg]

But....

 

If a man standing in the middle of the woods says something, and there's no woman around, is he still wrong?

 

Oh, life's little mysteries

[KTsRidin]

That's simple......

 

 

 

 

 

 

 

 

 

 

 

 

YES

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Just kidding - or am I