The double slit experiment explained.

Rkolter · Post by **Rkolter** » Tue Nov 14, 2006 8:54 am

Woah. This is really, really well done. Apparently it's been out there for awhile, but I just now found it.

http://video.google.com/videoplay?docid ... &q=quantum

This is definately going on my list of links for the science-lover.

Warren · Post by **Warren** » Tue Nov 14, 2006 9:12 am

Nifty! And yet the best explaination I've seen.

Not that I understand it that much, but cool to visualize...

Black Sparrow · Post by **Black Sparrow** » Tue Nov 14, 2006 9:15 am

Hey, that was so simply put that even I could understand it.

And whoa... weird.

ChibiJess · Post by **ChibiJess** » Tue Nov 14, 2006 9:24 am

That's just amazing. I've never heard it explained fully - just my friends chattering off stuff that goes right over my head. But that actually made sense. Is this anything like Shrodinger's cat? You observe it and change it because you are acknowledging that something has the potential to happen? Or is that something completely different?

Rkolter · Post by **Rkolter** » Tue Nov 14, 2006 9:35 am

Schroedinger's Cat is a simplified explanation of the double-slit experiment.

ChibiJess · Post by **ChibiJess** » Tue Nov 14, 2006 9:49 am

rkolter wrote:Schroedinger's Cat is a simplified explanation of the double-slit experiment.

Oooh - ok

Thanks for clearing that up

Guildmaster Van · Post by **Guildmaster Van** » Tue Nov 14, 2006 9:49 am

Up in the sky! It's a bird, it's a plane!
NO! It's Quantum Physics Man!

Terotrous · Post by **Terotrous** » Tue Nov 14, 2006 10:25 am

Quantum Physics Man would probably want you to refrain from looking up at him lest you interfere with his work.

Rkolter · Post by **Rkolter** » Tue Nov 14, 2006 10:37 am

He'd probably say things like, "Don't Pigeonhole me!"

... wait for it...

Escushion · Post by **Escushion** » Tue Nov 14, 2006 10:57 am

Haha, I enjoyed that video. Very nice stuff.

MixedMyth · Post by **MixedMyth** » Tue Nov 14, 2006 3:04 pm

Terotrous wrote:Quantum Physics Man would probably want you to refrain from looking up at him lest you interfere with his work.

Wow! It's just like government!

[AOD] · Post by **[AOD]** » Tue Nov 14, 2006 3:33 pm

Holy wow! -- What the bleep!

Actually, I pretty much understood this before I viewed it, but this video made it soooo much fun! At the end I almost (almost) wanted to become a quantum physicist myself! Wow. Man!

But HOW did the observer collapse the wave function?

I recall reading somewhere that electrons were measured by bouncing photons (X-rays?) off of them. Was this what caused the electrons to behave like particles, rather than waves?

?~AOD

Joel Fagin · Post by **Joel Fagin** » Tue Nov 14, 2006 4:05 pm

Hm... So if a tree falls in a forest and there's no one to see it, is it a wave or a particle?

- Joel Fagin

Rkolter · Post by **Rkolter** » Tue Nov 14, 2006 6:11 pm

[AOD] wrote:Holy wow! -- What the bleep!

Actually, I pretty much understood this before I viewed it, but this video made it soooo much fun! At the end I almost (almost) wanted to become a quantum physicist myself! Wow. Man!

But HOW did the observer collapse the wave function??~AOD

NOW you want to be a quantum physicist.

We don't know why. There are a lot of things we don't know the why for. Basic things. Things you take for granted every single day.

Science rocks. Welcome to the dark side.

Joel Fagin · Post by **Joel Fagin** » Tue Nov 14, 2006 6:13 pm

MixedMyth wrote:
Terotrous wrote:Quantum Physics Man would probably want you to refrain from looking up at him lest you interfere with his work.
Wow! It's just like government!

The Government doesn't want you to look up to them? That explains a lot...

- Joel Fagin

Nomadic Phoenix · Post by **Nomadic Phoenix** » Tue Nov 14, 2006 9:58 pm

[AOD] wrote:But HOW did the observer collapse the wave function?

I recall reading somewhere that electrons were measured by bouncing photons (X-rays?) off of them. Was this what caused the electrons to behave like particles, rather than waves?

?~AOD

I might be wrong on this one, but I'm going to give it a shot anyways.

In order to observe something, you have to see it. All sight is is the reflection of light off an object into a recieving device (which most of the time is the eye). Now, in order to observe the electrons passing through the two slits, they had to bounce photons (quantized packets of energy we know as light) off the electron. Since an electon acts as a wave as well as a particle, the photon threw off the wave pattern of the electron and changed its properties so that it only went through one slit and acted like matter and less like a wave.

However, when they were not observing the electron, it ended up showing interference patterns since there were no photons striking the electron and throwing it off.

That relates to Heisenberg's uncertainty principle which says that it is impossible to know the velocity and the position of a particle at any given moment at the same time. Calculating the position would require bouncing a photon off it, changing the velocity. Calculating the velocity would alter it, making the position impossible to determine.

Sorry for all of the science...I couldn't help but answer the question.

As for the video, that's the best explanation I've seen yet...and the most entertaining!

[AOD] · Post by **[AOD]** » Tue Nov 14, 2006 10:10 pm

I found something else out about my own question (heh) on Wikipedia.

It seems that, since having a detector means that you'd have to interfere with the --uhh -- interference, elsewise you wouldn't detect anything since the electron wouldn't interact with your detector, at the moment at which the electron supposedly 'splits' into two particles, one of the 'virtual' particles is apparently observed (or 'absorbed', in a sense) by the detector, leaving only one 'real' particle to impact the screen, thus "collapsing the wave function", which is why the electrons in this case behave like particles -- their wave-nature has been restricted such that they are forced into behaving like particles.

...

At least, that's the gist of it, I suppose.

Actually, it's because of wierdness like this that I prefer atmospheric physics. Give me all the chaos theory, fluid dynamics and turbulence you like, but as long as the atmosphere behaves like a nice, Newtonian fluid, I won't have to worry about particles being waves and occupying an infinite number of states all at the same time. That's a leeetle bit more wierdness than I can take, howsoevermuch I may enjoy the concept being explained by the fun science man.

rkolter wrote:NOW you want to be a quantum physicist.

If I weren't so devoted to atmospheric science, I think that I would have to start having my meteorology girls undress to the dull rhythm of the vibrations of superstrings, whilst explaining the Heisenberg Uncertainty Principle in a low, sultry voice.

@~AOD

Dracomax · Post by **Dracomax** » Tue Nov 14, 2006 10:16 pm

I know it's mostly disproven(or just regarded as plain nuts) but I still like the "it's interference from an alternat universe's electron where the same experiment is occuring" explanation. It's more fun in a Sliders kind of way.

And wouldn't photons be striking the electron anyway? Or did they not mention that they kept the room completely free of anything capable of causing electromagnetic interference, such as light, non-essential and/or unshielded electronics, etc.?

[AOD] · Post by **[AOD]** » Tue Nov 14, 2006 10:19 pm

Technically, draco, they'd have to keep the room clean of EVERYTHING, since all matter that's not at absolute zero is continuously giving off radiation, and spontaneously decaying for no good reason and suchlike.

@~AOD

Dracomax · Post by **Dracomax** » Tue Nov 14, 2006 10:38 pm

[AOD] wrote:Technically, draco, they'd have to keep the room clean of EVERYTHING, since all matter that's not at absolute zero is continuously giving off radiation, and spontaneously decaying for no good reason and suchlike.

@~AOD

that's what I thought, but you can't exactly construct an experiment in that level of "clean."

Which is what makes working with electrons so frustrating. literally everything can make them behave randomly, and one of the best way we have to measure them is to use electron microscopes. SO, by definition, we are trying to measure electrons position and speed and whatever, by either sending electromagnetic waves at it, which will tend to give it a charge, and could logically throw off readings because of magnetic attracion caused by induced fields, or we shoot an electron at it, altering it's speed, position, and generally not being a good method.(it's like trying to measure a beach ball by shooting beach balls at it).

SO, I don't see how observing an electron could possibly not effect it, regardless of how it is measured.

but, feel free to correct me if I'm wrong. Only way I'll learn.