Quantum Physics

David H wrote:

halfwise wrote:

David H wrote:
My question is, if we're thinking of waves moving through the medium of space-time in ways that can be measured by an interferometer, haven't we just made a big circle and come right back to where we were 100 years ago with Luminiferous ether?

The only way I can think of responding to that question is to say that locally you can't measure motion relative to space-time, only in comparison to warps in space-time.

I'm don't understand in this context though. The trouble I'm having is in measuring a potentially faster-than-light effect with an optical sensor. There are a lot of apparent paradoxes in faster-than-light travel that have been used to show that it's impossible (at least for undergraduates). This seems to require that they all be reexamined. But I'm trying not to speak Martian.

So let's say that the USS Enterprise is approaching Earth in a warp field at Warp 2. What happens to the light in the field? Can an observer on Earth see it? If so, what does it look like? If not, how can you measure the effect? Does Eel Oil help? How about Buckie?

This isn't an idle question you know. I'm thinking about the next Carrot Ship.

Sorry David, been out of the loop for the last week, being on vacation/conferences and stuff. I'm not sure I'm mentally equipped to explain this either, but let's give you and example to think about that may make you feel more comfortable with the idea.

You can't detect motion relative to flat space-time: postulate of relativity. You can detect motion relative to curved space-time, it feels like acceleration due to gravity. What the sensor was measuring was interference between two beams of light going through differently curved space-time: you are seeing relative accelerations manifest by phase changes in the waves.

You could perhaps relate space-time curvature to aether drag, but the difference is that the aether hypothesis would still have light travelling relative to the aether, so even away from large masses you should be able to detect relative motion, whereas in flat space-time you can't detect relative motion.

[quote="halfwise"]

David H wrote:

halfwise wrote:

David H wrote:
My question is, if we're thinking of waves moving through the medium of space-time in ways that can be measured by an interferometer, haven't we just made a big circle and come right back to where we were 100 years ago with Luminiferous ether?

The only way I can think of responding to that question is to say that locally you can't measure motion relative to space-time, only in comparison to warps in space-time.

I'm don't understand in this context though. The trouble I'm having is in measuring a potentially faster-than-light effect with an optical sensor. There are a lot of apparent paradoxes in faster-than-light travel that have been used to show that it's impossible (at least for undergraduates). This seems to require that they all be reexamined. But I'm trying not to speak Martian.

So let's say that the USS Enterprise is approaching Earth in a warp field at Warp 2. What happens to the light in the field? Can an observer on Earth see it? If so, what does it look like? If not, how can you measure the effect? Does Eel Oil help? How about Buckie?



This isn't an idle question you know. I'm thinking about the next Carrot Ship.

have u tried turning it on and off again

yupp.. that ususaly works.

or like.. plugg it in.

Or rum and chocolate. I am lagging. Fuel must be restored

Carly Castle wrote:

have u tried turning it on and off again

Thanks Carly, I just tried that. Still no luck.

For the Star Trek and Who fans out there, this works by creating a bubble in space-time so that the ship isn't actually moving within the bubble, but the whole bubble is "moving" as space in front of it shrinks and space behind gets bigger.
You can view this shrinking/expanding as a moving wave that the bubble and everything in it is "surfing" on.

halfwise wrote:
You could perhaps relate space-time curvature to aether drag, but the difference is that the aether hypothesis would still have light travelling relative to the aether, so even away from large masses you should be able to detect relative motion, whereas in flat space-time you can't detect relative motion.

I guess what's got me interested is that if, as this theory seems to suggest, we can create measurable waves in space-time capable of traveling large distances with relatively small amounts of energy, then it seems reasonable to suppose that other things in the universe may be making them as well. This suggests the possibility of a very non-flat dynamic space-time, with standing waves,traveling waves, ebbs and flows happening all around us like a troubled ocean.
Now try to visualize light traveling trough such a space-time and I think you'll see why I'm coming back to a modification of the old aether model, just like particles have come in and out of fashion over the years.

hmm, you may have a point there. Space-time is never really flat, what with gravity waves careening all over the place.

I understand what your babbling about,I do!, but Im buggered if I can elaborate !

What we are actually doing, Azriel, is a sort of quantum duality called elababblating. Feel free to pitch in.

I think Il "pitch" my "fork" some where else (in a parallel universe maybe ?) I can grasp,but,not qualified enough,mentally, to respond coherently, (that sounded marginally a level up from "chav" !)

is a sort of quantum duality called elababblating- Halfwise

Does that mean if no one reads the thread there is no elababblating? Or does the elababblating only come into being when someone observers the elababblating?

Or does the mere presence of other already written posts in the thread cause the elababblating to happen whether its observed or not?

Excuse me one second whilst I go over here to let my head explode.

Pettytyrant101 wrote:is a sort of quantum duality called elababblating- Halfwise

Does that mean if no one reads the threat there is no elababblating? Or does the elababblating only come into being when someone observers the elababblating?

Or does the mere presence of other already written posts in the thread cause the elababblating to happen whether its observed or not?

Yes, exactly! All of the above. Thanks for stating it so clearly!

I know what my problem is I'm nowhere near drunk enough yet for this.
To paraphrase Einstein slightly, "The more one learns about Quantum Theory the sillier it seems."

I love physics.

That's a good lass.

When I was teaching, the young women did better than the young men in physics, but somehow rarely chose to pursue it into higher education. But I'd like to believe the style of thinking paid off in cross disciplines. Just like postulate-theorem-proof pays off from learning Euclidean Geometry the right way (they've largely stopped teaching it the rigorous way in America ).

Since the Nobel Prize in physics was awarded to a couple of people who studied the problems of quantum reality in the 1990's, Scientific American has made available for a limited time an article written in 1997 about it.

I feel I should give a little introduction here since I still haven't gotten around to the quantum interpretations article (and am only partly through one that would precede it). You may recall, perhaps upon rereading this thread, that single particles such as photons can seem to do two things at once. If a photon is given the choice of going through two slits, if you let many photons go through, on the other side you will see an interference pattern as if a wave had been split by the two slits then made a ripple pattern on the other side. But the photons are only detected one at a time, meaning it doesn't make sense that they split. The typical quantum way to deal with this is to treat particles as if they act like waves until you look at them, at which point they look like single particles again, just distributed in a wave like pattern. Until you look, the particles are in a superposition of all the possibilities a spreading wave would be in, the 'collapses' into one possibility upon observation.

Erwin Schroedinger was bothered by this, and devised the famous "Schroedinger's Cat" thought experiment. You put a kitty in a box along with an "infernal device" consisting of a radioactive decay source and a detector connected to a vial of poisonous gas. The radioactive source is very weak, and particles are ejected at random, maybe on average once a minute or so. If such a particle is detected, the gas is released, killing the cat almost instantly.

Since the radioactive decay is governed by quantum mechanics, all the possibilities must exist at once in a quantum superposition until you measure it. But when does the measurement take place? When the detector goes off? When you look inside to see if the cat is dead or alive? If the second case, then the cat must also be in a quantum superposition of dead and alive until you take a look inside the box.

Our common sense tells us that obviously the cat is either dead or alive, so the wave function collapse must happen when the detector is tripped. But the detector may be made of something as simple as an atom in an excited state, which when a particle hits in releases a photon, which goes into a photomultiplier, which creates a current that opens the vial. But the excited atom is itself a quantum situation, as is each stage of the photomultiplier tube, which means the lines between quantum and non-quantum can be blurred all the way to the poor unsuspecting cat.

This is why the early quantum practicianers brought the idea of consciousness into the game: they thought that perhaps a conscious mind was the dividing line. But surely the cat is competent to know whether it is dead or alive....

Anyway, welcome to the logical jungle of quantum mechanics, a realm in which it is sometimes safer not to think too much. On to the article:


http://www.scientificamerican.com/article.cfm?id=bringing-schrodingers-quantum-cat-to-life

You highlight there Halfwise the problem I have always had with Schroedinger's Cat- everyone always forgets about the cats perception.

Terry Pratchett said if you put a cat in such a box there is in fact three potential states it could be in- Dead. Alive. And Bloody Furious.

good old Terry Pratchet ! Love him !

If my experience with cats is anything to go by, it's almost certainly the third option.

Ok, sorry about this. Pure Publications has decided to branch out and to provide occasional 'educational' special editions celebrating great Scotshobbits, where appropriate on threads.
Two things I am obliged to say.
Firstly as per my instructions from Angmar and Sons- "All events are true within the definition of truth being that which sells most newspapers, this being an ultimate truth. As it is the duty of the Press to get to the ultimate truth all newspaper stories must, by defininition, be true themselves. Especially when they may appear not to be."
And secondly on a personal note this editon counts as a bloody supplement to an edition I delivered a week ago. As far as I can make out the only purpose for this is so I dont get paid for delivering it.

And if you want to make your own cloud chamber at home, do the following:

• Take ye a fine clear plastic bottle and empty it. Preferably contents you enjoy emptying. Rinse out.
• Place within a small dribble of water (or just leave some rinse water). Actually, it need not be pure water, but if you have hopes of keeping the cloud chamber for a while it would be best if nothing is likely to be growing in it.
• Blow in a puff of smoke, source of your choosing. I recommend incense but pricier varieties will do as well. Seal tightly.
• Squeeze your chamber, wait about 10 seconds, then quickly release.

You have yourself a cloud in a bottle. If you now repeat the squeeze and release procedure rapidly while holding it up to the light, the effects are most dramatic. I do this for my weather camp, explaining how clouds are formed.

The smoke actually is playing the part of the charged particles. I believe if you leave out the smoke then squeeze and release next to an old style glowing watch hand (the radioactive kind) you may see tracks.

So Pure Publications didnt just make it all up then? Well I'll be buggered!

ps I am about to embark on making a cloud chamber as per your instructions Halfy, just as soon as I have finishjed emptying this bottle of its contents - oh, and if anything unfortunate happens during this experiment I will be blaming you!

Oh, News of the Pure is an unimpeachable source! The official accounts have none of the buckie backstory...the personal investigative journalism is simply topnotch.

Enjoy your cloud in a bottle. Not sure when plastics became commonplace, but Wilson wouldn't have had to work so hard to make a cloud chamber if he had just waited a decade or so for flexible clear materials.

edit: I guess you may have to put the watch inside the bottle, may not be feasible - unless the particles can penetrate plastic.

watch? I was just going to put some plutonium in there, I've had it kicking about for ages, well since the US navy was here at any rate, Ive been wondering what to use it for besides selling it to Iran on e-bay- wont that work?

'The official accounts have none of the buckie backstory'- Halfwise

Thats because of the laws here surrounding giving out to much information on crabbit mathmatics and buckie dreaming-you'd think other nations would be suspicous at the way we kep inventing stuff but as it gives us an edge its all state secrets.
If they knew half the stuff I'd given away here I'd be sent off to Goane Tam's Coo Bay, and you won't find it on google earth!