h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

great entry! I like the relaxed style the article is written in! I’m not an expert at all as far as physics are concerned , but I like reading stuff about theories that kind of (more or less) add up to me in the end.

kat

I agree. This is a very nice article.

A minor nitpick: The last footnote seems superfluous. The same text almost verbatim has been put into the entry a couple of paragraphs down.

There is a very stubborn part of me that wants to insist that quantum changes in state must not be instantaneous, but that the situation must rather be due to a lack of sophistication in our measuring instruments. We currently have no way of measuring something faster than the speed of light, do we? Or measuring things in the multidimensional space?

But maybe someday we'll have a better answer to this quandary.

I think it depends on how you set up an experiment. In some cases we could measure something that happens faster than the speed of light. For instance, people have measured cases where it appears that information has been conveyed faster than the speed of light (through a cloud of cesium atoms or something bizarre).

It's a matter of spacing,really. If you build a big enough experimental apparatus, such that your 2 entangled particles are far enough apart, and then mesaure the state of one of them, you could have loads of time to make the measurement of the second.

The problem is more that we have no way of measuring the state of the system without profoundly modifying it in the process.

ps congrats HELL!

I thought this one was heading straight into 'most neglected'

Thanks. Great. Hah...

Astonished,

HELL

Good point, dave. Obviously what we need is a monitoring apparatus that has an amazing mechanism to turn things *back* after they change.

And heavens no, HELL. There are two barriers to the popularity of science. The first is that some people have trouble understanding it. It seems that h2g2's denizens are a cut above, so that's eliminated. The other is that most articles are written with layers of needless complexity that makes them more perfectly correct but relatively boring.

An article that explains a concept in familiar terms is much appreciated.

i was just wondering if you would know whether it might be a possible theory that the two particles at their moment of seperation are both put into a 'twin-identical spin' in which they both spin identically to each other between the different possible outcomes that they could end up in. so at any given instant that it is observed, the particles would "decide" to be the same. i know this doesn't explain anything about their communication between each other, but it would explain the randomness of their outcome.

According to quantum theory, whatever happens to the particles will remain their own secret. At the moment you measure - BANG - all's over. That's quite a bummer for the folks trying to figure out what the heck those things are doing. On the other hand, I think, this leaves room for a number of theories, like the one you proposed. (I have never heard of that term 'twin-identical' in particular, and I guess someone would have to do some calculations to see this theory fit, but hey... who am I?) As far as I know, quantum theory *seems* to be OK, and stuff behaves randomly like tossed cois. Of course maybe *all* of Physics is bullsh*t, and turns out all is different than we thought...

Hmmm...

HELL

what we really need here is someone to write an understandable entry about electroweak measurement. I have no idea about it, but I know it would answer a lot of questions for us about this very topic.

EPR, it turns out, is a bit of a non problem. The crux of relativity is that you cannot transfer information faster than the speed of light. When you think about it no information can be transmitted using only entanglement.


Stuart