Quantum Entanglement

mickeydevine

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

Am I reading this right. Can particles billions of lightyears apart be in some way connected??. I must be reading it wrong.

Professor_Fink

mickeydevine wrote: »

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

Am I reading this right. Can particles billions of lightyears apart be in some way connected??. I must be reading it wrong.

Yes, they can. You should bare in mind though that it is not a causal link. It doesn't allow you to transmit information. It's simply a very strong type of correlation.

mickeydevine

Weird! Maybe from our perspective the universe is immense but at a quantum level its not that big. How you can theorise something like that using maths is beyond me.

CoupleLoads(soz got carried away) of questions if anyone fancies it:

1: If the universe were a meter stick, how far has our technology allowed us to see i.e are we 100% sure the make up of the universe.

2: Is there an attractive force between matter and anti-matter?

3: Neutrinos have a non-zero mass, really small. Would a detectable amount of energy be released in contact with anti-neutrinos?

4: Do all particles have anti-particles? If so, are anti-matter stars possible and how would they differ from matter stars?

5: I saw a picture of the universe shortly after the big bang few years ago, sort of eliptical shaped, and I think it was from ambient radio waves? Does anti-matter give off the same type of radio waves, are they distinduishable?

6: Since stars are neutrino "factories" are they in anyway responsible for the expansion of the universe?

7: Would it be possible for anti-matter to be present in the universe, somehow separate but observable?

Thanks.

Podge_irl

I'm gonna attempt to answer these but I imagine Fink will come along and give you the right answers in a while

mickeydevine wrote: »

1: If the universe were a meter stick, how far has our technology allowed us to see i.e are we 100% sure the make up of the universe.

No. It's a reasonably impossible question to answer, as new physics can be discovered all the time. We understand the universe at our energy level quite well (QED for example has been confirmed up to 99% by experiment), however many of our theories break down at high energy levels/small distance scales.

2: Is there an attractive force between matter and anti-matter?

Gravity affects anti-matter and matter equally and is an attractive force.

3: Neutrinos have a non-zero mass, really small. Would a detectable amount of energy be released in contact with anti-neutrinos?

Detectable as in physically possible to detect, then yes I think so. I don't know whether we possess the technology to do so at the moment though.

4: Do all particles have anti-particles? If so, are anti-matter stars possible and how would they differ from matter stars?

Yes. Anti-matter stars are possible, though obviously we don't see any in the universe as they wouldn't last very long. There is, I believe, no real reason why the universe shouldn't be predominantly anti-matter instead of matter and its not known why exactly we have the asymmetry.

5: I saw a picture of the universe shortly after the big bang few years ago, sort of eliptical shaped, and I think it was from ambient radio waves? Does anti-matter give off the same type of radio waves, are they distinduishable?

That would have been a diagram of the CMB - the cosmic microwave background radiation. It arises as a result of the highly energetic beginnings of the universe. Its just EM radiation though - the same EM radiation(essentially) you would get from annihilation of a particle and an anti-particle. There is no way to tell where a particular photon came from - it could have come from an electron decaying to a lower energy level in an atom or from a matter-antimatter collision.

6: Since stars are neutrino "factories" are they in anyway responsible for the expansion of the universe?

I'm not sure I understand this question. Neutrinos aren't in any way responsible for the expansion of the universe, so the fact that stars produce them is immaterial.

7: Would it be possible for anti-matter to be present in the universe, somehow separate but observable?

Anti-matter is just as observable as normal matter. It's possible for anti-matter to exist but highly unlikely as any contact with matter will result in annhilation. There is no reason for us to think that the universe shifts at any point in space to being predominantly antimatter.

mickeydevine

Podge_irl wrote: »

I'm not sure I understand this question. Neutrinos aren't in any way responsible for the expansion of the universe, so the fact that stars produce them is immaterial.

Yeah soz badly formatted question. I should have said do neutrinos have any affect on the expansion of the universe. You answered anyway, thanks.

My thinking is that, from what I understand the universe isn't expanding just at the edges but the space between galaxies is expanding i.e space is created between galaxies (correct me if I'm wrong). Therefore something has to be creating space and since galaxies are billions of stars then whats produced in stars may affect it. So although nonzero in mass, the universe produces a huge amount of neutrinos ( a googalplex, or is that a googal to far:D) p/s. I'm a layman so feel free to add :rolleyes: to your answer:pac:.

Could anti-neutrinos, given their size, last long in the universe or would they be annihilated immediately.

Podge_irl

Space is expanding between galaxies, but no new space is being created. Its one of the trickier things to wrap your head around. Think of the universe instead as a balloon. Its the analogy that is always used, but its used because its a good one. As you blow up the balloon points on the surface will move further and further apart, however, you have not created any "new" bits of balloon between them.

There are a number of theories behind the expansion of the universe, but it is generally thought to be caused by some form of "dark energy" - which is similar to dark matter. It is energy that we can not measure directly as it doesnt interact the same way that all matter we know of does.

All anti-matter is annihilated as soon as it interacts with matter. However, neutrinos don't interact much (which is why they are so hard to detect) so I imagine anti-neutrinos would last longer then most anti-particles.

mickeydevine

Podge_irl wrote: »

Space is expanding between galaxies, but no new space is being created. Its one of the trickier things to wrap your head around. Think of the universe instead as a balloon. Its the analogy that is always used, but its used because its a good one. As you blow up the balloon points on the surface will move further and further apart, however, you have not created any "new" bits of balloon between them.

There are a number of theories behind the expansion of the universe, but it is generally thought to be caused by some form of "dark energy" - which is similar to dark matter. It is energy that we can not measure directly as it doesnt interact the same way that all matter we know of does.

All anti-matter is annihilated as soon as it interacts with matter. However, neutrinos don't interact much (which is why they are so hard to detect) so I imagine anti-neutrinos would last longer then most anti-particles.

So, like a balloon, is there a limit to its eventual size i.e will it pop.

Is it theoretically possible for the universe to be flooded with anti-neutrinos and the anihilation of them giving small amounts of energy yet in such large numbers producing, overall, a large amount of energy?

Podge_irl

mickeydevine wrote: »

So, like a balloon, is there a limit to its eventual size i.e will it pop.

Is there a limit? Maybe. Will it pop? No. this is where the balloon analogy fails unfortunately. As the balloon expands the tension on the surface increases - a similar situation does not happen with the universe (in fact much the opposite happens). The balloon analogy merely gets across the conceptual nature of the expansion.

The universe will do one of three things
1) Expand forever - if this happens then eventually all the energy is the universe will sort of dissipate out. Stars will stop forming and the universe will essentially die. Its sometimes referred to as the Big Cool.
2) It will expand til it reaches a certain point and then just stop.
3) It will expand til it reaches a certain point and then start collapsing - this would require the gravitational attraction to be greater then the force causing the expansion.

As things stand we think 1) is what is actully going to happen.

Is it theoretically possible for the universe to be flooded with anti-neutrinos and the anihilation of them giving small amounts of energy yet in such large numbers producing, overall, a large amount of energy?

Well yes. It depends on your definition of small and large, but without meaning to belittle the question many small things tend to add up to a large thing eventually. However, again no "new" energy is being created. It took energy to create these neutrinos and anti-neutrinos.

mickeydevine

So hypothetically, what would be different about our universe if it was like the diagram attached? Everything probably.

Podge_irl

I'm afraid I don't really understand what that diagram is getting at.

mickeydevine

took me ages. Cheers Podge.

Professor_Fink

Hi guys, sorry for the delay. Podge's answers are pretty good, but there are a few points I would probably answer a little differently, so let me have a go.

mickeydevine wrote: »

1: If the universe were a meter stick, how far has our technology allowed us to see i.e are we 100% sure the make up of the universe.

It's impossible to know. We don't know whether the universe is infinite in extent or finite, although the current thinking seems to lean more towards a finite universe. What I can say is that our technology allows us to see almost as far as is possible.

The big bang occured a little over 13 billion years ago, and since no effects travel faster than the speed of light, we have an observable universe that is about 27 billion light years across, and we can see almost that far. The Hubble deep field view shows plenty of very very old objects, and the cosmic microwave background radiation is a remenant from 380000 years after the big bang (and hence is coming from very far away.

mickeydevine wrote: »

2: Is there an attractive force between matter and anti-matter?

As Podge said, gravity is such a force, but theere are other forces which can either be attractive or repulsive (or not couple to specific particles). These are the weak and strong interactions and electromagnetism. None of the forces depend on whether whether the particle is counted as matter or anti matter, but rather on properties (such as charge and isospin) which vary from particle to particle.

mickeydevine wrote: »

3: Neutrinos have a non-zero mass, really small. Would a detectable amount of energy be released in contact with anti-neutrinos?

Neutrinos are extremely weakly interacting, including neutrino-neutrino interactions, and so such interactions would be incredibly rare. Any energy released would almost certainly be in the form of gamma rays, which are in principle detectable, but also rather weakly interacting. Your chances of detecting such an event are pretty low.

mickeydevine wrote: »

4: Do all particles have anti-particles? If so, are anti-matter stars possible and how would they differ from matter stars?

You may want to check out the Wikipedia article on antiparticles: http://en.wikipedia.org/wiki/Antiparticle

Anti-matter starts would be identical to matter start if the scientists observing them were made up out of anti matter. If we observed the anti-matter star, then we would find that all the charges had been flipped, which would flip the magnetic field.

mickeydevine wrote: »

5: I saw a picture of the universe shortly after the big bang few years ago, sort of eliptical shaped, and I think it was from ambient radio waves? Does anti-matter give off the same type of radio waves, are they distinduishable?

I suspect you mean the cosmic microwave background radiation. The reason it was elliptical is not because the universe is necessarily elliptical, but rather because of how they plot the measurements. Basically the ellipse is an unrolled version of what the sky would look like.

The anti-particle of photons (which make up the CMB) are also photons, so we would see identical results from both matter and antimatter.

mickeydevine wrote: »

6: Since stars are neutrino "factories" are they in anyway responsible for the expansion of the universe?

Not really. The production of neutrinos isn't in any way adding energy to the universe, and the neutrinos aren't directly responsible for the expansion, so I don't really see what you are getting at here.

mickeydevine wrote: »

7: Would it be possible for anti-matter to be present in the universe, somehow separate but observable?

It could be in a seperate region of the universe, but hadrons react extremely violently with their antiparticles, which would be very easy to see on a large scale, so they can't really co-exist in the same space.

mickeydevine

Professor_Fink wrote: »

Not really. The production of neutrinos isn't in any way adding energy to the universe, and the neutrinos aren't directly responsible for the expansion, so I don't really see what you are getting at here.

I read that the expansion of the universe began accelerating about 5 billion years ago so I was thinking, almost certainly wrongly, that the universe is like a bath with the tap dripping, after a certain amount of time the bath fills and the water spills over the edge. Stars weren't born at the big bang but after gases coalesed and the mass was right fussion began. So with stars being the most active and numerous bodies in the universe expansion was affected by their output. Really just thinking out loud. Also, is it true that right after the big bang the universe was expanding faster than the speed of light?.