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Topic: Thoughts about the Ur-Quan... (Read 32997 times)
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Art
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You mean "cochlea", unless you hear through your eyes.
And the question of the size of the universe is more complex than just deciding whether vacuum can exist without reference points. I don't really understand it myself, but one factor is that matter bends space around itself, so in a closed universe (as opposed to an open universe) there's enough matter to bend all of space into a closed shape (so that, yes, it wraps around). Most cosmogonists seem now to think that the universe is closed, and are looking for where the mass is that would allow it to be so -- one reason for the search for "dark matter".
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Cronos
*Many bubbles*
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Posts: 170
Shofixti Scoutmaster
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I'm fairly sure the universe is not a closed system. If it were light would bend around eventually and we'd be seeing our galaxy in it's youth.
Dark matter in any case it whats speeding up the expansion of the universe, if the universe had enough matter to halt this expansion, we wouldnt note the increasing trend in the redshift of distant galaxies.
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Art
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Um, no. Light takes time to travel, and it's been a finite amount of time since the Big Bang. Also, the inverse-square law (the fact that light spreads out as it travels, and becomes less intense as it spreads out) plus the fact that the universe is filled with debris that absorbs light, is the reason we don't see all the way "through" the universe. (If the universe were infinitely old, eventually the debris absorbing the light would be heated to the point where the light would be re-radiated again, but... the universe isn't infinitely old, so that's moot.)
The accelerating redshift would not be caused by dark *matter*, as increased hidden mass would tend to cause the universe to contract. What you refer to is Einstein's cosmological constant, what's now being called "dark energy" or "vacuum energy", some sort of force pushing *against* gravity hidden from our view in the universe, and... as far as I can tell the attempts to figure out what it is or if the experiments saying it's there are even accurate are controversial. Again, this isn't my field. There are other reasons, however, to believe that there is extra matter in the universe and that mass-wise the universe is closed, or possibly flat (teetering right on the edge between closed and open; slowing in its expansion more and more and more but never actually stopping its expansion).
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Profound_Darkness
Zebranky food
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Current Mood: RL-Buisy...
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Didn't Einstien also say something about if the universe was contracting (shrinking back to the big crunch) that we wouldn't be able to tell? I don't remember the theory realy well since I heard about it back in my first year of junior high.
It could have been someone else but I am pretty sure Einstein was involved somehow (like theories) (it's been a while).
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Art
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I don't know what Einstein's own opinion was, but many scientists believed that time's arrow was linked to the expansion of the universe -- that the expansion of the universe is what causes time to appear to flow in one direction, and a contracting universe would appear to be the same as an expanding universe to the people inside it. (So the universe would always look like it was expanding; it would reach a point when time would come to an end, and reverse itself, from my limited understanding of the subject.)
That doesn't mean that a contracting universe would be identical to an expanding universe in all ways, however. I was reading one of Stephen Hawking's books about a month ago and he seems to think that this isn't necessarily true, that if the universe were contracting time would still be going in the same direction and we would be able to tell.
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Death 999
Global Moderator
Enlightened
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We did. You did. Yes we can. No.
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The whole contracting-universe implying backward-time idea was discarded about 50 years ago when someone realized they had put a sign error in one of their equations, or some other basic error. There is no catastrophic change to spacetime itself upon the reversal of the expansion.
Dark Energy could be the cosmological constant, or it could be the effects of extremely cold particles combined with quantum mechanics. According to the Schroedinger equation, the momentum of a particle is proportional to the curvature of its wavefunction. Thus, tighter curvature implies higher energy. If you are considering a group of particles (cold dark matter, say) in the lowest energy state, the energy is defined by the amount of space available. This creates a pressure for there to be more space. General Relativity provides a mechanism by which such a pressure actually creates more space.
Reaching back a bit, Entropy is not based on random motions. It is simply the logarithm of the multiplicity of the state. Multiplicity being the number of 'similar' states on a statistical level... states where you switch two particles, or move one to the side but there is no significant change to the system (for a well-chosen definition of 'significant'). The entropy does not rely on any physical properties in specific; this is why one can speak of the entropy of a bitstream. It is the exact same idea; the same calculations. etc.
What you can't define on a bitstream, though, is temperature.
The Temperature is where energy comes in; it is the reciprocal of the derivative of the entropy in respect to the insertion or removal of energy. So, if it takes a little energy to increase the entropy a lot, you have low temperature and the system will like to absorb energy from higher-temperature sysems, in order to maximize entropy within the energy constraints.
That said, I agree with both Meep and Art.
As for quantum teleportation (generic version), here are the steps:
1) get two or more particles to fit into a specific relation to each other, but prevent any other particles from being affected by the specifics of this relation.
2) separate the particles
3) measure the particle you have, collecting exact information on what comes out.
you now know what state the other particles are in. For the people THERE to know what state their particles are in, they either need to measure them or you need to tell them. Note that you don't get to pick what you measured, so you can't transmit information to them in this manner.
Now, as for the more specific teleportation methods, it's more complicated.
steps 1-3 as before, then:
4) transmit the results of this measurement to the person who has the other particle
5) they then put in a carefully chosen set of particles which will interact with the system in a relatively predictable way, producing a particle identical to the one you measured. This continues to apply even if you messed around with your particle first (so long as you didn't measure it in the process) (which is in itself quite tricky).
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Pages: 1 ... 8 9 [10]
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