A wee question... :) (Phys) Watch

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Chubb
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#21
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1. Yeh they think that there are more than one dimension because there isn't enought matter for the gravity that we are experiencing - think its seeping through form another dimension.

2. Antimatter is just the same as normal matter but has an opposite charge as far as I know - never heard anything about it being in the opposite direction in time.
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Nylex
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(Original post by Chubb)
2. Antimatter is just the same as normal matter but has an opposite charge as far as I know - never heard anything about it being in the opposite direction in time.
Opposite spin, too.
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john !!
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This spin thing seems silly. I get the "too hard for you to learn at college, so we totally lie to you" impression from college. What does it mean?
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rts
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intrinsic angular momentum of a particle. that's all i know.
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Wagamuffin
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Hmmm I am reading a string theory book (admittedly at a snail's pace!) and it has convinced me that there couldn't be more than one temporal dimension. The reasoning is something along the lines of: we move only one way through time, and if there were another dimension, we would tend to "lose" each other.... if that says anything to you I got a bit distracted from the book by the 5th Harry Potter!
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john !!
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Well yeah, it would be like walking on a field rather than on a path.
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Willywonko
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(Original post by polthegael)
Can anyone expalin two things to me about time, please?

1) Are there more than one temporal dimensions? If so, can anyone have a stab at explaining that in a way a fool like myself can understand?

2) It has been claimed (by Feynman) that antimatter is just ordinary matter but travelling the other way through time. How does that work?
Whoa horsy!!

This is incredebly advance stuff to be discussed in a forum like this.

The answer, on the other hand, is simple:"we're not quite sure, but we have many good theories."

1. I, being a fan of the string theory, would argue yes. It is hard to explain in a jiffy, but string theory predicts "branes", which is kind of like multidimensional pancakes (really!) . These branes exists in many dimensions, up to (what was it again...?) 26 space dimensions and (probaby) 13 time dimensions. It is incredably hard to imagine more dimensions than that of which we live in, but try to think that you are a 2D cartoon. You wouldn't be able to notice the third room dimension would you? And the funny thing is that the safest safe in the whole 2D would could without effort be breached by a 3-dimensional being. In the same way can a 4D- being cross right through our world without us noticing.

2. The thing about antimatter travelling backwards in time sounds fishy. I'm not a specialist in the area, but i would argue that they are just regular particles with the opposite charge. Just because one mathematically deducts that a positron is equivalent to a electron travelling backwards in time, doesn't mean that they always do. And the spin thingy is about quarks, not leptons, in the sense of antimatter, I presume.

Don't kill me if I'm wrong, just wanted to play along with you gyus.
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LH
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Has someone already made a joke about urine?
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m:)ckel
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(Original post by Lord Huntroyde)
Has someone already made a joke about urine?
yeah, it was the first reply :rolleyes:
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RobbieC
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I thought the hypothesis was quite lovely.

Whosoever claims that science cannot be based on assumptions and guesswork is, in my eyes, a little ignorant. As someone has already pointed out, many of the breakthroughs in science today, and in the past, are the result of interdisciplinary guesswork and prediction, whether it be founded in mathematics or not.

Jeez, an expansion rate like that, and the place is still damn crowded...
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rts
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(Original post by RobbieC)
Jeez, an expansion rate like that, and the place is still damn crowded...
If one hydrogen atom per cubic metre is crowded
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khil
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(Original post by rts)
1. Nobody really knows. String theory says there are 12 (I think - something like that) in total but it can't be proven.

2. I think it is that on Feynman Diagrams (diagrams which respresent particle interaction), an electron travelling forwards through time is mathematically equivalent to a positron travelling backwards through time and vice versa. Don't quote me on this though.

I don't really know a lot about positronium (had to look it up on google to see what it was) but I'm going to try and play devil's advocate with your theory anyway:

Firstly, a positron can't "stay" anywhere for a period because of the uncertainty principle - it would be constantly moving about (I'm not sure if "governed by the laws of quantum mechanics" already covered this).

An electron travelling the other way through time would be the same as a positron travelling forwards through time, and if you fired a positron (forwards through time) at another positron, you wouldn't get positronium.

Also, I think they make positronium by firing an electron at a positron and these are both forwards through time so I don't understand how the electron could be going back in time.

Also, if the electron was going back in time to reach the positron, after we had seen it annihilating (assuming we move forwards in time), wouldn't we just see the electron re-appear from the annihilation and travel back from where it came?

Also, I would guess the duration of co-existence can probably be calculated from QED (relativity + quantum theory + electromagnetism theory) or this would be a lot more prominent problem in science. Putting it down to relativity is probably the right way of going about it I would think.

Also, two objects meeting cannot be described as instantaneous because as you try and measure to a smaller and smaller time scale, the energy fluctuations of the fields become greatly magnified (uncertainty principle again).

Interestingly enough, there is currently a popular grand unified theory that proposes space and time are quantised, it's called Loop Quantum Gravity.

And it's Professor Hawking . Hope this makes sense.
Hey whoever you are - are you from Cambridge or something? Someone explain to me what a positron is and what a positronium and what a lepton is!!!! (I don't even do physics AS so that explains my ignorance) All this sounds extremely interesting, however, just mind-boggling :eek: and truth is the only thing I understand is the electron - thanks to GCSE and AS Chemistry hehe .
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Nylex
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(Original post by irisng)
Someone explain to me what a positron is and what a positronium and what a lepton is!!!!
Positrons are basically electrons with a positive charge. Positronium?

Leptons are fundamental particles (ie. they're not composed of other particles) but not quarks (which are also fundamental) - eg. electrons, positrons, tau particles and all their associated neutrinos.

Hopefully that's right, haven't done any particle physics in a while. No doubt elpaw will correct me .
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dinkymints
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(Original post by irisng)
Hey whoever you are - are you from Cambridge or something? Someone explain to me what a positron is and what a positronium and what a lepton is!!!! (I don't even do physics AS so that explains my ignorance) All this sounds extremely interesting, however, just mind-boggling :eek: and truth is the only thing I understand is the electron - thanks to GCSE and AS Chemistry hehe .
A positron is the antiparticle of an electron.

An electron is a type of lepton - leptons are fundamental particles. Other leptons are muons and taus, plus 3 types of neutrinos.

I think, anyway, I've only done GCSE physics!!

*edit* Beat me to it!!

Forgot to say, here's a good site:

http://durpdg.dur.ac.uk/lbl/particle...tstandard.html
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khil
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(Original post by polthegael)
I have a head full of random and useless facts
Makes two of us! Although mine is voluntary it all comes from documentaries - but only so much you can learn cus they repeat themselves. I've literally watched all there is to watch, given the programmes available on discovery channels in sky for science and wildlife. Even if I haven't they always go on about the same things - like spiders dissolving prey's insides and sicking it out like a milkshake - I've heard that in all the spiders documentaries I've watched, and believe me I've watched a lot. They don't repeat facts about the brain so often though cus there's more to talk about - trouble is then they start repeating the same documentaries!!!!!!1
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dinkymints
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(Original post by Nylex)
Why aren't leptons fundamental??
typo (or my fingers are not connected to my brain!), I edited it straight after... you're quick!!
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khil
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Just to clarify - I'm not keen on spiders. However I am a bit of a snake fanatic hehehehehehehehe (mwhahahaha - see my fangs?)
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Nylex
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(Original post by dinkymints)
typo (or my fingers are not connected to my brain!), I edited it straight after... you're quick!!
Hehe. Will delete that post above.
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elpaw
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#39
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leptons could be unfundamental - they could be branes, which themselves could be made of "brane substance" which would be fundamental
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Nylex
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(Original post by elpaw)
leptons could be unfundamental - they could be branes, which themselves could be made of "brane substance" which would be fundamental
Told you :rolleyes:. What are branes??
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