11-05-2003 03:57									#61
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quote: Originally posted by Willem No, light contains photons which have a very slight mass. When they connect with a sail, they would push the craft forward.

nope

photons have no mass

they do have momentum though, and carry energy

Jon Miller

	11-05-2003 04:01									#62
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quote: Originally posted by Jon Miller no they aren't fusion power is not economical at the moment and I have made a Superconductor (Type 2, but ....) Jon Miller

OK, let me restate that. Theoretical on a practical level. Of course superconductors might be able to function in the cold of space. What is it now, the temperature of liquid helium before they actually work? That might be feasible in a space ship, but there's still to many problems with fusion power.

	11-05-2003 04:03									#63
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Somehow I believe we will use the so-called dark matter that occuppies space. We will gather that in, accerlerate it, and keep the pedal to the metal the whole distance. If it takes only six years to Alpha Centauri at one g constant accelleration and deceleration, it would take only three years at two g's. This sounds to me more than doable. We actually may be able to do this within the next 100 years.

	11-05-2003 04:05									#64
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quote: Originally posted by Jon Miller photons have no mass

Well I admit I'm no physicist, but I seem to recall that photons can be considered both matter and energy, depending on how you conduct the experiment. And since matter has mass...

	11-05-2003 04:07									#65
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quote: Originally posted by Ned If it takes only six years to Alpha Centauri at one g constant accelleration and deceleration, it would take only three years at two g's.

Except that someone mentioned that it takes light 4.3 years to reach AC, and nothing can travel faster than light. Provided Einstein was right of course.

	11-05-2003 04:16									#66
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Willem, Now you got me thinking. Is this time measured from the spaceship or from Earth?

	11-05-2003 04:24									#67
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quote: Originally posted by Ned Willem, Now you got me thinking. Is this time measured from the spaceship or from Earth?

From Earth I imagine. I'm just going by a previous post and presuming that the estimate is correct. On the spaceship, relative time would slow down as you approach the speed of light, so 4.3 years might seem like only 2 for people on the spaceship. I don't know the exact calculation of that difference though. Like I said, I'm no physicist.

	11-05-2003 04:24									#68
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quote: Originally posted by Willem OK, let me restate that. Theoretical on a practical level. Of course superconductors might be able to function in the cold of space. What is it now, the temperature of liquid helium before they actually work? That might be feasible in a space ship, but there's still to many problems with fusion power.

type 2 superconductors can work at as high of temperatures as120 K

helium is of course 4k

lots of prolbems with fusion, that is true

Jon Miller

	11-05-2003 04:34									#69
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quote: Originally posted by Willem Well I admit I'm no physicist, but I seem to recall that photons can be considered both matter and energy, depending on how you conduct the experiment. And since matter has mass...

photons are both particles and waves (There is duality there)

and mass and energy are related by Einstein, E=mc^2

and light can also bend space-time

(I am a physicist (in training), but my understanding of GR is limited)

but lgiht does not have mass as we know it (as in photons have 0 rest energy)

E^2 = (mc^2)^2 + (pc)^2

for photons, E = pc

in fact, only if m = 0, may the particle travel at c

Jon Miller

	11-05-2003 04:34									#70
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quote: Originally posted by Jon Miller nope photons have no mass they do have momentum though, and carry energy Jon Miller

Matter is just condensed energy, they are one in the same acording to quantum mechanics. If they are particles of matter, Fermions, or particles of energy, Bosons, depends on thier quantum "spin."

	11-05-2003 04:40									#71
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WTF?

Jon Miller

	11-05-2003 04:42									#72
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you have some huge misconceptions about physics

I would recommend a class in college (if you are of the right age demographic)

if you are no longer in college, and not interested in going back

Feynman's Lecture series on Physics is good (it is a 3 part and covers Mechanics, E&M and intro Quantum Mechanics)

Jon Miller

	11-05-2003 04:46									#73
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quote: Originally posted by Odin Matter is just condensed energy, they are one in the same acording to quantum mechanics. If they are particles of matter, Fermions, or particles of energy, Bosons, depends on thier quantum "spin."

So theoretically, we could convert the space ship (matter) into light, travel to AC in 4.3 years, then convert the energy back into matter again if we can learn to control that spin.

Another theory I've read regarding quantum physics is the possibility of creating a wormhole, and travelling between two points in the universe simultaneously. The article I read though said it would probably require the amount of energy produced by a super-nova in order to do it.

	11-05-2003 04:48									#74
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umm, Willem, Odin doesn't have a clue about what he is talking about

Jon Miller

	11-05-2003 04:50									#75
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quote: Originally posted by Jon Miller WTF? Jon Miller

I'm 17 and I just stumped a Physics Major. Read A Brief History of Time by Stephen Hawkins to see what I'm talking about.

	11-05-2003 04:52									#76
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quote: Originally posted by Jon Miller umm, Willem, Odin doesn't have a clue about what he is talking about Jon Miller

Not to many people do when you start discussing quantum physics. I admit it leaves me largely baffled when I try to understand it.

	11-05-2003 04:54									#77
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ack

I can't let this be

most particles have both rest energy (ie mass) and momentum (and thus energy greater than rest energy)

while it is true that the photon is a Boson, there are many more Bosons that do have rest energy

the main difference between fermions and bosons is what sort of statistics they follow, (fermi-Dirac or Bose-Einstein)

the out growth of this is the pauli exclusion principle, which says that any two fermions cannot be in the same state

Jon Miller

	11-05-2003 04:57									#78
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quote: Originally posted by Odin I'm 17 and I just stumped a Physics Major. Read A Brief History of Time by Stephen Hawkins to see what I'm talking about.

I am a grad student

my response was an indication of my confusion as to how you got the perception that bosons are particles of energy and fermions are particles of matter

Jon Miller

	11-05-2003 05:13									#79
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quote: Originally posted by Willem Not to many people do when you start discussing quantum physics. I admit it leaves me largely baffled when I try to understand it.

it's not too bad

check out the lecture series I suggested

really the best way to go about is to do so slowly and from the base up, trying to jump in at the top will only igve oyu silly misconceptions

I presonally like my textbook by Townsend, but it would probably be ebst to see some modern/begining QM first

my QM classes actually have been my easier classes recently

Jon Miller

	11-05-2003 05:13									#80
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quote: Originally posted by Jon Miller ack I can't let this be most particles have both rest energy (ie mass) and momentum (and thus energy greater than rest energy) while it is true that the photon is a Boson, there are many more Bosons that do have rest energy the main difference between fermions and bosons is what sort of statistics they follow, (fermi-Dirac or Bose-Einstein) the out growth of this is the pauli exclusion principle, which says that any two fermions cannot be in the same state Jon Miller

MY BAD!!!

	11-05-2003 05:16									#81
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I think I'll stick to Biology, Physics has too much math for me.

	11-05-2003 05:44									#82
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don't give up on physics

I know a number of people who like physics and dont' love math (even tohugh loving math does help)

Jon Miller

	11-05-2003 06:45									#83
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Jon:

quote: photons are both particles and waves (There is duality there)

I read an article once that talked about how the 'scientific community' ended the photon debate by saying that:

"A photon behaves as a particle under certain circumstances."
"A photon behaves as a wave under certain circumstances."

I thought this was a fairly novel way to state things, rather than saying 'both' or 'neither'. It also carries a bit of a philosophical connotation, regarding duality and relativity and all that jazz.

What does this have to do with anything? I don't know, but for some reason it just came to my mind when I read that line.

	11-05-2003 06:54									#84
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I could never figure out how matter is a state of energy.

It just doesn't seem to make sense.

	11-05-2003 07:07									#85
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Am I the only one who finds it ironic to go into (deep)space using sails???
I do hope we don't encounter any aliens on that trip, hell, we'd be the laughing stock of the whole universe...

	11-05-2003 08:10									#86
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quote: Originally posted by Lancer I could never figure out how matter is a state of energy. It just doesn't seem to make sense.

E=MC^2

	11-05-2003 08:15									#87
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quote: Originally posted by alva Am I the only one who finds it ironic to go into (deep)space using sails??? I do hope we don't encounter any aliens on that trip, hell, we'd be the laughing stock of the whole universe...

Nah, other civilizations will probably be using them too. They are a very efficent means of travel; a good ion drive wouldn't be too bad either, but the acceleration sucks.

	11-05-2003 08:23									#88
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quote: Originally posted by Dr Strangelove I think that someone did the calculations on this and determined that it wouldn't supply enough power.

All you need to do is to accelerate at 1g half the way and slow down at 1g the other half. The good thing is when the ship gets close to c time slows down.