Freethought & Rationalism Archive

Wyz_sub10 · 01-21-2003, 12:53 PM

Quote:

Originally posted by cfgauss
Wyz_sub10:
The author makes a common mistake in the article. How did the Hydrogen get to near the speed of light? It accelerated. Acceleration is *not* relative, so there *is* a difference between the two, and we can tell wich of the atoms is in motion. Though the energy required to accelerate something that fast (assuming that the "mass" increase he gave is correct) in in the ballpark of 9x10^34 J.

I just want to be clear that I think the article is nonsense. I just present it to provoke some discussion on the topic. I will check out your link, though.

cfgauss · 01-21-2003, 01:00 PM

You should also check out that link's parent, http://www.desy.de/pub/www/projects/Physics/. It has a lot of *very* good information and links there.

Shadowy Man · 01-21-2003, 03:20 PM

Quote:

Originally posted by cfgauss

Shadowy Man:
Everything below Iron *was* created (possibly things above, but we can't be sure) in the Big Bang, just in *very* small amounts. (Technically, they were *all* created *shortly after* the Big Bang.) But, believe it or not, when you've got the ammount of matter in the universe crammed into a teeny space, just cool enough to not blow itself apart, there will be some fusion taking place . Most of the stuff above Helium, however, was created in stars.

No, I don't think this is true. What model of Big Bang Nucleosynthesis are you taking this from? Or are you just making it up?

It's possible that elements as heavy as Beryllium were created in BBN, but Lithium is already nine orders of magnitude down from hydrogen.

Friar Bellows · 01-21-2003, 03:20 PM

Quote:

Originally posted by cfgauss
My analogy was perfectly fine. It simply says that mass and energy are related, just like force and distance in a spring, or distance and time at a speed. You can easily only consider k and v to be constant in these cases.

So what? What they really are are variables (poor grammar!) If you pick one variable on the right hand side of F=kx or d=vt, that variable does not uniquely determine the value of the quantity on the left hand side. On the other hand, for E=mc^2, m uniquely determines the value of E because c is a universal constant (dependent on nothing). This is why you can consider E and m to be equivalent.

Quote:

Also, c may well be a varyable, too!

Not in any well-tested physics I know.

Quote:

I can pick the frame of the Apollo 11 astronaughts urine after it was ejected from the spaecraft, if I want, but there's nothing special about it. Often we pick coordinate frames wherein things look "nice" (why do you think we use rectangular coordinates so often?), but there's nothing special about any of them. You get the same results in all of them, but it's easier to use one or two. There is, however, no *prefered* frame! Just nice ones and not as nice ones.

Yes, I think I'm wrong here and you're right.

cfgauss · 01-21-2003, 04:50 PM

Friar Bellows:
My examples are perfectly fine! In F=ma, m is a constant for an object (are F and a equivalent for an object?); in F=kx, k is a constant for the spring (are F and x equivalent for the object?); in E=mc^2, c is a constant for the universe! If you want some more...
1-Cos(x)^2 = Sin(x)^2, are sin and cos the same?
For a right triangle, leg^2 + leg^2 = hypotenuse^2, are they the same?

And like I said, when you use E=mc^2 like that, you're mixing measurements from different frames, which you can't do! E=mc^2 for an object *not* at rest is E = gamma mc^2 = (p^2c^2 + m^2c^4)^(1/2).

http://www.desy.de/pub/www/projects/...y/SR/mass.html

There are several "theories" (that don't do much at the moment) that say c may've changed in time. There're experiments that seem to indicate this, too.

And I'm always right

.

Jesse · 01-21-2003, 05:20 PM

cfgauss:
I'm saying Hawkingfan's "arrow of time" thing makes no sence, I know what the arrow of time *is*. But to say or to any way imply that the arrow of time has anything to do with preception is nonsense.

Do you think the fact that we can remember the past but not the future is in no way related to the thermodynamic arrow of time? I have heard a number of physicists suggest that the psychological arrow of time is directly related to the thermodynamic arrow of time. Stephen Hawking, for example:

Quote:

Suppose, however, that God decided that the universe should finish up in a state of high order but that it didn't matter what state it started in. At early times the universe would probably be in a disordered state. This would mean that disorder would decrease with time. You would see broken cups gathering themselves together and jumping back onto the table. However, any human beings who were observing the cups would be living in a universe in which disorder decreased with time. I shall argue that such beings would have a psychological arrow of time that was backward. That is, they would remember events in the future, and not remember events in the past. When the cup was broken, they would remember it being on the table, but when it was on the table, they would not remember it being on the floor.

It is rather difficult to talk about human memory because we don't know how the brain works in detail. We do, however, know all about how computer memories work. I shall therefore discuss the psychological arrow of time for computers. I think it is reasonable to assume that the arrow for computers is the same as that for humans. If it were not, one could make a killing on the stock exchange by having a computer that would remember tomorrow's prices!

A computer memory is basically a device containing elements that can exist in either of two states. A simple example is an abacus. In its simplest form, this consists of a number of wires; on each wire is a bead that can be put in one of two positions. Before an item is recorded in a computer's memory, the memory is in a disordered state, with equal probabilities for the two possible states. (The abacus beads are scattered randomly on the wires of the abacus.) After the memory interacts with the system to be remembered, it will definitely be in one state or the other, according to the state of the system. (Each abacus bead will be at either the left or the right of the abacus wire.) So the memory has passed from a disordered state to an ordered one. However, in order to make sure that the memory is in the right state, it is necessary to use a certain amount of energy (to move the bead or to power the computer, for example). This energy is dissipated as heat, and increases the amount of disorder in the universe. One can show that this increase in disorder is always greater that the increase in the order of the memory itself. Thus the heat expelled by the computer's cooling fan means that when a computer records an item in memory, the total amount of disorder in the universe still goes up. The direction of time in which a computer remembers the past is the same as that in which disorder increases.

Our subjective sense of the direction of time, the psychological arrow of time, is therefore determined within our brain by the thermodynamic arrow of time. Just as a computer, we must remember things in the order in which entropy increases.

A Brief History of Time, pp. 146-147

Osm bsm Y. · 01-21-2003, 06:02 PM

=(

Quote:

NumberTenOx

The reason that it took 300,000 years for atoms to form is that before that, the electrons and protons were too hot to form atoms. They might try, but they would rip apart from the heat. Only after the universe cooled down enough could they form stable atoms

i haven't ever been taught what heat is aside from molecules vibrating. i remember an experiment in high school where we heated air in a test tube that was covered with a balloon and the balloon expanded because heat increased the speed of the molecules of air in the tube and thus also increased the pressure in the tube...expanding the balloon.

if heat is related to motion in any way, shouldn't there be some relation between a particles ability heat and it's speed? it would seem to me that as something approached the speed of light it would go to absolute zero temperature...since it's particles that make it up aren't able to themselves travel faster then the whole.

i also don't understand how a single particle can be considered hot

cfgauss · 01-21-2003, 06:32 PM

If you're in a boat moving down a river, does your perception of it matter? No, it doesn't. You are regardless. Is your perception related to it? Generally. Does that mean anything? No.

Jesse · 01-21-2003, 06:49 PM

cfgauss:
If you're in a boat moving down a river, does your perception of it matter? No, it doesn't. You are regardless. Is your perception related to it? Generally. Does that mean anything? No.

I don't understand what you're getting at with this response. Do you agree or disagree that our perceptual arrow of time owes itself to the thermodynamic arrow of time, and that the explanation for why the two arrows are related is at least somewhat nontrivial?

cfgauss · 01-21-2003, 06:55 PM

Well, why do we think we're moving down the river in the boat? Because we are. That's the relation, no more. It's trivial.

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01-21-2003, 01:00 PM	#72
cfgauss Regular Member Join Date: Jan 2003 Location: USA Posts: 108	You should also check out that link's parent, http://www.desy.de/pub/www/projects/Physics/. It has a lot of very good information and links there.

01-21-2003, 04:50 PM	#75
cfgauss Regular Member Join Date: Jan 2003 Location: USA Posts: 108	Friar Bellows: My examples are perfectly fine! In F=ma, m is a constant for an object (are F and a equivalent for an object?); in F=kx, k is a constant for the spring (are F and x equivalent for the object?); in E=mc^2, c is a constant for the universe! If you want some more... 1-Cos(x)^2 = Sin(x)^2, are sin and cos the same? For a right triangle, leg^2 + leg^2 = hypotenuse^2, are they the same? And like I said, when you use E=mc^2 like that, you're mixing measurements from different frames, which you can't do! E=mc^2 for an object not at rest is E = gamma mc^2 = (p^2c^2 + m^2c^4)^(1/2). http://www.desy.de/pub/www/projects/...y/SR/mass.html There are several "theories" (that don't do much at the moment) that say c may've changed in time. There're experiments that seem to indicate this, too. And I'm always right .

01-21-2003, 06:32 PM	#78
cfgauss Regular Member Join Date: Jan 2003 Location: USA Posts: 108	If you're in a boat moving down a river, does your perception of it matter? No, it doesn't. You are regardless. Is your perception related to it? Generally. Does that mean anything? No.

01-21-2003, 06:49 PM	#79
Jesse Moderator - Science Discussions Join Date: Feb 2001 Location: Providence, RI, USA Posts: 9,908	cfgauss: If you're in a boat moving down a river, does your perception of it matter? No, it doesn't. You are regardless. Is your perception related to it? Generally. Does that mean anything? No. I don't understand what you're getting at with this response. Do you agree or disagree that our perceptual arrow of time owes itself to the thermodynamic arrow of time, and that the explanation for why the two arrows are related is at least somewhat nontrivial?

01-21-2003, 06:55 PM	#80
cfgauss Regular Member Join Date: Jan 2003 Location: USA Posts: 108	Well, why do we think we're moving down the river in the boat? Because we are. That's the relation, no more. It's trivial.

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