Physics

Actually I believe it is a case of, the more accurately you know a particles velocity the less accurately you know its location.

It had something to do with the device being used to measure the velocity would affect the particle more if more energy was used to determine its velocity... or something along those lines.

Oh, and I don't think its quite applicable to your speeding ticket.

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And on another point.

*** is it with all these science questions - I thought this was a highly technical PC forum, not an advanced physics forum.

OK, so people find the topics interesting which is cool, but the forum is now dominated by these kinds of threads.

Moan over.

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Originally posted by Arcanum

And on another point.

*** is it with all these science questions - I thought this was a highly technical PC forum, not an advanced physics forum.

OK, so people find the topics interesting which is cool, but the forum is now dominated by these kinds of threads.

Moan over.

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Sorry about the extra stuff Arcanum. I fell to the same mistake when I posted the Theory Thread a long time ago and it was vanq--moved to Gadgets and Gizmos. The thing is though, this site may be in fact well known for topical questions somewhat encompassing computer related topics and I have mentioned it to the odd person(s) who excel in the physics field themselves. Good for extra traffic in any case. At least it doesn't produce massive flame threads on a regular basis...

You have a point though.

Low frequency wavelengths dusturb the velocity of a particle less. However, the longer the wavelength used to observe a position of a particle the greater the uncertainty of it's position.

High frequency wavelengths disturb the velocity of a particle more, but you have better certainty of it's position.

Since the wavelengths from a radar gun are very unlikely to disturb your car's position I don't think you have a case.

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Originally posted by Arcanum


And on another point.

*** is it with all these science questions - I thought this was a highly technical PC forum, not an advanced physics forum.

OK, so people find the topics interesting which is cool, but the forum is now dominated by these kinds of threads.

Moan over. [/B]

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A little off topic discussion is acceptable, and phyiscs/math type stuff is in the spirit of this forum. I am doning my best to keep it confined to a few threads though... :)

It is rather impressive the knowledge that some of the members have :)

There haven't been any interesting computer architecture/technology threads for a while though, which is a shame but I guess that nothing much is happening right now.

Ions can be measured with the electromagnetic field. So we can narrow their position and velocity down to a very small scale.

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Originally posted by elimc
Ions can be measured with the electromagnetic field. So we can narrow their position and velocity down to a very small scale.

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Interesting. Pardon my newbness, but is this a theroetical extrapolation or an actual test in working progress right now?

If you think about what the uncertainty principle says,

the product of the uncertainty in momentum and the uncertainty in position can not be less than h/(2*pi)

That's an extraordinarily small number.

IT's possible to be very sure about a position and momentum at the same time, but impossible to both precisely.

http://www.colorado.edu/physics/2000...quations/h.gif

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Originally posted by GARRIN19:

Interesting. Pardon my newbness, but is this a theroetical extrapolation or an actual test in working progress right now?

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This is my personal guess. Even then, we couldn't know the exact position and velocity of an ion because we can only "ping" the ion at the speed of light. But it would be very close. However, not all subatomic particles respond to the electromotive force (like neutrinos).

A bit of nuclear weapons history I never understood:

In WW2, the German nuclear weapons program uesd heavy water (water in which there are more than usual of hydrogen's heavier isotopes, deuterium and tritium). What was it used for, as I would assume that they weren't making H-bombs before fission bombs?:confused:

"OK, so I was pondering life's little nagging questions, and this occurred to me...

As you're aware, the Heisenberg Uncertainty Principle teaches us that it is impossible to know a particle's velocity AND it's location at the same time...you can determine one or the other, but not both. Granted that this is true, how can a police officer claim to have sufficient grounds to issue you a speeding ticket? If he claims he knows how fast you were going, he can't say that you were actually there...if he says you were, there, he can't say he knows how fast you were going. "

Ok, Motoman, here's your answer, but you've opened up a bigger can of worms than you may realize:

Unfortunately for me and my last speeding ticket, as someone said before, the amount of uncertainty is somewhat small. But more importantly, the amount of uncertainty DECREASES as the mass of an object INCREASES. This should be obvous from simple proportions that a .1 inch error in a position for an object .01 inches long is huge compared to a .1 inch position error in an object 1 inch long. These are made up numbers and a simplistic approach, and the vagaries of quantum mechanics make the actual implications for extremely small particles pretty bizzare, but you get the idea. The wave/particle duality of light is an example of the weirdness of quantum mechanics, but I won't go into explaining that at the moment (most should know at least the idea).

In any case, the fact that quantum mechanics breaks down for large objects means that it has little effect on that cop's radar gun output. On a scientific level it also means that the two great theories of physics, on which most of modern technology is based, are essentially mutually exclusive - they contradict each other and can't both be right. One is quantum mechanics of course, and the other is Einstein's relativity. Relativity works exceedingly well for very large objects and quantum mechanics works exceedingly well for very small ones. When each is applied to the domain of the other, neither work. The last great challenge in physics, indeed one of the capstone achievements of science, would be to find a theory that unifies the two - the "Grand Unification Theory." The search for this theory is what is driving the leading edge of physics.

Probably to create an experimental nuclear reactor would be my guess. I live next to a nuclear reactor and these materials are central for a fission power plant. By the way, I think that heavy water is something like H^3O. Quite simply, heavy water is heavier than regular water.

I remember reading a story about a whiz kid in middle school who wrote a paper on how to make a nuke. He went to the library and got all the info from books on the shelves and extrapolated the rest. He also built a model to show how it worked. This was in the 70's

It was so good, FBI came and interrogated him. They couldn't believe a kid could figure it out and all the information was available at the public library. He handed over his bibliography and stunned them Scientists reviewed his work and agreed if built and stocked with fissionable material - it would have detonated easily enough. The kid got an A. He probably works for a gov lab now. lol

Heavy water is still H2O, just there are more hydrogen nuclei with either an neutron and a proton (deuterium) or two neutrons and a proton (tritium) (a normal hydrogen nucleus is just one proton).

To expand, heavy water is used only in fusion. So the nazis must have been researching fusion. I doubt they got very far with it though.

A lot of excellent questions here. But a lot are metaphysical and easily answered with a little logic. And others have a general scientific consensus....

"When did time start?"

Since time is a property of the universe, it started when the universe was created/came into being - about 13 billion years ago (by earth time).

"Is space never ending?"

It is generally belived that according to Big Bang theory that the universe is finite and without boundary. It is exactly like that circle or the surface of the earth. When you view a circle in one dimention, it has no beginning or end but a definable length (circumference). When you view the earth's surface in 2 dimentions it has no starting point but a definable surface area. 3 dimentional space has a definable volume but no beginning or end.

If by "never ending" you are referring to time, see the first question for the beginning. For the end, one possiblity is the never-ending cycle of bangs and crunches, expansion and contraction. The other two are continuous expansion, and a steady state where it ceases to expand but never contracts. To answer that, we need better information on the quantity of matter in the univers, hence the gravitational effects on the expansion.

"Where did space/time start and what was before that?"

Space/time started at the big bang and "what was before that" is an oxymoron. If there is no time, there is nothing to be before it. The only possibility is the idea (not testable, so not a theory) that "before" the big bang there was a big crunch - and a never ending cycle of expanding and contracting universes.

"where did we come from?"

Most scintists would say that the simplest organisms appeared out of the "primordial soup" then evolved into us.

Is there a god?

Thats not a scientific question, so not answerable scientifically. It is also by definition not possible to disprove the existence of God. So its up to your own personal belifs.

Also, the key to the circle question is the same as the second question above about the boundaries of the universe. If you view the circle in two dimentions it has a length and width (both the same, so expressable as simply diameter). But if you look at it in ONE dimention, it has only length.

[somehow this post ended up in the wrong thread. Sorry for any confusion.]

much props to russ on that one ;)

Heavy water is only used in fusion? Where I live, the tritium is actually leaking into the rivers from the waste tanks, but I don't think that we have ever made hydrogen bombs or tested experimantal fusion reactors.

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Originally posted by elimc
Heavy water is only used in fusion? Where I live, the tritium is actually leaking into the rivers from the waste tanks, but I don't think that we have ever made hydrogen bombs or tested experimantal fusion reactors.

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i think we will have an experimental fusion reactor up soon in sellafield, uk.

I meant where I live there have never been any fusion reactors or H bombs made (I believe). Yet we have tritium seeping into our water from waste tanks.

Some extra comments from a maths/physics major.

Einstein proved 'beyond reasonable doubt' that space and time are linked within the fundamental nature of the universe. There WAS no 'before the universe'. This comes under special and general relativity. As a side note ALL of our laws of physics and understanding of them come are themselves dependent on the universe itself (obviously!) We therefore can not test anything that happens outside our universe by any current or likely means. We can only speculate.

While the universe is currently expanding, no one really knows what the fate of the universe will be. It may either shrink into a 'big crunch' or expand forever. This area is under intensive research as it underpins a great deal of our understanding of the universe.

For those of you who believe in God here understand that God, if he exists, created space and time. He must exist outside of time rather than as a part of it. You can't really say 'he was the only thing that was back then' because there was no time. He must be well and truly beyond any mortal comprehension.

OneWayTraffic.

P.S. It is really HARD to talk about this properly as English depends on concepts like time being unscrewed up!

I gotta agree with you OneWayTraffic. If God is of outside the universe (as all definitions of a god present it to be) then our laws of physics wouldnt apply to it, at least not exclusively. How can you describe unfathomanable things? What does a monkey think about a 747 flying overhead, or of a PalmPilot when given one? Cliff Pickover does some thought experiments on what a being of a 4th dimension could do in our world . Entertaining, thought provoking material (which Pickover excels at) that you can get lost in, until you remember you gotta pay the bills :).

hmm....don't know how that post about symbols got here, that was meant for the math thread. anyway....

Tritium is the active ingredient in fusion bombs. But elim, now that I think about it (and you mentioned it), I think heavy water is also used in the reactor vessel of a nuclear plant. The extra neutrons aid the fission proccess. So the nazis could have been using it in fission research. BTW, tritium is one of the most toxic substances known to man. But hey, it looks good on a watch face.

Also, yes we have fusion bombs - they are called hydrogen bombs since hydrogen is the element that is fusing. Fission bombs only produce explosions of a few kilotons because of the difficulty in separating such a large mass of fissable material. You have to have chunks of fissable material just under critical mass. The higher the yield, the more chunks and the more difficulty in keeping them separate then recombining them. In Tom Clancy's "The Sum of All Fears," he goes into excruciating detail on the makeup and functioning of nuclear bombs. In a hydrogen fusion bomb, the fission trigger is only 10-20 kilotons, but can ignite fusion of a few megatons yield.

edit: Just as a basis of comparison, the bombs dropped on Japan were on the 10-20 KT range. So the hydrogen fusion bombs that we have can be as much as a thousand times more powerful. Kinda scary, huh?

Also, yes nuclear fusion is being researched for power. Princeton has the largest facility in the US. They have a working nuclear reactor, which is to say nuclear fusion occurrs - for a few miliseconds at a huge negative efficiency. I belive CERN (the center for european nuclear research) has one, as does Japan. I'm not sure what they are doing in England.

Engineers and physicists seem to agree that a practical fusion plant is still 50 years away because of containment and efficiency problems. The essential problem is twofold - to ignite fusion you need extremely high temperatures, millions of degrees F. This takes power and makes containment of the material difficult since no material on earth can withstand temperatures like that. So they use magnets to contain the hydrogen plasma, which is why the reactors are in the shape of a dounut magnetic field. The only promising alternative is using lasers to ignite the fusion, but I'm not sure how that is going.

There was recently some interesting news in the field of fusion.
'Tabletop' Fusion Report Elicits Mixed Reaction

Quite a creative approach to it. It may not be all that promising, but it is nice seeing people think different.