Slashdot Mirror

Kirk? Wait a minute, you aren't Roykirk? Too much IMPERFECTION

Nomad .... wait .... ZZZZZap

This is why, in terms of English, weight is treated as a scalar... because we always know which two bodies we're talking about, and which one's weight we're measuring relative to the other. In other words, if we're talking about the weight of some body on earth (and we usually are), we know that the weight is toward the earth so we can just leave that part out. Incidentally, we also know, roughly, the gravitational acceleration between the two bodies, so we tend to ignore that, too, and just treat weight as a measurement of mass... which it is, if you just go to the trouble of doing the simple math to throw away a constant and ignore an obvious direction.

You're right, the Earth does weigh 150lbs. on me, in physical terms. In English terms, that's an absurd image, as "weight" is generally assumed to be the property of a smaller object with reference to, say, a planet. So there I was debating English. But I still debate your contention that physical "weight" is bidirectional. It's just a measurement that can be taken from either side with the same result. :)

Interesting point. This reminds me of a Star Trek episode.

In the Copenhagen interpretation the act of observation changes reality as opposed to revealing some part of reality that was previously known. An electron will behave differently depending on what you know about it.

What spike? The spike in what? This is physics, be specific

When you measure a quantity (Energy, momentum, voltage, there's lot of them) where the wave function is a Gaussian distribution, for example, of different values (of Energy, momentum, whatever) your measurements won't show a Gaussian distribution of that quantity -- even though that's what your theory says is there -- rather you'll see a range of values for that quantity with most of the measured values in a spike where the wave function collapsed. According to the Copenhagen interpretation, the wave function collapsed due to the act of measurement. According to the law of large numbers the wave function collapsed because of the way you analyze and process the data from your experiment.

Unfortunately, that site seems to be for non-experts who also understand all kinds of crazy math, of which I don't even know the name.

As far as I can tell, the Fine Structure Constant can't be explained without recourse to big mathematical things. It's just one of those things that's easier to describe in its effects (as an earlier poster has done) than to give an explanation of what it is.

Ok, I'm mathematically ignorant but I'd like to know more about how they simulate these things -- in an educated layman's terms. Wouldn't two galaxies colliding be the n-body problem from hell?

Slightly OT, but the Zeta function, in addition to being of significance to primes is important to astronomy. That's because to derive the thermal emission from eg. a star as a function of Temperature you need to integrate the Planck Blackbody Function, which gives Zeta(4) = pi^4/90 The result is known as the Stephan-Boltzmann Law

Slightly OT, but the Zeta function, in addition to being of significance to primes is important to astronomy. That's because to derive the thermal emission from eg. a star as a function of Temperature you need to integrate the Planck Blackbody Function, which gives Zeta(4) = pi^4/90 The result is known as the Stephan-Boltzmann Law

More correctly, the presence of a changing magnetic field requires the presence of an electric field, and vice-versa.

Aside for people who've taken calculus based physics: If you remember the Maxwell equations, you should remember that there are four of them: two of them tell you how static charges give rise to E and B fields, and two that tell you how moving charges give rise to E and B fields, and additionally, how a time-varying E field gives rise to a B field and vice-versa. See, for example, Eric's Treasure Trove

Furthermore, there are some points about Faraday cages that you are missing: firstly, as another poster mentioned, any holes will reduce the effectiveness of the cage. Secondly, even a very good cage only keeps out static fields; time-varying fields penetrate into cages to a degree that depends on their frequency. For this, you'll need to check out an advanced undergraduate or graduate E&M text (such as Jackson). This is why, for instance, you can listen to the AM radio while riding in your car, and why you can talk on your cellphone inside an elevator (which are generally excellently well closed Faraday cages).

Light's kinda weird. It has a small but greater-than-zero momentum (not really mass, but momentum). Momentum must be conserved, so momentum from the laser is imparted to the target, and it's this momentum that causes the damage. If the light is reflected then the momentum imparted to the target is even larger, because it needs to not only stop the light but also impart the same amount of momentum in the other direction. The amount that the momentum imparted causes the target to move or deform can be used to determine the force imparted. Since the area that the force is acting over is known, you can find the pressure. Thus, light has pressure. For more info I recommend Eri'c Treasure Trove of Physics. Try starting here.

Mr. Spey
Cover your butt. Bernard is watching.

Indeed! In the real world, you can't win, can't break even, and can't quit the game....More technically (from Eric's Treasure Trove of Physics):

• First Law: energy is conserved - change in internal energy come from changes in heat and work done on the system.
• Second Law: entropy doesn't decrease
• Third Law: at absolute zero, entropy tends to a constant; for crystalline solids, that constant is zero

Yep the speed of light is exactly 299,792,458 m/s in vaccuum. A second is defined as the time required for 9,192,631,770 vibrations of a Cs atom. Read about it here

http://mathworld.wolfram.com/ had a robots.txt file at http://mathworld.wolfram.com/robots.txt (now changed) that forbade spidering of the site except by a few specific search engines (including Google, which is why they have its pages cached). Not only that, but there was a legal page at the site that explained that any IP address that downloaded pages in bulk would have its entire subnet banned. You could not mirror this site. I don't think anybody has an offline copy of it.

The original robots.txt file was identical to this one. Also see this similar legal page.

http://mathworld.wolfram.com/ had a robots.txt file at http://mathworld.wolfram.com/robots.txt (now changed) that forbade spidering of the site except by a few specific search engines (including Google, which is why they have its pages cached). Not only that, but there was a legal page at the site that explained that any IP address that downloaded pages in bulk would have its entire subnet banned. You could not mirror this site. I don't think anybody has an offline copy of it.

The original robots.txt file was identical to this one. Also see this similar legal page.

Are we doomed to live out all these plots from the original series, or just those authored by Gene L. Coon? If so, I suggest we just skip to Shore Leave. But let's agree to get rid of Finigan early on.

Are we doomed to live out all these plots from the original series, or just those authored by Gene L. Coon? If so, I suggest we just skip to Shore Leave. But let's agree to get rid of Finigan early on.

Sorry, you're correct: specific heat is energy required to raise a certain amount of a substance a given temperature. Thermal conductivity is the amount of heat that can pass through a substance in a given time. The two are related, but not the same. It's been a long, long time since I've taken chemistry. :)

Sorry, you're correct: specific heat is energy required to raise a certain amount of a substance a given temperature. Thermal conductivity is the amount of heat that can pass through a substance in a given time. The two are related, but not the same. It's been a long, long time since I've taken chemistry. :)

The _real_ problem is that you will eventually have a completely uniform universe, (maximum entropy) which means that there isn't a way to harness that energy.

On another note, it is interesting to note that we may already be in a black hole. If you look at the average mass density and size of the observable universe (which is about 10 or 15 billion light years in radius) and plug them into an appropriate formula (say here) then the universe has the gross properties of a black hole (the right size and mass). (It's important to note that size or mass completely describes a non-charged, non-spinning black hole).

So, falling into a black hole might suck (pardon the pun :] ) but living in one might be ok.

Actually, it's not a theory, it's Einstein -Podolsky-Rosen, which was recently proved as a law of quantum mechanics with a neat little experiment...
In a nutshell, EPR implies that in an entangled state, certain particles would seem to violate local reality by "agreeing" on their quantum state, with no perceptible particle exchange (which means it's not limited by the speed of light), even when separated by great distances.

The problem is, for now, that we have no way of predetermining quantum states in entangled pairs, meaning we can't yet use it for FTL data transmission. But it is the principle behind quantum teleportation, which is unspeakably cool.

ObKomputerGeek->Relevance: Information stored in quanta has some freaky properties.

> Inverse Symbolic Calculator
> http://www.cecm.sfu.ca/projects/ISC/

Argh. NOW I found out about a home site, after I graduate. *sigh*

Another great site is Eric's Treasure Trove of Science
http://www.treasure-troves.com/

Cheers

[The exclamation point after 100 is mathematical notation for factorial.]

Like the article says, Wiles solved a special case of STW to knock off Fermat's Last Theorem. I guess this is a proof of the general version (but the article is a little vague--any number theorists around who are in the loop?)

• on Eric's Treasure Trove of Mathematics
• H ow it relates to FLT
• Several link on FLT and STW
• If you're at a University or otherwise have access to the American Mathematical Society's MathSciNet, there are a couple of papers

I read this a couple of days ago, and understood several of the words involved. Further reading, with decent enough explanations, can be found here.

I keep trying to convince my coworkers of this, but they refues to listen.

Funny. I would have thought that would be easier to grasp than the fact that the cardinality of the set of rationals = the cardinality of the integers = the cardinality of the squares of the integers etc etc.

But then, you still have to convince them that the cardinality of the real numbers (the continuum) is in fact unknown... :)

Although the number 1 used to be considered a prime (Lehmer 1909; Hardy and Wright 1979, p. 11), it requires special treatment in so many definitions and applications involving primes greater than or equal to 2 that it is usually placed into a class of its own.

I read "somewhere" that 1 isn't defined as a prime partly for this reason: that each integer is said to have a unique prime factorisation

Seems like it. I guess they got tired of saying "x holds for all primes except 1" that they excluded it :-)

The unique factorisation thing is the Fundamental Theorem of Arithmetic.

--
Repton.

http://www.treasure-troves.com/ math/EvenNumber.html is a good math dictionary and agrees that zero is even.
--