April 24, 2004

• now, why did i think a graphic depiction of relativity would help me understand the theory?
• I don't think it's easy to understand Einstein's work until you have had it explained by an ape. Also, it helps to have very concrete examples.
• oh thanks, that really helps. i'll stay with the two hairs! if e=mc2 and all are variables but m, which by definition is a finite substance, then how does that one compute? i could never decipher the logic behind mixing substance and theory and coming up with an empirical equation. and einstein thought quantum mechanics was too unpredictable? ha! / good article in today's nyt's re: his last girlfriend's diary, by the way.
• The disc is half-full. The disc is half-empty. /Ambiguity, Great Geeking Goddess of Gigabytes
• pretty cool stuff. John Dillenger, of course, isn't dead. Kind of a random connection, I guess, but still cool.
• dxlifer: e=mc2: c is the constant. m depends not only on the object, but also on how fast it's going, as does energy (a moving ball has more energy/mass than a stationary one). Incidentally, do you have a link to the nyt article?
• The aforementioned link.
• The best way to think of the energy equation is E = square_root(m^2 c^4 + p^2 c^2), where m is the mass, c is the speed of light in vacuum, and p is the momentum. Thus mass is invariant (physists tend not to think of mass increasing as an object goes faster, these days). There are two implications of this. First, massive particles have nonzero energy, even when at rest (that is what E=m c^2 is all about), and when you "destroy" that matter, you release an amount of energy equal the mass time the square of the speed of light. The speed of light is a huge number (light is fast), so the square of it is fricken'-ass huge, hence nuclear bombs and giant flaming balls of light in the sky. Second, massless particles carry a momentum (this is a key foundation of my thesis research). As for dxlifer's question: A theory basically is an equation. The thing is that the equation must describe something physically. m, c, and E are all quantities that describe something. m is the mass of some object, c is the speed of light in a vacuum, and E is a quantity that we call energy. Now, you can measure directly the mass and the speed of light (sort of, I'm glossing over stuff here), but not the energy. Energy is something of a mathematical thing that makes physical explanations simpler. The kinky thing about this mathematical thing is that it can manifest in many different ways. For example, an electron at rest has an energy E1 = m1 c^2. Let's say an anti-electron (electron with the opposite electric charge) comes by and smacks into the electron. It has an energy E2 = sqrt(m2^2 c^4 + p2^2 c^2). Now, when an electron and an anti-electron collide, they produce a packet of light called a photon. The energy of a photon is defined as E3 = h f, where f is the frequency of the photon and h is called Planck's constant and can be figured out through experiments. If we assume that energy is neither created nor destroyed (we can come up with ways of testing this assumption and so far it has always held up), then we can say that the energy of the photon should be E3 = E1 + E2. Like I said, you can't directly measure E3, but you can measure the frequency of light (sort of, glossing over again), so h f = m1 c^2 + sqrt(m2^2 c^4 + p2^2 c^2). So now we have a way of figuring out one set of measurable quantities from another set of measurable quantities. Depending on what you are trying to do, you could use this equation to figure out what f should be, figure out how fast the anti-electron was moving (by calculating p2), or even test the conservation of energy (by calculating the frequency of light with the equation, then setting up an experiment where you have an electron at rest and an anti-electron with momentum p2 and measuring the frequency of the photon that is produced). In practice theory-making is a very messy process. The more fundamental theories can be derived directly from the physical laws (stuff like F=ma), but in complex systems, it's not always easy to figure out which physical processes dominate, or what assumptions are safe to make. There's a lot of back-and-forth between experimenters and theorists to figure out what works and what doesn't. Disclaimer: I'm about three months away from a PhD in theoretical astrophysics, but I don't think about these sorts of things enough and I probably said something wrong. On preview: Holy crap, this is long.
• who follows the empirical lie, falls prey to the medusa'a eye, the knower petrifies the known, the subtle dancer turns to stone. / that's my standard response to this kind of thing that simply doesn't fit into my personal method of interpretation. i was in social sciences. but thanks, dirigibleman, i did manage to sort out some understandable parts of your post to add to my partial comprehension. perhaps someday, i shall reconcile this theory with my own thoughts. now, since the activity of the brain is energy, can we apply the theory there? if that energy is indestructible, then we have resolved the 'life after death' quandry. let us know when you get the treasured phd, so we can share your exhaltation. such an accomplishment justifies great celebration. / how can something 'massless' have momentum? now i'm more baffled. i'll stick with archimede's principal.
• now, since the activity of the brain is energy, can we apply the theory there? if that energy is indestructible, then we have resolved the 'life after death' quandry. dxlifer, energy, from a physicist's perspective, it's just a msthematical concept that aids to understand the relation of causation between different physical phenomena. It has no real physical counterpart, but noteless it exists, sort of, like momentum, weight (not mass), angular momentum, pressure, drag, friction. It's just a quantity without any other kind property. So saying "the activity of the brain is energy" is actually redundant. All this activity inside of hte brain is actually the result from previous processes (metabolism) and it ends wasted in heat. So there's no real energy conservation in the brain, it's all wasted eventually. If you die it's because the brain, or the whole body for this matter, can process more energy (turning fats and sugar into something useful) anymore and all the useful energy it had was completely wasted as heat.
• That's why I love to say that all living things are no more than burning candles.
• now energy is just a concept??? no wonder i'm so tired. / nearing the end of her candle, *sigh*
• What I was trying to say, before my meal cooled, is that when speaking of energy, everyone uses it in a different way. So there's no use in trying to assume something about energy from what some physicist says when you don't understand the concept the same way he or she does. You can imagine I cringe everytime I hear someone speak of receiving positive energy from the sun or crystals. But I understand that what they take for energy is completely different from what I take for it.
• ah...so that proves that energy is not constant! at least in people's minds. i shall now feel free to interpret it according to the situation. thanks zemat. the truth has set me free.