Sisyphus

I'd also be interested to hear more actual physicists' opinions about various popularizers. For example, how do you feel about Einstein's own writings as a basic guide to relativity? Are the Feynman lectures hopelessly out of date yet? Which guys, to use some Wikipedia slang, are "POV-pushers?"

That's how water gets in lakes and rivers in the first place. Of course, the sunlight collecting surface area is the entire surface of the world's oceans...

1. Actually, they don't. The spiral shape seen in some (but not all) galaxies is a result of a higher concentration of younger, brighter stars in that pattern, which makes those areas brighter. But the shaper of the galaxy itself is still a disc. The pattern itself is caused by a kind of "density wave" analogous to a traffic jam. As stars and other material enter those regions, they are slowed by gravity, and the higher density of interstellar gas leads to more stars being formed. Material passes through and continues its orbit, but the "traffic jam" itself moves slower and is left behind. 2. They attract each other for the same reason that all material objects in the universe attract one another: gravity. 3. If galaxies pass near one another, the gravity of each will distort the other, much like the moon's gravity distorts the Earth (that's what tides are), but moreso, because galaxies are more fluid and less coherent than planets. If they actually collide, they'll either merge if they weren't moving very fast relative to one another and thus can get snared by one another's gravity, or if they are moving fast they'll just pass through one another, trading some of their stars and getting their shapes greatly distorted on the way.

They also have the highest percentage of people of any nation who believe in evolution. And they're consistently rated as among the "happiest" nations on earth, by various standards. And they're also apparently fans of (weekend) binge drinking, casual nudity (north of the arctic circle!), and bizarre conceptual art and music. Also elves. The relationship between these things I can, unfortunately, as of yet only speculate about it. Not only that, but there's glaciers, volcanoes, and the midnight sun. I've never been there, but I would love to go.

http://www.theonion.com/content/news/recession_plagued_nation_demands

Given the choice, you wouldn't. But if you want to drive more than normal commuter distances in one day, it becomes necessary. Most people hardly ever drive that long, but hardly anyone never does. That's what I was thinking, too. But even that would come with it's own set of problems. Electricity is electricity, but if you're routinely swapping out heavily used batteries, quality control could be a nightmare. I wouldn't be at all surprised if we do see something along these lines, though.

It's not (IMO) deliberate social commentary because as a culture we've reached the point where that "message" is no longer necessarily a political statement. To use a more extreme analogy, there was a time when showing a married, employed, female character on television would have been considered a radical feminist statement (and it still would be in many parts of the world). However, in 2008 in the United States it doesn't even occur to most people that it might be controversial. While it is true that there are still plenty of people who think "a woman's place is in the home," and that the the writers and producers of that television show almost certainly hold certain basic values in disagreement with that, that doesn't mean they're making a deliberate point.

Clearly there are certain values on display in the movie, but that doesn't mean it's propaganda, or even a deliberate message. I got the impression that the people at Pixar, like me, didn't think the "message" would even be controversial. Don't get so caught up in instant gratification that you ignore the consequences, nor so self-absorbed that you can't connect with other people, nor so complacent that you forget to explore life. "Oh my god! Liberal fascist propaganda!" Please. The National Review types are just upset because the movie takes as an accepted premise that we, through unchecked and unexamined consumption, can cause serious damage to the environment as a whole, a premise that they, in ever-shrinking numbers, are still thickheadedly dismissing as mere socialist propaganda despite all evidence to the contrary. The times, they are a-changin', and you better stop swimming, or you'll sink like a stone.

Here's a rather amusing summary of the various ridiculous controversies. The bigger firestorm seems to be not about making fun of obesity, but about the environmentalism themes. Apparently, it's all liberal fascist propaganda! In all seriousness, though, this is probably the best-crafted movie of the year, and certainly the most adorable robot yet conceived by man.

I don't think a blanket solution like that would be feasible, especially at the federal level. For one thing, rooftop solar is only worthwhile if the roof actually gets a certain amount of sun. You wouldn't put panels in a forest (or other shady location), or on a north-facing slanted roof, or a north-facing hillside, or places like Alaska. I would rather see: 1) Economic incentives, rather than mandates. I don't think they'll even be necessary as solar gets cheaper and more efficient, but they could help. 2) Municipal-level codes. It might actually be feasible on that level in certain places. I'd even be happy with specific deals with local governments, to account for circumstance. "Want to build that housing development in our town? Make your proposal energy self-sufficient and sustainable, and we'll talk." 3) More local projects (as opposed to regional or individual). A "town wind turbine," for instance, would (I'm guessing) be much more economically efficient than little ones on every roof, you'd still get most of the benefit of local generation (less electricity lost in transmission), and there wouldn't be the massive red-tape and such to overcome with huge, regional plants.

You're right that the upper limit for energy efficiency is necessarily going to be lower for biofuels than for solar. However, it's not necessarily true that there isn't enough room. For corn, soy, sugar cane, or any of the current common crops, you're right. But algae-based fuel produces thirty times the energy per acre, and we could, theoretically, power the whole world with it. Not that we should, necessarily, but we could. From that article: "The United States Department of Energy estimates that if algae fuel replaced all the petroleum fuel in the United States, it would require 15,000 square miles (40,000 square kilometers), which is a few thousand square miles larger than Maryland, or 1.3 Belgiums.[4] This is less than 1/7th the area of corn harvested in the United States in 2000.[11]"

Interesting to imagine how that would happen, though. If it's just enough spin to overcome gravity at the equator, then only a narrow equatorial band of material would actually fly off, right? The rest would just deform, flatten out into a more oblate spheroid. I guess if it happened suddenly there's no way anyone would survive, but after everything cools off and settles (in a few million years or so), you'd be left with a very peculiar planet, no? The image is so strange that I feel like I must be missing something important.

On a related and fairly hilarious note, it seems the Iranians have been manipulating images of their missile tests, and a widely circulated image today is actually a fake: http://thelede.blogs.nytimes.com/2008/07/10/in-an-iranian-image-a-missile-too-many/index.html?hp Four missiles instead of three: a 33% bigger saber to rattle? Some New York Times reader comments, from the blog: "One more missle and it could have been an AT&T Wireless Ad for "more bars in more places".” “They also removed the"TONKA" label on the truck out front. The whole thing was a set of model rockets five inches in length, and a wider shot would have revealed a man standing just out of camera range nearly as tall as the smoke.” “I know that these missiles are part of a threat to wipe Israel off the map, but now they've proved that they have the Photoshop capabilities to do it.”

Again, not that it matters, but instantaneous velocity ("at a point in time") is still defined as the ratio of distance traversed to time expired, just that the time is approaching zero. So no, it's not "zero." It's "infinitesimal," which means nonzero but smaller than any finite quantity. Put another way, it is the value towards which the ratio gets closer and closer as you reduce the "time" value more and more. Practically speaking, we generally don't bother thinking in those terms, but that's where it comes from, and it's closely tied with the origins of calculus.

He makes several good points, but I'm not too sure about his math. As for his "releasing a third" of the strategic oil reserves, that just seems very shortsighted. For one thing, a third of the strategic reserves is about a three week supply at current U.S. consumption rates. It would certainly lower prices for a while, depending on the rate at which its released, but necessarily not for very long, since there just isn't enough oil. All it would be doing was creating a "reverse bubble" in oil prices for a few months, screwing with a market that's finally created demand beneficial to our long term goals. And at the end of that period, you're more addicted to oil than you were before, the economy takes another hit readjusting to the once-more high prices, and your emergency reserves are 33% smaller. It would punish speculators who "bet against the United States" by crashing the market, but honestly, not really, since immediately after a price drop that you know will be temporary would be an ideal time to get into oil speculation. I also think he's being more than a little misleading with his comments about rocky mountain shale oil, etc. First of all, it's not "illegal to look for it there." We have been looking. Most of the theoretical supply is under federally-owned land, so there's not "a law against it," per se, any more than there's a specific law against me drilling on your property. Congress just has to approve individual leases. And they have already leased out several test sites to private companies, most notably Shell. Nobody, however, has committed to large-scale projects yet, because the economics of it aren't certain. They (the oil companies) want to be sure the global price of crude stays high, because otherwise shale extraction isn't economically viable. They were mining shale oil (or at least heavily investing in the infrastructure) during the last energy crisis in the 1970s, but when oil prices dropped in the 1980s it became obsolete, and they lost a whole lot of money. As for nuclear energy, though, I pretty much agree with him. In the medium to long term, it probably will and should be the foundation of a diverse energy production infrastructure. The more plants we build right now, the better off we'll be for the next few decades. I'm probably more optimistic than him, though, in that I have a lot of faith in the technological advance of "greener" energy to the point where even nuclear power has only a minor place. It won't be totally obsolete, however, until we have a better source that is independent of external conditions and can be built anywhere.

Yeah, that sounds more like an idea for classifying objects you already agree fall within the category of "planets." After all, an "atmosphere-less body" could be just about anything. Including me.

No, they're talking about gravitational pull changing as a result of change of position. As in, the pull is less high up in the air because you're farther away from the Earth's center of mass. I know: annoying.

I'm sure that in 1985, plutonium is available in every corner drug store, but in 1955 it's a little hard to come by.

(I'll be largely repeating myself, but I forgive you for not reading my original, very long post.) The thing is, it's not really defensive. In the crazy upside-down world of the nuclear standoff, it's ICBMs which are the defensive weapons. The only value of a nuclear missile is as a deterrent, but it's an extremely effective deterrent. We will not invade a country that credibly threatens to respond with nuclear force. That's why there was no World War III, and that's why nations continually threatened with superior force, such as Iran and North Korea, want nukes so badly. If, on the other hand, you actually use them, they have the exact opposite result: your own immediate guaranteed destruction. This is an inherent part of missile politics, but the "suitcase bomb" is immune, which is why that is the only credible threat. The converse to ICBMS being defensive, of course, is that missile shields are inherently offensive. If they work, then their only realistic effect is to neutralize a defensive weapon. That in itself is not inherently an argument against it, but it should at least be discussed in those terms. Carl Sagan famously compared the nuclear arms race to two men standing waste deep in gasoline, one holding three matches and the other holding five. It's a terrifying situation, but as long as everyone stays even remotely rational, nothing will come of it. An ABM system is based on the premise that one of those men believes he can make himself immune to fire, which changes everything.

It does certainly mess with MAD, which is why we had the ABM Treaty to begin with. Not only would it have unnecessarily tipped a perfectly functional balance of power, but its development by one side would have created a "now or never" situation in the other. Of course, that was during the Cold War, and many things are different now. Russia really has no rational grounds to object to a friendly nation defending itself, nor to expect even that that nation would take advantage of their new position to launch nuclear strikes on Russia. On the other hand, on an emotional level and in terms of prestige, it's extremely important. Russia is nowhere near the global power the Soviet Union was, but what does remain is the ability to push a button and obliterate entire countries within minutes, which at the end of the day is still the ultimate deterrent against aggression from foreign powers. Being nuclear capable means you don't need the best military to be secure in your sovereignty. That's why countries which are constantly threatened, like, for example, North Korea, Iran, or Israel, understandably feel the need to acquire such a deterrent. Taking that away from Russia is seen as akin to saying "we could destroy you if we wanted," which is taking away from them something very important in addition to being an insult. I'm not saying their anger is justified (particularly since the system, even if it worked perfectly, would be totally insufficient in stopping the full arsenal of Russia). To the contrary, I think they need to grow up. But that doesn't change the situation, and it helps to understand where they're coming from. And so the question, again, is how does an ABM system realistically change the game in today's world. (I'm assuming, here, that the thing actually works, which I understand is highly dubious). Well, it stops "rogue states" from launching missiles at us. But there's no way anyone was going to do that anyway, for several reasons. First, the whole point of having nuclear weapons is as a deterrent. They're useless if you actually use them, and furthermore will inevitably bring about your own immediate, spectacular obliteration. Any number of Dr. Strangelove quotes could appropriately be cited here. And second, there's no reason that any of these states would even use a missile. It would be far easier and more effective to bring it in Trojan Horse style - no ICBMs to build and hope work, no obvious target for retaliation, etc. Thus, it won't ever actually shoot anything down, and the only effects will be political, not tactical. And so, politically, is it a net gain? Well, Russia, whose cooperation we could sorely use, is furious. They have no right to be, but that doesn't change the fact that they are. So major minus there. On the plus side, nations who were building nukes as deterrents primarily against the United States and its allies might decide not to bother - with missiles. As mentioned earlier, it won't affect the more effective delivery systems. It also won't affect nations for whom the deterrent is from someone else, like Israel, India, or Pakistan. Or potentially even Iran, if they're afraid of Israel as well as the U.S. Politically, I'd say the net result isn't clear, but I'm leaning towards a minus. All that's left to discuss, then, is the economic cost. It's not much compared to the whole U.S. budget, it's true, but it's not exactly trivial either. It is, in one of the more unfortunate traditions of our military, a huge, expensive program that doesn't work right and pisses everyone off. It's classic, self-perpetuating military-industrial complex, the most tenacious virus even in a government full of self-perpetuating waste. The recipients of the pork grow rich and thus influential enough to keep it coming, and anyone who objects has to deal with a powerful lobby, economically addicted constituents, fear-mongering, and slander against their patriotism. I don't think that's the only reason for its existence - surely a lot of people in positions of power honestly believe its important - but it is definitely a major reason, and it gives me a headache to think about.

I don't know exactly what the evolutionary place of bat is, but it's definitely not a link like you describe. They're cousins, not ancestors. Their eyes, like everything else, are evolved for their own purposes. They can see, as CDarwin says, to varying degrees, and generally have as good vision as they can make use of, given their environment, diet, other senses, etc. What it's important to understand about evolved traits is that they won't appear if at any point their costs outweighs their advantages. And so you won't ever have an animal that suddenly develops useless eyes, nor will you really have an animal that has better eyesight than it really needs, because eyes are "expensive" in terms of bodily resources. That's why cave fish, which are descended from seeing fish, often evolve to become totally blind and eventually lose their eyes entirely.

I'll repeat the question, since I think it's quite relevant to this little tangent:

I don't understand what you mean by "cyclical" in this context.

That would make more sense than the university, wouldn't it? And what if they're not subject to free and fair elections? Are you implying it's not their business then? If not, then whose business is it?

These are some pretty controversial remarks.