swansont

You can have an ensemble of photons that have the distribution of a blackbody. One can talk of their temperature, which is really the temperature of the object emitting/absorbing them, in thermal equilibrium. We speak of the 2.7 K temperature of space, which is determined by the distribution of photon energies.

Which definition of "censorship" are you using? I see absolutely no evidence of any censorship going on here.

OTOH, it's been my observation that people who make more money generally tend to rank higher on the cheapskate scale.

There's about a dozen users in the banned/suspended list, over the course of more than 7 months. You can see that with rare exception, the banned users appear multiple times, and suspensions generally don't occur until several violations have been made (except for the unforgivable infractions). There are users who believe the staff are too lenient in handing out the infractions and sending abusers to troll-heaven. As iNow has guessed, the purpose was to both inform the users that something as being done about posters that were disrupting threads, and to lend some transparency to the process, lest anyone think the actions were arbitrary or unwarranted. You can look up users, read their "contributions" and judge for yourself, should you be so motivated. If anything, newbies might get the impression that I'm the Bad Cop™. I can live with that.

Butter-flavored gelignite?

Or we color it with language to spin it the way we want. You could have said "… like Boy Scouts," or "… like fraternity/sorority members" ————— There was a time when people in the US did service for their country, as tvp45 has mentioned. You got compensation, but it was less — possibly far less — than what you might get for two years at a job in the "real world." Other people have made, and continue to make significant sacrifices to allow people of today to enjoy what they have. The amount of squawking about requiring community service, not military service, and certainly not two years' worth, is just sad, IMO.

You really can't play the insulted card if you call someone a jerk, with or without the smiley. And the threat to leave the board carries little weight — either you do or you don't. Bringing it up multiple times quickly becomes unpleasant noise. Stick to the physics, please.

The deduction is up to $4000, and is "above-the-line," i.e. in addition to your itemized or standard deduction, according to the link I had provided. So can be about $1000 off your tax bill if you qualify. Then there are the two tax credits. Anyway, I looked at the IRS pub, and the current deductions/exemptions cannot be taken simultaneously. Why would the new one be any different?

Wow, even Nature has the ability to post almost-content-free material. I expected better of them. The mention "Hogan's ideas" without explaining what they are, like a few paragraphs are missing from the article. Now, what does this have to do with Rovelli's article?

I had come to that conclusion even before this.

If they didn't, and you could apply all deductions and credits, then you could get something like $8500 to attend a year of community college, where tuition is usually below $4000. And that's insane. I'm assuming you will be limited to an either/or situation. If it isn't, then hell, I may enroll in a night-school class.

Yep. That's the basic idea behind it.

I saw that the context was QG. I think there's little need for all of the preamble. He could just explain why quantum gravity would best be served without a time variable, but the context of this is "the nature of time" so one has to wonder how much of this is localized to the QG framework.

Fission, not fusion. I mentioned this above — here's more detail. You have a water-moderated reactor, and as water heats up it expands, reducing the ability to thermalize the neutrons before they leak out of the core. U-235 has a much smaller cross-section for higher-energy neutrons ("fast" neutrons), so the only appreciable fission is from neutrons that have become thermal. Fission heats up water, and the hot water is how one delivers energy to the turbine, subsequently cooling the water down. If the electrical demand goes up, more energy is taken from the water and it cools further, making it more dense. This, in turn, means neutrons are thermalized more efficiently, which boosts the fission rate. Hence, the power of the reactor naturally responds to the electrical demand. Should the water boil away, or there was a leak, you would not be thermalizing neutrons, and the fission rate would drop to a very low level. This design supposedly does not have a problem with fission products escaping if the temperature gets pretty high, so there would not be core damage in such an instance.

33.3 picoseconds in a cm (1 cm/3e10 cm/s)

There is already a tax deduction for tuition*, so presumably this would replace it, meaning the net change in tax burden is less than $4k per student. And better than a flat-out tax credit or deduction for tuition, since the country accrues some tangible benefit from it in addition to having educated citizens. edit: *currently there is a deduction and two types of tax credits http://collegesavings.about.com/od/taxbreaksforcollege/a/deducttuition.htm

Been there, done that. Small reactors tend to have negative reactivity coefficients. If the water heats up, the fission rate slows because more neutrons leak out. Power naturally follows steam demand, because as the load goes up the temperature drops, which causes an increase in the fission rate. Do the flow with convection and there are no moving parts in the primary. But a turbine is definitely a moving part, though it's not part of the reactor, per se.

Right, he's saying that we never measure time at all, since we're measuring some physical process. [math] \omega = \frac{d\phi}{dt}[/math] (I blogged about this today, though the motivation for doing so was unrelated to this thread) We attempt to measure the phase in order to tell us the time, t. So Rovelli is right — we never actually measure t. But when you find the mass of an object, are you measuring the mass, or are you measuring a force that indirectly measures the mass? His objection is an artificial one. All he appears to be doing is saying "get rid of t and use [math]\phi[/math] " But that's just semantics. You haven't really removed time from the problem, you've just renamed it. The whole field of metrology is trying to measure constants and realize standards. None of them can be done perfectly, so I fail to see why time should be singled out on the basis of imperfect clocks. There's no Galilean master length, either, because of relativity, so that can't be the criterion for tossing the idea of time.

Exactly. You can't prevent people from forgetting anything they might have learned for a class, but the exposure, overall, has benefit.

I think that's my largest objection. People who, despite swearing an oath to preserve, protect and defend the Constitution, insist on placing the Bible above that.

Rovelli's; III A. Back to Galileo and Newton, end of first paragraph. He appears to be complaining that a clock measures time and presenting it as a circular argument, rather than it being by definition.

I agree. I think the notion that college students might be working their way through school is being overlooked. I don't think that portraying it as charity is necessarily apt. You could be picking up garbage in a park or on the highway.

Actually we don't. Gammas come from nuclear interactions. You can have X-rays with higher energies than gammas. Probably not Radio waves, though.

Gammas generally have higher energies, because they come from nuclear interactions which stem from a stronger coupling, so they almost always have higher energies than the interactions that give you radio waves.

An object moving in a circle must have a force exerted on it to follow F = mv^2/r If that force is the weight, i.e. v^2/r = g, then the bucket cannot be exerting and force. But what happens if the bucket is swung faster? Or slower?