swansont

The hanging block has two forces on it: the tension and force due to gravity. Why should it accelerate at g? If T = mg, the block will not accelerate at all! And to accelerate at g, it is necessary to have T=0, which is not the case. Consider the motion if the top block has a mass of 10,000 m. Would you expect it to accelerate very fast?

Ah, but this effect should not be ignored. The ability of a material to transfer heat is very important in this scenario. The metal will feel hotter even if it is at the same temperature as the air. Consider this: would you place your hand in an oven that was at 175 ºC (350 ºF)? Would you grab a casserole dish or cookie sheet that was in that oven? In equilibrium, they will be at the same temperature if they are blackbodies. A material with a high heat capacity will take longer to get to equilibrium.

No, there appears to be senescence. That's a strange definition of "immortal," though. I think the original premise is fatally flawed, ironic as that is.

Some emergence/holism is pseudoscience. Not all scientific investigation is reductionist. But if you want to make an upper-level connection, you have to investigate it rigorously. It's the lack of rigor that is viewed with disdain, AFAICT.

Which is the motivation behind asking for a risk assessment. The conundrum of building a robust system is that unless you could make the components redundant, you would need a whole bunch of spare capacity to accommodate a failure of that component.

Right answer, AFAIK, but the reasoning is incomplete. Gauss's law tells us we can treat extended masses and charges as points, but there are exceptions: if the distribution isn't uniform, or we aren't outside of the volume. So a mass or charge distribution, as long as it's uniform, behaves just like a point for r>R. When you have a nonuniform distribution is when you have to have to worry about the spatial extent. That's when you make the assessment of size of effect vs distance, because it drops off like r^-3, i.e. faster than the force.

From a physics standpoint they are equivalent. Which is damn convenient sometimes, because you can often choose a frame of reference where the math is easiest.

Yes, it matters. Equation 1 gives you the speed of the rocket (and bolt) at the 4-second mark, as you've already suggested. We don't know how high the rocket went, but we know that however high it went is also the distance the bolt has to fall. Try writing down equation 2 for the rocket and for the bolt. Since delta-x is the same, you can set them equal to each other.

Coulomb's law assumes point charges — this allows you to do a single calculation for the force between any two charges. Having to worry about the spatial extent of a charge complicates calculations and in most cases the effect is small, which means the effect can often be ignored. In the case of the electron, as far as one can tell when trying to determine if there is a charge distribution, it is a point charge.

Indeed. One must wonder how CO2 avoids absorbing radiation near 4 and 15 microns. http://chriscolose.files.wordpress.com/2008/03/image001.gif

Which is now this thread, because there's no need to start a new one to talk about the same topic.

Then let's define our scenario more carefully. In inertial frames, observers not moving with respect to each other, at the same altitude, will see clocks running at the same rate. If one observer (the traveller, T) is moving with respect to another (the mountain, M) each will see the other's clock running slow. In this situation, a third observer will not see T and M as stationary with respect to each other — they will be in different frames. At "time frame" is the same as an inertial frame at a given gravitational potential (altitude). If they are not at rest with respect to each other, they are not in the same frame.

I believe you have overestimated the grid capacity and underestimated the losses (efficiency of transfer). Excessive transport loss is one of the arguments I have seen against remote solar, so both claims can't be right. In the US, insufficient grid capability is a serious concern. Do you have any sources that support your claims? Also, adding more turbines to a dam may not be possible or result in additional energy. Storage capacity is a function of stored water volume. Power is a function of number of turbines.

Not sure where you're going with this. Gravitational time dilation isn't normally associated with escape velocity.

Seems to me that the Republicans' definition of compromise in this case is "agreeing to everything we want"

S-orbital wave functions, for instance, don't vanish near r=0 as quickly as some others, and the nucleus is not a point. So the electron will spend some of its time in the nucleus — if you were to localize it, some of the measurements would have it inside the nucleus. Electrons will not hop from one orbital to another with a different energy unless energy is added (or removed) from the system (and if we're discussing a ground-state system, the electron can't drop to a lower energy). So no, it won't go to a "higher orbital" away from the nucleus. (remember, an orbital is not the same thing as an orbit)

"Striking" is not the same as "good" — you want to stay away from gaudy combinations that make the eyes bleed after a few minutes. Some powerpointers on how NOT to do it http://scienceblogs.com/twominds/2008/03/how_to_give_a_bad_science_pres.php http://scienceblogs.com/grrlscientist/2008/09/how_not_to_use_powerpoint.php http://scienceblogs.com/worldsfair/2008/09/is_this_the_most_evil_powerpoi.php

Silly, perhaps, but it's also how nature behaves. If you are moving relative to me, I will observe your clock to run slow. All you can say is the person and the mountain were moving relative to each other. You can't say which one is moving — the laws of physics work for both of them, and do not have a preference for either one. As insane_alien has stated, there is no preferred frame. Doesn't matter if you "buy into" it or not. That's not the metric of validity.

There is uproar in the Mac community. Gruber at Daring Fireball has been railing against it, for one. If an app can be rejected for nebulous reasons, developers won't invest time in writing the apps. And cool apps would be an enhancement of value for the iPhone. http://daringfireball.net/2008/09/podcasters_rejection http://daringfireball.net/2008/09/app_store_exclusion http://bits.blogs.nytimes.com/2008/09/16/apples-capricious-app-policy/

It depends on the question of whether a photon experiences time, which we've discussed http://www.scienceforums.net/forum/showthread.php?t=34872 One problem being that much of the justification for the statement relies on relativity, which is valid for inertial frames. But a photon is not in an inertial frame.

I'd like to see a comparison between the energy loss from transmission and the energy it would take to make and maintain the liquid helium/hydrogen for the superconductors. Along with a risk assessment for the inevitable failure of one part of the grid.

We need truth-in-advertising to be applied to campaigns. http://blogs.scienceforums.net/swansont/archives/801

This is just a guess, but there are a couple of factors here: High schools are generally starved for science teachers, so geophysics vs physics shouldn't be much of an issue, and you will probably have to take enough physics for a geophysics degree that high school teaching would not be an issue at all — you likely wouldn't teach anything beyond calculus-based general physics. College becomes more problematic, since you would likely be competing with physics degree holders, and PhD no less, for the teaching positions. "Do what you love" is my advice.

"Tax" and "income tax" are not the same thing. There are payroll taxes, too, that are paid by people who end up paying no income tax. Apples and oranges.

I will add: unless you are actually connecting from your cellphone, "textspeak" is not considered to be polite communication. you, not u