swansont

The "wall plug efficiency" of laser diodes is pretty high, as is the gain in the lasing active region. For higher-power diodes you have to anti-reflection coat one of the facets otherwise it literally blows the end of the laser off (degradation of the AR coating leading to this is one of the causes of death for laser diodes). When it does, it still acts as a diode, just no round-trip gain, so there's a glow at whatever color the diodes gives. There are even higher power diodes that are tapered so that the power density doesn't get too high, and these are basically single-pass devices. Used as lasers they don't tend to have narrow linewidths because they don't have round-trip amplification, but you can also use them as injection-locked amplifiers. The two black boxes halfway down the table on the right side in this picture house tapered amplifier diodes. 500 mW output each (~ 10-20 mW in)

For US pennies it was 1982 that they switched from 95% copper to copper clad with 97.5% zinc.

In addition to what Tom Mattson has said in response to this, great pains are taken to shield precise clocks from effect such as these. Time dilation is not a mechanical effect on clocks. It is an effect on time.

No, that's not what I'm saying, and strawmen usually are nonsense. I'm saying that if an apple ripens in 5 days, and you went away on a trip at sufficient velocity to account for 5 days in time to the apple, but the trip was very short for you (say one hour), when you came back the apple would be ripe. By your watch, one hour had passed. By the apple, and the clock sitting next to it, 5 days had passed. The timekeepers in the two frames will not agree, even though when they are side-by-side, the second hands are observed to tick at the same rate, and they were reading the same value at the beginning of the trip.

I haven't read the book, so I can't say for sure. IN GR there is also an energy-momentum tensor, aka the stress-energy tensor.

I thought it belonged to his wife

There will be a time difference between them, even when they return to operation at the same frequency. They are not in the same time frame.

The comparison of what you'd see and what somebody else sees is a change in the question. As long as you restrict yourself to two observers under inertial conditions, what you'd see would be symmetric, since either one of you could claim to be at rest. A third observer would see something different. But nobody would see you go faster than c under any conditions.

If you are going at a speed of c/3, it is possible for you to go at 2c/3, with respect to some frame A. The velocity addition formula comes into play when there is an additional observer/frame. If you were travelling at c/3 and doubled your speed to 2c/3, with respect to frame A, you would not have doubled your speed with respect to some other frame B that is not at rest with respect to either you or A. That's why I said your original question was poorly framed - it did not distinguish between a specifically chosen frame or an arbitrary frame.

Yes: "GR is difficult."

There's an energy-momentum 4-vector, comprised of E and the three spatial components of pc. The scalar product with itself gives you E2 - p2c2, which is the square of the rest energy.

The question is poorly framed. What do you mean by "no matter what reference frame?" There will always be a reference frame with which you may double your speed, since you can always define a reference frame that is travelling at less than c/2 with respect to you. But you cannot say this about any arbitrary reference frame.

No.... Did the company lose money selling you the smoke detector, due to the cost of the gold?

UT1

Yes, he was here. I wasn't able to attend the colloquium, even if I had wanted to. I did check with some people and I was basically right. No matter what you do, the translation between an earth frame and a celestial frame requires earth orientation information that must be measured (using distant quasars and interferometers) because it cannot be modeled. Even though the rotation of the earth frame and the celestial frame are supposed to be related linearly through UT1 (earth time), UT1 is not predictable!

Except that it's not really new. Rutherford did similar work 70 years ago. The new part is the pyroelectric crystal to give you the accelerating voltage.

I do know something about economics, but more importantly, I can usually recognize BS whan I see it. And I'll leave you to wallow in your leavings.

It's more than assuming. The particle is in both states.

They're defined in the link. v is the speed of frame B with respect to A. u is the velocity as seen by A, and u' is the velocity as seen by B.

You need to build out the solar infrastructure, and I've read critiques that claim that the cost of that is prohibitive under the current market conditions. Solar electricity is just too expensive at this point.

It's not the viabilty of the vehicles as much as the fact that hydrogen from electrolysis does absolutely nothing to decrease our dependence on fossil fuels, since you have to use fossil fuels to make the electricity to get the hydrogen. That's the first law of thermodynamics. And due to the inefficiencies involved, you have to use more energy to make it than you get back. That's the second law of thermodynamics.