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## Comment Re:Photons and solar wind (Score 1)163

That's a bit misleading, although technically correct in the center of momentum frame. In general the relativistic energy is obtained from the length of the 4-momentum m(vx, vy, vz, mc^2) which gives the oft-quoted E=mc^2 for a mass that has no motion relative to the observer. But for a massless particle (which according to the theory must move at the speed of light in every frame), E=Pc .

So more accurately the Sun loses mass to produce light but the transfer to Earth involves only energy and momentum. Absorption by the Earth increases the velocity of bits of matter which results in a corresponding mass increase.

## Comment Re:faster than light never violates Relativity (Score 1)226

Yes, the direction of the time axis is as observer-dependent as is the rotation of spatial axes. In Cartesian geometry the distance (dx, dy, dz) between points depends on the choice of coordinate system, but the length of that 3-vector is always the same (compared to the distance between some reference pair of points)

Similarly in space-time it is only the length of the 4-vector between events A and B that can have any physical meaning. This length can be positive, negative, or zero. A positive length means the events are outside each other's light cones ("space-like"), thus have no causal influence on each other. A negative length ("time-like") means each could have participated in the events leading up to the other.

A zero-length ("light-like") means there is no event separation between the two, i.e. they are the SAME EVENT (this might be understood as length contraction in the direction of motion going to zero when v=c). All the points on A's light cone (which includes B) are the same event as A. All the points on B's light cone (which includes A) are the same event as B. So far there is nothing to determine the direction of time, and indeed the physics describing the transfer of action when v=c is symmetric with time.

But there are points Z on A's cone not on B's cone and these are also part of the same event AB even if they also have space- or time-like separation from B. Even if nothing can interrupt the ZAB event, the direct ZB distance could be time-like and thus set a direction of time, B before A. If B was a causal factor for A, it is difficult to see how ZAB could not be affected by the the direct BA interaction. It seems to me, here is the collapsing wavefunction. The only way I can reconcile it, is to introduce some time average long enough to allow all these paths to interact.

## Comment Re:Plot Hole (Score 1)179

At the crucial moment Frodo could not destroy the ring! The long trek was needed to bring about the fight in which Gollum reclaims the ring and then, in his exhaustion, falls with it into the crevasse.

Also Sauron was distracted by all the fighting and uncertainty caused by the rumors of the ring being carried around.

## Comment Re:Straight to the pointless debate (Score 1)136

NASA did destroy a large amount of imagery in the 1980s, despite a public outcry I certainly contributed to. The official line was that no one knew how to read the warehouses full of 7 track tapes to for conversion to CD (the 2400 foot tape could store 5 to 140 MB depending on density). The obvious reason was no one wanted to spend the money to replace all the classified pixels with innocuous ones. And so mankind lost a large amount of wealth.

## Comment Units were chosen for the conclusion? (Score 1)409

Can't be bothered to read TFA, and got a life-threatening yawn scanning the overly complicated rebuttal.

Dollars of carbon offsets vs. megawatts of installed capacity is mostly a measure of the average capacity factor during operation, possibly adjusted by the fossil fuels needed for maintenance but that is way beyond this level of analysis.

Capacity factor is something like 20% for solar (5 full sun hours most days), 40% for wind in a favorable location, 95% for nuclear until something bad happens In the end if they all have the same cost per installed MW then nuclear wins. If solar had 5x less installed cost then it wins, similarly for wind at 2.5 less.

## Comment Re:Christmas is coming early this year (Score 5, Insightful)702

Such a bomb could well house a small battery for detonation, big enough to also power the device for a short time for the trigger swipe. Rejecting devices that don't work is absolute insanity.

## Comment Re:Engineering win (Score 1)262

But no net energy that way, just pointless multiplication of PV panels. If you want a energy return equal to the energy that went into making the first panel, the first 5 years is a loss - all it does is produce a panel. If you produce no more panels after that it takes another 5 years to recover the energy you could have used 10 years earlier to do something useful. Only after that is net energy. Some of the net energy can be used as a new source of useful energy, the rest to produce more panels and ultimately as the energy source to develop a Dyson sphere. When you stop building panels, it's all net energy.

## Comment Re:Engineering win (Score 1)262

Energy Return on Energy Invested (EROEI) of PV can be 3-4 in favorable cases but the rate of return is also important if you want to multiply the resource. If energy parity for the first panel takes 5 years then its output could produce a second panel in another 5 years. So for 10 years you get no net energy, after which you can tap some of the output for other uses while still continuing to add panels at an accelerating rate. Doesn't matter if you start with 10 or 10 billion, there is still no net energy for 10 years. Starting with a large number could cause energy shortages and social unrest which could end the sustainable growth entirely.

Yes, we should have started 20 years ago.

## Comment Re:This always ends well.... (Score 2)76

As always, there is plenty of free and superior course material. The real graft is at whatever level can issue the mandate that the latest and priciest must be used. Nothing but the best for our children, etc.

## Comment Does anyone look at ads anyway? (Score 1)355

I have script and ad blocks and bogus host file entries to speed up browsing but can honestly say I don't pay attention to ads when they get through, When looking for something to buy I do the search and find it hard to believe unsolicited ads bring in any customers.

Are there really people who click through and buy something because an ad says they need it?

## Comment Re:The image formation process is still the same (Score 1)60

That's the infinite plane wave approximation for lattices of infinite extent. Scattered spherical waves from finite objects will result in some energy passing through the aperture for every spatial frequency. Although it could be difficult to sort out which frequencies are contributing (aliasing). Analysis of the through focal series can do that, also changing the convergence of incident illumination.

But if the source is known to be two points, accurate measurement of the spacing between the resulting PSFs is limited only by signal to noise.

## Comment Re:The image formation process is still the same (Score 3, Insightful)60

Yes, and what's more diffraction causes no fundamental limit to resolution, it just happens to be the distance between the first zeroes of an interference function. For two point sources of equal intensity that leads to an easily seen contrast difference of around 25% but trained observers can detect 5%. On electronic displays the contrast can be cranked up arbitrarily.

The fundamental limit to resolution is signal-to-nose.