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Comment: Saving Earth's resources? (Score 2) 243 243

As about one fourth of world electricity consumption is used for lighting purposes, the LEDs contribute to saving the Earth's resources.

Efficiency does not mean lower consumption. Efficiency remains a useful goal but not "to save the planet's resources". The latter can happen only if overall consumption is reduced. What will happen is that as electricity used for lighting purposes is consumed less, it will get cheaper to direct it elsewhere.

Comment: Re:Black holes are real, we observe them all the t (Score 1) 356 356

Maybe he should have meant the following version which seems very counter-intuitive:

Suppose you wrap a string around the Earth's equator so that it fits tightly. Now suppose you add an extra meter in the length of that string. Surely, the string won't be tight anymore. So pinch it at a point and pull it upwards as high as you can. (Now, the string goes tightly around most of the earth, and forms a triangle elsewhere with the apex being the point you pinched and pulled.)

How high this apex would be from the surface? The answer turns out to be well over a hundred meters. See Image 1

(Apart from the actual number, the surprising part is also that the bigger the initial object - earth here - the higher you can pull the string even though you add the same extra length of 1 m in each case.)

Comment: Re:Read the whole article (Score 1) 136 136

Also, either the author of the article has a listening comprehension problem or the assitant professor quoted in the article has a reading comprehension problem.

Look at Turing's original article. It says that the imitation game is played between a man (A), a woman (B), and a player C. C has to decide among A and B who is a man and who is a woman. Now, the _man_ is replaced is a computer and we ask if C will perform as well or poorly as before.

So in Turing's version we have a computer A pretending to be a woman to C, and a woman trying to convince C that she is the woman.

Turning's original test _does not_ have a man and a computer pretending to be a woman to a judge.

Comment: Re:the joker in the formula (Score 1) 686 686

There are 7 billion people on earth but only one tallest person. Clearly the odds of finding a tallest being on any planet is 1:7_billion.

The point of parent is that if the intelligent "us" were not us, someone else would have evolved to be as intelligent. You can argue that point but don't argue probabilities based on 1 out of however many being intelligent. Two intelligent species would have competed and one would be killed off so far in earth's history.

Comment: Re:Fascinating, terrifying stuff is news (Score 1) 358 358

Do you realize that the whole point of the GP's "exercise" was that you can't ignore relativity? It is due to relativity that the time observed by the traveller would be so little. If you are travelling at a velocity very close to the speed of light, in your own frame time is essentially standing still. You would get to your destination before you could blink your eye.

Now redo the calculations taking time dilation into account.

Comment: Usual /. (Score 4, Informative) 82 82

The summary (and the headline) unnecessarily highlights space travel as a usage for radiation pressure and delegates the most interesting part as a footnote-ish last line. The /. crowd as usual starts shouting pros and cons of space travel, as if every comment on this page is not saying what has already been said a million time around here, and nobody to talk about the interesting part.

I wish someone with the right background in physics posted something more interesting about the fact that a group of researchers have come up with prediction of how a non-quantized spacetime (gravity) would look in the presence of quantized matter/energy. Apparently this would look different than a quantized background with quantized foreground (IANAP, so I don't know what is this all about) in a measurable way. If they can levitate a tiny but macroscopic mirror using light and balance it then giving it a gentle push would create a pendulum with no friction slowing it down. By probing the frequency evolution one can potentially get closer to actually knowing whether a quantum theory of gravity is the right way to unify QM and GR.

It's fascinating that such things are possible even in principle with existing technology. I wish someone would explain something more related to this.

Comment: Re:Clueless (Score 1) 80 80

I don't think so.

Stability of ordinary matter is well explained by other more traditional theories (strong/weak forces for nucleus, electromagnetic for atoms and molecules, gravity for even larger structures). This theory described stable states that initially no one believed existed.

Morever, these configurations are stable but quite fragile.

Comment: Re:Clueless (Score 5, Informative) 80 80

I found the summary confusing but the article made more sense.

The theory was that there exist configurations of three particles that is stable in a strange sort of way. The strange part is that if a certain configuration was stable then putting the particles in the same configuration but the distances blown up by a certain factor (22.7 if the three particles were the same) gives another stable configuration. So you can keep blowing up the distances in multiples of 22.7 and would get an infinite sequence of stable configurations. These configurations are necessarily quantum and not classical since the distances involved would be much larger than the range of the forces between the particles. (Although even the initial distances are large too, if i understood correctly, you would agree that they _will_ get pretty large at some point).

Now some independent groups have shown the existence of such states with the required blowup. Since similar-particle setup required cooling things down to the limit of present day technology, only _one_ configuration was observed initially. Someone used a system of different particles resulting in a blowup factor less than 22.7 allowing them to observe _three_ of these configurations, essentially validating the theory.

Hope that made sense (IANAP).

Comment: What increases the risk (Score 2) 172 172

I don't think anyone is implying that we are doomed because of _these_ impacts.

However, in general the frequency of an impact event is inversely proportional to the size of the impacting body. Smaller impacts happen more often than the larger ones. Counting the smaller ones precisely gives you an idea of what the risk of a big event is.

So far people underestimated these smaller ones that is being reported. The wikipedia article I linked to earlier, suggests one impact every five years at the level of 5 kT of TNT. These guys being right would imply a risk of at least a magnitude higher than previously estimated. That increases the risk for the really big ones too.

Comment: Re:I know what you're thinking.. (Score 4, Informative) 77 77

A black hole would dissipate via Hawking radiation only if it doesn't absorb more energy than it emits. Large blackholes absorb more energy (cosmic background radiation) than they would emit and hence will not necessarily dissipate. From wikipedia:

"A black hole of one solar mass has a temperature of only 60 nanokelvins; in fact, such a black hole would absorb far more cosmic microwave background radiation than it emits. A black hole of 4.5 × 1022 kg (about the mass of the Moon) would be in equilibrium at 2.7 kelvin, absorbing as much radiation as it emits. Yet smaller primordial black holes would emit more than they absorb, and thereby lose mass."

Comment: Re:Completely wrong post at +5 Insightful (Score 1) 172 172

Slashdot moderation sucks.

It used to work better when there were fewer stories on slashdot. These days the front pages gets updated at such a rapid rate that I suspect a big chunk of readers with mod points going past just a few comments in any one story. If they keep jumping from story to story then faulty moderations are bound to go uncorrected for relatively long times.

Give it a while though; residents of the internet wake up at different times :)

There must be more to life than having everything. -- Maurice Sendak