The really important question is whether or not at the Planck scale one finds that we are all one really, really big version of Minecraft, being played by beings that look strangely like turtles. All the way down.

Another really important question is just how much of the world's creative potential is devoted to creating meta-inventions on top of rulesets intended for something else entirely rather than, say, bringing about world peace, curing cancer, feeding the hungry, or just plain moving out of your mom's basement. Not that I am entirely without sin in this regard myself, but it is a sad commentary on the state of the world (virtual or not) that we appear to live in when solving vast and pointless artificial problems in a virtual reality is more appealing than tackling the real and serious problems that surround us.

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*flog* *flog* *flog*

I didn't justify anything, on anybody's part. I pointed out a factual error, with a little commentary.

Settle down, Beavis.

That's not the death penalty: that's the after-death penalty. And it's the number one reason I would spit in the face of the Christian god, if there was such an entity to be spat upon. Nearly all of the ranting about the Christian hell is in the New Testament, so it's at least nominally part of the new covenant. And the new covenant consigns little children who haven't been baptised to eternal torture in fire. Eternal. With no hope of redemption or respite. Ever.

Eternity is a long long long long time, and fuck the god who created such a place as the Christian hell.

Rome was an outlier, in all ways. The typical Roman planned city was much smaller, and required only one aqueduct. No, they didn't treat their sewage, but they had clean drinking water.

I'll repeat my suggestion to DerekLyons: read David MacCauley's book City.

There's a book by David Macaulay called City, about ancient Roman cities and their water systems. You should read it. Mountain springs are not required. A river will do. The upper limit on capacity as designed by Romans was typically about 50,000. Actual city populations were undoubtedly higher than that, but that was their planned capacity. Yes, it takes repeating the Roman cookie cutter method quite a few times to accommodate all 2 billion, but the ancient Romans were already in the habit of duplicating their method repeatedly, because it worked so well. It's quite well adapted to being repeated over and over again.

And those 2 billion people have nothing more important to be doing than securing a clean water supply. You don't need slaves when you have 2 billion with exactly one first priority.

I'll echo the anonymous coward: I wasn't alive when that law passed locally. And add my own observation: had I been alive, I haven't always lived here. I've lived lots of other places too. You expect me to have control of local matters in 22 different places? (Yes, 22. That's how many different local jurisdictions I've lived in.) When I've had no control in any of those places, ever, because I'm not as rich as you apparently are to be able to buy the local city council? Nor am I rich enough to run the kind of propaganda campaign required to get enough of the apathetic locals to give a shit about something that hadn't even left labs yet. There WAS no Internet when those laws were passed.

So I'm supposed to be a millionaire clairvoyant who has never moved in my entire life, according to you.

Fuck you, you arrogant asshat. With the federal government. Sideways.

Don't be ridiculous. There are lots and LOTS of things that can stop a bad guy with a gun that aren't a gun at all. At least some of them are available in almost every office. I bet getting stabbed in both eyes by a pen would stop pretty much any bad guy with a gun.

You don't even have to get that brutal, though brutal always works. One bad guy with a gun at the bottom of a pile of 20 guys is pretty well stopped, and not one of them has to have a gun to do it.

No they're not. Romans is in the New Testament.

One of the other responders commented that Christians use the Bible to justify anti-gay bigotry, and usually reference Leviticus when they do. They could as easily reference the New Testament. That passage from Romans maintains the death penalty for gay behaviors, for disobeying parents, for worshiping idols, and for oathbreaking, among other things.

So you're/they're saying mass-energy in any form doesn't have a "weight"? Einstein was even wronger? Rearrangements at constant mass-energy can have different weight? At the Planck scale you can say pretty much anything you like and not have much chance of your words being falsified, and while I'm not a falsificationist and agree that a consistent hypothesis can have meaning even if it can't be verified or falsified, this falls into the same scientific category that magnetic monopoles do, only tens of orders of magnitude worse. At least in the case of monopoles, I can understand all sorts of observationally true sequellae -- like charge quantization -- and they should be easy enough to observe subject only to their Bayesian prevalence and looking in the right places with the right tools. It wouldn't surprise me in the least if magnetic monopoles are eventually observed, adding a really, really important building block to our incomplete TOE. But in the meantime, I accord them only a weak degree of belief because I cannot rule out from a near infinity of hypotheses human have not thought of -- yet -- alternative explanations of the same sequellae that don't involve monopoles and because it becomes increasingly difficult to explain why we haven't observed at least one monopole yet unless there is some truly enormous energy barrier or symmetry breaking that we do not understand.

So I think that there is a very reasonable chance that monopoles exist and that physics completes in that general direction and that we'll eventually be able to take that "chance" (far too weak to call a "true fact") and turn it into a probably true fact through observation. I think that there is almost no chance that the hypothesis that entanglement alters weight at what amounts to the Planck scale ever gets any experimental validation either way. In its own way, it is like hypothesizing that dynamics at that scale is all due to neurotic invisible fairies. Which is, of course, very nearly a perfect metaphor for quantum field theory anyway.

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Hmm, is that true? Granted that many of the water molecules in my body have been inside many, many living animals and passed through one way or another, surely there are (a LOT of) water molecules being made and unmade every day through ionic dissociation. It might be more accurate to say that every atom of H and O in your body has been through a creature, but not necessarily bonded into water. Then there is "new water" produced when primordial hydrogen or methane are oxidized. Finally, I haven't done the statistical mechanics of it, but the ocean (or total volume of existing water) is pretty big, turnover is pretty slow, diffusion is even slower -- I could believe that a significant fraction of "old" water molecules (or the old constituents of younger molecules) in the world haven't been through an animal yet, and of those a few are making their first pass through me. But that's difficult for me to visualize well enough even to do a Fermi estimate of the probabilities, certainly not before my coffee.

The real problem is dissociation of water into H+ and OH-, followed by the formation of H_3O+ and OH-, followed (quite rapidly) by recombination into H_2O with (probably) different H, though. When that happens (and it happens all the time and rapidly in ordinary water) it is almost certain that the H+ that leaves a water molecule in one second is not the one that rebonds to it a moment later, so water molecules have a comparatively short half-life as a unitary identity, two specific H's and one specific O have been one specific water molecule for less than a day (models indicate order of 10 hours). So in that sense, almost none of the water in my body has been in the body of any other animal, as little of the water I drink was in another animal within ten hours of when I drink it, and even it it was, if it persists in my own body for a single day very little of it is still the same water at the molecular level that it was when I drank it.

In the end it is as useful as noting that we are all stardust, that is to say, the excreta of a dying star. That too is more poetically true than literally true, but it sounds way cooler than saying that we are all made of shit (starshit or otherwise:-).

And yes, we suffer from the same dissociation problem. I am not the same me (in terms of physical constituents) instant to instant as I'm a large, complex, organism and the worldlines of all of the matter that is arguably "me" for at least some brief time if "I" am defined either in terms of chemistry or some physical envelope are a whirling blur around my macroscopic worldline, constantly being spun into my envelope and then spinning out again, with every thread tied to the threads of many, many other living beings by the will of the Norns. Quite a romantic picture, even though sure, the bulk of the ins pass through my nostrils and mouth and the outs pass through many channels including anus and urethra.

So I think I'll stick with stardust woven by the Norns, not a pile of recycled shit.

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Sure, and consider that we do not yet have direct experimental confirmation that antiparticles fall down, instead of up. There's a reason for that, and it is 30 orders of magnitude.

The antiparticle experiment actually might be doable. And it is the thing that is a mere 37 orders of magnitude short of measuring the difference in weight of entangled quantum antiparticles.

So yes, you are right, one cannot be certain that there is no supremely clever way to measure Planck-length scale phenomena without using experimental probes with the energy of a freight train per particle and so on. What we can say with certainty is that at this particular moment, there is no justification for the use of any "measurable" variation of weight. No, there is no measurable variation of weight in particular, and probably no measureable variation of mass. The same laws of quantum mechanics that produce the supposed entanglement make it impossible to measure things at that resolution on a particle scale.

Now, if you could entangle whole planets, or even entire cats, matters might be different. I'd suggest building a scale and put Schrodinger's diabolical apparatus (plus a volunteer cat) onto it. Tell us what you measure regarding the difference in weight of the entangled vs non-entangled cat, bearing in mind that measuring weight is measuring so don't be surprised if the cat's state is collapsed to the classical one of live or dead but not both while you perform the measurement.

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Excuse me? E^2 = p^2c^2 + m^2c^4 is the correct statement (or to be pickier, the four vector P = E/c - \vec{P} has conserved length equal to mc). Photons have zero mass, so for them E^2 = p^2c^2. You are thinking of E = \gamma m_0 c^2, which works fine for massive particles where m_0 \ne 0, not so well for light where \gamma = \infty because light travels at the speed of light.

BTW, does /. grok latex if one wraps it, that is, does $$E = \gamma m_0 c^2$$ work? Might as well try it...

No, apparently not. I suppose I'll have to look at actual documentation to see if there is any way to make it work.

Hey /. Dudes! You keep changing the site, improving it and so on! A 21st century website that cannot speak latex is so, not-even-20th century, and when that site is devoted to technology, it is vaguely insulting. Even wordpress can often understand $latex E = \gamma m_0 c^2$.

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You saved me from having to reply. I do not think that this "measurably heavier" means what you think it means (or rather, they think that it means), to quote Inigo Montoya. Let me 'splain. No, there is too much, let me sum up. In addition to the fact (as you have so ably pointed out) that we will never, in the future course of the universe, be able to measure the effect predicted, it is a theoretical prediction based on assumptions in a particular circumstance. If the assumptions turn out not to be correct, it might not be any more correct than the assumptions. And since we will never, ever, ever be able to verify the prediction of measurable changes in weight -- where I am pretty certain that they meant to say "mass" and not "weight", since the former is an intrinsic property of particle configurations and the latter describes the macroscopic Newtonian force between two objects where traditionally at least one of the two is rather large, say a planet or a star -- of two quantum entangled microscopic particles in a Universe where the other forces acting on them are tens of orders of magnitude larger under pretty much all circumstances, we cannot even use this to demonstrate the empirical consistency of the unproven theory.

I'll have it done by lunch time, as long as the lunch is held in the restaurant at the end of the Universe, which I will get to via an infinite improbability drive using the plausibility of measuring the difference in weight of quantum entangled states.

Oh, one last thing. Everything is in a quantum entangled state. Literally everything. All of the time. After all, there is no "outside" of everything to perform a classical measurement and force the system to disentangle. Something to think about, while contemplating the Nakajima-Zwanzig equation -- for the Universe:

http://en.wikipedia.org/wiki/N...

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And the ancient Romans figured this out, and solved it.

It does not require the massive infrastructure that starts with Western toilets to solve this problem. It can be done with wood and stone and gravity, assembled using nothing more than muscle power. The fact that 2 billion people (with far more muscle power at their disposal than the ancient Romans ever had) haven't speaks volumes about the 2 billion people.