Follow Slashdot blog updates by subscribing to our blog RSS feed


Forgot your password?
Check out the new SourceForge HTML5 internet speed test! No Flash necessary and runs on all devices. Also, Slashdot's Facebook page has a chat bot now. Message it for stories and more. ×

Comment Re:Recursion is dead! (Score 1) 600

While a JMP is equivalent to a goto, keep in mind that conditional loops are a higher-level language construct than what is available to those early processors, which kind of means that JMP/goto had to be used everywhere on those systems. In my personal experience, having written spaghetti code with goto, and also having written vastly less tangled code without it, I'm quite aware of the software-maintenance benefits of avoiding goto whenever it is easy to avoid. But I'm also aware of situations, usually involving getting out from the inside of many nestings of conditions and loops, where goto is clearly the simplest and most elegant way to do that, and I will unhesitatingly use it for that purpose. Those situations are uncommon enough that its use need never be called "excessive".

Comment Re: Now can we (Score 1) 334

Thank you for all your feedback. I will note that it was claimed (not verified) that metallic deuterium had been produced in the Z machine. I'd prefer to wait until the claims are no longer dispute-able, and then see what they find out about the properties of metallic deuterium. Regarding high-energy muons, what you wrote is not what I've read, unless you consider a close-orbiting muon to be the same thing as a high-energy muon. However fast they move when produced, they slow down enough to displace an electron orbiting a deuteron, and then they catalyze fusion with another deuteron (and they can actually do that quite a few times, perhaps as many as a hundred, before they decay from their 2-microsecond lifespan --I should mention that one failure mode, for multiple fusions, is failure to acquire enough energy from the fusion event to escape orbiting the new helium nucleus; have you ever wondered exactly how a muon, not participating in the Strong Nuclear Force, can acquire the energy to escape orbiting the new helium nucleus? My hypothesis offers an explanation for that...).

Comment Re: Now can we (Score 1) 334

| Orbitals get arbitrarily close to the nucleus as is.|
That statement cannot be very accurate, for electrons, if it is possible for muons to orbit 206 times closer (which it most certainly is).
| you can find a discussion of fusion cross-sections in the intro chapter of many plasma textbooks |
I'm thoroughly aware of that. And now you are forgetting the factor of kinetic energy. In a hot plasma the kinetic energy of electrons is very high, while that kinetic energy is much smaller at room temperature. This makes a huge difference in how "spread out" an electron can appear to be, in terms of Quantum Mechanics. It means that in a hot plasma, while an electron can easily approach a nucleus at high speed, it also must leave at high speed, and the probability is LOW that another electron will be nearby enough, or moving in the right direction, to replace that first fast electron. But at room temperature lots and lots of electrons in the conduction band of a metal are quite widely-enough "spread out" to make it easy for one electron after another to get in-between two deuterons that happen to be approaching each other --the relatively slow loose electrons are attracted there, remember!
In the hot plasma, because there is no significant duration of cancellation of the mutual repulsion of two deuterons by a fast electron, they don't keep approaching each other, and they behave as is well-known in a hot plasma. But at low temperature, when one electron after another can easily get in-between a pair of deuterons, cancellation of their mutual repulsion can allow them to approach more closely than usual. The hypothesis is that they might be able to approach closely enough to fuse. (The hypothesis also states that they have to be randomly on an almost perfect collision course, which is very different from muon-catalyzed fusion --the muon has enough mass to influence a deuteron's course of motion, helping it get closer to another deuteron.) I'm not about to outright state that electron-shielding will allow deuterons to approach closely enough to fuse, because I know it is just a possibility that relatively cheap/simple experiments should be able to test --especially if they can now make metallic hydrogen (the claim was quickly disputed by other scientists, but Slashdot never posted that story).

Comment Re: Now can we (Score 1) 334

| This is flat out false |
Not false. Your response is subliminally talking about electrons in fixed orbits, not loose electrons. But I am talking about what loose electrons can do.
| the electrons do not just sit on the nuclei |
For "hydrogen in general", the electrons are in fixed orbits, and that's why they can't approach the nucleus arbitrarily closely. For loose electrons, they can approach the nucleus, but they cannot stay there because of the Uncertainty Principle. But when there are lots and lots of loose electrons available, any electron that must leave the close vicinity of a nucleus can be (temporarily) replaced by another. And when two nuclei approach each other, the place of greatest electrical attraction, between both nuclei and a loose electron, is the place midway between the two nuclei.
Finally, density is an average thing. It is perfectly possible for two nuclei, among many approximately holding an average distance apart, to approach each other more closely than the rest. Just like there is a bell curve of molecular kinetic energies with respect to the temperature of something, there is also a bell curve of average distances between nuclei, with respect to density. For ordinary hydrogen, with its very low percentage of deuterium, the probability of fusion is simply two low, most of the time, for it to happen when two random nuclei approach each other. But two deuterons have a much greater probability of fusing ---are you aware that Jupiter is reported to have a slightly higher temperature than it "should" have, based on its age and distance from the Sun? Rare fusions of deuterons in its metallic-hydrogen layer could be happening, sufficient to explain that.

Comment Re: Now can we (Score 1) 334

You are missing the fact that with respect to hydrogen, each atom has only one electron. For other materials with conduction bands, the atoms have plenty other electrons to prevent loose electrons from closely approaching nuclei. But when hydrogen forms a metal, a great many nuclei are now "bare", because their lone electrons have been loosed into the conduction band. The electrons are free to closely approach the bare nuclei!
One other thing, and that is that Quantum Mechanics allows electrons to appear to exist at many points simultaneously. This means multiple electrons can "partially" appear to exist in-between two bare nuclei that happen to be randomly approaching each other --you do realize, don't you, that the point of greatest electrical attraction, between two bare nuclei and loose electrons, is the point midway between the nuclei? --the net effect can be equivalent to a single electron holding its position in that place.

Comment Re: Now can we (Score 2) 334

Remember that inside places like Jupiter and brown dwarfs, the percentage of deuterium is very low, compared to the percentage of ordinary hydrogen. This makes it quite rare for two deuterons to randomly approach each other --but in pure metallic deuterium, that fact is no longer valid. Also, it is not the density that matters (per the hypothesis); it is the fact that the electrons are no longer in fixed "orbits" when hydrogen exists in the metallic state. The electrons are loose, forming a "conduction band", and are free to approach hydrogen nuclei arbitrarily closely (because they are not in fixed orbits) This means electrons can get in-between two deuterons that happen to be randomly approaching each other, no matter how closely the deuterons approach each other, and cancel out their mutual repulsion, similar to what muons do in the phenomenon called "muon catalyzed fusion" (the muons are in orbit, but because they have 206 times the mass of electrons, they orbit 206 times closer to the nucleus than electrons, which allows separate deuterons to get close enough to fuse). Electron-catalyzed fusion cannot possibly work when the electrons are in fixed orbits, but in metallic deuterium, they won't be in fixed orbits.

Comment Re: Now can we (Score 3, Interesting) 334

Several years ago I sent off a collection of wild ideas about "cold fusion" to a magazine, hoping for some feedback, and they published it as an actual article. Toward the end of the article was something about a possible way to test the hypothesis. Basically, if you could make some solid metallic hydrogen out of pure deuterium instead of ordinary hydrogen, some cold fusion might happen. It seems to me that the chances of someone being able to do such an experiment have now increased greatly....

Comment Re: we saw that the science was falsified by the C (Score 5, Informative) 371

This is more of an addendum to the just-above msg, than a reply.
Fact One: Carbon dioxide is a greenhouse gas. It is more transparent to frequencies of visible light than frequencies of infrared light.
Fact Two: The total content of carbon dioxide in the atmosphere has been increasing as a result of human activities. The two largest sources are the burning of fossil fuels, and the production of concrete.
Fact Three: The exact amount of greenhouse effect of existing carbon dioxide in the atmosphere is unknown. We only know that it must be some magnitude greater than zero. See Fact One.
Fact Four: Adding still-more carbon dioxide to the atmosphere can only increase the existing greenhouse effect. See Fact One.
Question: On what basis could it be called a "good thing" to keep increasing the total amount of carbon dioxide in the atmosphere?

Comment Re:Enough rope for impeachment (Score 1) 820

The Preamble of the Constitution clearly specifies the purpose of the document. How can anyone who works at some cross-purpose be considered a defender of the Constitution?
Regarding evidence, Follow The Money. See who has been supporting the deniers of AGW --and note that the magnitude of the donations absolutely indicates rich donors, not poor donors.
Finally, I did not specify any "high cost mitigation approach" in my prior post. While it is supposedly widely known that while the first step to solving a problem is to recognize the problem exists, my other post only talked about denial and ignorance, regarding AGW. But here's how I would choose to deal with it: I'd promote nuclear fusion research. Knowledge is power, and the sooner we have that knowledge, the sooner we will have the associated power!

Comment Enough rope for impeachment (Score -1) 820

It may be possible to impeach a government official for violating the Oath of Office, which includes swearing to protect and defend the Constitution. Trump has made no secret of the violations he intends to commit, after taking office. For example, Constitution specifies that one of its purposes is to "promote the general Welfare" --which does not mean promoting only the welfare of the rich, and it is mostly the rich who desperately want all the data about Anthropogenic Global Warming to be ignored, so they can keep getting richer, while ocean levels rise and drown the home of millions of ordinary citizens.
Next, Trump claims to want to make America great again, but then he goes and starts appointing people who promote ignorance, not knowledge. Knowledge Is Power! --not ignorance. It is know-how that was one of the factors that made America great in the first place. To promote ignorance is to not-hardly be consistent with the Oath of Office, to defend the Constitution and consequently promote the general Welfare!
The last thing I'll mention is Trump's claim to oppose abortion --and that means enslaving pregnant women, when they don't want to stay pregnant, in violation of the 13th Amendment. Note that the Constitution requires a Census of ALL persons ("except Indians not taxed") every 10 years, and the Founding Fathers were right there in 1790 to specify the details of how the very first Census would be done. No unborn human has ever been counted in any Census! This means that the Founding Fathers did not consider the unborn to be persons, a Constitutional Precedent far predating the Roe v Wade decision. And modern scientific data about what we might call "generic personhood" indicates that dolphins are vastly more likely to qualify as persons, before any unborn human. Our unborn are mere-animal entities, nothing more than that, and to enslave women as life-support systems for mindless animals would be a heinous crime quite worthy of impeachment.

Comment Alternative (Score 4, Insightful) 917

There is an alternative. The whole notion of UBI depends on the assumption that goods must be purchased. But if they are getting made for essentially free (after costs of capital investment have been recovered; also think in terms of renewable energy and resource-recycling), then why should there be any charge for those goods? Logically, if the goods can be made for free, and obtained for free, an income isn't really quite as important as the OP indicates.

Slashdot Top Deals

One man's "magic" is another man's engineering. "Supernatural" is a null word. -- Robert Heinlein