Max™ wrote:Iron atoms don't "contain" or "lose" neutrinos, they contain neutrons, protons, and electrons. Sometimes a proton can capture an electron and turn into a neutron, and a neutrino. You can tell for certain when this happens.
I think you have a valid interpretation there of current understanding. I want to point out though that when a nucleus emits a beta particle, you can figure that it created an electron on the spot and ejected it, or that the electron was already there all along somehow inside the nucleus. Similarly when it emits a positron, maybe the positron was created on the spot or maybe it was already somehow inside a proton or something. And when it also emits a neutrino, did it create it on the spot or was it residing inside the nucleus? At the moment I think the distinction is more one for philosophy than for physics.
OK, if you carry an iron atom and you get one neutrino from it, that's a bad bargain for mass versus acceleration. Maybe we'll find that we can get lots of neutrinos from an iron atom on demand. Maybe after an iron atom has released a whole lot of neutrinos then it turns to manganese or something. There would be a lot of details to work out, and there's no point in me elaborating on them when at this point it's all fantasy. But I want to point out that this violates no fundamental laws as we currently envision them. Does a Mn55 atom contain more binding energy than a Fe56 atom? Sure, but we just harvested the mass-energy from an entire neutron. We can spare some for binding energy.
The processes which release neutrinos in large amounts all involve what are usually known as thermonuclear reactions, iron in particular is not much good for this, as you lose energy fusing iron, thus iron is literally a starkiller metal.
Everything you say is correct by our current understanding. But remember that there's lots we don't understand about neutrinos. Current beliefs hold that some neutrinos oscillate between a form that is indirectly detectable, versus a form that we currently have no way to detect at all. Why can't there be neutrinos traveling everywhere that we currently cannot detect, that do not oscillate into a form we can detect? Well, currently the standard model does not predict them. There is one kind of neutrino for each kind of lepton, and there has been no need to postulate neutrinos for quarks, bosons, etc. Completely undetectable neutrinos have not been observed, so why predict they're there? If we find a way to detect them then the standard model will be revised.
If you were spitting neutrinos out of any atom, something has to be changing to cause this, proton + electron -> neutron + neutrino is the most common form of such a reaction I can think of, but it is not the only one. However there is no way you could just have a "neutrino leak" without a different end product than the iron or whatnot which you began with.
Yes, you would get a different end product. It would probably be a form of iron, if no charges are gained or lost.
As I recall, Iron tends to turn into a really radioactive form of Cobalt during some of these processes, and you should be more worried about that than launching with a photon rocket.
This is an entirely hypothetical example of something that might possibly be found by future physics. It isn't appropriate to consider the engineering details of manned spaceships that use it, yet.
I picked iron for the example because iron as you say is lowest on the fusion/fission scale, and because we have plenty of iron. If by some sort of coincidence the new physics turns out somehow similar to my description, likely some other element would be more practical to use.
Rockets are stupid for ground launch though, elevators, loops, cannons, anything where you can spend energy once to get most of the mass up without carrying propellant is generally going to win.
Yes, sort of. Once you get high enough, further acceleration has to be from something onboard. You'll probably need some rocketry involved. But it's valuable to reduce that.
Could you get just the iron atoms that are in one orientation to produce their neutrinos all in the same direction? Maybe. That might subtly violate some sort of symmetry but I don't see that it necessarily would.
This would rather unsubtly violate symmetries, hence the mention of Noether's Theorem.
I don't see why it necessarily violates symmetries any more than lasers or magnets do. (Incidentally, I read a story that when Townes proposed the laser, based on his interpretation of Maxwell's equations, various experts in quantum mechanics told him it was incompatible with quantum mechanics and therefore impossible. After he did it, they figured out why it was compatible with QM after all. But when I read his autobiography he didn't tell it that way. They figured merely that it would be impractical to get all the atoms lined up correctly so they would produce their light in the same direction in unison. They were indeed QM experts but they weren't arguing that QM forbade it, they were only expressing their gut feel about statistics.)
Would it take a lot of energy to orient them, compared to what you get from the neutrinos? Would they lose their orientation when they lost a neutrino and have to regain it? Maybe a lot of that could take care of itself, like magnetic domains in crystals that heal themselves of small perturbations though not large ones.
If it could happen this easily, it would happen all the time. Since it doesn't ever happen, it won't happen easily, you can safely assume.
This is the argument that goes "We haven't noticed it happen, therefore it can't happen." Clearly, atoms are mostly stable. But then, a sackful of sugar sitting on a shelf is mostly stable. You can leave it there 10 years dry at room temperature and nothing will happen. However, if you mix it into 5 gallons of water with a few salts etc and some yeast, the sugar will be mostly gone in a week. There is a high energy barrier required for the sugar to burn and it doesn't happen without a lot of heat to start the process. But yeast have enzymes that catalyze a slow burn. They tunnel through the activation barrier.
Could here be something analogous going on with, say, iron? Each of those protons contains a tremendous amount of energy, but they're in a stable state so the energy is trapped in place. You can release all that energy quickly if you have an anti-proton handy.... If there turns out to be some way to catalyze the reaction, you might get energy out of iron. The method that catalyzes it would be rare in nature, which is why we have so many atoms lying around. Similarly, yeast and liquid water are both rare in our solar system so we only observe enzymes catalyzing chemical reactions here on earth.
I don't see that current physics proves we can never have cheap safe travel from earth. It just doesn't give us any way to do it today. Future physics might give us that without having to break conservation laws.
I particularly like neutrinos because there's the possibility they could be safe. If we want to lift millions of tons from earth's surface we can't afford a tremendous amount of pollution from the spent fuel. And if we want to someday have a thriving space economy that pays off, we need lots of trade. To make that work we need very cheap safe travel from earth to escape velocity and back. Future physics might give us that. But JustSo stories aside (I guess this is kind of the opposite of a JustSo story, but there are similarities), you want to make a giant investment in current technology, with an uncertain payoff that is unlikely to be good for the investors on earth. And you want to do that while science and technology are both rapidly changing.
There is no real possibility that any process which emits huge quantities of neutrinos would be safe. The main ones we know of involve active stellar cores, and of course supernova events produce tons of them.
You are not qualified to make that claim, from your understanding of the way that future physics must inevitably develop. I certainly do not claim it will go the way I say. I do claim that physics 200 years from now is likely to be no more similar to what we have today, than today's physics is like the physics of 1812. If you believe that physics progresses faster now than it did then (when it was pursued largely by amateurs and tenured professors puttering in cheap labs), it is likely to change even more in that time.
Currently we have a vague idea how to do that for the few people who get out, who cannot return much to the people on earth who paid the bills. After you burn most of the fossil fuel getting up there, you get tremendous free energy that you mostly can't sell to us. Why should the billions of people who will live on earth pay for the thousands who escape? Well, depending on what you find up there you might wind up with a whole lot of bomb-grade nuclear material that you could drop on us if you wanted to. Maybe after you get established we will have no choice but to keep supporting you.
You can very easily beam energy down from space, where did you get the idea that you can't use microwave power transmission and the like?
How many terawatts do you want to maser to earth?
Currently those are pie-in-the-sky pipe dreams, based on utterly inadequate data. Currently, sending stuff home from space is expensive. Ablation shields and all that, plus if we did a lot of it we don't know what it would do to the climate. Or the insurance rates -- it only takes one big package off course to do a lot of damage anywhere in the world there's a lot of stuff to damage.
I can understand how you'd think it's urgent to get to space. Things are likely to go pretty badly here over the next 30 years or so, and if you don't manage to burn a lot of the fossil fuels getting into space right away, then they will be gone and you'll never get to use them. You could be stuck here in horrible conditions with the rest of us peasants. But see, if we can do good enough science and engineering here, we can get past those temporary problems. We can get to space without the fossil fuels. It might take a little longer, but we could get an actual space economy that works.
Uh, where did you get the idea you need to use fossil fuels to get to space?
Randall calculated it takes about the energy of 1.5 kg of gasoline to lift 1 kg of mass to escape velocity, assuming you don't have to lift any fuel. Where will that energy come from? I guess it could come from nuclear power or possibly solar power. But the bulk of our energy use today comes from fossil fuels.
Yes, there are some LOX+Kerosene rockets, but LOX+Liquid Hydrogen, Nitrogen Tetroxide+Hydrazine, and so forth can all be synthesized fairly simply.
How much fossil fuel do you use to get liquid hydrogen? How much fossil fuel does it take to make your hydrazine? Etc. The advantage is that when you make fuels with more concentrated energy, you don't have to carry as much. Saving on weight can more than make up for the cost of creating the fuel in the first place. Plus the incidental engineering issues, that might say to use one fuel over another. But when you use a solid fuel, you don't dig its components out of the thermite mines. You use up lots of energy making them, and that energy is usually going to come from burning fossil fuels.
The real issue is if we're still completely relying on rockets with no progress for a non-rocket launch system in 30 years, we're pretty screwed as far as getting any significant amount of material into orbit or beyond.
Send the rest of us to hell getting up there now, and you just might find out that you personally are allergic to the algae you have to eat, and the space economy can't grow fast enough because there isn't enough zinc, and you can't mine zinc fast enough because you don't have enough zinc to do the mining. And your local technologists are franticly trying to find a workaround, while the remaining scientists on earth who could help you are having trouble keeping the internet together, much less send messages to you....
You seem to have this idea that the world is on some tipping point or whatever apocalyptic bullshit is being spewed by the latest blowhard touring the news.
I get this from some space enthusiasts. The argument goes that we have to get to space before the fossil fuels are gone, because after that it isn't going to happen and they'll be stuck down here with a bunch of welfare cases and Democrats. I think they're paranoid. But then, they think I'm paranoid. "What? The gigawatt masers? Those aren't death rays! We want to to give away free energy to earth!"
That's sheer failure of imagination. Compare the quality of physics done before 1945 versus since then. Physicists need super-expensive tools because they can get super-expensive tools. Without that budget they would look carefully at things they can look at, and discover new physics that way. They might not discover the same things. But there isn't just one right path for physic advances to take.
...so your argument is that physicists need expensive stuff like the SSC just because they can get away with spending so much on it... though they didn't get it because shortsighted shitbags in Congress couldn't see a reason for it and decided it was too expensive?
There are scientists doing all sorts of science without massive budgets, but arguing that we'd do just as well without these tools is doing a huge disservice to the folks over at the Tevatron, as well as the discoveries made at accelerators before and since.
I'm not saying they'd necessarily be better off with a lower budget. Just -- look at how it's gone with biology. They needed to study DNA. Now, every major university biology department has a scanning electron microscope. People like to look at stuff. And it's easy and cheap to get micromanipulators that can do things like separate out yeast cells. You look at them with a microscope and you move a little oil globule to the one you want, and then you move it around. Over the last 20 years or so scientists have developed methods to manipulate single atoms using a scanning tunneling microscope. If that had come early enough, and if biology had gotten enough money, we would be using that sort of thing to study DNA. When we wanted to create new DNA sequences we would assemble them one subunit at a time, with nanomanipulators. It would be extremely expensive, but that's just how you have to do it, you get what you pay for.
But the way it actually happened, the money just was not there. And researchers studying viruses that attacked bacteria, noticed that when they transferred the same virus to a slightly different strain of bacteria, at first less than 1 in 1000 of the viruses were successful. But after awhile most of them were. It turned out that each kind of bacteria made enzymes that chewed up foreign DNA, but they changed their own DNA in subtle ways to protect it. Eventually researchers learned how to use those enzymes for themselves, to cut up DNA and splice it back together. They got cheap ways to manipulate DNA. Would they even have thought of that if they were busy competing for time on the nanomanipulators? Maybe not.
Science advances when researchers notice little rough edges that don't fit their expectations, and they look closely at them and figure out what's going on. I am not a professional physicist so I don't know what's really going on with them, but for a few years now a lot of the nontechnical talk has implied a lot of theoretical particle physics could not progress until they found out whether there was a Higgs boson. Maybe that was just hype to justify the funding, but if it's real it indicates a massive failure of imagination. Get too many people focused too tightly on one expensive project, and they are not looking everywhere for little anomalies to investigate.
If there was funding to support a lot of physicists, and moderate funding for equipment, they'd look for innovative ways to get results. They'd find some.
Arguing that there is some magical way we might be able to probe the high energy regime with stuff whipped up by a kid genius in his basement only works on the assumption that this is a movie, and it isn't a movie, that shit only works in the movies because of script writers not doing research... I mean fuck, this is a well known trope.
We are doing high-energy stuff because we have the funding for it. There is no guarantee that it will not be mostly a dead end, but it looks like a very good approach to follow, since the money is there. Without so much funding we'd have more emphasis on cosmic rays, more emphasis on cheap ways to bootstrap results, more indirect observation, more low-energy physics, etc. Physics results would come about as fast (or maybe faster) but they would not be the same results. Would the bottom line be better or worse? I don't know. The experiment has not been done. There is no control group.
Yakk, here's your reminder not to click on "View next post".
The Law of Fives is true. I see it everywhere I look for it.