"Information from nowhere" is identical to saying either a violation of conservation of energy, or at the very least, breaking the second law of thermodynamics.
In any case, the statement that you gave is an example of coincidence - you don't KNOW that the newspaper is real, so there's no real (valid) information there, whereas the example I gave (teach someone how to become rich) is an example where you DO know that the newspaper is real, so it is valid information.
It's the difference between going to a psychic and believing she's telling the truth and knowing (and being able to rigorously prove) she's telling the truth.
The first exists all the time: the second does not.
Nope - that wouldn't work. "You" are not unique and indivisible, especially with a time machine.
Man works full day (day 1). Man goes through time machine to go back to beginning of day 1. Man realizes that Man is already at day 1. There are now two of Man at beginning of day 1. If Man wishes to go back through wormhole to repeat day 1 again (a third time), both Man (copy 2) and Man (copy 1) would have to go through.
etc. Step and repeat.
Anyway. Time machines like this are bull - it won't work, it won't happen. Blah.
This doesn't matter : being able to go back to the past at all still does nasty things like provide information from nowhere. Assume you've got a time machine running, and you state "OK, when I become rich, I will come back through my time machine and tell myself how I did it!" poof, you do it, become rich, all happiness prevails.
This is a closed timelike loop. In GR, bizarrely enough, this appears to be allowed. Then again, another example of a closed timelike loop is a flying winged monkey popping out of one side of the wormhole, laughing at the people there, and then going back through the other side.
Whoops! Film sucks even more - it's ~5%. I've been working with photomultipliers too much - they're the 20% that I've been claiming. Anyway, this just increases my point even more - 20 times, not 5 times.
Hell, FILM technologies can't offer rates of 12,000 fps: once you expose a piece of film, it takes thousands upon thousands of years before it settles back so that you can take another frame!
The movie industry, of course, solves this by having tons of pieces of film, and rotating between them. This is, of course, directly applicable to CCDs/digital camera solutions: have a LOT of sensors, and a prism to shift between them all.
Take, for instance, two of those SI sensors: they'd then be able to do 1400 fps. Take 20 of them, and you've got 14K fps.
That's only 2.4 GB/s: that's not that bad - you can get memory nowadays that can sustain that. You're also talking about 1M frames per second (1000 CCDs, firing 1000 times/second): if you move to a more manageable, say, 12K fps (as in the post), you're only talking about 30 MB/s or so, which is just plain slow. Granted, you'd need a thousand of them, but it's just money.
It'd be expensive, yes, but it'd pay for itself in the added sensitivity (5 fold) and the recurring film cost and lack of many-moving-pieces in time. From what I've been reading around here, it looks like there are several companies already working on it.
This is the same problem that film would have, though. You can't get sub-photon resolution of light, because it doesn't exist.
For high speed photography, you need lots of light. This is just generically true. But the quantum efficiency of CCDs is virtually 100%, as opposed to film which is much lower. So, this is a strong point in favor of a CCD system - you'd need less light. There's a poster above talking about how in car crash tests they need massive lighting systems to be able to see things. This'd cut down on their power bill quite a lot.
CCDs (or back-illuminated CCDs, to be specific) are typically 100% efficient - or close enough (90-95 or so). Just search on the Web for "quantum efficiency CCD" - it's a strong function of the energy of the photon, but there are plenty that are virtually 1 around visible wavelengths. Front-illuminated CCDs do have a QE of about 50%, but why would you use one of them?
Hence the reason that CCDs are way cool compared to film: film is only about 20% or so - it takes 5 times less light to get the same image out of a CCD than it does film.
Are you sure about this? CCDs have near perfect QEs, so they capture all of the light that falls on them (as opposed to 20% or so for film, I think). The process for generating the charge is the photoelectric effect, which is basically instant. I think you're more talking about the latency of CCD, rather than the response time. That is, the amount of time it takes to readout the actual frame and let everything settle back to zero.
This problem is solvable: after all, film has the same problem, much much worse: the settling time for film is millions of years (heh)! They solve this by placing huge arrays of film on a loop, and exposing them all for a fraction of time. You could do the exact same thing with a CCD (if you could make flexible silicon, or something like that) that would solve all of these problems.
CCD most distinctly does not suck: you can prove this by looking at astrophotography, which is without a doubt one of the hardest photographic problems that exists: extremely low light levels, and moving targets. Astrophotography is completely dominated by CCDs, because the sensitivity is just so much better, so you can get far more light in a shorter time.
You're right in the last part of your analysis: it's the latency that kills CCD detectors. The light sensitivity (i.e., the quantum efficiency) of CCDs is definitely not the problem, though: CCDs are as close to ideal photodetectors as you can get. They capture virtually 100% of the light that falls on them (their QE is >90%: film is usually quoted at 20%).
This is actually a point in favor of high speed CCDs : in order to get the same level of contrast, you need about 5 times less light than a normal high-speed camera. Remember that the same argument you made for light sensitivity/light levels also applies to film. They'd need a light source 4000 times brighter as well, as the film is only exposed for a small fraction of the time.
You might be able to do something cool that mixes film and CCDs: have a film made of CCDs that are then read out after being exposed to light. This solves the bandwidth problem as well, because you could have multiple systems reading out the data from multiple CCDs - it's not hard to aggregate GB/s worth of bandwidth from slower sources. The main problem, of course, would be flexible silicon. That'd take some work.:)
That's what SysMark is supposed to be: they measure "real-world" performance figures - they run a slew of Photoshop filters, and time it, and other crap.
Unfortunately, SysMark's testing strategy is really terrible. I'm even a bit confused how it works: they say that they scale each test based on how long it takes to complete: but is the scaling from a "reference system" or from each system? If it's from a reference system, then it's biased against whatever that reference system is good at (since the difficult bits get weighted more). If it's from each system on the fly, then it's really meaningless, as one poorly-chosen benchmark can skew the whole thing.
Worse yet: in SysMark 2002, AMD claims that BAPCo uses the same benchmark, multiple times: this is just plain bad, because not only does it magnify the importance of this benchmark, it shrinks the importance of all of the other ones. It's just plain idiotic. Take 3 tests, run them 4 times each, and use the results from all of the runs? It's a very very obvious bias - the only reason you would do that is if you wanted to cheat for one specific processor, and you knew which filters it was good at.
Well, that less sentence was intended to be tounge in cheeck. I could phrase it so that it is non-falsifiable if you prefer (an athiests faith-based notion, if you will):
Yah, but if you phrased it that way, it's identical to the previous one. It's answering "who", not "how". Before you kindof implied a "how", using "seeded". Now you just said that they did it. You can disprove a how. It's not so easy to disprove a "who" when the who is outside of this Universe.
My definition (and contention) of aliens is no more scientific than another's definition and contention of God... indeed the latter is often equated with the former in several fringe religions, and sometimes even by theologens affiliated with mainstream religions. Go figure.
I wasn't arguing with the definition of aliens (as I alluded to just before) but more with the explanation given (re: seeding bit) - that is, the "how", not the "who". The previous poster said "God used evolution" - well, the "how" there is evolution, which (presumedly) you agree with. You just don't agree with the "who". If you had said "Yah, I could say that aliens from another dimension had guided our evolution as well, but..." that'd be functionally identical to the previous statement re: God. It'd also be just as impossible to prove or disprove, as well.
And to be honest, though - there are just as many crackpot scientists as there are theologians. Personally I wish theology was more scientific and rigorous - you may not be able to prove anything, but you can certainly disprove quite a bit. I don't see why it can't be - most fringe religions aren't even self-consistent, so they'd fall apart quite rapidly.
The simple definition that I gave is the most basic starting point for a deity - sapience and omniscience can be mostly inferred from this (although sapience is damn tough, since even we don't know what it is). Omnipotence is actually poorly given to a deity if you ascribe it: how can you "change" the Universe? That's superscribing time on top of time. Anyway, I didn't give an arbitrary definition - I gave one with very little details - that's vague, not arbitrary.:)
Also, it's really quite sad that most critics of religion use the worst examples of it to criticize it: it would be like a person criticizing physics using Pons & Fleischmann, or Podkletnov as examples. There's no way that Christianity ascribes a human gender to a deity - that's directly refuted by several statements from the Pope, if memory serves. As per the Mormons, (canonically) they don't believe in a God fitting my definition - actually, they believe in a creator inside this Universe. A dangerous position, considering it's both physically falsifiable and logically falsifiable - it makes it more like a cultural belief rather than a religion. Man. That could get me into a lot of trouble in places. Maybe that's the reason that religion isn't categorized and rigorously treated.:) There are quite a few rigorous treatises which really clarify exactly "what" God is not in Christianity, at least (outside of time, lacking in gender).
Anyway, I won't disagree on the last point. It's a "how" explanation rather than a "who" explanation. It doesn't even really disprove anything - at worst it disproves the literal interpretation of an English translation of a Hebrew document written after (thousands of?) years of oral tradition. The fact that anyone ever believed that (actually, they selectively believed literal interpretations, which is even worse. Most sections of the Bible they interpret figuratively - the way they were intended, as specifics probably didn't exist in languages then) continues to amaze me.
OK: you're assuming that astrophysicists are accurate to 50%? You have a lot of faith - usually if I ever got within a factor of 2, I'm happy. Being perfectly serious, though, I usually use 10 billion years because that's the order of magnitude that it is. With regard to the other two ages, blah, should've said 4 and 5.
Anyway, your last statement amused me: if we ever found evidence that the Universe was really created just recently, would God pop out of existence like in Hitchhiker's Guide? Heh.
The theory/hypothesis statements were perfect - the last statement is a bit over the top.
And I know this Athiest believes aliens could have seeded the Earth with proto-human life, but until I see some sensible evidence indicating that such might be the case, I'm not going to pay the notion much heed.
Equating that statement with the previous statement is really quite weak - one is falsifiable (aliens), one is not (God). One statement is specific (aliens seeding Earth) one is not (God isn't even defined...).
Or, put slightly differently, one is philosophical (God) and one is scientific (aliens). You can argue against aliens in a rigorous manner, but you can't argue against God in any rigorous manner. In fact, I can make it so that it is specifically impossible to disprove that God created the Universe - by defining God as "that which created the Universe."
All I'm really saying is that equating that statement with aliens seeding Earth is a little counterproductive: the question of whether or not a God exists does not belong to the same science as how life on Earth was created (one is theology, the other is something like anthropology/paleontology). The fact that some Christian fundamentalist idiots do equate it doesn't mean that you should.
It's always possible, for instance, to claim that the Universe just sprang into being, and has been evolving as it is supposed to ever since. Sure. There's no problem with that, it's perfectly consistent, and impossible to disprove. It's also a meaningless statement, from a logic point of view.
Let me put it this way: what's the fundamental difference between instantaneous creation and subsequent evolution and evolution straight from the beginning? The difference is whether or not the ten billion years that it took for the Universe to get to this point actually happened. However, from our point of view, this doesn't matter - the atoms in our body and everything else move just as if the Universe had been here for 10 billion years, and so whether or not it "actually happened" is a statement without a heck of a lot of merit. To us, it did happen: we evolve, and live, as if the Universe is 10 billion years old, and Earth is 5 billion years old, and the Sun is 6 billion years old. Asking whether or not it "actually happened" is not a question for man, science, or anyone in this Universe, because whether or not it "actually happened" is only answerable by something outside this Universe.
So, the basic answer is: of course it is possible. The problem is that there's no reason to believe it - it's not important for the Universe whether or not it was "created" five seconds ago, or ten billion years ago. If you want to believe that, sure, go ahead. Ask God when you die.
But most importantly, don't argue against the "created 10 billion years ago" theory. That's being arrogant - it's claiming that you know something that only God could know.
Actually, I think you misunderstood the satellite issue: they're not using satellites for themselves - they're using satellites that other people put up, and have drifted from their geosynchronous orbits - which is over the equator, and not visible from the pole - into an orbit which is "mostly" geosynchronous, but visible from the pole.
This leads to spotty, poor internet connections (because it's not really geosynchronous, they do move, and they have to be not visible to the pole for some of their orbits) so they need another solution. More satellites would just produce the same current situation, and you definitely don't need to move the old ones back into place - they're working fine currently, but they're just 'spotty', and more importantly, the people who run those satellites probably WANT them in geosync orbit, so they do want to move them back. Fiber's a permanent and cheap solution to this.
Re:Good idea for nuclear waste?
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in response to my assertion that you could apply the given energy along a vector of your chosing
I addressed this: this breaks conservation of momentum. It's not that simple. In order to use the energy that the Sun gives you to deorbit a vessel, you need to either a) redirect the (incredibly weak) momentum from the Sun against your orbit, or b) use propellant. Solar-powered propellant (the ion drive you mentioned, plus its many derivatives) is still very weak compared to actual conventional rockets, and they would take quite a bit of time to deorbit the object.
e.g. time==money with no explanation of why taking 6 years to lob your waste into the Sun is more expensive than taking 6 months
Sorry, this was covered in a previous post as well, and I thought it was to you. Apparently not...
Space isn't empty, and we don't have the ability to model gravity and track all of the objects in the solar system and predict things out several years in advance. Therefore, if you take 6 years (and it would likely be closer to several hundred years! it takes 5 years to get to Mercury by conventional means, and that's a light spacecraft, as opposed to a garbage scow) to deorbit something into the Sun, you need to pay someone to constantly check up on its orbit to make sure that something hasn't happened to sling it back at you, or somewhere else you don't want to go. There's simply no way around this yet, and there likely won't be for some time to come.
(And when it does come, then that will be the scientific advance that allows us to toss waste into the Sun, not the space elevator.)
Re:Good idea for nuclear waste?
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Actually, there's a big difference between needing to insert energy into a system and needing to shift the angular momentum of a system. Energy is a scalar, not a vector: you could remove energy from the system by simply firing a rocket radially away from the Sun. That wouldn't work, obviously: you'd be in a hyperbolic orbit and out into the Solar System in no time. If you need to apply energy in a specific direction, then you're talking about a momentum shift, not an energy shift.
Getting energy from the Sun is easy. It radiates energy, you absorb it, boom, you've got energy. However, it's radiating outward, and so you don't have an easy way to remove the momentum of the system. You've got tons of power, but very litle momentum (you've got E/c momentum, but c is a very big number, even if E is quite large) so in general you're going to have to bring something along to generate that momentum (rockets - that is, throwing some mass out the back).
Personally, I don't think it's a bastard description at all. The fact is that all momentum from the Sun is coming out radially, and it's very weak - it's the flux of energy from the Sun divided by the speed of light. You could use a solar sail, but the amount of thrust is very small (at Earth orbit, it's 5 uN/m^2. This is really tiny, especially for something that's likely going to be tens of thousands of kilograms). If you want to fall into the sun, you need to get rid of the angular momentum that you have - you need to apply that energy against your orbit, which is not easy.
Let me put it this way. The Sun puts out something like 1500 W/m^2 at Earth orbit. Something at Earth orbit has ~ 450 MJ/kg of mass of kinetic energy. Naively you'd say that using the Sun's energy, you should be able to fall into the sun (with 1 m^2 radiator, and gathering all the energy in one burst at Earth orbit - so this is a worst case scenario) in 83 hours/kg. The truth, however, is that you can't use all of the Sun's energy to deorbit you, since you need to remove the momentum as well (that is, there is no way to directly convert the energy of the Sun into something directly pushing against your orbit - solar sails are the closest you can come) Anyway, what I'm basically trying to say is that the statement that "it just takes energy, and we've got the Sun!" is naive, as the situation is more complicated than that. For comparison, by the way, the same naive assumptions with the solar sail method would yield 190 years/kg. Yes, this is not the correct answer, since the solar flux goes as 1/r^2, but the 1/r^2 factor would appear in both calculations, so the scale is correct). You might use the sun's energy to power some engine on board, but you're not going to use it alone to remove momentum, so you've got to bring propellant along.
To put it simply, without a space elevator to the Sun, going to the Sun is more about momentum more than it is about energy.
But, anyway. Next point...
You don't want something with propellant because with propellant, you've just radically increased your costs. You're now throwing away useful material as well as useless material, plus, since you're talking about waste disposal, it'd require a lot of propellant. If you bury it somewhere on Earth, you're wouldn't need that, so it will always win out. The huge constraints on space-based waste disposal into the Sun is that it is resource and money intensive to do it, and the space elevator only eliminates a small portion of that constraint, not all of it.
Remember that time is money, literally. The longer it takes to shove this thing into the Sun, the better off you would have been putting it somewhere else - because it's cheaper. The Moon idea, for instance: nuclear waste could be sent to the Moon almost for free with a space elevator, at the right time of the month (twice, actually - it might actually be free, I'd have to think about the dynamics of it). Focus on the fact that we're talking about throwing garbage into the Sun, not anywhere else. The Sun has fundamental problems associated with it that other objects don't have, so you need to compare it with space-based disposal to other objects (or, in the ultimate act of arrogance, just chuck it out of the ecliptic). Is the benefit of permanent elimination really worth the huge extra cost? No, not really.
Think about it this way: imagine if the stuff was already in orbit, and you wanted to get rid of it. Deorbiting it into the Sun is not easy - it will require time, effort, propellant, and money. Anywhere else can be done for free comparitively. Therefore, dumping waste into the Sun is never going to happen. They'd be more likely to chuck it into Jupiter, or Venus, or something. Once you're in orbit, you'd still hate to go to the Sun, and would much rather go anywhere else. Hence, to conclude, the space elevator will not remove the main problem with space based disposal into the sun of nuclear waste (unless, as someone else put it, the elevator is 10x the distance to the Moon).
Re:Good idea for nuclear waste?
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... and actually, to recomment, it's not entirely clear what would happen to an object just left in solar orbit, thanks to an effect on the next page after the Poynting-Robertson effect - the Yarkovsky effect. I should learn to finish reading before posting. Basically, the object will absorb energy from the Sun and reradiate it isotropically. Depending on the thermal properties and spin of the object, and its shape, this may push it inward, outward, or have no effect at all, and for large objects, will dominate over Poynting-Robertson and light pressure.
Granted, you should be able to allow this to push you inward rather than outward, especially once all constraints on shape are lifted with a space elevator.
Re:Good idea for nuclear waste?
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Found it (grr, it WAS the name that I thought it was). It's the Poynting-Robertson effect. With a time of 1 billion years in orbit, it's highly unlikely that it would actually fall into the Sun. It'd be struck by something first, which would, well, defeat the whole purpose of doing it. Even with a time of 1 million, it'd still be risky.
If you're too far out of the ecliptic, you're not going to do much of a gravity assist, since you're not going to get too close to a planet, now are you?
It's interesting that someone else pointed out that you can choose launch times such that all the elevator's rotation is against the tangential velocity. That'll keep you in the ecliptic (mostly - there'll be a reaaallly small offset). However, if you're talking about gravity assists, those are planned orbits, and having a launch window of "twice a year" limits your ability to create an orbit with gravity assists.
Re:Good idea for nuclear waste?
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I'm not wrong: I'm just not always right.:) Most of the year a significant component will be thrown out of the ecliptic, and no matter what, you're always going to be in an orbit that's out of the ecliptic, it's just a matter of whether or not you're already aligned with that plane.
Although, good point. If the elevator was absolutely gigantically huge, it would work. Hadn't quite thought of that... wonder why.:)
And as for moot points, to resummarize:
1: You can lose a lot of the 30 km/s simply by using the velocity of the far cable. The maximum you can lose is roughly 8 km/s. The minimum you can lose is 4 km/s. Most of the time you'll lose somewhere between the two. You get two shots at the minimum.
2: You can use planets as gravity slingshots. Well, yes, but it'll take a hell of a lot of 'em to do it. Probably around 5 or 6 - most likely more. It would also most likely require course corrections, which defeats the purpose (propellant mass).
3: You could wait a long time and have them fall in via the effect I can't remember. While this is true, it also defeats the purpose. Having something to track and pay attention to in space costs more money than it's worth.
4: You could use a solar sail to push them in. Same problem as above. It takes forever to do it, which defeats the whole purpose.
Jeez. The whole initial point that people started arguing with was that a space elevator doesn't help you with getting rid of trash. All of the problems listed above are far more costly than the initial surface-to-Earth transit. The elevator doesn't help you with the basic problem that you have 30 km/s of rotational velocity to deal with, and you need to get rid of it.
Re:Good idea for nuclear waste?
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Do you remember the name for this effect? I always forget it - there's it and the competing effect for objects that are very small (light pressure). It's in Carroll & Ostlie, but my copy's in my office, and I'm not.
In any case, you're right, but the timescale is so huge that it again proves the point. It's not feasible - it might as well be a waste dump for as long as anyone is around to care.
Did you read the FAQ? Honestly, most of the objections are dealt with in there. After that point, read the NIAC paper, there are actual numbers in there to alleviate any concerns.
The ribbon is 1 cm width from 0-10km, because that's where the atmosphere is important (winds) and it reduces wind drag. Everything higher than that is much thicker. It isn't important being thin at that point because it doesn't need to withstand impacts (the atmosphere shields it) and you don't need to worry about it burning up on reentry (as it's only 10 km).
As for the mass issue, look, this is trivial, and it's been done. Check out the FAQ, check out the proposal. It's 100,000 km long, and the top counterweight is only about 30,000 kg. Carbon nanotubes are reaaaallly light and strong. They rule.
As for the windspeed issue, at height, the air density is less as well, therefore the actual amount of force they place on the ribbon will be minimal.
Regarding your numbers, you have to remember that everyone's planning on tapering this thing: it doesn't have a constant density. Without a counterweight, a tapered ribbon would need 144,000 km to work - not the distance to the moon.They're planning on putting up a counterweight which is of order the size of the ribbon, bringing that down to 91,000 km. The density profile of the ribbon they want to use is pretty complicated: it'd take a bit of work to calculate it out, but go ahead: you'll find that they're right.
Drop a piece of paper. See if it falls on its side. Drop it very very far. See how long it stays on its side then. It'll be very turbulent, and the ribbon will build up a lot of drag, and tear itself apart. This stuff is light - very light. It's no danger.
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"Information from nowhere" is identical to saying either a violation of conservation of energy, or at the very least, breaking the second law of thermodynamics.
In any case, the statement that you gave is an example of coincidence - you don't KNOW that the newspaper is real, so there's no real (valid) information there, whereas the example I gave (teach someone how to become rich) is an example where you DO know that the newspaper is real, so it is valid information.
It's the difference between going to a psychic and believing she's telling the truth and knowing (and being able to rigorously prove) she's telling the truth.
The first exists all the time: the second does not.
Nope - that wouldn't work. "You" are not unique and indivisible, especially with a time machine.
Man works full day (day 1).
Man goes through time machine to go back to beginning of day 1.
Man realizes that Man is already at day 1. There are now two of Man at beginning of day 1.
If Man wishes to go back through wormhole to repeat day 1 again (a third time), both Man (copy 2) and Man (copy 1) would have to go through.
etc. Step and repeat.
Anyway. Time machines like this are bull - it won't work, it won't happen. Blah.
This doesn't matter : being able to go back to the past at all still does nasty things like provide information from nowhere. Assume you've got a time machine running, and you state "OK, when I become rich, I will come back through my time machine and tell myself how I did it!" poof, you do it, become rich, all happiness prevails.
:)
This is a closed timelike loop. In GR, bizarrely enough, this appears to be allowed. Then again, another example of a closed timelike loop is a flying winged monkey popping out of one side of the wormhole, laughing at the people there, and then going back through the other side.
You can guess how much I believe this stuff.
Whoops! Film sucks even more - it's ~5%. I've been working with photomultipliers too much - they're the 20% that I've been claiming. Anyway, this just increases my point even more - 20 times, not 5 times.
Hell, FILM technologies can't offer rates of 12,000 fps: once you expose a piece of film, it takes thousands upon thousands of years before it settles back so that you can take another frame!
The movie industry, of course, solves this by having tons of pieces of film, and rotating between them. This is, of course, directly applicable to CCDs/digital camera solutions: have a LOT of sensors, and a prism to shift between them all.
Take, for instance, two of those SI sensors: they'd then be able to do 1400 fps. Take 20 of them, and you've got 14K fps.
That's only 2.4 GB/s: that's not that bad - you can get memory nowadays that can sustain that. You're also talking about 1M frames per second (1000 CCDs, firing 1000 times/second): if you move to a more manageable, say, 12K fps (as in the post), you're only talking about 30 MB/s or so, which is just plain slow. Granted, you'd need a thousand of them, but it's just money.
It'd be expensive, yes, but it'd pay for itself in the added sensitivity (5 fold) and the recurring film cost and lack of many-moving-pieces in time. From what I've been reading around here, it looks like there are several companies already working on it.
This is the same problem that film would have, though. You can't get sub-photon resolution of light, because it doesn't exist.
For high speed photography, you need lots of light. This is just generically true. But the quantum efficiency of CCDs is virtually 100%, as opposed to film which is much lower. So, this is a strong point in favor of a CCD system - you'd need less light. There's a poster above talking about how in car crash tests they need massive lighting systems to be able to see things. This'd cut down on their power bill quite a lot.
CCDs (or back-illuminated CCDs, to be specific) are typically 100% efficient - or close enough (90-95 or so). Just search on the Web for "quantum efficiency CCD" - it's a strong function of the energy of the photon, but there are plenty that are virtually 1 around visible wavelengths. Front-illuminated CCDs do have a QE of about 50%, but why would you use one of them?
Hence the reason that CCDs are way cool compared to film: film is only about 20% or so - it takes 5 times less light to get the same image out of a CCD than it does film.
Are you sure about this? CCDs have near perfect QEs, so they capture all of the light that falls on them (as opposed to 20% or so for film, I think). The process for generating the charge is the photoelectric effect, which is basically instant. I think you're more talking about the latency of CCD, rather than the response time. That is, the amount of time it takes to readout the actual frame and let everything settle back to zero.
This problem is solvable: after all, film has the same problem, much much worse: the settling time for film is millions of years (heh)! They solve this by placing huge arrays of film on a loop, and exposing them all for a fraction of time. You could do the exact same thing with a CCD (if you could make flexible silicon, or something like that) that would solve all of these problems.
CCD most distinctly does not suck: you can prove this by looking at astrophotography, which is without a doubt one of the hardest photographic problems that exists: extremely low light levels, and moving targets. Astrophotography is completely dominated by CCDs, because the sensitivity is just so much better, so you can get far more light in a shorter time.
You're right in the last part of your analysis: it's the latency that kills CCD detectors. The light sensitivity (i.e., the quantum efficiency) of CCDs is definitely not the problem, though: CCDs are as close to ideal photodetectors as you can get. They capture virtually 100% of the light that falls on them (their QE is >90%: film is usually quoted at 20%).
:)
This is actually a point in favor of high speed CCDs : in order to get the same level of contrast, you need about 5 times less light than a normal high-speed camera. Remember that the same argument you made for light sensitivity/light levels also applies to film. They'd need a light source 4000 times brighter as well, as the film is only exposed for a small fraction of the time.
You might be able to do something cool that mixes film and CCDs: have a film made of CCDs that are then read out after being exposed to light. This solves the bandwidth problem as well, because you could have multiple systems reading out the data from multiple CCDs - it's not hard to aggregate GB/s worth of bandwidth from slower sources. The main problem, of course, would be flexible silicon. That'd take some work.
That's what SysMark is supposed to be: they measure "real-world" performance figures - they run a slew of Photoshop filters, and time it, and other crap.
Unfortunately, SysMark's testing strategy is really terrible. I'm even a bit confused how it works: they say that they scale each test based on how long it takes to complete: but is the scaling from a "reference system" or from each system? If it's from a reference system, then it's biased against whatever that reference system is good at (since the difficult bits get weighted more). If it's from each system on the fly, then it's really meaningless, as one poorly-chosen benchmark can skew the whole thing.
Worse yet: in SysMark 2002, AMD claims that BAPCo uses the same benchmark, multiple times: this is just plain bad, because not only does it magnify the importance of this benchmark, it shrinks the importance of all of the other ones. It's just plain idiotic. Take 3 tests, run them 4 times each, and use the results from all of the runs? It's a very very obvious bias - the only reason you would do that is if you wanted to cheat for one specific processor, and you knew which filters it was good at.
Well, that less sentence was intended to be tounge in cheeck. I could phrase it so that it is non-falsifiable if you prefer (an athiests faith-based notion, if you will):
... indeed the latter is often equated with the former in several fringe religions, and sometimes even by theologens affiliated with mainstream religions. Go figure.
:)
:) There are quite a few rigorous treatises which really clarify exactly "what" God is not in Christianity, at least (outside of time, lacking in gender).
Yah, but if you phrased it that way, it's identical to the previous one. It's answering "who", not "how". Before you kindof implied a "how", using "seeded". Now you just said that they did it. You can disprove a how. It's not so easy to disprove a "who" when the who is outside of this Universe.
My definition (and contention) of aliens is no more scientific than another's definition and contention of God
I wasn't arguing with the definition of aliens (as I alluded to just before) but more with the explanation given (re: seeding bit) - that is, the "how", not the "who". The previous poster said "God used evolution" - well, the "how" there is evolution, which (presumedly) you agree with. You just don't agree with the "who". If you had said "Yah, I could say that aliens from another dimension had guided our evolution as well, but..." that'd be functionally identical to the previous statement re: God. It'd also be just as impossible to prove or disprove, as well.
And to be honest, though - there are just as many crackpot scientists as there are theologians. Personally I wish theology was more scientific and rigorous - you may not be able to prove anything, but you can certainly disprove quite a bit. I don't see why it can't be - most fringe religions aren't even self-consistent, so they'd fall apart quite rapidly.
The simple definition that I gave is the most basic starting point for a deity - sapience and omniscience can be mostly inferred from this (although sapience is damn tough, since even we don't know what it is). Omnipotence is actually poorly given to a deity if you ascribe it: how can you "change" the Universe? That's superscribing time on top of time. Anyway, I didn't give an arbitrary definition - I gave one with very little details - that's vague, not arbitrary.
Also, it's really quite sad that most critics of religion use the worst examples of it to criticize it: it would be like a person criticizing physics using Pons & Fleischmann, or Podkletnov as examples. There's no way that Christianity ascribes a human gender to a deity - that's directly refuted by several statements from the Pope, if memory serves. As per the Mormons, (canonically) they don't believe in a God fitting my definition - actually, they believe in a creator inside this Universe. A dangerous position, considering it's both physically falsifiable and logically falsifiable - it makes it more like a cultural belief rather than a religion. Man. That could get me into a lot of trouble in places. Maybe that's the reason that religion isn't categorized and rigorously treated.
Anyway, I won't disagree on the last point. It's a "how" explanation rather than a "who" explanation. It doesn't even really disprove anything - at worst it disproves the literal interpretation of an English translation of a Hebrew document written after (thousands of?) years of oral tradition. The fact that anyone ever believed that (actually, they selectively believed literal interpretations, which is even worse. Most sections of the Bible they interpret figuratively - the way they were intended, as specifics probably didn't exist in languages then) continues to amaze me.
OK: you're assuming that astrophysicists are accurate to 50%? You have a lot of faith - usually if I ever got within a factor of 2, I'm happy. Being perfectly serious, though, I usually use 10 billion years because that's the order of magnitude that it is. With regard to the other two ages, blah, should've said 4 and 5.
Anyway, your last statement amused me: if we ever found evidence that the Universe was really created just recently, would God pop out of existence like in Hitchhiker's Guide? Heh.
The theory/hypothesis statements were perfect - the last statement is a bit over the top.
And I know this Athiest believes aliens could have seeded the Earth with proto-human life, but until I see some sensible evidence indicating that such might be the case, I'm not going to pay the notion much heed.
Equating that statement with the previous statement is really quite weak - one is falsifiable (aliens), one is not (God). One statement is specific (aliens seeding Earth) one is not (God isn't even defined...).
Or, put slightly differently, one is philosophical (God) and one is scientific (aliens). You can argue against aliens in a rigorous manner, but you can't argue against God in any rigorous manner. In fact, I can make it so that it is specifically impossible to disprove that God created the Universe - by defining God as "that which created the Universe."
All I'm really saying is that equating that statement with aliens seeding Earth is a little counterproductive: the question of whether or not a God exists does not belong to the same science as how life on Earth was created (one is theology, the other is something like anthropology/paleontology). The fact that some Christian fundamentalist idiots do equate it doesn't mean that you should.
It's always possible, for instance, to claim that the Universe just sprang into being, and has been evolving as it is supposed to ever since. Sure. There's no problem with that, it's perfectly consistent, and impossible to disprove. It's also a meaningless statement, from a logic point of view.
Let me put it this way: what's the fundamental difference between instantaneous creation and subsequent evolution and evolution straight from the beginning? The difference is whether or not the ten billion years that it took for the Universe to get to this point actually happened. However, from our point of view, this doesn't matter - the atoms in our body and everything else move just as if the Universe had been here for 10 billion years, and so whether or not it "actually happened" is a statement without a heck of a lot of merit. To us, it did happen: we evolve, and live, as if the Universe is 10 billion years old, and Earth is 5 billion years old, and the Sun is 6 billion years old. Asking whether or not it "actually happened" is not a question for man, science, or anyone in this Universe, because whether or not it "actually happened" is only answerable by something outside this Universe.
So, the basic answer is: of course it is possible. The problem is that there's no reason to believe it - it's not important for the Universe whether or not it was "created" five seconds ago, or ten billion years ago. If you want to believe that, sure, go ahead. Ask God when you die.
But most importantly, don't argue against the "created 10 billion years ago" theory. That's being arrogant - it's claiming that you know something that only God could know.
Actually, I think you misunderstood the satellite issue: they're not using satellites for themselves - they're using satellites that other people put up, and have drifted from their geosynchronous orbits - which is over the equator, and not visible from the pole - into an orbit which is "mostly" geosynchronous, but visible from the pole.
This leads to spotty, poor internet connections (because it's not really geosynchronous, they do move, and they have to be not visible to the pole for some of their orbits) so they need another solution. More satellites would just produce the same current situation, and you definitely don't need to move the old ones back into place - they're working fine currently, but they're just 'spotty', and more importantly, the people who run those satellites probably WANT them in geosync orbit, so they do want to move them back. Fiber's a permanent and cheap solution to this.
in response to my assertion that you could apply the given energy along a vector of your chosing
I addressed this: this breaks conservation of momentum. It's not that simple. In order to use the energy that the Sun gives you to deorbit a vessel, you need to either a) redirect the (incredibly weak) momentum from the Sun against your orbit, or b) use propellant. Solar-powered propellant (the ion drive you mentioned, plus its many derivatives) is still very weak compared to actual conventional rockets, and they would take quite a bit of time to deorbit the object.
e.g. time==money with no explanation of why taking 6 years to lob your waste into the Sun is more expensive than taking 6 months
Sorry, this was covered in a previous post as well, and I thought it was to you. Apparently not...
Space isn't empty, and we don't have the ability to model gravity and track all of the objects in the solar system and predict things out several years in advance. Therefore, if you take 6 years (and it would likely be closer to several hundred years! it takes 5 years to get to Mercury by conventional means, and that's a light spacecraft, as opposed to a garbage scow) to deorbit something into the Sun, you need to pay someone to constantly check up on its orbit to make sure that something hasn't happened to sling it back at you, or somewhere else you don't want to go. There's simply no way around this yet, and there likely won't be for some time to come.
(And when it does come, then that will be the scientific advance that allows us to toss waste into the Sun, not the space elevator.)
Actually, there's a big difference between needing to insert energy into a system and needing to shift the angular momentum of a system. Energy is a scalar, not a vector: you could remove energy from the system by simply firing a rocket radially away from the Sun. That wouldn't work, obviously: you'd be in a hyperbolic orbit and out into the Solar System in no time. If you need to apply energy in a specific direction, then you're talking about a momentum shift, not an energy shift.
Getting energy from the Sun is easy. It radiates energy, you absorb it, boom, you've got energy. However, it's radiating outward, and so you don't have an easy way to remove the momentum of the system. You've got tons of power, but very litle momentum (you've got E/c momentum, but c is a very big number, even if E is quite large) so in general you're going to have to bring something along to generate that momentum (rockets - that is, throwing some mass out the back).
Personally, I don't think it's a bastard description at all. The fact is that all momentum from the Sun is coming out radially, and it's very weak - it's the flux of energy from the Sun divided by the speed of light. You could use a solar sail, but the amount of thrust is very small (at Earth orbit, it's 5 uN/m^2. This is really tiny, especially for something that's likely going to be tens of thousands of kilograms). If you want to fall into the sun, you need to get rid of the angular momentum that you have - you need to apply that energy against your orbit, which is not easy.
Let me put it this way. The Sun puts out something like 1500 W/m^2 at Earth orbit. Something at Earth orbit has ~ 450 MJ/kg of mass of kinetic energy. Naively you'd say that using the Sun's energy, you should be able to fall into the sun (with 1 m^2 radiator, and gathering all the energy in one burst at Earth orbit - so this is a worst case scenario) in 83 hours/kg. The truth, however, is that you can't use all of the Sun's energy to deorbit you, since you need to remove the momentum as well (that is, there is no way to directly convert the energy of the Sun into something directly pushing against your orbit - solar sails are the closest you can come) Anyway, what I'm basically trying to say is that the statement that "it just takes energy, and we've got the Sun!" is naive, as the situation is more complicated than that. For comparison, by the way, the same naive assumptions with the solar sail method would yield 190 years/kg. Yes, this is not the correct answer, since the solar flux goes as 1/r^2, but the 1/r^2 factor would appear in both calculations, so the scale is correct). You might use the sun's energy to power some engine on board, but you're not going to use it alone to remove momentum, so you've got to bring propellant along.
To put it simply, without a space elevator to the Sun, going to the Sun is more about momentum more than it is about energy.
But, anyway. Next point...
You don't want something with propellant because with propellant, you've just radically increased your costs. You're now throwing away useful material as well as useless material, plus, since you're talking about waste disposal, it'd require a lot of propellant. If you bury it somewhere on Earth, you're wouldn't need that, so it will always win out. The huge constraints on space-based waste disposal into the Sun is that it is resource and money intensive to do it, and the space elevator only eliminates a small portion of that constraint, not all of it.
Remember that time is money, literally. The longer it takes to shove this thing into the Sun, the better off you would have been putting it somewhere else - because it's cheaper. The Moon idea, for instance: nuclear waste could be sent to the Moon almost for free with a space elevator, at the right time of the month (twice, actually - it might actually be free, I'd have to think about the dynamics of it). Focus on the fact that we're talking about throwing garbage into the Sun, not anywhere else. The Sun has fundamental problems associated with it that other objects don't have, so you need to compare it with space-based disposal to other objects (or, in the ultimate act of arrogance, just chuck it out of the ecliptic). Is the benefit of permanent elimination really worth the huge extra cost? No, not really.
Think about it this way: imagine if the stuff was already in orbit, and you wanted to get rid of it. Deorbiting it into the Sun is not easy - it will require time, effort, propellant, and money. Anywhere else can be done for free comparitively. Therefore, dumping waste into the Sun is never going to happen. They'd be more likely to chuck it into Jupiter, or Venus, or something. Once you're in orbit, you'd still hate to go to the Sun, and would much rather go anywhere else. Hence, to conclude, the space elevator will not remove the main problem with space based disposal into the sun of nuclear waste (unless, as someone else put it, the elevator is 10x the distance to the Moon).
... and actually, to recomment, it's not entirely clear what would happen to an object just left in solar orbit, thanks to an effect on the next page after the Poynting-Robertson effect - the Yarkovsky effect. I should learn to finish reading before posting. Basically, the object will absorb energy from the Sun and reradiate it isotropically. Depending on the thermal properties and spin of the object, and its shape, this may push it inward, outward, or have no effect at all, and for large objects, will dominate over Poynting-Robertson and light pressure.
Granted, you should be able to allow this to push you inward rather than outward, especially once all constraints on shape are lifted with a space elevator.
Found it (grr, it WAS the name that I thought it was). It's the Poynting-Robertson effect. With a time of 1 billion years in orbit, it's highly unlikely that it would actually fall into the Sun. It'd be struck by something first, which would, well, defeat the whole purpose of doing it. Even with a time of 1 million, it'd still be risky.
If you're too far out of the ecliptic, you're not going to do much of a gravity assist, since you're not going to get too close to a planet, now are you?
It's interesting that someone else pointed out that you can choose launch times such that all the elevator's rotation is against the tangential velocity. That'll keep you in the ecliptic (mostly - there'll be a reaaallly small offset). However, if you're talking about gravity assists, those are planned orbits, and having a launch window of "twice a year" limits your ability to create an orbit with gravity assists.
I'm not wrong: I'm just not always right. :) Most of the year a significant component will be thrown out of the ecliptic, and no matter what, you're always going to be in an orbit that's out of the ecliptic, it's just a matter of whether or not you're already aligned with that plane.
:)
Although, good point. If the elevator was absolutely gigantically huge, it would work. Hadn't quite thought of that... wonder why.
And as for moot points, to resummarize:
1: You can lose a lot of the 30 km/s simply by using the velocity of the far cable.
The maximum you can lose is roughly 8 km/s. The minimum you can lose is 4 km/s. Most of the time you'll lose somewhere between the two. You get two shots at the minimum.
2: You can use planets as gravity slingshots. Well, yes, but it'll take a hell of a lot of 'em to do it. Probably around 5 or 6 - most likely more. It would also most likely require course corrections, which defeats the purpose (propellant mass).
3: You could wait a long time and have them fall in via the effect I can't remember. While this is true, it also defeats the purpose. Having something to track and pay attention to in space costs more money than it's worth.
4: You could use a solar sail to push them in. Same problem as above. It takes forever to do it, which defeats the whole purpose.
Jeez. The whole initial point that people started arguing with was that a space elevator doesn't help you with getting rid of trash. All of the problems listed above are far more costly than the initial surface-to-Earth transit. The elevator doesn't help you with the basic problem that you have 30 km/s of rotational velocity to deal with, and you need to get rid of it.
Do you remember the name for this effect? I always forget it - there's it and the competing effect for objects that are very small (light pressure). It's in Carroll & Ostlie, but my copy's in my office, and I'm not.
In any case, you're right, but the timescale is so huge that it again proves the point. It's not feasible - it might as well be a waste dump for as long as anyone is around to care.
Did you read the FAQ? Honestly, most of the objections are dealt with in there. After that point, read the NIAC paper, there are actual numbers in there to alleviate any concerns.
The ribbon is 1 cm width from 0-10km, because that's where the atmosphere is important (winds) and it reduces wind drag. Everything higher than that is much thicker. It isn't important being thin at that point because it doesn't need to withstand impacts (the atmosphere shields it) and you don't need to worry about it burning up on reentry (as it's only 10 km).
As for the mass issue, look, this is trivial, and it's been done. Check out the FAQ, check out the proposal. It's 100,000 km long, and the top counterweight is only about 30,000 kg. Carbon nanotubes are reaaaallly light and strong. They rule.
As for the windspeed issue, at height, the air density is less as well, therefore the actual amount of force they place on the ribbon will be minimal.
Regarding your numbers, you have to remember that everyone's planning on tapering this thing: it doesn't have a constant density. Without a counterweight, a tapered ribbon would need 144,000 km to work - not the distance to the moon.They're planning on putting up a counterweight which is of order the size of the ribbon, bringing that down to 91,000 km. The density profile of the ribbon they want to use is pretty complicated: it'd take a bit of work to calculate it out, but go ahead: you'll find that they're right.
Drop a piece of paper. See if it falls on its side. Drop it very very far. See how long it stays on its side then. It'll be very turbulent, and the ribbon will build up a lot of drag, and tear itself apart. This stuff is light - very light. It's no danger.