Changing your landing point is very easy - you just slightly change the attitude of the rocket during its retro burn, changing the horizontal component of the acceleration. Changing your landing point to where you want it to be is harder, but the SpaceX people seem to be making good progress on this. (Except that they just blew up their test vehicle...)
I've been interested in this for some time. Here are some solutions I've come across: Something like a standard battery Flow batteries, where you store liquid electrolytes in tanks, and energy capacity is proportional to the capacity of the tanks Salt/Liquid metal batteries. Take the process for smelting aluminium, and make it reversible. (The metal used need not be aluminium.) There is a good TED talk on this. Fixed volume compressed gas storage: pump gas into a pressure vessel or abandoned mine Fixed pressure compressed gas storage: pump gas into a bladder deep under water. This works well for off shore wind farms, as they have the deep water right there. Otherwise you need a convenient lake or flooded mine. Elevated water reservoir. Needs the right topography and hydrography, so doesn't work everywhere. Variable output hydro power: similar to the above, but instead of pumping water uphill you just increase/decrease the downhill flow that already exists, to match you output to the production shortfall of the time variable generators. If you already have hydro power, this is very cheap, possibly free. At worst you need to increase peak capacity by adding turbines. Heat storage: store energy as heat in a large thermal mass, extract it with some form of heat engine.
Complementary to this, we can also try to time-shift demand: Off-peak water heating. This has been around for many decades. Off-peak heating/cooling using thermal storage (e.g. an insulated water tank under your house from which your radiators are fed.) Off-peak charging of plug-in electric cars. (We can even use peak-hour extraction of power from the electric cars.) This is cheap in that those batteries are already there for other purposes. It does cost if they batteries have a limited number of recharge cycles (which currently they do.)
For most species, childhood is all risk, no benefit (where benefit = breeding), and so it is to be got through as fast as possible (or at least in time for next breeding season). If glucose shortage was the only reason for doubling the length of our childhood, there would be a huge evolutionary pressure towards kids who could metabolize much more food and reach adulthood in half the time.
There is an obvious reason why humans have such a long childhood - it is because we have so very much to learn. Little bodies can learn as well as big bodies, and cost less to maintain.
Some new game changing battery/supercapacitor breakthrough might be just around the corner. If so, all that investment in the battery megafactory could get wiped out. Ditto with investing in lithium mining.
So the megafactory might be still happily minting money 25 years from now, or it might be nearly worthless 5 years from now. Presumably this means we'll be paying a risk premium on lithium and lithium batteries. It seems to me that it would be smart for Tesla to be investing in the very technologies that might disrupt their factory, as an insurance policy. That way, if the fortune you've invested in the factory evaporates, hopefully you'll have a new replacement fortune due to having a stake in the new technology. However, this strategy requires that you have the funds for this speculative investment, and has you encouraging the very research which will ruin your factory investment. (Also, maybe you won't have invested in the right places and won't have a stake in the new technology.) In the case of Tesla, they are major consumers as well as (soon to be) major manufacturers of batteries, so there is an additional up-side to investing in the hypothetical tech breakthrough.
Is lithium mining expanding fast enough to feed this factory when it comes online?
“Now we’re going to give you what you deserve for meddling in our business and when we finish with you, you can sue the city for $5 million and get rich, we don’t care,” Lt. Dennis Ferber said, according to the suit filed in Brooklyn Federal Court.
It appears the police followed exactly your logic. However if that statement is substantiated, Ferber's boss would be seriously derelict in their duty if they didn't fire him for this. He's publicly stated that he doesn't care about knowingly causing a multi-million dollar liability for his employer. IANAL, but I expect that should these cops not get punished and pull a similar stunt again, the city would open themselves up for greater punitive damages, as they'd let employees with a known track record of rights abuse continue working where they were likely to abuse again.
It would be good to see criminal proceedings, but I doubt it will happen.
Most metals are not ferromagnetic, and so are not held in place by magnets. I'm pretty sure neither indium nor gallium are ferromagnetic.
As they are good conductors, metals do develop eddy currents in a changing magnetic field, which heats them. (Try dropping a magnet through a narrow aluminium tube. The energy loss due to eddy currents will slow its fall considerably.) If you had this liquid metal inside you, having an MRI scan might be a really bad idea - I wouldn't rule out the possibility that the bits of you in contact with the metal could get cooked. This would be a considerable drawback in a cancer treatment. It would be no different than having metal inside you for other reasons - e.g. titanium pins used in surgery. Does anyone know how those react to MRI?
Aside from the risks of what happens to the liquid metal after it's done its job, you also end up with a big lump of dead cells inside the body, which can't be good. On the other hand, presumably successful radiation therapy has the same result, and the result doesn't have to be 'good', it just has to be 'better than having a tumor'. Would someone with actual medical knowledge care to comment?
I agree. The theory can be rubbished in very simple terms: The inventors assume no new physics, and conclude their device will violate conservation of momentum. All the 'input' physics conserves momentum. Therefore their analysis is wrong.
If I give you a list of numbers which are all even and ask you to add them up, and you give me a sum which is odd, I know you've messed up. I don't need to check the details of your adding and point to exactly where you went wrong. This situation is analogous.
So if the device *does* work (which I very much doubt) it will be pure wild coincidence, not due to any cleverness on the part of the inventors.
(Note: these comments are based on the description of the EmDrive in New Scientist some years ago. I am unfamiliar with the Cannae Drive, so I don't know if it has the same theoretical flaw. If it *does* end up working, I will revoke my vow to never again subscribe to New Scientist.)
"ROC analysis of [the test statistic], for cancers plus precancerous/suspect conditions vs. controls, cancer vs. precancerous/suspect conditions plus controls, and cancer vs. controls, gave areas under the curve of 0.87, 0.89, and 0.93, respectively (P<0.001). Optimization allowed test sensitivity or specificity to approach 100% with acceptable complementary measures."
The ROC curve has area under it of 1 for a perfect classifier and 0.5 for wild guessing. This is a more useful measurement than the p-value. (E.g. if I look at height vs sex for humans, it won't take too big a sample to get a great p-value for there being a difference, yet classifying people as male/female depending on whether they exceed some height threshold is a very poor diagnostic system.) I don't have much of a feel for how good ROC area of about 0.9 is for a medical test. I'd guess it is good enough to be useful, but you'd not want to rely on that test alone.
The plane was 10km up. It wasn't shot down by something bought for $50,000 from Bob's Quality Used Implements of Death and Destruction and delivered to you by a courier van. The suspected weapon system requires at minimum one tank sized tracked launcher vehicle, and for full capability it requires three such vehicles. This is way out of Bob the arms dealer's league. Although I'm pretty much guessing here, the missile alone I expect would cost over a million dollars to manufacture.
Having said that, the possibility exists that rebels with military experience seized such a weapon system from an overrun Ukrainian military base.
I think you've misread the post. In "What she did was wrong", I read "wrong" as "unethical", "unscientific", or at the very best "incompetent". Your criticism assumes it meant "something which eventually turned out not to be how reality works".
Immune system genes are often under balancing selection - i.e. the rarest alleles are favoured (until, due to this favouring, they cease to be rarest, then other alleles are favoured.) An infusion of new different alleles from Neandertals could be favoured simply because they are different, not because they are evolved to European conditions.
Testing between these hypotheses seems difficult. The 'balancing selection' hypothesis predicts that the genes will readily spread back into Africa, whereas the 'evolved for European conditions' predicts they will not. The problem is that you need some neutral mutations that arose in Europe at the same time as a 'control' for comparison purposes. I'm not sure how to identify such mutations, but I expect it could be done.
There is another obvious point in history where such a gene transfer could have occurred. European conditions favour light skin, and Neandertals had been hanging out there for some tens of thousands of years before modern humans turned up and so had evolved light skin. These newcomers, having recent ancestry in Africa, were probably dark skinned. Interbreeding could easily have introduced the beneficial-to-European-conditions light skin mutations into the modern population.
My memory of the literature (which I have followed just a little bit, not closely) is that this did not happen - genetic analysis shows that modern Europeans and Neandertals acquired light skin through different mutations. However, Wikipedia says this is still under debate.
This is a silly objection. That isn't how payback times are used.
Payback time is a quick indication of return on investment. You then compare that return on investment with the other options available to you, such as leaving the money in the bank.
If you included interest rates in payback time, you'd need to be constantly adjusting it as rates changed, and it would differ for different entities depending on their access to finance. Instead you keep it simple, and each entity has its own idea (based on circumstances and current interest rates) of what the effective payback time is of leaving the money in the bank (or not borrowing it, or investing it in other opportunities.) (For example, a start-up is likely to require a very short payback time - they're strapped for cash and are trying to get their Big New Idea to market where they hope it will make a fortune. Up-front money is then very expensive compared to down-the-road money. For them, it may make sense to lease a supercomputer even if buying it would have a two year payback time.)
What is missing from this analysis is depreciation of assets. After 6.4 years, money in the bank will have depreciated much less than the solar cells. Payback time is a rough guide - it tells you whether it is worth your while doing a more detailed analysis including finance cost, depreciation, tax implications etc.
They aren't. They're using an established term "energy payback". The authors wrote an analysis which will be useful to many people but used the word "payback" in a way which does not match your preconceived notion of how it should be used. For this, you label them "charlatans".
So all the people interested in energy payback times should not be able to publish or read about it because you've claimed ownership of the word "payback" and won't license them to use it? They should use a less clear term to express their meaning because otherwise some random idiot who reads technical papers might make the leap "payback = money", despite the term "energy payback" being self explanatory?
Had you argued that because this is "energy payback" rather than financial payback, it isn't worthy of being reported on Slashdot, I could respect your argument. Instead you label people charlatans because what they discuss is not what you're interested it.
Oh good, I'll just print up a bunch of fliers saying you torture kittens and set fire to orphanages and post them around your home town. Because nobody has heard of you and I'm not a publicly listed company, it will be 'opinion' rather than 'libel'.
I have no idea whether this guy's claims are justified, but neither do you. My liking Wikipedia does not therefore mean that the facts or the law are on the side of Wikipedia.
When El Nino leads to a new record high temperature by a large margin (for argument's sake, in 2015), the denialists will quietly adopt this as their new standard for 'normal' and in 2025 they'll be saying "warming is a hoax because temperatures haven't risen on average since 2015."
Slashdot Mirror
Changing your landing point is very easy - you just slightly change the attitude of the rocket during its retro burn, changing the horizontal component of the acceleration. Changing your landing point to where you want it to be is harder, but the SpaceX people seem to be making good progress on this. (Except that they just blew up their test vehicle...)
I've been interested in this for some time. Here are some solutions I've come across:
Something like a standard battery
Flow batteries, where you store liquid electrolytes in tanks, and energy capacity is proportional to the capacity of the tanks
Salt/Liquid metal batteries. Take the process for smelting aluminium, and make it reversible. (The metal used need not be aluminium.) There is a good TED talk on this.
Fixed volume compressed gas storage: pump gas into a pressure vessel or abandoned mine
Fixed pressure compressed gas storage: pump gas into a bladder deep under water. This works well for off shore wind farms, as they have the deep water right there. Otherwise you need a convenient lake or flooded mine.
Elevated water reservoir. Needs the right topography and hydrography, so doesn't work everywhere.
Variable output hydro power: similar to the above, but instead of pumping water uphill you just increase/decrease the downhill flow that already exists, to match you output to the production shortfall of the time variable generators. If you already have hydro power, this is very cheap, possibly free. At worst you need to increase peak capacity by adding turbines.
Heat storage: store energy as heat in a large thermal mass, extract it with some form of heat engine.
Complementary to this, we can also try to time-shift demand:
Off-peak water heating. This has been around for many decades.
Off-peak heating/cooling using thermal storage (e.g. an insulated water tank under your house from which your radiators are fed.)
Off-peak charging of plug-in electric cars. (We can even use peak-hour extraction of power from the electric cars.) This is cheap in that those batteries are already there for other purposes. It does cost if they batteries have a limited number of recharge cycles (which currently they do.)
For most species, childhood is all risk, no benefit (where benefit = breeding), and so it is to be got through as fast as possible (or at least in time for next breeding season). If glucose shortage was the only reason for doubling the length of our childhood, there would be a huge evolutionary pressure towards kids who could metabolize much more food and reach adulthood in half the time.
There is an obvious reason why humans have such a long childhood - it is because we have so very much to learn. Little bodies can learn as well as big bodies, and cost less to maintain.
We need way, way, more women like her on TV.
Yes, let's over-represent a minority group on purpose.
Yes, people with talent are overrepresented on TV. Most of us prefer it that way.
Some new game changing battery/supercapacitor breakthrough might be just around the corner. If so, all that investment in the battery megafactory could get wiped out. Ditto with investing in lithium mining.
So the megafactory might be still happily minting money 25 years from now, or it might be nearly worthless 5 years from now. Presumably this means we'll be paying a risk premium on lithium and lithium batteries. It seems to me that it would be smart for Tesla to be investing in the very technologies that might disrupt their factory, as an insurance policy. That way, if the fortune you've invested in the factory evaporates, hopefully you'll have a new replacement fortune due to having a stake in the new technology. However, this strategy requires that you have the funds for this speculative investment, and has you encouraging the very research which will ruin your factory investment. (Also, maybe you won't have invested in the right places and won't have a stake in the new technology.) In the case of Tesla, they are major consumers as well as (soon to be) major manufacturers of batteries, so there is an additional up-side to investing in the hypothetical tech breakthrough.
Is lithium mining expanding fast enough to feed this factory when it comes online?
From TFA:
“Now we’re going to give you what you deserve for meddling in our business and when we finish with you, you can sue the city for $5 million and get rich, we don’t care,” Lt. Dennis Ferber said, according to the suit filed in Brooklyn Federal Court.
It appears the police followed exactly your logic. However if that statement is substantiated, Ferber's boss would be seriously derelict in their duty if they didn't fire him for this. He's publicly stated that he doesn't care about knowingly causing a multi-million dollar liability for his employer. IANAL, but I expect that should these cops not get punished and pull a similar stunt again, the city would open themselves up for greater punitive damages, as they'd let employees with a known track record of rights abuse continue working where they were likely to abuse again.
It would be good to see criminal proceedings, but I doubt it will happen.
Wikipedia says:
While metallic gallium is not considered toxic, the data are inconclusive.
Pure indium in metal form is considered nontoxic by most sources.
Most metals are not ferromagnetic, and so are not held in place by magnets. I'm pretty sure neither indium nor gallium are ferromagnetic.
As they are good conductors, metals do develop eddy currents in a changing magnetic field, which heats them. (Try dropping a magnet through a narrow aluminium tube. The energy loss due to eddy currents will slow its fall considerably.) If you had this liquid metal inside you, having an MRI scan might be a really bad idea - I wouldn't rule out the possibility that the bits of you in contact with the metal could get cooked. This would be a considerable drawback in a cancer treatment. It would be no different than having metal inside you for other reasons - e.g. titanium pins used in surgery. Does anyone know how those react to MRI?
Aside from the risks of what happens to the liquid metal after it's done its job, you also end up with a big lump of dead cells inside the body, which can't be good. On the other hand, presumably successful radiation therapy has the same result, and the result doesn't have to be 'good', it just has to be 'better than having a tumor'. Would someone with actual medical knowledge care to comment?
Here is another cat hack story, although it seems in this case the cat was only used as a data repository.
No, that is the point. The mathematics is provably wrong.
I agree. The theory can be rubbished in very simple terms: The inventors assume no new physics, and conclude their device will violate conservation of momentum. All the 'input' physics conserves momentum. Therefore their analysis is wrong.
If I give you a list of numbers which are all even and ask you to add them up, and you give me a sum which is odd, I know you've messed up. I don't need to check the details of your adding and point to exactly where you went wrong. This situation is analogous.
So if the device *does* work (which I very much doubt) it will be pure wild coincidence, not due to any cleverness on the part of the inventors.
(Note: these comments are based on the description of the EmDrive in New Scientist some years ago. I am unfamiliar with the Cannae Drive, so I don't know if it has the same theoretical flaw. If it *does* end up working, I will revoke my vow to never again subscribe to New Scientist.)
Here is the abstract. The actual paper is behind a paywall.
"ROC analysis of [the test statistic], for cancers plus precancerous/suspect conditions vs. controls, cancer vs. precancerous/suspect conditions plus controls, and cancer vs. controls, gave areas under the curve of 0.87, 0.89, and 0.93, respectively (P<0.001). Optimization allowed test sensitivity or specificity to approach 100% with acceptable complementary measures."
The ROC curve has area under it of 1 for a perfect classifier and 0.5 for wild guessing. This is a more useful measurement than the p-value. (E.g. if I look at height vs sex for humans, it won't take too big a sample to get a great p-value for there being a difference, yet classifying people as male/female depending on whether they exceed some height threshold is a very poor diagnostic system.) I don't have much of a feel for how good ROC area of about 0.9 is for a medical test. I'd guess it is good enough to be useful, but you'd not want to rely on that test alone.
The plane was 10km up. It wasn't shot down by something bought for $50,000 from Bob's Quality Used Implements of Death and Destruction and delivered to you by a courier van. The suspected weapon system requires at minimum one tank sized tracked launcher vehicle, and for full capability it requires three such vehicles. This is way out of Bob the arms dealer's league. Although I'm pretty much guessing here, the missile alone I expect would cost over a million dollars to manufacture.
Having said that, the possibility exists that rebels with military experience seized such a weapon system from an overrun Ukrainian military base.
I think you've misread the post. In "What she did was wrong", I read "wrong" as "unethical", "unscientific", or at the very best "incompetent". Your criticism assumes it meant "something which eventually turned out not to be how reality works".
Immune system genes are often under balancing selection - i.e. the rarest alleles are favoured (until, due to this favouring, they cease to be rarest, then other alleles are favoured.) An infusion of new different alleles from Neandertals could be favoured simply because they are different, not because they are evolved to European conditions.
Testing between these hypotheses seems difficult. The 'balancing selection' hypothesis predicts that the genes will readily spread back into Africa, whereas the 'evolved for European conditions' predicts they will not. The problem is that you need some neutral mutations that arose in Europe at the same time as a 'control' for comparison purposes. I'm not sure how to identify such mutations, but I expect it could be done.
There is another obvious point in history where such a gene transfer could have occurred. European conditions favour light skin, and Neandertals had been hanging out there for some tens of thousands of years before modern humans turned up and so had evolved light skin. These newcomers, having recent ancestry in Africa, were probably dark skinned. Interbreeding could easily have introduced the beneficial-to-European-conditions light skin mutations into the modern population.
My memory of the literature (which I have followed just a little bit, not closely) is that this did not happen - genetic analysis shows that modern Europeans and Neandertals acquired light skin through different mutations. However, Wikipedia says this is still under debate.
I explicitly did so.
This is a silly objection. That isn't how payback times are used.
Payback time is a quick indication of return on investment. You then compare that return on investment with the other options available to you, such as leaving the money in the bank.
If you included interest rates in payback time, you'd need to be constantly adjusting it as rates changed, and it would differ for different entities depending on their access to finance. Instead you keep it simple, and each entity has its own idea (based on circumstances and current interest rates) of what the effective payback time is of leaving the money in the bank (or not borrowing it, or investing it in other opportunities.) (For example, a start-up is likely to require a very short payback time - they're strapped for cash and are trying to get their Big New Idea to market where they hope it will make a fortune. Up-front money is then very expensive compared to down-the-road money. For them, it may make sense to lease a supercomputer even if buying it would have a two year payback time.)
What is missing from this analysis is depreciation of assets. After 6.4 years, money in the bank will have depreciated much less than the solar cells. Payback time is a rough guide - it tells you whether it is worth your while doing a more detailed analysis including finance cost, depreciation, tax implications etc.
They aren't. They're using an established term "energy payback". The authors wrote an analysis which will be useful to many people but used the word "payback" in a way which does not match your preconceived notion of how it should be used. For this, you label them "charlatans".
So all the people interested in energy payback times should not be able to publish or read about it because you've claimed ownership of the word "payback" and won't license them to use it? They should use a less clear term to express their meaning because otherwise some random idiot who reads technical papers might make the leap "payback = money", despite the term "energy payback" being self explanatory?
Had you argued that because this is "energy payback" rather than financial payback, it isn't worthy of being reported on Slashdot, I could respect your argument. Instead you label people charlatans because what they discuss is not what you're interested it.
Oh good, I'll just print up a bunch of fliers saying you torture kittens and set fire to orphanages and post them around your home town. Because nobody has heard of you and I'm not a publicly listed company, it will be 'opinion' rather than 'libel'.
I have no idea whether this guy's claims are justified, but neither do you. My liking Wikipedia does not therefore mean that the facts or the law are on the side of Wikipedia.
When El Nino leads to a new record high temperature by a large margin (for argument's sake, in 2015), the denialists will quietly adopt this as their new standard for 'normal' and in 2025 they'll be saying "warming is a hoax because temperatures haven't risen on average since 2015."
http://xkcd.com/1321/
I believe you've just taken what was intended as reductio ad absurdam seriously.
No, as you would have seen if you'd read the article. By their numbers, about 60% of the energy cost of streaming is in the data center.
Whoosh