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Testing Quantum Behavior — From Earth to the ISS
Posted by
timothy
on Tue Jun 10, 2008 08:44 AM
from the houston-will-you-have-heard-me dept.
from the houston-will-you-have-heard-me dept.
KentuckyFC writes "Einstein famously believed that the instantaeous effect of quantum entanglement would allow 'spooky action-at-a-distance' in violation of special relativity. Every test of entanglement on Earth has so far agreed with quantum mechanics but naysayers continue to point out various loopholes that might allow the results of these experiments to be determined in advance rather than instantaneously as QM suggests. Today, an international team of scientists is proposing the mother of all entanglement experiments, to be performed in space. The plan is to send entangled photons between an observer on the ground and one on the International Space Station. By the peculiarities of special relativity, the high relative velocity between the observers means that both will always be able to claim to have carried out their measurement first, thereby ruling out the naysayers' arguments (abstract). The experiment, called Space-QUEST, would be housed aboard Europe's Columbus module and would give the much-derided ISS a stab at doing some decent science for a change."
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Science coverage on /. is crappy (Score:5, Informative)
Sure it would be nice to do even more, and sure the costs are high (in part due to the STS, a nice but incredibly inefficient LV), but all this group-thinking about the "white elephant" ISS is akin to saying that kernel programming is easy. It's stupid, flat wrong and insulting for the people that get a lot of good work and science done.
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Re:Science coverage on /. is crappy (Score:5, Informative)
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Re:Science coverage on /. is crappy (Score:5, Informative)
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Re:Science coverage on /. is crappy (Score:4, Funny)
W
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Re:Science coverage on /. is crappy (Score:4, Insightful)
The facts [sciencedaily.com]: "On this first ATV mission, Jules Verne will deliver 4.6 tonnes of payload to the ISS, including 1 150 kg of dry cargo, 856 kg of propellant for the Russian Zvezda module, 270 kg of drinking water and 21 kg of oxygen. On future ATV missions, the payload capacity will be increased to 7.4 tonnes.
About half of the payload onboard Jules Verne ATV is re-boost propellant, which will be used by its own propulsion system for periodic manoeuvres to increase the altitude of the ISS in order to compensate its natural decay caused by atmospheric drag."
Also [itwire.com]: On April 25, 2008, the European Space Agency announced that earlier in the day its first automated transfer vehicle (ATV), the "Jules Verne," increased the altitude of the International Space Station by about 2.8 miles (4.5 kilometers)--the first time an ESA craft had performed such an important task. The 12.3 minute maneuver was directed by ESA's ATV Control Center, which is located in Toulouse, France.
At 6:22 a.m. Central European Summer Time (CEST) (0422 GMT), controllers turned on two of the Jules Verne's four main engines. The two engines produced a thrust that increased the station's speed by about 8 feet per second (2.65 meters per second).
To achieve this re-boost in altitude, the ATV consumed 537 pounds (244 kilograms) of fuel. In all, the ATV carries about two metric tons (about 4,400 pounds) of propellant for re-boost activities.
After the burn was completed, the new altitude of the ISS became 212.5 miles (342 kilometers) above the Earth's surface.
The Space Station needs periodic boosts to raise its orbit because its orbit decays slowly over time due to a very small amount of atmospheric drag on the large structure as it orbits about the Earth.
In the past, the RSA Progress, the NASA Space Shuttle, or the ISS itself has performed such a maneuver. However, only RSA Progress and the ESA ATV are able to re-boost the space station to such a high level due to the amount of fuel onboard each vessel.
The Jules Verne ATV (ATV-001) will perform three additional re-boost maneuvers over the next few months: on June 12th, July 8th, and August 6th. Normally, the space station tries to keep at an orbital height of about 211 miles (340 kilometers) above the Earth's surface.
Later in August 2008, the Jules Verne, loaded with waste and unneeded materials from the space station, will be undocked from the ISS. The ATV has a capacity of carrying up to 6.3 metric tons (13,900 pounds) of unwanted material from the Station."
So what most people don't realize is that JV carries a LOT more (dense, low-volume) as mass as fuel for reboost than it does anything else in that cool pressurized comparment it has the astronauts go in. I understand that the JV maneuvers were held off to allow Shuttle attachment of KiBo at the lower and easy to reach altitude. But my point is that things are only going to get worse and will ultimately I think go beyond what JV is designed or funded to do to keep ISS up.
JV is an experiment in European autonomous docking technology, not an integrated reboost system. I have yet to see any plans for how many JVs will be flown in the long run - currently there are only 4 more in the pipeline thru 2015. The numbers above represent the data required to figure out just how many JVs will be required to keep ISS up for X number of years. I predict that when that calculation is finally run - and when NASA explains to ESA that there will be zero American funding to keep the JV production line running - that ESA will say, OK, we ain't payin no Euros to keep this junkheap up either, which side of Hawaii do you want us to splash the ISS in?
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Also, what ever happened to the possibility of using solar-powered electrodynamic tethers to reboost the ISS?
Re:Science coverage on /. is crappy (Score:5, Informative)
The parent post is overrated. It's not entirely correct and it's not very coherent.
That is before any of the hardware had been launched. But it's unsurprising that the OP could be dissatisfied with the experience. Aside from being a government program and all the cliches that entails, the ISS has gone through many redesigns, and the effort of cooperating internationally has been an added source of delay and cost. He's not alone in such criticisms and the ponderous nature of government programs is one of NASA's biggest problems.
The shuttle is a much more expensive spacecraft to operate than the ATV. The shuttle's advantages are it's manned, it is a versatile work platform, and it can carry cargo back to earth. It's overkill for basic resupply. Although Jules Verne didn't because there was a large amount of pressurized cargo on board, the ATV can carry up to 4.7 tonnes of spare propellant...much more than either the shuttle or Progress. There may also be a commercial option available for re-supply and reboost in the next 3-4 years through the COTS program.
There is absolutely nothing wrong with Soyuz or Orion performing crew rotation. Both of these craft have lower operating costs than the shuttle, and lower projected loss of crew probability.
Total BS. The international partners are well aware of how much reboost the ISS needs and are planning accordingly. There is no secret. Progress, ATV, or the shuttle alone can't do all of the reboost, but combined they can. Also, once construction is finished, the ISS will be boosted to a slightly higher orbit to reduce the effect of drag. Lastly, the ISS is at nearly maximum drag, with only one more solar array to be added, but still growing in mass. Added mass works out net neutral. The momentum reduces the effect of drag just as well as it reduces the effectiveness of reboosts.
This statement, at least, is based mostly in fact. ISS is somewhat contentious at NASA, but it has its supporters and detractors. There will be quite a few glad not to have to divert resources to it, and plenty others frustrated by the loss of a unique laboratory environment and work platform. I doubt hardly anyone there would argue that it's completely without value, but many feel the money would be better spent elsewhere.
The contention of crooked accounting is unsubstantiated. If there's crooked accounting it goes on at lower levels, but the OP has provided no evidence of it. NASA funds are accounted for at the higher levels in the annual budget allocations. The problem with accounting for exact costs is that ISS draws on programs that have their own independent budgets. How much of the cost of the shuttle return-to-flight program should count towards the ISS, for example? More on cost here. [wikipedia.org]
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Re:Science coverage on /. is crappy (Score:5, Insightful)
I agree with the accusation that the ISS is a white elephant. Your claim of "hundreds" of experiments is padded by a considerable number of low value experiments such as archiving (in addition to the regular sampling if I read the list correctly) fluid and tissue samples from the crew of each expedition (there have been 17 returned expeditions so far, hence, 17 "experiments"). Let's put this in perspective. By the time the ISS has run through 2016, it'll have consumed around $150-160 billion between NASA and the other participants. This includes a decade or so of the Space Shuttle which we could have phased out in 2000 or earlier, if it wasn't for the ISS. Even after completion, it'll cost almost $2 billion dollars a year to maintain.
In comparison. including launch costs the MIR station cost a few billion and the first serious NASA proposal in the mid-80's was around $12 billion in today's dollars, including launches. If NASA had gone with a scaled down station, it would have been completed years ago and generating a similar quantity of useful science (over its lifetime) for a small fraction of the cost of the ISS. The high maintenance cost means that there's a good chance that it'll be cheaper to splash the ISS and launch a new station, than to leave the ISS up there. Finally, I think it's clear that the primary purpose of the ISS has always been to extend the lifespan of the Shuttle (and deliver public funds to NASA contractors) rather to do anything useful in space. In that, it has been remarkably successful.
I find it odd that ISS supporters have to resort to the numbers game and other vague arguments (like lauding the value of "international cooperation"). If you can't find 5 or so big reasons that justify the ISS, you're not going to make up the difference with thousands of mediocre ones. What justifies almost $2 billion a year in maintenance and the huge opportunity cost of putting almost a sixth of a trillion dollars into this project? As I see it, we could have done a hell of a lot more in space with that money.
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Here's the list (Score:3, Interesting)
ISS Experiments by Expedition [nasa.gov]
Please note the count of experiments currently stands at 561, and the focus ranges from virology, to fluid mechanics, to relativity, to astronomy, and even engineering validation (not simply of space station components, but also of fully independent technologies). That's nothing to sneeze at.
And while a fairly large portion of them are relatively minor or PR projects
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Note that Fox did not deny they were falsifying the news story on BGH; they argued only that what they did was not covered by the "adopted rule" of the FCC. A purely technical legal argument to defend broadcasting information they intentionally distorted and knew was wrong.
And that is a new organization?
h [foxbghsuit.com]
Re:Science coverage on /. is crappy (Score:5, Informative)
1, Fox News actually went to court and won an advance judgment that said, even if it could be shown that the newscasters had deliberately lied about a concealed source being reasonably unbiased, and it was proved that the source actually worked for a political party and was paid to make the claims that it made, Fox would still be protected by the normal laws about concealing the identity of sources and this situation wouldn't constitute possible malice with respect to libel laws. Name another news agency that has even sought such a protection.
2. In 2002, there was a study of the media where the only thing that was examined was accuracy of attribution. That is, if a news source quoted a person and said that person was a lawyer in the state of New Jersey, the study checked to see if the person was really liscenced before the New Jersey Bar at the time. If they said a source was a Vice President at a fortune 500 company, the study checked to see two things - was that company really in the 500, and was the guy's title really VP and not Assistant VP or similar. NPR and BBC both scored in the 3.8 to 4 out of a possible 5 range. PRI, MSNBC and ABC ran somewhere near the middle. Where did Fox score? 2.2 - right next to Al-Jazera!
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Re:Science coverage on /. is crappy (Score:5, Insightful)
Forgive my modification to your quote, but I think that print offers better coverage of science issues. And while Fox News may report science news as well as CNN does, an astrologer reports as much science as either one of them as well. Fox News is crap. If other TV channels are also crap, well, good job my friend, you're still watching crap.
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Slashdotted already? (Score:5, Funny)
Re:Slashdotted already? (Score:5, Funny)
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Derision (Score:4, Insightful)
That won't necessarily help with the derision, as nobody denies the fact that interesting experiments are possible in space. The main point of contention will still be if you need to keep live persons there continuously to perform them. It'd have to be shown that a satellite or a simple orbiting mission couldn't have performed the same experiments for a fraction of the total costs.
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Well, the real question would be how many experiments do we neeed to do aboard the ISS before it becomes cheaper than sending up mission after mission after mission.
Re:Derision (Score:5, Insightful)
But the ISS is not only about science, it's also about engineering and learning how to live for long periods off the world (the MIR was pioneer, but its design and MO would be too dangerous to use beyond Earth's orbit). The next target will be the Moon and then probably Mars, but we had to learn how to walk before we can run.
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Re:Derision (Score:4, Informative)
That won't necessarily help with the derision, as nobody denies the fact that interesting experiments are possible in space. The main point of contention will still be if you need to keep live persons there continuously to perform them. It'd have to be shown that a satellite or a simple orbiting mission couldn't have performed the same experiments for a fraction of the total costs.
I think it's like a zoo. Maybe the animals inside are being held in some sort of unfair captivity (I tend to think that in modern zoos most animals are pretty satisfied, but let's not go into that), but the interest and money generated by those animals creates the world's largest resource for saving their wild relatives.
Even if the ISS is never used in a way that provides more direct scientific knowledge per euro than unmanned missions, I believe it's worth it in the long term.
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Spooky (Score:5, Informative)
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Still a naysayer (Score:2)
Robust enough? (Score:5, Interesting)
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In order to get to the bottom of this.... (Score:2)
Why not go further? (Score:2)
Or perhaps on the moon.
Or mars.
This is actually a fairly exciting bit of science.
Noooo! (Score:5, Funny)
Re:How do you entangle a photon in the first place (Score:5, Funny)
It's super effective!
Photon capture device go!
You entangled a photon!
It was added to your photondex.
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Just wondering if you could put one of the quantum photons in an optical switch, and perhaps use the the reading of the other photon to flip a bit. That might actually be useful. If this were viable, NASA could have something better than radio for their next generation of probes. Now if they're only watching the thing bounce around randomly on its own, and it happens to be in synch with its paired photon - I'm not sure how useful that could be.
Now, can someone untangle the that for me?
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Re:Could it be useful? (Score:5, Informative)
I've not RTFA - it's down - but basically the EPR effect allows someone to create two photons and then measure if their polarization is H or V. The result is completely random BUT, both photons will always give the same result.
Now Alice measures her photon first and lets say we get H, then Bob's photon must instantaneously turn into H (previously it was a mixture of H and V - the dead and alive cat) so that when he measures his photon he also gets H.
What's already been done is to ensure that Alice and Bob decide what measurement to do, and make the measurement, so close to the same time that it's impossible for there to be any way for Bob's equipment or photon to "know" what Alice is going to do (or vice-versa) except at superluminal velocities.
But because Alice and Bob are in the same inertial frame there's still, at least in theory, a concept of who did the measurement first and who did it second. (Alice and Bob can have synchronized clocks and record the time they did the experiment. Then they can, using normal communication, tell each other what time they did the experiment and they'll both agree who was first and who was second.)
What this experiment will do is mean that Alice and Bob won't agree about who was first and who was second. Alice and Bob's clocks cannot remain synchronized, so that according to Alice, and people sitting next to her, she did the measurement first, but according to Bob, and people sitting next to him, he did the experiment first. And BOTH will be correct because the two measurements are space like rather than time like.
Tim.
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Re:Could it be useful? (Score:4, Interesting)
Just to clarify this paragraph because I've realized it's confusing.
Alice and Bob both randomly decide to measure the H/V polarization or the +/- (45 degree) polarization.
Then they get together and compare results. Where one has measured H/V and the other +/- then they throw the results away because they don't tell them anything useful, but where they've made the same measurement they find they always get the same (or opposite) results.
It's when they make the measurement that neither they, nor their equipment or photon can "know" what the other is doing.
There's also something called Bell's inequality that basically proves that the results of all of Alice and Bob's possible cannot be "known" by the photon ahead of time. (no local hidden variables).
Tim.
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Am I mis
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It doesn't (there are other points where GR and QM conflict, but entanglement is not one of them ). Einstein thought it did because he assumed that any such interaction would be deterministic and could hence be used for communication (THAT would break GR ). Essentially Einstein never liked the idea that the universe was based on randomness, hence the famous "god does not throw dice with the universe" quote. As a consequence he repeatedly tried to disprov
Re:Could it be useful? (Score:4, Informative)
1. Quantum Mechanics.
2. Locality.
3. Realism.
All the experiments performed so far strongly support QM, so we can't dismiss that. If locality is false then we have Einstein's spooky action at a distance and a conflict with GR. If realism is false...then nobody knows where the hell we are, or what we are.
But one of them *has* to be wrong. All these experiments are trying to prove is which one.
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Re:Could it be useful? (Score:5, Interesting)
QM tells us that when you have two entangled photons and measure both of their polarizations, the chance the results will correlate is the square of the cosine of the difference in angles between the two polarizers . If you measure them at the same angle, the results always correlate. If you measure them at 45 degrees apart, the measurements correlate 50% of the time. If you measure them 90 degrees apart, the measurements never correlate (the results are always opposite). No matter how you look at it, this means either the results are predetermined at the time the photons are created based on the angles the polarizers will be at the time the measurements are taken, or that one measurement somehow influences the other later so the past isn't immutable.
Either way you look at it, it means the universe doesn't work the way we expect it to. If you're a glass-half-full person you want to believe in FTL and time travel, and if you're a glass-half-empty person then you think maybe the universe is deterministic.
That's why this stuff gets everyone who understands its implications all in a tizzy.
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Re:Could it be useful? (Score:5, Insightful)
we know this because in a quantum superposition, different possibilities in the superposition can interfere with other possibilities, making certain results more or less likely. this is shown by the double-slit experiment [wikipedia.org]. shooting photons at a screen through two slits produced not two stripes like you'd expect, but several stripes. this is because each photon went through 2 waves of possibilities, one through each slit, and the waves then collided with each other, making certain ares of the screen more likely to be hit than others.
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Re:Could it be useful? (Score:5, Informative)
Yes, you're missing something fundamental.
Going back to one photon.
We'll have four polarization states H, V (the normal horizontal and vertical polarization) and +, - the 45 degree polarizations.
Now Alice produces a stream of H photons and sends them to Bob. Now if Bob measures to see if they're H/V then he will always get H.
But if Bob measures if they're +/- he'll get 50/50 + and -, with each individual photon being + or - at random.
After measuring +/-, if Bob then remeasures H/V he'll again get 50/50 H and V. The measuring of +/- destroys the knowledge about H/V
If Bob measures at an angle other than 45 degrees then he'll get different proportions but he'll get sin^2 theta with one polarization and cos^2 theta with the other polarization.
Now lets consider entangled photons that will always give the same result for Alice and Bob. Initially we'll assume that Alice will always measure the horizontal polarization (0 degrees) Now lets consider that the photon "knows in advance" whether it will go through a horizontal polarizer i.e. it has (an infinite number) of hidden variables. Regardless of what measurement Bob does, an ensemble of photons can distribute values amongst these hidden variables so that Bob gets the expected correlations relative to Alice and the angle of his measurement.
But now let Alice vary her angle as well. Now the correlation depends on the difference in angle between Alice and Bob. But that angle isn't known (and hasn't even been decided) at the point the photon has been created. It could have a big "look up table" saying "If Alice angle is n and Bob angle is m then do/don't go through Alice's filter and do/don't go through Bob's filter BUT the photon that arrives at Bob's detector has to know what measurement Alice will/has done and the photon that arrives at Alice's detector has to know what measurement Bob will/has done.
But because Alice and Bob independently randomly decide what angle to measure "long" after the photon was created and their independent decisions are made so close together in time that neither can know what the other has/will do when they make their measurement due to the speed of light limit then there is no way for the photon to use its "lookup table" and get the correct statistical results.
It doesn't matter how you construct that "lookup table", unless you allow some sort of faster than light communication, using the lookup table will give different results to QM.
If you want the formal maths for that bit of hand waving then lookup Bell's inequality. He actually deduced the inequality that could be tested to prove no local hidden variable theorem was consistent with the results of QM based on measuring particle spins while most of the tests that have been done have used polarization of photons but the underlying theory is the same.
These experiments have already been done, and Bell's inequality has come down on the side of QM. Because Alice and Bob make their measurements so close together in time, not all observers will agree which one is first but (perhaps unfortunately) Alice and Bob will agree who was first and who was second. What this experiment does is close even that loophole - even Alice and Bob will be unable to agree who made the first measurement and who made the second.
Tim
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Exactly. But QM says they are.
H polarized photon = Cat dead. V polarized photon = Cat alive. 45 degree polarized photon = Cat dead, 135 degree polarized photon = Cat alive.
Until Alice and Bob make their measurements we really do find that the cat is both dead and alive.
But what does "measurement" mean? If we really were using dead/alive cats to do this experiment (currently we lack the ability to keep something the size of a cat in a superposition of states) then presumably
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Or, at the very least, they remembered to take jockstrap from locker.