I have to wonder why the idea of adaptive vsync wasn't thought of earlier or implemented into display standards earlier. It just seems like such an obvious idea once you've heard of it. Surely someone else in the graphics/display industry must have had the idea before NVidia?
It's just a vicious compatibility circle.
CRTs have a fixed frame rate for technical reasons. Therefore graphics cards have a fixed frame rate to support CRTs Therefore LCD displays have a fixed frame rate to support graphics cards Therefore graphics cards continue to have a fixed frame rate etc...
New stuff has to remain compatible with old stuff, so nobody even thinks of breaking the circle. Until now, fortunately.
Nah, the engine will normally start again once you're back at 1g. And 0g is not so bad anyway, as long as you don't get into the negative g range the engine will probably even keep running normally if it's just a few seconds. And you need a fairly high speed to get anywhere near 20 seconds, a gravity-fueled rental plane is more likely to give you 5 seconds or so. No problem for the fuel system.
Slightly more annoying is the oil system: you often end up with oil all over the engine cowling and having to clean that up before anyone notices and gets really angry at you. Don't ask me how I know;-)
"Space itself expanding" is just a term made up to explain these things to normal people in popular articles. There's no such thing as "space itself", what they really mean is "the coordinate system we happen to be using to describe things in an efficient way that's easy for us to use".
Define space time coordinates according to Special Relativity, relative to our position and assuming a constant speed of light, and you end up with a perfectly valid model of the universe in which nothing goes faster than light, all the laws of nature work correctly, but everything looks really distorted because of Lorentz contraction. The further away you "look" (in a mathematical model, not having to wait for light to get here), the faster things are flying away from us and the slower local time is therefore going. At a large distance away from us, the age of the universe multiplied by the speed of light, things are flying away at the speed of light (but never faster), are infinitely Lorentz-contracted, and are frozen in time. Over there, the big bang is still beginning right now.
Even though this model is a perfectly valid and correct way to describe our universe, cosmologists don't like it very much. They prefer a different kind of coordinates in which the speed of light is the same everywhere relative to the local expanding universe, not relative to us. General Relativity allows you to do this easily, it's just a matter of putting different labels (coordinates) on things. Same universe, different labels for distance and time, like using a ruler that looks normal in the middle but has marks closer and closer together as you move from the center. In that model (which is still the same universe), things look roughly the same everywhere, without Lorentz contraction (except for local speeds relative to local space, of course) and the universe is truly infinite. Things now do fly away from us faster than light, simply because we are measuring their speed differently (with a distorted ruler).
That's what "space itself" really means. It's all just about the coordinates which we happen to choose. It's not some kind of background aether or anything like that. At least, as far as we know so far.
So in the early universe, things may very well have gone faster than light depending on what kind of coordinate system you're using to describe it. Either it was slower than light but distorted because of the enormous amount of energy and high speeds involved, or it was going faster than light and looked differently and far more easy to describe mathematically. Nature doesn't really care.
The Google car can certainly avoid obstacles, I was just saying it's unlikely to make sophisticated decisions about which "obstacle" (including humans) to prefer.
Is there anything not directly pi-related (i.e. not something like "I wonder whether or not the digits of pi are random" or "look how many digits of pi this computer can calculate") in which it's actually usefull to have more than a few hundred digits of pi? Just curious, not being sarcastic.
Why does that show most people are not ethical? Rather depends on what kind of ethics you choose, ethics is not an exact science and has evolved quite a bit over time, back and forth. I find it perfectly ethical to kill the escaped criminals rather than the mother with child and foetus.
Now if it was someone elses wife with son and child, exactly the same but just not your wife, it would start to become a bit more difficult.
What if one car has two guys with multiple convictions for armed robbery and the other has a working dad with a family and three kids at home? OK, the algorithm would have to be pretty sophisticated to detemine that, but who knows...
Or something slightly more realistic, a car with an couple of 80 year olds versus a 25 year old mom of three? Should the car kill the mom rather than the couple that will be dead in less than 10 years? One death is worse than two, no matter what?
Or yet another one, what if two people cross the street without looking, and the car swerves off the road to avoid them and rather kill one person who was walking on te pavement, not doing anything wrong? One casualty is better than two, right?
Those are just questions, mind you. Only shows how "minimize casualties" is not always so clear cut.
I remember a study not long ago that compared the smoothness of traffic in different simulated scenarios. The worst was when nobody followed the rules, that resulted in total choas and mayhem. A much better scenario was when everybody followed the rules. But somewhat suprisingly, the best results were achieved when most people followed the rules but a significant fraction did not! The rule breakers helped fill in gaps and actually caused traffic to flow more smoothly.
One of the reasons may be that the officers are specifically told not to take risks, and can even be punished if they do so anyway. If they fire even one bullet, or if they somehow provoke a violent situation that could have been avoided by simply letting the thief go about his business, they will be subject to an investigation. In today's lawsuit-happy society, if an officer gets killed or injured, the department may be sued. So the chiefs tell their officers to stay away from danger, and most officers are happy to comply. If you don't only risk your life but ALSO risk being suspended for taking a risk you shouldn't have taken, the decision becomes really easy.
We check the tires and look for leaks before every flight, but the wheel well is above eyesight level and pretty big. You have to actually climb up in there or open the landing gear doors to peek inside. That's normally not required. Everything that needs to be checked regularly, is visible from the ground.
Yes, but I was talking about the EXTRA encryption they used to apply to e-mail attachments. The full disk encryption is still present, that hasn't changed. I was just wondering why they bothered to apply an extra encryption step to e-mail attachments if by breaking full disk encryption you could get the passcode and break all the other encryption too without extra effort.
OK, so if I understood correctly, the entire "disk" (SSD) is encrypted with a key that can be unscrambled with the passphrase (just 4 digits for most people), and Apple used to also encrypt e-mail attachments one extra time on top of the full disk encryption, but now no longer does.
Can anyone explain what the added value was of the extra encryption they used to add and that is apparently so sorely missed now?
After all, what were they using to encrypt those attachments? Errr... the same passphrase, right? After all, I can boot up my iPhone, enter my passphrase, and read all my mail. No other extra strong authentication needed to get to e-mail attachments. If someone can get the password by brute-forcing the full disk encryption, they can then use that password to simply log in and open Mail.
Ergo, the extra encryption was totally useless and just a waste of battery power. Or am I missing something here?
Dragonflies certainly seem to be pretty good at judging the distance to nearby insects to attack them. And hoverflies as well, are really good at hovering in place and chasing other insects away. Actually, many insects eem to be able to judge distances quite well. Just landing on a flower or a turd wouldn't be easy without stereoscopic vision.
On the other hand, quite a lot of insects fly round in such a clumsy manner that you wonder whether they even have eyes at all. Crane flies, beetles, heteroptera,...
In the video, they said that the ionic liquid is like a bunch of little magnets sticking together but still able to move around each other. They stick together so well that the fluid wouldn't even evaporate in outer space. How can it be less cohesive than water, then? I know water molecules are little bipoles too, but water certainly does evaporate in outer space, so I would assume that the cohesive force is a lot less, no?
And the part about the lack of hydrostatic pressure... Do you mean the tubes have to be inserted deeper into the liquid? I don't think that matters at all, since the pressure in the tube as it passes through the surface will always be the same as the pressure above the surface. It doesn't matter how deep or wide the reservoirs are.
I do understand the conclusion: some siphons can work using the tensile strength of the fluid instead of (or in addition to) atmospheric pressure, but that doesn't mean you shouldn't at least mention the requirement.
Yes, it shows that you can siphon an extremely cohesive ionic liquid up to a very small height of just a few cm. The liquid would probably break up if you tried more than 10 cm or so, and you certainly wouldn't get anywhere near the 10 meters you can siphon ordinary water up to under atmospheric pressure.
The liquid is special because it is so cohesive that it can actually stay together under negative pressure. That is quite extraordinary, but certainly a very limited effect. Normal fluid breaks up as soon as you try to pull it apart, and so will even the ionic fluid if you tried only a little bit more height.
The ionic liquid they used for that experiment is a particularly cohesive liquid that even stays together under a small amount of tension (negative pressure). They only managed to get it up a few cm, though. Too bad they didn't try higher, I'm sure the fluid would break up at around 10 cm or so, probably even lower. Certainly nowhere near the 10 meters you can siphon water up to using atmospheric pressure.
It's really just like a drinking straw: when you suck, you reduce the pressure in your mouth (still a positive pressure, just less than normal) so that the atmospheric pressure pushes the liquid into the straw. In a siphon, gravity is providing the suction. But you can't suck (much) more than atmospheric pressure because the fluid breaks up when the pressure reaches zero. Except for very special liquids that can go slightly below zero, but not much.
The water breaks up because the pressure inside the tube reaches zero. Water doesn't stay together under negative pressure. Boiling has little to do with that.
You can siphon up a very small height, just a few cm, by using a particularly cohesive ionic fluid. The pressure in the liquid in the tube will actually become negative in that case, it's being pulled apart and only staying together because of the cohesion between the molecules. But that force could never hold more than a few cm, certainly not the 10 m that you can siphon water up to under atmospheric pressure.
The water in the experiment was still way above boiling point: at 0.18 atmosphere, water boils at a temperature of more than 50C. Of course the pressure up in the tube gets lower than 0.18 atm, but the whole point is indeed that the column breaks up when the pressure in the tube approaches zero. Not because the water boils, but simpy because it won't stay together. Unless you have a particularly cohesive fluid like some ionic fluids. You can use those to actually siphon up a few cm in a vacuum because they can stand a small amount of tension (negative pressure) without breaking up. But you'll get nowhere near the 10 meters you can get under atmospheric pressure.
And how high could you pull up the liquid? I bet it wasn't more than a few cm. At least it was in the experiment I saw on youtube. And, like you said, that was using an extremely cohesive ionic liquid.
I really wish someone would try that experiment with an apex more than 10 cm above the liquid surfaces. I'm pretty sure the fluid will break up.
Using atmospheric pressure, though, you can siphon ordinary water up to 10 m high.
Look at the replies to that post you referenced, explaining why it's wrong.
Granted, the video of that experiment does show that, if you have an extremely cohesive liquid (an ionic liquid, comparable to a bunch of magnets much stronger than water molecules), you can get it to siphon up a few cm using the cohesive force. But I bet they couldn't get it up to even 10 cm or so.
A normal siphon, under atmospheric pressure, can siphon water up to 10 m which also happens (coincidentally?) to be the height of water that corresponds to one atmosphere of pressure. In the Nature experiment referenced in the article, the water in the 1.5 m siphon broke up when they reduced the pressure to about 0.18 atm. How can you then say that atmospheric pressure has nothing to do with it?
I'll give you a car analogy:
Suppose we see a bunch of cars traveling up a 2000 meter mountain. I would say that their engines are pushing them up the hill. You would say that, no, their engines have nothing to do with it. You would then show an experiment where a car traveling at high speed would cut it engine and then coast up and down a small 20 meter high hill. See, cars don't need engines!
Yes, you can siphon up a very small height (just two centimeters or so) using an extraordinarily cohesive liquid. That doesn't imply that siphoning has nothing to do with atmospheric pressure.
Gravity is responsible for lowering the pressure in the outbound leg of the siphon, but you still need atmospheric pressure at the inlet to push the water over the top of the siphon. You can't siphon up more than about 10 m under normal atmospheric pressure.
So in a way, it's not really wrong to say that atmospheric pressure is pushing the water over the top. Just like atmospheric pressure pushes liquid into a drinking straw as well. Would you say that a drinking straw has nothing to do with atmospheric pressure?
Of course the exact value of atmospheric pressure doesn't matter much as long as it's enough, the flow rate will only depend on the difference in height between the two water levels, but without enough atomospheric pressure the siphon stops working. Which was clearly shown in the experiment described in Nature as well. In fact that experiment dispoves rather than proves his point.
Slashdot Mirror
I have to wonder why the idea of adaptive vsync wasn't thought of earlier or implemented into display standards earlier. It just seems like such an obvious idea once you've heard of it. Surely someone else in the graphics/display industry must have had the idea before NVidia?
It's just a vicious compatibility circle.
CRTs have a fixed frame rate for technical reasons.
Therefore graphics cards have a fixed frame rate to support CRTs
Therefore LCD displays have a fixed frame rate to support graphics cards
Therefore graphics cards continue to have a fixed frame rate
etc...
New stuff has to remain compatible with old stuff, so nobody even thinks of breaking the circle. Until now, fortunately.
I certainly wouldn't pay 250k to go into space without being able to leave my seat.
Nah, the engine will normally start again once you're back at 1g. And 0g is not so bad anyway, as long as you don't get into the negative g range the engine will probably even keep running normally if it's just a few seconds. And you need a fairly high speed to get anywhere near 20 seconds, a gravity-fueled rental plane is more likely to give you 5 seconds or so. No problem for the fuel system.
Slightly more annoying is the oil system: you often end up with oil all over the engine cowling and having to clean that up before anyone notices and gets really angry at you. Don't ask me how I know ;-)
"Space itself expanding" is just a term made up to explain these things to normal people in popular articles. There's no such thing as "space itself", what they really mean is "the coordinate system we happen to be using to describe things in an efficient way that's easy for us to use".
Define space time coordinates according to Special Relativity, relative to our position and assuming a constant speed of light, and you end up with a perfectly valid model of the universe in which nothing goes faster than light, all the laws of nature work correctly, but everything looks really distorted because of Lorentz contraction. The further away you "look" (in a mathematical model, not having to wait for light to get here), the faster things are flying away from us and the slower local time is therefore going. At a large distance away from us, the age of the universe multiplied by the speed of light, things are flying away at the speed of light (but never faster), are infinitely Lorentz-contracted, and are frozen in time. Over there, the big bang is still beginning right now.
Even though this model is a perfectly valid and correct way to describe our universe, cosmologists don't like it very much. They prefer a different kind of coordinates in which the speed of light is the same everywhere relative to the local expanding universe, not relative to us. General Relativity allows you to do this easily, it's just a matter of putting different labels (coordinates) on things. Same universe, different labels for distance and time, like using a ruler that looks normal in the middle but has marks closer and closer together as you move from the center. In that model (which is still the same universe), things look roughly the same everywhere, without Lorentz contraction (except for local speeds relative to local space, of course) and the universe is truly infinite. Things now do fly away from us faster than light, simply because we are measuring their speed differently (with a distorted ruler).
That's what "space itself" really means. It's all just about the coordinates which we happen to choose. It's not some kind of background aether or anything like that. At least, as far as we know so far.
So in the early universe, things may very well have gone faster than light depending on what kind of coordinate system you're using to describe it. Either it was slower than light but distorted because of the enormous amount of energy and high speeds involved, or it was going faster than light and looked differently and far more easy to describe mathematically. Nature doesn't really care.
O, come on, this has literally been available since the beginning of time. Even before.
The Google car can certainly avoid obstacles, I was just saying it's unlikely to make sophisticated decisions about which "obstacle" (including humans) to prefer.
Is there anything not directly pi-related (i.e. not something like "I wonder whether or not the digits of pi are random" or "look how many digits of pi this computer can calculate") in which it's actually usefull to have more than a few hundred digits of pi? Just curious, not being sarcastic.
Why does that show most people are not ethical? Rather depends on what kind of ethics you choose, ethics is not an exact science and has evolved quite a bit over time, back and forth. I find it perfectly ethical to kill the escaped criminals rather than the mother with child and foetus.
Now if it was someone elses wife with son and child, exactly the same but just not your wife, it would start to become a bit more difficult.
Depends how much you hate your wife, I suppose...
I think he's talking about technology 50 years from now. An autonomous Google Prius is unlikely to make that kind of decisions any time soon.
What if one car has two guys with multiple convictions for armed robbery and the other has a working dad with a family and three kids at home? OK, the algorithm would have to be pretty sophisticated to detemine that, but who knows...
Or something slightly more realistic, a car with an couple of 80 year olds versus a 25 year old mom of three? Should the car kill the mom rather than the couple that will be dead in less than 10 years? One death is worse than two, no matter what?
Or yet another one, what if two people cross the street without looking, and the car swerves off the road to avoid them and rather kill one person who was walking on te pavement, not doing anything wrong? One casualty is better than two, right?
Those are just questions, mind you. Only shows how "minimize casualties" is not always so clear cut.
Yeah, those were the good old days...
I remember a study not long ago that compared the smoothness of traffic in different simulated scenarios. The worst was when nobody followed the rules, that resulted in total choas and mayhem. A much better scenario was when everybody followed the rules. But somewhat suprisingly, the best results were achieved when most people followed the rules but a significant fraction did not! The rule breakers helped fill in gaps and actually caused traffic to flow more smoothly.
One of the reasons may be that the officers are specifically told not to take risks, and can even be punished if they do so anyway. If they fire even one bullet, or if they somehow provoke a violent situation that could have been avoided by simply letting the thief go about his business, they will be subject to an investigation. In today's lawsuit-happy society, if an officer gets killed or injured, the department may be sued. So the chiefs tell their officers to stay away from danger, and most officers are happy to comply. If you don't only risk your life but ALSO risk being suspended for taking a risk you shouldn't have taken, the decision becomes really easy.
We check the tires and look for leaks before every flight, but the wheel well is above eyesight level and pretty big. You have to actually climb up in there or open the landing gear doors to peek inside. That's normally not required. Everything that needs to be checked regularly, is visible from the ground.
Yes, but I was talking about the EXTRA encryption they used to apply to e-mail attachments. The full disk encryption is still present, that hasn't changed. I was just wondering why they bothered to apply an extra encryption step to e-mail attachments if by breaking full disk encryption you could get the passcode and break all the other encryption too without extra effort.
OK, so if I understood correctly, the entire "disk" (SSD) is encrypted with a key that can be unscrambled with the passphrase (just 4 digits for most people), and Apple used to also encrypt e-mail attachments one extra time on top of the full disk encryption, but now no longer does.
Can anyone explain what the added value was of the extra encryption they used to add and that is apparently so sorely missed now?
After all, what were they using to encrypt those attachments? Errr... the same passphrase, right? After all, I can boot up my iPhone, enter my passphrase, and read all my mail. No other extra strong authentication needed to get to e-mail attachments. If someone can get the password by brute-forcing the full disk encryption, they can then use that password to simply log in and open Mail.
Ergo, the extra encryption was totally useless and just a waste of battery power. Or am I missing something here?
Dragonflies certainly seem to be pretty good at judging the distance to nearby insects to attack them. And hoverflies as well, are really good at hovering in place and chasing other insects away. Actually, many insects eem to be able to judge distances quite well. Just landing on a flower or a turd wouldn't be easy without stereoscopic vision.
On the other hand, quite a lot of insects fly round in such a clumsy manner that you wonder whether they even have eyes at all. Crane flies, beetles, heteroptera,...
In the video, they said that the ionic liquid is like a bunch of little magnets sticking together but still able to move around each other. They stick together so well that the fluid wouldn't even evaporate in outer space. How can it be less cohesive than water, then? I know water molecules are little bipoles too, but water certainly does evaporate in outer space, so I would assume that the cohesive force is a lot less, no?
And the part about the lack of hydrostatic pressure... Do you mean the tubes have to be inserted deeper into the liquid? I don't think that matters at all, since the pressure in the tube as it passes through the surface will always be the same as the pressure above the surface. It doesn't matter how deep or wide the reservoirs are.
I do understand the conclusion: some siphons can work using the tensile strength of the fluid instead of (or in addition to) atmospheric pressure, but that doesn't mean you shouldn't at least mention the requirement.
Yes, it shows that you can siphon an extremely cohesive ionic liquid up to a very small height of just a few cm. The liquid would probably break up if you tried more than 10 cm or so, and you certainly wouldn't get anywhere near the 10 meters you can siphon ordinary water up to under atmospheric pressure.
The liquid is special because it is so cohesive that it can actually stay together under negative pressure. That is quite extraordinary, but certainly a very limited effect. Normal fluid breaks up as soon as you try to pull it apart, and so will even the ionic fluid if you tried only a little bit more height.
The ionic liquid they used for that experiment is a particularly cohesive liquid that even stays together under a small amount of tension (negative pressure). They only managed to get it up a few cm, though. Too bad they didn't try higher, I'm sure the fluid would break up at around 10 cm or so, probably even lower. Certainly nowhere near the 10 meters you can siphon water up to using atmospheric pressure.
It's really just like a drinking straw: when you suck, you reduce the pressure in your mouth (still a positive pressure, just less than normal) so that the atmospheric pressure pushes the liquid into the straw. In a siphon, gravity is providing the suction. But you can't suck (much) more than atmospheric pressure because the fluid breaks up when the pressure reaches zero. Except for very special liquids that can go slightly below zero, but not much.
The water breaks up because the pressure inside the tube reaches zero. Water doesn't stay together under negative pressure. Boiling has little to do with that.
You can siphon up a very small height, just a few cm, by using a particularly cohesive ionic fluid. The pressure in the liquid in the tube will actually become negative in that case, it's being pulled apart and only staying together because of the cohesion between the molecules. But that force could never hold more than a few cm, certainly not the 10 m that you can siphon water up to under atmospheric pressure.
The water in the experiment was still way above boiling point: at 0.18 atmosphere, water boils at a temperature of more than 50C. Of course the pressure up in the tube gets lower than 0.18 atm, but the whole point is indeed that the column breaks up when the pressure in the tube approaches zero. Not because the water boils, but simpy because it won't stay together. Unless you have a particularly cohesive fluid like some ionic fluids. You can use those to actually siphon up a few cm in a vacuum because they can stand a small amount of tension (negative pressure) without breaking up. But you'll get nowhere near the 10 meters you can get under atmospheric pressure.
And how high could you pull up the liquid? I bet it wasn't more than a few cm. At least it was in the experiment I saw on youtube. And, like you said, that was using an extremely cohesive ionic liquid.
I really wish someone would try that experiment with an apex more than 10 cm above the liquid surfaces. I'm pretty sure the fluid will break up.
Using atmospheric pressure, though, you can siphon ordinary water up to 10 m high.
Look at the replies to that post you referenced, explaining why it's wrong.
Granted, the video of that experiment does show that, if you have an extremely cohesive liquid (an ionic liquid, comparable to a bunch of magnets much stronger than water molecules), you can get it to siphon up a few cm using the cohesive force. But I bet they couldn't get it up to even 10 cm or so.
A normal siphon, under atmospheric pressure, can siphon water up to 10 m which also happens (coincidentally?) to be the height of water that corresponds to one atmosphere of pressure. In the Nature experiment referenced in the article, the water in the 1.5 m siphon broke up when they reduced the pressure to about 0.18 atm. How can you then say that atmospheric pressure has nothing to do with it?
I'll give you a car analogy:
Suppose we see a bunch of cars traveling up a 2000 meter mountain. I would say that their engines are pushing them up the hill. You would say that, no, their engines have nothing to do with it. You would then show an experiment where a car traveling at high speed would cut it engine and then coast up and down a small 20 meter high hill. See, cars don't need engines!
Yes, you can siphon up a very small height (just two centimeters or so) using an extraordinarily cohesive liquid. That doesn't imply that siphoning has nothing to do with atmospheric pressure.
And if you look at that link, you'll see it's a letter from 2010. Which is yesterday by Slashdot definitions, of course.
By the way, the letter was nicely debunked here:
http://www.theregister.co.uk/2...
Gravity is responsible for lowering the pressure in the outbound leg of the siphon, but you still need atmospheric pressure at the inlet to push the water over the top of the siphon. You can't siphon up more than about 10 m under normal atmospheric pressure.
So in a way, it's not really wrong to say that atmospheric pressure is pushing the water over the top. Just like atmospheric pressure pushes liquid into a drinking straw as well. Would you say that a drinking straw has nothing to do with atmospheric pressure?
Of course the exact value of atmospheric pressure doesn't matter much as long as it's enough, the flow rate will only depend on the difference in height between the two water levels, but without enough atomospheric pressure the siphon stops working. Which was clearly shown in the experiment described in Nature as well. In fact that experiment dispoves rather than proves his point.