The definitions of coordinates used in cosmology are far from arbitrary and have objectivity. There is specific meanings behind what distance and speeds mean, although a lot of that gets dropped from actual papers when summed up in more accessible material.
Well, with "arbitrary" I didn't mean to say there were no good reasons for using the cosmological model, quite the contrary. Obviously it's easier to use a reference frame in which the infinite universe is homogenous and the same age everywhere. I'm just saying that it's one of several possible choices of coordinate systems, and other choices would yield different times, distances and speeds. The whole idea of "space expanding faster than light" is in a way caused entirely by this particular choice of coordinates. The special-relativistic model (which pretty much nobody uses, for good reasons) does obey the speed limit but has the disadvantage of not being homogenous and treating our milky way as a special location at the center of a finite universe (like I described in my earlier, great-grandparent post).
I do prefer the cosmological model, but I think it's useful to point out exactly what it means, and where the contradiction with Special Relativity is coming from. Too many popular publications just say "space itself is expanding faster than light, and that explains it" while "space itself" doesn't really mean anything. They make it seem like space is some kind of expanding aether, which of course it isn't. Stuff in space happens to be flying apart, and we just chose a system of coordinates to make the description of the stuff easier. This happens to have the side-effect of creating the notion of an expanding "space" on top of which c has to be superimposed, but that's just a mathematical artefact caused by the choice of space-time coordinates.
You are right that you won't pass a beam of light in the same direction, because in GR it will always locally look like special relativity. But it is possible to have a beam of light shined directly at you, and have it never be able to reach you in finite time, while at the same time have its distance always increasing from the source.
Exactly, and I gave that example in my earlier great-grandparent post. In the cosmological model, the light from distant galaxies will never reach us because space is expanding too rapidly. In the special-relativistic model, that galaxy will never exist in our reference frame since its ancestral matter is moving away from us at a speed so close to c (and increasing towards it) that the passage of time is asymptotically grinding to a halt. Both views are consistent with the actual fact that we will never see that galaxy.
Everyone thinks that because one galaxy is moving away from me, relative to me, at.9 C in one direction and another is moving away from me at.9 C in the opposite direction (relative to me) then they are moving away from each other at faster than C. Not relative to each other though.
Well, if they are moving away from us at that speed due to the expansion of the universe, and everybody uses the cosmological model, then even the aliens in one of the galaxies will agree that the other galaxy is moving away from them at 1.8 c. Because that's due to "the expansion of space" (or in other words, the peculiarities of the cosmological model). If everybody uses models based on special relativity, the aliens will only measure the other galaxy at 0.99 c.
No two objects in space move away from each other, relative to each other, faster than C.
Just to make a tiny correction: relative to each other, as measured by one of them. If we measure them, using our reference frame, we will definitely see them moving away from each other at a relative speed of 1.2 c. Each second, the distance between them will have increased by 1.2 light seconds. But if you are on board of one of the objects, you will have a different clock and different distance scales. You will then measure 0.88 c.
Yes, light speed would be orders of magnitude greater than c with those silly definitions. Which is exactly the point: both light speed and the speed of local objects at different places in the universe can be different depending on which reference system you use, and this explains why things can go "faster than light" in some models, and light speed isn't always 'c'.
To make the comparison a bit more accurate: suppose I defined a non-cartesian reference system where the size of a metre depends on the distance to earth. Here on earth, it is the width of an atom but on Mars it's the length of our traditional metre. I can then go "faster" on earth than a ray of light on Mars since the ray on Mars is only doing 300000000 metres per second and I am doing more "metres" per second here. Of course that's still a silly example, but it's quite similar to what's happening in the cosmological model.
A reference frame that obeys special relativity will have the same light speed everywhere, and all objects will travel slower than c, but in the cosmological model light speed will have "the expansion of space" superimposed on it and objects travel away from us at speeds higher than c (but slower than local rays of light in the same direction). It's all just because of the coordinates used. Normally, objects moving away from us at high speed will be contracted in the direction of motion but the cosmological model uses contracted metres that make everything the same size again. And the scale keeps changing as the universe expands, artificially "moving" objects to ever greater distances. And clocks are artificially sped up. All of this throws Special Relativity out the window.
No matter which reference frame you use, you will never be able to outrace a beam of light at the same location as you. But you may be able to go "faster" than a beam of light that is many billions of light years away, since the "faster" just depends on arbitrary measurements without a direct objective relationship. In any case you can't actually physically pass a beam of light in the same direction as you.
Actually, they would have to compare some subset of the key over a classical channel, to detect eavesdropping and then use the remainder of the key for the actual secret communication.
Of course I disregarded gravity in my post. Black holes are a whole different ball game. But there too, you can use different coordinate systems to get different interpretations of the events, always yielding the same tangible results.
For example, you could easily argue that, at this moment, no black holes exist. Just before the black hole really becomes a black hole, local time will have slowed down so dramatically that it never actually becomes a black hole. It's forever stuck at the stage right before becoming a black hole. But change to a different reference system and there you go, they exist after all. Just change your definition of "now". In the second system, light inside the black hole may actually be retreating away from us even though it was aimed in our direction while in the first system, it is simply never emitted. I bet people have come up with reference frames that have time going backward inside black holes too. Or going imaginary (the complex number kind of imaginary). But no matter how you define your seconds and meters, you'll always get the same results if you apply General Relativity.
Space itself can expand at much greater velocities than c.
To explain this in a little more depth, what we call "space" is really just tied to an arbitrary choice of space-time coordinates. If we choose a different reference frame, distances and times will be different. Just to give a silly example, if I define a meter to be the width of an atom, or if I define a second to be the time required for the earth to go around the sun a thousand times, I can easily travel faster than c. So how does this apply to cosmology and general relativity?
Depending on the coordinate system you choose, the universe can really look radically different, even to the point of no longer being infinite. I will give two possible views, both equally valid even thought the first may appear strange. (So read the rest as well before labeling it as rubbish).
You can apply a classic "special(ly?) relativistic" coordinate system to the universe, with us at the center. The speed of light is the same everywhere, relative to us, just like Einstein said in the beginning. Things that are far away from us are moving away at high speed (but less than the speed of light) and are therefore aging more slowly. This means that some far away galaxy isn't just younger (defined as the amount of local evolution after the big bang) because we had to wait for its light to get to our telescope, it actually is younger "right now" even if we take the traveling time of light into account. Local clocks are really advancing more slowly. The effect increases with increasing distance, and at a distance of c times the age of the universe, the big bang is happening as we speak. Right now. This also means that the universe is finite (assuming nothing existed before the big bang, which is a big assumption). Not that it matters much, because we could never reach this "edge" anyway. It is retreating at the speed of light.
This model is quite interesting but a bit cumbersome for cosmology, so most people prefer to use the "cosmological model". They simply adjust the coordinates of time and space so that the whole universe is the same age and looks roughly the same everywhere, "right now". See, we just changed the definition of "now" and chose a coherently matching set of space coordinates so everything looks rougly the same size, that's all we did. In General Relativity, we are completely free to do so, you can pick pretty much any coordinate system you like. Things can move from the future into the past and back again as we change our variables, without impacting causality (which is all that matters).
Using the cosmological model, the universe is now truly infinite, the big bang is in the distant past everywhere and all the clocks are running at the same speed (as long as they are stationary relative to "space", i.e. moving away from us at the same speed as the average local galaxy). Now, however, the assumptions of special relativity no longer hold. In particular, the speed of light is no longer the same everywhere. Light speed is still the same everywhere locally, relative to "space" (the speed of the average galaxy in that area), but you have to take the properties of our peculiar coordinate system ("expanding space") into account. If at some distance, "space" and the objects in it are expanding away from us faster than the speed of light, the light from those galaxies will never reach us since it will actually be retreating as if it were running towards us on a conveyor belt moving the other way at a higher speed. The conveyor belt isn't "real", it's just an artifact of our choice of coordinates which does not comply with special relativity.
In the first model, those distant galaxies simply never come into existence since the local "space" is asymptotically stuck at a time shortly after the big bang. Things over there are moving away from us at increasing velocity approaching c, and time (rate of aging of that part of the universe) is grinding to a halt.
Entanglement can be used to exchange keys for secret communication. It allows two parties to create a shared key without anyone being able to intercept it. In principle, this key can be as long as the message itself and perfectly random, so a simple 'xor' operation is all it takes to make the message completely undecryptable. In more detail:
Alice wants to send a secret message to Bob. They (or anybody else, really) create a bunch of entangled photons, half going to Alice and the entangled counterparts going to Bob. This all happens at normal speeds (not faster than light), but can be prepared in advance. If anyone tries to eavesdrop during transmission of the entangled photons, Alice and Bob are able to detect the fact that the photons are no longer in a superimposed state and start over with a new bunch. Now Alice and Bob measure the photons. They have no control over the outcome of the measurements, which will be completely random, but they do know that they will both get the same result (or rather, exactly the opposite result). This becomes their cryptographic key. Now Alice encrypts her message with this key and sends it to Bob using traditional communication channels, for example a carrier pidgeon. Bob uses his identical key to decrypt the message.
The only faster-than-light part of the story is that the entangled photons "chose" their state at the time of the measurement. Before the measurement, they were in a superimposed state. This means the information for the key didn't even exist yet in any way and can therefore never be intercepted by anyone. It only came into existence at the time the photons were measured, simultaneously for Alice and Bob. (Take the word "simultaneously" with a grain of salt, because as the article shows, they can even be separated in time). And the encrypted message without the key is just a series of random bits.
So you can just wait until one day you're diagnosed with cancer, then go and get yourself insurance so the insurance company can pay for your treatment? I don't think insurance works that way.
Insurance is all about probabilities, they take money from a lot of people who have a low (normal) probability of getting sick and use that money to pay the few of them who do get sick. If clients are more likely to get sick, they'll have to pay a higher premium or the maths simply don't add up. And if you already know someone is sick and is going to need treatment, how can you give this person "insurance"? "O, you're going to need a couple of million dollars for your treatment? Sure, join up and pay a monthly fee of a few hundred dollars and we'll pay for your treatment." That just doesn't make sense.
Obviously I do know that insurance companies are making way too much money and could certainly do with a bit less, but you have to remain reasonable.
What I don't quite understand is how they first explain how difficult it is to find these planets, relying on tiny changes in the star's luminosity because the planets themselves are too dim to observe directly, and then go on to describe this planet in great detail: diameter, the fact that it's tidally locked, temperature at different locations, jet stream winds,... On a planet 2000 light years away? How did they get this "stong evidence"? Did they tune in to a local alien weather station?
Except for the fact that it's actually true. There are actual "professional" players, mainly retired or unemployed people, who sit in front of these machines all day and make a little bit of money in the long run. But way below minimum wage, so not really worth it. I'm not sure about the casino's strategy behind this, I guess it's to attract more non-perfect players who lose a lot more money than the "pros" are making. They basically use them for cheap advertising, I guess.
Which way would be "up" anyway? Away from the earth, but also away from the sun, away from the center of our milky way, away from the center of mass of our local cluster, etc... For "normal" down forces that doesn't matter, since the earth gets the same accellerations as we that are on it, so we only have to take the earth into account (except for tidal forces). But if all forces get inverted, all gravitational interactions from everywhere will suddenly make a difference.
And General Relativity would probably go out the window as well, because a straight line in curved spacetime should be the same for matter and antimatter.
Just look up DRM on Wikipedia, scroll down to "Obsolecence"
Amazon ebooks that could no longer be installed on new devices, Zune not being able to play PlaysForSure songs, MSN music songs after 2011, Yahoo! Music store licence servers shut down, etcetera. And there have been a few "always on" games that stopped working when the servers were shut down too, I seem to remember.
anyone who would set up a system to automatically trade based on an algorithm like that is a fucking idiot.
You can call them a lot of names, but "idiot" is not necessarily true. The algorithms would have made a shitload of money if the tweet had been true, while they probably only lost a relatively small amount now. The odds of a fake message would have to be pretty high for this strategy not to work in the long run. In fact, they probably lost a lot less than the amount they may have made with "bomb Boston marathon". And I wouldn't even be surprised if they actually managed to turn the fake tweet situation into a profit after all by reversing their positions in time while others were still selling like monkeys after seeing the wiggly line go down really fast.
Immoral, dishonest, call them what you will, but idiots? Unfortunately, no.
- First possibility: message is fake. HFT loses a bit of money by selling at prices just below current prices and then buying back at slightly higher prices when the tweet turns out to be fake. - Second possibility: message is real, markets tumble, HFT makes a shitload of money.
The probability of a fake message has to be pretty high for this strategy to be unprofitable in the long run. And then I'm not even mentioning the very real possibility of HFT algorithms managing to turn the first possibility into a profit after all by realising their mistake and reversing their positions while the other traders are still following their lead in selling,
That does not mean I condone automatic trading based on tweets, just that it's not necessarily as stupid a strategy as it would appear. Unfortunately.
Slashdot Mirror
The definitions of coordinates used in cosmology are far from arbitrary and have objectivity. There is specific meanings behind what distance and speeds mean, although a lot of that gets dropped from actual papers when summed up in more accessible material.
Well, with "arbitrary" I didn't mean to say there were no good reasons for using the cosmological model, quite the contrary. Obviously it's easier to use a reference frame in which the infinite universe is homogenous and the same age everywhere. I'm just saying that it's one of several possible choices of coordinate systems, and other choices would yield different times, distances and speeds. The whole idea of "space expanding faster than light" is in a way caused entirely by this particular choice of coordinates. The special-relativistic model (which pretty much nobody uses, for good reasons) does obey the speed limit but has the disadvantage of not being homogenous and treating our milky way as a special location at the center of a finite universe (like I described in my earlier, great-grandparent post).
I do prefer the cosmological model, but I think it's useful to point out exactly what it means, and where the contradiction with Special Relativity is coming from. Too many popular publications just say "space itself is expanding faster than light, and that explains it" while "space itself" doesn't really mean anything. They make it seem like space is some kind of expanding aether, which of course it isn't. Stuff in space happens to be flying apart, and we just chose a system of coordinates to make the description of the stuff easier. This happens to have the side-effect of creating the notion of an expanding "space" on top of which c has to be superimposed, but that's just a mathematical artefact caused by the choice of space-time coordinates.
You are right that you won't pass a beam of light in the same direction, because in GR it will always locally look like special relativity. But it is possible to have a beam of light shined directly at you, and have it never be able to reach you in finite time, while at the same time have its distance always increasing from the source.
Exactly, and I gave that example in my earlier great-grandparent post. In the cosmological model, the light from distant galaxies will never reach us because space is expanding too rapidly. In the special-relativistic model, that galaxy will never exist in our reference frame since its ancestral matter is moving away from us at a speed so close to c (and increasing towards it) that the passage of time is asymptotically grinding to a halt. Both views are consistent with the actual fact that we will never see that galaxy.
Everyone thinks that because one galaxy is moving away from me, relative to me, at .9 C in one direction and another is moving away from me at .9 C in the opposite direction (relative to me) then they are moving away from each other at faster than C. Not relative to each other though.
Well, if they are moving away from us at that speed due to the expansion of the universe, and everybody uses the cosmological model, then even the aliens in one of the galaxies will agree that the other galaxy is moving away from them at 1.8 c. Because that's due to "the expansion of space" (or in other words, the peculiarities of the cosmological model). If everybody uses models based on special relativity, the aliens will only measure the other galaxy at 0.99 c.
No two objects in space move away from each other, relative to each other, faster than C.
Just to make a tiny correction: relative to each other, as measured by one of them. If we measure them, using our reference frame, we will definitely see them moving away from each other at a relative speed of 1.2 c. Each second, the distance between them will have increased by 1.2 light seconds. But if you are on board of one of the objects, you will have a different clock and different distance scales. You will then measure 0.88 c.
Yes, light speed would be orders of magnitude greater than c with those silly definitions. Which is exactly the point: both light speed and the speed of local objects at different places in the universe can be different depending on which reference system you use, and this explains why things can go "faster than light" in some models, and light speed isn't always 'c'.
To make the comparison a bit more accurate: suppose I defined a non-cartesian reference system where the size of a metre depends on the distance to earth. Here on earth, it is the width of an atom but on Mars it's the length of our traditional metre. I can then go "faster" on earth than a ray of light on Mars since the ray on Mars is only doing 300000000 metres per second and I am doing more "metres" per second here. Of course that's still a silly example, but it's quite similar to what's happening in the cosmological model.
A reference frame that obeys special relativity will have the same light speed everywhere, and all objects will travel slower than c, but in the cosmological model light speed will have "the expansion of space" superimposed on it and objects travel away from us at speeds higher than c (but slower than local rays of light in the same direction). It's all just because of the coordinates used. Normally, objects moving away from us at high speed will be contracted in the direction of motion but the cosmological model uses contracted metres that make everything the same size again. And the scale keeps changing as the universe expands, artificially "moving" objects to ever greater distances. And clocks are artificially sped up. All of this throws Special Relativity out the window.
No matter which reference frame you use, you will never be able to outrace a beam of light at the same location as you. But you may be able to go "faster" than a beam of light that is many billions of light years away, since the "faster" just depends on arbitrary measurements without a direct objective relationship. In any case you can't actually physically pass a beam of light in the same direction as you.
Actually, they would have to compare some subset of the key over a classical channel, to detect eavesdropping and then use the remainder of the key for the actual secret communication.
Of course I disregarded gravity in my post. Black holes are a whole different ball game. But there too, you can use different coordinate systems to get different interpretations of the events, always yielding the same tangible results.
For example, you could easily argue that, at this moment, no black holes exist. Just before the black hole really becomes a black hole, local time will have slowed down so dramatically that it never actually becomes a black hole. It's forever stuck at the stage right before becoming a black hole. But change to a different reference system and there you go, they exist after all. Just change your definition of "now". In the second system, light inside the black hole may actually be retreating away from us even though it was aimed in our direction while in the first system, it is simply never emitted. I bet people have come up with reference frames that have time going backward inside black holes too. Or going imaginary (the complex number kind of imaginary). But no matter how you define your seconds and meters, you'll always get the same results if you apply General Relativity.
Space itself can expand at much greater velocities than c.
To explain this in a little more depth, what we call "space" is really just tied to an arbitrary choice of space-time coordinates. If we choose a different reference frame, distances and times will be different. Just to give a silly example, if I define a meter to be the width of an atom, or if I define a second to be the time required for the earth to go around the sun a thousand times, I can easily travel faster than c. So how does this apply to cosmology and general relativity?
Depending on the coordinate system you choose, the universe can really look radically different, even to the point of no longer being infinite. I will give two possible views, both equally valid even thought the first may appear strange. (So read the rest as well before labeling it as rubbish).
You can apply a classic "special(ly?) relativistic" coordinate system to the universe, with us at the center. The speed of light is the same everywhere, relative to us, just like Einstein said in the beginning. Things that are far away from us are moving away at high speed (but less than the speed of light) and are therefore aging more slowly. This means that some far away galaxy isn't just younger (defined as the amount of local evolution after the big bang) because we had to wait for its light to get to our telescope, it actually is younger "right now" even if we take the traveling time of light into account. Local clocks are really advancing more slowly. The effect increases with increasing distance, and at a distance of c times the age of the universe, the big bang is happening as we speak. Right now. This also means that the universe is finite (assuming nothing existed before the big bang, which is a big assumption). Not that it matters much, because we could never reach this "edge" anyway. It is retreating at the speed of light.
This model is quite interesting but a bit cumbersome for cosmology, so most people prefer to use the "cosmological model". They simply adjust the coordinates of time and space so that the whole universe is the same age and looks roughly the same everywhere, "right now". See, we just changed the definition of "now" and chose a coherently matching set of space coordinates so everything looks rougly the same size, that's all we did. In General Relativity, we are completely free to do so, you can pick pretty much any coordinate system you like. Things can move from the future into the past and back again as we change our variables, without impacting causality (which is all that matters).
Using the cosmological model, the universe is now truly infinite, the big bang is in the distant past everywhere and all the clocks are running at the same speed (as long as they are stationary relative to "space", i.e. moving away from us at the same speed as the average local galaxy). Now, however, the assumptions of special relativity no longer hold. In particular, the speed of light is no longer the same everywhere. Light speed is still the same everywhere locally, relative to "space" (the speed of the average galaxy in that area), but you have to take the properties of our peculiar coordinate system ("expanding space") into account. If at some distance, "space" and the objects in it are expanding away from us faster than the speed of light, the light from those galaxies will never reach us since it will actually be retreating as if it were running towards us on a conveyor belt moving the other way at a higher speed. The conveyor belt isn't "real", it's just an artifact of our choice of coordinates which does not comply with special relativity.
In the first model, those distant galaxies simply never come into existence since the local "space" is asymptotically stuck at a time shortly after the big bang. Things over there are moving away from us at increasing velocity approaching c, and time (rate of aging of that part of the universe) is grinding to a halt.
But do those places exist or not?
Entanglement can be used to exchange keys for secret communication. It allows two parties to create a shared key without anyone being able to intercept it. In principle, this key can be as long as the message itself and perfectly random, so a simple 'xor' operation is all it takes to make the message completely undecryptable. In more detail:
Alice wants to send a secret message to Bob.
They (or anybody else, really) create a bunch of entangled photons, half going to Alice and the entangled counterparts going to Bob. This all happens at normal speeds (not faster than light), but can be prepared in advance.
If anyone tries to eavesdrop during transmission of the entangled photons, Alice and Bob are able to detect the fact that the photons are no longer in a superimposed state and start over with a new bunch.
Now Alice and Bob measure the photons. They have no control over the outcome of the measurements, which will be completely random, but they do know that they will both get the same result (or rather, exactly the opposite result). This becomes their cryptographic key.
Now Alice encrypts her message with this key and sends it to Bob using traditional communication channels, for example a carrier pidgeon.
Bob uses his identical key to decrypt the message.
The only faster-than-light part of the story is that the entangled photons "chose" their state at the time of the measurement. Before the measurement, they were in a superimposed state. This means the information for the key didn't even exist yet in any way and can therefore never be intercepted by anyone. It only came into existence at the time the photons were measured, simultaneously for Alice and Bob. (Take the word "simultaneously" with a grain of salt, because as the article shows, they can even be separated in time). And the encrypted message without the key is just a series of random bits.
What if a competitor with very large pockets publishes free versions of your software just to force you out of business?
So you can just wait until one day you're diagnosed with cancer, then go and get yourself insurance so the insurance company can pay for your treatment? I don't think insurance works that way.
Insurance is all about probabilities, they take money from a lot of people who have a low (normal) probability of getting sick and use that money to pay the few of them who do get sick. If clients are more likely to get sick, they'll have to pay a higher premium or the maths simply don't add up. And if you already know someone is sick and is going to need treatment, how can you give this person "insurance"? "O, you're going to need a couple of million dollars for your treatment? Sure, join up and pay a monthly fee of a few hundred dollars and we'll pay for your treatment." That just doesn't make sense.
Obviously I do know that insurance companies are making way too much money and could certainly do with a bit less, but you have to remain reasonable.
You mean that spot where they just started construction of a new McDonalds?
Being paid for finding a vulnerability and keeping it secret sure beats getting sued for disclosing it responsibly.
More likely, these supercapacitors will be outlawed in the US because they "contain drugs".
And you can see storms from 2000 light years away?
What I don't quite understand is how they first explain how difficult it is to find these planets, relying on tiny changes in the star's luminosity because the planets themselves are too dim to observe directly, and then go on to describe this planet in great detail: diameter, the fact that it's tidally locked, temperature at different locations, jet stream winds,... On a planet 2000 light years away? How did they get this "stong evidence"? Did they tune in to a local alien weather station?
They turn into regular car wrecks.
Except for the fact that it's actually true. There are actual "professional" players, mainly retired or unemployed people, who sit in front of these machines all day and make a little bit of money in the long run. But way below minimum wage, so not really worth it. I'm not sure about the casino's strategy behind this, I guess it's to attract more non-perfect players who lose a lot more money than the "pros" are making. They basically use them for cheap advertising, I guess.
Which way would be "up" anyway? Away from the earth, but also away from the sun, away from the center of our milky way, away from the center of mass of our local cluster, etc... For "normal" down forces that doesn't matter, since the earth gets the same accellerations as we that are on it, so we only have to take the earth into account (except for tidal forces). But if all forces get inverted, all gravitational interactions from everywhere will suddenly make a difference.
And General Relativity would probably go out the window as well, because a straight line in curved spacetime should be the same for matter and antimatter.
Come on, even school kids can send balloons filled with helium up into space. Surely that can't be the problem?
Just look up DRM on Wikipedia, scroll down to "Obsolecence"
Amazon ebooks that could no longer be installed on new devices, Zune not being able to play PlaysForSure songs, MSN music songs after 2011, Yahoo! Music store licence servers shut down, etcetera. And there have been a few "always on" games that stopped working when the servers were shut down too, I seem to remember.
anyone who would set up a system to automatically trade based on an algorithm like that is a fucking idiot.
You can call them a lot of names, but "idiot" is not necessarily true. The algorithms would have made a shitload of money if the tweet had been true, while they probably only lost a relatively small amount now. The odds of a fake message would have to be pretty high for this strategy not to work in the long run. In fact, they probably lost a lot less than the amount they may have made with "bomb Boston marathon". And I wouldn't even be surprised if they actually managed to turn the fake tweet situation into a profit after all by reversing their positions in time while others were still selling like monkeys after seeing the wiggly line go down really fast.
Immoral, dishonest, call them what you will, but idiots? Unfortunately, no.
Well, to be fair:
- First possibility: message is fake. HFT loses a bit of money by selling at prices just below current prices and then buying back at slightly higher prices when the tweet turns out to be fake.
- Second possibility: message is real, markets tumble, HFT makes a shitload of money.
The probability of a fake message has to be pretty high for this strategy to be unprofitable in the long run. And then I'm not even mentioning the very real possibility of HFT algorithms managing to turn the first possibility into a profit after all by realising their mistake and reversing their positions while the other traders are still following their lead in selling,
That does not mean I condone automatic trading based on tweets, just that it's not necessarily as stupid a strategy as it would appear. Unfortunately.
Why not Ghandi? Didn't he have ancestors that might be related to yours?
That's entirely logical, it's common knowledge, with plenty of legal precedent, that having sex with someone is worse than killing them.
But then they'll need a new app for keeping your offspring from dating each other.