Yep. And most string theorists would cheer. They work on string theory because it's the best theory we have that unifies QM and GR. They'd love to find a better one.
It is true that once you measure that photon, you only extract the one bit of information, but if you were to send this photon into a quantum computer, you could do all sorts of analysis on it first. So in some sense the information is there, it's just not extractable.
Also, see the 1966 short story by Bob Shaw that anticipated this: Slow Light
Some of these are valid complaints, some are not. Responses from a one-time string theorist:
1. Yes. It's a shame. The usual response is "Well how's _your_ quantum gravity theory coming," which tends to shut people up. But there are other interesting responses. See Lenny Susskind's recent book.
2. That's the wrong way of looking at it. While we thought the cosmological constant was zero, no one really looked to see if you could get nonzero ones in string theory, since you could clearly do zero. Once we saw that it wasn't zero in nature, people started looking in string theory, and realized that you could do it pretty easily, and in fact, it is probably more general for the cosmological constant to me nonzero in string theory.
3. It's not that string theory is invalid in time-dependent spacetimes, it's just that we don't yet understand how to calculate much there. We have some ideas. It is true that most of our understanding of string theory is background-dependent--that is you have to specify a spacetime background before calculating anything.
4. This is true. This is a very difficult problem, and is really a job for the mathematicians. Even quantum field theory, a very well regarded theory, has some mathematical problems. Because we can't prove things, what we do is calculate them in different ways. So far, almost all of these calculations don't disagree with each other (there is a little debate about one or two).
5. I wouldn't characterize these arguments as strong. And string theory does not really assume that spacetime is continuous, though it's a little hard to explain why. Briefly, spacetime is an emergent phenomenon of the theory, and words like "continuous" or "discrete" don't necessarily apply. It is certainly true that string theory is blind to variations in spacetime on very small scales, which is very similar to a theory with a discrete spacetime.
Two final comments: The article, and many people, blame string theorists for this problem, which may be fair. But the real reason for it is that physicists have no interesting, fundamental experimental puzzles, and haven't for more than twenty years. So they don't have anything better to do than try to work out this fascinating theory. This may be changing a little, as interesting cosmological data emerges, and may change dramatically with the LHC.
Also, complaints about testability were levied not too many years ago against another theory: cosmological inflation. Now we have new ideas of how to test it, and we're doing so. So far, it's passing with flying colors.
But it's a valid thing for people to talk about these issues, and I think most string theorists welcome the discussion.
In case anyone is curious, the problems from the IMO this year. Four and half hours for each set of three:
Day 1
Problem 1 ABC is acute angle triangle with AB not equal to AC. The circle with diameter BC intersects the lines AB and AC respectively at M and N. O is the midpoint of BC. The bisectors of angle BAC and angle MON intersect at R. Prove that the circumcircles of thev triangles BMR and CNR have a common point lying on the line BC.
Problem 2 Find all polynomials f with real coefficients such that, for all reals a,b,c such that ab+bc+ca = 0, we have the relation
f(a-b) + f(b-c) + f(c-a) = 2 f(a+b+c)
Problem 3 Define a "hook" to be a figure made up of six unit squares as shown by the &s in the figure below, or any of the figures obtained by rotations and reflections to this figure. &&& &@& &@@ (@s are just place holders) Determine all mxn rectangles that can be covered without gaps and without overlaps with hooks such that no point of a hook covers area outside the rectangle.
Day 2
Problem 4 Let n>=3 be an integer. Let t[1],...,t[n] be positive real numbers such that n^2+1 is greater than (t[1]+...+t[n])(1/t[1]+...+1/t[n]) Show that, for all distinct i,j,k, t[i],t[j],t[k] are the side lengths of a triangle.
Problem 5 In a convex quadrilateral ABCD, the diagonal BD bisects neither angle ABC nor angle CDA. A point P lies inside ABCD and satisfies angle PBC = angle DBA and angle PDC = angle BDA. Prove that ABCD are concyclic if and only if AP = CP.
Problem 6 A positive integer is alternating if every two consecutive digits in its decimal representation are of different parity. Find all positive integers n such that n has a multiple which is alternating.
Slashdot Mirror
Yeah, except that that's incorrect: http://www.lawfficespace.com/2013/12/yes-white-males-are-protected-class.html.
Yep. And most string theorists would cheer. They work on string theory because it's the best theory we have that unifies QM and GR. They'd love to find a better one.
It is true that once you measure that photon, you only extract the one bit of information, but if you were to send this photon into a quantum computer, you could do all sorts of analysis on it first. So in some sense the information is there, it's just not extractable.
Also, see the 1966 short story by Bob Shaw that anticipated this:
Slow Light
Some of these are valid complaints, some are not. Responses from a one-time string theorist:
1. Yes. It's a shame. The usual response is "Well how's _your_ quantum gravity theory coming," which tends to shut people up. But there are other interesting responses. See Lenny Susskind's recent book.
2. That's the wrong way of looking at it. While we thought the cosmological constant was zero, no one really looked to see if you could get nonzero ones in string theory, since you could clearly do zero. Once we saw that it wasn't zero in nature, people started looking in string theory, and realized that you could do it pretty easily, and in fact, it is probably more general for the cosmological constant to me nonzero in string theory.
3. It's not that string theory is invalid in time-dependent spacetimes, it's just that we don't yet understand how to calculate much there. We have some ideas. It is true that most of our understanding of string theory is background-dependent--that is you have to specify a spacetime background before calculating anything.
4. This is true. This is a very difficult problem, and is really a job for the mathematicians. Even quantum field theory, a very well regarded theory, has some mathematical problems. Because we can't prove things, what we do is calculate them in different ways. So far, almost all of these calculations don't disagree with each other (there is a little debate about one or two).
5. I wouldn't characterize these arguments as strong. And string theory does not really assume that spacetime is continuous, though it's a little hard to explain why. Briefly, spacetime is an emergent phenomenon of the theory, and words like "continuous" or "discrete" don't necessarily apply. It is certainly true that string theory is blind to variations in spacetime on very small scales, which is very similar to a theory with a discrete spacetime.
Two final comments: The article, and many people, blame string theorists for this problem, which may be fair. But the real reason for it is that physicists have no interesting, fundamental experimental puzzles, and haven't for more than twenty years. So they don't have anything better to do than try to work out this fascinating theory. This may be changing a little, as interesting cosmological data emerges, and may change dramatically with the LHC.
Also, complaints about testability were levied not too many years ago against another theory: cosmological inflation. Now we have new ideas of how to test it, and we're doing so. So far, it's passing with flying colors.
But it's a valid thing for people to talk about these issues, and I think most string theorists welcome the discussion.
In case anyone is curious, the problems from the IMO this year. Four and half hours for each set of three:
Day 1
Problem 1
ABC is acute angle triangle with AB not equal to AC. The circle with diameter BC intersects the lines AB and AC respectively at M and N. O is the midpoint of BC. The bisectors of angle BAC and angle MON intersect at R. Prove that the circumcircles of thev triangles BMR and CNR have a common point lying on the line BC.
Problem 2
Find all polynomials f with real coefficients such that, for all reals a,b,c such that ab+bc+ca = 0, we have the relation
f(a-b) + f(b-c) + f(c-a) = 2 f(a+b+c)
Problem 3
Define a "hook" to be a figure made up of six unit squares as shown by the &s in the figure below, or any of the figures obtained by rotations and reflections to this figure.
&&&
&@&
&@@
(@s are just place holders)
Determine all mxn rectangles that can be covered without gaps and without overlaps with hooks such that no point of a hook covers area outside the rectangle.
Day 2
Problem 4
Let n>=3 be an integer. Let t[1],...,t[n] be positive real numbers such that n^2+1 is greater than (t[1]+...+t[n])(1/t[1]+...+1/t[n]) Show that, for all distinct i,j,k, t[i],t[j],t[k] are the side lengths of a triangle.
Problem 5
In a convex quadrilateral ABCD, the diagonal BD bisects neither angle ABC nor angle CDA. A point P lies inside ABCD and satisfies angle PBC = angle DBA and angle PDC = angle BDA. Prove that ABCD are concyclic if and only if AP = CP.
Problem 6
A positive integer is alternating if every two consecutive digits in its decimal representation are of different parity. Find all positive integers n such that n has a multiple which is alternating.
(From Ignacio Larrosa Cañestro on sci.math)