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I don't think the problem is string theory per se — I think the problem is that we're running up on the bounds of what we can test experimentally, and further p

I don't think the problem is string theory per se — I think the problem is that we're running up on the bounds of what we can test experimentally, and further progress is going to require some really cleverly designed experiments that can probe Planck scale events. Although the greatest physicists throughout history have for the most part been theoreticians, it may be the case that in the future, the greatest physicists will be experimentalists because of the extraordinary amount of creativity needed to design novel experiments that can probe the most obscure corners of reality. String theory isn't pseudoscience, because it does make testable, falsifiable predictions. In fact, it makes the same predictions that quantum field theory does for the phenomena that we are currently capable of testing (and arguably using a more elegant framework than QFT provides). The problem is that the predictions that string theory makes beyond QFT are currently way outside the realm of experimental assessment. This doesn't make the predictions false — if that's the way the universe really is, we just may be incapable of knowing that for a long time. There are a few hints that at least some of the predictions of string theory may be incorrect — we have yet to find any evidence of supersymmetry, and many physicists thought the LHC would turn up at least some evidence of this if it existed. Regardless, I think people get too hung up on buzz-phrases like "is time real?" or "are we in a multiverse?". A lot of these are what I consider irrelevant to science, as the goal of science is to make accurate predictions about the future. If there is another universe out there, it is by definition unreachable from our current universe, so it makes no difference to science whatsoever. Likewise, what is or isn't "real" has no bearing on how accurately one can compute the evolution of some system's state through time.

nol13 10y ago
But how can you make accurate predictions about the future if time isn't real? Chew on that science boy.
- wolfgke 10y ago
  Even if time emerges from something different it is still there.
  - nol13 10y ago
    Prove it.
chime 10y ago
> Regardless, I think people get too hung up on buzz-phrases like "is time real?" or "are we in a multiverse?". If by people you mean science vbloggers like VSauce or Veritasium or even NDT's new Cosmos, then I'd say their goals are not to do or teach science but to inspire the next generation. Pop-sci is not for today's scientists. It is for the next generation of scientists and I think these philosophical questions are a fantastic way to get people interested in pursuing a career that doesn't have much glamor but can be very promising and fulfilling.
kilroy123 10y ago
Are there people/groups actively working on a way to test string theory? If so, are they getting close?
gnaritas 10y ago
> If there is another universe out there, it is by definition unreachable from our current universe We can't know that yet, universes if parallel may interact at small scales in such a way that they can't be detected and reachable. To say they're unreachable by definition is hubris.
- codeulike 10y ago
  I think he means that universe = universal = everything so that if parallel universe-things did turn out to be observable then we would have to expand our concept of universe to include them, rather than call them separate universes.
  - gnaritas 10y ago
    That's not what the thing I quoted meant, nor what I was replying to.
    - codeulike 10y ago
      I disagree.
      - gnaritas 10y ago
        Well then feel free to expand because frankly the sentence I quoted cannot possibly in any way be interpreted to mean what you said; you're having a reading comprehension issue if you think your interpretation in any way matches what I quoted. What you said is an entirely different thing than what he said, they aren't even close.
        codeulike 10y ago
        Xcelerate said 'by definition', and emphasised it. Which means that his/her argument rests on the definition of the term 'universe'. edit: Also Xcelerate has confirmed thats what they meant: https://news.ycombinator.com/item?id=12083025 https://news.ycombinator.com/item?id=12083025
nilkn 10y ago
> String theory isn't pseudoscience, because it does make testable, falsifiable predictions. I feel like it's also worth pointing out that string theory is also a possible solution to an extremely difficult mathematical problem. You don't fully get an appreciation for this when reading popular accounts. You don't realize that string theory is not just mumbo-jumbo about strings that someone made up but rather that the extraordinarily sophisticated math behind it actually works out, something that can't be said for the vast, vast majority of attempts at resolving the issues that string theory does resolve. The difficulty of this problem is such that even coming up with possible solutions is itself a Herculean feat (witness the fact that Edward Witten, who proposed M theory, was awarded a Fields medal). This is ultimately why string theory has ever been taken seriously. None of this means string theory is correct, of course.
- naasking 10y ago
  > resolving the issues that string theory does resolve. Is there a list of such issues somewhere?
Koshkin 10y ago
"is time real?" -- I am somewhat puzzled by this question being so popular. (Perhaps, people are mystified by what appears to be a perpetual and unstoppable progression of things from the past to the future which is not under our control.) Of course time is real, just like, for example, distance (length) is real. You can measure time, just like you can measure distance - in some units that you can choose. So, if one has doubts as to reality of time, there is no reason why one should not also doubt reality of space with all its attributes, i.e. pretty much reality of anything at all.
- guitarbill 10y ago
  Time is weird though. With e.g. mass, you can define the kilogram as the mass of a certain number of atoms, which makes sense. Time though is defined as some amount of caesium oscillations. Also, time (and therefore length, or vice versa if you prefer) changes in relativistic scenarios, only the speed of light is constant. Even as a physicist, I've often thought that time is more of a useful mental construct, but maybe it's time for something else. And then there's the question of why time doesn't flow backwards (aka the arrow of time), which is genuinely interesting. Only a few fields have answers for this, e.g. thermodynamics with entropy. I hope answering this question will give us a much better framework to define time. I'd love it if it was shown in my lifetime that time is quantised.
  - cLeEOGPw 10y ago
    You just said yourself that only speed of light is constant, mass is also relativistic like time. And how do you know that time doesn't flow backwards? On quantum scale, how do you tell past from future? Gravity is one directional too, but somehow everyone are mystified by time. I think it's because it's far too easy to let the imagination run wild on the possibilities of reversing time, but much less intuitive to imagine "reverse: gravitation or reverse entropy.
    - guitarbill 10y ago
      > And how do you know that time doesn't flow backwards? On quantum scale, how do you tell past from future? E.g. you don't observe a glass un-smashing. But as you probably also know, the question if/how a quantum arrow of time relates thermodynamics is currently unsolved and probably Nobel Prize territory. Not sure how much progress we'll make on Hacker News. > Gravity is one directional too I assume you mean it's purely attractive? It isn't too difficult to imagine a sphere with negative mass repelling another (like magnets), even if you've never seen negative mass :) How do you picture reversing time? If you imagine it like reversing a video, it's obvious how this breaks down, again from the glass un-smashing. Entropy can be very visceral.

nol13 10y ago

But how can you make accurate predictions about the future if time isn't real? Chew on that science boy.

wolfgke 10y ago
Even if time emerges from something different it is still there.
- nol13 10y ago
  Prove it.

chime 10y ago

> Regardless, I think people get too hung up on buzz-phrases like "is time real?" or "are we in a multiverse?". If by people you mean science vbloggers like VSauce or Veritasium or even NDT's new Cosmos, then I'd say their goals are not to do or teach science but to inspire the next generation. Pop-sci is not for today's scientists. It is for the next generation of scientists and I think these philosophical questions are a fantastic way to get people interested in pursuing a career that doesn't have much glamor but can be very promising and fulfilling.

kilroy123 10y ago

Are there people/groups actively working on a way to test string theory? If so, are they getting close?

gnaritas 10y ago

> If there is another universe out there, it is by definition unreachable from our current universe We can't know that yet, universes if parallel may interact at small scales in such a way that they can't be detected and reachable. To say they're unreachable by definition is hubris.

codeulike 10y ago
I think he means that universe = universal = everything so that if parallel universe-things did turn out to be observable then we would have to expand our concept of universe to include them, rather than call them separate universes.
- gnaritas 10y ago
  That's not what the thing I quoted meant, nor what I was replying to.
  - codeulike 10y ago
    I disagree.
    - gnaritas 10y ago
      Well then feel free to expand because frankly the sentence I quoted cannot possibly in any way be interpreted to mean what you said; you're having a reading comprehension issue if you think your interpretation in any way matches what I quoted. What you said is an entirely different thing than what he said, they aren't even close.
      - codeulike 10y ago
        Xcelerate said 'by definition', and emphasised it. Which means that his/her argument rests on the definition of the term 'universe'. edit: Also Xcelerate has confirmed thats what they meant: https://news.ycombinator.com/item?id=12083025 https://news.ycombinator.com/item?id=12083025

nilkn 10y ago

> String theory isn't pseudoscience, because it does make testable, falsifiable predictions. I feel like it's also worth pointing out that string theory is also a possible solution to an extremely difficult mathematical problem. You don't fully get an appreciation for this when reading popular accounts. You don't realize that string theory is not just mumbo-jumbo about strings that someone made up but rather that the extraordinarily sophisticated math behind it actually works out, something that can't be said for the vast, vast majority of attempts at resolving the issues that string theory does resolve. The difficulty of this problem is such that even coming up with possible solutions is itself a Herculean feat (witness the fact that Edward Witten, who proposed M theory, was awarded a Fields medal). This is ultimately why string theory has ever been taken seriously. None of this means string theory is correct, of course.

naasking 10y ago
> resolving the issues that string theory does resolve. Is there a list of such issues somewhere?

Koshkin 10y ago

"is time real?" -- I am somewhat puzzled by this question being so popular. (Perhaps, people are mystified by what appears to be a perpetual and unstoppable progression of things from the past to the future which is not under our control.) Of course time is real, just like, for example, distance (length) is real. You can measure time, just like you can measure distance - in some units that you can choose. So, if one has doubts as to reality of time, there is no reason why one should not also doubt reality of space with all its attributes, i.e. pretty much reality of anything at all.

guitarbill 10y ago
Time is weird though. With e.g. mass, you can define the kilogram as the mass of a certain number of atoms, which makes sense. Time though is defined as some amount of caesium oscillations. Also, time (and therefore length, or vice versa if you prefer) changes in relativistic scenarios, only the speed of light is constant. Even as a physicist, I've often thought that time is more of a useful mental construct, but maybe it's time for something else. And then there's the question of why time doesn't flow backwards (aka the arrow of time), which is genuinely interesting. Only a few fields have answers for this, e.g. thermodynamics with entropy. I hope answering this question will give us a much better framework to define time. I'd love it if it was shown in my lifetime that time is quantised.
- cLeEOGPw 10y ago
  You just said yourself that only speed of light is constant, mass is also relativistic like time. And how do you know that time doesn't flow backwards? On quantum scale, how do you tell past from future? Gravity is one directional too, but somehow everyone are mystified by time. I think it's because it's far too easy to let the imagination run wild on the possibilities of reversing time, but much less intuitive to imagine "reverse: gravitation or reverse entropy.
  - guitarbill 10y ago
    > And how do you know that time doesn't flow backwards? On quantum scale, how do you tell past from future? E.g. you don't observe a glass un-smashing. But as you probably also know, the question if/how a quantum arrow of time relates thermodynamics is currently unsolved and probably Nobel Prize territory. Not sure how much progress we'll make on Hacker News. > Gravity is one directional too I assume you mean it's purely attractive? It isn't too difficult to imagine a sphere with negative mass repelling another (like magnets), even if you've never seen negative mass :) How do you picture reversing time? If you imagine it like reversing a video, it's obvious how this breaks down, again from the glass un-smashing. Entropy can be very visceral.