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I honestly don't get the "No, not again". Could you elaborate? Thanks edit: thanks for the explanation

cozzyd 8y ago
There are many ways to extend the standard model and it would be nice to have additional constraints on the extensions (which would come from observing behavior not described by the standard model).
- wolfgke 8y ago
  > There are many ways to extend the standard model and it would be nice to have additional constraints on the extensions (which would come from observing behavior not described by the standard model). For any experts reading this: what are plausible-looking extensions of the standard model which can probably be challenged/"proved" by current generation accelerators (in particular the LHC) and would lead to interesting extensions of the standard model? As far as I am aware, the LHC could e.g. find no sign of lots of variants of supersymmetry, which was a plausible candiate for this in the past: > https://www.scientificamerican.com/article/supersymmetry-fails-test-forcing-physics-seek-new-idea/ https://www.scientificamerican.com/article/supersymmetry-fai... > https://www.quantamagazine.org/complications-in-physics-lend-support-to-multiverse-hypothesis-20130524/ https://www.quantamagazine.org/complications-in-physics-lend...
  - cozzyd 8y ago
    I'm no theorist, so this is perhaps my jaded view, but right now my impression is that the phase space of theories is too large for someone to have a single prediction. The situation seems more like the LHC experiments are looking for ANY potential discrepancies with the standard model and then theorists will happily write up some reason for why it has to be that way. I went to a conference a few years ago where the LHC experiments announced that previous hints of a discrepancy with the SM evaporated with more statistics, which resulted in a whole session of theorists having to cancel / completely redo their talks.
    - the8472 8y ago
      > The situation seems more like the LHC experiments are looking for ANY potential discrepancies with the standard model and then theorists will happily write up some reason for why it has to be that way. Until recently they were mostly looking for specific deviations predicted by extensions. They only recently announced that they're now going for a broader search.
    - whatshisface 8y ago
      >theorists will happily write up some reason for why it has to be that way. They'll write down a model that describes it, which is all theorists' job to begin with.
izzydata 8y ago
I imagine they can't improve upon the standard model if everything they find never contradicts what they already know. Or rather what they can already conclude by the standard model.
- k__ 8y ago
  Are there so many parts that could be wrong?
  - proaralyst 8y ago
    Crucially: it really doesn't work with gravity or relativity.
    - jcranmer 8y ago
      The standard model incorporates special relativity, but you're right in that general relativity doesn't mesh with the standard model.
    - danbruc 8y ago
      To avoid confusion, relativity must be read as general relativity, the standard model is a relativistic quantum field theory and hence takes special relativity into account.
      - evanb 8y ago
        You can even formulate the standard model on a curved background metric that arises from GR. Just don't try to make the metric itself dynamical.
  - chriswarbo 8y ago
    As well as ignoring gravity, the standard model also doesn't predict or explain any of those observations labelled "dark matter" and "dark energy". We can add an extra parameter to general relativity (known as the "cosmological constant") to describe "dark energy" observations via a kind of 'anti gravity'; although we still don't fully understand what that means, or whether it's a correct description. It's also unclear whether this would have anything to do with quantum theories (like the standard model). General relativity can explain "dark matter" observations by assuming there is more mass/matter than we can see (i.e. it's electrically neutral and doesn't interact with light). Since the standard model tries to describe all of the fundamental constituents of matter, and forces including electromagnetism (light), having nothing to say about such a seemingly large amount of stuff is a rather large discrepancy in the standard model. AFAIK the standard model also says that neutrinos have zero mass; yet we've observed them undergoing radioactive decay ("neutrino oscillation", where each sort of neutrino can decay into the others). Particles which decay require some amount of time to do so. Particles with zero mass always travel at the speed of light (like photons, and hypothetical gravitons) and hence don't experience any time passing (this sentence is a consequence of special relativity). So particles with zero mass can't decay, so neutrinos can't have zero mass. I don't think we've measured their mass very accurately yet; we know it's very small, but it cannot be zero.
Will_Parker 8y ago
> I honestly don't get the "No, not again". Could you elaborate? As the cosmologist Sean Carroll said in his podcast, particle physicists haven't really been surprised by an observation since the 1970s. Presumably many were hoping for a surprise.
asdfman123 8y ago
If I have a conversation with you and you agree with everything I say, I learn nothing. If we have a conversation and you reveal that my assumptions are wrong, I can go back, rethink everything, and come out with a stronger world view. Basically, this experiment didn't tell scientists anything they didn't already know, or didn't prove them wrong--which might lead to newer, more interesting models that reveal more about the universe.

There are many ways to extend the standard model and it would be nice to have additional constraints on the extensions (which would come from observing behavior not described by the standard model).

wolfgke 8y ago
> There are many ways to extend the standard model and it would be nice to have additional constraints on the extensions (which would come from observing behavior not described by the standard model). For any experts reading this: what are plausible-looking extensions of the standard model which can probably be challenged/"proved" by current generation accelerators (in particular the LHC) and would lead to interesting extensions of the standard model? As far as I am aware, the LHC could e.g. find no sign of lots of variants of supersymmetry, which was a plausible candiate for this in the past: > https://www.scientificamerican.com/article/supersymmetry-fails-test-forcing-physics-seek-new-idea/ https://www.scientificamerican.com/article/supersymmetry-fai... > https://www.quantamagazine.org/complications-in-physics-lend-support-to-multiverse-hypothesis-20130524/ https://www.quantamagazine.org/complications-in-physics-lend...
- cozzyd 8y ago
  I'm no theorist, so this is perhaps my jaded view, but right now my impression is that the phase space of theories is too large for someone to have a single prediction. The situation seems more like the LHC experiments are looking for ANY potential discrepancies with the standard model and then theorists will happily write up some reason for why it has to be that way. I went to a conference a few years ago where the LHC experiments announced that previous hints of a discrepancy with the SM evaporated with more statistics, which resulted in a whole session of theorists having to cancel / completely redo their talks.
  - the8472 8y ago
    > The situation seems more like the LHC experiments are looking for ANY potential discrepancies with the standard model and then theorists will happily write up some reason for why it has to be that way. Until recently they were mostly looking for specific deviations predicted by extensions. They only recently announced that they're now going for a broader search.
  - whatshisface 8y ago
    >theorists will happily write up some reason for why it has to be that way. They'll write down a model that describes it, which is all theorists' job to begin with.

izzydata 8y ago

I imagine they can't improve upon the standard model if everything they find never contradicts what they already know. Or rather what they can already conclude by the standard model.

k__ 8y ago
Are there so many parts that could be wrong?
- proaralyst 8y ago
  Crucially: it really doesn't work with gravity or relativity.
  - jcranmer 8y ago
    The standard model incorporates special relativity, but you're right in that general relativity doesn't mesh with the standard model.
  - danbruc 8y ago
    To avoid confusion, relativity must be read as general relativity, the standard model is a relativistic quantum field theory and hence takes special relativity into account.
    - evanb 8y ago
      You can even formulate the standard model on a curved background metric that arises from GR. Just don't try to make the metric itself dynamical.
- chriswarbo 8y ago
  As well as ignoring gravity, the standard model also doesn't predict or explain any of those observations labelled "dark matter" and "dark energy". We can add an extra parameter to general relativity (known as the "cosmological constant") to describe "dark energy" observations via a kind of 'anti gravity'; although we still don't fully understand what that means, or whether it's a correct description. It's also unclear whether this would have anything to do with quantum theories (like the standard model). General relativity can explain "dark matter" observations by assuming there is more mass/matter than we can see (i.e. it's electrically neutral and doesn't interact with light). Since the standard model tries to describe all of the fundamental constituents of matter, and forces including electromagnetism (light), having nothing to say about such a seemingly large amount of stuff is a rather large discrepancy in the standard model. AFAIK the standard model also says that neutrinos have zero mass; yet we've observed them undergoing radioactive decay ("neutrino oscillation", where each sort of neutrino can decay into the others). Particles which decay require some amount of time to do so. Particles with zero mass always travel at the speed of light (like photons, and hypothetical gravitons) and hence don't experience any time passing (this sentence is a consequence of special relativity). So particles with zero mass can't decay, so neutrinos can't have zero mass. I don't think we've measured their mass very accurately yet; we know it's very small, but it cannot be zero.

Will_Parker 8y ago

> I honestly don't get the "No, not again". Could you elaborate? As the cosmologist Sean Carroll said in his podcast, particle physicists haven't really been surprised by an observation since the 1970s. Presumably many were hoping for a surprise.

asdfman123 8y ago

If I have a conversation with you and you agree with everything I say, I learn nothing. If we have a conversation and you reveal that my assumptions are wrong, I can go back, rethink everything, and come out with a stronger world view. Basically, this experiment didn't tell scientists anything they didn't already know, or didn't prove them wrong--which might lead to newer, more interesting models that reveal more about the universe.