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...subject to our assumed framework and chosen prior. People always forget that Bayes theorem only marginalizes over the unknown parameters. It assumes the mode

...subject to our assumed framework and chosen prior. People always forget that Bayes theorem only marginalizes over the unknown parameters. It assumes the model is otherwise given (true). You can only marginalize over the known-unknowns, not the unknown-unknowns. People like to slip assumptions into their models where the uncertainties are not accounted for. The reason why everyone trusts the LIGO result is that we have an extremely high degree of confidence in general relativity. More generally, what's even the point of placing a confidence level on a non-falsifiable claim? What utility does it serve?

aalleavitch 9y ago
We might be able to generate hypotheses using it as a premise?
quietbritishjim 9y ago
For context: This reply was written when the title on here was "With 95% confidence, we expect our Universe to last more than 10^58 years"
phkahler 9y ago
>> More generally, what's even the point of placing a confidence level on a non-falsifiable claim? One can answer questions like: Is it worthwhile for people to attempt to colonize the galaxy? When things like getting to other stars will take lifetimes, and getting across a galaxy 100M light-years across may take more time than has already passed, one needs to have some idea if there is even enough time left for such undertakings. Of course the lifetime of the galaxy will probably be less than 10^50 years, at least it puts the universe as a whole into better context. And really, in spite of any crazy ideas just putting ourselves into context seems to be important to a lot of people.
deleted 9y ago
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lisper 9y ago
> The reason why everyone trusts the LIGO result is that we have an extremely high degree of confidence in general relativity. No, that's not true. The reason everyone "trusts" the LIGO results is because we believe the people running the experiment are trustworthy. The results have nothing to do with GR except insofar as they were designed to test a heretofore untested prediction of GR (which prediction they have confirmed). And the reason we want to test a prediction of GR is that we want to try to falsify it, because that is the way progress is made in science. I think you may have meant to say something about how we cannot know for certain that GR is true, that that's right, we can't. But it's not like Einstein just pulled GR out of a hat. It's the only known solution to the problem that fits all of the known data. That doesn't prove it's true, but it is the best explanation we have so we might as well carry on as if it's true until someone proves otherwise or comes up with a better idea.
- AnimalMuppet 9y ago
  I don't think that LIGO was designed (only) to test GR. It was also set up to be an astronomical observatory. (I don't know which goal was considered more important...)
  - lisper 9y ago
    Why do you think those are different goals?
    - AnimalMuppet 9y ago
      Because in the astronomy part, we're assuming the GR is correct, and using it to watch astronomical events in a way we couldn't before. For example, the detected neutron star merger tested that gravitational waves travel at the speed of light, since we were able to also detect the fast gamma ray burst from it. That's testing GR. But it also showed that such fast gamma ray bursts come from the merger of two neutron stars. That's not testing GR.
- perlgeek 9y ago
  My impression was that they made advanced predictions what a gravitational wave observation would look like from a binary black hole merger, and then they measured pretty much exactly that. This is why we believe the machine worked. The other reason we believe them is that they (together with VIRGO) found a neutron star merger, and that was confirmed by many other observations in many different spectra.
deleted 9y ago
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falkod 9y ago
>> ...subject to our assumed framework and chosen prior. This is usually implicit in such analyses. >> More generally, what's even the point of placing a confidence level on a non-falsifiable claim? What utility does it serve? It's not about falsifiability in the sense that someone should go out and measure the predicted lifetime of the universe experimentally. The point of such lifetime calculations (and their associated confidence levels) is more as a test of the underlying theory - the Standard Model of particle physics. If this theory would make the prediction that the lifetime of the universe should be shorter than the observed lifetime of the universe, then clearly there is something wrong with the theory, or with the way the lifetime has been computed, since clearly we are still here to make that calcuation. Usually, this is seen as a sign that there should be some new physics - i.e. physics that is not described by the standard model in its present form - that should enter at an energy scale relevant to the calculation. Since this we do not know about this physics yet, the calculation is necessarily incomplete, which would explain finding a "too short" lifetime of the universe, while with a more complete theory one would (hopefully) find a result, that explains observed lifetime of the universe. The fact that the paper finds a "long enough" lifetime of the universe, could be seen as an indication that the theory is able to make predictions at energy scales relevant to this calculation.

aalleavitch 9y ago

We might be able to generate hypotheses using it as a premise?

quietbritishjim 9y ago

For context: This reply was written when the title on here was "With 95% confidence, we expect our Universe to last more than 10^58 years"

phkahler 9y ago

>> More generally, what's even the point of placing a confidence level on a non-falsifiable claim? One can answer questions like: Is it worthwhile for people to attempt to colonize the galaxy? When things like getting to other stars will take lifetimes, and getting across a galaxy 100M light-years across may take more time than has already passed, one needs to have some idea if there is even enough time left for such undertakings. Of course the lifetime of the galaxy will probably be less than 10^50 years, at least it puts the universe as a whole into better context. And really, in spite of any crazy ideas just putting ourselves into context seems to be important to a lot of people.

deleted 9y ago

[deleted]

lisper 9y ago

> The reason why everyone trusts the LIGO result is that we have an extremely high degree of confidence in general relativity. No, that's not true. The reason everyone "trusts" the LIGO results is because we believe the people running the experiment are trustworthy. The results have nothing to do with GR except insofar as they were designed to test a heretofore untested prediction of GR (which prediction they have confirmed). And the reason we want to test a prediction of GR is that we want to try to falsify it, because that is the way progress is made in science. I think you may have meant to say something about how we cannot know for certain that GR is true, that that's right, we can't. But it's not like Einstein just pulled GR out of a hat. It's the only known solution to the problem that fits all of the known data. That doesn't prove it's true, but it is the best explanation we have so we might as well carry on as if it's true until someone proves otherwise or comes up with a better idea.

AnimalMuppet 9y ago
I don't think that LIGO was designed (only) to test GR. It was also set up to be an astronomical observatory. (I don't know which goal was considered more important...)
- lisper 9y ago
  Why do you think those are different goals?
  - AnimalMuppet 9y ago
    Because in the astronomy part, we're assuming the GR is correct, and using it to watch astronomical events in a way we couldn't before. For example, the detected neutron star merger tested that gravitational waves travel at the speed of light, since we were able to also detect the fast gamma ray burst from it. That's testing GR. But it also showed that such fast gamma ray bursts come from the merger of two neutron stars. That's not testing GR.
perlgeek 9y ago
My impression was that they made advanced predictions what a gravitational wave observation would look like from a binary black hole merger, and then they measured pretty much exactly that. This is why we believe the machine worked. The other reason we believe them is that they (together with VIRGO) found a neutron star merger, and that was confirmed by many other observations in many different spectra.

deleted 9y ago

[deleted]

falkod 9y ago

>> ...subject to our assumed framework and chosen prior. This is usually implicit in such analyses. >> More generally, what's even the point of placing a confidence level on a non-falsifiable claim? What utility does it serve? It's not about falsifiability in the sense that someone should go out and measure the predicted lifetime of the universe experimentally. The point of such lifetime calculations (and their associated confidence levels) is more as a test of the underlying theory - the Standard Model of particle physics. If this theory would make the prediction that the lifetime of the universe should be shorter than the observed lifetime of the universe, then clearly there is something wrong with the theory, or with the way the lifetime has been computed, since clearly we are still here to make that calcuation. Usually, this is seen as a sign that there should be some new physics - i.e. physics that is not described by the standard model in its present form - that should enter at an energy scale relevant to the calculation. Since this we do not know about this physics yet, the calculation is necessarily incomplete, which would explain finding a "too short" lifetime of the universe, while with a more complete theory one would (hopefully) find a result, that explains observed lifetime of the universe. The fact that the paper finds a "long enough" lifetime of the universe, could be seen as an indication that the theory is able to make predictions at energy scales relevant to this calculation.