231–240 of 301 posts
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Neutrinos faster than light had 6 sigma. It just shows probabilistic significance. Confirmation by independent research teams helps eliminate calculation and execution errors.
As I recall, FTL neutrinos were the result of experimental error, not chance; and so are outside the scope of what sigma screen for.
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Just to expand a bit, the sigma symbol is a standard symbol used to indicate the standard deviation of a measurement, and standard deviation is roughly a measure of how much variation there is within a data set (and consequently how confident you can be in your measurement). So when they say that the theoretical result is now 4.2 sigma (units of standard deviation) away from the experimental result instead of 2.7 sig…
> Again, this assumes both that there were no errors made in the experiment This is worth repeating a lot when explaining sigma (even in a great and comprehensive explanation such as yours): Statistical anomalies are only relevant when the experiment itself is sound. Imagine you are trying to see whether two brands of cake mix have different density (maybe you want to get a good initial idea whether they could be the…
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The creation of new particles, is that bremsstrahlung?? I’m trying to find more info on it.
Bremsstrahlung is not the creation of virtual particles, though it does involve a virtual photon. It is rather the radiation of (real) photons by electrons when they suddenly "decelerate" (i.e. collide with other charged particles). In fact the name "bremsstrahlung" means "braking radiation," if memory serves.
I think it'd be more accurate to say "interact" instead of "collide" – the electron could still be far away from the charged particle. More generally, bremsstrahlung also occurs when an electron's velocity vector (not necessarily its modulus) changes, i.e. when the electron changes direction, like in a synchroton.
> In fact the name "bremsstrahlung" means "braking radiation," if memory serves.
That's correct :)
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Let me say that this is the best thing that I ever saw in science: people using art to explain extremely complex findings that might change the future in a bit. I laughed a bit on 'I don't know you anymore'. When I was younger, I remember to read cyberpunk comics quite a lot. They explain a vision of the future that is improbable, but in many ways it get stuff right. Imagine aligning this with real word science. Imag…
I used to read the Cartoon Guide to... books as a kid: https://www.amazon.com/Cartoon-Guide-Physics/dp/0062731009 . They were great.
which are pretty great.
I can't wait for PBS Spacetime to tell me what to think about this.
Am I the only one who barely understands anything from that show? Every episode I hear a dozen barely explained confusing terms with quantum this and higgs-field that. I feel like they care more about impressing me with how complicated this stuff is than they do about actually teaching me much. Maybe I'm just not the target audience :(
My own impression of SpaceTime is that they are consistent and chronological. I wouldn’t understand that math on my own nor make any inferences, but conceptually everything is pretty clear to me.
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No, the essence of my point is that the number of sigmas is meaningless when you have a systematic error — in either the experiment or the theoretical estimate — all that the sigmas tell you is that the two are mismatched. If a mistake could happen once, a similar mistake could easily happen again, so we need to be extremely wary of taking the sigmas at face value. (Eg: the DAMA experiment reports dark matter detecti…
The systematic errors enter the sigma calculation, doesn’t it?
Systematic errors can easily remain hidden. The faster-than-light neutrino had 6-sigma confidence[0], but 4 other labs couldn't reproduce the results. In the end it was attributed to fiber optic timing errors.
So if you don't know you have a system error, then you can very easily get great confidence in fundamentally flawed results.
[0] https://en.wikipedia.org/wiki/Neutrino#Superluminal_neutrino...
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Lagrangian mechanics is equivalent to Newtonian mechanics, but doesn't involve force https://en.wikipedia.org/wiki/Lagrangian_mechanics The idea of replacing a 'gravitational force' with spacetime curvature gave us General Relativity; extending this same idea to electromagnetism gives us Kaluza-Klein theory https://en.wikipedia.org/wiki/Kaluza%E2%80%93Klein_theory The current state of the art is Quantum Field Theory…
I still need someone to ELI5 to me how space curvature model explains the attraction between two bodies that have a delta-v of 0.
For a curvature based model, the delta v being 0 means that the gradients around each body are equal to each other, but that doesn't say anything about what's causing those gradients.
To find this "attraction", you have to calculate the curvature while leaving some sources out
What is everyones favorite book on quantum mechanics (I would love understand more of the 3 generations of matter)?
A great intro is Sean Carroll's youtube series "The Biggest Ideas in the Universe". https://www.youtube.com/playlist?list=PLrxfgDEc2NxZJcWcrxH3j...
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Lowercase Sigma
Just to expand a bit, the sigma symbol is a standard symbol used to indicate the standard deviation of a measurement, and standard deviation is roughly a measure of how much variation there is within a data set (and consequently how confident you can be in your measurement). So when they say that the theoretical result is now 4.2 sigma (units of standard deviation) away from the experimental result instead of 2.7 sig…
No, this is a p-value misinterpretation. Sigma has to do with the probability that, if the null hypothesis were true, the observed data would be generated. It does not reflect the probability that any hypothesis is true given the data.
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Sure they can fit any experimental result that way, they can probably fit any 19 experimental results that way, but in general if you would freely adjust a constant to fit one experiment then it would stop fitting other experiments.
Do we need TDD for particle physics so CI could run tests on what experiments break when merging a theory
As a sibling comment points out, it is difficult to implement the markup that spans the space of all possible theories. Kostelecky's parametric Standard Model Extension offers one avenue to do so.
One could implement such a test as a checklist, too, which might already make a difference.