211–220 of 301 posts
There was a nice explanation of the finding in comic format from APS & PhD Comics: https://physics.aps.org/articles/v14/47
This sound like the hypothesized „subtle-matter“ as proposed by Dr. Klaus Volkamer [1]? - still looking for a better link than the Book… I’ll update this later [1] https://amzn.to/3mvvsWW
Physics noob question: is there any physical framework that does away with the concept of "force"? I know a bit about how it is reconceptualized as space-time deformation in the context of general relativity, but that's about it. It just seems like one of those inherently anthropocentric concepts that (potentially) holds us back from exploring something different?
> It just seems like one of those inherently anthropocentric concepts that (potentially) holds us back from exploring something different? This is something I struggle with. I know that physics originated from an experimental framework. We observe phenomena, then we try to come up with explanations for said phenomena, formulate hypothesis, then test them. That is fine. But this breaks down when the 'fundamental force…
This sounds silly but it's exactly the root cause in the current understanding and shoehorning in the word "force" in "force-carrying particles" is a stretch and causes this confusion. It's true that there would be no electromagnetic force without the photons. But photons and their likes are not the only way a "force" arises. For example, the Pauli exclusion principle can be seen as a "force" and it arises without photons with just electrons.
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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.
An attempt at a true ELI5 is the bodies exist in what we know as spacetime, not as separate independent concepts of space and time which we perceive from our day to day experience, so we have to know a bit about the difference. Chiefly in spacetime everything always travels the same "speed" (c, the universal speed limit) and it's just a matter of how much of that speed appears as "traveling through space" and how muc…
Genuine question from ignorance. Is this related to this work at CERN? https://www.theguardian.com/science/2021/mar/23/large-hadron...
Fun!
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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?
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 :(
Earlier quoted context omitted.
An attempt at a true ELI5 is the bodies exist in what we know as spacetime, not as separate independent concepts of space and time which we perceive from our day to day experience, so we have to know a bit about the difference. Chiefly in spacetime everything always travels the same "speed" (c, the universal speed limit) and it's just a matter of how much of that speed appears as "traveling through space" and how muc…
That's the best explanation I've ever heard. I'd like to know if it really is mathematically rigorous. If so, bravo.
The "spacetime speed vector" is more formally the four-velocity and it's true that the norm of this 3 component space 1 component time vector is strictly tied to c. At the same time the four-velocity doesn't actually mathematically behave like a euclidean vector space vector where you can just add another like vector describing the effects of the warping and call it a day. In reality you have to run it through the metric tensor first (some function for the given instance that describes the geometry of warped spacetime) to get things in a coordinate space that is usable. Once you have that you actually have to run it through the geodesic equation to see what the acceleration will be as using the mapped four-vector alone will only tell you about the current velocity components in your coordinate space not the effect of the spacetime warping on something in them. These kinds of differences are the bits I swept under the rug as "nuance in how things actually change" but the net concept of the four-vector shifting components due to the warping of spacetime as an object moves along its world line is 100% the net result.
Also I can't really take credit for the method of explanation, just some of the simplified wording. I do find this explanation not only infinitely more accurate but actually easier to understand than the damn rubber sheet analogies or even improved/3D space warping analogies as they still leave out the time portion of the spacetime gradient which actually plays a bigger role in these examples.
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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…
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 same cake mix). You can do this by weighing the same amount (volume) of cake mix repeatedly, and comparing the mean value for weight measurements of either brand. That works well, but it totally breaks down if you consistently use a glass bowl for one brand, and a steel bowl for the other brand. You will get very high units of sigma, but not because of the cake mix.
There was a nice explanation of the finding in comic format from APS & PhD Comics: https://physics.aps.org/articles/v14/47
They mystery here is why that comic image that is inlined into the page loads so slowly, but if you click on it while it is loading, you get a pop-up which shows the whole darn thing almost instantly, at what looks like the same resolution, even as the in-line one is still loading. Spooky quantum effect, there!
I didn't feel the need to click anything.