I often have my browser's devtools open since I'm often debugging a snippet. I noticed this message often recently:
Why is Stack Overflow trying to start audio?
Update.
I see it's from an ad?
https://static.adsafeprotected.com/sca.17.4.95.js
Update 2
It happens when this ad appears, From...
@JohnRennie I guess so. ;) Most of the hippy types I knew back in the 1970s were Australians, although I did know a few from the UK & the USA. And they may not have been as hard-core as the hippies that "invaded" Glastonbury.
@CaptainBohemian Yes. And we had an unusually warm autumn. So the cold temperatures are a bit of a shock. Of course, the climate in Sydney is rather mild, compared to some places. So I can't really complain.
I like the places with abundant sunshine. I have been such a place, that is Beijing, where there is sunshine almost every day and if it rains, it only rains for a short period rather a whole day or consecutive several days. I feel this kind of place is so congenial. I can feel energetic in daytime most of time because there is sunshine most of time in daytime.
@CaptainBohemian For 7 years, I lived a bit north of Coffs Harbour. It has a nice climate, but maybe not sunny enough for you. ;) I've been back in Sydney for 2 years, and I don't like the colder winters.
A prolonged period being either rainy or overcast often makes me melancholy. I remember there have once been a month being that way not long ago; that kind of weather is really daunting.
@PM2Ring It's like a person in my Facebook told me he also lives in New South Wales but I foreget the definite place name he said. He said his place can be very hot in summer, like over 40 C and very cold, like below 0 C in winter.
@CaptainBohemian Yes, it sometimes gets over 40°C, but it almost never gets below 0°C near the coast, where most of the population live. It only gets that cold inland, and in the mountains. Our mountains aren't very tall, but we have a long chain of mountains parallel to the east coast, and during winter our southern mountains get plenty of snow.
@RyanUnger The cobordism proof thing implies that the fact that a timelike vector field is nowhere vanishing implies that its flow curves don't have any endpoints, and therefore the curve must end on $S_2$, but is that correct
Couldn't a curve end up on some singularity instead
For Lorentzian manifolds a compact manifold can be geodesically incomplete
"Since this possibility has been excluded by hypothesis, we conclude that every such curve $\gamma$ must have a future endpoint. This endpoint cannot occur in the interior of $M$, for $\xi^\mu$ vanishes nowhere, nor on $S$, since $M$ is isochronous. Thus, the future endpoint of $\gamma$ lies on $S'$"
But if I consider let's say the Clifton-Pohl torus, I get an inextendible curve without an endpoint yet with a finite proper time parametrization
In geometry, the Clifton–Pohl torus is an example of a compact Lorentzian manifold that is not geodesically complete. While every compact Riemannian manifold is also geodesically complete (by the Hopf–Rinow theorem), this space shows that the same implication does not generalize to pseudo-Riemannian manifolds. It is named after Yeaton H. Clifton and William F. Pohl, who described it in 1962 but did not publish their result.
== Definition ==
Consider the manifold
M
=
R
2...
One of the most "embarrassing" failures of modern physics is the current disagreement of measurements of the gravitational constant $G$, well beyond reported uncertainties (and agreeing only to about 1 part in $10^5$). Part of the difficulty is that it's impossible to "screen out" the gravitation...
How would you do a higher precision G measurement? A huge Cavendish balance in a trans-Neptunian orbit? Or maybe an orbit in a plane perpendicular to the ecliptic.
Element symbols work just fine in their own, and unnecessary MathJax just makes them harder to read in situations where MathJax is not enabled
Say, external searches, or the inbox and achievements boxes in other SE sites
@PM2Ring not a particularly good question, I think
Basically, any question that boils down to "is everyone in this particular field, that I don't have any detailed knowledge of, completely incompetent", generally has a simple answer, "no".
Ditto with "I looked but I haven't found any discussion of X in the literature" - the problem is with the "I looked" and not with the literature.
@EmilioPisanty Fair points. I suppose you need to dig pretty deep in the literature to find all those mundane details. Still, it'd be nice to see an answer that explains why G is so hard to measure.
Ok, but the OP does finish with "If not, what am I misunderstanding about the physics of the situation?" But I totally agree that the question should be rephrased so that it doesn't imply that the physicists trying to measure G aren't incompetent.
@EmilioPisanty : Well, it is nice to have symbols (that can appear in equation mode) to be in math mode to be consistent but searchability is an important point.
@PM2Ring He seems to have swapped the link out for a seemingly irrelevant wikipedia link. Now all we need is "a way to do low energy positron generation from quantum vacuum"... sounds totally trivial
... and naturally he adds a new wikipedia link to zero point energy to add to the confusion... ZPE doesn't imply anything about generating positrons from a vacuum, does it?
well except I guess in a virtual particle sense maybe... but not in like a practical generation, get energy from it, sense
@JMac Correct. You can't do work with the vacuum ZPE. Unless the vacuum is actually in a metastable state, and there's actually a lower state which is the true vacuum.
It's the same as trying to make hydroelectricity at the Dead Sea. Sure, the water has gravitational potential energy, but you don't have a lower location for the water to fall to.
@PM2Ring Yeah, makes sense to me. It's called "zero point"; I always see pseudoscience references to it as like a magic energy device; but the term "zero point" (and like 2 seconds of googling) have always made it pretty clear to me that it's just a minimum potential, so you can't do much with it
Greg Egan has a novel, Schild's Ladder, where they prove that the vacuum is metastable. They successfully attempt to induce a vacuum transition to the lower state. And the new vacuum propagates outwards at half the speed of light, destroying the current universe.
@JMac Oh, yeah. The free energy crackpots love ZPE.
On a slightly similar topic, I recently watched season 2 of the German show Dark on Netflix. I've really enjoyed the first two seasons, but the use of pesudoscience terms to explain time travel is hilarious. They discover "dark matter" which then leads to them finding the "god particle" which enables time travel. The show's great IMO; but the abuse of science is so comical it broke some immersion
Oh dear. It's understandable that they'd use jargon words that are probably familiar to the general audience, it's a sci-fi tradition, especially in movies & TV. But it does make it a bit cringe-worthy for people who know what the terms actually mean.
OTOH, I can read old pulp sci-fi from the 20s and 30s that has totally ridiculous stuff. But when I'm reading those stories I just recalibrate my expectations so it doesn't break the suspension of disbelief unless they're internally inconsistent.
Yeah, it wasn't too off-putting, because I wasn't expecting real accurate physics, but it would have been nice if they avoided actual science terms that are so often poorly used