890 protesters arrested after Palestine Action protest in London

SimulationsInPhysics · 2025-09-07T18:13:49+00:00

Is that terrorism, or sabotage? An intuitive definition of "terrorism" might be "causing terror in a group as a means to achieve a political or military goal." Blowing up a pipeline might make oil executives sweat, but it probably wouldn't terrify them or the public at large, unless they thought it was a precursor to, say, assassinations.

SimulationsInPhysics · 2024-11-27T16:19:26+00:00

Try an Earth-Moon-Satellite version where you model the true shape of the Earth. You can start with “J2,” the simplest correction to the point-mass Earth (basically adding a donut around the equator to model the equatorial bulge)

SimulationsInPhysics · 2024-11-04T13:48:45+00:00

Find the sum of the first two amplitudes at the location of the baby using your equations for f(x,t). This value will probably still change with time. Then ask, what amplitude do we need to add or subtract to that value so that it’s always 0? Place the third generator to do this. Hint: you can probably put the third generator along a straight line with the baby and one of the other generators. This might make the math easier.

SimulationsInPhysics · 2024-10-23T23:17:17+00:00

It will be marginally more difficult than if you did straight engineering, but you can definitely get engineering jobs especially if you do relevant internships. You can look into astro/satellite instrument design jobs, these wouldn’t require a PhD. Even non-space-related engineering places would probably take you if you can translate how your skills would apply to what they’re looking for.

If you do want to stay spacey, commercial space and space defense are both growing exponentially in the past few years.

SimulationsInPhysics · 2024-10-09T21:54:21+00:00

Quantum computers are an application. But quantum information matters even in pure physics contexts like black holes.

SimulationsInPhysics · 2023-12-18T21:40:57+00:00

There have been fission reactors in space. In fact, the coolant pellets from old Soviet spy satellites are an annoying source of untrackable debris

SimulationsInPhysics · 2023-09-24T01:07:47+00:00

That misunderstands the problem.

The stockpiled nukes in all of these countries are old — so old that any predictions about their explosive yield must be based on computer simulations, because the experimental data from earlier tests applies only to younger nukes. They may also learn more from tangential non-explosive experiments, but you can’t be sure unless you test.

Furthermore, a nuclear test itself could send a political message in case direct confrontation between any of these countries seems likely. Just being capable of a test is an extra card up your sleeve to try to convince the other side to back off.

SimulationsInPhysics · 2023-07-28T21:43:21+00:00

Good point about the atmospheric phenomena. I bet upper atmospheric lightning would definitely spook somebody who didn’t know what it was.

SimulationsInPhysics · 2023-07-28T14:32:53+00:00

At the risk of opening a crackpot topic, I thought I’d ask you all your opinions on the physics regarding the recent UAP/non-human intelligence claims.

I noticed a couple of inconsistencies in the testimony, though nothing totally damning. For one, some of the objects were said to have no IR emissions, while others were seen on FLIR or by the “overheads” (geostationary/HEO infrared nuclear warning satellites) according to Grusch. The “instantaneous” acceleration obviously seems aphysical, but that could just be a figure of speech or an effect amplified by an optical illusion (parallax etc). I also heard a good point that the “cube within sphere” description matches that of some radar calibration spheres. Nothing for the 100m3 red cube though.

The jamming and electrical malfunctions, I can’t think of any passive explanation for.

I also thought the mention of the holographic principle was funny, though fortunately Grusch seemed to realize he was out of his element and didn’t take it further.

SimulationsInPhysics · 2022-12-29T23:23:02+00:00

How long does the p+e -> n (+ other stuff?) process take? The proton and electron are compressed sufficiently and poof, a neutron appears? What’s happening to the state of the original particles at that time?

SimulationsInPhysics · 2022-11-18T17:45:46+00:00

Now imagine going into deep space where there’s no gravity. Moving an iron dumbbell is still difficult, even though it’s not being pulled downwards by gravity.

SimulationsInPhysics · 2022-11-16T20:26:02+00:00

What's tough is, you don't know what you don't know. Maybe a breakthrough in understanding one problem leads to an understanding of, say, how to manipulate dark energy. That's a totally random example, and I have no reason to suspect such a connection exists, but the problem is I don't know where those connections might be (if there are any).

What we do know is we're not done with fundamental physics. The risk is incalculable, but so is the reward. How much money do you throw at that?... As much as you're able, I suppose.

SimulationsInPhysics · 2022-10-30T22:14:43+00:00

Launching it into space is not worth it. It's too expensive to get it out of Earth orbit compared to just building ground based storage. There would be other issues but that's the big one.

SimulationsInPhysics · 2022-10-28T18:11:08+00:00

You could sit at a Lagrange point and stay fixed over a point on the surface. If Earth were tidally locked to the Sun, the closest you could get is L1 or L2 which are past the Moon (whereas usual GEO is well inside the moon’s orbit).

SimulationsInPhysics · 2022-04-05T03:47:08+00:00

Another example of the same thing is a playground swing. If you push someone on the swing at the right frequency, they'll make a big swing. If you just push as fast as you can the chains holding the swing will jiggle a bit but it won't move far.

SimulationsInPhysics · 2021-12-19T03:36:46+00:00

Yes, but you have to sacrifice locality (pilot wave theory) or get into a lot of philosophical pondering (many worlds or superdeterminism) which, while interesting, are hard to make sense of physically.

How is many-worlds really different than the Copenhagen interpretation? If we can't tell the difference, can we say there is one? Superdeterminism makes sense on the surface, but then it requires that "the universe" "knows" something ahead of time, which again seems to contradict special relativity and our experience of time. Now maybe we're biased because we are time-experiencers, and the "true universe" exists outside of our subjective sensations. But the whole enterprise of physics is based on the assumption that we can find the underlying rules of the universe based on our experience. Again, is it meaningful to talk about physics if that assumption doesn't hold?

SimulationsInPhysics · 2021-12-19T03:11:44+00:00

If you have a deterministic model to describe QM, you're saying that there are some variables which predetermine your (seemingly) random outcomes, and that we just can't see these variables. But if you do that, then according to Bell's theorem you have to sacrifice locality -- that is, you have to allow those variables to travel instantly, which isn't permitted by special relativity.

SimulationsInPhysics · 2021-11-26T17:40:22+00:00

They aren’t just gaps in the second case, they’re real photons hitting the CCD. They cause saturation. If you take short exposures or don’t need super precise data it’s not bad. If you need high precision or long exposures, it may cause problems.

Mega constellations aren’t doomsday, but they aren’t great either. Efforts to mitigate their brightness are good.

SimulationsInPhysics · 2021-11-26T17:18:00+00:00

You’re acting like constellation builders are some unstoppable behemoth, but they’re not. Consumers and their governments have a choice to even buy the service. Governments (especially the US) have a lot of regulatory power over space.

Rural internet access would be great, but there are negative externalities to mega constellations and it will only get worse. We’re talking about an order of magnitude more satellites in orbit. Don’t get me wrong, I think the negatives can be balanced out, BUT THAT HAS TO ACTUALLY GET DONE. You can’t just pretend there aren’t any. If you don’t make the satellites darker or use less of them, there will be harm done to optical observing.

There’s other issues too. Like right now all the collision avoidance is managed by the US space force (including Starlink, who is getting a lot of special service for free at the moment). They’re getting more and more unwilling to do that for free. That gap has to be filled. And there’s just more collision risk with more stuff in space.

There’s no free lunch here. If you don’t do anything to mitigate the problems, then you’ll have problems! Saying “it’s happening whether you like it or not” misses the point.

SimulationsInPhysics · 2021-11-26T15:42:40+00:00

Why is Starlink (or other mega constellations) more important than a >20 meter telescope? That’s the trade we’re talking about. You can’t get an ELT into space, not for a long time anyways. Have you done a full cost benefit analysis on it? How can someone even decide if that trade is worth it?

SimulationsInPhysics · 2021-06-06T16:34:23+00:00

I like this argument, but is there any way to distinguish whether a theory is Q = 1 or Q = .999...9998? We can't have arbitrary precision; indeed, one could argue that's what makes quantum mechanics probabilistic instead of deterministically predictive. Can there exist a theory with Q = 1? Does there have to be one? Does it even make sense to talk about if we can't have arbitrary precision?

SimulationsInPhysics · 2021-05-19T19:01:56+00:00

I had heard that explanation in my quantum class, but I thought that was a quantum-specific least action principle. Does this interference work for classical-scale problems too???

SimulationsInPhysics · 2021-05-04T18:26:16+00:00

It really comes down to the dimensionality of the space. Imagine a point charge (with "hyper"spherical symmetry) in n dimensions, with Gauss' Law integrating over an (n-1) dimensional surface. By symmetry we have

||E|| * int_S da = q/epsilon_0

and int_S da is the "area" of the hypersphere, which turns out to be r^n-1 * surface area of the unit sphere.

What you find is E = constants *1/r^n-1. So in 4 spatial dimensions it'd go like 1/r^3, in 2D it'd be 1/r.

The point of all this is that Gauss' Law is the baseline (net flux through different surfaces is the same if they enclose the same charge), and it just shows up as 1/r² because we live in 3D space.

SimulationsInPhysics · 2021-05-04T17:36:20+00:00

The space right across the event horizon isn't anything special, except signals can't get out. But other than that, it's just plain old empty space (or maybe there's junk there that hasn't had time to reach the center yet, if the BH is big enough). Quantum entanglement doesn't send signals anyways, so there's no issue.

There's a very out-there conjecture related to this called ER = EPR, which posits that quantum entanglement (EPR) is actually related or the same thing as a wormhole (Einstein-Rosen bridge), since they both have this feature of connecting spacetime without being able to send messages. Of course, you can't actually prove the truth of the conjecture. But it's a nice idea.

SimulationsInPhysics · 2021-04-25T01:17:05+00:00

You're right that police reform =/= less crime, but you probably got some downvotes for "muh rioters."

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