The h Bar

Q: How much energy does a breaching sandworm generate

12:37 PM

Do you think this question could be tweaked to be Physics appropriate?

1

So this started out a question related to a Dungeons and Dragons session I had once, where I was playing a druid and used the spell Bones of the Earth and the fate of a Purple Worm, now known affectionately as Chad. Our DM of the session has a penchant for the Rule of Cool, and tends to ignore ce...

One of our members has already started some crude calculations:

Off topic, but.... For a rock with a density of 3000 kg/cubic meter, the mass of each column is about 2×10^6 kg. If the rocks are subject to constant acceleration before magically stopping, and the whole column travels 30 feet (about 10 meters) in less than a single round (6 seconds), then d = 0.5*a*t^2 + v0*t, or 10 = 18*a, and a is approximately 0.5 meters per second squared. Then the force on each column is about 10^6 newtons. It exerts this force on the purple work for 30 feet, until it magically comes to a stop, imparting 10^7 joules of energy per column. — Adamant yesterday

so I'm guessing it's possible, but not sure if it would be welcome?

@AncientSwordRage It's too vague currently to be about physics, but anything more precise will turn it into something just asking for a calculation like that comment does, so it would be likely off-topic under our homework-and-exercises policy

@ACuriousMind hmmm, there's no middle ground?

Because it's possible that the OP doesn't know what equation to use

@AncientSwordRage You're asking for the force, in newtons, produced by a spell?

::shakes head::

2

@AncientSwordRage Yes, but "What equation do I have to use to compute the result?" isn't sufficient to make it on-topic

user 147593

@EmilioPisanty just like they asked about the aether :P

12:48 PM

We're a bit stricter than many other sites - not every question that is arguably about physics is on-topic here

I don't really see a way to turn this into a question that would be well-received here

user 147593

but, we do argue :-)

I agree with ACM. First off, if you take away the physics, it's just asking for a calculation (OT via homework).

But besides that, there just isn't enough information there to produce a physically plausible question

> the spell moves six cylinders of rock 5ft wide from ground level to 30 ft tall instantaneously and how much force that would produce (imagine a piston moving that fast)

regardless of the "spell" context, that's already not physics

well, the answer clearly is that it produces infinite force and anything hit by the cylinders should be atomized, not launched into space ;)

you can't judge force without knowing the time it takes for the change in velocity (starting and stopping)

user 147593

1:05 PM

::knods head::

Q: Shy is 20% enrihment for Uranium considered the minimum for making a nuke?

0

I get that this is the physical limit - an infinite mass of Uranium would produce a runaway reaction. But an infinite mass is impossible.. Really, what is the minimum % of enrichment of Uranium, that when stacked into a mass, runs away before becoming a black hole?

black-holes radioactivity

oooh, boy

shy→why?

but then

> runs away before becoming a black hole?

any thoughts about how to handle this?

Jim

1:28 PM

@EmilioPisanty the answer is obviously (100+infinitessimal)% enrichment

meaning it's impossible. I'd just ask for a clarification. If they feel there is a minimum, then there must be an amount of enrichment that they know will runaway to a black hole

once you get that answer, I don't know, I guess leave a comment that this doesn't happen and close the question?

1:46 PM

@EmilioPisanty If you think that's strange, wait until you have to discuss with a bunch of physicists how invisibility spells work :P For instance, if light just passes through the invisible object, can you sabotage radiation shielding by making it invisible? (That actually became very relevant in the context!)

2:07 PM

@EmilioPisanty The spell causes an effect, that effect would be associated with some physics. I mean if you phrased it without mentioning the spell, it would be the same physics question.

@ACuriousMind gotcha

A: Are the implications of magic on-topic?

2:22 PM

@AncientSwordRage It's interesting that you're trying to make the case based on the off-the-cuff comedic reaction instead of the detailed physics case of how this is a flawed question.

There's a clear trend of people asking questions about fictional physics where they fall into this rabbit hole (and attempt to pull you in with them) of coming up with one band-aid fix after another, without addressing the core problems. It makes us extremely wary of engaging with any of it. Please don't do it.

There's plenty of relevant threads on meta if you want to dig into it

physics.meta.stackexchange.com/search?q=fictional results, and links within those results

18

No, questions involving magical situations are not generally on topic here. Our help center lists "questions about fictional physics" as one of the off-topic categories. The reason is basically what Kyle Kanos said in a comment, ...Pretend the laws of physics are broken, what does physics say...

as an example