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Very Wrong Math

charlespetzold.com

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Re: Very Wrong Math

#51

Post by nkrisc »

munch117 wrote: post #41
tempestn wrote: post #29

Earlier quoted context omitted.

Depends what causes things to stick to the flat Earth. IIRC flat earthers have various explanations for gravity, including the disc continuously accelerating upward; in that case you'd experience the same force everywhere on it.

If this mysterious disc-accelerating force also accelerated the people and things on the surface, we'd all be weightless. I guess it must be a pushing force from below. So, who's doing the pushing? I'm thinking a big turtle.

They mean it is actually accelerating constantly.

My math might be wrong, but if we were accelerating at 9.8m/s/s for at least 4000 years (roughly as long as we have continuously recorded history and the minimum time “gravity” has been observed) then we ought to currently be traveling through space at over 1,000,000,000,000m/s.

Now I’m no physicist, but I reckon that might end up violating causality.

Re: Very Wrong Math

#52

Post by userbinator »

seanhunter wrote: post #14

I have seen a very similar (incorrect) argument used to justify the idea of a flat earth. A builder on youtube made the argument (with a similar out of scale drawing of the earth) that if he drops a plumb bob and makes a right angle so he has a straight horizontal line and then goes across that line for a bit and drops another plumb bob, the two lines he has dropped are parallel, "proving" that the surface of the ear…

The earth is just much much much bigger than in the diagram so the effect is within the margin of error for the measurement he was taking.

It's actually measurable on a human scale:

https://www.mathscinotes.com/2017/01/effect-of-earths-curvat...

1 5/8" difference over 693', or slightly less than 1 part in 5 thousand --- definitely measurable on a smaller scale with accurate machinists' tools.

Re: Very Wrong Math

#53

Post by lukan »

tempestn wrote: post #29
munch117 wrote: post #23

Earlier quoted context omitted.

Ah, but would they actually be parallel on a flat earth? Say the earth is disc-shaped. Then the center of gravity is only directly beneath you if you're standing at the exact center. You get ever-so-slightly not parallel lines, just like on a round earth. The fun part of a disc-shaped earth comes as you move towards the sides, and gravity, still pointing towards the center, makes you stand at an increasingly acute an…

Depends what causes things to stick to the flat Earth. IIRC flat earthers have various explanations for gravity, including the disc continuously accelerating upward; in that case you'd experience the same force everywhere on it.

The theological argument I recently heard is, the creator just made up and down. And things move down. But it is not gravity.

Re: Very Wrong Math

#54

Post by simplicio »

Seems intuitively obvious. On a flat Earth the two distances would be the same, and while the Earth isn't flat, its close enough to approximate a flat surface for most purposes, so you'd expect the differences in the two arcs to be ~0

Re: Very Wrong Math

#55

Post by ben_w »

seanhunter wrote: post #14

I have seen a very similar (incorrect) argument used to justify the idea of a flat earth. A builder on youtube made the argument (with a similar out of scale drawing of the earth) that if he drops a plumb bob and makes a right angle so he has a straight horizontal line and then goes across that line for a bit and drops another plumb bob, the two lines he has dropped are parallel, "proving" that the surface of the ear…

> We joke about LLMs hallucinating but I'm not convinced we are so superior when we are outside our personal "training data".

Every time I see the phrase "common sense", I expect to see an example of the human failing you describe.

Re: Very Wrong Math

#56

Post by lynguist »

I would do it like this:

Approximate Earth as a flat line. (The 5000ft path is close enough that it is also represented by the flat line. This is the 5000ft path.)

Then make the 33000ft path which is a slightly looser line on top of this line.

This new path is not 4 times longer. Just a little bit raised, because 33000 ft is “nothing” compared to Earth. (To become 4x longer we would go deep into outer space and back.)

Re: Very Wrong Math

#57

Post by jbeninger »

nkrisc wrote: post #51
munch117 wrote: post #41

Earlier quoted context omitted.

If this mysterious disc-accelerating force also accelerated the people and things on the surface, we'd all be weightless. I guess it must be a pushing force from below. So, who's doing the pushing? I'm thinking a big turtle.

They mean it is actually accelerating constantly. My math might be wrong, but if we were accelerating at 9.8m/s/s for at least 4000 years (roughly as long as we have continuously recorded history and the minimum time “gravity” has been observed) then we ought to currently be traveling through space at over 1,000,000,000,000m/s. Now I’m no physicist, but I reckon that might end up violating causality.

Nah, when you move that fast, further acceleration stops increasing speed and starts squishing time instead, so you asymptotically approach C.

So I guess what I'm saying is I see absolutely no problem with the flat earth arguments?

Re: Very Wrong Math

#58

Post by Derbasti »

prmph wrote: post #37

One question I've always had with this: How does the rotation of the earth affect an airplane's flight time, if any? And how does this change with altitude?

In general, the air moves with the ground, so the earth's rotation does not affect airplanes.

However, rotation of the earth imparts a coriolis force on the air, which results in jetstream winds. Aircraft routes are optimized to use/avoid jetstreams for shorter travel times.

Re: Very Wrong Math

#60

Post by kergonath »

seanhunter wrote: post #49
kergonath wrote: post #42

Earlier quoted context omitted.

> I have it on good authority that this is still going on Do you mean making simplifying assumptions to make a problem tractable? Of course it’s still going on. It has to be , otherwise you just cannot do anything. > Assume the penguin's beak is a cone It is impossible to consider the true shape of a penguin’s beak for several reasons: - you’d need to go all the way down to the electron clouds of the atoms of the bea…

Bet you’re fun at parties as they say. I totally understand why simplifying assumptions are helpful in modelling and definitely don’t need you to explain that. It also is a bit ridiculous if you think literally about it which makes it something that is fun to laugh about as here.

Yes, sure, I get the jokes. I just found it puzzling that someone would think it stopped.

And I don’t talk about work at parties anyway :)

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