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## A reasonable question from a flat-Earther

Most people ridiculed the post, saying that it didn’t make any sense—that it was just the ramblings of a crazed flat-Earther.

I disagree.  Much of the post makes perfect sense.  I think it deserves to be answered scientifically, and the conclusions might surprise you.

What is the poster trying to say, exactly?

“…the atmosphere near the equator would be spinning around at over 1000 mph…”

True.  The velocity of anything on the surface of the Earth at the equator would be v = 2πr/T = 463 m/s = 1036 mph.  Way to go, flat-Earther!

“…and gradually slower down to the poles where the atmosphere would be unaffected at 0 mph.”

True.  So what’s the problem?

“…this alleged force…[is] proven non-existent by the ability of airplanes to fly unabated in any direction without experiencing any such atmospheric changes.”

So apparently, the flat-Earther is bothered by the idea that you can be going 0 mph at the North Pole and 1000 mph at the equator, and that if you flew from the North Pole to the equator, you would speed up by 1000 mph, which would seem to be noticeable.

Well, that objection seems reasonable to me!  It doesn’t sound totally absurd.  But since we know the Earth is round, where has our intuition failed us?  If I flew from the North Pole to the equator, how come the 1000 mph difference wouldn’t, in fact, be noticeable?

First, the 1000 mph at the equator won’t show up on your speedometer, of course.  I’m not exactly sure how an airplane speedometer works, but it’s surely going to tell you your velocity relative to the ground (or air) around you.  So if you’re at the equator and you’re spinning with the Earth, that speed won’t be apparent.

But maybe you can feel the change in your speed as you go from 0 to 1000 mph?  Why don’t we notice this acceleration?

It’s a matter of scale.  Suppose I’m in a 747 cruising at 255 m/s, and I fly from the North Pole to the Equator (I know, I know, that’s a bit too far without refueling…)  The distance is about 10 million meters, so it takes 10,000,000/255 = 39,216 s (not quite 11 hrs.)  My North/South velocity doesn’t change, but in the lateral direction my velocity goes from 0 up to 463 m/s, to catch up with the spinning Earth.  This represents an acceleration of Δvt = 463/39216 = 0.0118 m/s2, which is below the threshold of human detection (around 0.065 m/s2 for lateral motion).  For a 100-kg person, this represents a force of around 1 Newton (i.e. about a quarter of a pound) which would be easily detectable with laboratory apparatus, but is not noticeable by an individual, since the 980 N pull on you downward (due to gravity) drowns it out.  (For the same reason, a 100-kg person doesn’t feel the pull of the Sun, even though it’s a respectable 0.6 N).

The conclusion is simple: the flat-Earther is right except for one thing: the change (going from 0 to 1000 mph as you travel South) happens too gradually for humans to detect.  I believe this is just a matter of underestimating the size of the Earth.  0 to 1000 mph seems like a big difference, but the Earth is huge.

Not every objection to science is ridiculous.  The best way to combat ignorance is with scientific argument, not ad hominem attacks.  So please, please, don’t make fun of these fusty nuts with no kernels.  They’re too dumb to get most insults, anyway.

### 5 Responses

1. I was just thinking earlier today how much I would enjoy another Many World Theory Post! Thanks!
A shout out to the Many Worlds Interpretation near the end

• I sort of took the summer off. But now I’m back!

2. Fourat Janabi explains quite well in his book that the orginal flat earthers`weren’t actually all that far wrong in their calculations. Where they messed up was, like here, in factoring in the scale of the planet.

And I agree with Drak, it’s good to see you back.

3. Good post but with one mistake:
> (For the same reason, a 100-kg person doesn’t feel the pull of the Sun, even though it’s a respectable 0.6 N).

Actually the person (with Earth) is in (nearly) free fall relative to the sun.

• The force exists of course, but you’re right, you don’t feel it if the normal force is zero. I stand corrected.