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The ballon was at 60k feet and eye witnesses said it had the same apparent size in the sky as passenger jets flying nearby at 30k feet.

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if only i paid attention in trigonometry..

Hmm, do we even need trig? Naively I would imagine that simple proportions would hold — e.g. same visible size @ twice the distance = object is twice as big

4x as big, since we see in two dimensions — you can judge length & height (but not depth).

So if it appears the same size but twice as far away, the the length and height are each 2x. So that would make it the size of ~4 airplanes

Not super relevant but I find this to be true when spotting a 747/757/767 vs say a 737

the area is 4x but the diameter is just 2x here.

Isn’t the object three-dimensional?

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