Please hold your hand up at arm’s length and check which things around you can be blocked from view by your pinkie. Your little finger covers an angle of about one degree, which is about double what you need to cover the Moon—make sure to check this for yourself the next time you do some lunar observing. For an object to cover half a degree, its distance from you needs to be about 115 times its size, so if you’re looking out your airplane window and can cover a 50-meter (Olympic-size) swimming pool with half your pinkie, you’ll know that your altitude is 115 × 50 m = 6 km. In the exact same
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