# An airliner's shadow

**URL:** <https://boards.straightdope.com/t/an-airliners-shadow/644909>\
**Category:** Miscellaneous and Personal Stuff I Must Share\
**Created:** [December 23, 2012, 7:55am UTC](https://boards.straightdope.com/t/an-airliners-shadow/644909 "2012-12-23T07:55:09Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![the\_diego](https://avatars.discourse-cdn.com/v4/letter/t/7bcc69/32.png) [@the\_diego](https://boards.straightdope.com/u/the_diego)\
**Post date:** [December 23, 2012, 7:55am UTC](https://boards.straightdope.com/t/an-airliners-shadow/644909/1 "2012-12-23T07:55:09Z")

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When riding a jet plane, assuming the time is right and you’re seated in the right seat, you can see the plane’s shadow on the ground. It must be moving as fast as a .45 cal slug. Would a person notice the shadow when it passes over him? Once I was walking alone inside a stadium. Then there was a sudden “blink” in my surroundings, like there was a momentary blink of the sun’s rays. No, it’s not low-lying clouds changing the sun’s brightness. I can actually see cloud shadows on the ground. They (clouds) don’t move that fast. Could it have been an airplane’s shadow?

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**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\
**Post date:** [December 23, 2012, 8:26am UTC](https://boards.straightdope.com/t/an-airliners-shadow/644909/2 "2012-12-23T08:26:58Z")

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Sure. I’ve had one pass over me any number of times.

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**Author:** ![GuanoLad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/guanolad/32/42_2.png) [@GuanoLad](https://boards.straightdope.com/u/GuanoLad)\
**Post date:** [December 23, 2012, 12:01pm UTC](https://boards.straightdope.com/t/an-airliners-shadow/644909/3 "2012-12-23T12:01:47Z")

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My house is beneath a flight path. Depending on the time of year, and the sunniness of the weather, I notice the shadows of planes flicker past several times a week, sometimes many in a day.

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**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\
**Post date:** [December 23, 2012, 3:19pm UTC](https://boards.straightdope.com/t/an-airliners-shadow/644909/4 "2012-12-23T15:19:47Z")

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It does happen, but the airplane needs to be at a fairly low altitude for it to eclipse the sun. At cruise altitude, it would just be a small dot moving across the sun, and you wouldn’t even notice the dimming caused by it.

(Or to put it another way, at high altitude the airplane only creates a [penumbra](http://en.wikipedia.org/wiki/Umbra#Penumbra).)