[ExI] astonishing

[Adrian Tymes]

Huh, and here I thought you were going to talk about the tree on the left,
and ignore all that visual clutter.

On Sat, Mar 20, 2021 at 7:24 AM spike jones via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

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> Study this photo and tell me what you see please.
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> The explanation is wicked cool.
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> This was taken on a camping trip last weekend at a National Park and is a
> 30 second duration.
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> OK everyone saw Orion up there on top right quadrant of the photo.
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> Our eyes are drawn to the cosmos, but consider the visual clutter at the
> bottom of the photo, which I needed to explain to my scouts why the stars
> in the photo appeared streaky, all of them.  The structure is a public
> restroom but it doesn’t have windows.  So that vertical light artifact on
> the left end of the streak is caused by reflected light from a door opening
> and closing with a light on inside the restroom.
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> The roof of a foreground car eclipses part of the undulating light path,
> which is caused by a dual LED headlamp worn by a walking person.  The
> orange glow on the building is stray light perhaps from the headlamp.
> There is another feature on the right end of the undulating streak which I
> think is stray light reflecting off of a person entering the restroom from
> a door on the other side of the restroom.
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> The undulating streak is interrupted by being eclipsed by a van, also in
> the foreground so it isn’t as close but allows you to get a scale and helps
> show the undulations are not steps.  They are too far apart for that.
> Those are caused by the headlamp wearer looking down at the path and up
> ahead (I think that would explain that sinusoid and also why there are only
> about 5 or 6 total undulations in 30 seconds.
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> On the right end of that light streak the light path diverges into two
> separate streaks caused by (I think) the dual LEDs in the headlamp.
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> OK then, now we are ready to talk about the stars.  When we zoomed in on
> the photo, the stars were all streaks.  I used this photo to explain to the
> scouts why this is: the earth rotates while the camera is gathering light.
> They weren’t sure they believed it, so I had them figure out how many
> degrees the earth rotates in an hour: 360 degrees divided by 24 is 15
> degrees an hour.  OK how much per minute?  The sharp ones could divide in
> their heads, 15 over 60 is quarter of a degree a minute.  OK how much in 30
> seconds?  Eighth of a degree.  OK then, those stars dang sure would show as
> streaks, just as one guy with a headlamp (who you can’t see because he
> didn’t stand still long enough) made the sinusoidal streak.
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> There is a fun follow up post coming soon but I gotta run.  More later,
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> spike
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