[ExI] astonishing

[spike at rainier66.com]

Study this photo and tell me what you see please.

 

 



 

The explanation is wicked cool.

 

This was taken on a camping trip last weekend at a National Park and is a 30
second duration.

 

OK everyone saw Orion up there on top right quadrant of the photo.

 

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.

 

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.

 

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.

 

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.

 

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.

 

There is a fun follow up post coming soon but I gotta run.  More later,

 

spike

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