On 21 May 2005 00:39:54 -0400, (DoN. Nichols)
wrote:

In article ,
Sunworshipper wrote:

It's about time to set the alarm at 3 am again. Which brings up a
question I've wondered about for a long time. Is it possible to see
the sine waves in the street lights from say 15 miles away and them
being perpendicular and 15 miles long? They seem awfully rhythmic for
just heat convection. They go back and forth while watching way out
over the city before sunrise.

I doubt that your vision is quick enough to detect 1/120th of a
second half-cycles. TV works with 1/30th second changes of scene, and
movies are even slower, though I forget what the actual frame rate is.
I do remember that it is different between home movie cameras and the
professional ones.

Remember -- the heat convection has a lot of air to work with
between you and those lights. I'll bet that if you spotted a bright
star just above the horizon in about the same direction, you would get
the same sort of variation.

Now -- one possibility (but *very* unlikely) would be that you
are seeing the sum of light powered by two different power grids which
are not precisely at the same frequency, so the brightness of the sum
will vary, if the lights actually vary in intensity fast enough to track
the power line. Incandescent lights will not, but mercury vapor ones
probably will, and the Sodium lights probably will as well, since it is
ionized clouds of the metal vapor which is generating the light, not
overly hot metal filaments.

I say that it is *very* unlikely simply because any two grids
that physically close together would be kept in sync to allow for an
emergency transfer of load from one to the other.

Enjoy,
DoN.


I'll try filming it this summer. I've had other people with me and
they see it also. IIRC it goes back and forth and like clock work.
I've watched for long periods of time and just can't see how
temperature variations could flow in consistent planes. If they slowed
down and sped up down the line I could understand.

I keep telling myself that it should travel way to fast to see it the
way I have. Just something that make me go hmmm.