Friday, October 28, 2022
navigating by the star
It occurred to me that the sun moves reasonably fast relative to me. Sometimes it is coming nearer me as in the morning and sometimes going further from me as in the evening. Its light should be slightly bluer in the morning and ever so slightly redder in the evening. Similarly these effects will be greater when near the equator than at the poles.
You could in principle know from the colour of the suns light that you are on some line of equal hue. You dont have even to see the sun directly, and the light could be reflected light just as well.
The shift at a specific point will be greatest to blue at 6am and least at 6pm. As you go towards the poles the shift reduces down basically to zero. At midday the shift will be zero.
I guess the lines of equal hue are those of latitude if you took 6am and 6pm as the poles. Clearly these two points are the points of maximum and minimum hue change.
Could birds use this and a sense of time to navigate without actually seeing the sun. Maybe the mystery organ for navigating is the eye with colour vision
Now all of this is assuming the rotational velicity of the earth on its axis can be observed shifting the spectrum. If not so, you could try using the speed of the earth's orbit around the sun, giving a shift to the average background of the cosmos. It will be bluer in the pm, compared to the am, with a gradual change scoss the sky
Martin
