They were asking me WHY the shadows will be half-moons and I was like... cause pinhole photography? Physics?
Ah, a question I can answer! The sun is not a point source of light. It acts like a uniform disk of light in the sky. This is why on a normal sunny day your shadows are, for lack of a better word, soft. A diffuser sort of, but not exactly, does this as well; it takes the light from a point source, aka light bulb, and spreads it out a bit. The little pin holes mirror the sun's disk on the object that the light is projected on. As long as the sun is a disk, that image will be round. As the moon move in front of the sun, you see less and less of a disk and more of a crescent. Now, the light from the sun is still not a point source of light, but it is also not a perfect disk either. The shadows on the ground reflect the change in the shape of the sun as the eclipse progresses. One of the things that I intend on documenting is when shadows stop being soft and start having hard edges. (My guess is at 75% covered but we will see.)
If you have a square light source, by the way, and use a pinhole projector? The image looks more square than round.
Here is a picture that shows rather than explains. Everyone in that outer, perumbra, shadow will see a partial eclipse. Only in the that cone of shadow, the umbra, is the eclipse total.
I'll be in a city called Tate in Georgia - north of Atlanta. Out of the path of totality by a few miles :(
Yea you are maybe 10 miles from the fun stuff. We get to do this again in six and a half years so use this as the excuse to whet the appetite for a total eclipse. Still a bummer, but when work is paying the bills you gotta do what they want you to do, right?
And just because I had it up already for some other sites I looked at the NWS report for Tate. Thunderstorms and 30% chance of rain on the day of. Prepare an out for your gear in case of rain. Hopefully you get to dodge the rain and get some great pictures.