My apartment looks west across the Schuylkill River over the Poweltown and Mantua sections of west Philadelphia. Since I’m on the 14th floor, I’m high enough to see the horizon stretching from the other side of the Philadelphia Museum of Art to the wooded high ground in Poweltown.
In the summer the afternoon sun blazes directly into my apartment. It’s so hot I have to shut the shades, even with the air conditioning on. Gradually since the summer solstice, the sun has moved to the left, the south, so that by late afternoon it’s shining more sideways across my balcony. I can leave my blinds open and enjoy the scene. The light displays at sunset are not so dramatic as we get into winter, but I’ve always appreciated the steel grey skies of late December afternoons in this region.
I said that the sun “moved.” Not accurate at all. What’s really been happening is that the tilt of the earth’s rotation has been changing direction, from its maximum pointing at the sun at the summer solstice to maximum pointing away from the sun at the winter solstice. I’ve been aware of how this change in the earth’s tilt accounts for changes in the length of daylight and seasonal temperatures. When I was commuting to work, I was aware of the sun’s becoming lower and lower in the sky to get in my eyes and interfere with driving.
But I’ve never been in one place, high enough and long enough to observe how these changes also affect the apparent position of the setting sun on the horizon.
So, I go back to my opening sentence. How can I be looking “west” at the summer sun when it’s not there when I’m look “west” in the winter? I haven’t moved. My building hasn’t moved. The sun hasn’t moved. What’s going on? As with so many things we take for granted as fixed and permanent, directions like east and west lose some of their meaning outside of our narrow, earth-bound vision.