2017 Aug 21, Total solar eclipse

Location: Nashville, TN
GPS: 36.2213, -86.7564
Environment: just me and 9 friends in the yard/driveway of our Airbnb

Eclipse

This was my first total solar eclipse. It was really really cool!! I’m sure you’ve seen plenty of beautiful photos and read multiple accounts of how amazing and other-worldly it was. I’ll just say that the experience is definitely worth the time/money/energy, and rather than add to the chorus of photos and prose, my write-up here is about the experiments I set up.

I was already inordinately excited for this eclipse and had all my logistics in Nashville booked more than 6 months out. I got an Airbnb for 8 people just northeast of Nashville, which ended up being the perfect location to watch the eclipse. We had a couple other friends join us and we just hung out in the yard and driveway of the Airbnb. There was a tree, which gave us cool leaf pictures and shade for the cheese and frozen grapes, and a really friendly neighborhood cat, who we named Luna and let us observe her behavior during totality. The clouds passed overhead, making us a bit nervous, but we were really lucky that the sky cleared for totality.

One of my favorite Youtube channels is SmarterEveryDay, and this video got me even more excited about doing experiments during the eclipse. I really wanted to get video of the shadow bands and data of our environment.

Shadow bands

Shadow bands are waves of light that occur right before and after totality, when the sun is transitioning between a crescent and a slit. The light rays are collimating (becoming more parallel) and the air refracts the light, creating wavy patterns.

I had a large white sheet of posterboard set up with a camera rolling for a few minutes before/through/after totality. The videos totally shows shadow bands!!

Pre-2nd contact shadow bands.
Post-3rd contact shadow bands.

Here is link to the full video and a link to the same video but with my live video showing in the corner so you can see what else is going on. Fast forward to these timestamps if you don’t want to see the whole thing:
1:10 — pre-2nd contact shadow bands
3:45 — post-3rd contact shadow bands

It’s pretty cool that the direction of the shadow bands change between pre and post totality, which is probably correlated with the direction of the moon covering and uncovering the sun.

I found it interesting that we didn’t notice the shadow bands until after 3rd contact, but the video definitely shows shadow bands before 2nd contact as well. At one point, someone says “what a weird kind of dark”, and we were all noticing how strange everything looked. It was hard to say whether it was because of the color or the darkness, but I also think it was because we were seeing the shadow bands and not realizing what they were, as shadow bands are easier to see on a surface.

Weather measurements

I bought a simple digital thermometer+hygrometer that responds really fast to the environment. I put it in the shade, along with my laptop that didn’t update its timezone. This is why my measurements were all taken in PST and then converted to local time and UTC. The thermometer turns itself off after a couple minutes and when you turn it back on, it defaults to Celsius. I took the first few measurements in Fahrenheit, which you can change with a button, but then got lazy and time-rushed so the rest of the data was recorded in Celsius, hence the decimal weirdness at the top.

Timestamps for reference, in local time:
11:58–1st contact
13:27–2nd contact
13:29–3rd contact
14:54–4th contact

I love that there is >10 degree Fahrenheit drop during the first partial phase, and the reverse rise during the second partial phase. Humidity here is relative to temperature, thus a corresponding inverse graph. I’ve submitted this data to the GLOBE project, which promotes citizen science.

My husband Eyal built a weather station with more sensors. Check out the graphs in his write-up.

Other observations

I live-streamed a few minutes before, during, and after totality, for which I’m really glad I did. Now when I rewatch it, I can look for things that I didn’t notice before. Here is the video. For example, I don’t know exactly when the house light came on due to decrease in light, but in the video, it’s definitely off at 3:33, but at 3:46, it’s on.

I didn’t really notice or look for stars, but you can clearly see Venus in the video at 4:35.

The insects gave us some background noise, which we didn’t notice until it was after totality. But in my live video, you can hear them starting to crescendo ~3:00 to ~4:00. And then they quieted down going into totality. After totality, around 7:09, they got super loud, right when we noticed the shadow bands. It’s a little hard to tell the volume of the bugs for most of the video, but ~9:00, they are definitely much quieter. After some internet research, I think the insect noises came from katydids or bush crickets. You can hear them most clearly ~7:38.

Moths flew around during totality, thinking it was night time. They quickly disappeared when the sun came back.

Luna the cat did not seem to display any change in behavior.