Green Sky in the Morning

It was about 4:00 in the morning on Saturday when my cell phone sounded the alert for a possible geomagnetic storm brewing (courtesy of spaceweather.com).  Kathy and I were vacationing in Banff, Canada, and I could see some reddish clouds in the sky, nicely reflecting the town's lights.  Stars were visible, yet no auroras.  But wait -- the clouds in the northeast were silhouetted, indicating that something was lighting up the sky behind them.  Perhaps the coming dawn?  No, it was much too early for that in Banff; sunrise would not be until 8:03am.  Eventually the effect brightened and it became obvious that this was indeed an aurora -- the Northern Lights.

It did not look much like the spectacular images in the astronomy web sites -- usually taken from Alaska or other high latitude regions, without clouds in the way.  But it was the first time Kathy and I had seen them at all, so the view was amazing enough for us!

One thing you may not know is that the picture-book photographs of auroras are all time exposures -- mine was 6 seconds at f/4 with ISO 6400.  So, like for most nighttime sky views, photography enhances our ability to see and appreciate the Northern Lights.

Family, Fun, and Physics

This is my grandson John, throwing a rock into the water of Fern Ridge Lake near Eugene. We're talking a big rock, as you can see here:



Big rocks make big splashes, which fascinated John -- but not nearly as much as they fascinated me when I enlarged a portion of the 1/1500 sec shot.



So much is visible in that frozen instant of time (0.0007 sec.)!  The rock itself is continuing to push down into the water after expelling a window-thin sheet of water upward.  Through the "window glass," you can see a secondary shock wave getting sent backward.  But my favorite feature of the brief apparition is a set of concentric rings on the sheet itself, caused by water droplets striking it like pebbles dropped in a pond. (Click on the image to see this better.)

Grandson John did not need any photographic enlargements to be entertained however.  He kept it up all the way to sunset, splash after splash:



It was a glorious afternoon -- we enjoyed family, a gorgeous sunset, and Physics.