Speed of Sunrise


Recently, I was in the parking garage at my work, in my car and starting to get out to start my workday. I saw the sun start to peak over (from my point of view) the cement floor of the garage and I started to record. I recorded the sunrise for 4min until I got a little bored.

I thought it was cool that when I fast forwarded the video, I could see the sun move pretty well (try it). I wondered, just how fast is it moving?

It is obvious(?) that from our point of view, the sun travels 360 degrees in 24 hours, so it goes 15 degrees per hour (360/24).

At 40 degrees latitude (look up your own latitude), one degree of longitude is about 53 miles, so the sun travels at about 795 miles per hour (15*53) while you're watching it during a sunrise.

The calculation is, length of path(miles)/time(hrs) = mph. For this problem, this becomes (circumference of Earth in miles adjusted for latitude)/(24hrs) = 2pi*(radius of Earth in miles)*cos(40 degrees)/(24hrs) = 2pi*(3,959 miles)*cos(40 degrees)/(24hrs) ~ 795mph.

So now you know.

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