The first is in our heads. "At sunset, our eyes are daylight adapted and may even be a bit weary from the day's toil," Lynch and Livingston write. "As the light fades, we cannot adapt as fast as the sky darkens. Some hues may be lost or perceived in a manner peculiar to sunset. At sunrise, however, the night's darkness has left us with very acute night vision and every faint, minor change in the sky's color is evident." In short, you may perceive more colors at dawn than at dusk. [Red-Green & Blue-Yellow: The Stunning Colors You Can't See] - See more at: http://www.livescience.com/34065-sunrise-sunset.html#sthash.vYmyt91K.dpuf

According to the astrophysicist Neil Degrasse Tyson, director of the Hayden Planetarium in New York, there's also a trick for distinguishing a sunrise from a sunset played in reverse. Because of Earth's tilt, the sun doesn't rise or set along a vertical line, but at an angle. "When viewed from all latitudes north of the Tropic of Cancer (23.5 degrees north latitude), the sun always rises at an angle up and to the right, and sets and an angle down and to the right," Tyson writes on his website. "That's how you can spot a faked sunrise in a movie: it moves up and to the left. Filmmakers are not typically awake in the morning hours to film an actual sunrise, so they film a sunset instead, and then time-reverse it, thinking nobody will notice."

So if you see a rising sun move up and to the left, you know you're in the twilight zone. Better head back to the hospital.

Questions about the path of the Sun across the sky

Michah from Wisconsin wrote:

Astronomical twilight is defined when the sun's center is 18 degrees below the horizon, nautical twilight is at 12 degrees, and civil is at 6 degrees. According to www.weatherunderground.com, today's (January 12th) twilight times are as follows: Astronomical twilight began at 5:46 a.m. and ended at 6:20, nautical began at 6:20 and ended at 6:56, and civil began at 6:56, then sunrise was at 7:28 a.m. Since they are all segments of 6 degrees of rotation, how can the times between them be different? Additionally, if the average time it takes to travel 6 degrees is 34 minutes, and there are 60 groups of 6 degrees, it would mean that there are 2,040 minutes in a day, which isn't true, there are only 1,440. How can these things be explained?