The Fascinating Science Behind Sunrise and Sunset: Exploring the Different Phases of Twilight

The sky comes alive during sunrise and sunset, but what happens before and after these natural wonders? Morning Edition co-hosts Jeremy Siegel and Paris Alston recently spoke with GBH meteorologist Dave Epstein about the fascinating science behind these beautiful displays of nature.

During civil twilight, which occurs just before sunrise and after sunset, the sun is positioned zero to six degrees below the horizon. This is a favorite time of day for many people because it provides light without the sun being visible. Sunrises and sunsets during civil twilight can be absolutely breathtaking, occurring approximately 30 minutes before sunrise or 30 minutes after sunset.

Nautical twilight follows civil twilight and takes place when the sun is six to 12 degrees below the horizon. During this time, the brightest planets and stars become visible. Animals are also more active during nautical twilight, making it known as “coyote time” due to increased activity of crepuscular animals like deer that can sometimes lead to accidents with cars.

Finally, astronomical twilight occurs when the sun is between 12 and 18 degrees below the horizon. This is a time when faint objects like the Milky Way can be observed, but it is not considered nighttime yet. In summer months like June, astronomical twilight occurs very early and late in northern New England where true nighttime may not begin until late evening, making astronomical twilight in early morning hours.

Understanding these different phases of twilight enhances our appreciation for the beauty of sunrises and