Discovering the Science Behind Twilight: From Sunrise to Astronomical Night

Sunrises and sunsets are two of the most beautiful times of the day, when the sky is painted with shades of pinks and oranges. But what happens before and after these stunning moments? GBH meteorologist Dave Epstein recently shared insights with Morning Edition co-hosts Jeremy Siegel and Paris Alston about the science behind these natural wonders.

According to Epstein, sunrise is the moment when the center disk of the sun rises above the horizon, while sunset is when it moves below. Civil twilight occurs just before sunrise and after sunset when the sun is situated zero to six degrees below the horizon. This period provides light without the sun being visible, making it a favorite time of day for many people. Sunrises and sunsets during civil twilight can be absolutely breathtaking, occurring approximately 30 minutes before sunrise or 30 minutes after sunset.

After civil twilight comes nautical twilight, which takes place when the sun is six to 12 degrees below the horizon. During this time, brightest planets and stars become visible, and animals become more active. Epstein humorously refers to it as “coyote time” due to increased activity by 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 period allows faint objects like Milky Way galaxy can be observed but it’s not considered nighttime yet. In summer months like June, astronomical twilight occurs very early in late morning hours resulting in short nights in northern New England where true nighttime may not begin until late evening or even midnight in some cases.

Understanding these different phases of twilight helps us appreciate their beauty and gives us insight into natural phenomena that happen before and after those magical moments of nature’s artistry on display for all to see