Give Now  »

Noon Edition

Sunrise, Sunset

An image of a sunrise, clouds, and Haleakal, Maui

Has it ever seemed to you like sunsets take longer than sunrise? On a basic level, it shouldn't feel right. Why or how could that be possible?

Equal To Or Greater Than

One reason for this perception? The way your eyes perceive light is different at the end of the day versus the start of the day. Human eyes adapted to daylight, may have a harder time perceiving the changes in light as the day fades into the night.

Another reason is in the morning, the air is clearer and cooler than it is in the evening. That means light doesn't scatter as much. At dawn, the sun has to be pretty close to the horizon before it starts lighting up the sky.

At sunset, the lowest mile or so of the atmosphere is filled with things like vehicle exhaust, dust, smoke, and water vapor, and all these pollutants scatter light. This means that at dusk, the sun can dip farther below the horizon before we stop seeing all the light. Then, at night, the pollutants get a chance to disperse, and the whole cycle begins again.

On the bright side (pun thoroughly intended), this effect is much less noticeable in the winter, when dust and haze stay closer to the ground.

Sources And Further Reading:

Support For Indiana Public Media Comes From

About A Moment of Science