Twilight happens twice a day when the sun is just below the horizon, and the sky is filled with a soft glow of light. As the light changes, so does our eye’s ability to see color.
The retina of your eye has rods and cones. The cones allow us to see color during bright daylight and read the words on a page. The rods make it possible for us to see at night, but they can’t distinguish color or make out the words on a page.
You can do a fun activity with your family to help you notice that shift from using the cones to using the rods. You’ll want to stay outside from sunset until it gets completely dark. Here are some things you can do to prepare for the activity:
- Find out when sunset is expected in advance so you’ll be outside in time.
- If you want snacks or beverages, prepare them beforehand and bring them outside.
- Take a book or newspaper out with you to test your ability to read as you go along.
- Take a printout of the chart below and a pen or pencil.
- Have blankets or bug spray on hand, so you don’t have to run back inside the house.
- Turn off exterior lights, so they don’t interfere with your experiment.
- Set up a comfortable space so you can relax.
- Invite friends and family to join you for a time of relaxed conversation.
Use the chart below to note the changes in your eyesight as twilight progresses. In early twilight, you’ll still be able to easily see bright colors in the sky and on the ground. Record what time colors begin to fade and when it becomes difficult to read. You can also jot down the time you see the first stars, then when you notice the sky is starry with just a patch of twilight glowing on the sunset horizon. You can end by recording the time when twilight is gone, and it’s dark outside.
Click on the chart below to download it as a PDF for printing. There are enough slots for you to try this activity several times over the span of weeks to note the differences in time.