When our eye sees something, it sends a message to the brain to make sense of the image. The brain keeps that image for about 1/10 to 1/30th of a second. That doesn't seem like very long, but it makes a big difference in how we process the world around us.
If our brains didn't keep images, we would see darkness every time we blink. Because our brains do keep the image, even for a very short time, we don't even notice a disruption in or vision.
Movies and TVs take advantage of the way our vision works. When we go to the movies, the film shows a new frame every 1/24th of a second. Even though there are disruptions in the image, our brains retain the image of each frame until the next frame is shown. This gives us the illusion of continuous, smooth motion.
Vision Science Experiment
We can create an experiment of our own that helps to show how the brain keeps images and how it affects the way we see the world around us. You will just need to collect a few items from around the house.
- card stock or this card board
- pencil or pen
- scissors
- hole punch
- ruler
- string
Draw or trace a circle on the card stock approximately 4 inches in diameter.
Cut the circle out with the scissors. Then, draw a fish bowl on one side of the circle and a fish on the opposite side.
Cut 2 lengths of string 24 inches long. Thread a string through the holes on each side of the circle. Next, hold the strings and twirl the circle around so that the strings are twisted together on each side of the circle. One person can do this, but sometimes it's easier to have one person hold the strings and another person twirl the circle. Start with 25 or 30 twists.
Pull the twisted strings straight out to the sides so that the circle spins. What do you see? If you have twisted the strings tight enough, you should see the fish appear to be in the bowl. If you do not see this, try twisting your string more.
Vision Science Explained
When the circle spins around, the eye sees both images. The brain retains the first image for a fraction of a second. This is long enough for the eye to see the second image. This causes the two images to overlap in the brain and the fish appears to be in the bowl.
Did you see the images overlap? If not, twist the strings tighter so that they will spin faster when you pull the strings. How many twists did it take?
The retaining of images in the brain makes this experiment work just like movie film works to make individual frames appear to be continuous motion. It's just one of the many wonders of our human vision!
More Science Units for Kids
- Animal Cells (Edible!) K-6th
- Animal Report Forms K-8th
- Crystals - How to Grow Crystals K-6th
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- How to Make a Lava Lamp - K-6th
- Why do Leaves Change Colors K-6th
- Homemade Battery Experiment K-6th
- Pop Rock Science Experiment K-6th
- Simple Machines – Inclined Planes
- Solar System Worksheets
- Squishy Circuits (PreK-6th)
- Weather Unit (free printable unit) K-3rd
Marci is a Christian wife, homeschool mom, science geek, softball coach, hockey mom and blogger, who needs her morning coffee, hair done and make-up on before attempting of those things. You can find her blogging at The Homeschool Scientist
