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Nature at Night - The Eyes
Good evening Naturalists!
Welcome to week three of ONSC Online! We hope that you have been enjoying the last couple of weeks of science. For our third week, we're going to be looking at the intrigue of what happens in nature after it gets dark!
Very quickly, we have a lot of hands-on activities this week, and it is important to set you up for success with them, so here's a few tips from our ONSC Teacher-Naturalists:
Most of these activities require your eyes to be adjusted to the dark. Because of the way our eyes work, it takes about 5 minutes in the dark to get about half of your maximum night vision, and about 40 more for the best night vision. This can be a great time to sit with a family member and tell (non-scary) stories!
This time will need to be spent in a place without direct lights, and as little extra light as possible. If you live in the country-side without street lamps, your porch or lawn might be an option, and if not, a dark room in your house will work for most of these activities!
If being in the dark makes you nervous, that's okay! Everyone has something that makes them nervous, and this gives you a chance to be brave! When we have students that come out to ONSC, we like to tell them that activities like these can be used to celebrate bravery. To us, bravery means doing something even though it makes us nervous.
If you go outside at all for these activities, make sure that you have a parent or guardian with you (or at least get their permission), and only do so if you are in a place where it is safe to be outside. Also, please make sure to follow local rules!
For tonight's activities, let's start by thinking about how we view the world around us. What senses do we use to discover our planet? Which ones do we use the most during the day? The least? Write those down. Now, make a second list of what senses are used most at night. How do the lists change?
These lists change because our bodies are adapted to be awake during daylight hours; we are diurnal. In the evening, when light levels get lower, our bodies react to help us see a bit better, but not perfectly.
To see this for yourself, you will want to find a dark place. All you will need for these activities are:
A small light (like a flashlight)
Some crayons, colored pencils, or markers
A piece of paper.
Before we begin this activity, listen to this story to get some background information, and read the information about the activities.
Once your eyes have adjusted to the dark, take out those art supplies and pick one at random. Without looking at the label, draw a line on your scrap paper. What color is the line? Write your best guess next to it. Do this for several other colors, then put those items away for right now.
The next test of your eyesight is to stand facing your buddy so that you can see their face in the dark, and take steps back one at a time until you notice something different. Keep your eyes on your buddy's face. If you do not have a buddy, you can choose an object to look at instead, but it is important that you start fairly close to that object. The 6'0” “social distancing” distance should work. What do you notice?
Now, go ahead and cover one eye and close it tight, as tight as you can. Shine the light in the other eye for several seconds, then turn the light off. Open each eye individually and see if you can notice the difference like a pirate would! (This activity has the most noticeable difference if you wait longer)
To recap for those of you that want a quick reminder before you begin:
Colors on Paper
Stepping Back in the Dark
“Wearing an Eye Patch”
What happened, and why?
To answer those questions, we need to take a closer look at our eyes themselves. Our eyes are complex organs in our body that allow us to see even as light levels change. One of the ways they do this is by having different types of cells that specialize in seeing in different conditions. Today, we will talk about rod and cone cells. Rods allow us to see in low amounts of light, while cones allow us to see in higher light levels as well as see color. Which ones do you think are more active at night? Why do you think that?
The first experiment allowed us to see just how much the darkness affects our cones. The second one allows us to see where most of our rods and our cones are located within our eye. If done correctly, you may have noticed that your buddy's head disappeared! This happens because there are a lot of cones (and few to no rods) in a very small space in the exact middle of our vision. When the cones shut off in low-light conditions, anything in that small space cannot be seen by the eyes, forming a “blind spot”. I have no doubt that many creepy legends of headless creatures comes from this fault in our vision!
Any light that hits the multi-colored area labeled “cones” will not be seen by the eyes in the dark when the cones are turned off, giving us a “blind spot'.
For our pirate story, we discovered that our eyes change very quickly when exposed to light. That is because once our light conditions get lower, our eyes begin producing a chemical called rhodopsin (roh-dop-sin), which allows our rods to become more active. This chemical is photosensitive, meaning that it is sensitive to light. It takes quite a while for your eyes to produce enough of it to get your best night vision, and even a quick flash of light can destroy it! This is why you may have noticed your eyes hurting when you turn on a bright light at night, or when you leave a movie theater.
For our last activity of the day, you can try making light art. This will require at least two people, a flashlight or other bright light that you can move around, and a camera or other device that can take pictures. This activity also requires space to move your arms, so larger spaces work better. You can try writing your name, or drawing simple shapes!
If you're proud of your art and want to show it off, feel free to send it to us at firstname.lastname@example.org and we may feature it on this page on Friday! Also, this is a reminder that we will be hosting our third “Find-out Friday”, but at a different time! We will be starting at 8:00PM to watch night fall on the Science Center and hopefully call in some owls!
If you enjoyed watching today's lessons and would like to purchase one of our ONSC Virtual Merchandise Packages, which includes an ONSC Program T-shirt and field journal, click to go to our Online Store.
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April 16, April 30, May 14 & May 28