Night Hike I: Vision

From the day we arrive on the planet
And blinking, step into the sun
There's more to be seen than can ever be seen
More to do than can ever be done

—Elton John, “Circle of Life”

But, Elton, what about when the sun goes down?! Join us as we begin to explore all the things we might miss if we don't embrace the dark. The evening shall be glorious!

"Vision" Quest Night Hike

Let's Get Started!

Hi, everyone! Welcome to Nuhop’s At-Home Outdoor Education! Your instructors for tonight's adventure will be Bumble Bee, Dingo, Geode, and Mountain, and we are looking forward to showing you Nuhop at night!

Tonight's specialty night hike? Vision Quest! While our Vision Quest is not a coming-of-age ritual, we are embarking on an endeavor to learn more about how people and animals see in the dark! Let's get started just before sunset—which happens at a slightly different time every night, so plan ahead by checking Time And Date.

We’ll guide you through some vision-based activities that we love to do with our students. Just like Micro Hike, you can use your own backyard for this close-range adventure - but you’ll take it on in a whole new "Light."

Materials Checklist

Here's a checklist to help you make sure you'll have the all materials you will need.

Tree Tracing - Step One

What’s Happening?

This activity will demonstrate how human eyes perform under different levels of light. You will briefly take a look at the subject of your case study (eg. a tree, a shrub, a house, or a skyscraper) at three different times in the evening. We will start about 30 minutes before sunset. Finally, the next day, you will observe it a fourth time in daylight.

What Should I Know Before I Start?

  • Tree tracing is a unique activity: you don’t do it all at once; you take plenty of time between each step.

  • It’s best to start 30 minutes before sunset.

  • Helpful hint: on Tuesday, the 5th of May, the sun will set at 8:31PM here in Ohio. On that day, 8:00PM will be a good time to start. As spring progresses, a later start time will be practical. In June and early July, the sun won’t set until around 9:00PM. Starting on the 4th of July, the sunset will slowly come earlier each day. No matter where you are in the world, you can use https://www.timeanddate.com/.

Materials

You may want a timer. Later in this activity, you’ll need something to draw on and something to draw with.

How Do I Start?

Check out Bumble Bee's video below! Visually follow your subject from its tallest point all the way down to where it reaches the ground or becomes completely blocked from view by another building or plant, noticing as many details about shapes and color as you can.

Good job with the first step of tree tracing! What time is it? Plan to come back in 30 minutes for step two when you’ll observe your subject at sunset. You might want to set a timer. In the meantime, check out the Paper Shapes activity!

Paper Shapes Experiment

What’s Happening?

This experiment demonstrates how humans see shapes and color in the dark. It works best in a dimly lit room or outside after dark.

Materials

You’ll need markers, scissors, and a couple of sheets of paper. If you like to be precise you can use a ruler, compass, protractor, or stencil kit! Depending on what you have at home, you could use one marker and different colors of paper—or white paper with markers of different colors. If you have a printer and you prefer drawing digitally, you could print your shapes.

Making the Tools

You will need to make five different paper shapes in five different colors. Maybe pick a few shapes that are really similar and one or two that are quite different. All of your shapes should be two-dimensional and about the same size. You are going to be testing someone at home, so don’t let anyone see what colors you use for which shapes!

Consider making similar shapes—like your heptagon and your octagon—similar colors for a more advanced challenge! You can trace these images if you’d like; if you’re tracing them by putting a piece of paper against your screen, use a marker which you’re certain won’t bleed through the paper...and be very gentle.

How to Run the Experiment

  1. First, test your own ability to see color in the dark. Bring your cut-out, colored shapes to a dimly lit room. Let your eyes adjust for a moment if you like. Look at the shapes, one at a time, and see if you can tell what color they are. If you remember the color you chose, for a shape, is this how you expected it to look? How similar is it to the color you were looking at in regular light?

  2. After looking at each one, compare them side-by-side. How easy or difficult is it to tell the colors apart? Why do you think this is?

  3. Now test someone else’s dark vision and color vision. Without turning on the lights or opening the curtains back up, invite a family member into the room with you. While you give them a moment for their eyes to adjust, tell them how you started your tree tracing project and explain that now you’re testing color vision in the dark. Hold up one shape at a time and have the person try to guess the color of each of your shapes. See if they know what the name is for a seven-sided shape! (Heptagon.) When you’ve shown them each one, spread them out next to each other. Ask how the colors look now, and whether they can tell any of the colors apart.

  4. Turn on the lights or open the curtain to see how many colors you each guessed correctly.

Explanation

  • Most people have a hard time telling colors apart in the dark. We have cells in a part of our eyes called our retina that specialize in particular jobs. Cone cells help us see color—as long as they have enough light. Rod cells help us see light, shadow, and shapes.

  • Invite your family to watch Colm Kelleher's TED video together. Where do you think he might be from? What device does he tell us takes advantage of the three types of cone cell?

  • Keep an eye on the clock or your timer. What time is it? How long until you return to your tree tracing case study?

Tree Tracing - Step Two

What's Happening?

Half an hour after you first visually traced your tree, shrub, or building, you’ll return to the same spot to observe how it looks at sunset.

Materials

Your timer, if you want it

How Does Step Two Work?

Look closely at the tallest part of your subject. Notice its shapes and proportions. Visually follow it to the lowest point you can see.
Drink in the details and compare what you see now to what you saw earlier. Were all of the details as clear as the first time you looked? Did anything look fuzzier? Did anything appear to glow in the sunset? Was anything reflecting the light differently?

What’s Next?

Nicely done; you’re finished with step two! What time is it now? Plan to come back again in half an hour. Set a timer if you’d like. While you wait for the sun to go down further and the light to become grey, we dare you to try...the Headless Horseman illusion!

The Headless Horseman Illusion

What’s Happening?

You’ll experience an optical illusion by yourself or with a partner! This works best about 30 minutes after sunset.

Materials

If you perform this illusion by yourself, you’ll need to go outside and find an object such as a stop sign, potted plant, or bird feeder.

How Can I Perform the Headless Horseman Illusion?

  • For solo players: Go outside to choose a medium-sized object. Maybe it’s a mailbox or a birdhouse. Stand about 15 steps away and stare at it. Don’t blink—stare it down! Keeping your head still, slowly walk toward your object. It will seem to disappear! While keeping the rest of your body still, move your eyes to look away, and the object will reappear.

  • For partners playing together: Stand at opposite ends of your porch or backyard. Stare into each other’s faces without blinking, and, keeping your heads still, slowly walk toward one another. Your partner’s head should begin to disappear! When the illusion is working for both you and your partner, stand still and, without moving your head, look from side to side. Your partner’s head will reappear!

Explanation

A couple of factors are at play here. Remember the cone cells and rod cells Colm Kelleher discussed? Your cones respond to color and they’re most densely concentrated near the center of the back of your eye, but they need light to work. When you looked from side to side, your rod cells got to work. Rods are located throughout most of your retina and give you peripheral vision—and, remember, rods allow you to see shapes and shadows. This video explains how humans also have a blind spot at the center of the backs of our eyes which can be used for similar optical illusions. Watch until 3:46.

Human Eyesight is Only One Example...

How do Animals See in the Dark?

You’ve explored some of the ways human eyes adjust to fading light and some of our visual limitations in the dark. But what about animals? Some species have adapted their sight over many generations in very specific ways. What do Anna Stöckl and Pen-Pen Chen have to say about animals' night vision?

  • What food would our eyes resemble if our eyes had the same size proportions as a tarsier monkey's?

  • Which animal inspired headlight design?

  • If you could see the world through the eyes of one of these animals for one night, which animal would you pick?

Tree Tracing - Step Three

What's Happening?

You’ll make another observation of your subject now that it’s mostly dark. You’ll draw what you see to demonstrate how vision changes in the dark.

Materials

A pencil or marker along with a sketchpad or notebook

How Does Step Three Work?

You guessed it: now that the sun is down and the light is going grey, you’ll visually trace your chosen building, tree, or bush from top to bottom. But this time, draw what you see! Five minutes will be plenty of time. Sketch your subject from top to bottom. Include as much detail as you can see. Notice how much detail is disguised by the darkness. What do you think your rod cells are doing right now? How about your cone cells?

What’s Next?

Congratulations! You’ve hit the pinnacle of Tree Tracing. Put your drawing where you can get to it easily tomorrow. In the daylight, come back to check out your results! Before you go, we have one last insight into night vision for you: stories by candlelight!

Stories by Candlelight and Why Pirates Wear Eye Patches

Now, thanks to Mountain, we'll explore a beautiful example of how human night vision works. Grab a flashlight or get help from an adult to light a candle. You'll want to find a dark spot to get comfortable, outside if you can, and enjoy the story of Uite, the young boy who must deal with his fear of the night before he can become a great hunter.

What can you see in the darkness? Did anything around you appear closer than you thought it was before listening to the stories? Do things appear to glow? If yes, then what color? Different people see different colors of glow. Surroundings glow pink for Geode. Some people have seen surroundings glow purple or blue. One student saw a green glow.

Science or a Crazy Old Pirate's Tale?

In this Khan Academy video, you can see what happens when a rod cell sees light and its rhodopsin protein molecules respond. This is what happened in our eye that stared at the candle. What happened in our covered eyes was the reverse process. Watch until 5:34.

Your covered eye is exposed to deeper darkness than the eye that stares at the candle. Your uncovered eye becomes accustomed to the bright light of the candle flame, so it is overwhelmed with darkness when the candle goes out. Meanwhile, the rod cells in your covered eye had spent their time in the darkness by gradually changing (bending) the shape of their rhodopsin protein molecules. This change in shape at the molecular level allows the rhodopsin—and your rod cells in general—to become extra sensitive to light. The darkness made by your hand was greater than the darkness in your general environment, so your rod cells had become super sensitive to the small amount of light that was suddenly available to them—voila! You could see very well with one eye!

What's all this about Pirates and Eye Patches?

I know you are dying to ask. Don't worry, we didn't forget. When you see pirates depicted with an eye patch it is easy to assume that they wear that patch because they are missing an eye or had some sort of dreadful accident with their hook. A more plausible explanation has to do with the experiment you just did. Many years ago it wasn't possible to have electric lights on a ship sailing the oceans. When sailors (and pirates) would go below decks into their cabins or into the cargo hold of a ship, it would be very dark, maybe only lit with a few candles or lamps. And of course during the day the sun would shine brightly on the top deck. Moving back and forth between the bright top deck and the dark below deck would make it difficult to see or would take a long time as they let their eyes adjust. So, many sailors solved this problem by keeping one eye in the dark at all times. If they needed to go below deck, into the dark, they would switch their eye patch to the other eye or just remove it and they'd be able to see much better in the dark. When going back to the top decks, they put the patch back on to keep the rhodopsin charged up in one eye.

Now you know!

Tree Tracing - Step Four (the next day)

The next day, bring your drawing with you to make your fourth and final observation of your subject.

How Does Step Four Work?

Make sure you have plenty of daylight. Grab your drawing and head out to the same spot you used last night. Think back to your different observations: before sunset, at sunset, and at dusk. Recall how the shapes and colors may have slowly gotten hazier, begun to glow, or may have even melted away from one visit to the next. Notice how in the daylight, you can see as much detail as you could when the sun was beginning to set. Humans are diurnal (active in the daytime,) so our eyes are adapted to take advantage of sunlight. Compare your drawing to your subject. Last night, did your building seem to overlap with other parts of the skyline? Did your tree appear to have branches that actually belonged to a neighboring tree? What other details now seem different?

Wrap-Up

Thanks for returning to this lesson! You can test your knowledge in the quiz below, and feel free to scroll up, review, and reflect at any time. We look forward to learning with you again soon. Perhaps you'd like to head back to the home page and choose another lesson! If you liked this one, you might also enjoy Light and Sound, Nature as Poetic Muse, Nature Sketching Field Trip, Micro Hike, Backyard Phenology, or Night Hike II: Sounds in the Night!

From all of us here at Nuhop: have fun, stay safe, and get outside!