Solar System scale activity
In 2014-04, I was asked by Sagamore second grade teacher Ms. Quinn to help do something for the first grade and kindergarteners on Sagamore Space Day. I'd like to do what I proposed back in January, of imagining the real scale of the solor system, riffing off of, "How Big is the Solar System? | It's Okay to be Smart | PBS Digital Studios - YouTube".
I'm using an online solar system scale calculator to see what our solar system model can look like. Although the video serves science education by using metric units, I wonder if we should use US customary units instead? Using the scale chosen in the video, 1,264,000,000:1 (calculated from the video's stated 110 cm (4.3 inch) grapefruit = 1.39 million kilometer sun)!, we can comfortably get out to Saturn at 370′. A 5.5′ sun gets us Saturn at 470′ (the length of our field) and a scale of 1,600,200,000:1 , but I think I'll stick with their scale because they give us good size references (e.g. Mercury is only the width of just 4 human hairs).
| What | Diameter | Orbit Radius (feet) | Difference from Prior (feet) |
|---|---|---|---|
| Sun | Grapefruit (4.3″) | ||
| Mercury | 4 hair widths (0.0151″) | 15 | |
| Venus | 10 sheets of paper thick (0.0376″) | 28 | 13 |
| Earth | 1 millimeter (0.0396″) | 39 | 11 |
| Moon | ¼ Earth | 1 | |
| Mars | ½ the size of Earth (½mm) (0.021″) | 59 | 20 |
| Jupiter | Almost half-inch (0.4448″) | 202 | 143 |
| Saturn | Hieght of Lego brick (0.3622″) | 370 | 168 |
| Uranus | 0.146″ | 744 | 374 |
| Neptune | 0.1413″ | 1,167 | 423 |
| Voyager spacecraft (farthest man-made object) |
4,590 (0.87 miles) | ||
| Betelgeuse (Red giant star) |
135′ | ||
| Sirius B (White dwarf star) |
0.0433″ |
| What | Distance from Sun (miles) |
|---|---|
| Alpha Centauri (Nearest star) |
2,000 |
| Galactic center (Center of Milky Way) |
12,873,222 |
| What | Quantity |
|---|---|
| Light Speed | 1 inch per second |
| Light Year | 465 miles |
| Width of Milky Way | 100-120 thousand light years |
Fastest manmade object is the Juno spacecraft sent to study Jupiter as it uses Earth's gravity as a slingshot it will reach 25 miles per second. A bullet's speed is ½ mile per second and light's speed 186,000 miles per second.
Activity
I imagine taking kids out to the field, starting in the eastern corner, and explaining the concept of scale. Out comes the (grapefruit?) Sun and they collect some nearby pebbles and sand. Invite them to choose the right size objects and place them around the Sun, at the same kind of distance the planets really are from the Sun (to scale).
Establish a foot by measuring the leaders foot and deciding how they'll walk to measure out feet.
The leader will have stiff flags with the scale planets attached and labeled.
Each planet's distance from the Sun is shared, and the group counts out he paces. The true model planet is revealed and its flag planted, a factoid is shared; imaginations are challenged. Repeat up to the Earth, then fast-forward to Saturn (when we run out of space).
I know it might be hard to keep all kids engaged. But, it's outside, they get to run around a bit and count out paces, and I think seeing how tiny the planets actually are and how far away everything is, can impart a real impression of the reality of space.
Materials
- Grapefruit or other 4.3″ Sun like object
- 1 foot ruler
- A 'globe from the Sagamore Science Lab
- (6) Small, stiff, flags, labeled and scale planets attached
- Nearby rocks & sand (for planets)
Script
Do you all know what the solar system is? [discussion] How about the size of planets and where they are in the solar system? [discussion]
Well, what we're going to do is make an acurate model of that by scaling the solar system down so that most of it fit here on the field here. How much do you think we have to shrink the real solar system down so that it fits on this field? [discussion]
We're going to make a solar system here that's 1¼ billion times smaller!
Now we might be able to imagine half, right? If something was as long as you can stretch your arms out [everyone stretch arms], how big would half that be? How about one tenth? [play with arm scales] So that's ten times smaller; how about one hundred times smaller? One hundred is ten tens. So, in the tenth you measured out, show me one tenth of that. That's a hundred times smaller the width of your arms. Could you imagine doing a tenth of that?! That would be one thousand times smaller the width of your arms. One thousand times smaller is doing ten times smaller three times.
Well, to get to the over a billion times smaller we'll be using for our solar system model here, we need to shrink the real solar system a thousand times smaller, and then another thousand times samller, then another thousand times smaller than that!
At that scale, the Sun… anyone know how big the Sun is? [discussion] Our model Sun will be the size of this (grapefuit)! That means the real sun 1¼ billion times bigger than this in real life! I'm going to put our sun right here on the ground. It's the first thing in our model of our solor system!
What should we put out next? [Mercury!]
Now, everyone go grab some rocks and sand over there that we can use for Mercury and the other planets. [kids grab nearby rocks & sand]
Everyone choose something they think is the right size for Mercury compared to our sun here, and stand how far away from our sun you think Mercury should be as it orbits around the Sun.
Okay, Mercury should be 15′ away from the sun in our shrunk down solar system.
How big is a foot? [get out the foot, compare it to the leader's feet, see how the leader has to step to step out a foot at at time]
Okay, let's count out 15′. [everyone follow along as the leader steps out 15′]
And how about its size? Mercury is actually so small at this scale, that I have to use the four hairs taped to this flag to imagine its size. You know how thick a hair is? Well, our Mercury is only four hair thicknesses wide!
Which planet is next? [Venus!] Okay, let's do the same thing, see if you can find something that might be the right size for Venus and walk out to where you think it should orbit the sun.
Do you see how thick this 10 sheets of paper is? That's how big Venus should be! And we have to walk out 13 more feet away from Mercury, to place it where it should be. [every counts out the steps, then the flag for Venus is planted]
Which planet is next? [Earth!] Let's find something the size of Earth, and walk to where you think it goes.
I'm going to count 11 more feet from Venus, that's 39 feet from the Sun. Wow, look how far away from the sun we are! And here's our Earth, 1 millimeter wide! (Use pepper corn, larg salt crystal, ?) Look how far away the sun is and how small it looks! That's why the humongous Sun doesn't look humongous in the sky—it's so far away! And look again how tiny the earth is compared to the sun and the empty space all around.
Here's another model of the Earth [pass around a globe]. Can you find where we are on there? And just think how long it takes to travel on that globe. Like if you went to Disney World, which is here, it's only that far away from Atlanta on the globe, but it takes a long time to get there! Hours to flay at jet speeds, even many more hours to drive. And that's just to go from here to here. What if you wanted to get to China?
Now shrink this Earth (the globe) down to this Earth size (the model solar system Earth). It still takes just as long to travel around the Earth, but imagine instead of moving around a little bit on this tiny Earth, you wanted to go to Mars. Just think how long that would take!
Perhaps the follow discussion of the speed of light should be left out?
But what if we just went a lot faster? Really, really fast? Then it wouldn't take too long, right? [discuss]] But guess what? We can't go as fast as we want—there's actually a cosmic speed limit! Know what the go the fastest? Light! Light is the fastest thing in the universe, it's impossible for anything to go faster. And crazy things happen when you try to go as fast as light. You know what happens? You get heavier! It's not some cosmic policeman who says, "hey, slow it down, there's no going faster than light around here!" It's because as you go faster you actually get heavier, so it takes more to make you go faster. It's eaier to make a marble go faster than to make a bowling ball go faster, right?). You get heavier, so it takes more to go faster, but even if you go faster, you get heavier again, so it takes even more to go faster again. And watch out, if you get too heavy, you turn into a black hole and swallow everything up! So no going as fast as the fastest thing in the universe, light! So how can light go as fast as it does? Because it starts out not weighing anything, so it never gets heavier!
And how fast is light? Here on Earth, light seem super fast, faster than you can imagine. Turn on a light, and instantly you see a room light up; you don't see the middle of the room—light where the light is—light up first, and then more of the room, and then finally the corners. No, it seems that the light form the light lights up the room all at once. But space is so huge, that even super speedy light seems slow.
In our model solar system here, light travels about one inch per second! See if you can move one inch per second. Remember, an inch is only this big, and a second is the time it takes to say, "one one thousand", so it's about this fast. [show and play with the speed of light]
Any guesses how far away on our solar system here, to the next closest star? It's 2,000 miles away! And remember, that's in our over 1 billion times smaller model here, not for real. For real, the light from the star closest to our sun takes over 4 years to reach our eyes! In other words, if you left our model Earth here, traveling at the speed of light—remember that's 1 inche per second in our model here—you'd have to walk for over 4 years at that speed to travel the 2,000 miles to the next closest star.
And here's some other fun things about stars. If one of the biggest stars were where our Sun is here, we would actually be standing inside of it! It would be all around here, it's surface being somewhere out there! But the smallest stars are only a little bigger than the Earth!
And you know you can see a lot of stars out in the night sky. All of those stars you can see are in our Milky Way galaxy—and we don't even see all the stars in the Milky Way. Our solar system is around the edge of the Milky Way galaxy, and if you wanted to travel to the middle of our galaxy, you'd have to go almost 13 million miles away in our model!
With telescopes we can see billions of galaxies that are far away from us. Just think how big the universe is! How many stars! How many planets!
I hope you guys learned some things today. Now you know that pictures you see of the solar system aren't exactly right because the planets of the soloar system would be too small to see!
Okay, I've planted flags with more planets out that way, and you can travel (run) to Mars and Jupiter and Saturn, but after that we run out of room! Uranus and Neptune are even farther away!
Have fun flying around the solar system!