Star In A Star
Basketball
Introduction
Title: "Basketball Earth"
A Basketball court makes an ideal location to really feel the size of the solar system.
This accurate scale model will show how the Earth, Moon, and Sun will match a Basketball, a Tennis ball, and the length of the Court.
Additionally (in an interesting cosmic coincidence), at this scale, lightspeed scales to the top speed of a human 5k runner. The lightspeed concept can be introduced to more advanced audiences.
Preparation and Goals
Location
A basketball court (indoor or outdoor)
Materials and participants
- 1 Instructor
- 1 Basketball — the Earth
- 1 Tennis ball — the Moon
- 1 Moon holder (person)
- 1 Runner (person)
Distances and scale can be very abstract for people. To make this demonstration more effective, make the distances and sizes in this model more relevant to the location where the demo is happening.
A well-chosen Earth Orbit "location" will help to engage the audience and prolong the effect of the demonstration. Instead of just saying "the Earth would be 3 kilometers from the Sun," a specific place that is well-known to the audience should be chosen as the eventual place for the Earth/Moon system.
For instance, here in Croton-On-Hudson, NY the High School and Middle School have indoor basketball courts that are about 3k away from the entrance to the Croton Point Park. Most audience members will be able to visualize that place and most importantly, they are also able to go there afterwards and hold the scale model Earth and Moon.
The ability to re-experience and solidify the mental image of the scale model is (almost) the entire goal of this demonstration. The audience should be encouraged to imagine the Sun every time they enter any basketball court and to imagine carrying (or actually carry) a Basketball and Tennis ball to the Earth Orbit "location."
If there is time and equipment available to prepare this and to do a screen projection, a map can be shown after the introduction of the Earth Orbit "location" with the entire orbit superimposed on the place where the demo is happening.
Demonstration
Earth
Let's scale the Earth to the size of a basketball. Pick up the Earth, dribble it, pass it, finally... Spin it on your fingertip (may require practice). Make sure you spin it the correct direction — counterclockwise — and mention that each time the Earth spins that is a day.
Moon
If the Earth is the size of a basketball then the moon is the size of a tennis ball. The moon's orbit around the earth at this scale is twice the radius of the center circle. Someone should walk out past the center circle (maybe counting steps until the circle and then counting those same steps again) and carry the moon out to that distance. Depending on time, the Moon can do a few orbits (months) of the Earth.
Sun
The final part of this model is the Sun. If the Earth is a basketball then the Sun will be very, very large. How large is the Sun in this model? Let's bring the Sun here to the basketball court for a size comparison.
If the Sun were here, it would be a seething ball of nuclear fire with a diameter that is the length of the court. Imagine that we are at the center of that giant Sun now. If we were in the center of it, it would reach as high as the ceiling and the same depth downward underground.
It's getting kind of hot inside the Sun so let's leave it here on the court and travel (in our imagination) to the Earth Orbit "location" that is 3 kilometers away. Make sure that you note to the audience that the "location" we are going to is just to help with familiarity and that that location is just one "place" in the orbit of the Earth around the Sun.
Now we are at the remote place in our imaginations, let's look back at the Sun. Everyone knows that when you move further away from something, that thing seems to get smaller. As we move away from the model Sun, it will also appear to get smaller. From 3k away, the model sun will be "visible" glowing at the basketball court location and from this distance (if we have done our scale model correctly) the Sun model will appear to be the same size as the actual Sun in the sky.
Advanced
(The final part of this scale model demonstration is for advanced audiences who can understand the idea that light actually travels at a "speed" and it takes time for light to get from the Sun to the Earth.)
Everyone knows about Light Speed right? (if not, you could do a little intro on that)
Now, imagine that a beam of light emerges from the sun's nuclear fire and begins traveling to the Earth. Who knows how long that light takes to reach Earth from the Sun? (someone will say 8–9 minutes). Most people have heard of light years (the distance that a beam of light travels in 1 year), but the distance light travels in 1 minute is called a "light minute." So, 8 light minutes after it leaves the Sun, the light is actually going to reach Earth.
When you scale down size (like we have done with the Sun, Earth, and Moon here) distance also scales down and so does "speed." At this scale, light speed is equal to the top speed of a 5k runner. So, if we had the fastest runner in the world here in Croton run the 3k from the basketball court to the Park, he would be like a beam of light. It would take him 8 minutes to travel that distance in our scale model as it takes light to travel the real distance between Sun and Earth.
As an aside, light takes about 1.25 seconds to travel from the Moon to the Earth. The 5k runner should be able to cover that distance in 1.25 seconds. If you want someone to demonstrate this at the basketball court it might help to solidify the understanding of the much more immense distance between Sun and Earth.
Notes
The earth and moon images above are sized to scale with each other.
The sun image is not to scale with the Earth and Moon images. It would not fit on the page.
Baseball
Introduction
Title: "Pitching to Pluto"
A Baseball field and diamond makes a great, compact demonstration for an outdoor demo, but it can also be moved indoors into a gym because this model only uses the diamond and the pitcher/catcher distance.
Light speed is more of an advanced concept so this might need some background work first. You can build up to light speed by talking about things that travel faster and faster.
Preparation and Goals
Understand the immense size of the Solar system and the time it takes light to travel.
This demonstration is intentionally named to bring up Pluto and allows an introduction to the reclassification of Pluto as a Dwarf Planet.
Location
A baseball diamond (indoor or outdoor)
Materials and participants
- 1 Instructor
- Sun — 5mm ball — clay or yellow/orange playdough
- Pluto — a piece of paper with a tiny dot on it (even that is too big as Pluto is invisible at this scale)
- Jupiter — a grain of sand glued to a piece of paper or on the top of a stake
- A stake with an "image" of a beam of light mounted on it. This will be placed and moved over the course of 5 hours and 30 minutes.
Demonstration
We want to shrink the Solar System to fit the entire thing inside a baseball diamond (with the pitcher's mound hosting the Sun as the center). To do that, the Sun needs to shrink to a size of 5mm. None of the planets will be visible except maybe Jupiter and Saturn which will be the size of a grain of sand.
The planetary orbits shrink to fit to the size of the diamond.
The Sun will be the pitcher and will throw light towards home plate — however, the light will take 5 hours and 30 minutes. It might require too much patience to wait for the beam of light to reach Pluto at home plate, so the audience should return periodically to move the light marker.
Each significant moment of the travel of the pitch to Pluto can be marked. Mercury, Venus, and Earth are all passed by the light within 9 minutes. The outer planets can be indicated by a timer alarm to remind the group that the light is passing that object's orbit.
Notes
This can be a short demonstration but make sure you schedule it so that you are able to come back periodically during the 5 hours and 30 minutes. Each time you return you should move the light beam to mark the travels of the light that the Sun threw.
Variation
Instead of starting with the whole solar system in the baseball diamond, we can begin with just the Earth and Moon.
This variation on the Pitch to Pluto demonstration uses a progression of scale models starting from the Earth Moon system with Earth placed at the pitcher's mound and the Moon at home plate. At that distance the moon is a size 3 soccer ball and the Earth is a 60 cm diameter sphere (a big air-filled playground ball). If a pitch is made from Earth to Moon at this scale, a ball thrown at about 35 mph (typical kid speed) is traveling at light speed.
You can throw the light beam ball to home (Moon) to demonstrate the distance that light can travel in a bit more than one second. This can be a more immediate and visceral experience for younger audiences. They will want to throw the light beam ball over and over and this is good! It will solidify the feeling of the light having a "speed."
To take this beyond the younger set and make it more advanced you can start with Earth/Moon and then scale down the system and each time the scale model shrinks the speed has to slow down to throw ball slower and slower. This is required because in the model light stays the same speed but the "distance" represented at each scale is progressively larger. At some (early) point in the shrinking scale model someone will have to carry the light beam ball to make it slow enough.
Soccer — Rocky Runners
Introduction
Title: "Rocky Runners"
The Sun can be scaled to the size of a size 5 soccer ball. At this scale, the 4 inner, rocky planets orbit within the Soccer field width. The outer planets are further out, but this model can demonstrate the inner planets.
Preparation and Goals
Location: Soccer field
Materials: Size 5 Soccer ball
This is for a set of 4 or more energetic kids. They are going to model the full orbits of the inner planets.
Orbit distance cheat sheet to help mark out the orbits on the Soccer field. Mark at least 8 points of each orbit track ahead of time. This could be by cones or flags or rope or hula hoops dropped onto the grass.
Demonstration
Basic introduction to scale models. Basic introduction to orbits.
Give each kid a planet to be. Fastest is Mercury. Then Venus, Earth, and Mars (for long distance runner).
Notes
It would be a feat of "people engineering" if you could actually get the kids to run in the cycles that the actual planets orbit. Don't feel bad if you can't get them to do it at the right speed. The main idea is that the further out you are from the Sun the bigger your orbital path and the longer it will take you to get around for a year on your particular planet.
Soccer — Milky Way in Millimeters
Introduction
Title: "Milky Way in Millimeters"
Preparation and Goals
Location: A Soccer field — 100 meters (image above shows half a soccer field, but the galaxy should be scaled to the whole field so it is 100m x 100m).
Materials:
- Something that is 1 millimeter long to show a light year
- A meter stick to show 1000 light years
Place a small, millimeter sized object in the grass ahead of time.
Demonstration
Basic introduction to scale models. Basic introduction to the Milky Way Galaxy, its spiral shape, the arms, the Solar System, the location of the Solar System in the Galaxy, Earth.
Milky Way galaxy scale model in half of a soccer field.
100,000 ly across, the Milky Way galaxy scaled to 1 mm per light year fits in a soccer field.
Go to a large field like a soccer field.
Lead kids to a spot near where the solar system would be (talk about the black hole at the center that is like a toilet bowl flushing, talk about how the Solar System and the Earth is away from the black hole at the center, far out on one of the spiral arms), then focus on the ground, looking for a millimeter-sized object that was placed there ahead of time.
If you cut that millimeter into about 1,000 parts (365 days x 24 hours = 8760 light hours in a light year, the entire solar system is 10 light hours in diameter measured to the orbit of Pluto, so 876 parts to be exact) one of those 1000 parts of the millimeter (a micrometer, smaller than a red blood cell — a human hair is 40 micrometers wide, so 1/40th of the width of a human hair) is the size of the entire solar system.
The earth's orbit is about 1/40th of the size of the solar system (measured by Pluto's orbit) which at this scale is 40 nanometers. In other words, earth's orbit is 1/40th of 1/40th the width of a human hair — about the size of a virus.
And the earth itself is about 1/10,000th of its orbit radius (which would make the earth in this model 4 picometers — about 6x smaller than a hydrogen atom). For comparison to one of the smallest "things" there is, 25 picometers is the size of the smallest atom Hydrogen... at this scale earth would be about 6x smaller than the smallest atom!
Notes
The toilet bowl metaphor is useful because even though it's not exactly accurate, it's pretty funny to think about.
Track
Introduction
Planets race around the track at different speeds (and different distances from the Sun).
Notes
This is similar to the Soccer field demo.
Swimming
Introduction
Title: "Swimming in Stars"
Imagine the Sun is the size of a grain of sand. Imagine that other stars are grains of sand that fill a swimming pool. Imagine the distances between them. Galaxies are groupings of stars. The universe is filled with galaxies.
Preparation and Goals
A small source of sand where you know the approximate number of grains.
Demonstration
Notes
To keep the swimming theme, you can compare swimming to flying and moving freely in 3 dimensions. This can be helpful to bring to light the fact that stars and galaxies are all around us.
© 2016 Daniel Cummings — All Rights Reserved