Imagine holding an automobile in your hand. It’s easy, just pick up a matchbox car. Matchbox cars have lots of features of a real car, just shrunk down. Scientists call this a “scale model.” Model because it is not a real car, and scale because all the parts are shrunk down by the same amount. A Matchbox car is scaled by about 1:64, meaning a real car is 64 times bigger than the toy.
A Barbie doll is also a scale model, but it can’t fit in the matchbox car because it is scaled differently. Barbie dolls are scaled by about 1:6. A real girl is about 6 times bigger than the doll. Barbie is over 10 times bigger than the matchbox car. For Barbie to drive a Matchbox car, the car would have to be about the size of a football, or she would have to be shrunk down to the size of penny.
Thinking like a scientist means trying to describe reality to make future predictions. A very effective way to do this is by using models. They help scientists understand things that are too humungously big (or small) or too freakazoidically far away to make sense of. But remember, for a model to make sense all objects in the model must be at the same scale. Barbies and Matchbox cars are both scale models, just not to the same scale.
Models are often mathematical, but can also be made of die-cast metal and plastic. The more accurate the model and the more closely it describes reality, the better. Some toy cars just roll. Others have working doors and make noise.
Consider our solar system: Our nearest star, the Sun, is big. Really big. 865,000 miles wide. 110 times wider than the Earth. But what does that mean? Let’s build a model.
Imagine the Sun was scaled down to the size of a basketball, how big would the Earth be? The size of a baseball? Of a golf ball? No. More like the size of a pea. A basketball and a pea.
The Sun is far away from us, 93 million miles away. But what does that mean? If the Sun was a basketball in the hoop of one basket at a basketball court, the Earth would be a pea at the other basket 94 feet away.
If we keep going, a quarter-mile away from the basketball Sun is a golf ball named Jupiter. A half-mile mile away is a pingpong ball called Saturn. Three-quarters of a miles away is a walnut named Neptune. The NASA spaceship Voyager 1 (the furthest out manmade object ever) is a speck of dust about a mile away from the basketball.
So the Sun is really big and far away But the other stars are so much farther away I can barely describe it. The Sun is just one of many stars in our Milky Way galaxy. One of the next closest stars is Alpha Centari over 26 trillion miles (4 light years away). But what does that mean? Let’s expand the model.
Suppose the Sun was a basketball was at Disneyworld, Orlando Florida, at the Space Mountain ride. At that scale, Alpha Centari would be another basketball at Space Mountain in Disneyland in Pasedena, California 2,500 miles away! And that’s just the closest star. Other stars in our galaxy are much farther away.
To make sense of them, we would have to change the scale of our model again. Shrink the Sun down to the size of a pea. Earth is the size of a poppy seed. Alpha Centauri is now a pea only a mile away still in Orlando Florida. Other stars in our Milky Way galaxy are peas in California. And that’s just our galaxy.
The next closest galaxy to the Milky Way is Andromeda. The Andromeda galaxy is 2 million light years away. What does that mean? We need another scale!
Stars are really far away. Musician George Hrab explained it best in his classic song, “Far.”
“I sense all the explosions going off inside your brain
As your mind gets blown by what I just did explain
Sorry if my words might drive you all insane
But that’s what happens when precision is your middle name
This stuff is far, [it’s really far] this stuff is far far far away
We’re talkin’ far, [like über far] you can’t get there by car in a day”
Talking Like a Scientist: Magnitude
Scientists have an easy tool to help make sense of really big numbers and make comparisons.. When looking at any two numbers, scientists count the number of digits in each number. For instance, with Barbie’s scale factor (the number of times it is shrunk), 64 has two digits a 6 and a 4. If two scale factors have the same number of digits (like 64 and 11), then scientists say they are of the same order of magnitude. If one scale has 2 digits and the other has 1 digits (like 64 and 6), the 64 is considered to be an order of magnitude smaller. Barbie dolls are an order of magnitude larger than a matchbox car.
Venus is closer to the Sun than Earth, but they are the same order of magnitude away. Andromeda is 6 orders of magnitude farther away from Earth than Alpha Centari.
Song, “Far” by George Hrab from the album Trebuchet.
Song “The Sun is a Mass of Incandescent Gas” – by They Might Be Giants, from the album Severe Tire Damage.