The Solar System to Scale

All us of remember learning about the Solar System in school. It is, for most schoolchildren, our first introduction to astronomy and the universe. Most of us started by learning the names of each planet, typically through a mnemonic device such as the extremely popular, “My Very Educated Mother Just Served Us Nine Pizzas.” (I personally remember learning “My Very Eccentric Mother Just Swallowed Up Nine Pickles”). Of course, Pluto was downgraded to a “dwarf planet” in 2006, largely to address the discovery of numerous other similarly sized objects, specifically a Pluto-sized object billions of miles beyond Neptune, which would later be named Eris. After this, the most popular mnemonic seems to have become “My Very Educated Mother Just Served Us Nachos.” Once we learn the names of the planets, we typically move onto a model of the Solar System, which typically looks something like this:

Image: Pixabay

Or it may be a physical model like the one below.

Image: Pics about Space

Scale Problems

But models like these have two significant problems when it comes to scale. First, the sizes of the planets are way off. These models lead us to believe that Jupiter is almost the same size as the Sun, but it’s not even close—the sun’s diameter is almost 10 times that of Jupiter. If we were to create a model with the planets’ sizes to scale, it would look more like the following visualization.

In this model, you can see that Jupiter is significantly smaller than the Sun. But more noticeably, Mercury, Venus, Earth, and Mars are so small that they are barely visible. This is, of course, the primary reason why models resize the planets—without doing so, it would be very difficult to study the planets and their different surface characteristics.

But, the bigger scale issue is one of distance. Models typically show the planets relatively close to each other, but this is far from the case. In fact, if you were to take a picture of the solar system with the Sun on the left and Neptune on the right, then resize that photo down to 800 pixels wide, it would look something like this:

There is nothing wrong with your screen. The Solar System is so huge that, when scaled down to an image of this width, the planets and even the Sun, are so small you cannot even see them (Note: I’m only accounting for the size of the objects in the Solar System, not the light produced by the Sun and the reflection of that light off the planets). If you were to assume the Solar System started at the Sun and ended at Neptune (it does not—there are numerous objects outside of Neptune including the Kuiper Belt and Oort Cloud, which extend many billions of kilometers past Neptune) and ignored smaller objects—moons, asteroids, dwarf planets, comets, dust, etc.—the Solar System would be 99.98% empty space.

A Truly Scale Model

Clearly, this problem of distance is the reason why so few of our Solar System models are truly to scale. It’s a nearly impossible task to create scale models that are useful in any practical way. But I wanted to see if I could create a truly scale model of the Solar System using Tableau. First, of course, I collected data on the sizes and distances of the planets.

Object	Distance from the Sun (km)	Diameter (km)
Sun	NA	1,391,400
Mercury	57,910,000	4,800
Venus	108,200,000	12,100
Earth	149,600,000	12,750
Mars	227,940,000	6,800
Jupiter	778,330,000	142,800
Saturn	1,424,600,000	120,660
Uranus	2,873,550,000	51,800
Neptune	4,501,000,000	49,500

I then created my visualization:

You’ll notice the scroll bar at the bottom. The screen itself shows about 6.5 million kilometers. Considering that Neptune is over 4.5 billion kilometers from the Sun, that means you’d need to page to the right almost 700 times to get to Neptune. If we could stretch this visualization out to its full width, it would be almost as long as 2 ½ football fields!

Of course, the only way to truly get a feel for the scale is to interact with the visualization. But be careful—if you scroll to the right too quickly, you are very likely to miss the planets because many of them are very small (remember that Mercury, Venus, Earth, and Mars are almost invisible on our first visualization) and because there is simply so much empty space. So, use the key at the top to scroll to the correct distances and locate each planet.

Note: As usual, I had to scale down the size of this viz (no pun intended) in order for it to fit nicely on the blog, but feel free to go directly to my full-size version of the visualization.

To Scale: The Solar System

Before closing out this post, I wanted to be sure to direct you to a short video which documents an attempt by filmmakers, Wylie Overstreet and Alex Gorosh, to build a scale model of the Solar System in the Black Rock Desert in Nevada. It is definitely worth the five minutes it takes to watch it, so check it out here.

Ken Flerlage, April 14, 2017

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