Why do all this? Sure, it might be fun, and pretty to look at. But does it accomplish anything? Would anyone really learn anything from it, that they wouldn’t have learned otherwise? Good questions.

First, here’s a one-question quiz for you:

Q: if the Earth were the size of a golf ball, about how big would the Moon be, and how far away?

A: Hold a golf ball in one palm, and a blueberry in the other; stretch your arms wide apart. This is a fair approximation of the relative sizes of the Earth and Moon, and the distance between them.

How did you do? If your guess was way off, don’t worry – the size and scope of the solar system is nearly impossible to visualize with charts and illustrations, and even interactive videos and apps struggle to convey the solar system’s scale. As a result, even the most basic spatial relationships between solar system objects are dimly understood by anyone other than passionate astronomers. But after seeing a realistic model, even a small child will not soon forget it.

So why hasn't it been done before? Well, in one sense it has. Worldwide, there are dozens of scale models of the solar system; Wikipedia has a useful guide here. Still, making a good one is no easy feat. Too large, and the model becomes difficult to experience, and even more difficult to remember. For example, the Sweden Solar System measures nearly two hundred miles from the Sun to Pluto, and even the superb to-scale models at New York City's Hayden Planetarium would stretch seventy miles if spaced proportionally. But make the model too small, such as in the otherwise wonderful 3/4 mile Sagan Planet Walk, and the planets become so tiny that they're no longer interesting to look at.

The length of Broadway in New York City offers an ideal scale to visualize the reach of the Solar System, out past Pluto to the outer edge of what is known as the Kuiper Belt. At this scale, the Earth is the size of a golf ball, the Moon is the size of a blueberry, and New York City's grid offers a handy way to dramatize and remember the relative distances between the planets.

Planet Walk NYC will be a destination activity for New York City visitors and residents alike!