Murphy Center at Asphalt Green

555 East 90th Street

Text and Photographs by Neil deGrasse Tyson

Natural History special issue

Part of City of Stars photo essay.

The Municipal Asphalt Plant, a structure with a parabolic roof, arcing like the Saint Louis Arch.

A community sports, fitness, and recreational facility, this landmarked Municipal Asphalt Plant is an extruded parabola. A parabola happens to be the trajectory of an object that has exactly enough kinetic energy to forever escape the gravitational embrace of the object it orbits. When the Apollo astronauts left low-Earth orbit, their trajectory was parabolic, enabling them to reach the Moon without falling back to Earth. Simple orbits can have only three other shapes: circles, ellipses, and hyperbolas.

Long-period comets, such as those that take thousands of years to complete an orbit, travel along paths that are not quite parabolic—an indication that they are still gravitationally bound to the Sun. If we discover a comet with a truly parabolic orbit, we’ll know that it came from the depths of interstellar space and not from our own solar system.

An open-side-down parabola makes for an especially simple, yet stable structure; it was the shape of choice for the famous Gateway Arch in Saint Louis, Missouri.

The small sundial structure.

In the middle of the playground and picnic area behind the Murphy Center is a sundial atop a twelve-foot pole. Simple and elegant in design, the sundial is askew in relation to the Manhattan street grid, but it is properly aligned with Earth’s north-south meridian. The sundial is unreadable to all but extremely tall people.