by Erik Baard
The moon increases in apparent size for two reasons. Routinely we observe an apparent swelling in the moonrise. Because of a quirk of human optical neurology we percieve the moon as larger on the horizon, rather than overhead. But the moon is also at times closer or further from Earth in different points of its elliptical orbit. Tonight is perigee, the closest pass. It will appear 14 percent larger and 30 brighter than what you’ll typically find for the rest of the year.
Of course, oldsters might tell a young’n that the moon was bigger and brighter when they were young. Well, they’re right in fact but there’s no way a human could detect it: the satellite is ever-so-slowly spiralling away from its host planet. Each year it stretches our gravitational bonds by about 1.6 inches (4cm).
The moon tantalizes us, draws us into the Cosmos beyond. At some level, this is our narrowness making us silly: we are born, live, and die in space as much as those who might do the same on any other world. Still, it remains a place of national posturing, from the Space Race of the 1960s to the emerging powers of India and China.
For an inner city child, however, the lure of the moon is that it reveals a real topography to his or her eyes from any street corner, even without expensive equipment or the crystal clear skies of the backwoods. As South Bronxite Neil deGrasse Tyson told me for a Village Voice article, a realm of personal possibilities was opened when he stared at the moon from his stoop through a pair of binoculars after his father took him to Hayden Planetarium at the American Museum of Natural History.
“I saw the mountains and valleys and craters of the moon. It became another world, something to learn about,” he remembers. “I knew I wanted to be a scientist since I was nine years old and I never wavered.”
He is now an astrophysicist and the Frederick P. Rose Director of the Hayden Planetarium.
* As a side note, the mountains are seen better on a half or crescent moon, because features are seen in relief. Straight on, light bounces back up from every little crevice, washing out our view.
My own enjoyment of tonight’s delight takes me back to the wintry Snow Moon perigee of February 1988. I was staying over at Smith College with my then-girlfriend (who now works for an oil company — some things weren’t meant to be). Seeing her sleep inspired this poem (and forgive that WordPress always screws up spacing and formatting):
to the broad and barren moon
the peace of being lost
in my sleeping lover’s