The first of three supermoons coming to NYC this summer will appear in Saturday's night sky -- wonderfully coinciding with the last Manhattenhenge of the year. It will also appear Friday night, as the moon will be fullest on Saturday at 6:25 a.m.

But what does that mean and why does it matter?

Full-moon lovers and those that love the Tom Petty album "Full Moon Fever" know that with the monthly (approximately 30-day) occurance comes balance in the universe, (or at least some explanation for why things feel different, or are unexpected).

But the supermoon is a bit scientific, too.

According to NASA scientist Dr. James Garvin, a supermoon occurs during a full moon, and when the moon is closer to the Earth than it normally is.

"It is called a supermoon because this is a very noticeable alignment that at first glance would seem to have an effect. The 'super' in supermoon is really just the appearance of being closer," he said.

And if you think all of this is malarky, consider that the term "supermoon" was coined by an astrologer.