Saturday's full Moon will be the year's closest — but not by enough to draw attention.
"The superstitious among us should beware of extra-big werewolves this weekend," warns Time magazine. For some reason, the world's news media are all aflutter over Saturday night's full Moon.May is the month this year when full Moon occurs closest to perigee, the point where the Moon is closest to Earth in its monthly orbit. But the Moon will be only 8% closer and larger than average. That's not enough to notice unless you're a very careful moonwatcher. Or use measuring tools.
And, this full Moon will shine only 0.16 magnitude brighter than average. That's only slightly more of a brightness difference than a skilled variable-star observer can just detect.
You can see the difference in a side-by-side comparison like the one above. But looking at the Moon by itself? Not likely.
If this is a "Supermoon," I guess Superman can only bench-press 108 pounds if I can bench-press 100.
If you want to compare Saturday's lunar apparition to the Moon at its very farthest, you can double those numbers. They're still not a lot.
Do go out and take a careful look. But beware of the power of suggestion. As my S&T colleague Tony Flanders just popped his head in to say, "You know some people are going to swear the Moon is just incredibly huge. If you'd told them the Moon was biggest when it was actually the smallest of the year, they'd probably say the same thing."
When it comes to science stories, some news editors never seem to grasp what the engineer's T-shirt says: "If you don't know it in numbers, you don't know it at all."