If you were outside last week, you probably noticed the full moon – which reached the peak of fullness Sept. 9. And if you were anywhere along the coast, you also noticed the tide was higher than normal ... and also ... lower than normal. In Lewes, the highest of the high tides was up to the edge of the dunes. And along Del. 9, there was water across the road in some areas – all without the influence of a storm.
To find out why the tide is higher when there's a full moon, we went to University of Delaware professor of physics and astronomy, Harry Shipman, who explained: "Tides are higher when the moon is full because at that time the gravity from the moon and sun are pulling together on the earth. They are pulling in the same direction."
USA TODAY had a great explanation of the lunar influence on tides back in 2007: "During both new and full moon phases, the gravitational attraction of the moon is in line with the gravitational pull of the sun, producing high tides and low tides."
Those highs and lows are typically 20 percent higher and 20 percent lower than an average tide.
Those high highs and low lows are about the same at both the full and the new moon (when the moon is dark). The next new moon is Sept. 24 so you can expect higher and lower tides then, too.
Now, how about those supermoons that caused a buzz – and some spectacular photography – all summer?
Shipman said they also have an influence on tides, more even that a traditional full or new moon: "A supermoon happens when the moon is near the closest point in its orbit. The moon only comes a few percent closer at some points in its elliptical orbit around the earth. But every percent makes some difference in the height of the tides. There are supermoons every year. The next is September 28, 2015."
This year, there were five supermoons: two new moons in January and full moons in July, August and September – the one we just experienced.
Send your science questions to Molly Murray at mmurray@delawareonline.com
Follow her on Twitter @MollyMurraytnj
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