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27 October 2011

High tide alert! Closest new moon of 2011 on 26 October 2011

Yesterday — October 26 — features the closest new moon of 2011. Look for higher-than-usual tides along coastlines throughout the world.

Because it crosses the sky with the sun during the day, you can’t see today’s extra-close new moon. Yet it will usher in large tides along the ocean coastlines for the next several days, especially if these high tides are accompanied by strong onshore winds.

Why is this moon so close? The reason is that the 2011 October new moon falls on the same date as perigee — the moon’s closest approach to Earth for this month. At perigee today, the moon lies only 221,862 miles (357,052 kilometers) away. Earlier this month, the moon had swung to apogee — its farthest point for the month — on October 12. At that time, it was 252,546 miles (406,434 kilometers) distant.

Why will the tides be higher than usual? At every new moon, the moon is more or less between the Earth and sun. Each month, on the day of new moon, the moon and sun line up to create wide-ranging tides, known as spring tides. High spring tides climb up especially high, and on the same day low tides plunge especially low.

Today’s extra-close new moon accentuates these monthly spring tides all the more.

- Earthsky