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biochemistry and biophysics

TRIVIA ARCHIVE: 2012 - 2013 - 2014 - 2015 - 2016


How does the pull of the Moon’s gravity affect Earth’s surface?

It creates tides.

The moon, along with the sun, exerts a gravitational pull on the Earth’s surface. The solid part of Earth may deform a bit, but water being fluid is more free to move.

Tides are the periodic changes in sea level with respect to land. The pull of the moon and sun, along with the centrifugal force created by the rotating Earth, cause water levels to rise and fall. The gravitational pull on water causes the oceans to bulge out in its direction.

We have two tides every day. Earth is spinning, the Moon travels around it, and together they travel around the sun. No wonder water can’t stand still.

The highest tides in the world are at the Bay of Fundy in Nova Scotia, Canada. Tides roll in and out, and difference in the height of the water has been as much as 53 feet.

This week's answer:

Where is the moon larger – at the horizon or directly overhead?

The moon is always the same size.

Because the moon’s orbit is elliptical, there are times when it appears larger because it is closer, but on any given night, the Moon’s size remains constant.

The moon may look larger when it is closer to the horizon line and smaller when overhead, but this is an optical trick known as the Moon illusion.

The apparent size of the moon relates to our perception of distance. When the moon is near the horizon, we perceive it to be farther away from us than when it is directly overhead. Objects near the horizon line (buildings, trees, etc.) help reinforce the idea of the Moon’s inflated size because we know that it is behind those objects.

When it is above us, surrounded by empty space with no terrestrial reference points, it appears smaller. The same illusion applies to celestial bodies as well. Constellations may look larger the closer they are to the horizon. The stars, the Sun, and the Moon are identical in size no matter where they are in the sky.

Next week's question:

Which is bigger: the Moon or Pluto?


Past questions and answers are in the trivia archives: 2012 / 2013 / 2014 / 2015 / 2016

Questions? Comments? Corrections? Contact Mary Leonard,