The word “tides” describes the regular rising and falling of the ocean’s surface. Large lakes, such as the Great Lakes, also have tides, but the change in water level is only inches. Ocean tides are measured in feet.

Tides are caused by gravitational forces of the moon and the sun. The sun is huge, but it is 360 times farther from the Earth than the moon.

Even though the moon is much smaller than the sun, it has two times more influence on tides than the sun, simply because it is much closer to the Earth.

The moon’s gravitational force pulls on water in the oceans and causes bulges that create “high tide.” The moon’s gravitational pull is strongest on the side that faces the Earth. You might think that the opposite side of the Earth would experience a low tide, but that would be incorrect!

Amazingly, the moon’s gravity creates a high tide on both sides of the Earth. As the moon’s gravity pulls on the Earth, it pulls water into a bulge on the side closest to it.

Meanwhile, on the other side of the Earth, there is another high tide created by the moon slightly pulling the Earth away from the still water on that side.

There are a few different types of special tides that occur depending on the phase of the moon. Spring tides are strong tides that occur when the Earth, the moon and the sun are in a line.

During these times, the combined gravitational pull of the moon and the sun is very strong. Spring tides occur during the full moon and new moon phases.

The Proxigean Spring Tide is a rare, very high tide that occurs when the moon is unusually close to the Earth and in a new moon phase. During this time, the moon is between the Earth and the sun.

“Neap tides” are weak tides that occur when the gravitational forces of the moon and the sun are perpendicular to one another, pulling on the Earth from different directions. Neap tides occur during the quarter moon phase.

Tidal facts:

  • Isaac Newton first explained tides scientifically in 1686.
  • The highest tides in the world occur in the Bay of Fundy in Nova Scotia, Canada.
  • Because the moon moves around the Earth, it’s not always in the same place at the same time each day. So, the times for high and low tides change by 50 minutes each day.

 

12 Join the Discussion

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    • We agree, Amanda! It’s fun to see everyone realize the tide is coming in, then see them scrambling to gather their belongings and head to higher ground! Thank you for sharing your personal connection to this Wonder! :-)

  1. I thought it was cool that the moon’s gravitational pull makes high tide and low tide. Thank you for the great info, because I always wanted to know how the moon effected the Earth.

  2. I was really surprised that the gravitational pulls create high and low tide. I was astonished when the sun and the moon are perpendicular. It creates neat tides. I learned so much, thanks!

  3. Hi wonderopolis!

    Does earth and the moon rotate? If so, does it block falling asteroids and other falling objects?

    • Hi J.D.! The Earth and the Moon are both moving! The moon is actually moving away from the Earth little by little each year! The Moon is believed to have blocked falling space debris from Earth! Thanks for WONDERing with us! :)

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Have you ever wondered…

  • What does the moon do?
  • What are tides?
  • Does the sun affect ocean tides?

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Try It Out

Want to create a tide in your own home? Try this experiment! You’ll get to feel the power of the moon — on a ball in a bowl.

 

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If the tide has gone out and you’re howling at the moon for more lunar fun, visit Science NetLinks to explore moon phases and play a fun lunar cycle challenge game!

 

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