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I feel like I'm at the ocean.

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Except here, the waves are man-made.

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Hi, Jacob and Catherine.

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I'm Dr. Hoffman from Old Dominion University.

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Hi.

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Hi.

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This is a great place to do research.

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We've been wondering, what is a tide exactly?

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A tide is the regular rise and fall of the surface of the ocean due to the gravitational

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force of the sun and the moon on our Earth.

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We learned that gravity is a force that exists between all objects.

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And it makes objects fall to Earth.

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That's right.

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And the bigger the objects and the closer they are to one another, the stronger the

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gravitational attraction between them.

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The sun is much larger than the Earth and the moon, but a lot farther away from the

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Earth than the moon.

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So which one causes the tides?

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They both do, but the moon plays the bigger role, being about twice as strong as the sun.

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As the two of them create a gravitational force on the Earth's oceans, it causes the

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water to move upwards towards the sun and the moon.

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And the Earth's gravity holds the water down.

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Right, but the tidal forces pull water sideways along the surface of the Earth, and this tug

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o' war creates a bulge in the surface of the ocean.

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If the moon's influence is stronger than the sun's, then is the bulge bigger beneath the

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moon?

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Yes, and due to the rotational motion of the Earth-moon-sun system, there is also a bulge

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on the opposite side of the Earth away from the sun and the moon.

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These bulges of water are large waves that we call high tides.

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So if the water bulges on opposite sides, then it must draw water away from the area

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between the bulges.

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Very good, and that is where low tides occur.

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How often do we have high and low tides?

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Many coastal locations, such as the Atlantic and Pacific Coast, experience two high and

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two low tides each day.

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But some areas, such as the Gulf of Mexico, only have one of each.

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Do the tides in a particular place always occur at the same time?

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No, but the answer's a little bit complicated.

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On average, high tides occur every 12 hours and 24 minutes.

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The Earth spins on its axis every 24 hours, so if you divide 24 by 2, you get 12.

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The extra 24 minutes is because of the moon's orbit about the Earth.

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Would high tides help bring objects floating in the water onto the shore?

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Tides do not typically have much of a role in transporting objects in the ocean.

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You can think of tides as a big sloshing motion where objects go as far in one direction as

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in the other.

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Here, let's check it out.

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That was cool, but what about the waves?

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Jacob, can you get in the pool?

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Can I?

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See the waves around Jacob?

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They look like they're moving the water forward, but actually they aren't.

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How is it that I stay in the same place?

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Each particle of water in a wave moves around in a circle.

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Energy moves forward while water particles remain in the same place, so an object floating

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on the water will rise and fall as the wave passes, but the object will not move forward.

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I think we definitely need more research about waves.

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Me too.

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Thanks, Dr. Hoffman.

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You're welcome.

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Enjoy the wave pool.

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You better stop researching the waves if you want to get there on time.

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Bianca does not like to be late.