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Tides and Waves
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First segment of the Ocean Odyssey describes tides and waves and how they are created by the gravitational forces of the sun and moon.
I feel like I'm at the ocean.
00:00:00
Except here, the waves are man-made.
00:00:05
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
00:00:18
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.
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- Valoración:
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- Idioma/s:
- Niveles educativos:
- ▼ Mostrar / ocultar niveles
- Nivel Intermedio
- Autor/es:
- NASA LaRC Office of Education
- Subido por:
- EducaMadrid
- Licencia:
- Reconocimiento - No comercial - Sin obra derivada
- Visualizaciones:
- 500
- Fecha:
- 28 de mayo de 2007 - 15:34
- Visibilidad:
- Público
- Enlace Relacionado:
- NASAs center for distance learning
- Duración:
- 03′ 13″
- Relación de aspecto:
- 4:3 Hasta 2009 fue el estándar utilizado en la televisión PAL; muchas pantallas de ordenador y televisores usan este estándar, erróneamente llamado cuadrado, cuando en la realidad es rectangular o wide.
- Resolución:
- 480x360 píxeles
- Tamaño:
- 19.50 MBytes
