|
|
(3 intermediate revisions by 2 users not shown) |
Line 145: |
Line 145: |
| {{clear}} | | {{clear}} |
| | | |
− | <div lang="en" dir="ltr" class="mw-content-ltr">
| + | {{clear}} |
− | As the earth rotates, a given point on the earth (such as a seashore) gets nearer and nearer to the moon until it is as close to the moon as it will get on that day. When this happens, the gravitational pull on the ocean is at its greatest (since the force of gravity increases as distance decreases). Since the ocean is closer to the moon than the center of the earth, it pulls harder on the ocean, and this causes the ocean to rise up. That causes a high tide.
| + | |
− | </div>
| + | {{clear}} |
| | | |
− | <div lang="en" dir="ltr" class="mw-content-ltr">
| + | {{clear}} |
− | The earth continues to rotate, and our point on the seashore is soon getting farther and farther from the moon causing the tide to recede (i.e., we experience a low tide). When the earth rotates our seashore to 90 degrees relative to the moon the pull on the rigid earth is abut the same as it is on the center of the earth since the distances are about the same. But then as the earth continues to rotate a remarkable thing happens - the tide begins to rise again even though the seashore is getting farther from the moon. When it rotates to 180 degrees relative to the moon, the seashore is at its farthest distance from the moon on that day, and we get ''another'' high tide! How does this happen? Isn't the pull of the moon on the ocean at its weakest then? Yes, but the pull on the rigid parts of the plant is stronger than the pull on the ocean.
| |
− | </div>
| |
| | | |
− | <div lang="en" dir="ltr" class="mw-content-ltr">
| + | {{clear}} |
− | Therefore, when the ocean is on the opposite side of the earth relative to the moon, it is farther away, and the moon does indeed pull on it less than when the ocean is nearest the moon. But the moon is pulling at the rigid part of the earth's center which is ''closer'' to the moon, with the effect that the moon is pulling on the rigid portion with more force than it is pulling on the more distant ocean. In other words, we get a second high tide each day when the ocean is farthest from the moon because the moon is pulling the earth away from its ocean.
| |
− | </div>
| |
| | | |
− | <div lang="en" dir="ltr" class="mw-content-ltr">
| |
− | ;Neap tides and Spring tides:
| |
− | [[File:Tide_schematic.svg]]
| |
| {{clear}} | | {{clear}} |
− | Neap and spring tides describe the difference between the low tide and the high tide. When the high tide is very high and the low tide is very low on the same day, we have a spring tide. When the high tide is less high and the low tide is less low, it's a neap tide. We get two neap tides and two spring tides each month, because they are influenced by the phase of the moon (which is controlled by the relative position of the earth, sun, and moon).
| |
− | </div>
| |
| | | |
− | <div lang="en" dir="ltr" class="mw-content-ltr">
| + | <noinclude></noinclude> |
− | The sun affects the tides in the same way that the moon does, but the sun has a much lesser pull on the oceans than the moon does, because it is much farther away, and therefore the effect is much smaller. But it does have an effect, which is what accounts for the the neap and spring tides. When the sun and moon are 90 degrees apart, they do not work together to reinforce the tidal effect. One of them will be trying to cause a high tide, and the other will be trying to cause a low tide, so the high tide is not as high, and the low tide is not as low (a neap tide). When the sun, moon, and earth are in a straight line, they ''do'' work together to make the high tides higher, and the low tides lower, thus giving us the spring tide. Therefore, we get a spring tide when we have a new moon (when the moon and sun are both on the same side of the earth) and when we have a full moon (when the sun and moon are on opposite sides of the earth). The neap tides occur at the first quarter moon and three quarter moon.
| |
− | </div>
| |
− | | |
− | <div lang="en" dir="ltr" class="mw-content-ltr">
| |
− | <noinclude> | |
− | </div></noinclude>
| |
| {{CloseReq}} <!-- 6b --> | | {{CloseReq}} <!-- 6b --> |
| | | |
Line 328: |
Line 313: |
| <noinclude></noinclude> | | <noinclude></noinclude> |
| <!-- b. Visitar un zoológico o acuario que tenga una exhibición de océanos. Pensar en qué zonas oceánicas vivirían las criaturas que ve allí. --> | | <!-- b. Visitar un zoológico o acuario que tenga una exhibición de océanos. Pensar en qué zonas oceánicas vivirían las criaturas que ve allí. --> |
| + | |
| + | {{AY Honors/Zoo Visit}} |
| <noinclude></noinclude> | | <noinclude></noinclude> |
| {{CloseReq}} <!-- 12b --> | | {{CloseReq}} <!-- 12b --> |