Why is it when you see a picture of the earth from space the sea does not run out over the 'edge'.
2007-05-15 11:04:27 · 15 answers · asked by oldtimer 3 in Science & Mathematics ➔ Astronomy & Space
Again I have to impress a sense of scale.
The Earth is so large that if you take a section of it like the surface of a pool, it is as near flat as anyone could measure. What we call "flat" or "horizontal", surveyors will know this means slightly curved, following the curvature of the Earth. So, if they are building a level road, say 10 miles long that road will be slightly curved.
Even from an airliner you can see the curvature of the horizon.
There is a saying that if you had a perfectly flat and frictionless billiard table, if you put the balls against the side cushions, they would roll to the center. That's because the table isn't following the curvature of the earth, and the sides would be actually slightly further from the center of the earth, which amounts to being slightly uphill.
But of course, the amount of difference would be millionths of an inch, and there is no such thing as a frictionless table (or balls).
But hopefully, that will give you some idea - the surveyors' "flat" is really slightly curved with the Earth, and would be quite measurable for a long flat road, but not a swimming pool surface (or a billiards table).
2007-05-15 11:50:08 · answer #1 · answered by nick s 6 · 3⤊ 2⤋
The surface of the earth in general is not level.
For example, when you stand on a clifftop at the coast and watch for a while you may see ships appearing over the horizon. This is because the horizon is the furthest you can see before the curvature of the earth intervenes. The ships are sailing toward you from beyond this point and so come into view.
If you've ever sailed out to sea with a view of the coast behind you, you may have noted that the highest points on land are the last to disappear ... this is because they 'stick up' above the curve of the surface.
It is possible to see the effect on very long straight level canals by putting 3 poles in the water so they all stick out the same amount. Standing at the first pole and sighting the third pole will reveal the middle one sticks up slightly - the further apart the three poles are the more pronounced the effect. The experiment was famously performed in 1870 to win a bet.
2007-05-16 00:54:40 · answer #2 · answered by Anonymous · 1⤊ 0⤋
The earth is round, and gravity pulls everything towards the centre. The sea is therefore like the skin on an orange - if you had a picture of the surface of an orange and zoomed in really close it'd look flat. But it would be slightly curved. The same goes for a swimming pool, the surface is curved but the earth is so big that you're zoomed in too close to tell.
2007-05-15 11:18:12 · answer #3 · answered by Joe 5 · 2⤊ 0⤋
The surface of the sea, from a very local perspective, appears as flat as a swimming pool. In fact, it is curved such that the surface remains equidistant from the earth's center (for all practical purposes and to avoid an excessively complex answer). In other words, the oceans surface, due to gravity, follows the curve of the earth. If you could measure with sufficient accuracy, you'd find that the surface of the pool is also curved, but even a very large pool would be only a small fraction of an inch higher at the center than at each edge.
2007-05-15 11:17:07 · answer #4 · answered by roxburger 3 · 3⤊ 1⤋
Run over the edge, to where?
"Flat" is a relative term. A rock can be flat until you get very close and see all the bumps. The surface of a swimming pool has the same curvature of the Earth, you just haven't got the acuity of vision to pick the curvature, that's all.
2007-05-15 11:48:17 · answer #5 · answered by Labsci 7 · 1⤊ 0⤋
Dude,
It DOES run over the edge.
But the centre of the earth acts like a big fountain and pushes water to the surface again.
I think the romans installed it
Yeah.... :o)
2007-05-16 01:18:38 · answer #6 · answered by loathsomedog 3 · 0⤊ 1⤋
Nope! It's not flat. However not only does it follow the curvature of the earth due to gravity it is also affected by the gravity of the moon. The sea/ocean swells towards the moon due to its weak force of gravity and this is what makes high and low tides.
2007-05-15 19:41:31 · answer #7 · answered by Ian M 2 · 0⤊ 0⤋
The earth's surface looks smooth from space. The ceiling in your house does to but it's not. Flies don't have magical suckers that enable them to stick to walls, they 'hook on' to the ridges and troughs on a surface that we can't see with the naked eye.
2007-05-15 11:31:11 · answer #8 · answered by Quizard 7 · 0⤊ 0⤋
The pool surface is the same as the earths surface, curved.
2007-05-15 11:17:02 · answer #9 · answered by Princess415 4 · 3⤊ 1⤋
Plonker,,,,,`edge`. You`ve got to laugh tho` apart from that, A swimming pool`s surface is curved and also has `Tides` Think about it. :o)
2007-05-15 12:34:02 · answer #10 · answered by Spanner 6 · 0⤊ 1⤋