Which Is Higher? Atlantic Ocean Or Pacific Ocean?

[KrazyHorse]

So we'd have to make the Canal a straight shot across panama and increase its cross-sectional area 13-fold to match Niagara falls. This is assuming the most ideal situation; in fact, most turbines run at around 30% efficiency, so now we're talking 40 times the current area. Add in the hydrodynamics and you're probably talking 200+ times the current area...

[Dis]

we all know it's useless and impractical. We're just discussing if it can be done.

As I said before. Cutting through mountains isn't as easy as games like civ2 would have you believe.

A dam would be useless anyways. How would the ships traverse? You could have a bypass, but that would have to use locks again.

[KrazyHorse]

I know you don't think we should do it. I'm just presenting the available power and the limiting factors as rough estimates as a general thought exercise.

[SpencerH]

Originally posted by KrazyHorse
Whyy? It's not like the earth's spin is accelerating...

Its evidence that the earths rotation is slowing

Heres the answer. It involves the rotation but not in the way I was (incorrectly) thinking.

You were taught correctly. The Pacific and Atlantic Oceans have different heights with the highest sea surface in the Western Pacific. But don't worry about all that Pacific water rushing into the Atlantic and flooding the Texas coast.

As far as equalizing levels, this has occurred but introduces an idea that many people find hard to imagine. The difference in heights is a result of a "dynamic equilibrium". Dynamic means changing, but equilibrium means balance, which we usually think of as no change. How can this be? Think of an unchanging balance as one like you can find on a scale where you place the same weight on both sides and it will balance -- always and forever. There is no new weight added or removed, no energy added or removed. This is Static equilibrium, an unchanging balance. A dynamic equilibrium involves the balance of changes. Imagine on your scale that you have cups instead of weights. Each cup the same size and is being dripped into and overflows but it will still balance if the fluid dripping in and out balances on both sides. Here there is a dynamic equilibrium with changes in mass or weight. If we want to imagine an equilibrium that also includes energy, let's have one side of the scale have a smaller cup than the other. Water drips in and overflows, but the two sides can never balance because the two cups can never hold the same amount of water. This gets a little complicated, so hang in there. The cups can't balance each other with weight alone. The lighter cup will go up and the heavy cup will go down. You can make a dynamic equilibrium by pushing down on the lighter cup. Now you have two cups with different amounts of water that balance. Hmmm? This can only happen with the addition of energy.

This is similar to how the sea surface heights can be different -- there is a dynamic equilibrium. It is indeed affected by the rotation of the Earth which is where some of the energy used to maintain the balance comes from. More comes from the Sun and its heat. The energy acts through winds on the sea surface and currents which tend to cause water to "pile up" where currents are swift. Imagine the surface of your morning juice in its cup. If you swirl that juice, the surface is no longer 'level' but slanted (and the slant rotates with the swirl). This slant is maintained as long as you continue to swirl the cup. You have an equilibrium that requires energy. The moment you stop adding energy by swirling, the surface of the juice levels out. It is now a static system with a static equilibrium that is simple to understand.

There is a huge science project (yes, scientists do science projects too) called TOPEX/Poseidon that looks at the sea surface (and other ocean information) from orbiting satellites. And there are oceanographers who specialize in studying the sea surface and what causes it to be different from flat. Some of this information is available on the Internet including really cool pictures made from satellite information. You can start looking at these locations:

http://www.madsci.org/posts/archives/oct98/905867100.Es.r.html

[Lul Thyme]

Originally posted by Docfeelgood
So which is heavier?
100 pounds of lead or 100lbs of feathers?

Hundred pounds is a hundred pounds such as sealevel is sealevel.

All the oceans that are at sealevel are the same height.

Thats an inane answer.
As many ppl have posted (see post above for example) oceans are not always at "sea level".
And thats what the original poster asked...

[TCO]

The acceleration (for a typical dam/hydro turbine) does happen almost completely at the nozzle/turbine and thus there is little headloss from flow thorugh the lake behind the dam. Is 30% efficiency reasonable for a water turbine? Steam turbines have efficiencies in the high 90's, but of course there is a larger pressure drop.

I agree with you that 18 feet of head is not worth drilling through 40 miles of mountains for...

[TCO]

Kitty, were you thinking of a heat cycle efficiency with the 30%? The water turbine is just a mechanical energy conversion device. Here is some Googled info:

http://www.tev.ntnu.no/vk/publikasjoner/pdf/ArneKjolle/chapter1.pdf

http://www.azsolarcenter.com/otherre/hydro1.html

[KrazyHorse]

Originally posted by SpencerH


Its evidence that the earths rotation is slowing

With a timescale of a billion years or so?

That's a bad joke...

As for the link it simply states that large scale meteorological and geological (but not astronomical) forces are to blame. The reason is not obvious from a physics point of view...

[KrazyHorse]

Originally posted by TCO
Kitty, were you thinking of a heat cycle efficiency with the 30%? The water turbine is just a mechanical energy conversion device. Here is some Googled info:

http://www.tev.ntnu.no/vk/publikasjoner/pdf/ArneKjolle/chapter1.pdf

http://www.azsolarcenter.com/otherre/hydro1.html

No. I know the difference between a heat engine and a turbine.

I did a quck google search on it and my hit gave an efficiency of 0.30. Either they were in error or I misread. I was slightly surprised at how low the efficiency was, actually, but decided to take what I thought was their word since I am but a theorist...

[KrazyHorse]

Originally posted by TCO
The acceleration (for a typical dam/hydro turbine) does happen almost completely at the nozzle/turbine and thus there is little headloss from flow thorugh the lake behind the dam.

However this means that the flowrate is much lower than the flowrate I used (the maximum possible value of ~8 m/s). A reasonable flowrate for a path which does not slope too much would have to be more like 1 m/s, so take the power I gave you and divide by 8...

[TCO]

Originally posted by KrazyHorse


However this means that the flowrate is much lower than the flowrate I used (the maximum possible value of ~8 m/s). A reasonable flowrate for a path which does not slope too much would have to be more like 1 m/s, so take the power I gave you and divide by 8...

I'm struggling to understand your thought process. Where did 8m/second come from? I tend to think in terms of volumetric flow rates versus velocities for a system with changing cross-sectional area. What's the velocity of water "accross the lake" behind Hoover dam?

[TCO]

How about we use nuke bombs to clear the channel? There are some ones that are designed for this kind of work...

[TCO]

also, just because the step change is only 18 feet does not mean the supply (and exhaust) channels are limited to this depth. They could be deeper, which will minimize head loss from friction with the channel walls.

[TCO]

Need to extend these channels off shore a little bit, too...

[TCO]

I like it better than the laser launching system which requires a beam that stays on target (and does not spread) over 1000 bounces and planetary distances or whatever...)