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HysteryDiagnosis Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 06:48 PM
Original message
The gravity of the situation.... mind experiment, physics question,
brain fart.

Something has been bothering me since reading the first chapter of The Final Theory. A close relative of mine who has an analytical mind, engineering background and is in short a brilliant person is up to about chapter 4 where the tides are discussed.

My problem is this. Each and every day, hundreds of millions of tons of water are lifted 2 to 4 feet (the tide) and then lowered back down again supposedly by the sun and the moon.

Now, if this water were trapped in a certain way as to force it to return to its natural level through turbines or water wheels, hundreds of billions of watts could be produced FOR FREE.

Since one of them there laws of thermodynamics states that energy can neither be created nor destroyed, where in the heck would this energy come from, rather, what "other" system would have to be drained in order to balance out the equation??

Remember, this has been happening for MILLENIUM. That's a bunch of watts and I doubt anyone here can explain it away with Newton's, Einstein's or even Feynman's description of how things work.
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Fredda Weinberg Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 06:51 PM
Response to Original message
1. The Earth is not a closed system
The sun is input to our weather and tide cycles ... so we can harness their energy without worrying about replenishment. The universe is closed, so the total energy is conserved.
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hunter Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:16 PM
Response to Reply #1
16. That's not the right answer really.
Fusion within the sun fuels much of our weather, but the tides have more to do with the angular momentum of the dust that formed our solar system.
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Fredda Weinberg Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 08:36 PM
Response to Reply #16
42. The question regarded closed systems
and I happen to remember from my chemistry classes years ago that life on Earth depended on the fact that we are *not* a closed system.

As for the drag of the tides, that's not conserved angular momentum - would be if it happened in the vacuum of space but here, it's just contributing to the entropy that eventually will leave us with evenly distributed energy and no life.
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hunter Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 09:23 PM
Response to Reply #42
43. Why does one face of the moon always face the earth?
My physics was hammered into my head by a brutally honest physics professor who promised he would weed out all the unpromising pre-meds. And he did too, about a third of the class. I passed. I'm hoping at least some of it stuck. :P

I know a bit about evolutionary biology too.

Nah, I'm not being snarky... hey, wanna see my Bev Harris scars?
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Fredda Weinberg Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 10:54 PM
Response to Reply #43
49. Cause it revolves as it rotates
But I can't tell you how the Earth and Moon got locked into this relationship.

BH? BS is more like it. I'm sorry for your scars, but I tried to warn everyone.
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Jamastiene Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Aug-12-06 01:36 AM
Response to Reply #43
56. Maybe it's the magnetism.
Earth has a north and south pole. Maybe the moon does too, but tilted so that it always faces our opposite pole. I'm confused.
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MercutioATC Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 06:51 PM
Response to Original message
2. Do you mean something like THIS?
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bananas Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 06:53 PM
Response to Original message
3. What are you talking about?
What is this "Final Theory"?
I've seen you mention it before.

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G2099 Donating Member (500 posts) Send PM | Profile | Ignore Thu Aug-10-06 07:02 PM
Response to Reply #3
8. Link to The Final Theory here:
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HysteryDiagnosis Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:10 PM
Response to Reply #3
11. Yes.... I'm just bananas over it.... really. :)
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originalpckelly Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 09:27 PM
Response to Reply #11
44. I do a little work in this area.
I might give that site a whirl.
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Kutjara Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 06:56 PM
Response to Original message
4. The tidal pull of the Moon is caused by gravity.
As yet, we have no satisfactory explanation for how gravity works. It is the great problem that needs to be solved in order for quantum mechanics and relativity to be reconciled. There's a good book called "5 Roads to Quantum Gravity" that explains the leading theories attempting to explain gravity's seemingly paradoxical properties.

What makes gravity puzzling from the standpoint of your question is that it appears to generate no friction, and so can keep operating almost eternally in the absence of external disturbances. So the Moon can orbit and orbit for millions of years, exerting a constant gravitational force on the earth, pulling the seas and (to a much lesser extent) the land on Earth towards it, then releasing them as it passes. Ultimately, the Moon will crash into the Earth, but not because of gravity. Instead, collisions with space debris and the force of the solar wind will slow it down and slowly spiral it inwards.

Discovering how gravity exerts its force 'for free' will open the doors to a whole new world of physics.
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karlrschneider Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:04 PM
Response to Reply #4
9. I'll bet you a million bucks against $100 the moon never crashes
into the earth!

:evilgrin:
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Kutjara Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:12 PM
Response to Reply #9
12. You're quite right. My mistake.
I forgot about the transfer of momentum from Earth to Moon. Actually, the Moon is receeding from the Earth.

Here's a good link explaining the phenomenon:

http://www.physlink.com/Education/AskExperts/ae429.cfm
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karlrschneider Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:18 PM
Response to Reply #12
17. Hehe, didn't mean to be a smartass, tryin'a make a funny.
:hi:
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Kutjara Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:20 PM
Response to Reply #17
18. Not at all, I'm glad you pointed it out.
It made me look it up and refresh my memory. Thanks!
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Wiley50 Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:53 PM
Response to Reply #17
28. Karl, Your Okie is showing n/t
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Wiley50 Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:58 PM
Response to Reply #17
29. Karl, Your Okie is showing n/t
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Jamastiene Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Aug-12-06 01:26 AM
Response to Reply #4
54. Wow, don't you have a rosy view for us in the future?
I'm sure glad you aren't Jean Dixon. I sure don't want to be here when the Moon crashes into us. :sarcasm: :P j/k
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AngryAmish Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Aug-12-06 09:19 AM
Response to Reply #4
65. Like this?
The year 1994: From out of space comes a runaway
planet, hurtling between the Earth and the Moon,
unleashing cosmic destruction. Man's civilization is
cast in ruin.

Two thousand years later, Earth is reborn...

A strange new world rises from the old: a world of
savagery, super science, and sorcery. But one man
bursts his bonds to fight for justice! With his companions
Ookla the Mok and Princess Ariel, he pits his strength,
his courage, and his fabulous Sunsword against the
forces of evil.

He is Thundarr, the Barbarian!

<Image>
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Reckon Donating Member (729 posts) Send PM | Profile | Ignore Thu Aug-10-06 06:57 PM
Response to Original message
5. Centrifugal force of the moon, maybe?..
And could it be slowing down?
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skids Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:12 PM
Response to Reply #5
14. Actually no it's the earth that loses energy in this case.
The moon is actually gaining energy. The earth is losing it's spin, plus some amount is lost as heat.

I like the idea of tidal power, but I like wave power even better. It's just about as predictable and as far as I know has the lowest impact on the environment as any other technology.



http://www.democraticunderground.com/discuss/duboard.ph...
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karlrschneider Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:01 PM
Response to Original message
6. Tidal currents ARE used to produce electricity in some places.
What is "drained" is the momentum between the earth and the moon which happens whether or NOT tidal
motion is utilized. Extracting some of that kinetic energy does -slightly- increase the rate of reduction of angular momentum but compared with the available energy is virtually infinitesimal.
At some far future time, the moon will "slow down" to exactly match the rate of rotation of the
earth. (It won't 'move' in the sky any more.)

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bananas Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:01 PM
Response to Original message
7. Energy from tides
Take a look at this wiki page:
Earth's energy budget

<snip>

The total flux of power entering the Earth's atmosphere is estimated at 174 petawatts. This consists of:

<snip>

# tidal energy (0.002%, or about 3 terawatts; or about 0.0059 W m-2)

* This is produced by the interaction of the Earth's mass with the gravitational fields of other bodies such as the Moon and Sun.

<snip>

http://en.wikipedia.org/wiki/Earth%27s_energy_budget
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karlrschneider Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:09 PM
Response to Reply #7
10. Interesting link from the Wiki article
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bananas Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:12 PM
Response to Original message
13. Tidal energy is turned into heat
A good example is the moons of Jupiter:
http://www.astrobio.net/news/article603.html

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BrewerJohn Donating Member (499 posts) Send PM | Profile | Ignore Thu Aug-10-06 07:15 PM
Response to Original message
15. I think the energy would ultimately come out of Earth's rotation
Gravitational force from the Moon and Sun doesn't by itself cause the tides. If the Earth
did not rotate with respect to one or the other, the tidal forces would just result in
static "bulges" in water level. The rotation makes the bulges travel and produces the
up/down cycle at any fixed location.

Because the up/down motion is cyclic, there is no average work done (energy expended)
over the cycle. Except for "frictional" effects of all that water in motion, running
over the surface, of course. The energy dissipated in the friction has to come out of
the rotational energy of the Earth, which causes the motion.

Now if the potential energy of water that has risen is tapped in the process of its
returning to the low level, that would take additional energy out of the system. That
would be equivalent to introducing additional "friction".

The result would be that the rate of the slowing of the Earth's rotation would be
slightly increased. Nothing to worry about, though. Can you imagine just how much energy
is stored in a whole planet spinning at the rate of one rotation per 24 hours?
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HysteryDiagnosis Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:26 PM
Response to Reply #15
19. Because the up/down motion is cyclic, there is no average work done
I suggest that you take just two (2) buckets of water and raise them over your head twice a day for a few thousand years.... then tell me if any work is being done.
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Realityhack Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:32 PM
Response to Reply #19
20. lol
The other poster is correct though. Physics wise no work is done when an object is moved up and then back down to its original possition with the exception of anything lost to friction.
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HysteryDiagnosis Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:38 PM
Response to Reply #20
22. Well then.... what is it when you move a mass a certain
distance, even if that distance is 2 to 4 feet up?

http://id.mind.net/~zona/mstm/physics/mechanics/energy/...
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BrewerJohn Donating Member (499 posts) Send PM | Profile | Ignore Thu Aug-10-06 07:59 PM
Response to Reply #22
30. When "you" move a mass up and then back down
you do work on it, to be sure. The difference is that the energy you gave up to
do it, you can't get back in the same form. Heat gets generated, and so forth.

When the gravitational field does the work, though, it gets all the energy back when
the mass is returned to its original position. Except for any that gets lost in
friction, which is a tiny fraction of the total involved for the tides rising
and falling.
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HysteryDiagnosis Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 08:01 PM
Response to Reply #30
31. Oh...... it gets it back..... I see... hadn't thought of that angle.
there apparrently isn't a 15% restocking fee. Tee hee.... I jest. thanks for that....
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Wiley50 Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 08:06 PM
Response to Reply #22
33. You Folks aren't sailors
Where I docked last summer on Long Island
My boat went 13 feet up and down
twice a day
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HysteryDiagnosis Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 08:07 PM
Response to Reply #33
35. I suggest you lay off the Viagara for awhile there.... really.
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Wiley50 Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 08:08 PM
Response to Reply #33
36. You Folks aren't sailors
Where I docked last summer on Long Island
My boat went 13 feet up and 13 feet down
twice a day
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Wiley50 Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 08:11 PM
Response to Reply #36
37. Seriously. The tidal range is much greater by locality
As a sailor, I experiance it
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HysteryDiagnosis Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 08:22 PM
Response to Reply #37
38. Well then get ready for the Bay of Fundy tidal range......
Edited on Thu Aug-10-06 08:22 PM by 4MoronicYears
http://members.tripod.com/~bore_encyclopedia/BasicNA.ht...

The Bay of Fundy in Canada divides the peninsula of Nova Scotia from New Brunswick. The Bay divides into two arms of water at the north-east end - Chignecto Bay and The Minas Basin. Because of the anticlockwise rotation of the earth, the tides are larger in the Minas Basin. Burncoat Head, Nova Scotia, has the largest tidal range in the world with a mean spring range of 14.5m (47.5ft)! And the mid-tide flow in the vast Minas Basin entrance channel, north of Cape Split, equals the combined flow of all the streams and rivers on earth!
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AZCat Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 09:54 PM
Response to Reply #15
48. Don't know about rotational energy of earth, but...
the earth's kinetic energy of translation in its orbit is 2.57x10^41 ergs, or 7.14x10^27 kw-hr.

The moon's kinetic energy of translation in its orbit is 3.63x10^35 ergs, or 1.01x10^22 kw-hr.
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Cleita Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:36 PM
Response to Original message
21. Remember, it's not nice to fool with Mother Nature and this is
major fooling. On the other hand woods dwelling people
in the Northwest have figured out ways to use the flow of a creek to generate electricity without interrupting the stream's flow. Couldn't you do the same with the ebb and flow of the tides?

And you can ignore me too as I really don't know anything about this, but I do hate to see wetlands, rivers and oceans messed with by engineers and their dams and other projects that screw up an environment.
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HysteryDiagnosis Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:40 PM
Response to Reply #21
23. But it does give the planet a good excuse to wage natural
disasters on us.... I'm KIDDING. It's not the tapping of the tides I'm interested in... it's the source of the so say "free energy" that lifts them up and down ENDLESSLY.
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Warren DeMontague Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 08:28 PM
Response to Reply #21
40. Well, pretty much *anything* we do will be "fooling" with mother nature.
The key is to do it in as low-impact a fashion as possible.

OTOH, like the song says..

"You cannot go against nature...

'cuz if you do...

goin' against nature

is part of nature, too"
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porphyrian Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:40 PM
Response to Original message
24. It could be done with floats and things that compress...
...but I'm not an engineer.
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HysteryDiagnosis Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:43 PM
Response to Reply #24
25. Well howdy neither am I.... but imagine if ALL OF THE FISH
decided to swim west to east..... would it, could it make the sun rise in the west?
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porphyrian Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:46 PM
Response to Reply #25
27. Only if they did it really fast...
They'd have to stop the current spin first, and it takes a bunch of energy to defeat inertia. I didn't flunk out of physics for nuthin'.
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leftofthedial Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 07:45 PM
Response to Original message
26. and solar power and wind power don't work either!
egad!
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Pobeka Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 08:04 PM
Response to Original message
32. The moon is in essence "lifting" up the water.
The moon lifts the water, due to it's gravitational pull on the water.

I think what is of critical importance here, is to recognize that if we slow the lifting on one side (incoming tide), and don't slow the outgoing tide on the other side of the planet an equal amount, all the water will get stuck on one side of the planet, so choose your country of residence carefully. :P
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HysteryDiagnosis Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 08:06 PM
Response to Reply #32
34. Not a very large problem if you have a very large
one of these.....

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Pobeka Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 09:51 PM
Response to Reply #34
46. :-)
Edited on Thu Aug-10-06 09:52 PM by Pobeka
:rofl: :rofl:
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Rex Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 08:24 PM
Response to Original message
39. I always look at that huge nuclear ball of gas and wonder why
we don't exploit the energy from the Sun. Guess it would be too free. :eyes:
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HysteryDiagnosis Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 08:29 PM
Response to Reply #39
41. What if..... oh gawd this hurts..... what if..... what if the real
explanation for many of the "holes" in contemporary physics could be explained by a theory that states that EVERYTHING in the universe is expanding. I don't mean the galaxies, the stars, the outer boundaries of the universe but EVERYTHING. I want to make myself clear. All things expanding at an equal rate, which would make the expansion nearly impossible to measure. Wouldn't that be a hoot.
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Rex Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Aug-12-06 01:14 AM
Response to Reply #41
53. Einstein asked that question.
Would anybody notice?
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HysteryDiagnosis Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Aug-12-06 08:24 AM
Response to Reply #53
61. Not unless they had a ruler that wasn't expanding too. n/t
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Jamastiene Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Aug-12-06 01:33 AM
Response to Reply #41
55. The Universe IS expanding.
I can't remember where I read that, but I did read it. Sagan, maybe? Yeah, I believe that is where I read it. In Carl Sagan's book, Billions and Billions.

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BrotherBuzz Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 09:44 PM
Response to Original message
45. 2 to 4 feet is squat and won't turn a turbine
Seek eight feet or more then you may have the start of something (well, with today's technology, anyway).

Laws of thermodynamics are interesting to reflect on and some people view cyclonic storms (Hurricanes) as the equalizer - where does all that energy come from? Mother nature balances things in odd ways and has a wicked sense of humor; There are forces at work much more significant than just the tides. :shrug:

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MercutioATC Donating Member (1000+ posts) Send PM | Profile | Ignore Fri Aug-11-06 09:58 PM
Response to Reply #45
51. It's more about current speed than it is about tide height.
4-5 knots will work just fine.
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BrotherBuzz Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Aug-12-06 02:30 AM
Response to Reply #51
58. I guess I was thinking like a damn dam engineer
Bummer, Max ebb at the Golden Gate rarely runs faster then 4.0 Knots
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MercutioATC Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Aug-12-06 02:33 AM
Response to Reply #58
59. I've read that there are only 20 or so places in the world
that are prime tidal generator locations.

...at least until technology improves.
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rasputin1952 Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Aug-10-06 09:52 PM
Response to Original message
47. I have read through this thread and have come to a conclusion...
Remember: KISS...Keep It Simple Stupid... :D

Let's not get too far ahead in the theory aspect. Your statement on the First Law of Physics, "Since one of them there laws of thermodynamics states that energy can neither be created nor destroyed", is correct, however, energy can be transformed from one for of energy to another when certain circumstances exist.

There are plenty of ways to convert some energy forms into others; sunlight can be transformed into electrical energy for example. In the case of Tidal energy, which is essentially motion, it can easily be used to transformed into electrical energy, just as wind is transformed into electrical energy.

I'm not a physicist, but I know that by using existing technology, and using a small portion of tidal movement passing through either blades or "squirrel cage" apparatus, or anything else that can move a magneto, will transform energy into a more usable form for humanity.

The question is money...Long ago someone said that the reason Solar Power never took off, is because there was no meter between the sun and the earth. Of course that is simplistic, but there is truth in the statement.

Harnessing tidal forces should be relatively easy, why we haven't gone there is beyond me.
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muriel_volestrangler Donating Member (1000+ posts) Send PM | Profile | Ignore Fri Aug-11-06 05:27 AM
Response to Reply #47
50. Existing and planned tidal power stations around the world
http://en.wikipedia.org/wiki/Tidal_power#Resource_aroun...

La Rance in France, at 240MW peak capacity, has been going for abour 40 years. The UK is seriously looking at a barrage across the Severn Estuary with a capacity of over 8000MW (some wonder about the environmental impact on mud flats and so on, as well as the capital cost). The Severn is an obvious place to do it - a very large tidal range (over 8m), and several million people live nearby. The advantage of tidal power is it's very predictable; the disadvantage is you also know there are periods each day when it will produce nothing.
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MercutioATC Donating Member (1000+ posts) Send PM | Profile | Ignore Fri Aug-11-06 09:59 PM
Response to Reply #47
52. Does nobody Google? We HAVE gone there...
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DoYouEverWonder Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Aug-12-06 09:06 AM
Response to Reply #47
64. Why haven't we gone there?
Can you spell BIG OIL.

They are the biggest bunch of traitors in history, because they deny the people of the earth access to clean and sustainable forms of energy. The technology is there. Heck, sailboaters have be doing it for decades and can live quiet comfortably thank you.

One more reason to support Al Gore in 2008.



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lumberjack_jeff Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Aug-12-06 01:36 AM
Response to Original message
57. This energy is borrowed from the rotational intertia of the orbiting...
bodies. Slowing the water that flows from low tide to high perturbs the orbits of the earth/moon system by a brazillionth of a piconanocentimeter every uh... century.

I'm mister smarty-pants, and thanks for asking!
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IChing Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Aug-12-06 02:36 AM
Response to Original message
60. The book sucks big time
these guys never went to college for science or have any advanced mathematics or advanced physics formulas to back up there
$59.99 theorem.
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HysteryDiagnosis Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Aug-12-06 08:59 AM
Response to Reply #60
62. Quote.....
The only thing that interferes with my learning is my education.
Albert Einstein
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burythehatchet Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Aug-12-06 09:02 AM
Response to Original message
63. .
where in the heck would this energy come from, rather, what "other" system would have to be drained in order to balance out the equation??

The resulting energy would be stored as potential energy, until used.
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HysteryDiagnosis Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Aug-12-06 12:38 PM
Response to Reply #63
66. Ah ah ah.... can't get somethin' fer nuthin'. Gotta put a load on
either the moon, the earth or both.
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