Lunar energy...

[Externet]

Hello.

Tidal currents are a brutally high potential suppliers of all the energy the planet may need, and much more. The ´generator´ is the orbiting moon.

 

Assumming (or dreaming) that all the tidal currents in all the planet seas and waters were tapped to supply the world energy needs and more; would that affect the rotation or orbits of earth-moon ?

 

-Yes, a lunatic question-

[Robittybob1]

Hello.

Tidal currents are a brutally high potential suppliers of all the energy the planet may need, and much more. The ´generator´ is the orbiting moon.

 

Assumming (or dreaming) that all the tidal currents in all the planet seas and waters were tapped to supply the world energy needs and more; would that affect the rotation or orbits of earth-moon ?

 

-Yes, a lunatic question-

Yes you would end up slowing the rotation of the Earth, day lengths would get longer and the tidal acceleration the Moon would get stronger, hence the Moon would move away faster and then the magnetic field of the Earth would ultimately fail and extinction would be end the result.

This would be over a very long period and many other resources may be limiting restraints so that none of this ever happens.

Good idea though!

[studiot]

I can't see that it would make any difference to the rotation of the Earth since the energy of the tides has already been transferred to the water on Earth so diverting that energy somewhere else would not loose it to the planet.

The fundamental rotation of the planet does not stem from the Earth - Moon interaction.

 

BTW I hope you realise that the term tidal current refers to the horizontal movement of the water and the term tide refers to the vertical?

Both motions can be utilised as an energy source, but only some of the energy of motion cna be extracted since the water must still move to extract the energy.

[Robittybob1]

I can't see that it would make any difference to the rotation of the Earth since the energy of the tides has already been transferred to the water on Earth so diverting that energy somewhere else would not loose it to the planet.

The fundamental rotation of the planet does not stem from the Earth - Moon interaction.

 

BTW I hope you realise that the term tidal current refers to the horizontal movement of the water and the term tide refers to the vertical?

Both motions can be utilised as an energy source, but only some of the energy of motion can be extracted since the water must still move to extract the energy.

 

I appreciate your challenge to my ideas, and I want to understand what you mean about the energy already transferred to the water.

Can you explain that?

There are several reasons that validate the slowing of the Earth. Do you understand tidal acceleration? What creates the bulge to be ahead of the centerline between the Moon Earth? I believe slowing the movement of the waters will intensify this bulge this will mean the moon is pulled stronger. It will accelerate the Moon but the Earth, to conserve momentum, will be slowed.

 

If you don't believe me find out how much the Moon recesses today and multiply that by the age of the Moon. You will find the weird fact that the Moon should have moved away further than it has today. Why did the Moon not recess as fast in the past when the tides presumably were so much more intense, since the Moon was so much closer?

It is a big and unsolved problem IMO.

Edited October 12, 2014 by Robittybob1

[studiot]

Yes of course the Earth's rotation is slowing, measurably but slowly and the interaction betwen the orbiting moom and the Earth is in a large part responsible.

 

But the fact remains that the water belongs to the Earth and rotates with it.

Extracting tidal energy will not change this.

 

I do not have verifiable information about the history of water bodies on the Earth or the Moon on a geological timescale so cannot comment on your other idea.

[Robittybob1]

Yes of course the Earth's rotation is slowing, measurably but slowly and the interaction betwen the orbiting moom and the Earth is in a large part responsible.

 

But the fact remains that the water belongs to the Earth and rotates with it.

Extracting tidal energy will not change this.

 

I do not have verifiable information about the history of water bodies on the Earth or the Moon on a geological timescale so cannot comment on your other idea.

It is "wrong" to say the water rotates with the Earth. In some way the Moon pulling on the tidal bulge makes the water on the Earth spin some fraction slower than the Earth does. So that means as the Earth spins towards the east the bulge is being pulled toward the West so the net flow of water around the Earth should if my reasoning is right be a net current to the West (that is from the East to the West). Unfortunately this dragging could be offset by the net superrotation of the air currents. (The air currents on earth are very complex but I do believe there is a slight net westerly superrotation (That is from the West to the East.)

The Antarctic Circumpolar Current: The circumpolar current is driven by the strong westerly winds in the latitudes of the Southern Ocean.

 

There the wind effect is greater than the tidal pull which should be in the opposite direction.

In all the other oceans the land masses form a barrier to any overall rotation of the water. Big circulations are set up in each oceans, with the movements predominantly from the East to the West in the equatorial regions.

Edited October 12, 2014 by Robittybob1

[Externet]

Thanks.

Yes, horizontal currents in bodies of water created by changes in vertical levels from tides.

The massive insertion of turbines to extract energy from tidal currents cause slowing of currents and some corresponding warming of churning waters.

Natural obstacles as straits of Gibraltar, and north of Labrador, Denmark, Malacca and countless others have been doing it for millions of years just as if those massive bottlenecks were turbines extracting (electric) energy.

----> Has that energy dissipation been altering the earth-moon rotation and orbits since day one ?

I can see the planet with no shortage of energy in the future. Brutal engineering and costs needed to implement such extraction from tidal currents. Am sure some said Suez and Panamá canals were impossible to build also.

 

=================================

Edited. added:

Found "Tidal friction causes Earth days to lengthen 1.6 milliseconds/century. "

=================================

Edited October 12, 2014 by Externet

[Janus]

Yes of course the Earth's rotation is slowing, measurably but slowly and the interaction betwen the orbiting moom and the Earth is in a large part responsible.

 

But the fact remains that the water belongs to the Earth and rotates with it.

Extracting tidal energy will not change this.

Yes, it will. You have to consider the mechanism that causes the slowing of the Earth's rotation and the Moon's recession. Interaction between the Rotating Earth and the water forming the tidal bulge causes the Earth to drag the tidal bulge out of alignment with the Moon. It is this "tug of war" between the Earth dragging the bulge in one direction and the Moon trying to pull it aback into alignment, that transfers angular momentum from Earth to Moon.

 

If you add a device to extract energy from the changing tide, you are getting energy from water movement, this is done at the cot of that water movement. The end effect is that you are adding to the interaction that tends to drag the tidal bulge along with the Earth. This has the effect of increasing the misalignment of the the tidal bulge and Moon and increasing the rate of angular momentum transfer.

 

Granted, it will be a very very small increase, but a real one.

[studiot]

 

Constancy of Earth's Rotation

It was not possible to detect day-to-day differences in the period of earth rotation with the pendulum clock, but another fom of evidence based on extremely accurate observations of the moon, sun and the planets Mercury and Venus showed that the period of rotation gradually changes from year to year...............

 

......During the second half of the nineteeth century the rate of earth rotation steadily increased by more than 1 second per year, accumulating a total of about 40 seconds error; this trend was reversed in 1900 and the rotational rate began to decrease by the same amount per year. Again, in about 1920, the trend reversed. Because observations on the four bodies are in excellent agreement, there is no question that the earth has been changing its rate of rotation..............

 

...........On theoretical grounds, astronomers have calculated that the forces of tidal friction set up within the earth by the moon would ahve a braking effect of such a magnitude that the sidereal day should increase by 0.0016 seconds per century..............

 

......... The assumption that the earth's period of rotation continues to become longer because of tidal friction ahs been challenged in recent years. There is not disagreement among scientists that the earth began its existnece some 4 billion years ago, with a considerably shorter rotational period than now - probably as short as 10 hours. There is also no doubt that the braking action of the tides has caused the rate of rotation to become slower and the period of the day to increase to 24 hours.

 

The question is: Has the rotation now reached a constant average rate? : Source Professor Strahler Columbia University "The Earth Sciences"

 

Perhaps swansont has some more up to date data?

Edited October 12, 2014 by studiot

[Robittybob1]

 

Perhaps swansont has some more up to date data?

In that last quote you finish by saying "The question is: Has the rotation now reached a constant average rate? : Source Professor Strahler Columbia University "The Earth Sciences", And that is a very tricky question, for in one of the many hypotheses I have developed was the one where the rotation of a planet is affected by the Sun and the gas in its atmosphere. This was argued for several months but it was strongly disputed but I think it is still true, and I was reminded about it in this thread when I looked at the Antarctic Circumpolar Current, where they say that is powered by the strong westerly winds but don't explain what powers the winds to be always in the super-rotational direction.

 

So I can see it is possible to get to the stage where the acceleration from the Sun's energy balances the deceleration from the transfer of momentum to the Moon. But I don't think that has happened on the Earth as we don't have a lot of atmosphere left.

 

Extracting energy out of the Antarctic Circumpolar Current could be a real possibility, except its locality, thousands of miles from nowhere.

[studiot]

update

 

see post#4 here

 

http://www.scienceforums.net/topic/86036-earths-rotation/

 

Thank you swansont