Wind Turbines: Could the Earth Come to a Standstill?

Well I think first you must determine what is making the Earth spin....Then you could calculate the forces at work here...However, I think realistically that time will solve this problem for us...The time that it would take us to build any significant number of windmills, I think, would fall well beyond the time required for it's technological demise..

The earth's surface moves at about 1000 mph at the equator. The atmosphere, as a whole, moves at this same speed, assuming calm winds. The winds that power windmills are relatively localized, and for every east wind there is another going west (more or less) somewhere else. The energy for wind comes from the sun, not from the earth's rotation. As long as the sun shines there will be wind... and windmills.

Nuclear energy makes great sense, however. If only we were more rational.

You have to be careful to put the same number of windmills on the other side of the earth to balance it all (like counter rotating toilet flushes), otherwise the hair on my cows might fall off.

jjjohn

As long as you always have more than 300 standard trees per turbine per continent you can build them, since trees make the wind. 2 acres of grass = 1 standard trees. There are look up tables for other equivalents in Perrys Tree Huggers Handbook

Treeless, grassless continents can only support a few turbines (which explains why there are so few in Antarctica)

Wind turbines don't slow the wind, they don't speed the wind up and are less of a disturbance to the wind than the earlier mentioned trees. Nuclear power plants leave us with a waste product worse than any form of energy production in the world, and that waste product will be with us for thousands of years into the future.

Why not put the nuclear waste on a rocket headed to the sun

So we could all share in the joyous bounty that is nuclear waste when the rocket destructs in a sub orbital incident

We tried it the sun sued us.

Hilltopper please explain your science how can some thing that extracts energy from a system cause it to speed up?

How do trees make wind, by fluttering their leaves?

Ever heard of the butterfly effect?

That's a very dry joke, right? Otherwise, you'd have to explain how the 1200Kph winds on Jupiter are caused by trees on earth

Have you seen the people who live there?

Yes, I have seen them. Unfortunately, these twisted, windblown and cerebrally stunted creatures are unable to exist in the relative calm of the earth, and must create trouble wherever they go. So when they visit earth, they are immediately elected to congress.

!!

Oh, no need to worry, these 2 things are not comparable at all. A drop compared to ocean, even less, far far less. The earth's mass is too big for any such event to occur.......!

Some of you Guys really have to get a life

AMEN to that brother!

"Some of you Guys really have to get a life"

What do you mean get a life? Do you mean to say that there is actually something besides CR4.

That's blasphemy Nymoc46, wash your mouth out and then go and write down the following statement on the whiteboard the √c ÷ π times!

There is nothing but CR4, CR4 is everything, nothing existed before CR4 and nothing will exist after CR4. Anything else is just an illusion and the deranged ranting of a deluded mind!

I tried it it did not suit me.

I have submitted this question to the Stanford Research Institute, (SRI), for analysis and they have assured me they will have an answer in 87 months.

So just hang in there BrainWave and when I get the report I will forward it to you.

Thanks but just how much will it cost, I heard those guys only deal in seven figure numbers.

BrainWave you are to late it's April 8. not 1.

You all miss the point apart from wasting your time with question, I was wanting to inspire thoughtful comments. It is not that the turbines will directly slow the Earth by their own mass but rather the drag with in the atmosphere and the fact that the more energy we extract from the air the more it must interfere with the normal operation of the atmosphere. This could eventually cause even more global warming. No body seems to have thought it through in a rational way, so they just keep on planting these thing ad lib until my fears come true. Many other seamingly harmless things have come back to bight us sooner or later why should this be any different?

When we know it will all be far too late as usual.

yes; we must act quickly. Scientists have already noticed that Mars has been warming markedly for the last 30 years (really; look it up!); if we don't reverse our foolish ways, we'll warm the whole solar system...and beyond!

Global Warming on Mars? I swear i never drove a car on Mars that i can recall.

Remember those two rovers we sent there? REMEMBER THOSE!?!?!

And I think it's high time that the EPA starts seriously looking into spacecraft emissions; particularly those flourocarbon-heavy solid-rocket fuel emissions.

On the other hand, if we turn Mars into a comfortable destination, would that be so bad?

Ah! MG Rover went bankrupt last year.

It is not that the turbines will directly slow the Earth by their own mass but rather the drag with in the atmosphere and the fact that the more energy we extract from the air the more it must interfere with the normal operation of the atmosphere

Now You are right. There is an influence You are talking about. Air works like water in home gravity based heating system: absorbs heat from more hot areas (where is more sun) and transfers it to more cold areas of the Earth. And makes temperature distribution around the world more even.

Mountains, ocean waves, trees, even grass (therefore also wind turbines) work like a stone on inner walls of heating system pipes - decrease circulation speed. Effect of slowering will be like at home: Near equator will be more hot, near Poles will be more cold.

But because effective area of wind turbines, compared to surface of the Earth is small, their influence is also small, below 1E-6 compared to the rest. Difference between winter wind (no leaves on trees...) and summer wind is several orders bigger, than influence of wind turbines. Decision to worry or not is up to You.

Look on the bright side. As the earth slows down, with a standard 40 hour work week, we'll all have more free time.

but working hours will be longer also!

It's started. Remember that leap-second that was introduced on new-year's-eve a few years ago?

The next one should be added some 15.5 years from previous one. Good news for girls. Their official age will be lower than real.

The winds are driven by incident solar energy. - No problem.

There might be some minor, local weather effect, but we're simply
not big enough to cause a major change in weather patterns.

(The sky IS falling chicken little, but that ain't the reason.)

These weighty discussions are, in fact, dragging the earth to a halt.

And all this time I thought that SCREEEEEEEEEECH was the brakes on my neighbors car.

we're simply
not big enough to cause a major change in weather patterns.

By building wind turbines - yes. I agree with You. But otherwise, unfortunately we are!

Look at the forests cuttings off. This changes both local and global climate... and replaces forests by deserts, or agricultural areas. This has at least 1000 times bigger influence on weather than wind turbines.

This is one area with which I share common ground with the tree-huggers. I hate to see how much rain forest we're losing every year...what a criminal waste to lose so much just for cattle grazing ground!

Here we consider sex with trees a deviant behaviour that starts with hugging...you will be watched :)

What if it's consensual?

Only if the judge believes the tree's testimony....

and I always thought the stories about "knot holes" were pure fiction.

Physics says that m1*V1+m2*V2 +... =constant if there is no influence of external masses. . That means Earth mass + air mass has constant spin (almost). Moon is such an external mass. Earth's spin goes down (2000 year's day is longer 2.3msec then 1990year's day) due to Moon influence by making sea tides see:http://bowie.gsfc.nasa.gov/ggfc/tides/intro.html.

Wind really changes temporary earth's rotation speed. But this is not cumulative. What adds today takes back tomorrow.... The influence of wind turbines on earth rotation is not cumulative (sum of accelerations cancels sum of decelerations). Temporary change of earth's rotation speed dw/w caused by wind turbines is far below 1E-14 . For example 12-hour variation of rotation of earth caused by tides is of order of +-30us/12hour = 7E-10 = several orders more disturbing than wind turbines.

Oh my! I switched on an energy saving light bulb and felt the earth slow down.

As for trees and sex they can always turn over a new leaf.

You have got most sensitive accelerometer in the world. Apply for the Nobel Prize

I'm not contributing anything, just wanted to take a peek.

• ........(o) (o)........
• --000---O---000--

Brainwave is right guys, we should keep using coal.

And what about buildings??? Are bigger and with more hard surface, and can "stop" the wind too. If this is true, even the trees can stop the Earth by reducing the wind velocity and energy. I think that windmill may be a solution for zones with high velocity winds in order to reduce them and generate at the same time ©

Yes you are right this why the suffer when a big storm comes along and hits them for six. Tornado and hurricanes hit them hard. My question is not all daft if we depending on an ever increasing amount of wind energy a time will come when it must have some effect. The same with ever bigger taller buildings. Why else did God install tech-tonics and the earth quake? Time will tell the story of why I am right.

I fear some of our tom foolery has been at your expense, but this has been a great thread -- lots of clever fun. And you are right -- there are virtually always unintended consequences.

Have no concern my hide is thicker than that of a politician. I thought things had gone a bit flat and needed some life blowing in to proceedings. Nothing like a good mental joust.

Oh c'mon people; even if it does turn out that wind turbines cause problems (that our blowhard politicians can't replace themselves), there's a very simple solution:

We'll just use big coal and/or oil-fired engines to spin giant wind turbines to put some of the wind back.

!!! You're on a roll. You've brightened my day.

If we think that windmills can "stop" the wind, we can't use a generator powered by oceans waves...... it can stop our loved waves.

Imagine a world without waves, nobody surfing, all surfboard manufacturers unemployed!

You got me so damn jealous now I might just build that new fangled free energy device after all. Where are those blue prints, oh the dust. Better late than never.

I think turbulence behind the turbines will create localized low pressure areas actually increasing the rotational speed of the earth. Uh..............

Yes and no in theory they should act like screw propellers and make the earth speed up tow low pressure part is balanced by their drag coefficient. The whole surmise of the question is that unlike and air craft where you are using energy to do work here energy is being removed in the form of electrical power, so the bigger and more powerful the more energy removed from the atmosphere. Watts and all that, conservation of energy. Et Al.

Regardless of whether or not wind turbines do or do not slow the earths rotation, nobody has yet bothered to look at what would happen if indeed the energy we were getting did actually come from the Earths rotation.

Some time ago, in another thread, this was discussed and I actually calculated what would happen if we used the earths rotation to supply all our global energy needs. Without going into the calculation itself it showed if we did use the earths rotation to supply all our energy needs worldwide then we would ad 86.4 μs to the length of a the day each year.

Now the year stays the same length as this is governed by the earths orbit around the sun and is therefore not affected by the slowing of the Earths rotation. What this dose mean is that by the time all the nuclear waste we are generating at the moment has decayed and become completely safe we would no longer need to have leap years. Wow that's a really bad, we must never use the earths rotational energy in such a wasteful way.

Seriously though, the effect would be minimal and while detectable with atomic clocks that are accurate to umpteen decimal places most people would never notice. We may need to recalculate the celestial navigation tables and ditch the occasional leap year after a hundred millennia or so but I can't see it being anything like as bad as warming the Earth by 3-6°C in a century or so.

While the rotation of the Earth has the capacity to do work, harnessing that capacity is another thing altogether. For that, one needs a reference point, probably one that is fixed relative to the Earth's orbital radius around the Sun, against which to do work. And it just isn't available. So she just keeps on spinning. As rotation in 'frictionless' bearings goes, Earth is a pretty good example.

We need to just do the math:

KE=½I♥²

Where KE equals rotational kinetic energy, I equals inertia, and ♥ equals Love. Clearly, because it's squared, the single biggest factor is...

Uh oh, the world is in trouble...

How about building a tower to the moon?

Build it on a rail car. The track around the equator. Generators on the wheels. ...or better yet, Mag-Lev and linear generators.

I like the idea of eliminating leap-years.

Gordie.

I'd be concerned that as we slow the moon, it would come crashing down, into us.

How about how about a tower that would reach into the orbit of Mars? At the top of this tower, we'd have a flapper that would wind a spring against ratcheting latch. Each collision would wind up the spring, and in between collisions we'd use the energy stored in the spring. Something like a toy wind up car, with its motor expanded by 10¹⁸. We'd need a very large hole in this tower for the occasional passage of Venus, of course.

Then, when Mars slows too much and gets sucked into the sun, it's less likely to take us with it. There is, of course, the small matter of our own speed around the sun being slowed with each collision. And each collision would have a terribly disturbing effect on our day length.

"We'd need a very large hole in this tower for the occasional passage of Venus, of course."

Correct me if I am wrong but I was under the impression that Venus was closer to the Sun than both Mars and Earth. That would make it fairly difficult for it to hit the mast between Earth and Mars.

"There is, of course, the small matter of our own speed around the sun being slowed with each collision. And each collision would have a terribly disturbing effect on our day length."

This may sound strange but as an orbit decays it actually speed up, not slow down. It all has to do with the total energy but as you fall from a higher orbit to a lower one you speed increases rather than decreases. The loss of energy all comes from the potential energy part of the equation not the kinetic.

Correct me if I am wrong but I was under the impression that Venus was closer to the Sun than both Mars and Earth. That would make it fairly difficult for it to hit the mast between Earth and Mars.

As far as I know, you are right regarding the relative positions of the rocky planets. However, I envision this tower as being knocked around a bit in each collision, not unlike a tennis racket being knocked back by a fast moving ball, if the racket were loosely held. So, at times this tower will rotate around earth on its equatorial track, and given that Earth is further from Mars than Venus, it seems polite to provide a hole for Venus's passage. A reasonable person might argue: "Wouldn't it be better to simply control the tower with rockets, so that collisions could be avoided or encouraged at will?" But then a more reasonable person might argue, "Isn't this already impossible ludicrous?"

This may sound strange but as an orbit decays it actually speed up, not slow down. It all has to do with the total energy but as you fall from a higher orbit to a lower one you speed increases rather than decreases. The loss of energy all comes from the potential energy part of the equation not the kinetic.

That doesn't sound strange at all. However, the effect that generally precipitates an orbital decay is drag. I'd expect that if we wanted to send Earth into the sun, we'd want to slow it rather than speed it up. Speed it up enough, (to escape velocity) and it will leave the Sun permanently, true?

Hi Ken & others,

I was about to pipe up with the fact that the glider that I used to fly was solar powered but you beat me to it. Currently the longest single glider flight is 2463 Km in Argentina but I am unsure if this holds the official record. As far as I can see the current world record is a flight in New Zealand of 2,049 Km where a pilot flew the length of both islands twice including a double crossing of Cook Straight in a single flight. There is also a claim for a flight in New Zealand of 2,569 Km but this is also unconfirmed.

These are all flights in what is an atmospheric wave, formed when wind strikes a large mountain ranges and is deflected upwards. This deflection can then create an instability that causes a series of oscillations in the atmosphere. You can sometimes see this when rows of clouds form running parallel to mountain ranges. The rows of clouds correspond with the crest of each of the waves and the affect can continue for hundreds of kilometers downwind of the mountain range.

There are also record flights that have been made in Australia of over 1,000 Km but using thermals to gain height rather than atmospheric waves. Thermals are caused when a parcel of air is warmed by a hot spot on the ground. As the parcel of air rises it cools at a rate of 3° C per 1,000 feet that it rises. If the atmospheric conditions are such that the atmospheric temperature reduces at less than this the parcel of air will continue to rise till it reaches a point that the atmospheric temperature is equal or warmer.. If the air becomes saturated as it rises then a cloud forms and the resultant heat released warms the air even further. As a result moist air only cools at around 1.5° C for every 1,000 feet. This can create an even stronger vertical movement and causes the cloud to build.

In the deserts in central Australia, where the air is extremely dry and overnight temperatures can drop below zero, you can get these thermal rising with vertical speeds of up to 30 Km/h and sometimes more. They can rise to altitudes of up to 20,000 feet and when you consider that glide ratios of most modern gliders is better than 30:1 to 50:1 you get a range of 200-300 Km from each thermal. If you can't find another thermal within 200 Km then you aren't looking very hard. Basically the limiting factor is the amount of time the sun shines.

"I'd expect that if we wanted to send Earth into the sun, we'd want to slow it rather than speed it up. Speed it up enough, (to escape velocity) and it will leave the Sun permanently, true?"

If you wanted to crash the earth into the Sun it would actually be going faster just before impact than it currently is. Lower orbits have higher orbital velocities.

The same thing happens with a satellite in orbit and this is where things really get weird. If you fire a retro rocket to slow a satellite down it actually speeds up as the orbit decays and it moves to a lower orbit. If you fire a rocket and try and speed it up it moves into a higher orbit and slows down. In other words the acceleration that the satellite undergoes is in the opposite direction to the force that is applied to it by the rocket.

Weird eh what?

It's all very complicated and you can read and see how confusing it can get in the thread Solar System Kinetic Energy Problem where Roger, Jorrie, myself and others played with it for some time before convincing ourselves that we understood what was going on.

To start a glider you need energy, it is impossible to start from ground level, just using wind and thermals.

Gliders are also not interesting for transport.

It is a like the Hydrogen technology: it is perfectly possible to power a 40 ton truck with hydrogen fuel cells and enable it to drive 1000 km in one run.

Only one little problem: your payload will be the driver. The rest is taken by the hydrogen storage.

You're mostly right, but gliders have been used extensively for transporting troops silently behind enemy lines, and other such covert purposes. Similarly, hydrogen fuel works pretty well to fling big, heavy things into space.

It's always a matter of designing the system to the need. There are those who adamantly claim that pneumatics are inefficient; but not when they work better than anything else!

You are right: depending on the application it might the best/only solution, the gliders in WW II were a solution to cope with the lack of engines.

Which percentage of the total spacecraft take off weight is fuel? up to 85%

For normal economic applications we must find a way to do this differently.

To my opinion we will be using oil based fuels for transportation for a long time.

To start a glider you need energy, it is impossible to start from ground level, just using wind and thermals.

Impossible? Mighty strong language!

One simply tethers the glider facing into a 50 knot wind, such as you can occasionally find atop some high mountains. Once the glider has attained 500' above ground level, (flying as a kite) the pilot releases the tether. If the pilot does nothing else, the glider will start accelerating rearward (relative to ground) and its airspeed will rapidly decay (emulating a kite with cut string). To maintain airspeed, the pilot lowers the nose, using gravity to increase speed (trading altitude for speed is the phrase used). The first several such experiments will likely result in contact with ground, but eventually some intrepid and skilled pilot will be able to clear the edge of the mountain, and then endlessly soar the ridge -- provided, of course, that the weather cooperates (which it rarely does.)

My friend would launch from a mountain (on which he lived) with his wife driving the Jeep. This (and winch launches even more so) would give me the Willys (arrgh!) because you'd be putting a lot of faith in the release mechanism. At least with an airplane tow, if the release fails, you have a large time window for fiddling, and you can always land still in tow. I think Masu can confirm, however, that these release mechanisms almost never fail.

Birds are impressive flyers. Something I love to watch is the ability of some birds to hang motionless in space, as if tethered (like a kite). Without any flapping, they can hold position by gliding in a slightly rising wind (as near a beach dune), perfectly balancing the vectors.

"At least with an airplane tow, if the release fails, you have a large time window for fiddling, and you can always land still in tow. I think Masu can confirm, however, that these release mechanisms almost never fail."

A release failure is a very rare event and whilst it is discussed during your training it is not a practiced maneuver. It is deemed that trying to do a landing with the glider still attached is far too dangerous to practice and so rare that by training we would be causing more accidents that would be prevented.

There is also a release mechanism in the tow plane so in the event of the release failing at the glider the tow plane can release it from that end. There is also a weak link at the tow plane end that can be broken fairly easily. I have broken it once when practicing the maneuvers that you go through when you have a release mechanism failure.

"Birds are impressive flyers. Something I love to watch is the ability of some birds to hang motionless in space, as if tethered (like a kite). Without any flapping, they can hold position by gliding in a slightly rising wind (as near a beach dune), perfectly balancing the vectors. "

It's not as difficult to do as one might think. If the wind hits terrain that causes it to be deflected upwards it can trigger an oscillation that causes waves in the atmosphere. The trick is to set the glider up so that the addition of you velocity and the wind causes you to track along the windward side of one of these waves, where the air is rising. If you play around for a while you can sometimes get it to add up to a zero ground speed and you appear to hover over one spot on the ground.

Wave soaring as it is called can be a lot of fun but you need to be especially careful when doing it. The problem is that you normally track back and forwards along the leading edge of the wave so you ground track periodically reverses. If there is another glider in the same wave you will end up on a converging track. With two aircraft closing on straight tracks and constant speed there is no angular motion between the two aircraft, in other words the opposing aircraft will appear stationary with respect to each other. The result is with closing speeds of 150 Km/h plus you don't see each other until about 2 seconds before impact. From a pilots point of view what appears to be a stationary fly spec on the canopy suddenly grows into an aircraft coming the other way about 2 seconds before you collide. It makes collision avoidance very difficult and one of the big problems with flying gliders in mid air collisions. Recently however a system has been developed that utilizes a GPS receiver in each glider and a short range transmitter and receiver. Each glider transmits it position and a vector that represents its heading and velocity in 3 dimensional space. Any aircraft in the vicinity then compares this with its own vector and if two aircraft look like getting too close an alarm is sounded with a visual indication of the direction the opposing aircraft is coming from. So fare it seems to have prevented collisions but unfortunately the system dose not yet work when aircraft are thermaling in what is referred to as a gaggle because they are all going round in circles. I understand that there are plans to update the software to work in this mode but I don't know the status of that yet.

I have only ever had one near miss but a fellow pilot at my club has been involved in two mid air collisions. The first one he managed to bail out before the aircraft impacted the ground but in the second one the wing of the opposing aircraft went through the cockpit killing him instantly. His aircraft then went into a spiral dive and impacted the ground almost vertically traveling at somewhere around 400 Km/h. The altimeter was found nearly 100 m from the point of impact and the nose hook was over 3 m down in the ground.

You can start glider rolling it down from the hill.

You can burn H2 in a rocket engine attached to glider. 20kg engine and 1kg of Hydrogen would be probably enough to get 500m in 15 seconds. Only that noise... doesnt suit to glider.

..on Second World War thousands of gliders were used for transportation purposes..

It is possible to make 800kg glider carrying >800kg load. Airplane built to fly around the world was very like a glider. Having some 800kg of its own mass and carrying >2000kg of fuel. So for more short distance it could have payload> own weight.

It's all very complicated and you can read and see how confusing it can get in the thread Solar System Kinetic Energy Problem where Roger, Jorrie, myself and others played with it for some time before convincing ourselves that we understood what was going on.

If you actually read that thread, you'll see that I pulled you, kicking and screaming all the way, to the conclusion that the ratio of planetary kinetic energy to potential energy is .5, regardless of orbital eccentricity. See, for example, Jorrie's post 48, my post 84, Jorrie's post 86, my post 91, and Jorrie's post 93.

In other words the acceleration that the satellite undergoes is in the opposite direction to the force that is applied to it by the rocket.

You seem to be arguing that when the retro rockets are fired, the response of the satellite is to speed up. This would be a surprise to astronauts, I think. While it is true to say that pulling on a bow string eventually causes an arrow to accelerate, it is misleading to say that pulling on a bowstring makes the arrow accelerate forward. Rather, the arrow gently accelerates rearward, then slows to a stop, and only after the release, does it accelerate forward. Your statement that the acceleration that a satellite undergoes is in the opposite direction to the force applied makes the physics seem much weirder than they really are. Newton still rules for many happenings in space.

Having never having been in space I can't testify on the exact sequence of events. Regardless of the sequence if you fire retro rockets that try and decelerate the space craft the craft will end up in a lower orbit but going faster. The exact opposite is true if you try and speed the craft up you will ultimately end up in a higher orbit going slower.

I don't know the exact sequence though. There are two possibilities that I can see:

1. Initially you speed decreases or increases according to the force being applied by the rockets and then after the firing has concluded the craft then moves to the new orbit and the speed changes accordingly.
2. As you fire the rocket the speed and orbit change simultaneously and continually with the craft ending up in the new orbit the moment that the rocked finished firing.

If it is the second then the craft will appear to accelerate in the opposite direction to the force that is being applied to it. If the first is true the there will be an initial acceleration in the direction of the thrust from the rocket then a period of change as the new orbit settles out.

I think, or then again maybe not and I could have it completely wrong and as usual have it all arse up.

Is there anybody out there from NASA or somewhere else that can tell us what really happens and the sequence of events when you fire rockets to change your orbit?

Is there anybody out there from NASA or somewhere else that can tell us what really happens and the sequence of events when you fire rockets to change your orbit?

See link in post 99.

It is not a series of events.

As you start to slow down the sattelite, the total energy of the system lowers.

The sattelite will start loosing heigth and gaining speed in the direction of the gravitational center of the earth = the axial speed. (forget the moon for a while)

The radial speed will go down.

As long as you fire the rocket, the radial speed will keep going down.

From the moment that the sattelite started to go towards the earth, the axial speed will go up. The ratio is depending on the radial speed and heigth.

The sattelite will never speed up again in the radial direction, there is nothing that pulls in that direction. All the potential energy will be transformed to axial speed. The total energy level will remain.

It is not that complicated you see, just don't mix up the directional vectors.

It is not a series of events.

It is not a series of events only if we stop time.

If we view changing orbit radius as one event, then it leads to statements like Masu's:

In other words the acceleration that the satellite undergoes is in the opposite direction to the force that is applied to it by the rocket.

This would make Newton squirm.

Larger orbits are slower. But getting to a larger orbit requires speeding up. Twice, usually. To start, the spacecraft fires posigrade rockets to increase tangential* speed, making the orbit eccentric. This is usually considered an impulse in the overall scheme of things: i.e., it happens at a point on the original orbit. The spacecraft takes off on a tangent into an eccentric orbit which will meet the desired orbit also at a tangent. When it arrives at the new orbit, it is going slower (closer to the new orbit's natural speed) because the gravity vector in an eccentric orbit is not perpendicular to direction of travel (and causes speeding up and slowing down). In fact, by the time we reach the new orbit, the slowing has been enough to require another posigrade burn to shove the craft into the new, circular orbit.

Speed up twice... end up going slower.

A pretty simple, but good explanation is here. A little more detail is here.

*BTW, I think when you say radial, you mean tangential, and when you say axial, you mean what I would call radial -- in other words in line with a radius. When I hear axial, I think "in line with an axis of rotation" -- a line through the earth's poles, for instance.

Good response. Thank you.

Top link Ken, thanks for posting it. I havn't read it yet but I will over the next day or so.

Beg pardon: if the Moon were slower, its orbital radius around the Earth would be greater. Sorry.

What you say makes sense. In other words, larger orbits have slower speeds. But changing to a lower orbit requires first slowing down, making the transition, and then speeding up. Consider this, from this site that deals with orbital maneuvers:

When transferring from a smaller orbit to a larger orbit, the change in velocity is applied in the direction of motion; when transferring from a larger orbit to a smaller, the change of velocity is opposite to the direction of motion.

(This applies to the first change in velocity.)

One can imagine a thought experiment in which one quickly decelerates a satellite to a "stop". Gravity (the centripetal force causing orbits) would then pull the satellite straight into the attracting body.

An obvious way to get to a higher orbit is to accelerate to escape velocity, true?

an object in orbit has exactly the escape velocity for that orbit.

If you want to move it up, you need to add some speed in the Axial direction, so that it moves away from the earth, and slow the object down so that the radial speed matches the new orbit.

an object in orbit has exactly the escape velocity for that orbit.

LIES!! You are trying to get us all killed!

Actually any change in circumferential speed will put us into a different orbit, but any increase in speed will not cause us to "escape", i.e., go "flying off into space." The escape velocity (which is really a speed, not a velocity) is 2^.5 (i.e., about 1.414) times the orbital speed.

Compare the escape velocities of the planets as presented in the chart in Wikipedia with the orbital speeds as presented in the links to each planet from this page.

Beam us up, Scotty!

Surely the usual problem with communications, rather than lice or fleas. The proper statement (equivalent to what you write, and easy to misremember) is that adding kinetic energy that is equal to the orbital kinetic energy gives the escape velocity.

Fyz

Or I suppose you could say, "If you want to knock something out of the solar system, give it a good whack with a cosmic golf club, to double its kinetic energy."

Yes - and that's easy to remember. However, I don't play astronomical golf. If I did, I suppose my objective would be to get the satellite INTO a hole - and I wouldn't expect to live long enough to find any suitable holes outside the solar system

Fyz

Brainwave, I think you need a brain scan . . .

I had one not so long ago they said nothing to worry about, my brain was in good working order. It's official my mental faculties are all ok. So there now you know.

A standstill relative to what?

Standstill relative to the Moon will eventually happen as the Moon moves further away from the CoG of the Earth/Moon system. Turbines may have an influence as tides and wind are inter-related.

Standstill relative to the Sun would have the consequence of accelerating towards it to absorption. Standstill relative to the fixed stars would mean the Earth leaving Solar orbit. Such forces would probably disintegrate it, so any link to wind turbines is probably nonsensical.

Well there is no harm in asking, is there? You have all had a nice dig at my expence but I can take it. After all you don't know until you ask. My theory could be right I am very rarely wrong in my thinking. Time will tell.

There is a lot of posts and all were not read. i beg for forgiveness if i am repeating something.

Question "will wind turbines stop the rotation of earth" No not easily - you will at least have time to listen to a looooooot of CD's.

Question - will the turbines stop the wind - No, The wind blows because ther are pressure differences and the air moves in a circular path to fill this "space". As long as this variations in pressure exist the air will move.

analog to this:

In South Africa an irrigation canal system were developed after WWII. Because of the lack of electricity the farmers installed water wheels in the canal for household power generation. (the bottom pedal touching the water)

The flow is restricted slightly resulting in backing up the water slightly resulting in a greater pressure gradient with faster flows. End result negligible.

Don't take life or any of this too seriously Hendrik it is just a way to get people thinking about the bigger picture and bring about some ideas as what is really going on with our global weather. All good ideas must pass the ridicule test first then mature into a good joke after witch they become folk-law then accepted fact. I thought at the time it was a slow day and needed some stimulation. so much has been talked of global warming and how wind would save our bacon but no thought given as to how this might one day come back to bite us all. It is all speculation for now but who knows where it will land us in the future science fiction seems to come true after enough time has been allowed to pass. "The day the Earth stood still" of course we all know that was just a silly film but just suppose it were to happen and the things that would follow from the possible panic amongst the people as they slowly roasted or froze. Don't lose sleep it may never get that bad. Some nasty alien life form could have sneaked up on us all and exterminated all life on earth before then.

There is a school of thought that feels that there is intelligent life in the universe, and that it has used Earth as its loony-bin.

So say some and who am I to disagree. There are certainly more loonies now than ever before I do believe it has some thing to do with the amount of alcohol consumed topped up with the prevalent use of other substances well left alone. Wacky backy, and china white, rocks etc.

Have we entertained you? I do hope so. The serious message is everything has an unknown element to it.

Yes, it's been fun. And I agree, the unknowns often outnumber the knowns.

Hi Brainwave,

this is a nice one, The only effect I can imagine from windmills is that it will get colder on earth as wind energy, which normally returns to heat by friction, will be converted to electricity.

Wind originated in heat and will return to heat. The only effect the earth rotation has is on it's direction as the earth has a different speed on different latitudes.

But I loved the conclusions made by others here.

Pretty much all the electrical energy also ends up as heat as well. The only part that doesn't is radio transmissions in the VHF and higher frequency where something less than half of the radiated signal leaves earth and heads off into space.

So, what will be the effect of wind turbines on the energy level of earth?

None.

"So, what will be the effect of wind turbines on the energy level of earth?"

All you are doing is converting the kinetic energy of the wind to electrical energy so like with everything else there is no net gain or loss of energy. The question then becomes what would be the effect of removing the kinetic energy from the atmosphere and converting most of it to heat. Actually heat is also kinetic energy as well so there is no real change with the exception of the energy that is radiated into space.

I suppose that the slight increase in the energy being radiated into space would mean a very slight net cooling affect but it would be very minor. Somebody might like to do the calculation how much energy would actually be lost to space.

Globally our total energy consumption is about 500 Zj per year so has anybody got any idea what removing that amount of kinetic energy from the atmosphere would have?