# Thread: Is planet earth shrinking?

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## Is planet earth shrinking?

Imagine the measured distance planet earth-moon, which is growing about 3.8 centimeters a year, is not equivalent to a theory that the moon is going away, but planet earth may just be shrinking in the same way (or maybe a combination of these two movements).
In fact, we know the expansion of the mid-atlantic ridge (about 14 cm per year). But do we know the change in the subduction zones of the continental drift as well? If subduction exceeds the expansion, we`ll have a shrinking planet. How about measuring the equator once in a while, or does this take place already?

2. Assuming for a moment that the volumetric size of the earth is not readily ascertained, where do you propose the extra mass being subducted goes? Compressed in the mantle?

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Why not. We know from SMBH that mass can be compressed. We have planets (and even elements) with different density, although they have same size (or volume). So...?

4. Originally Posted by Relative
Why not. We know from SMBH that mass can be compressed. We have planets (and even elements) with different density, although they have same size (or volume). So...?
This by itself does not tell us whether or not any of them are shrinking, or are capable of doing so.

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I think GPS precision rules that out.

ETA: note that decreasing the volume of a sphere will not change the orbits of satelites, they will steadily increase in height. (Technically the earth isn't strictly a sphere, and doesn't have uniform density, but decreasing by 4cm/year would still over time provide a discernable effect within GPS error bounds).

ETA: actually, we'd see all our satelites (not just the moon) increase in height by 4cm/year, this is not seen.

6. Originally Posted by Relative
Imagine the measured distance planet earth-moon, which is growing about 3.8 centimeters a year, is not equivalent to a theory that the moon is going away, but planet earth may just be shrinking in the same way (or maybe a combination of these two movements).
In fact, we know the expansion of the mid-atlantic ridge (about 14 cm per year). But do we know the change in the subduction zones of the continental drift as well? If subduction exceeds the expansion, we`ll have a shrinking planet. How about measuring the equator once in a while, or does this take place already?
Suppose we had a shrinking Earth with the Moon's orbital radius remaining constant. If that were the case, then the Earth's spin would be speeding up over the long haul, rather than slowing down as it actually does. That is the same conservation of angular momentum that causes a spinning skater to speed up as she pulls her arms in.

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First of all, I´m not sure wheter the moons radius may be constant or not. Since everything is in motion, it would be an unbeleivable wonder, if it was. Second, don`t forget "expansion of the universe". If this theory is true, it might affect the system earth-moon as well. So acceleration of angular momentum could be braked. Third, if space is not totally "empty", slowing down of planet earth may also have other causes. Fourth, the opposite way of assuming the moon would have prompted earth´s slowing down leads to an non-solutionable model. Fifth, also a "stationary" moon orbit could have caused planet earth to slow down - against the acceleration due to angular momentum. Sixth, a mass-corresponding amount of energy could have leaved planet earth (in the process of "cooling down"), so an acceleration due to angular momentum might not occur...

8. Originally Posted by Relative
First of all, I´m not sure wheter the moons radius may be constant or not. Since everything is in motion, it would be an unbeleivable wonder, if it was. Second, don`t forget "expansion of the universe". If this theory is true, it might affect the system earth-moon as well. So acceleration of angular momentum could be braked. Third, if space is not totally "empty", slowing down of planet earth may also have other causes. Fourth, the opposite way of assuming the moon would have prompted earth´s slowing down leads to an non-solutionable model. Fifth, also a "stationary" moon orbit could have caused planet earth to slow down - against the acceleration due to angular momentum. Sixth, a mass-corresponding amount of energy could have leaved planet earth (in the process of "cooling down"), so an acceleration due to angular momentum might not occur...
And do you have any evidence to support those contentions? Especially given that that the planet is covered with artificial structures, some of which are thousands of years old and none of which display any signs of such a global contraction?

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Originally Posted by caveman1917
I think GPS precision rules that out.

ETA: note that decreasing the volume of a sphere will not change the orbits of satelites, they will steadily increase in height. (Technically the earth isn't strictly a sphere, and doesn't have uniform density, but decreasing by 4cm/year would still over time provide a discernable effect within GPS error bounds).

ETA: actually, we'd see all our satelites (not just the moon) increase in height by 4cm/year, this is not seen.
If really so, this would mean that the earth´s diameter hasn`t changed at all since satellites have been launched to measure it. I can hardly beleive that, since that then would be the only constant in the universe... What if these machines could not detect the difference, as they were coming from our planet, so their angular momentum is connected to ours by means of origin?

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Originally Posted by Garrison
And do you have any evidence to support those contentions? Especially given that that the planet is covered with artificial structures, some of which are thousands of years old and none of which display any signs of such a global contraction?
Actually, I don`t have - otherwise I woudn`t share this idea with you but publishing it in a science paper.
In the 1950s there even was a theory, that planet earth was expanding, shortly after people noticed the continetal drift. (Continental drift, by the way, is the answer to your question. Even if there are structures, that are thousand of years old, we still have earth quakes, vulcanoes and that drift, which hasn`t stopped yet.)
Some years later, the theory of expansion of planet earth had been abandonned. But if you go to http://en.wikipedia.org/wiki/Expanding_Earth
you will also find a sentence that says "Measurements suggest that, on very long timescales, the Earth is slowly shrinking, due to thermal contraction."
So, at least, my idea seems to be not so far off...

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Relative,

If just the Earth is shrinking that would be one hypothesis. If the Earth and moon are both shrinking that's another hypothesis. If all planets and moons shrink or some combination thereof, then that's another hypothesis. If all matter including the Earth is shrinking that's again another hypothesis. In this model of yours it seems that you are simply proposing that the Earth but nothing else is shrinking, right? But if any shrinking is related to thermal contractions then many other or all planets and moons might also be shrinking, right?

12. Originally Posted by Relative
Actually, I don`t have - otherwise I woudn`t share this idea with you but publishing it in a science paper.
Relative,

If you have not done so, I would strongly urge you to review The Advice for ATM Advocates. Among other points covered in it, is that you are expected to defend your ATM idea with evidence, and that ATM is not for the development of your idea, nor for wild speculation.

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Originally Posted by Relative
Imagine the measured distance planet earth-moon, which is growing about 3.8 centimeters a year, is not equivalent to a theory that the moon is going away, but planet earth may just be shrinking in the same way (or maybe a combination of these two movements).
In fact, we know the expansion of the mid-atlantic ridge (about 14 cm per year). But do we know the change in the subduction zones of the continental drift as well? If subduction exceeds the expansion, we`ll have a shrinking planet. How about measuring the equator once in a while, or does this take place already?

If the above were true, you would have to have a shrinking that retains the quadropole form of the Earth geoid, otherwise all the atomic clocks so perfectly synchronized by NIST would go out of synchronization. What proof do you have for this very strange shrinking?

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Originally Posted by forrest noble
Relative,

If just the Earth is shrinking that would be one hypothesis. If the Earth and moon are both shrinking that's another hypothesis. If all planets and moons shrink or some combination thereof, then that's another hypothesis. If all matter including the Earth is shrinking that's again another hypothesis. In this model of yours it seems that you are simply proposing that the Earth but nothing else is shrinking, right? But if any shrinking is related to thermal contractions then many other or all planets and moons might also be shrinking, right?
Sure. I didn`t state planet earth might be an exception.
If we consider planets have been formed from interstellar material, there obviously WAS a shrinking process in the beginning. When should this have come to an end? At a certain equilibrum? Maybe yes, if there is no activity in the planet`s core any more. But our planet still exhibits thist. If fusion processes are existing in the center, some haevier elements might also provide an increasing density. So, what about the space that is gained therefore (besides thermal contraction)?

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Originally Posted by Relative
If really so, this would mean that the earth´s diameter hasn`t changed at all since satellites have been launched to measure it. I can hardly beleive that, since that then would be the only constant in the universe...
Other than all the others. There are twenty odd in the Standard Model alone and no evidence that they have all changed. There is a tiny hint (not confirmed, not very certain) that there have been tiny changes in alpha but so far that is about it.

And on post #9. You would therefore be suggesting some magic effect where all objects that originated from the Earth had some spooky link that meant that angular momentum just bled off so that your measurements came out right? How would that even work? How is that reconciled with the fact that we all come from one gas cloud which came from one larger gas cloud and so on back to the Big Bang? Is there some limit where this effect breaks down? I am sorry but you seem to be hastily adding post-hoc ideas without adequate support.

Could you show how much heat energy would have to be lost to conserve angular momentum by the way? You need to check that these things are feasible (order of magnitude) before you propose them and post that reasoning with your claims.
Last edited by Shaula; 2010-Dec-16 at 10:09 AM. Reason: Changed last post to #9 to make it clearer

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Concerning the argument of GPS and atomic clocks:
Our GPS Satellites are not orbiting "freely" like the moon, aren`t they? I guess, slight corrections are made once in a while to keep them on their (calculated!) path. So, if we discover, it is going away from earth, we will fire a jet to bring it back to its position relative to earth. So, will this device be able to notice a shrinking at all? (at Shaula: This was, what I was meaning, sorry. Of course, you are right otherwise...)
We even don`t know exactly yet, how the gravitational influence on the time on board of a satellite is. Or for the signal travelling from ground to the satellite and back. To notice a difference in the order of 1^-10 compared to earth`s radius, we need a respective accuracy.
We know the mass of our planet accurate to 3 decimal places only. So how do we intergate the gravitational effect on time in the calculation of distance using GPS accurately?

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Originally Posted by Relative
Concerning the argument of GPS and atomic clocks:
You can't lump the stationary atomic cloicks and the GPS ones together, please answer each question separately.

Our GPS Satellites are not orbiting "freely" like the moon, aren`t they?
Actually, they are. You need to check your facts before you make assertions.

We even don`t know exactly yet, how the gravitational influence on the time on board of a satellite is.
Actually, we do. Check your facts.

18. Originally Posted by Relative
Actually, I don`t have - otherwise I woudn`t share this idea with you but publishing it in a science paper.
In the 1950s there even was a theory, that planet earth was expanding, shortly after people noticed the continetal drift. (Continental drift, by the way, is the answer to your question. Even if there are structures, that are thousand of years old, we still have earth quakes, vulcanoes and that drift, which hasn`t stopped yet.)
Some years later, the theory of expansion of planet earth had been abandonned. But if you go to http://en.wikipedia.org/wiki/Expanding_Earth
you will also find a sentence that says "Measurements suggest that, on very long timescales, the Earth is slowly shrinking, due to thermal contraction."
So, at least, my idea seems to be not so far off...
And can you demonstrate any connection between the above and your theory? You see you not only lack supporting evidence for your theory but the available evidence actually contradicts it. And you have you bothered to go beyond Wikipedia and find out the degree of thermal contraction and what is meant by long timescales to see if it actually fits in with what your suggesting?

19. Having done some number crunching*, I find that the rotation period of the Earth would be shortened by about a millisecond if the radius shrinks by 4cm. If that happens in a year that would be roughly 100 times as much as the long term slowdown rate that actually is observed and attributed to the tidal interaction with the Moon. In other words a shrinking of so much as a millimeter would be enough to overpower the tidal drag and cause our planet to spin up rather than down.

I have concluded that the measured increase of the surface to surface separation of the two bodies reflects an actual center to center increase, and not any significant shrinking.

*Formula for angular momentum of spinning solid sphere of mass M and radius R, with angular velocity ω:

L = 0.4MR2ω

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Originally Posted by Relative
Sure. I didn`t state planet earth might be an exception.
If we consider planets have been formed from interstellar material, there obviously WAS a shrinking process in the beginning. When should this have come to an end? At a certain equilibrum? Maybe yes, if there is no activity in the planet`s core any more. But our planet still exhibits thist. If fusion processes are existing in the center, some haevier elements might also provide an increasing density. So, what about the space that is gained therefore (besides thermal contraction)?
Seemingly no possible fusion processes in the Earth's core, possibly minor fission processes, but theoretically there is still isotope decay that supposedly creates decreasing heat in the Earth's core. This could cause the Earth and all the planets to possibly shrink to a minor extent over a great deal of time. Measurements sometime may prove your idea to be correct, but if so my guess would be that again we are only talking about a relatively minuscule effect that seemingly would be of no major importance concerning the overall understanding of the Earth or planetary system.

21. A quick calculation suggest that if the flow of heat from the core is about 42 terawatts and say 80% of this comes from radioactive decay, this corresponds to a loss of mass of about 35 kg per day. As the earth accumulates something like 4 tons per hour from space dust, this loss through fission is less than negligible.

22. Originally Posted by Strange
A quick calculation suggest that if the flow of heat from the core is about 42 terawatts and say 80% of this comes from radioactive decay, this corresponds to a loss of mass of about 35 kg per day. As the earth accumulates something like 4 tons per hour from space dust, this loss through fission is less than negligible.
The vast majority of radioactive decay occurring in the earth's interior is not through fission, but through alpha and beta decay.

23. Originally Posted by geonuc
The vast majority of radioactive decay occurring in the earth's interior is not through fission, but through alpha and beta decay.
Fair enough. I assume that doesn't change the numbers though.

24. Originally Posted by Strange
Fair enough. I assume that doesn't change the numbers though.
Shouldn't think so.

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Originally Posted by macaw
You can't lump the stationary atomic cloicks and the GPS ones together, please answer each question separately.Actually, we do. Check your facts.
So, you state that there might be a difference between stationary clocks and those orbiting. Otherwise you won`t blame me to lump them. So, can we do reliable distance calculation then, if we have two different systems? Another thougt experiment: If the distance between two GPS satellites in the orbit is measured, and the signal between the two of them is influenced by gravitaion, i.e. the two "ends" of the signal are influenced less then the curve (not a straight line) inbetween them, how do we know, how far they are away from each other exactly?
Originally Posted by macaw
Actually, they are. You need to check your facts before you make assertions.
Ok, I assure, I`ve never heard from satellites falling to earth, because we weren`t able to make corrections in their orbit. I must admit, that GPS orbit corrections are not made by firing a jet but via rotating plates. Excuse me. But so, these satellites are NOT freely orbiting.
Originally Posted by macaw
Actually, they are. You need to check your facts before you make assertions.
In fact, we are still quite unsure. There have been test with pilots in a jet compared to ground, still quite inaccurate, but this is nothing in comparison to space dimesions. On the other hand, can you disprove me by (by the way just theoretical) calculation?
Last edited by Relative; 2010-Dec-17 at 09:17 PM.

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Originally Posted by Garrison
And can you demonstrate any connection between the above and your theory? You see you not only lack supporting evidence for your theory but the available evidence actually contradicts it. And you have you bothered to go beyond Wikipedia and find out the degree of thermal contraction and what is meant by long timescales to see if it actually fits in with what your suggesting?
Okay. We know about the extension in the midatlantic ridge. Do we know this from GPS or do we see it in the position of the geolocical layres? If we make a GPS ditance determination between the tip of the Empire (I was abot to write "Entire") State Building and the Eiffel Tower, we find an increasement of 14 cm per year (according to our assumption that GPS works porperly). But has anybody measured the distance between Paris and New York in the opposite direction? We do not read anything about the loss of distance in the subductions zones, do we? And if so, what about the elevation of continental plates, has this been included?
Last edited by Relative; 2010-Dec-17 at 09:23 PM.

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At Hornblower: As I was saying. a millisecond, depending on what is your basis, is nothing. When we were determinating the speed of light, this would correspondend to an error of 3^-10. By the way, how did you get to L = 0.4MR2ω? I thought the moment of inertia was 2/5m r^2. So, where doese the 0.4 come from?

28. Originally Posted by Relative
Okay. We know about the extension in the midatlantic ridge. Do we know this from GPS or do we see it in the position of the geolocical layres? If we make a GPS ditance determination between the tip of the Empire (I was abot to write "Entire") State Building and the Eiffel Tower, we find an increasement of 14 cm per year (according to our assumption that GPS works porperly). But has anybody measured the distance between Paris and New York in the opposite direction? We do not read anything about the loss of distance in the subductions zones, do we? And if so, what about the elevation of continental plates, has this been included?
I'm afraid you're the one with the ATM theory, so you must provide the evidence to support your proposal, and if you can't answer the above why would you even put up your theory in the first place?

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The problem is, we do not have a system of satellites or whatsover, which quasi remains at an everlasting "stationary" place in the universe and provide unalterable information. It all depends on the point of view of the beholder. If you were living on the moon and were about to determine the distance from moon to earth (without knowing the bahaviour of water, as this is not existing in your home environment) you will fail. You will measure a distance at an always existing "high tide" on planet earth, as your home (the moon) influences this on the observed planet. The distance you measure, therefore, will always be too short...

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Originally Posted by Relative
So, you state that there might be a difference between stationary clocks and those orbiting. Otherwise you won`t blame me to lump them.
Yes, they are governed by different rules. In answering my and caveman's challenges you lumped them together incorrectly.

So, can we do reliable distance calculation then, if we have two different systems?
Yes, we can but it it not for me to answer your questions, it is for you to answer our challenges.

Another thougt experiment: If the distance between two GPS satellites in the orbit is measured, and the signal between the two of them is influenced by gravitaion, i.e. the two "ends" of the signal are influenced less then the curve (not a straight line) inbetween them, how do we know, how far they are away from each other exactly?

Ok, I assure, I`ve never heard from satellites falling to earth, because we weren`t able to make corrections in their orbit. I must admit, that GPS orbit corrections are not made by firing a jet but via rotating plates. Excuse me. But so, these satellites are NOT freely orbiting.
Again, you are making no sense, would you please answer the question I asked you. It does not involve any satellites.

In fact, we are still quite unsure. There have been test with pilots in a jet compared to ground, still quite inaccurate, but this is nothing in comparison to space dimesions. On the other hand, can you disprove me by (by the way just theoretical) calculation?