Is the Moon moving away from Earth due to big bang inflation?

[spartan45]

I read on the BBC Sky At Night website that the Moon is moving away from the Earth (at about the rate fingernails grow according to google) because of the gravity pull caused by the tidal bulge being slightly ahead of the Moon. The effect is to accelerate the moon to a higher orbit and the energy used  results in slowing Earth's rotation.

Very plausable, but my instinct tells me this is not the reason. What do other members think of the theory that it is Big Bang inflation that is causing the distance between Earth and Moon to expand at the rate finger nails grow? 

[daiwelly]

Hi Spartan welcome to SGL,

The moon orbits the earth in  elliptical path at its closest  it slingshots around the earth so it speeds up and then travels out to its furthest point on the elliptical path. that what we was told on the OU the moons and planets course i did earlier this year. here is a transcript:

Synchronous rotation

Because most moons in the Solar System are in close orbit around much larger planetary bodies, over time the speed of a moon’s rotation is decreased as the tidal, or gravitational, pull between the two bodies drags on the moon’s spin. Eventually, this slows down a moon’s rotation so much that it completes only one rotation about its axis per orbit, resulting in the same side of the moon facing its planet at all times (known as captured rotation, or synchronous rotation). With the Earth and the Moon, these competing tidal forces have also exerted drag on the Earth’s rotation, slowing its rate of spin about its axis and thus lengthening a day by almost two milliseconds per century.

Tidal forces affect you too. While standing on the Earth’s surface, your head is nearly two metres further away from the centre of the Earth than your feet are. The Earth’s gravitational field can be treated as if all the mass were concentrated at the planet’s centre. Since the force of gravity decreases as the distance increases, your feet are pulled down slightly more strongly than your head. The anatomical consequences of this stretching are negligible for you, but for a much more extended body such as a moon, the physical consequences can be quite noticeable and in one case, as you will see later, very severe.  

[JamesF]

I think unless you can provide a plausible argument based on accepted physics that demonstrates why it should be the way you suggested then we should probably stick with the current accepted explanation as being the most reasonable.

"Instincts" are what told people the world was flat and that everything revolved around it.

Of course, if you are a heavy duty physicist specialising in orbital mechanics and cosmology, get a paper published; make your name.

James

[Stu]

I read on the BBC Sky At Night website that the Moon is moving away from the Earth (at about the rate fingernails grow according to google) because of the gravity pull caused by the tidal bulge being slightly ahead of the Moon. The effect is to accelerate the moon to a higher orbit and the energy used results in slowing Earth's rotation.

Very plausable, but my instinct tells me this is not the reason. What do other members think of the theory that it is Big Bang inflation that is causing the distance between Earth and Moon to expand at the rate finger nails grow?

As I understand it, inflation is effective over distances relative to the scale of the universe, but locally gravity has a more significant effect. The Andromeda Galaxy for instance is heading towards us, bound by gravity presumably as part of the local group, and that is around 2.5million light years away.

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[Knight of Clear Skies]

When I hear the phrase 'thinking with my gut' or some equivalent I remember that the human digestive system has a similar number of neurons* to a cat brain, so I like to mentally substitute the phrase 'my cat thinks...'.

Physics is strange, unintuitive and difficult I'm afraid, instincts often mislead us.

(* - That doesn't actually mean our guts are as smart as a cat, although the number of neurons is similar there are far more connections between them in a cat brain. So 'thinking with your gut' is reasoning on par with a very backward cat.)

[D4N]

Just be glad that it is going in the right direction!

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[Zakalwe]

I read on the BBC Sky At Night website that the Moon is moving away from the Earth (at about the rate fingernails grow according to google) because of the gravity pull caused by the tidal bulge being slightly ahead of the Moon. The effect is to accelerate the moon to a higher orbit and the energy used  results in slowing Earth's rotation.

Very plausable, but my instinct tells me this is not the reason. What do other members think of the theory that it is Big Bang inflation that is causing the distance between Earth and Moon to expand at the rate finger nails grow? 

"instincts" do not apply when discussing subjects like orbital mechanics. The field is non-intuitive.

For example: Two spacecraft are in orbit around the Earth. Craft "A" is slightly behind the other (Craft "B") and wishes to catch up. Does craft A:

A: Point at B and fire the engines (prograde) to catch up; or :

B: Spin 180 degrees so that A is pointing away from B and fire the engines to move away from B?

If you picked A (the instinctive answer) then you would be wrong. A has to slow down (with a retrograde burn) to drop into a lower orbit where it will move faster. It then overtakes B, rotates back and fires the engines prograde to lift back up into the other craft's orbital plane.

If A did a prograde burn first it would convert velocity into height and move into a higher orbit 180 degrees opposite the point where the burn ended (this is called a Hohmann transfer). Higher orbits have slower speeds so the gap would increase.

Of course, you might be correct, but this is highly unlikely as the maths behind orbital mechanics are pretty well understood.

Here's a good primer on the subject:

http://www.braeunig.us/space/orbmech.htm

[AstroJOE]

My instincts tell me the earth is just getting smaller which makes it seem like the moon is getting further away !! Lol

[oldnut]

I thought the moon had gotten further away then realised I had the binos round the wrong way! 

[Zakalwe]

Very plausable, but my instinct tells me this is not the reason. What do other members think of the theory that it is Big Bang inflation that is causing the distance between Earth and Moon to expand at the rate finger nails grow? 

Its worth also pointing out that what you have outlined is not a theory.  In science a theory is something that has been shown to be correct many, many times. There is usually no evidence to the contrary, otherwise the theory becomes invalid.  Theories are formed when a hypothesis gathers enough evidence (again by repeated observation and testing)

What you have outlined is a supposition, which is an uncertain belief. It's little more than a guess.

http://chemistry.about.com/od/chemistry101/a/lawtheory.htm

[Cath]

Instincts. gut feeling, common sense etc often have no place when it comes to how the 'real' world really works (on the small scale at least).

History tells us this time and time again. We really ort to accept it as being the way it is, unfortunately theirs nothing much we can do about it. It's not we who are making the rules, it's the universe itself that.

[hjw]

The inflation theory is a model to explain the inhomogenety of the universe. It lasted (if this theory is correct) from 10^-36 to about 10^-32 seconds after the big bang. One nanosecond after the big bang inflation was ancient history . I would stick with NASA on this one. They've been doing laser measurements since Apollo 11 put a mirror on the moon. The 3.8 cm/year is most likely explained by the tidal effects. However, since you like some gut feelings how about dark energy. DE is getting blamed for the fact that the expansion of the universe is accelerating rather than slowing down. There is some food for thought...

[Macavity]

As I understand it, inflation is effective over distances relative to the scale of the universe, but locally gravity has a more significant effect. The Andromeda Galaxy for instance is heading towards us, bound by gravity presumably as part of the local group, and that is around 2.5million light years away.

Quotably, no *expansion* occurs within (gravitationally) bound systems? Idem Atoms (e.m. bound systems) don't change size etc. Yet, there is something that slightly worries me... To my mind, the whole universe is "gravitationally bound" - So Gravity has infinite range, both large AND small! But then, quite a few concepts in Physics, seem to arbitrarily "switch on / off" at the behest of theory / theorist. [teasing] 

Clearly not everyone within Physics agrees about distance effects - Remember Brian Cox and the great "diamond rubbing controversy"? lol. Sometimes effects are small enough to neglect (measure). But that doesn't mean they aren't small and finite. Frankly, I have yet to see an entirely convincing explanation of the *region* of the universe within which expansion occurs (or not)... and the precise WHY of it? 

[Zakalwe]

Instincts. gut feeling, common sense etc often have no place when it comes to how the 'real' world really works (on the small scale at least).

History tells us this time and time again. We really ort to accept it as being the way it is, unfortunately theirs nothing much we can do about it. It's not we who are making the rules, it's the universe itself that.

Very much this. We are smart monkeys that through a series of extraordinarily lucky events, managed to make it this far. Our gut instincts have developed to help us spot predators that would have us for lunch and for judging how far we have to chuck a rock to turn something into dinner for us! Zero-gee environments, space, the infinities of the universe are totally alien concepts to us and our "common sense and instincts do not apply.

[spartan45]

I think unless you can provide a plausible argument based on accepted physics that demonstrates why it should be the way you suggested then we should probably stick with the current accepted explanation as being the most reasonable.

"Instincts" are what told people the world was flat and that everything revolved around it.

Of course, if you are a heavy duty physicist specialising in orbital mechanics and cosmology, get a paper published; make your name.

James

Oh boy, do I regret using that term "instinct" ! I don't think accepted physics should stop us questioning what we see. I'll give you an example or two - for many years text books "proved" using accepted physics that if you filled a rubber balloon with CO2 and another with hydrogen.then the balloon with the smaller hydrogen molecules would deflate first as they leaked through the rubber membrane. A school experiment showed this was not so. It turned out the larger CO2 molecules were shaped in such a way as to pass through the rubber in an unusual way. Text books all over the world had to be rewritten.  Just this year it was "proven" using accepted physics that fish cannot exist below 9,000m because of the effect on their molecules - yet in 1960 when the Trieste sphere dived the Challenger Deep to nearly 11,000m a sole type fish was seen moving through the murky waters only metres from the ocean floor. I am sure you know of many more examples so I won't go on. Mankind are ingenious - although perhaps cats can show us a thing or two.

[acey]

I read on the BBC Sky At Night website that the Moon is moving away from the Earth (at about the rate fingernails grow according to google) because of the gravity pull caused by the tidal bulge being slightly ahead of the Moon. The effect is to accelerate the moon to a higher orbit and the energy used  results in slowing Earth's rotation.

Very plausable, but my instinct tells me this is not the reason. What do other members think of the theory that it is Big Bang inflation that is causing the distance between Earth and Moon to expand at the rate finger nails grow? 

Your instinct is wrong.

The theory of tidal locking and the Moon's expanding orbit was worked out in the 19th century using Newtonian mechanics. A key figure was Charles Darwin's son G.H. Darwin.

Cosmological expansion arises from general relativity and is based on a simplifying assumption that the universe is a perfectly smooth fluid. This is good enough on the grandest scale (just as we can regard air and water as smooth even though they're made of molecules), but it doesn't work on small scales: our galaxy or solar system are not undergoing cosmological expansion.

So cosmological expansion (the Big Bang) has absolutely no relevance to systems such as the Earth and Moon. The 19th century Newtonian calculations can be made more accurate by using general relativity instead, but it makes no significant difference to the result.

What you state in your post is a very good summary of what is actually happening.

When it comes to science, you should perhaps trust the BBC a little more and your hunches a little less.

[JamesF]

Then "do your schoolboy experiment" as it were, and demonstrate that the currently-accepted physics is inconsistent with reality.  Without some sort of evidence you might as well propose that the Moon is moving away because of all the negative emotional energy it receives from astronomers who don't like it being around on clear nights.

James

[Paul M]

Hey up, what's all this?

'twas always my understanding that tidal interactionct between Eath and the Moon was imparting some of Earth's angular momentum into the Moon's orbital velocity.

So the Moon grows ever more distant.

The Moon gets smaller in our sky and Earth days grow longer.

One day there will be a last ever total solar eclipse.

Simples

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[JamesF]

One day there will be a last ever total solar eclipse.

Which makes me wonder... Is it amazing that homo sapiens happens to be around at a time when effects such as the "diamond ring" and the solar corona can be seen during a solar eclipse?  Or is it precisely because the Moon happens to be that distance away that led to the conditions for us to evolve at this time?

James

[symesie04]

Then "do your schoolboy experiment" as it were, and demonstrate that the currently-accepted physics is inconsistent with reality.  Without some sort of evidence you might as well propose that the Moon is moving away because of all the negative emotional energy it receives from astronomers who don't like it being around on clear nights.

James

Woo James man stop with the negative vibes!  

[JamesF]

Woo James man stop with the negative vibes!  

My apologies, Sergeant Oddball.  Now careful with that paint shell.  Wouldn't want it to go off in your hand...

James

[Knight of Clear Skies]

Oh boy, do I regret using that term "instinct" ! I don't think accepted physics should stop us questioning what we see.

Fair enough. I don't think anyone here would disagree with that statement. Doubt is an essential component of science, especially quantifying uncertainty, but in order to be useful it needs to be backed up by more than a case of the 'reckons'.

[symesie04]

woof

[Scott]

Don't ya just love it when the intellectual collective of SGL all get together to denigrate another member for daring to be free thinking. Just an observation is all 

[Scott]

Instincts. gut feeling, common sense etc often have no place when it comes to how the 'real' world really works (on the small scale at least).

History tells us this time and time again. We really ort to accept it as being the way it is, unfortunately theirs nothing much we can do about it. It's not we who are making the rules, it's the universe itself that.

Instinct tells me not to trust someone when they tell me their tiger is tame and I should take it for a ride. If it wasn't for instinct, the human race would not have survived day one. I think you greatly under estimate the importance of instinct