Lunar recession

[no-one-particular]

There is geological and paleontological evidence that Earth rotated faster and that the Moon was closer to Earth in the remote past. Tidal rhythmites are alternating layers of sand and silt laid down offshore from estuaries having great tidal flows. Daily, monthly and seasonal cycles can be found in the deposits. This geological record indicates that 620 million years ago there were 400±7 solar days/year.

The current rate of lunar recession which has been measured very accurately by mirror's placed on the moon indicates that there should have been 426 days in a year 620 million years ago. The usual explanation is that the moon was receding more slowly in the past. This makes no sense. If anything the moon should have been receding faster in the past.

However, the current rate of lunar recession is consistant with the observation that there were 400 days in a year 620 million years ago if the Earth was closer to the Sun (because the year would be shorter). Its orbital radius would have to have been 0.9589 au at that time.

Recession rate = 6.85 * 10^-11 au/yr (10.25 m/yr)

Assuming that rate did not change, that puts it at 1-(1- 0.9589) *7.5 = 0.69 at 4.5 billion years ago

if the rate of recession is inversely proportional to the cube of the orbital radius then that puts the Earth just inside the sun 4.5 billion years ago

Year lengthens by 3.24 seconds per 1000 years

 

[NMN]

Based on the actual rate that the moon is receding from the earth, and not some theoretical rate the could only be proven with a time machine, the moon would have been scraping along the surface of the earth just about one million years ago. The fact is that easily observable evidence demonstrates the impossibility of an ancient earth.

 

[Keith&Co.]

Based on the actual rate that the moon is receding from the earth, and not some theoretical rate the could only be proven with a time machine,

Wouldn't we need a time machine to prove that the current rate is a constant?
I mean, if you measure the tide for a few minutes, extrapolation proves either the seas will be empty in a short time, or the entire Earth will be flooded, depending on when you take the measurements.

 

[repoman]

In the early time of the Solar System up until the Late Heavy Bombardment, I would not be surprised if the earth's distance from the sun changed quite a bit. After that I don't see what could do that.

This is an article that is strange, it seems to put the desired conclusion of a closer earth-sun sytem first in order to answer the Young Faint Sun Paradox.

https://arxiv.org/pdf/1306.3166.pdf

Maybe this is not such a reputable journal.

Compared to finding the earth moon distance, the earth sun distance can't be found using mirrors on the sun. There is also a lot of noise in the system with Jupiter, Venus and Mars tugging on us. I don't have a handle on what the relative numbers are of each.

Leaving aside Jupiter and Venus for the moment, if a decent physic calculation showed that from LHB (3.8 Billion years ago) to now the Earth's distance to the sun went from 0.9xx au to 1.00 au now I would give it consideration. It would be based on the same principles of earth moon recession.

To be unbiased, the calculation should only look at what is known about the physics and properties of the Earth and Sun. DON'T look for a target number of the earth sun distance in the past.


So the earth's sidereal year https://en.wikipedia.org/wiki/Sidereal_year is getting longer all the time as the orbit gets bigger. Going backward to Pre-Cambran or to the Archean, I have not found what much info about the sidereal year then.


------------------------------------------------

ok found another article, this looks well researched:

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&ved=0ahUKEwjN67fmk_DUAhVG12MKHZtjBWIQFghAMAQ&url=http%3A%2F%2Fonlinelibrary.wiley.com%2Fdoi%2F10.1029%2F1999RG900016%2Fpdf&usg=AFQjCNG3Q7-WDe6vGyn61V3MI7oHG6aYSA

This is a table from it


STILL, there is no mention of what the sidereal year was at that time compared to the current number time of 365.25636 SI days. An SI day is 24 hours*60 min/hr*60 sec/min.

A second is "At its 13th official meeting in 1967, the committee adopted the following definition: "The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom."

I am being pedantic on purpose so there is no possible confusion. The current sidereal year is 365.25636 days*86,400seconds*9,192,631,770 cesium-133 transitions. This is about 2.90102*10^17 cesium-133 transitions per sidereal year currently.

What was the sidereal year 620 Million years ago or 3.8 billion years ago?

That it is not mentioned makes it look like it must have been fairly close to what it is now.

 

[repoman]

What about doing a big picture energy balance for the entire Earth Moon system? Of course dissipative friction has to be added in somehow.

Compare the rotational energy of the earth-moon now to the data from 620 million years ago.

The earth has a moment of inertia: I = 8.04×1037 kg*m2 which can't have changed much.

Might do this later...

 

[bilby]

The Gross Lunar Product has basically been zero since their last export of rocks to Earth in December 1972, an astonishing 180 consecutive quarters without any economic growth (or, indeed, activity) at all. However as the Lunar economy hasn't shrunk during that time, it's not technically a Lunar recession.

 

[fromderinside]

If the lunar landscape is any indication meteor impacts are the measure of activity on the moon.

Fortunately someone is observing . About Lunar Impact Monitoring https://www.nasa.gov/centers/marshall/news/lunar/overview.html

Finally.

Maybe in a thousand years or so we'll be able to determine whether moon meteor activity is in recession. Until then I urge keeping Lunar your money on the sideline.

 

[Jimmy Higgins]

Based on the actual rate that the moon is receding from the earth, and not some theoretical rate the could only be proven with a time machine, the moon would have been scraping along the surface of the earth just about one million years ago. The fact is that easily observable evidence demonstrates the impossibility of an ancient earth.

Odd how my calculations of the sea flooding the planet when the tide came in seemed to be based on a faulty premise when the tide didn't flood the planet. If I could only figure out what it was.

 

[Loren Pechtel]

The Gross Lunar Product has basically been zero since their last export of rocks to Earth in December 1972, an astonishing 180 consecutive quarters without any economic growth (or, indeed, activity) at all. However as the Lunar economy hasn't shrunk during that time, it's not technically a Lunar recession.

I must disagree. There have been exports of information since then. There appear to be three active scientific satellites (two missions, one of which has a pair of birds) now, thus there still is an economy.

 

[Jokodo]

Based on the actual rate that the moon is receding from the earth, and not some theoretical rate the could only be proven with a time machine,

Wouldn't we need a time machine to prove that the current rate is a constant?
I mean, if you measure the tide for a few minutes, extrapolation proves either the seas will be empty in a short time, or the entire Earth will be flooded, depending on when you take the measurements.

We don't need a time machine to deduce that the rate is *not* a constant. Just plate tectonics + common sense. With a bit of fluid dynamics on top, we can even estimate past rates.

The rate of recession is not a primitive but causally linked to tidal breaking on Earth (tidal distortion of the rockbed itself is a very minor contributor in comparison). That is, it depends on how much force the oceanic tides wash up against the continents with. If the Earth were a cueball, there'd be essentially no tidal breaking. If the Earth were entirely covered in ocean, there'd be very little due to friction. If the continents were all in one place, there'd be only one long shoreline against which the tide washes. If the continents were concentrated near the poles, also little tidal breaking.

The maximum tidal breaking is what you get when you have several separate large landmasses evenly spaced perpendicular to the equator. That's pretty much what we have today!

(There's some added stuff about the ocean body's harmonic frequencies and stuff which involves math I'm too dumb to grasp. The calculations have been made in the 70s and 80s -- pretty much as soon as plate tectonics was universally accepted -- and they fit paleontological observations such as day and year growth rings in corals etc. I can probably dig up those papers again if google fails.)

 

[Jokodo]

Based on the actual rate that the moon is receding from the earth, and not some theoretical rate the could only be proven with a time machine, the moon would have been scraping along the surface of the earth just about one million years ago. The fact is that easily observable evidence demonstrates the impossibility of an ancient earth.

An actual rate we *know* not to be constant. See my previous post.

 

[Jokodo]

The current rate of lunar recession which has been measured very accurately by mirror's placed on the moon indicates that there should have been 426 days in a year 620 million years ago. The usual explanation is that the moon was receding more slowly in the past. This makes no sense. If anything the moon should have been receding faster in the past.

If distance is the only thing you account for, yes. But distance isn't the only thing that effects the amount of tidal breaking and thus the rate of exchange of momentum - plate tectonics is a biggie here.