Wednesday, October 24, 2007

Exhibit 2: Lunar Anomaly

China's Chang'e Moon probe finally launched Wednesday at 1000 GMT. Japan's Kaguya mission has already entered lunar orbit and released two smaller spacecraft. One of history's great achievements climaxed on July 20, 1969. Here it is recreated at the National Air and Space Museum in DC.

Apollo’s immense bounty of science returned the oldest rocks ever found and indicated that the Moon is a daughter of Earth torn free in a collision. The Lunar Laser Ranging Experiment (LLRE) told us that the Moon still has a liquid core, verified that Newton’s G is indeed constant, and provided one more test of General Relativity. LLRE has also found a huge but little-known anomaly in the Moon's drift from Earth.

Most of this apparent drift is due to tidal forces. As the Moon creates ocean tides, the tidal bulge outraces the Moon due to Earth’s 24-hour rotation. The bulge pulls the Moon along by a tiny amount, increasing the Moon’s orbital velocity. Through tides angular momentum is transferred from Earth to Moon across 384,402 kilometres of Space. This causes Earth’s rotation to slow, and the Moon to slowly drift away. LLRE has measured this drift at 3.82 ± .07 cm/yr, anomalously high.

Geology and paleontology can tell more precisely how the Moon’s orbit has changed. Coral gains layers on both daily and yearly cycles, dependent upon tides caused by the Moon. By studying fossilised coral we can tell the length of Earth’s day in the past, and therefore how much angular momentum Earth has lost. Growth rings in coral tell the height of lunar tides, indicating how close the Moon was in the past.

Starting with today’s LLRE measurement, Bills and Ray have compiled the most accurate estimates of lunar orbital distance. At an age of 310±5 million years, the Mansfield datum shows that the Moon's distance was 375.3±1.9 thousand km. These measurements show that the Moon has been receding at 2.9 ± 0.6 cm/yr. How can two precise experiments disagree on the same quantity? When the Moon appears to recede 1/3 faster than geology says, it is a serious anomaly.

If the speed of light slows, that would increase the time for light to return each year, making the Moon appear to recede faster as measured by LLRE.

From GM = tc^3, c(t) ~ t^{-1/3}

cdot/c = -1/3t

Where t is age of the Universe, on the order of 13.7 Gyr.

cdot/c = -1/(41.1 Gyr)

Factor cdot/c applies to any value measured in relation to c. Multiplied by the lunar distance of 384,402 km, that distance will appear to increase an additional 0.935 cm per year.

Today several nations are competing to reach the Moon. Already lunar exploration has led to some big surprises. Like Mercury's precession, the Moon has a big clue about cosmology. An anomaly in the Moon’s outward drift is precisely accounted for, indicating that c is slowing to this day.


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Anonymous Anonymous said...

You want a lunar anomaly? What's this?

Tell me why this isn't interesting.


1:27 PM  
Blogger Kea said...

I wish I knew more paleontology and geology! How do we know that the fossils are a scale replica of the original organism? Could the rock expand, or shrink? Soory to be so ignorant.

5:37 PM  
Blogger L. Riofrio said...

The monolith in 2001: A Space Odyssey started as an anomaly too. Anon's object is one more reason to revisit the Moon.

Judging from Kea's climbing experiences, you know many more useful things about rocks than most physicists.

Coral creates new layers on both a daily and yearly basis. By counting the number of layers per year, paleontologists can determine the nymber of days in a year and therefore how fast Earth was rotating. Determining whether fossils were underwater allows geologists to estimate tide level and therefore distance to the Moon millions of years ago. These markers are not dependent on size of the organism.

On the other hand, there are many things about Type Ia supernovae that may not be constant. Their redshifts are the ONLY evidence for "cosmic acceleration." Those scientists need to get a swimsuit and explore some coral reefs.

8:03 AM  
Blogger Kea said...

Those scientists need to get a swimsuit and explore some coral reefs.

Next time I'm on the Barrier Reef, I'll be looking more closely at the coral!

8:43 AM  
Blogger nige said...

Hi Louise,

Thank you for this post. It is impressive that the Moon was receding at the rate of 2.9 ± 0.6 cm/yr about 310 million years ago and it is now receding at 3.82 ± .07 cm/yr.

This is certainly very interesting. Over the last 310 million years the Moon has receded by at least 9000 km so the Earth-Moon distance has increased by at least 2.4%.

Regarding the mechanism for tidal action, this is too trivial to have much effect. In any case, you'd expect that when the Moon was very close to the Earth, the relative loss of energy to tidal action would be greater, and would decrease as the Moon receded, instead of speeding up. So there is no way that any changes in the energy loss rate due to tides, as the Moon recedes, could explain the observed increased rate of recession of the Moon.

Your accurate calculation here is very impressive. I'm interested that you write:

"The Lunar Laser Ranging Experiment (LLRE) told us that the Moon still has a liquid core, verified that Newton’s G is indeed constant, and provided one more test of General Relativity."

Exactly how did they verify that G is constant? It sounds like an arm-waving claim to me, like Teller's or Sean Carroll's claims that G isn't varying because (they claim) it would vary fusion rates in stars and the big bang (which isn't true because any variation in G would be accompanied by similar changes to other force coupling constants like electromagnetism, and the increased Coulomb repulsion between protons due to higher electromagnetic coupling would offset the increased gravitational compression due to higher G, so fusion rates aren't spectacularly affected). I'm very concerned about this because G variation is the only real alternative to c varying in your equation GM = tc^3, as I just wrote in a comment to your post on Exhibit 1.

Best wishes,

12:08 PM  
Blogger L. Riofrio said...

For Nige: Thanks, there is still possibility that G varies. Williams and Dickey, "Lunar Geophysics, Geodesy and Dynamics," from the 13th Int'l workshop on Laser Ranging, 2002, only set upper limits on G change. My post on Quantum Diaries would indicate that claiming a fundamental value constant is probably foolish.

2:22 PM  
Blogger CarlBrannen said...

Louise, I'm so glad to see you putting these posts together.

4:18 PM  
Blogger L. Riofrio said...

You are very welcome, Carl. I am glad you enjoy the posts. Some of this has been accepted for publication in a proper journal.

6:09 AM  
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