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RAZD
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Message 12 of 12 (821508)
10-08-2017 5:11 PM
Reply to: Message 8 by dwise1
09-20-2017 3:40 PM


Re: Converting Units - check against evidence
I will also plan on a better set of "years ago" to include ones for which we have geological evidence of the length of the day; eg, 400 days in the year in the Devonian, about 400 million years ago.

Curiously I have an entry on just this in Message 7 of my The Age of the Earth (version 3 no 1 part 3) thread:

quote:
Coral Growth and Geochronometry(3)

quote:
The two chief approaches to geochronometry are based on radioactive isotopes and on astronomical data. The most recent estimates 2 of geological time based on the rates of radioactive decay give the Cenozoic a length of 65 million years, the Mesozoic 165 million years, and Palaeozoic 370 million years, and so on. The beginning of the Cambrian is placed about 600 million years ago. To accept these figures is an act of faith that few would have the temerity to refuse to make. The other approach, radically different, involves the astronomical record. Astronomers seem to be generally agreed that while the period of the Earth's revolution around the Sun has been constant, its period of rotation on its polar axis, at present 24 h, has not been constant throughout Earth's history, and that there has been a deceleration attributable to the dissipation of rotational energy by tidal forces on the surface and in the interior, a slow-down of about 2 sec per 100,000 years according to the most recent estimates. It thus appears that the length of the day has been increasing throughout geological time and that the number of days in the year has been decreasing. At, the beginning of the Cambrian the length of the day would have been 21 h (ref. 1). After the first, a second act of faith is easy, and we can develop a simple relation between the geological time-scale and the number of days per year (Fig. 1)

Accepting this relation, in the absence of evidence to the contrary, it now follows that if we can find some means of determining the number of days per year for the different geological periods, we have a ligation between the results of geophysical and astronomical deductions. If we could determine, for example, that the number of days in the Cambrian year was of the order of 420, it would seem to confirm an indicated age of 600 million years based on tidal friction and in turn that since isotopic methods give the same result they too are in harmony. Is it possible to obtain estimates of the number of days per year from data preserved in recent and fossil organisms ? I would like to think so.

... Physiological studies on calcium carbonate secretion in recent corals, first made some years ago by Kawaguti and Sakumotos 6, and recently and more elegantly by Goreau 7, who used the isotope calcium 45, show that in reef corals the rate of calcium carbonate uptake in coral tissues falls at night or in darkness and rises during the day, but the reflexion of this in the skeleton ton has not yet been investigated. A much less-sophisticated approach would be to compare the number of ridges with the annual growth-rate; but this has not been directly tried on living corals in the field. I have tested it indirectly on one or two recent corals the annual linear growth-rate of which is fairly well known, and to my gratification found that the number of ridges on the epitheca, of the living West Indian scleractinian Manicina areolata (Fig. 5) hovers around 360 in the space of a year's growth. This strongly suggests, subject to experimental confirmation, that the growth-lines are diurnal or circadian in nature. It may be noted in passing that they may provide a much more sensitive caliper for measurement of annual growth-rates than the larger yearly simulations.

The next step, of course, is an attempt to determine, the number of growth-lines per annum in fossil corals. Here, as is usually the case, hypothesis is easier than practice. Few fossil corals are sufficiently well preserved to show clearly the supposed diurnal growth-lines, and it is not easy to determine the annual rate. In epithecate recent corals the growth-lines are commonly abraded or corroded even before death of the polyp. The best of the limited fossil material I have examined so far is from the Middle Devonian. of New York and Ontario, especially specimens of Heliophyllum, Eridophllum .(Fig. 6) and Favosites. Diurnal and annual growth-rates vary in the same individual, adding to the complexity, but in every instance there are more than 365 growth -lines per annum. usually about 400, ranging between extremes of 385 and 410. It is probably too much, considering the crudity of these data, to expect a narrower range of values for the number of days in a year in the Middle Devonian; many more measurements will be necessary to refine them.

A few more data may be mentioned: Lophophllidium from the Pennsylvanian (Conemaugh) of western Pennsylvania gave 390 lines per annum, and Caninia from the Pennsylvanian of Texas, 385. These results imply that the number of days a year has decreased with the passage of time since the Devonian, as postulated by astronomers. and hence that values of the isotopic dates of the geophysicists agree well with the astronomical estimates of the age of the Earth. ...


So these samples with diurnal growth rings showing faster spin and more shorter days per year, right in line with astronomical predictions.

Coral-algae metabolism and diurnal changes in the CO2-carbonate system of bulk sea water(4)

quote:
Abstract

Precise measurements were conducted in continuous flow seawater mesocosms located in full sunlight that compared metabolic response of coral, coral-macroalgae and macroalgae systems over a diurnal cycle. Irradiance controlled net photosynthesis (Pnet), which in turn drove net calcification (Gnet), and altered pH. Pnet exerted the dominant control on [CO32−] and aragonite saturation state (Ωarag) over the diel cycle. Dark calcification rate decreased after sunset, reaching zero near midnight followed by an increasing rate that peaked at 03:00 h. Changes in Ωarag and pH lagged behind Gnet throughout the daily cycle by two or more hours. The flux rate Pnet was the primary driver of calcification. Daytime coral metabolism rapidly removes dissolved inorganic carbon (DIC) from the bulk seawater and photosynthesis provides the energy that drives Gnet while increasing the bulk water pH. These relationships result in a correlation between Gnet and Ωarag, with Ωarag as the dependent variable. ...


This confirms how and why there are diurnal growth rings in corals.

Earth's rotation: Change in rotational velocity(5)

quote:
Over millions of years, the Earth's rotation slowed significantly by tidal acceleration through gravitational interactions with the Moon. In this process, angular momentum is slowly transferred to the Moon at a rate proportional to r-6 , where r is the orbital radius of the Moon. This process gradually increased the length of day to its current value and resulted in the moon's being tidally locked with the Earth.

This gradual rotational deceleration is empirically documented with estimates of day lengths obtained from observations of tidal rhythmites and stromatolites; a compilation of these measurements[41] found the length of day to increase steadily from about 21 hours at 600Myr ago[42] to the current 24 hour value. By counting the microscopic lamina that form at higher tides, tidal frequencies (and thus day lengths) can be estimated, much like counting tree rings, though these estimates can be increasingly unreliable at older ages.[43]


And 21 hour days would mean 24x365.24/21 = 417 days per year.


So it looks like your calcs are in the right ballpark.

Enjoy


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This message is a reply to:
 Message 8 by dwise1, posted 09-20-2017 3:40 PM dwise1 has taken no action

  
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