Earth’s Rotation cycles = Length of Day (LOD) cycles causing ΔT cycles which impacts our Climate
The Earth's rotation is gradually slowing down (opens in a new tab), a phenomenon that has been observed through the study of ancient eclipses and other astronomical events. Over centuries, this results in a slight increase in the length of a day (LOD) (opens in a new tab). For instance, it is estimated that the length of a day currently increases by about 1.8 milliseconds per century.
Earth’s rotation is not slowing down at a uniform rate, so it might differ per year. The value in 1902 was zero and as of 2020, TT was ahead of UT1 by ~69 SI seconds.
This slowing of Earth's rotation has implications for timekeeping systems, which rely on precise measurements of time intervals. There are 2 major definitions of time (there are lots (opens in a new tab) of (opens in a new tab) more (opens in a new tab)) but these are the two major ones (opens in a new tab)):
” Universal time (UT) represents the observed rotation angle of the Earth relative to an inertial reference frame.”
” Terrestrial Time (TT) is a theoretical uniform fixed time scale which aligned the mean Solar day in 1820 AD to be precisely 86,400 SI seconds. It is used as the time argument for the predictions of astronomical events. ”
So currently the length of day (LOD) - as measured on Earth (UT) - is increasing, compared to the length of day (LOD) fixed TT value of 86,400 SI seconds a day.
The TT value can be considered as the IFRS time. Independent on the LOD changes. That is why TT it is more suitable for the predictions of astronomical events.
The difference between TT and UT is known as Delta-T (opens in a new tab), which accounts for the discrepancies caused by Earth's irregular rotation. Delta-T has been increasing over time as the Earth's rotation slows, necessitating adjustments such as the addition of leap seconds to Coordinated Universal Time (UTC) to maintain synchronization with atomic time.
” ΔT is the time difference ΔT = TT − UT between Universal Time (UT, defined by Earth's rotation) and Terrestrial Time (TT, independent of Earth's rotation), which results in a drift in the length of a day as experienced on Earth”
The following graph can be found on the Wikipedia page about the historic values of Delta-T from 1650 AD.
NOTE: The little ice age ended around 1880, which is the same year as the trend of declining Delta-T, and since then we are living in a relatively warmer period. The Length of Day (LOD) cycles and climate cycles seems to be related to each other as also stated in several studies like this one from 2006 (opens in a new tab), this one in 1976 (opens in a new tab) and this one in 2010 (opens in a new tab). There are a lot more websites and studies that mention this same link. Go look for yourself on the internet.
So based upon the movements of the moon, the historic values prior 1955 are determined. After 1955 it is really measured.
The institution ”International Earth Rotation and Reference Systems Service” (IERS) (opens in a new tab) is the body responsible for maintaining global time. On their website (opens in a new tab) you can find more information as well.
Explanation Earth’s rotation slowing down in the dummy universe model
The reason for the current slowing down of Earth rotation because of an increase in the length of day (and therefore an increase of Delta-T), is NOT DIRECTLY linked to any Axial/ Inclination cycle in the dummy universe model.
There are however cycles in the dummy universe model that still have an impact in the bigger trend.
The 19,110 year cycle starts (and ends) when apsidal precession and axial precession are aligned with maximum eccentricity. The last time this alignment of perihelion with the December solstice happened was in the year 1,246 AD and in year 8,309 BC it was aligned with the June solstice (just like in year 10,801 AD). You can check it in the model: JD 2176324 the value of the Sun Orbit Center is 6:00:01 and the eccentricity reaches its value on this date at 06:00 of the Sun 0,01677891 AU.
Currently the eccentricity is decreasing to its minimum value of ~0.01132042 AU by the year 10,801 AD. So from max eccentricity in year 1246 AD we move to min eccentricity in 10,801 AD. That needs to have an impact on the length of day and therefore on Earth’s rotation as a big cycle.
But there are more forces at play that are causing cycles within cycles.
In the picture below, which you can find on several sites, the temperature cycles since 10,000 BC are presented.
You can clearly see (again) the cycles that are occurring. Based upon several studies, these cycles are directly related to Earth’s rotation and length of day values.
Why does the Delta-T graphs extrapolate exponentially into history?
I also found some graphs about the historic values of Delta-T from longer periods. This graph comes from this website (opens in a new tab)
On the IERS website (opens in a new tab) and in the same document mentioned above you can also find the Length of Day (LOD) historic values from 2000 BC to 2500 AD.
You can clearly see both graphs are inverse correlated. The longer the length of day, the smaller the value of Delta-T and vice versa.
NOTE: The length of day as shown in this graph is based upon theories (opens in a new tab) and formula’s (opens in a new tab) which makes sure the historic LOD values only will go further down and Delta-T up (opens in a new tab). In the excel sheet at chapter 6 I have added the formula’s so you can have a closer look.
As mentioned above, the length of day seems actually to be related to the climate changes (temperature movements) and therefore both these graphs with historic values of Delta-T and the length of day, can’t be right compared to the temperature graphs!
So the length of day, together with Earth’s rotation (and therefore Delta-T) is fluctuating and as a consequence the temperature changes. But according to above graphs the length of day comes from an absolute zero point and goes up indefinitely. That can’t be right. Does it really mean these graphs are wrong?
In my view what is shown in the longer term historical values of the length of day and Delta-T graphs, is because it is based upon Moon observations, either via eclipses or occultations (opens in a new tab), which can only be explained by Earth’s orbit around CENTER.
Earth is slightly turning on its orbital path around CENTER, causing the Moon to slightly turn as well, which had an impact on the observed point in time which shows as an increase in Delta-T.
The graph about the historic values of Delta-T from 2000 BC, seems to show a circle, which has most probably a ”furthest left point” in year 3992 BC and a most ”furthest right point” in year 6486 AD. Just like the apsidal cycle. But what this actually shows is the movement of Earth on its path around CENTER.
So to summaries as the length of day (LOD) currently increases, the rotation of the Earth is experienced to slow down. As a consequence we have a warmer period.
I have attached a picture of the figures coming out of the model:
In the dummy universe model there is a dance going on between UT and TT: Sometimes UT is ahead of TT and sometimes UT is behind on TT. In the long run however it is levelling out on the TT value of the length of day (LOD) of 86,400 SI seconds.
I created a graph with some more background on the dance between UT and TT. All data is in the Excel and directly coming from the 3D dummy universe model.
