Ladies & gents,
Allow me to start off the present exposé with this rather ‘bombasticsounding’ statement  were it only to wet your reading appetite: if what follows won’t make your jaw drop – or totally blow your mind – probably nothing ever will!
I will assume that this forum’s readers will have at least heard of the famed “Milankovitch cycles”; if not, you may peruse this Wikipedia page dedicated to the same  to get a general idea of what those longterm cycles are all about.
Well, in later years, a peculiar / longterm Milankovitch cycle of 405000(±500) years has become a hot topic among a wide range of diverse, wholly unrelated scientists. In fact, it would appear that the existence of this “405kyr cycle” (kyr = kiloyear) is largely agreed upon by geologists, climatologists, dendochronologists and astronomers alike! To be sure, this is a most unique and remarkable instance of multidisciplinary consensus between such different fields of research.
Below are a series of links to articles concerned with this ‘curious’ 405kyr cycle

“Geologic evidence confirms existence of 405,000year Milankovitch cycle”

“Jupiter and Venus Change Earth’s Orbit Every 405,000 Years”
Note that the last article mentions a period of “202500 Years” which is, of course, 405000 / 2.
Now, those who have read my Tychos book will know about the 25344year period (i.e. the “Great Year”) which is the time stipulated by the TYCHOS model for the Earth to revolve once around its PVP orbit (as illustrated in Chapter 20). Also, in Chapter 16 of my book, I expound how our Solar System seems to be pervaded by the number “16” (or round multiples / fractions thereof). I thus decided to put this “16 factor” to the test (in relation to the 405kyr cycle) – and promptly found that:
25344 X 16 ≈ 405500 (i.e. the higher boundary of the 405000±500year estimate of the long interval known as the “405kyr Milankovitch cycle”).
So, having spent several years finetuning the accuracy of the Tychosium 3D simulator (and being quite pleased with its performance so far), I was curious to see what would happen if I added 405500 years to a given date in the Tychosium. Well, that’s when my jaw dropped…The Sun, Mercury, Venus and Mars returned to the almost exact same celestial positions (ephemerides)!
You can verify this for yourselves: open the Tychosium on your laptop. Set the date at 20010621 (a day that, incidentally, featured a solar eclipse). Take note of the positions of the Sun, the Moon, Mercury, Venus and Mars. Then, jump forward by 405500 years to the date 4075010621.
I was then curious to see what would happen if I halved that 405500 value to 202750 (keeping in mind the “202500year” period mentioned in that last article linked above). Lo and behold – the Sun, Mercury, Venus and Mars returned again to the nearexact same positions!
You may now rightly ask: “so what about the Moon? Wasn’t there a solar eclipse on 20010621?”
Yes indeed. So I then tried adding 811000 years (i.e. 2 X 405500) to the date 20010621, which gets us to the date 8130010621. And that’s when my mind well & truly blew up… Lo and behold, – the Sun, Mercury, Venus and Mars returned AGAIN to the same positions, while the Moon returned facing the Sun (in a solar eclipse)!
As it is, the Tychosium simulator shows that – with each 202750year interval  the Moon “ticks” by 90° around its own orbit (as illustrated in my below, ‘megagraphic’  which should clarify all of this). Hence, in 811000 years  i.e. 202750 X 4  the Moon (which in my book I call the “central driveshaft of our system”) completes what I will henceforth be calling “our System’s 811000year MEGA CYCLE”:
(Please click on the image  twice  to view it at full size on your screen)
But there’s more, folks: What one may call the “cherry on the cake” of all these astonishing synchronicities, is the fact that EROS (our most famous nearearth asteroid) also returns to the nearexact same position in our skies over one 811000year MEGA CYCLE! Mind you, perhaps this shouldn’t come as too much of a surprise, since we know that EROS has a distinct 81.1year period in which it returns CLOSEST to the Earth. Hence, in 811000 years, EROS will complete exactly 10000 such 81.1year periods! (81.1 X 10000 = 811000).
Lastly – but not leastly  it is known that the two components of the Sirius binary system (Sirius A and Sirius B) revolve around each other in 50 years. This means that, in 405500 years, they will revolve around each other for a total of 8110 times (or 811000 / 100). Well, at the end of Chapter 6 of my book, I speculate that the Sirius binary system may be the “doubledouble” companion of our SunMars binary system. Logically then, one might reasonably surmise that HALF of our revolution around Sirius is completed in 405500 years – and that a FULL such revolution is completed in 811000 years.
In any event, dear ladies and gentlemen, it is looking more and more as if we live in a formidably stable (and nonchaotic) “clockwork universe”! We may thus live our lives in the blissful assurance that no cataclysmic cosmic event will wipe out humanity anytime soon.