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The Earth's axis rotates (precesses) with a period of about ~26,000 yrs • Hence, while today Polaris is the North Star, this will change over time • This precession happens b.c the Sun & Moon induce a torque that pulls Earth's equatorial bulge toward the eclipticpic.twitter.com/wFxzwPTePl
The forces from the Sun & Moon on Earth's equatorial bulge induce a torque τ on the Earth • A body subject to external torque τ spinning with ang. momentum L is related to the precessional angular velocity Ω as: τ=Ω x L https://phys.libretexts.org/Bookshelves/Astronomy_and_Cosmology_TextMaps/Map%3A_Celestial_Mechanics_(Tatum)/6%3A_The_Celestial_Sphere/6.07%3A_Precession …pic.twitter.com/KS7Vn07oY4
Is the mentioned torque vector of Earth co linear with the axis of Earth's rotation?
The direction of the torque vector is perpendicular to the angular momentum vector and the applied torque .. the torque that induces the circular precession shown above therefore must be perpendicular to the spin axis
Does this mean that the seasons also drift with regards to the calendar year over a period of 26000 years?
Good question. I don't believe so, since precession affects the direction of Earth's axis, but not the angle of its tilt relative to the ecliptic. The 23.5º axis tilt is constant, so the seasons themselves continue on just the same
Just think about all the physics over billions of years in order to produce this masterpiecehttps://youtu.be/kjxSCAalsBE
Actually, this is quite interesting, because some 2000 years ago, we were entering the age of Pisces, the fish. This astrological event may have influenced some of the imagery of religions that popped up at the time (including Christianity and Mithraism).
1/2 Thus, when #Shakespeare has Caesar bragging about being being "constant as the northern star," it's somewhat of a flub, because in Caesar's time, the north celestial pole was sort of 2/3 of the way from Polaris to Kochab (and not even really on a line between the two). D'oh!
2/2 But it's still a great line and a great play, and we love WS regardless. :) (Perhaps the equivalent line in the equivalent play by the equivalent playwright on Kepler 22b says "constant as the speed of light" or "constant as pi" or some such. :-) )
Every time I see something about the precession, I think of this.https://grahamhancock.com/motlochw1/
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