![Wink ;)](./images/smilies/icon_wink.gif)
I can see how this composite can be misleading, but I still think it was cleaver of the photographer to make the spiral around a different star from Polaris.
Of course it's continental drift! The image is exactly correct; in 14,000 years, the building's location will have shifted in latitude to produce that exact image.PTW wrote:starsurfer wrote:[...] The only things that will affect where the rotation point is in the picture are polar motion and continental drift.
Polaris will be back around in 27800 CE. Of course, it exhibits a degree of proper motion, so over time it will drift away from the pole even without considering precession.Boomer12k wrote:What was the prvious North Star... And when, if ever, will Polaris be the North Star again?
For the moment, yes. At least, one bright enough to be useful.ta152h0 wrote:and the South pole is void of a star ?
The variation wrt the ecliptic is about as you say. Over a longer time scale (1 million years) the ecliptic pole declination (J2000) is predicted to vary from 64° to ~69.5°. The combined wobbles of the ecliptic and the Earth's obliquity complicates how our NCP position evolves, even over a couple precession periods. (Plots below are from a previous post: http://asterisk.apod.com/viewtopic.php?f=30&t=34333)Chris Peterson wrote:Our axial tilt varies only a little, from about 22° to 24°. That does have an impact on long term climate, which shows up cyclically since the variation in tilt is partly related to our precession (modified by motion of the ecliptic itself due to planetary perturbations). The Moon also causes a bit of variation in tilt, although it actually is responsible for stabilizing it (Mars, which has no moon, experiences very wide variations in axial tilt).revloren wrote:What this displays is axial precession, which on Earth occurs on a 26,000 year cycle. Does this mean that the 23.4 degree tilt of earth axis changes as the planet wobbles? I believe this is in relation to the ecliptic, but the wobble would apply in relation to any fixed point. Would this also not have a dramatic effect on the Earth's seasons?
As people have commented, I think the composite can be misleading, too. And I commented on SpaceWeather.com site (posted before APOD) and discussed on that point with the contributor by private e-mail.Jarod997 wrote:Thank you Chris - that's what I thought. The earth still spins on it's axis, is just where that axis is pointing in space that changes over time. It's like taking a photo of a speeding car with 1/4 second exposure time and being asked to identify the make and model - sort of. (The car is... yellow.)
I can see how this composite can be misleading, but I still think it was cleaver of the photographer to make the spiral around a different star from Polaris.
paragkulkarni wrote:
And what happens to URSA MAJOR at that time.
It loses its great bear shape.
http://earthsky.org/favorite-star-patterns/big-and-little-dippers-highlight-northern-sky wrote:
<<Even 25,000 years from now, the Big Dipper pattern will look nearly the same as its does today. Astronomers have found that the stars of the Big Dipper (excepting the pointer star, Dubhe, and the handle star, Alkaid) belong to an association of stars known as the Ursa Major Moving Cluster. These stars, loosely bound by gravity, drift in the same direction in space. In 100,000 years, this pattern of Big Dipper stars (minus Dubhe and Alkaid) will appear much as it does today!>>
Yeah, right. Assuming it ever did look like a bear.paragkulkarni wrote:And what happens to URSA MAJOR at that time.
It loses its great bear shape.
The year 14000 is in the past... just not yet...Steven Morris wrote:"... star trails reminiscent of the year 14000 CE" is incorrect. You can only reminisce about past events. These star trail are reminiscent of the year 12000 BCE.
I can see the bear!Chris Peterson wrote:Yeah, right. Assuming it ever did look like a bear.paragkulkarni wrote:And what happens to URSA MAJOR at that time.
It loses its great bear shape.
Steven Morris wrote:
"... star trails reminiscent of the year 14000 CE" is incorrect.
You can only reminisce about past events. These star trail are reminiscent of the year 12000 BCE.
Chris Peterson wrote:For the moment, yes. At least, one bright enough to be useful.ta152h0 wrote:
and the South pole is void of a star ?
http://myweb.tiscali.co.uk/moonkmft/Articles/Precession.html wrote:
Sheffield Astronomical Society Newsletter (1994)
by Kieron Taylor.
<<At present, the neighbourhood of the South celestial pole is rather devoid of bright stars. The South pole is marked by the 5.5 magnitude star Sigma Octans, barely visible to the naked eye. In the year 4200 AD, the 4.1 magnitude star Gamma of the constelation Chameleon will be less than 2° from the pole. In the year 5800 the 3.6 magnitude star Omega Carinae will be less than a degree from the South celestial pole. There are a number of second or third magnitude stars in this region of the sky, many of which will pass close to the pole. In the year 8100 the 2.3 magnitude star Aspidiske, again in the constelation Carina, will be the pole star, followed in 9200 by the magnitude 2.0 star Delta Velae. (By now the Milky Way is crossing the South pole, so the neighbourhood is studded with a number of moderately-bright stars, many of which take their turn at holding the honour of being Pole Star.) Around the year 14,000 AD, while Vega is marking the North Celestial Pole, Canopus, the second brightest star in the sky, will be within 10° of the South Pole ; and around the year 22,000 AD the 0.5 magnitude star Achernar, in the constelation Eridanus, will have a South declination of about 82½°.>>