# Astronomy question - do stars retain relative position each year viewed from earth?

Say I were to look due north at midnight on 1 Jan 2008 from a given location, are the stars I would see in the same place as they were on 1 Jan 1998, or 1 Jan 1808?

The reason I ask comes from this site:

http://www.grahamphillips.net/Ark/Ark_10.htm

and specifically this picture.

The author claims that by viewing night sky at midnight on 6 Jan from a particular hill in South Warwickshire, you can deduce the resting place of the Ark of the Covenant.

Now this is only 20 mins from my house, so it’s all quite exciting.

BUT… the whole premis seems to rely on the fact that the stars would be in the same position at that specific time as they were 100 yrs ago (or whenever the window was created).

By drawing a line through two stars in The Plough (which are linked to the Ark legend) it hits a point on the horizon - like this - and there lies the Ark (or so it goes).

If the stars don’t stay constant, that line could be anywhere though, hence my question.

The stars stay in roughly the same configuration from one year to the next, but over a period of centuries they do not. Precession causes the direction of the Earth’s axis to change over a long period which means that the stars do not appear in the same position on 1 Jan 2008 as they did on 1 Jan, say 1608.

Strictly speaking, no, it’s not exactly the same. The stars have what’s called proper motion, and their absolute position on the sky does change with time. However, this change is very, very slow; the star with the highest proper motion, Barnard’s Star, would take about 360 years to move one degree on the sky. (And Barnard’s Star isn’t even visible to the naked eye.)

I also managed to find a movie of proper motions in the Big Dipper (what we call that collection of stars on this side of the pond.) Notice that every frame in this movie is a thousand years, and that the shape of the Big Dipper hasn’t changed significantly over human history. However, if you’re talking about extrapolating lines down to the horizon, then these small changes might indeed be enough to throw you off.

Here’s a nice academic page explaining the motion of the stars.

Precession doesn’t change the relative position of the stars though, just the position of the “celestial sphere” relative to the Earth.

Good luck on your Ark hunt, watch out for Nazis

Cool! Now I know why people from 98,000 years in the future call it the ‘Meat Cleaver’.

I know that, but that still means that those two stars in the Plough won’t point to the same point on the horizon over time.

But they would change what the OP is asking about though—the alignment of the stars with ground features. Right?

Quite right, I just glanced at the OP’s links and so misunderstood.

Wouldn’t our orbit around galactic center also have an effect? Also slow (a bit over 100 million years to go half way around) so even on an all of human history timescale we have not moved all that much (relatively speaking) but still…

That’s part of “proper motion”, and on the time scales that we’re talking about here, not a terribly important part. All stars are in orbit around the galactic center, but with irregular movement superimposed upon those orbits, and that irregular movement makes up most of what we see as proper motion. (If all the stars were in perfectly regular orbits, then we’d see very slow and very regular movement more like what we see on a smaller and faster scale with the planets.)

Thanks all - apparently they found one of the tablets containing the Ten Commandments in a ditch, but I’m hoping there’s some more left to find.

Useful links - sounds like a 19th century star code will still be more-or-less valid today, so the map inference remain valid (although still waaaay over the kook-horizon).

well, I have to say, that’s a lot more convienient that carrying that pesky Staff of Ra headpiece around.

On a related subject, the U.S. Department of Defense spends millions of dollars every year tracking the precise position of the North Star relative to earth. The measurement is performed each night (assuming there’s no cloud cover). I’ve been to the facility. Quite fascinating.

Good old DoD … Gotta keep a close & wary eye on that Polaris; it might shift into attack formation at any moment.

And there is Barnard’s Star. Sometime faceciously called Barnard’s Comet.