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Motivated by this question about a stranded submarine in the Jurassic I would like to know:

Is there anything remotely left of our current skyline if we go back or forward millions of years so that the stars rotating around the milky way covered a measurable distance ? I would expect that the proper motion of a star causes an irreversible drift out of the original position. Are there any stabilizing factors which may allow that some star configurations are still discernible ?

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  • $\begingroup$ If you go forward by more than a few hundreds of millions of years you will find that the Andromeda galaxy is either noticeably closer or already colliding with the Milky Way. As this will happen about 4.5 billion years from now, however, it's rather unlikely that there's still an Earth where you could be observing the skyline from. In time the very shape of both galaxies will be distorted beyond recognition. $\endgroup$
    – pablodf76
    Jan 5 '17 at 13:30
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The sun still rises in the East and sets in the West. So you quickly identify the cardinal directions.

By observing the point around which the stars rotate each night you can find the altitude of the pole, which gives you your latitude. You can't find your absolute longitude, but with good time keeping you can find your longitude relative to your starting point. The planets are still in the same orbits. You might find that Saturn doesn't have rings (it's not certain how old the rings are)

The Galaxies would still be in the same positions, The Milkyway, Andromeda and the Magellanic clouds are all visible. Many more with a moderate telescope, The Milkyway would look different, in detail, the LMC and SMC would be in different positions.

However, the stars in the background have all changed. There are no constellations that have not undergone radical changes. There would be no stars that you recognise: Stars are visible either because they are close (and so have a large proper motion) or powerful and short-lived. All the stars you know would either have moved, or not be born yet.

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  • $\begingroup$ As the sun roughly orbits the center of the milky way every 220-240 million years or so, that should move the Milky way from a Southern Hemisphere to a Northern Hemisphere object every 110 million years or so I would think, unless the motion of the sun would dominate that apparent movement. (or am I overthinking this). $\endgroup$
    – userLTK
    Jan 2 '17 at 23:06

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