Cosmological Positioning - How does one determine?

  • #1
Gary0509
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TL;DR Summary
Wormhole opens and safely dumps you at a random point somewhere in our observable universe. How does one determine where they are in relation to their home origin?
Thought experiment I'm wondering if anyone has explored yet.

Imagine by whatever means you like, that your spaceship plucks you out of our solar system and drops you at another random point in the observable universe. Due to light speed limitation, where ever you end up will be looking at our home star (or galaxy) at a point in the past.

I guess there's two questions to this.
  1. If you know how far you went, how likely could an A.I. simulator run back our cosmological calendar to determine what our local neighbor would look like given no idea in what direction you went?
  2. If you had no idea how far you traveled, would it even be possible to determine where home is (or will be)?
 

Answers and Replies

  • #2
anuttarasammyak
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In case we can observe the stars, for both the questions, we would identify the stars seen in different relative positions from observation on the Earth. We would analyze the change of their maps and would know where we are and when it is in cosmological time.
 
  • #3
Gary0509
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In case we can observe the stars, for both the questions, we would identify the stars seen in different relative positions from observation on the Earth. We would analyze the change of their maps and would know where we are and when it is in cosmological time.
I understand (depending on the distance) we may have to shift to infrared frequencies to detect starlight. That's kinda besides the point. The response was a bit too simplified. Of course, what you would do is try to adjust your observations based on the new location. The question was could an A.I. run backward simulations to determine a stellar fingerprint?

It's more complicated than what's on the surface. Likely the A.I. could only run based upon current available star patterns. It would not take into account stars that no longer exist, or were gobbled up by black holes (as an example). The simulation would likely have a loss of accuracy based upon how far back in time it ran. And this would likely on be in relation to question #1.
 
  • #4
collinsmark
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Previous posts mention a lot about starlight and star patterns, but triangulating individual stars is almost certainly worthless unless you're really lucky and were teleported to somewhere within the Milky Way. And even then, starlight from individual stars might not help.

Sure, if you were lucky enough to be teleported to somewhere else in the Milky Way, you should be able to figure that out by noticing other galaxies in our local group. Then you could hopefully get an idea where in the Milky Way you are by observing Magellanic clouds and any globular clusters that are visible. And only then would you start looking for individual starlight and hope the cataloged stars are not clouded by dust.

But given the extreme vastness of the observable universe, the chances that you would end up still in the Milky Way is almost zero.

After the teleportation, you would be in your own, new observable universe, and you'd hope that there is enough overlap that you could find correlation with some part of the new sky and the old familiar observable universe from which you came.

So if and when you find yourself in that situation, you could start big. Look for large-scale structures such as galaxy super-clusters and cosmological filaments, and try to triangulate using them (again, individual star patterns would be pointless), doing your best to take speed of light considerations into account, as mentioned in a previous post.

Accuracy could take time. At first you'd want to do an "all sky survey" as a reference, and then start cataloguing Type 1A supernova to begin formulating new distance observations. Sooner or later, you'll hopefully start finding correlations.

I hope your ship has suitable telescopes.
 
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  • #5
anuttarasammyak
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Observing CMB we could know our proper speed wrt FLRW frame of reference by its anisotropy and cosmological time by its temperature or wave length. To go further I think we need some kind of light house or buoys instead of stars that were pointed out to be insufficient. Recent theorem predicts accelerating inflation of space and we, if taken to far future, might not be able to observe any neighboring bodies and thus positioning in observable space might become meaningless.
 
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  • #6
Ibix
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I agree with @collinsmark - I think you're basically sunk if you're outside this galaxy. A huge problem is that our maps of anything are out of date because of the light speed limit. What an area a million light years away (the next town over, in cosmological terms) looks to us is how it was like a million years ago and it could look quite different now. Stars will have changed on that timescale, and I suspect especially so the really big bright ones that would be easiest to map.

Inside, or near, the galaxy you could use clusters and galaxies for a decent fix and then look at standard objects like Cepheid variables to refine that.

Of course, even in our galaxy could be tens of thousands of light years away and you'd need magic propulsion tech to get home...
 
  • #7
Gary0509
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Okay! Got it, Collinsmark.

That is really helpful. Now I can wrap my noggin around it. Essentially, they'd need some uber telescopic technology to begin their mapping on the most distant regions first. Depending upon how sensitive their technology is (as well as filtering) may take a long time to even acquire that data. They'd then work backwards from those more distant regions (because the time variance would be minimal) and compare them with much larger structures, like Laniakea.

In that instance, given enough time to get the data, they'd honestly not even need to know how far they traveled as long as where they ended up was still relatively within the origin's observable universe.
 
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