The future visibility limit
March 10, 2019 10:10 PM   Subscribe

How Much Of The Unobservable Universe Will We Someday Be Able To See? - "Light that was once too far away from us to be seen can now catch up to us. This fact carries with it a huge implication for the Universe: over time, galaxies that were once too distant to be revealed to us will spontaneously come into view."
As the Universe ages, the expansion rate doesn't drop to lower and lower values, approaching zero. Instead, there remains a finite and important amount of energy intrinsic to the fabric of space itself. As time goes on in a Universe with dark energy, the more distant objects will appear to recede from our perspective faster and faster. Although there's still more Universe out there to discover, there's a limit to how much of it will ever become observable to us.

Based on the expansion rate, the amount of dark energy we have, and the present cosmological parameters of the Universe, we can calculate what we call the future visibility limit: the maximum distance we'll ever be able to observe. Right now, in a 13.8 billion year old Universe, our current visibility limit is 46 billion light-years. Our future visibility limit is approximately 33% greater: 61 billion light-years. There are galaxies out there, right now, whose light is on the way to our eyes, but has not had the opportunity to reach us yet.

If we were to add up all the galaxies in the parts of the Universe that we'll someday see but cannot yet access today, we might be shocked to learn that there are more yet-to-be-revealed galaxies than there are galaxies in the visible Universe. There are an additional 2.7 trillion galaxies waiting to show us their light, on top of the 2 trillion we can already access...

Although there are a total of 4.7 trillion galaxies that we will someday be able to observe out to a distance of 61 billion light-years, the limit of what we can reach today is much more modest. Only those galaxies within approximately 15 billion light-years, or a quarter of the radius at the future visibility limit, can be reached today, which equates to about 66 billion galaxies only. This is only 1.4% of the total number of galaxies that will ever become visible to us. In other words, in the future, we will have a total of 4.7 trillion galaxies to view. Most of them will only ever appear to us as they were in the very distant past, and most of them will never get to see us as we are today. Of all those galaxies we'll someday see, 4.634 trillion of them are already forever unreachable, even at the speed of light.
also btw...
posted by kliuless (25 comments total) 43 users marked this as a favorite
 
This post just placed me in the Total Perspective Vortex.

Thank you?
posted by m@f at 10:24 PM on March 10, 2019 [8 favorites]


In a brief transcendent moment last night I looked aloft and wondered how much of what we see is still there? How can we know?
posted by unearthed at 11:29 PM on March 10, 2019 [1 favorite]


"Of all those galaxies we'll someday see, 4.634 trillion of them are already forever unreachable, even at the speed of light."

That's where the other civilisations are. We will never be able to reach them.
posted by Termite at 11:49 PM on March 10, 2019 [1 favorite]


We need to shout really loud.
posted by popcassady at 1:24 AM on March 11, 2019 [1 favorite]


The sad part is that as new things come into view, more and more of the presently observable universe is becoming redshifted to the point of invisibility, so immediately after we reach "peak star," we will inevitably more and more isolated into a smaller and smaller patch of space.

Assuming we don't roast ourselves or get roasted before then, of course..

It's sad to think that a civilization arising a billion or so years in the future would lack the clues in the form of the cosmic microwave background that have allowed us to understand so much about how our universe has evolved since its birth. The CMB, the ancient quasars, early galaxies, all rendered invisible by the inexorable march of time. Even in principle, the information we can glean from our surroundings today will be unknowable to future civilizations absent records from those that came before.

We really are quite lucky to have evolved at a time when it is still possible to "see" all the way back to the era of recombination.
posted by wierdo at 2:14 AM on March 11, 2019 [10 favorites]


If a galaxy exists in a universe and no one is around to hear it, does it make a sound?
posted by fairmettle at 2:42 AM on March 11, 2019


I am reminded of Stephen Baxter's short story Last Contact.
posted by edd at 3:31 AM on March 11, 2019 [13 favorites]


Hug yer loved ones.
posted by nikaspark at 5:26 AM on March 11, 2019 [2 favorites]


This is an argument for unrestrained hedonism.
posted by grumpybear69 at 6:29 AM on March 11, 2019 [4 favorites]


I was listening to this interview with Harvard Astronomy dept. chair Avi Loeb this morning - while it's largely focused on the ʻOumuamua object, one of the sidebars I found fascinating was the discussion of Pan-STARRS and the soon-to-be-online Large Synoptic Survey Telescope.

Loeb notes how little of the 'visible' universe we can currently see with precision, and that the LSST will shortly be collecting vast amounts of previously unobtainable, and possibly revolutionary, fine-grained data about the objects in our galaxy. There is still, apparently, a lot that can be learned by carefully observing what is available to us.
posted by ryanshepard at 6:41 AM on March 11, 2019


This is an argument for unrestrained hedonism.

Anything's an argument for unrestrained hedonism if you're brave enough.
posted by solotoro at 6:46 AM on March 11, 2019 [7 favorites]


Has anyone tried empathy?
posted by tillermo at 7:20 AM on March 11, 2019 [1 favorite]


Duuuuuuuuuuuude...
posted by SonInLawOfSam at 8:48 AM on March 11, 2019


"But if a man would be alone, let him look at the stars. The rays that come from those heavenly worlds, will separate between him and what he touches. One might think the atmosphere was made transparent with this design, to give man, in the heavenly bodies, the perpetual presence of the sublime."
— Ralph Waldo Emerson, Nature (1849)
posted by octobersurprise at 8:52 AM on March 11, 2019 [1 favorite]


ʻOumuamua object

Surely ʻOumuamuabject...?
posted by The Tensor at 9:06 AM on March 11, 2019


The unobservable Universe, on the other hand, must be at least 23 trillion light years in diameter, and contain a volume of space that's over 15 million times as large as the volume we can observe.
And here I thought the visible universe was enough to make you feel tiny.
posted by clawsoon at 9:29 AM on March 11, 2019 [2 favorites]


The rays that come from those heavenly worlds, will separate between him and what he touches.

Is it just me, or does that sentence make no sense? How do rays even seperate? And why would they seperate "between him and what he touches"? Or does he mean that the rays will prevent the man from touching....what he touches? What?
posted by thelonius at 9:45 AM on March 11, 2019 [1 favorite]


I think it’s a bad translation.
posted by Don.Kinsayder at 11:47 AM on March 11, 2019


(joke)
posted by Don.Kinsayder at 11:48 AM on March 11, 2019


I just called in sick so I can stay in bed tomorrow drink tea and follow every link in this FPP. Thanks for putting it all at my fingertips
posted by ezust at 1:08 PM on March 11, 2019


How Much Of The Unobservable Universe Will We Someday Be Able To See?

None of it, obviously.
posted by kenko at 1:53 PM on March 11, 2019 [4 favorites]


Dear Metafilter, if nothing can travel faster than light, and the universe is 13.8 billion years old, how come the visibility limit is 46 billion light years? Shouldn't it be 13.8 billion light years? Help, what am I missing!
posted by MrBobinski at 7:41 PM on March 11, 2019 [1 favorite]


During the whole time the light has been travelling, the universe has been expanding too.
posted by XMLicious at 8:35 PM on March 11, 2019 [2 favorites]


Heh, yeah, I thought the author had dropped a decimal point until he pointed out the expansion. I thought the universe was big BEFORE…
posted by Johnny Wallflower at 8:56 PM on March 11, 2019 [1 favorite]


In a brief transcendent moment last night I looked aloft and wondered how much of what we see is still there?

It depends on what we think we mean by "still" actually makes any sense with light speed and relativity.
posted by straight at 9:07 AM on March 13, 2019


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