Science philosophy in the NY Times

[steuard]

Brian Greene wrote a NY Times op-ed about the implications of the accelerating expansion of the universe. As he says,

Because of this, when future astronomers look to the sky, they will no longer witness the past. The past will have drifted beyond the cliffs of space. Observations will reveal nothing but an endless stretch of inky black stillness.

Comments

[nasu_dengaku]

Quick thought -- it seems like this is the sort of issue historians deal with all the time. It's a hell of a lot easier to determine truths of the Battle of Gettysburg if everyone can observe it happening. However, we only have primitive accounts of the event by people who were busy commanding armies and/or being shot at. It would be a lot easier for historians if they could re-run the Battle of Gettysburg over and over in a lab, but they can't.

As for missing technology to observe things, I think cosmology is moving so slowly that we'll be either all dead or a galaxy-spanning intelligence by the time any of these issues come around.

What isn't changing slowly, however, is our civilization, and the transitions that will take place over the next 100 years or so should be unprecedented. There's probably a lot we can learn about emergent order in complex systems and numerous other things that we're just not observing right now, and will never get to observe.

[steuard]

Well, yes, the time scales of cosmology are a wee bit slow: the issues here aren't all that likely to be relevant for any given civilization. But I agree that similar sorts of phenomena may show up in other areas of human knowledge.

As for historians, I'm probably just a snobbish physicist. I've always taken comfort in not needing to trust the ancients on anything, knowing that I can always just check their claims myself if necessary. It's startling to think that my field isn't as immune to that as I thought.

[robbbbbb]

"It would be a lot easier for historians if they could re-run the Battle of Gettysburg over and over in a lab, but they can't."

Who says?

(I kid, I kid.)

[steuard]

Hey, we've got a copy of that! Never played it, though: a bit in-depth for our usual gaming groups. How is it?

[jon_leonard]

I was under the impression that the it was more that remote galaxies would redshift toward invisibility rather than simply leaving us with a black sky. Not that (given enough time) it makes that much of a difference

[steuard]

No, it really is honestly a black sky (outside of our galaxy), which I find at least mildly terrifying. The accelerating expansion of space will (according to current theory, which may of course be wrong) become increasingly rapid until "new space is being created" between galaxy clusters faster than light itself can cross that space. So not only would the distant photons be extremely redshifted, but they'd also become increasingly rare (as only the ones that were right "on the edge" of making it to us would keep trickling in).

Good point about historical records, though. Especially if we manage to come up with some fundamental theory (with locally testable predictions) that implies a value for the cosmological constant, that would give future scientists a reason to believe our crazy stories about countless distant galaxies. (I hope those future scientists aren't as dependent on data from the CMB for progress as we're likely to be, though!)

[kirinn]

It occurs to me that what this phenomenon really gives a deadline for is *visiting* other galaxies. Take too long and civilization will miss that boat permanently. Well, short of utterly breaking the laws of physics as we know them.

[jon_leonard]

I guess I was making the trivial point that under a relativity+classical electromagnetism model, the effect shows up as an endless shift towards red. New light from the object can't reach us anymore, but it takes forever to clear out the light in between.

In terms of photons, there is some last photon (assuming certain kinds of expansion: A simple continuous linear expansion never expands to unreachability), but it takes a shockingly long time to go from the very-red-sky mode to an actual black sky. Would there be any stars left at that point?

[steuard]

I'm considerably more fond of the short story than the novel. But yeah, now that you mention it, that's a great antecedent to this sort of philosophizing. The question, I guess, is whether the knowledge will be passed down as formal scientific data or (as in Nightfall) merely as mythology or "lore".