In four billion years we’re due for a collision with this thing —

(Image link via Phil Plait.)

Added zoom available here.

ADDED: The action video (via Mr. Archenemy). It looks quite a bit more calamitous than I had expected.

ADDED: Galaxies are cosmic tiddlers.

Lawrence Krauss knows nothing about nothing, but on some other matters — I now realize — he’s an insight dynamo. This is his Our Miserable Future talk, of which the last seven minutes (minus the last two) are utterly absorbing.

In a nutshell — cosmic expansion will move every other galaxy in the universe beyond our light-cone (within two trillion years). After that time, even the most sophisticated scientific enterprise would find it impossible to reconstruct our contemporary cosmo-physics. In other words, what we presently understand about the evolution of the universe tells us it will become something that will cease to be understandable. What has been revealed to us is a tendency to cosmic concealment. We see the universe hiding itself.

That’s where Krauss leaves us (after a few tacked-on happy thoughts at the end). My question: If we can see that the cosmos is going to hide, so successfully that the fact it has hidden itself will itself have become invisible, upon what do we base any present confidence we may have that an analogous process of profound cosmic concealment has not already taken place? Confirming now, through mathematical physics, what Herakleitos proposed two-and-a-half millennia ago — that nature loves to hide — is it not reckless in the extreme to assume that she has been forthcoming with us up to this point?

ADDED: “Finding chameleon-like effects won’t necessarily mean they’ve found dark energy, says Adrienne Erickcek of the University of North Carolina at Chapel Hill. But it will show that screening mechanisms are a plausible explanation for our failure to measure the effects of dark energy in the local universe.”