[cautionary note] This post relates to an article that is about 4 years old, but someone pointed it out to me today and was I intrigued by it - so my apologies if readers have already seen discussions of this before
I've been a long-time fan of convergent scientific realism, which I hold to have the following properties: some scientific theories are at least approximately true, and they genuinely refer. The history of mature sciences is a progressive approximation to truth. (This is just offered as a quick definition of convergent scientific realism, not a technically correct definition). Convergence seems to imply that as time goes by and scientific theories change, they move closer to the truth. While convergent realism is usually invoked in a backward-looking way to explain changes in theory-formation, one expects on the basis of it that - if the current scientific climate does not collapse due to budget cuts, religious fundamentalism, or whatever other threats - we will know more and more about the empirical world. A few years ago, Krauss and Scherrer published a paper in Scientific American (The end of cosmology?) and in some more technical journals that challenged these assumptions. According to them, we live in an epistemically privileged age. "We may be living in the only epoch in the history of the universe when scientists can achieve an accurate understanding of the true nature of the universe" (p. 47).
As is well-known today, the speed of the expansion of the universe appears to be increasing. The prognosis is that the universe will become, in the long term, inhospitable to life. But before it does so, something else will happen: our universe will become more epistemically opaque. In about 100 billion years, our local galaxy together with other nearby galaxies (Andromeda etc) will collapse into an enormous supercluster of stars. All other galaxies will disappear beyond the event horizon, i.e., an (imaginary) surface beyond which no matter or radiation can reach us. What could inhabitants of this island galaxy in the seemingly for the rest empty, static void know? Well, for one thing, they would not observe galaxies receding from them. Also, they would not be able to detect background radiation, as it would be undetectably dilute (very faint at bout 10^-30 kelvin), and the original chemical mix of the early big bang would become contaminated by multiple generations of stars. Even if future scientists were able to pick up the background radiation, in the absence of these other clues they would probably discount it as noise from a more local source. In sum, even if our progeny were able to leave the Earth, colonize other star systems, and science would continue to expand, they would not be able to ever infer the big bang occurred (perhaps if scientists could keep records for billions of years as in the Asimov Foundation series?) The authors conclude: "The window during which intelligent observers can deduce the true nature of our expanding universe might be very short indeed." (p. 53). Also, it seems quite plausible that some clues in the past have already been wiped out by the process of the accelarating cosmic expansion.
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