Death from the Skies!‘s nine chapters all follow the same pattern: a brief, moderately sensationalized depiction of an astronomical disaster followed by a somewhat more sober discussion of the event, with an emphasis on how likely and/or subject to mitigation it is. The book more-or-less progresses from near-term potential events (like a meteor collision) to long-term inevitabilities (the eventual death of the sun, and way beyond). Plait’s enthusiasm is palpable throughout — he just loves this stuff.
I’ve read a lot of books that covered similar topics, but if you don’t read new ones (this one was published in 2008), things tend to change. For instance, we used to think that our sun was in the class of stars that could go nova, inexplicably increasing in brightness for a period of hours or days — possibly long enough to fry the Earth to a crisp. In the current understanding, stars like ours don’t go nova; only hydrogen-gorging white dwarfs do (whew!). On the other hand, I’m a little more scared of big meteors than I used to be; turns out blowing them up with nukes probably doesn’t work at all, and even deflecting them is likely to be much harder than I thought. So while Plait’s book covered a lot of ground familiar to me, there were usually new wrinkles; I learned plenty.
One reasonable quibble I have is that Plait is a little glib about scale. Only in the chapter on the death of the universe does he rely on exponential notation, and then only because the numbers are so unimaginably huge. Throughout most of the book he uses million and billion in adjoining sentences. Even these numbers are so beyond human scale that I think they’re difficult to keep hold of; I think our brains tend to render them as “really big” and “really big (but bigger)” — it’s hard (for me anyway) to keep in mind that a billion is a thousand million and that a trillion is a thousand thousand million. It’s geeky, but I kind of wish he’d used exponential notation throughout.
My unreasonable quibble with the book illustrates why I’d make a spectacularly lousy scientist, particularly in the chapter on “Deep Time” and the end of the universe. I can accept that we can make assertions about the age of the universe and what happened to bring us to the current point — if we look at an object that’s 6 billion light years away, we’re seeing it as it was 6 billion years ago unless pretty much everything we think we know about physics is wrong. So we can learn about state of the universe 6 billion years ago by direct observation, and extrapolate backward.
But foretelling the end of the universe involves quantities of time that literally, I think, beggar the imagination. As Plait acknowledges, you can’t use metaphors — you can’t say, for instance, that the 14-ish billion years age of the universe to date is an eyeblink compared to Deep Time, because an eyeblink is way, way, way, too long. It’s certainly scientifically reasonable to extrapolate from our observations of the universe now. But for us to presume we really know what’s going to happen on those scales strikes my unscientific, intuitive mind as enormous hubris. Suppose for a second that there’s some big change in the universe that happens once every 20 billion years. It hasn’t happened once yet, but in the Deep Time scale, it would happen billions upon billions upon billions of times. That’s not a scientific notion — I certainly can’t propose a mechanism for some fundamental shift in the universe, or draw up equations to describe whatever it might be.
But what I can observe is that throughout recorded history, when we think we have things pretty much figured out, something upsets the apple cart and we discover it’s way more complicated than we thought. And, from the oldest historical records to just last week (with news story about experimental results failing to match the predictions of string theory), the strangification of the universe is happening faster and faster.
So while I don’t know when, how, or why (although pseudo-scientifically, dark matter still seems to be a bit of a wild card), I’d (intuitively, unscientifically) bet that long before the universe gets to the Deep Time that Plait describes, our understanding of it will significantly change. Probably before the sun swells to a red giant, or within my lifetime, or possibly even next week. And that’s what I love — the notion that despite our best efforts, the universe will always reveal complexities that transcend our understanding. We need something even weirder than string theory? Bring it on!
My irrationality aside, I liked Plait’s book a lot. Certainly found it thought-provoking.
Needs more demons? Nope.