It has been a few years since I finished MANIFOLD: SPACE by Stephen Baxter. This book was a sequel of sorts to his earlier book, MANIFOLD: TIME, and I believe there is a third in the series called MANIFOLD: ORIGIN (which I haven't read).
I say "sequel of sorts" because they were two pretty different stories. Both feature the same protagonist, Reid Malenfant, but they tell stories that are actually set in different universes, and there are only a handful of other characters who carry over from the first book to the second. (One is Malenfant's significant other, Emma Stoney, another is a congresswoman whose name I can't come up with off the top of my head, without either book in front of me.) Only Malenfant is important to both stories.
Both are broad stories, with far reaching implications, and tons of hard science. In the first, something called the Carter Catastrophe is discussed, which loosely states that the odds of these characters living in the very early stages of humanity's existence are pretty long. The example Baxter has his character Cornelius use in the first book is that there is a box with balls in it. One of those balls has Malenfant's name on it. He says that there are either 10 balls in the box, or 10000. Then he begins decanting out the balls one by one. When Malenfant's ball comes up on the third or fourth ball, Malenfant makes a guess that there are only ten balls in the box, since it would be highly unlikely that his ball would come out third or fourth if there were 10000. And this is the argument of the Carter Catastrophe, if I understand it correctly; that the odds of any of us living this close to the beginning of humanity's ultimate span are pretty long ones. So, goes the argument, there is likely to be a catastrophe which will make this time period closer to the middle, or even more likely, the end of human existence. (Seemed like a logical argument with plenty of holes in it, to me...)
Anyway, in this first book, a message is received (through the quirks of quantum mechanics) from the distant future, and it is discovered to be coordinates. So Malenfant's corporation, the Bootstrap Corporation, racing against government intervention, launches a manned probe to the asteroid they've been directed to. Meanwhile, strange children are being identified - kids who seem to have superior mental faculties. And they frighten people. So they are placed in special schools for their own educational needs, and for their protection, but actually mostly to keep control of them.
In the second book, Malenfant is on hand on the moon (controlled by Japan's industrial complex) when the discovery of an alien presence in our solar system is discovered. Malenfant ends up being the one chosen to go out to meet the aliens, and when he arrives at their location, he finds a sort of gateway - a teleportation device. He decides to go through it, and meets up with the Gaijin, a robotic race advancing through the solar system.
Meanwhile, back in the solar system, the Earth becomes a devastated wasteland because of environmental damage, humans terraform their moon, and they have to repel an attack on the Sun by an alien species called the Crackers (because they crack Suns - exploding them for their own purposes of energy).
Pretty broad stories, as I said. In the end these stories are pretty optimistic, and they are loosely connected, as the events of the first book help to create the universe that the stories occur in the second.
Baxter doesn't try to describe his aliens too much, leaving most of their characteristics to the readers' imagination. Their motives are, for the most part, not understood or even really attempted to be understood. But in the end, Baxter seems to imply that aliens that we encounter might be more like us than not, simply because the traits needed to expand their horizons are likely to be common between races.
I found both of these to be good reads. They took me a lot of time to get through, and I think this is because they are long and detailed. Not many wasted words or storylines.
As noted previously, the first book discusses an idea known as "The Carter Catastrophe." Here is the link to the Wikipedia article that talks about it: Doomsday Argument
Baxter gives one example of the argument in his book. Here's another: You have two urns, one with 10 numbered balls, one with 10000 balls, but you don't know which is which. You remove one ball from one of the urns, and it is numbered 7. You can logically infer that it's from the one with 10 balls, because the likelihood of an early ball coming out of the other is pretty low.
Based on that statistical argument, it's argued that since you're here today, it is likely that you are in the last 90% of humans to be born, and less likely that you are in the first 10%. Since humanity's growth is exponential, the last 90% of the people would be born near the "Doomsday" of humanity.
To me it doesn't make sense, because SOMEONE'S gotta be among those first early humans, and it just so happens that it's the consciousness that is identified as "me". There's nothing special about "me", "I" could have been born at any time.
Someone in an internet discussion I found mentioned that the argument would be able to be made by every single person at almost every single time in "history" (or something like that). Someone else mentions that the sample size in that statistical experiment is exactly 1, and thus is meaningless. If you took out the first 10 balls, and they were 1 through 10, maybe that would mean something...you'd pretty much know with pretty high certainty which urn you were drawing balls from. Conversely, anything higher than 10 on the second draw means with 100% certainty that it's the urn with the much higher number of balls.
It's an interesting thought experiment, and Baxter uses it as an argument given by one of his characters, but doesn't necessarily endorse it as true or as good logic.