finished 3 January 2006

This is a very readable science fiction book about how paleontolgists would use time travel to study dinosaurs in the Mesozoic. It is quite entertaining and the descriptions of how the dinosaurs look and behave is well done. Time tunnels from the present back into the age of dinosaurs are established in 2013 and for a couple decades are kept secret from the general public. After 2036, one of the scientists breaks the secrecy and from there to about 2048 everyone accepts that this technology exists. The details of how time travel works are not so well thought out, however.

The time tunnels allow them to move around in the forty years of the projects, 2013-2048, and to set up scientific stations around 100,000 year intervals in the Mesozoic, 65-248 million years ago. Nothing between. The temporal transfer technology was not an invention of the humans who are using it. It was given as a gift from some other race in the far future, known as the Unchanging. They insist that paradox must be avoided at all costs, so careful records of the time travel from 2048 are constantly consulted from 2013 onward to avoid the consequences. This makes for clumsy character interaction, often doing things just because the records say that is how they were done in the future's past. There is no physical problem when your future self meets a past self, they just have to be careful not to divulge future discoveries to past selves. It is not at all clear why consulting some of the time travel records from 2048 is not such a divulgence, but only the most future-advanced people see these memos and tell their past selves what should be done in only fuzzy terms. Clumsy plot construction here.

Eventually the plot develops when religious fanatic infiltrates the scientific establishments and sabotages the time beacon when a new station is being established in the Maastrichtian age, 65-71 million years ago, just before the asteroid extinction event will end the Mesozoic and the rich life of the dinosaurs. Blowing up the time beacon strands eleven scientists in a valley used seasonally for breeding by herds of dinosaurs. For two years they study the interactions of a local tyranosaur family with the herds of hadrosaurs and triceratops.

Less well known, there is a time tunnel into the distant future by which the Unchanging travel to study human behavior and distribute the limited time tunnels back into the Mesozoic. Apparently they can move elsewhere because they have a nexus which they are stocking with large extinct mammals from the Cenozoic and artifacts of about every human civilization. The few human administrators who can get to this Unchanging nexus are carefully controlled so they can only see things from the past of their origin.

The end of the novel is less than clear what happens when a paradox is engineered about that mission which is stranded and then the Unchanging shut down the time tunnels. There is some talk about everyone dissolving into time bubbles (whatever that means) even the really distant future beings who manufacture the Unchanging. So the outcome of all this activity is uncertain, but it makes good reading up to that point. Maybe that is the point. Time travel is futile but fun until it collapses of its own weight.

This author could have used a little understanding of fifth and sixth dimensional mechanics. Paradox is only a problem from the perspective of a single time line, the way we usually concieve our history. Time travel is only possible if time can be shaped or folded in a higher dimension. From a 5D perspective, paradox is not a problem since infinitely many time lines exist at that level. In other words, if 4D is limited to just one time line, there is no angle from which to puncture it to allow the time travel. Historians realize that there are many parallel threads of events which they try to weave into a single causal sequence so we can understand how and why history happens. Paradox is not the major problem of time travel, but it is finding the place to stand and a lever to move the time stream.