# Can Earths be added to the chain?

In Pratchett/Baxter's The Long Earth, people learn how to 'Step', i.e. travel to another version of Earth where the dice were rolled differently. On some versions of Earth, the asteroid that killed the dinosaurs never hit, on others evolution lead to marsupials the size of brachiosaurs, others yet have seen some catastrophic event melting the poles and flooding most of the world, or the Himalayas never got formed.

In short, every Earth is separated from its neighbours by a degree of chance. For every event, there is an Earth that has had it happen, and one where it didn't. That doesn't go for every leaf that falls from a tree, but it does for the bigger things.

Thus far, every Earth shows what might have been based on events in the distant past (and I realize, we have a lot of 'past' behind us). I was wondering what would happen if we would have a major event in the present.

• Would a new Earth be added to the probability tree where it does or does not happen?
• Or would the number of Earths double (half of them having their history and evolution until that point plus the 'event', and the other half without it?).
• Or is the chain immutable, meaning that everything that can happen, is already predestined to happen on the worlds in the Long Earth? This would imply that there are at present (semi-)equal Earths that will start to differ once, in the future, this event does(n't) happen.
• Or would you imagine this working in a different way?

Additionally, all of the above are factors that affect one world only. How much of an impact do Steppers have on the above, by crossing over the probability boundaries?

Note that I'm currently nearing the end of Book 1, so if the above gets answered in later novels, please just say so.

• I think you overthink it. Wasn't the main component of the device that enables one to step a potatoe? Isn't one author Terry Pratchett? I don't think that the book is meant to be taken seriously. Also if I remember correct, our earth was the only one with native "humans". All other humans on all other earths were steppers from our earth, right? So I don't think the story examines the quantum tree idea that every possible alternate reality is present on one of the earths. Also remember that its a chain of earths, not a tree. To map a tree to a chain seems not what they've done here. – Hothie Aug 17 '17 at 10:53
• @Hothie I get what you mean; knowing Pratchett, the technical details take a back-seat to the idea itself. However, that idea did plant the seed fr my question. I'm not concerned with 'mapping the tree', I want to know how/if/when this tree shoots new branches. – steenbergh Aug 17 '17 at 10:57
• I think your premise is faulty. At least in the first book (the only I know) it is not explained how the earths where created and why exactly that earths are existing. While in general neighboring earths are often similiar, there are also two neighboring earths with nothing in common. And the fact that only on one earth there are humans, rules out the possibility that every possible earth is manifested. So I don't think that there are earths added. There are just X earth perhaps with the same starting point, developing independent of each other. – Hothie Aug 17 '17 at 11:12
• @Caleth: We have can an infinite numbers of earths with the only difference being that, for example, G at one spot is not the same, but slightly different. To simplify it extremely, let's assume it's 9.81 here, in the next world it would be 9.811, int eh next 9.8111, etc.etc. This would lead to an infinite number of earths, all almost equal. But this would not necessarily imply that these infinite earths include all possible earths, since, for example, the color of a red rose somewhere else would not be suddenly blue just because G changes on another spot. – Florian Schaetz Aug 17 '17 at 12:25
• Or you could have an infinite number of earths where the only difference is that Charlie Joe doesn't weight the same. In our earth, his weight is exactly 80kg, in the next it is 80.00001, in the next it's 80.0000100001, etc. This leads to an infinite number of Charlie Joes, all pretty much equal, but not absolutely. And still there is not ONE earth among them where Charlie Joe has blue hair. So you can have an infinite number of earths, all only differing in one very small detail without having all possible earths. – Florian Schaetz Aug 17 '17 at 12:29

The concept of Stepping is further evolved and explained in the next books so be patient. I don't want to spoil you the surprises completely. But exactly this question is not answered completely. Certainly, Long Earth does not work as Florian Schaetz is trying to point out about the infinity. It is not a list of impossible small changes, but something like all the history of Datum Earth somehow modified by past events that happened or not with some close-by adjustments that create belts of Earths with similar climate.

In later books, the stepping is also described as a mental process, more than a physical, so the concept of the Long Earth is basically created in the minds of sapient inhabitants of the Long Earth. This makes it even more harder to gasp in this question, but I believe it is important to say here.

So to the questions?

Would a new Earth be added to the probability tree where it does or does not happen?

That is not how infinite works. It is just infinite chain (at least the end was not discovered yet West nor East). There is no probability tree. It is still a chain where things in the past happened or not. Current events affect only the current Earths to the book experience.

Or would the number of Earths double (half of them having their history and evolution until that point plus the 'event', and the other half without it?).

Doubling would make sense again in the probability tree, but it does not have in the chain. It would mean that you could find an earth, that was already destroyed by People, but let's say without the Yellowstone eruption. They did not find such earth yet and I don't think there is one.

Every Earth is unique. You see different geological events, evolution steps of non-sapient species. It is hard to cover the sapient species when you see them crossing from earth to earth, but they (well ... people, trolls ...) had to evolve from something (considered non-sapient) so they could have create the Long Earth.

Or is the chain immutable, meaning that everything that can happen, is already predestined to happen on the worlds in the Long Earth?

That is very philosophical question. This was not stated anywhere so I would not like to guess this.

Can Earths be added to the chain?

The earths are living their own lives to some extent and (spoiler alert) there will be some change in the chain in book 4. It is not an addition, but a removal. But I would not call it a common practice.