This is something I have wondered for some time now. And I realize it has no precise answer. But humor me a little.
Consider the following example: Somehow I travel back in time, one thousand years. And I go to the exact spot of George Washington’s ancestral home in England. (I choose this location, because I assume that there will be a lot going on there, even at this early date.) I don’t do much there. In fact no one even sees me. But I dislodge just one pebble on the walk to the house (or what will be the house there).
How much effect could this have on the future? Not much? Or probably a lot? Will whole empires never exist? Will the future as we know it be radically different? Will the USA as we know it never exist? Or will it in fact have little effect at all. Please give your best educated example (even if you don’t consider yourself that knowledgeable).
There have been examples in time travel literature ranging from the slightest change will have major long-term effects (Ray Bradbury’s “A Sound of Thunder”) to that it takes much work and effort to make the slightest change (Fritz Leiber’s “Try and Change the Past”) to even more complex possibilities (George Alec Effinger’s “The Bird of Time Bears Bitter Fruit,” where the past is a consensus reality that can’t be changed or Alfred Bester’s “The Men Who Murdered Muhammad,” where you can only change your own personal past, which diverges from the main timeline). And there are probably hundreds of stories with all sorts of speculation as to what can be done.
I’ve wondered about the same. I’m guessing that if you could delay G Washington’s ancestor for 15 minutes on the evening of the conception of his great great Grandmother, that the path of history might change. A different victorious sperm cell would probably produce a different history. Benedict Arnold, no longer miffed, may have led the US to victory and become our first President.
As for the OP, doing that would change the configuration of molecules in the world. Humans may or may not find the change especially significant, but that’s anthrocentrism for you.
Moving a pebble is unlikely to make any difference. Highly unlikely. Could you even tell if a pebble was moved on the walkway to your house now? The coincidences required to have that make a difference are extraordinary. Perhaps the pebble was used by George’s great uncle to hit some local fellow in the eye, resulting in an infection that killed him, thereby leaving an opportunity for George’s great grandfather to join the clergy resulting in his son not traveling to America to become a tobacco farmer (not sure if I have the lineage correct there). How likely is that to occur? Not very. Could it? Sure, but don’t you think it’s far more likely the guy gets hit in the head with the pebble, kicks the shit out of Georges’s great uncle and nothing more ever comes of it?
It’s incredibly unlikely that moving something as huge as a pebble, over time spans as long as years, would fail to make a difference. All it takes is one chaotic component in a system, and the whole thing is chaotic, and we know that some things are chaotic.
Moving that pebble will result in radically different weather patterns, a few weeks out. Could those change history? Certainly. The weather means that people will interact at least somewhat differently. Every child born after that point will be the result of a different sperm fertilizing an egg, which means that a generation later, the cast of characters of history is completely different. Basically, change anything at all, and you’re rolling all of the dice all over again.
In my view there are two different aspects to this question. One is the “chain of causality” aspect. If I were to take my now-empty cup of coffee and go downstairs right now, how would it change the future vs. just sitting here for another few minutes? One could make up a scenario where it changed things very profoundly indeed, but one would have to recognize such a scenario as extremely unlikely and the whole discussion to be of interest only as a philosophical curiosity.
The other aspect is to recognize that the only way you could go back in time – indeed, the only way the concept is even semantically meaningful – is to enter a parallel universe. Such parallel universes have actually been hypothesized to exist, as for example in Hugh Everett’s “many-worlds” hypothesis. The question then has more to do with what particular universe you happen to have selected and how that selection was made among the infinity of universes in which all possible outcomes have all occurred. It would have to be one in which by definition your appearance at that point in time was part of the history, but nothing else is guaranteed … you’d have a lot more to worry about than dislodging one pebble – this might well be a universe in which George Washington had never been born, or in which an asteroid wipes out the earth in the year 1873. If one is going to be allowed to go back in time and change the future in arbitrary ways, then there is a vast – an infinite – plethora of universes one could end up in!
“Stephen Wolfram also notes that the Lorenz equations are highly simplified and do not contain terms that represent viscous effects; he believes that these terms would tend to damp out small perturbations.”
There is also the concept of the “predestination paradox”. Basically the idea is that if you went back in time, any actions you performed are already part of history.
Sort of like Kyle Reece being sent back in time to be John Conner’s father.
This also lends itself to the “bootstrap paradox”. The existence of an object or information in the timeline with no creation point. Like going back in time and giving George Washington that old pocket watch that was supposedly in your family for generations going back to the American Revolution where it was given to one of your ancestors by George Washington.
Sort of like Fry from Futurama being his own grandfather.
Is the physical universe deterministic? If it’s not, then replaying the world from any historical starting position, even without changing a thing, will most likely result in a different outcome.
The pocket watch that’s been handed down through generations, can’t be exactly like it was way back when. Corrosion, wear and tear, staining etc. adds and removes material over the centuries. So unless something miraculous happens to it to restore it to the original state, that loop is impossible, or it’s a temporal spiral rather than a temporal loop.
A different outcome to the War of Jenkin’s Ear leads inevitably to a change in the War of the Austrian Succession. Therefore, the great Fascist Threat of the mid-Twentieth Century was centered on Ruritania, not Germany, and Oreos are a vanilla cookie.
