Predicting the Future and Light Speed

[ejproducts]

This is probably the stupidest question I have ever asked, but it is bugging me and I am looking for an illuminating answer - not one that simply tells me I have the wrong idea, but one that explains in what way I have the wrong idea.

I can, based upon some knowledge of initial conditions and some equations, predict a future state of some system. For example, I can predict the next eclipse. Now, this prediction is based upon information that I have at the present, and some of that information is the initial conditions (where the sun, moon and Earth are now) and some of that information is the equation (how they move). With this information, I can know information about a future state before it happens.

Here is the troubling bit. I know that information cannot exceed the speed of light, and if it did it would be virtually or practically traveling into the past. But when I have information of the future state of something, that seems like information "from" the future, or at least, virtually indistinguishable from information from the future. That would entail, of course, information traveling faster than the speed of light. Yet I am pretty sure this hasn't happened - no information has been transmitted in the traditional sense from one location to the other.

However, when I think about this example backwards, I feel like information has been transmitted. If I calculate an eclipse that happened in the past, it is by virtue of it happening in the past that I have the information with which I can calculate the previous eclipse. The fact that it happened contributed to my current observations which I use as my initial conditions, though I set time to -1 to calculate the past.

Why doesn't predicting the future violate the speed of light? What is different about the circumstance or the information in this case?

 

[Doc Al]

I don't understand why you'd think that predicting the future would violate the speed of light, since you seem to agree that no information is being transmitted. Your prediction of a future eclipse, for example, is only as good as your model and your current data. (There may well be additional factors currently unknown to you that will prevent your prediction from coming true.)

 

[ejproducts]

I see what you mean. But let's assume it is a simple set of states that I have complete knowledge of, and I can predict a future state with complete accuracy as I have managed to discover all the laws of physics. This then removes the impediments of unknown elements as far as I can see. Although this is a theoretical and unrealistic state of affairs, let's go with it.

When I build my model, the information for my model comes from somewhere. If I build a model to calculate a past state, the information for my model effectively comes from that past state, the information having traveled through time to the present state, where I can extrapolate it by creating my model. So there is no problem with this, because my information got to me by the "regular route" - all the information I calculate for the past state I calculate with the information from the past state having traveled to me at the speed of light or less.

But when I calculate a future state...

Wait, I think I've figured it out. In this scenario there's only one set of information, isn't there? So when I calculate the past or the future, I don't have any new information. Is that right?

 

[Doc Al]

Wait, I think I've figured it out. In this scenario there's only one set of information, isn't there? So when I calculate the past or the future, I don't have any new information. Is that right?

That's what I would say. If you can predict the future with 100% accuracy, then the future itself holds zero new information. You already have all the information.