Can you change the past?

It's rather simple really. I'll give you a ride in the Tardis.

Ah, thanks Doctor Who Very kind of you - can we go back to the Cretaceous period first?!

Might seem like a simple, silly question, but I wondered what people make of it when you really stop to think about it.

Can you change the past?

This is a really interesting question. There's a lot of debate in metaphysics as to the 'status' of the past, present, and future. Philosophers disagree on a few things:

- Does the present only exist; i.e, does the past now not exist any more, and does the future somehow exist (whether pre-determined or not?)

- Is the idea of backwards causation coherent; ie., could we do something now that alters the past somewhat? And if not, why is the future unique in this way?

- If we, as beings, are stuck on an arrow of time moving past to future, could there be other perceptions of time? I.e, could some beings exist going (as we would see it) future to past? People think the arrow of time is connected to thermodynamic laws and entropy, which may change direction in the future. What would happen to past-future causality then?

I haven't really answered your question, like a classic philosopher . But basically while philosophers agree that we probably can't change the past, they don't agree on whether it could be possible.

Of course we can! Ready for an adventure???

YES!!!

Go to the supply cupboard and I shall be waiting for you there!

*gasp*



Maybe, although I'm not entirely sure how a time machine would really work. I guess it would need to be able to reverse energy.