h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

http://news.bbc.co.uk/2/hi/science/nature/4097258.stm

"...you can pop back in time and have a look around, but you cannot do anything that will alter the present you left behind"



Would it not be more accurate to say, "the present you left ahead"?

Further along in the article:

"Clearly, the present never is changed by mischievous time-travellers: people don't suddenly fade into the ether because a rerun of events has prevented their births - that much is obvious."

Isn't there a rather a significant flaw in the logic here?

...but maybe we wouldn't remember the alternate timeline...

It's still a nice thought that you could go back and change something, a mistake you've lived to regret, but it would never be allowed, even if we had the technologycan you imagine the chaoswould you restrict yourself to something personal? Or warn the authorities about atrocities about to happentrying to save people could get messy, if the technology was secret, you could be blamed for the thing you're trying to avoid

Have you ever seen the film "Timescape"?

Not only would we not remember the alternate timeline, (assuming the existence of such), it would be for us as if the alternate timeline never existed.

If there were alternate timelines, and if we could somehow shift from one to another, we would then neccessarily carry with us our memories -- and hopefully be able to pack a lunch!

The rational flaw is similar to that underlying Picard's famous line in Star Trek TNG: "Reality as we know it would cease to exist." --

We are *in* reality, as it were, and therefore cannot *know* reality as separate from ourselves. We therefore cannot possibly be aware of any alterations or changes.

But let us examine this idea further:

Perhaps existence/reality *is* in a continual state of flux, rearranging 'itself' moment by moment. How could we know?

For the most part, we seem to be inescapably time-bound by the 'slightly-out-of-step' perception of our nervous systems. This built-in talent for 'abstracting' -- thought, gives us enormous creative ability: Invention, art, music; but because of its misplaced application we tend to be easily deluded.

We are dazzled by the brilliance of our own minds, and of others, thus becoming enmeshed in prisons of beliefs, and even more particularly belief in a peculiar construct of memory -- personality.

Fear and desire enchant us into believing that we are somehow separate from an 'external reality', and the persistent illusion that this is who we are.

We are not busy little fish in the river, but the great river itself.



I have seen a movie called 'Timescape', also called 'Grand Tour: Disaster in Time', in which a man encounters a group of 'time-tourists'
Is that the one to which you refer?

http://www.imdb.com/title/tt0104362/

Yep, that's the one.

He manages to change his timeline.

I've just pinched the computer off Andrew to tell you he's been playing on Celestia since he came home from school

Perhaps his school may be interested, especially in the educational components of the program...

Have you checked out the plugins/addons?

http://www.celestiamotherlode.net/

Indeed, we are reality. Hey! Look at me! I'm reality!

How could it be otherwise?

http://news.bbc.co.uk/2/hi/science/nature/4676751.stm

The school do use "Celestia", it's why Andrew bothered to load it.