Surely time travel is impossible- if nobody has already come back from the future?

Answer 1

Well... time travel is possible. I am currently travelling forward in time at the rate of aproximately 1 second per second. And people travelling quickly can travel forwards in time even quicker.

But as for travelling backwards in time... It is possible that you cannot travel backwards to a time earlier than the time machine was created. And it is possible that while it is possible to send elementary particles back in time, it is not possible to send anything complicated back.

There is also the option that anyone wise enough to build a time machine, is also wise enough not to change history, or show themselves to the natives.

Our current understanding of the laws of physics do not rule out travelling to the past, but most of the options involve exotic matter or unlikely arrangements of black holes.

Incidently, if you can travel faster than light then you can travel backwards in time. Lots of sci-fi films and books seem to ignore that side effect of >c velocities.

Answer 2

I think this has been alluded to in older answers about time travel. Time travel is not impossible in theory. Subatomic particles do it all the time going back and forward in time tiny fractions of a second - all part of the strangeness of quantum mechanics. I keep hearing people say if you go faster than light you can go back in time - now THATS impossible. To accelerate even TO the speed of light (for something with any mass like a spaceship or even an atom) you'd need infinite energy - which doesnt exist. If time travel did become possible then I would think they'd be some strict guidance as to its use. If they find little holographic wrist watches in an undiscovered Egyptian tomb then you'll know that not all time travellers make it home safely.

Seriously though its not like they'd just announce their presense - if nothing else it would cause a paradox that would stop them from ever returning home - maybe just because it would create a parallel timeline (this is where Back to the Future got it wrong, talking about different time lines and still having paradoxes). If you want to really find out more you can read books like the Fabric of Reality by David Deutsch which discusses the possibilities. You could do an internet search on 'closed timelike curves' which is what physicists call methods of time travel using relativistic terminology. Regards!

Answer 3

Think of time as being a long line, and say we're halfway along it. If we invent a time machine, it may be possible to start whizzing in either direction along the line - but we haven't invented one yet, so how can anyone from the future be using it?

If we invented one tomorrow, then we might find people from the future suddenly start turning up.

Time travel into the future is not only possible, but already happens, Einstein's famous theories show us that. But for the effects to be evident, we'd have to be travelling at unimaginable speeds. From a purely scientific point of view, there is no reason in physics why you should only be able to go one way in time - but whether or not we'll ever know how, or have anything like the technology to do it is another matter.

Answer 4

Consider this - If time can truely be defined as a 4th dimension, then any particle will occupy a single point along it's axis. As time fluxes forwards the time coordinate will change, thus returning to a prior coordinate would be futile as all particles will have moved on to what you might call 'base time'. (Not withstanding quantum complexities that allow elementary particles a potential to vibrate either side of the base time by a tiny amount.) Think of time as an infinite tube, and of everything which exists as a thin membrane that moves in one direction - once it has passed a point there is no residual existance. For it to be otherwise would require the spontaineous and near exact duplication of the entire universe with every passing quanta of time, which would need an inconceivable and constant source of energy.

Answer 5

How would you know if nobody ever came back from the future?

If they could pull it off, they may be aware or afraid of the consequences of "killing your grandfather" and may be staying out of past events.

They may have a "Star Trek" like concept about not polluting history with a bunch of future junk,

They may have "altered" history causing changes we never would be aware of. If someone went and prevented you from being born, then you wouldn't be here to complain about the injustice of it all!

Answer 6

If we succeed in travelling faster than light ,we might be able to go to the future but not in the past.

So,that our future generation people haven't come to past doesn't mean that time travel is not possible.

Answer 7

One of humanities greatest dreams is time travel but the implications are huge. If you go back in time your plain presence, even if you go unnoticed might set in motion a chain of events that would change or destroy the world we live in. For instance, you go back in time, and you carry a bacteria (we at all times carry more but just for the sake of argument let's say it's just one), the humans in that time might have not yet developed an immunity to that bacteria or strand of virus that we 21st century humans are immune to. without a cure, they would die out...you just killed the entire human race. a person that is placed in a time that is not his or her own unwillingly might cause any number of disasters. so maybe....the humans in the future are wiser and more cautious than us.

Answer 8

of course time travel is impossible.. theres no such thing as time... it is a human creation to allow mankind to be able to deal with the staggering immensity of something we other wise could not comprehend, changes of nature... if time was natural we wouldn't need to change the clocks twice a year lol

Answer 9

Hello Tom, this is you from the future. The numbers for next weeks lottery are 2,17,22,23,30. The bonus ball will be 12.

Answer 10

well who said they have not come back? Read the books printed long ago for todays world. What is written did not exist then!