Time travel?

[cee-dee]

I think people that believe time travel is possible are deluded!

https://www.express.co.uk/news/science/1109426/Time-travel-proof-time-travel-possible-physics-time-t...

How can you travel to "The Future" when the future hasn't yet happened?

[right-then-petal]

Everything Is Possible In The Fullness Of Time

[upthecreekyetagain]

It seems far more logical to be able to travel to the future than it is to travel back to the past.  We already know that astronauts on the space station are travelling to the future albeit by a very small amount.

Time moves ever more slowly the more the speed of light is approached.  So if you could travel at a very high speed what may be just  days for you could be years for those you left behind so on your return you would in effect have travelled years into the future.

[cee-dee]

By that reasoning, when you return you go back again!

[upthecreekyetagain]

The theory of Special Relativity simply predicts that the faster an object moves relative to a stationary observer the slower time passes for the traveller.

When Scott Kelly returned from the International Space Station it was calculated that he was 5 milliseconds younger than he would have been had he remained on Earth for the 520 days he actually spent in Space.

Of course the ISS is only travelling at a tiny fraction of the speed of light compared to the Earth - to travel any realistic distance into the future speeds would have to be much higher.  It’s not acceleration that causes this time shift but relative speed therefore the time shift remains permanent.

https://www.space.com/33411-astronaut-scott-kelly-relativity-twin-brother-ages.html

[cee-dee]

The idea of time travel is that whoever "travels" does so to "the future" and they're thinking of the future on Earth. For instance seeing what places and people look like "in the future".

The fact that a space traveller might end up "younger" than he would have done had he stayed on Earth is hardly travelling "to the future". He might be "younger" but the World he left and returned to is not a "different future" than it would have been had he stayed.

[plpmr]

I agree with you.

also - 

"According to Gaurav Khanna, a professor of physics at the University of Massachusetts Dartmouth, we are always moving into the future one second at a time"

If you think of it we actually live in the past [allbeit seconds] as until something happens we cannot experience it

[bankhaunter]

Manipulating time can lead to much confusion.

The great Cathedral of Chalesm was scheduled for demolition in order to build a new ion factory. However, due to delays in construction and a strict deadline for the start of ion production, the beginning of the project was extended so far back in time that the cathedral ended up never having been built in the first place.

As a result, picture postcards of the cathedral suddenly became immensely valuable.

And blank.

[upthecreekyetagain]

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@cee-dee wrote:

The idea of time travel is that whoever "travels" does so to "the future" and they're thinking of the future on Earth. For instance seeing what places and people look like "in the future".

The fact that a space traveller might end up "younger" than he would have done had he stayed on Earth is hardly travelling "to the future". He might be "younger" but the World he left and returned to is not a "different future" than it would have been had he stayed.

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I don’t understand your logic.

If I were to travel out into space at very high speed for say 1 year and then returned to Earth then the Earth would be much older than when I left.  Depending on the speed I had travelled at then I could, for example, be 100 years in the future.  That is time travel.  The longer I travelled for and the faster I went the further into the future I would have travelled.

What I couldn’t do though is go back in time to when I left.

[cee-dee]

Your logic is flawed. Using your "example", theoretically you might be considered to be 100 years "in the future" but where you returned to would only have advanced by one year so your "time travel" has achieved nothing.

I did say that the idea most people have of time travel is travelling to the future and that idea just isn't possible.

If we're taking one year in time as the time taken for the Earth to revolve once around the Sun, then that year is just that, ONE year, story, end of! 

[celticthebhoys585]

Clare Randell did it in "Outlander" - so there, job done!

[upthecreekyetagain]

One year on Earth could appear to be just 1 second if you were travelling fast enough.  If you could watch the Earth as you were travelling it would appear as though you were fast forwarding time and the Earth would only be taking one second to travel around the sun.

When you landed back on Earth you would be in the future.

[cee-dee]

If you were travelling fast enough 1/ you wouldn't be able watch the Earth travelling round the Sun and 2/ the future you landed back on would be the same future as those on Earth.

Just travelling at the speed of light is around 670 million miles per hour and at that speed you'd never control a craft to make a revolution around the Earth close enough to view the Earth.

The whole thought of "travelling to the future" is wishful thinking.

One thing that's forgotten in all this daft "speeding through Space" is that first you've got to accelerate and then you've got to slow down which all adds "time" to the time spent travelling.

[upthecreekyetagain]

That’s why I said “IF you could see  . . .”

Landing 100 years in the future on Earth after 1 years travelling in space would be travelling to the future.

Of course it would be the same future as for those who remained on Earth but they had to wait 100 years to be there whereas the traveller had got there after just 1 year.  That is time travel, exactly the same as getting into HG Wells’ time machine waiting some time then getting out of it in the future.

[cee-dee]

That's just not so. One year of Earth time is one year. To travel forward 100 years the traveller might travel a year in supposed space time but it's still 100 years in Earth time.

A chap leaving Earth today and travelling for one year at whatever speed you think he might is travelling for one year and when he returns on April 4th 2020 he'll see the Earth as do the rest of us on that date.

Although I've often said that if man can think of something, one day he'll do it but there are limits to that and time travel is one of them.

Somehow I don't think we'll ever see a lost Victorian time traveller:- 

[upthecreekyetagain]

Of course those on Earth will have “lived” the 100 years that have passed on Earth but the point is that the space traveller won’t return to Earth just 1 year after they left in 2020 but 100 years later in 2119.  In other words they will have ‘jumped 99 years into the future when most, if not all’, of those they left behind are dead.

The 100 years of “Earth time” is just 1 year in “travel time”.  That’s time travel.

[cee-dee]

I think those that believe in time travel should be grouped with the flat earthers!

Just think about it for a while? How to leave Earth's gravity? How to accelerate to 670 million miles per hour? (and that's only at the speed of light!) How to avoid the umpteen billions of bits of dust plus other space objects? Just where are you gonna go? By my reckoning (is it flawed?) in a 100 years at the speed of light you'd travel around 600,000,000,000,000,000 miles. How the heck do you find your way back? How're you gonna decelerate? How're you gonna re-enter Earth's atmosphere?

Now it's OK saying that Man has overcome lots of what were major obstacles in scientific advancement in the last 250 years, things that were beyond comprehension for people before then BUT... there's limits to everything. Time travel is beyond Man now and in the future!

[upthecreekyetagain]

You forget the basics of the theory of special relativity.  Time is not only distorted by speed but also by gravity.  A number of black holes have been discovered that may well be beyond our ability to travel to now but not at some time in the future.

In any case a “time traveller” would not have to travel anything like a 100 years nor even 1 year if travelling at or near the speed of light in order to “jump” 100 years of Earth time.

[cee-dee]

That's all a world of fantasy. Although we've made terrific advances in the last 250 years, if we were still around to see what the next 250 years will bring, time travel will not be one of the "advances" we'd see.

You know what the retort is when someone comes out with a theory? Prove it? The retort to that is usually "disprove it" so round and round we go?

[upthecreekyetagain]

I don’t think we’ll see time travel to the future as an aim, what would be the point if you can’t then go back in time.  I’ve no doubt though that if man as a species survives we’ll see it as a by-product of space exploration at sometime in the future.

Travel to the future would be no different in reality to putting someone into some form of suspended animation where the body didn’t age and then waking them up at sometime in the future.