Time travel possible?

Gurgle

Hellrazer wrote: »

These wormholes are called Einstein-rosen bridges?Again I remember reading up on these a while back and the theoretical possibility of building one using a "gravity tractor" I think it was called.Something about gathering enough mass in one place to collapse space into an artificial black hole on one side and on the other side of it is an artificial white hole.Could be used as a bridge between 2 distant points in space.

Interesting concept but could it ever be a possibility?

Theres all kinds of notions about how to make a wormhole, mostly involving exotic matter, condensed matter, white holes, black holes... basically they're all based on hypothetical solutions (read: guesses) to stuff we don't understand.

On the other hand, in a sense 'Galactic Lensing' is a natural implementation of a wormhole - Basically when a galaxy moves between two points, they are closer together through that galaxy (due to the effect of its mass on spacetime curvature) than they are when it isn't there.

This also gives an indication of just how much mass would have to be simulated / assembled by the gravity tractor / black hole / condensed matter to implement a wormhole.

And also wondered since space and time are interlinked would the "bridge" not warp time aswell as space causing some sort of time distortion?

Yes, in the sense that the connected ends of the wormhole could be moving forward in 'absolute' time at different rates.

There is still no real physical theory that would allow backwards time travel.

ladyofthelake

Very simple, the closer that you get to the speed of light, the more time slows down for YOU, the rest of the time stream passes at the normal rate. So, if you were to travel for only a few years at light speed and left the earth, when you came back while you would only be a few years older, perhaps millions of years would have passed here on earth.

Messed up but true.

Helix

Hellrazer wrote: »

Light speed is supposedly constant--yes?? And that speed cannot be broken?

cant remember where i read it, but isnt it considered that the constants we take as constants arent actually constants, and some have been proven to have changed in the last few billion years

not sure if the speed of light is one of them, ill try to remember which of my books its in

Gurgle

Helix wrote: »

cant remember where i read it, but isnt it considered that the constants we take as constants arent actually constants, and some have been proven to have changed in the last few billion years

Its more semantics than anything else - light speed is constant because a meter is defined as the distance light travels through a vacuum in 1 / 299,792,458 seconds.

Light speed doesn't change as our universe (or localized big bang debris field) expands, the speed of time doesn't change as that would make the maths ridiculous so the meter is what changes.

Turtwig

Gurgle wrote: »

Its more semantics than anything else - light speed is constant because a meter is defined as the distance light travels through a vacuum in 1 / 299,792,458 seconds.

Light speed doesn't change as our universe (or localized big bang debris field) expands, the speed of time doesn't change as that would make the maths ridiculous so the meter is what changes.

Actually it isn't just semantics..

Linky,

Note : Not for the Layman, unless they're brave:P

20goto10

It is possible to see into the past. Light from distant stars takes so long to reach the earth that what we are seeing occured millions and billions of years ago. There is also a theory that suggests that the universe is donut shaped (I've no link, just google it), meaning that light eventually travels back around on itself. What this means, if proven, is that one of those stars out there is actually light from our sun from billions of years ago. In theory, we could one day have telescopic images of prehistoric earth in much the same way as we have images of the early universe.

It's quite easy to think well if we can see into the past then why can we not just travel to where the light is coming from? The problem is the past doesn't physically exist anymore. It's changed and all thats left is its photons whizzing around the universe.

It's still pretty cool to be able to see into the past though.

JoeB-

I don't think subjective time slows down at when you're travelling at the speed of light, or close to the speed of light.
The idea that when travelling at the speed of light you arrive anywhere instantly is just wrong...

Subjective time never changes... so everything will feel the same to you regardless of the speed you're travelling at.. this is the whole point, there is no way to determine the speed at which you're travelling, i.e if you're on a train, are you moving or is the Earth moving past you?, both viewpoints are correct.

So travelling at 99.9999% the speed of light, everything seems normal to you... you breathe normally, and age normally... it's when you stop and look around that you see many years have passed for those not speeding around.

Light takes eight minutes to get from the sun.. so if you travelled to the sn and back at 99.999999 % the speed of light it would take 16 minutes or thereabouts.. however 20 days or more may have passed on Earth.


Even if travelling at 99.9999999 % the speed of light certain parts of the universe would be too far away to reach.. this is why light from the earliest stages of the universe is still travelling towards us, it hasn't had a chance to get here yet.


Time travel may be physically possible, however the chances of humans ever doing it seem slim.

Some particles in accelerators have lived up to 2,000 times longer than they normally would.. this is when they are travelling so fast that in a second, where light has travelled 300,000km, the particle would only be behind the light wave by a few meters.. so that's very very fast.

komodosp

Light takes eight minutes to get from the sun.. so if you travelled to the sn and back at 99.999999 % the speed of light it would take 16 minutes or thereabouts.. however 20 days or more may have passed on Earth.

No that's the wrong way around. If you went to the sun and back it would feel instantaneous to you, but to everyone on Earth, 16 minutes would have passed.

Here's a question though:

Time travels fast for someone standing still but slowly for someone moving fast. BUT. Speed is all relative isn't it? So how does "the universe" know that it is not the person on Earth moving fast and the person on the spaceship moving slow? i.e. that it should be the person on Earth aging slowly and the person in the spaceship aging normally?

maninasia

Time is relative and the perception of time depends on the observer, in the above case both of the observers are right at the same time.
Einstein realised this and this allowed him to develop his theory of relativity.

The universe does not have a conception of time, humans have a conception of time as a by-product of entropy, or the trend to disorder. If entropy was reversed we would also have a sense of 'time', but this time would be running backwards. We would think this is perfectly normal also if we were born into this universe.

To give an idea of time being a human construct what if we were an artificial intelligent entitry capable of copying ourselves infinitely in any medium, where does time begin and time stop? What if we were capable of creating new universes, what is time then?

Azelfafage

Amalgam wrote: »

Is it true astronauts on the space shuttle lose or gain a tiny tiny amount of 'time', relative to people on Earth?

It certainly is true.

The Apollo astronauts are owed 300 microseconds overtime by NASA for 40 years now.

See:

http://www.time.com/time/magazine/article/0,9171,839785,00.html


.

aDeener

Delorean?