48 replies to this topic

[jjf3]

I think volunteers for missions will never be a problem. There will always be people willing to try almost anything.
Think how much easier it would be to put a man on mars if it was a one way mission. So much less fuel and equipment to take with you.
I'm sure you could find thousands of volunteers who would be willing to go even knowing certain death, for the incredible fame and legacy you would leave behind.

When people talk about time travel I always point them towards the direction of Arthur C. Clarke. In the year 2000 he published and released a book by the name of "The Light of Other Days." In this book it takes you through a journey of future Earth among the discovery and mass production of so-called time viewers. Now this I believe, it is a better vision for Time Travel without risk.

Future humanity may not want to risk going through actual physical time travel yes even with robots or holograms because these things could still disrupt space-time. So why not invent a brand new multi media device for viewing the past and the future. What could possibly come next after Holodeck type inventions??? I picture entire rooms could be dedicated to certain areas of the past and people will learn by watching what really happened. As the technology progresses, using augmented reality they could insert a likeness of themselves inside what I like to call history rooms and walk around without anybody knowing. They really aren't there and really aren't interrupting space-time. This will also greatly enhance our intelligence and fill in all the questions we ever had about the past. Using 3D printers we can plug in dimensions of lost historic and priceless artifacts and recreate them in museums.

We may figure out how to physically time travel, but may mark it illegal to do so because of the risk.

This also may explain why there is no record of any time travellers coming from the future.

[Keitaro2011]

I think time-travel into the past is a field well worth exploring! I prefer to be optimistic about the possibility of time-travel! Just listening to Michio Kaku talk about it is thrilling!

I think if time travel into the past were possible, then you could use time traveling nanobots to go back and scan the brains of people before their death, and bring them back to life in the future! You could use it to recover information and all sorts of other applications!

[Caiman]

Some interesting thoughts, jj. Talking of authors, have you read the story by Phillip K Dick called Paycheck? It's an interesting analysis of the consequences that could still occur if we created a device that allowed us to see, but not interact, with our future. It was adapted into a film a few years back which maintained the overarching storyline but transplanted it into a setting a little closer to 'the real world'. Not a great film, but it had some interesting scenes showing how the device became a type of 'self fulfilling prophecy', giving knowledge of future events which in turn lead to people taking the action which would cause them, in trying to change the future. In a sense though, being able to view the future means you are allowing information to travel back in time, so it's still [indirect] interaction with the past, from the POV of the timeline which is being viewed.

[Chronomaster]

I don't believe in the 'many worlds' interpretation of quantum physics, I struggle to come to terms with the concept of entire universes branching into existence because a different decision was made (just where would all the matter and energy to create a whole universe every nanosecond come from anyway?) therefore I think that there is only one 'timeline' as it were, that lays behind or infront of us and in that interpretation, time travel to the past simply cannot exist due to paradoxes. Time travel to the future via relativity is safe, I suppose- but no method which allows travel back from the future such as a wormhole.

[Shimmy]

I don't believe in the 'many worlds' interpretation of quantum physics, I struggle to come to terms with the concept of entire universes branching into existence because a different decision was made (just where would all the matter and energy to create a whole universe every nanosecond come from anyway?) therefore I think that there is only one 'timeline' as it were, that lays behind or infront of us and in that interpretation, time travel to the past simply cannot exist due to paradoxes. Time travel to the future via relativity is safe, I suppose- but no method which allows travel back from the future such as a wormhole.

The laws of physics only exist and need to be followed within our universe as far as we know. There's no reason why the concept of matter having to come from somewhere has to be true outside of our universal laws. If a new universe is created the matter is not being created in our universe, its sort of just been split, and within each individual universe no new matter has been made. The fact that the big bang happened at all could be thought of as supporting this view perhaps, and that the energy conservation law was brought into existence with the universe itself.

[Caiman]

Further to the above, from a comprehensive FAQ on Many Worlds;

Q22 Does many-worlds violate conservation of energy?
First, the law conservation of energy is based on observations within each world. All observations within each world are consistent with conservation of energy, therefore energy is conserved.

Second, and more precisely, conservation of energy, in QM, is formulated in terms of weighted averages or expectation values. Conservation of energy is expressed by saying that the time derivative of the expected energy of a closed system vanishes. This statement can be scaled up to include the whole universe. Each world has an approximate energy, but the energy of the total wavefunction, or any subset of, involves summing over each world, weighted with its probability measure. This weighted sum is a constant. So energy is conserved within each world and also across the totality of worlds.

One way of viewing this result - that observed conserved quantities are conserved across the totality of worlds - is to note that new worlds are not created by the action of the wave equation, rather existing worlds are split into successively "thinner" and "thinner" slices, if we view the probability densities as "thickness".

Many worlds doesn't sit well with me either, the concept that at any given moment, countless number of universes are splitting out from our own, then branching out from those which split, and so on ad infinitum, but it would certainly help explain away a lot of the paradoxes in quantum theory, and indeed remove any problems of paradox in time travel to the past.

[Caiman]

Time travel refuted by light speed results

http://www.bbc.co.uk...onment-14289114

Physicists have confirmed the ultimate speed limit for the packets of light called photons - making time travel even less likely than thought.

The speed of light in vacuum is the Universe's ultimate speed limit, but experiments in recent years suggested that single photons might beat it.

If they could, theory allows for the prospect of time travel.

Now, a paper in Physical Review Letters shows that individual photons too are limited to the vacuum speed limit.

That means that photons maintain the principle of causality laid out in Einstein's theory of special relativity - that is, an event's effect cannot precede its cause by traveling faster than light. It is violation of this causality that would, in principle, permit time travel.

While the limit in vacuum is a fixed number - some 300,000km per second - the speed of light can vary widely in different materials.

These differences explain everything from why a straw looks bent in a glass of water to experiments in cold gases of atoms in which light's speed is actively manipulated.

Some of those experiments showed "superluminal" behaviour, in which photons travelled faster than the speed of light in a given medium.

It remained, however, to determine whether or not individual photons could exceed the vacuum limit.

All relative

Now, Shengwang Du and colleagues at the Hong Kong University of Science and Technology have measured what is known as an optical precursor.

Like the wind that moves ahead of a speeding train, optical precursors are the waves that precede photons in a material; before now, such optical precursors have never been directly observed for single photons.

By passing pairs of photons through a vapour of atoms held at just 100 millionths of a degree above absolute zero - the Universe's ultimate low-temperature limit - the team showed that the optical precursor and the photon that caused it are indeed limited to the vacuum speed of light.

"By showing that single photons cannot travel faster than the speed of light, our results bring a closure to the debate on the true speed of information carried by a single photon," said Professor Du.

Thus, photons cannot time travel, and moving information around at faster-than-light speeds is impossible.

But the work has more prosaic implications.

"Our findings will also likely have potential applications by giving scientists a better picture on the transmission of quantum information," said Professor Du.

Time travel by other means, however, is not entirely ruled out.

Einstein's theory of general relativity, in which space and time are two intertwined aspects of the same medium, would permit the bending of the medium to join two different times - a situation popularised as creating a "wormhole".

[Roh234]

I guess the best way is to stay near high mass objects for 2x time dialation. For anything faster I'd suggesting englaring quantam foam buts that's also dangerous. Maybe we can find a way to make sure 1kg of payload > 1 kg of fuel and that way we can use time dialation traveling at reletavistic speeds could be possible. I would think atleast 5000 years from now.

[Robert Riness]

i think you guys are missing one key of the problem of time travel..


your using light speed as a constant. it is not a constant, it is effected by gravity. it can bend it, slow it down either way we are inside a gravity well and our current understanding of the speed of light is only part of a larger variable. we do not have the maximum speed of light measured yet because we have never been outside our sun's gravity well. we have the earths and the moon and our sun's gravity effecting light. our measurement is not the top end.


sadly this is a major problem for those of us who would like to visit other stars. because if the speed of light outside of gravity is faster than it is here than in between stars is backwards time. so light and matter in between stars actually travels backwards in time. which by conventional means we could never get to another star before it vanishes before our eyes.

folding space may save the day getting between star systems but a new way to measure space and distance will have to be made. if backwards time in between star systems then that says there is no distance. it seems the universe is actually a solid and not spread out that much.

but the whole idea of time travel can be seen right in front of us. and it seems its a natural occurrence. more gravity = faster into the future you go, no gravity you go backwards.

changing your position on the light speed frame reference changes progression of time. so just by being where light moves slower than light moves here you would be skipping day's month or years here. then if you want to go backwards you step outside of gravity all together to move backwards. my personal guess is that backwards movement goes a whole lot faster than forward movement at least from the observer's view of time during the movement.

time travel, its natural. if you got the money for a ship i can build it, we can go.. any questions....?

[Craven]

Well, to put it simply - you are wrong. Speed of light is constant. A very important one.
You're mixing impact of gravity on photons with constant speed of light in vacuum.

[Robert Riness]

which is why they are having to redo that experiment. but there are other facts that we have been collecting data on for years. oddly those craft we sent out how many years ago have broke the outer bands and are speeding up drastically as they go farther out. it makes for some interesting reading if you find the info on it.

but the data suggest that the frame reference of the speed of light is not fully measured. plus there is a large amount of astronomical questions this would solve.

i'm fully aware the implication this causes current understanding. myself i made the observation back around 03'. I've conducted a few experiments of my own, what i'm finding is 3 to 4 levels of speed of light increases between star system gravity / galaxy gravity / interstellar gravity / i'm not going to rule out an increase beyond that level. anything is possible, this i find to be true.


remember that current understandings of time are measured with light. being the case with non constant light speed across the universe allows for the illumination of it. the gravity wells are the only areas that reflection of and source of light exist. so with all the pictures stars and galaxies far away this explains what we are seeing and why we can see it at all.

[Craven]

I know of no "other facts" nor "data collected over years". There's no drastical change of speed in far away spacecraft. There are tiny, changes (like slowing of Pioneer) that don't yet have universal explanation. Believing that this even remotely suggests craziness you posted about inverting time outside of solar system, or "more gravity = faster into the future you go, no gravity you go backwards" is... well... plain crazy. It's neat example of really, really bad, BAAAddd astronomy.

[h.g.Whiz]

Well, to put it simply - you are wrong. Speed of light is constant. A very important one.
You're mixing impact of gravity on photons with constant speed of light in vacuum.

What about the speed of darkness?

[GNR Rvolution]

I would welcome seeing some evidence for this but I've certainly never heard of any empirical evidence that disproves the speed of light as being THE constant frame of reference around which much of modern physics (excluding quantum) is based.

[Craven]

At same time I'm sure you've heard plentiful of evidence that supports speed of light being constant

[Caiman]

your using light speed as a constant. it is not a constant, it is effected by gravity.

Actually, c is the constant. It's referred to as light speed though since, in a complete vacuum and where gravity is so negligible it can be ruled out, light travels at that speed. (In fact though, light is always travelling at c really, but if stuff gets in its way it can take longer to travel between two points, watch this: http://www.newscient...n-in-glass.html)

because if the speed of light outside of gravity is faster than it is here than in between stars is backwards time

Gravity has infinite reach, it is also present between stars.

which by conventional means we could never get to another star before it vanishes before our eyes.

Stars have lifetimes measured in billions of years. We could certainly get to one using conventional means, even if it took a hundred thousand years.

[Robert Riness]

i've never found any evidence that supports speed of light being constant. nothing we view in this universe says that there is any constant at all. that's kinda like saying the earth is flat. if your head is stuck inside the box your not being a very good observer.

as far as our area - pretty much the entire solar system light is constant. this we have been able to test, out side tho is a whole different matter.

i do admit that no one ever looks at the data for what it is. it seems everyone has an agenda they are trying to prove or disprove which blinds them to what they are looking at. some are actually scared to report what they find to be true or religious concerns. the NASA report about voyager released back around 03 04 talked about voyager speeding up to incomprehensible speed. now i don't know how fast that is i comprehend sound and light speed just fine so what they wrote i can't tell you. but the fact that it is speeding up at all gives credence to this theory. since you don't agree with it, it's up to you to disprove it. myself i try to keep my mind open because just as soon as anyone says this is a fact it is soon proven not to be the case.

btw if correct which i do believe it is, this doesn't effect what we know of inside our solar system, it only effects our knowledge beyond our gravity well, which is questionable anyway. i for one do not buy into this big bang theory. it sounds great and would be an interesting universe, but its not ours.

[Robert Riness]

wait a sec a vacuum has nothing to do with gravity. a vacuum means that matter is vacant. it has zero to do with gravity or light. vacuum only has an effect on matter.

gravity and light transverse regardless of a vacuum.

[Unrequited Lust]

i've never found any evidence that supports speed of light being constant. nothing we view in this universe says that there is any constant at all. that's kinda like saying the earth is flat. if your head is stuck inside the box your not being a very good observer.

as far as our area - pretty much the entire solar system light is constant. this we have been able to test, out side tho is a whole different matter.

i do admit that no one ever looks at the data for what it is. it seems everyone has an agenda they are trying to prove or disprove which blinds them to what they are looking at. some are actually scared to report what they find to be true or religious concerns. the NASA report about voyager released back around 03 04 talked about voyager speeding up to incomprehensible speed. now i don't know how fast that is i comprehend sound and light speed just fine so what they wrote i can't tell you. but the fact that it is speeding up at all gives credence to this theory. since you don't agree with it, it's up to you to disprove it. myself i try to keep my mind open because just as soon as anyone says this is a fact it is soon proven not to be the case.

btw if correct which i do believe it is, this doesn't effect what we know of inside our solar system, it only effects our knowledge beyond our gravity well, which is questionable anyway. i for one do not buy into this big bang theory. it sounds great and would be an interesting universe, but its not ours.

The constancy of the speed of light does not refer to its constant speed through any medium. For example, the speed of light is much slower in water than through air, evidenced by the weird distortions of something poking out of the water. This is called refraction and can be illustrated by this:



Rather the when physicists say the speed of light is constant, they really mean constant regardless of the frame of reference. For example, if you were driving at 50 mph and a car parallel to you passed traveling at 80 mph, their relative speed to you would be 30 mph (80 - 50). Similarly, the speed of your car is measured to be zero. However, light does not work this way. You can be traveling at 99% the speed of light, but the speed of light remains the same (as opposed to 1% the speed of light; 100%-99%). Meaning even if you are traveling at 99% the speed of light, your measurement would the same as someone who is at rest.

This has all sorts of weird implications called Lorentz transformations. The constancy of the speed of light is one of the two postulates of special relativity, a theory so rigorously tested after Einstein proposed it that physicists soon regarded it as fact. Relativity is routinely used when experiments contain phenomena that either goes as fast as light or close to the speed of light. Otherwise we use Newtonian mechanics, which provide approximations so close that they can be treated as exact.

The other postulate of special relativity says that laws of physics are the same in any inertial frame of reference. So your assertion that the laws of physics are different outside the solar system is crazy and absurd. I don't know how you can even begin to think such a thing unless you're really into woo and conspiracy theories.

[Caiman]

wait a sec a vacuum has nothing to do with gravity. a vacuum means that matter is vacant. it has zero to do with gravity or light.

Huh? Of course it has to do with it. Light that is travelling through non-vacuum is affected by the matter within it. Did you watch the video I posted? C itself is defined as the speed of light in a vacuum.