Hawking Says Time Travel Possible

[QwertyJuan]

The difference between his definition and yours is that his is right.

"Traveling" has precisely nothing to do with the ability to return to your starting point.

Then what IS the point? I travel into the future, but then what happens? I turn around and come back?? Whoopeee!!

If I want to time travel I will just cross the International Date Line backwards, thank you very much.

 

[HOCP4ME]

WRT the many worlds interpretation: suppose you have a system who has only two eigenvalues (possible outcomes of a measurement). For the sake of argument, let's say you're measuring the spin of an electron. Its projection along the z-axis can only have two possible values, +/- a constant. If you measure +constant, is there a universe in which an observer measured -constant? In essence, it ascribes a physical reality to all possible outcomes of a measurement.

I remember reading something about this. The EPR experiments, which creatively compared the results of electron spin measurements to prove - experimentally, and beyond doubt - that the observation of one electron can instantly (faster than light) affect the state of another electron miles away. I was absolutely amazed by this result, as it gave experimental proof to an idea that seems inherently unprovable at first glance. How do you begin to understand a system that collapses after you measure it? John Bell figured out how.

 

[mtasquared]

what if you make a long rod 200k miles in length. if it were perfectly stiff and you rotated(twisted) it, wouldn't that transmit information faster than the speed of light? just wondering.

 

[QwertyJuan]

what if you make a long rod 200k miles in length. if it were perfectly stiff and you rotated(twisted) it, wouldn't that transmit information faster than the speed of light? just wondering.

Ohhh! That's news!!

 

[Parmenides]

suppose you have a system who has only two eigenvalues (possible outcomes of a measurement). For the sake of argument, let's say you're measuring the spin of an electron. Its projection along the z-axis can only have two possible values, +/- a constant. If you measure +constant, is there a universe in which an observer measured -constant? In essence, it ascribes a physical reality to all possible outcomes of a measurement.

I'm not sure I follow

 

[BBA]

Hawkings is right...I am living proof, I travel forward through time every day...in fact I just went 10 seconds writing this sentence.

 

[okashira]

This is all only based off of Einstiens theory that if you travel at or faster than the speed of light you can travel through time. There isn't any actual evidence that this is true.

I normally stay out of these, but I can't help myself here. Please, I hope you are not serious. I didn't have time to read the replys but I hope someone has already pointed out there is A LOT of evidence this is true. I have a question. What is the difference between ignorance and stupidity? Stupidity is going around debating and making sweeping statements about something you're ignorant about.

We're all guilty of both. The difference is - what's your ratio of the latter to the former?

 

[okashira]

what if you make a long rod 200k miles in length. if it were perfectly stiff and you rotated(twisted) it, wouldn't that transmit information faster than the speed of light? just wondering.

Freudian?

In this case, the answer would be the that Freud does not acknowledge that a material which is so stiff cannot and does not exist.

In fact, the rate at which such information would be transmitted would be approximately equal to he speed of sound in that material, which is absurdly below the speed of light in any material...

 

[The Doctor]

say you build a ferris wheel the size of the planet that can make 8 revolutions a second. its possible yes? granted the enursha would kill you probably. that could travel faster then light!

Dude are you on drugs?

 

[Quoll]

Every time his name is mentioned I think of Family Guy

I think of Ricky Gervais

http://www.youtube.com/watch?v=6ktBQ51iGWw

 

[Shadow2531]

It was explained to me once that the speed you travel through space + the speed you travel through time is always equal to the speed of light (relative to your own galaxy). Therefore, the faster you move through space, the slower you must move through time.

But, as others have said, if you travel so fast for so long (to show a *significant* slowdown in time), you're going to be so far away that those at the starting point won't be able to observe you until you get back (or a tad before you get back depending on how you can send a signal). But, then, did time really slow down for you, or did those at the starting point just have to wait a very long time for you to come back into observation distance? I guess it'd be neat to observe constant light signals from the starting point, craft and end point at an equal distance from the starting point and end point in another galaxy. But, none of that makes sense, so just thinking retardedly.

For traveling back in time, if it were possible, I think that if you go back and kill yourself, the only thing that would happen is that you'd create an alternate time line. The time line where you were not killed would still exist. And, as for "create" in "create an alternate time line", you wouldn't actually "create" a new time line. It'd already exist. You'd just be able to observe it then.

Relative observation boggles the mind.

 

[HOCP4ME]

I'm not sure I follow

Let's say an electron's spin has two possible states - clockwise, and counter-clockwise, we'll call them. It's been experimentally proven (see EPR experiments) that the electron doesn't "choose" a state until you actually measure it. So you measure it, and it turns out to be spinning clockwise. Does there exist another universe in which you measured it, and it turned out to be spinning counter-clockwise?

You might say hell no, it was always spinning clockwise; you just didn't know that until you measured it. But experiments have shown that not to be the case.

At least I think that's what he's saying.

Hawkings is right...I am living proof, I travel forward through time every day...in fact I just went 10 seconds writing this sentence.

One of the questions on the application for a residential college here at the University of Virginia was the following:

"You discover that you can create a time machine by putting change into a jar of liquid drain cleaner. When you sit next to it, you travel into the future very slowly. How will you be able to tell?"

 

[Imaulle]

Dude are you on drugs?

always.

 

[HOCP4ME]

Relative observation boggles the mind.

One thing I don't quite understand about relativity is the feeling of inertia. If you passing your neighbor and your neighbor passing you really are the exact same event, why is it that in the first case you feel the acceleration and deceleration of the motion, whereas in the second case you feel nothing?

I recall some discussion of Mach and Einstein solving this problem but I've never heard an explanation that I fully understand.

 

[Sly]

What about those ~100 atomic clocks carried by GPS satellites that lose time precisely as predicted by relativity?

I love when people who clearly know jack-shit beyond their grade-12 physics try to correct someone who is far more brilliant then they could ever hope to be.

Curiously, how do they get synced? The only way i could think of to sync to clocks exactly without needing to compensate for latency is to put them next to each other. You can't exactly do that in space.

 

[Powerage]

Curiously, how do they get synced? The only way i could think of to sync to clocks exactly without needing to compensate for latency is to put them next to each other. You can't exactly do that in space.

Relativistic equations are programmed into them prior to putting them in space that calculates proper time (in our frame) based off where they'll be orbiting the earth. I'm pretty sure anyways.

 

[NKD]

I can see space-time travel as potentially being possible, but flat out time travel, nope, ain't happening.

very true, if you travel in space so fast ofcourse 100 years could pass on earth when you return and for you it felt passed by a lot slower. I honestly don't blieve that there is future you can travel too, unless ofcourse you are talking about parallel universe or even if they exist. Then you get too deep in to this space stuff.

 

[Hornet]

Why are you guys being so hard on Mr.Hawking? The new show on Discovery Channel is pretty good, and it gets people thinking and talking about this stuff. He won't be around forever and we'll need a new generation of physicists to solve these problems. A good start would be getting the masses interested in this and a little educated about it, which is what the TV show does.

+1

I'm no expert in physics, my mathematics are never good But I really love reading about all this extreme physics stuff in laymen terms, and we owe them to the great minds like Einstein who discover these stuff.

I hope there will be a young generation of brilliant minds to continue these works. (including proving string theory, or finding a theory of everything )

 

[keenan]

Curiously, how do they get synced? The only way i could think of to sync to clocks exactly without needing to compensate for latency is to put them next to each other. You can't exactly do that in space.

It's compensated for, and quite complicated. A GPS receiver needs to have a full almanac, giving it an accurate position for each of the satellites in the constellation and what orbit they are in. With that information they can apply some fancy maths to model the relativistic and environmental effects and compensate for them. I believe that the one-way time transfer of GPS is more precise than the clocks onboard the satellites themselves, given ideal receiving conditions and an accurate receiver. See: http://tf.nist.gov/time/oneway.htm

On a long-term basis, the USNO is responsible for the constellation, and they monitor it from ground stations and upload periodic correction commands to the satellites to keep them in sync with each and with UTC. They also publish correction data for all satellites, which can be used to post-process GPS information received in the field and considerably improve positioning accuracy where real-time results aren't needed, such as surveying.

GPS is also commonly used to 'transfer' time between two ground stations, and using it in this fashion, the accuracy of the time transferred can be better than the GPS clocks themselves. This method is used to keep global UTC in sync with standards labs around the world, and I believe UTC is defined as some kind of weighted average of the participating global standards.

 

[Matthew1034]

A particle existing at the speed of light could travel through time as we travel through space. The problem is and always has been that anything with mass cannot reach the speed of light, so for a thing with mass to travel c it would have to essentially de-materialize into pure energy and re-materialize once it reached the point in time it wanted to be.

 

[mavalpha]

There may not be a "cosmic speed limit" as we currently believe. I think it's critical to spend the resources to find the answers if we ever hope to survive this rock we're on.

My feeling has always been that the underlying math behind the "cosmic speed limit" was fundamentally flawed. If I make the initial assumption that 1+1=3, then I can go through a very complex proof that eventually proves that 1+1 does actually equal three. While there will be a flaw somewhere in that proof, the only way I will find it is by ultimately realizing that my initial assumption was wrong. Similarly, I think Einstein's calculations were based on an unformulated presumption that there wasn't any particle in the universe whose velocity exceeded c (ie a tachyon). If we counter this with an assumption that such a particle does actually exist, its very existence means that the arbitrary limit c is exactly that- arbitrary. The problem is that because of our causal view of the universe, we'd never be able to build a machine that accurately measures tachyons- and even assuming one ever showed up, we wouldn't know what to make of it. So until a tachyon stumbles across someone's detector and announces itself as a tachyon, people will keep treating c as an absolute ceiling and tachyons as nothing more than an exercise in conceptual physics.

 

[westrock2000]

what if you make a long rod 200k miles in length. if it were perfectly stiff and you rotated(twisted) it, wouldn't that transmit information faster than the speed of light? just wondering.

I'm just going to take a guess at this. When you move a solid object, the individual atoms transmit an electrical field to adjacent atoms that then follow. Imagine something like a train pulling out of the station. The engine starts moving and as each link between the cars tightens up the entire train begins to move. However with in a solid object this all happens at the speed electrical conductivity, which would be very nearly the speed of light. Thus to our intepretation it seems instantanous.

So if you had a 200K mile long rod and rotated it, ignoring torque and friction and fatigue of the material what you would probably see is a wave running length wise of the rod as it "rotates".

Kind of like the tires of a Top Fuel car deforming as the wheel suddenly is spinning at you know 100MPH and the outside of the tire is sitting stationary on the skid. The tire twists as the material plays catch up with itself.
http://www.youtube.com/watch?v=wL_6dDCCHlg

Carl Sagan (God rest his soul) in of the Cosmos episodes described the "twins paradox" where 1 twin stays on the Earth and the other travels to middle of the galaxy and back and we he comes back humans are long gone, but for him it was only like 30 years.

Issac Assimov in his (awsome) book Extraterrestial Civilizations, stated that while the idea of FTL is "nice" because it gives us the ability to go and come back again, that desire is more of that a human living on Earth. If you take mankinds history as a whole you would find that it probably would not be that important in the long run of space travellers. Consider that people from Europe originated in Africa and people here in America originated from Europe, yet many of us have no desire to ever go to Europe, like wise many Europeans have no desire to go back to Africa. While the intial space travellers may dream of returning to Earth, your first generation and beyond space travellers will have no idea what Earth is like and therefore they will view travelling through space as being normal. Sure the high mountains of the Swiss Alps sounds awsome, but I live in the flat plains of Texas with no problems.

"The universe is not required to be in perfect harmony with human ambition" -Carl Sagan

 

[Shadow2531]

tachyon

I always wondered what would happen if you could emit an inverse tachyon beam towards the same point in 3 different time periods.

 

[westrock2000]

My feeling has always been that the underlying math behind the "cosmic speed limit" was fundamentally flawed.

I think the argument from a fundamental standpoint just sounds very "human".

When we first discovered external transportation, our only reference was biological propulsion. The "leg". We used animals to pull our vehicles. The horse became the standard. There were animals that were faster then a horse, but they lacked the thrust a horse could generate and thus couldn't propel usefull weights. Likewise there were animals that could generate more thrust then a horse, but they did not have the high RPM of the legs so they were slower.

Sure we could push a horse harder, but it had negative physical effects and becomes unstable as you surpass the natural limits of the leg. So in order to go faster then the horse, we had to replace the horse itself. Eventually technology prevailed and we created the engine. It could generate more thrust and could operate at a higher RPM. Thus we surpassed the speed of biology.

Next we took to the skies. The propeller was used intially. This worked by displacing air. So then we ran into the next limit. How can you go faster then air when the air doesn't want to move any faster. There were some examples of prop based planes that tried to surpass the speed of sound. But again we ran into the same problems. It took way too much energy to do it and you ran into big stability issues.

So we replaced the prop. And moved to emission propulsion, the rocket. Chemicals or energy are emitted and pushes the transport. Finally we beat the speed of sound.

So now we have again arrived at the same fork in the road. Emission is currently our best known method, and the fastest thing we know of that is emitted is light. So how to we go faster then light? Again it takes alot of energy to beat it using the same method and again we run into weird anamolies if we were to do it.

So again we must create a new method of propulsion. And just like the reciprocating engine was unknown to early man on horseback and the jet engine was unknown to early pioneers of flight, the next method is currently unknown to us.

 

[Monkey God]

Can I just say, "No kidding?!?!"
Just because Hawkings made the big news (and good for him - much much better then Oprah! ) . . But, Now anything he says is new and ground braking to the backward news ORGs?? Are they that clueless, did they fire ALL of there science reporters??
WTF! This is OLD OLD OLD hat . . time dilation is not new, quite understood, tested (at least in a small scale - but quite consistent with theory), and even used in day to day life (GPS etc).

The OMGs!! this is new is just lame to anyone with 1/2 a clue. And I think the manor reporting does Hawkings a disservice.

+1
Seriously.

 

[spintroniX]

Actually, what I was saying WRT many worlds interpretation is too pop-sci esque. You should browse the web for more concrete information so I don't muddy your mind on the issue.

Again, you need to be careful with your language in regards to the EPR thought experiment. If you have two entangled particles, for simplicity let's assume you're dealing with a two state system and you measure one you certainly know the state of the other particle. So what? This information isn't usable and you can't use it to do anything practical. You have no way of influencing which eigenvalue you will measure - you simply get one of them at random and then you know the state of the other particle.

What Bell showed was that there are no hidden variable theories that are consistent with quantum mechanics. IN other words, quantum mechanics TRULY is random. It's not that the case that the particle was always in a spin up or spin down state. Until you perform the measurement, it is in a superposition of states and at that moment it "chooses" its state. We invoke the notion of wave function collapse because all repeated experiments of this observable will yield the same answer (provided your observable wasn't a linear combination of energy eigenstates)

 

[spintroniX]

Similarly, I think Einstein's calculations were based on an unformulated presumption that there wasn't any particle in the universe whose velocity exceeded c (ie a tachyon).

No, that's not how it worked. The fact that c is a fundamental speed limit is a consequence of the theory of special relativity, not the assumption. What Einstein (correctly) deduced is that all inertial observers will experience the same laws of physics. As a result, we have to measure the same values of the fundamental physical constants, such as the electron mass, charge, and of course the speed of light among other things.

This result has been confirmed by every experiment that has tested it. It's a fact.

 

[Parmenides]

Actually, what I was saying WRT many worlds interpretation is too pop-sci esque. You should browse the web for more concrete information so I don't muddy your mind on the issue.

Again, you need to be careful with your language in regards to the EPR thought experiment. If you have two entangled particles, for simplicity let's assume you're dealing with a two state system and you measure one you certainly know the state of the other particle. So what? This information isn't usable and you can't use it to do anything practical. You have no way of influencing which eigenvalue you will measure - you simply get one of them at random and then you know the state of the other particle.

What Bell showed was that there are no hidden variable theories that are consistent with quantum mechanics. IN other words, quantum mechanics TRULY is random. It's not that the case that the particle was always in a spin up or spin down state. Until you perform the measurement, it is in a superposition of states and at that moment it "chooses" its state. We invoke the notion of wave function collapse because all repeated experiments of this observable will yield the same answer (provided your observable wasn't a linear combination of energy eigenstates)

So, you would say that the crux of the matter is that we can't explain how sometimes observation entails one result as opposed to another?

No, that's not how it worked. The fact that c is a fundamental speed limit is a consequence of the theory of special relativity, not the assumption. What Einstein (correctly) deduced is that all inertial observers will experience the same laws of physics. As a result, we have to measure the same values of the fundamental physical constants, such as the electron mass, charge, and of course the speed of light among other things.

This result has been confirmed by every experiment that has tested it. It's a fact.

Curious, and I'm still muddy on this, but we have not observed the speed of light from the center of our galaxy, or from another galaxy for example. All our observations are on or close to earth or that which earth has received from afar. Not to suggest that the laws of physics could be different elsewhere, but in areas of different mass would it be possible to find different values for the speed if observation were from another area in the galaxy?

 

[Nemesis999]

Curious, and I'm still muddy on this, but we have not observed the speed of light from the center of our galaxy, or from another galaxy for example. All our observations are on or close to earth or that which earth has received from afar. Not to suggest that the laws of physics could be different elsewhere, but in areas of different mass would it be possible to find different values for the speed if observation were from another area in the galaxy?

The Gravitational Lensing predictions of general relativity seem to hold up everywhere.

The amount of curvature of light around a massive body is calculated from its speed. If the speed of light were different elsewhere our observations of light reaching Earth would cause general relativity to fail.

 

[Krenum]

This is pretty interesting.

'When we accelerate tiny particles to 99.99 per cent of the sped of light in the Large Hadron Collider at Cern in Geneva, the time they experience passes at one-seventhousandth of the rate it does for us.
'If we could build a spaceship that was fast enough, then it could reach other stars in the lifetime of the crew, but maybe 2.5million years would have passed by on earth.'


It makes sense.

The only way we could have a propulsion system fast enough made out of the technology we currently have would be to make an engine that could withstand controlled nuclear explosions to propel us through the universe. Or something that uses a magnetic field or gravitational pull.

But then you would have to build a spaceship that shielded the crew from space radiation. Also the spaceship would have to have gravity otherwise such a long trip would make the crews muscles deteriorate because in weightlessness there is no resistance.

lots of limiting factors, but the idea of space travel is interesting.

 

[okashira]

It's compensated for, and quite complicated. A GPS receiver needs to have a full almanac, giving it an accurate position for each of the satellites in the constellation and what orbit they are in. With that information they can apply some fancy maths to model the relativistic and environmental effects and compensate for them. I believe that the one-way time transfer of GPS is more precise than the clocks onboard the satellites themselves, given ideal receiving conditions and an accurate receiver. See: http://tf.nist.gov/time/oneway.htm

On a long-term basis, the USNO is responsible for the constellation, and they monitor it from ground stations and upload periodic correction commands to the satellites to keep them in sync with each and with UTC. They also publish correction data for all satellites, which can be used to post-process GPS information received in the field and considerably improve positioning accuracy where real-time results aren't needed, such as surveying.

GPS is also commonly used to 'transfer' time between two ground stations, and using it in this fashion, the accuracy of the time transferred can be better than the GPS clocks themselves. This method is used to keep global UTC in sync with standards labs around the world, and I believe UTC is defined as some kind of weighted average of the participating global standards.

I think you are answering a different question, that's how your local GPS receiver is calibrated. It's constantly updated time of its quartz clock based on the satellite times.
I don't know if the satellites themselves are even calibrated at all after being put in service, they ARE the source of the calibration. I believe they are actually atomic clocks in each of the GPS satellites. Someone more knowledgable correct me if I am wrong (that may be yourself )

I'm just going to take a guess at this. When you move a solid object, the individual atoms transmit an electrical field to adjacent atoms that then follow. Imagine something like a train pulling out of the station. The engine starts moving and as each link between the cars tightens up the entire train begins to move. However with in a solid object this all happens at the speed electrical conductivity, which would be very nearly the speed of light. Thus to our intepretation it seems instantanous.

So if you had a 200K mile long rod and rotated it, ignoring torque and friction and fatigue of the material what you would probably see is a wave running length wise of the rod as it "rotates".

Kind of like the tires of a Top Fuel car deforming as the wheel suddenly is spinning at you know 100MPH and the outside of the tire is sitting stationary on the skid. The tire twists as the material plays catch up ......

Yes, exactly as I explained... this deformation is no different then an acoustic wave travelling through the medium (compression wave) which causes oscillation of the distances between each of the molecules or atoms in the material. The deformation (twisting in this example) is just another manifestation of this and will travel at the speed of sound.

So, you would say that the crux of the matter is that we can't explain how sometimes observation entails one result as opposed to another?

Curious, and I'm still muddy on this, but we have not observed the speed of light from the center of our galaxy, or from another galaxy for example. All our observations are on or close to earth or that which earth has received from afar. Not to suggest that the laws of physics could be different elsewhere, but in areas of different mass would it be possible to find different values for the speed if observation were from another area in the galaxy?

Assuming you are not familiar with General Relativity, your question is ironically inquisitive. I think you would be interested in reading up more on General Relativity as its whole basis is on this exact concept (perspective and its effects on the speed of light). To give a hint, touching on your first comment, it is precisely not the crux of the subject.

 

[stueyG]

My feeling has always been that the underlying math behind the "cosmic speed limit" was fundamentally flawed. If I make the initial assumption that 1+1=3, then I can go through a very complex proof that eventually proves that 1+1 does actually equal three. While there will be a flaw somewhere in that proof, the only way I will find it is by ultimately realizing that my initial assumption was wrong. Similarly, I think Einstein's calculations were based on an unformulated presumption that there wasn't any particle in the universe whose velocity exceeded c (ie a tachyon).

This has already been answered pretty well. However. You can "prove" 1+1=3 by multiplying by zero, or by doing something else thats mathmatically wrong. Tachyons are a theoretical quantum mechanical dowhatsit, which makes then far more conceptually messy (almost by definition) than absolute c.

 

[keenan]

I think you are answering a different question, that's how your local GPS receiver is calibrated. It's constantly updated time of its quartz clock based on the satellite times.
I don't know if the satellites themselves are even calibrated at all after being put in service, they ARE the source of the calibration. I believe they are actually atomic clocks in each of the GPS satellites. Someone more knowledgable correct me if I am wrong (that may be yourself )

Each GPS satellite contains (at least? I don't recall exactly) two atomic clocks. I think some of them have 1 Rb and 1 Cs clock, while the newer ones have 2 Cs clocks. They're monitored from the ground to align them with UTC over the long term and make sure their drift etc. is reasonable.

Also somewhat amusing/relevant link I was trying to find for the last post: http://www.leapsecond.com/great2005/

Precise time enthusiast drives into the mountains on a road trip taking along an atomic clock, and is able to measure the relativistic shift between that clock and a similar one he left at home when he returns. Our best clocks today are damn accurate.

 

[Sergius64]

I think the argument from a fundamental standpoint just sounds very "human".

When we first discovered external transportation, our only reference was biological propulsion. The "leg". We used animals to pull our vehicles. The horse became the standard. There were animals that were faster then a horse, but they lacked the thrust a horse could generate and thus couldn't propel usefull weights. Likewise there were animals that could generate more thrust then a horse, but they did not have the high RPM of the legs so they were slower.

Sure we could push a horse harder, but it had negative physical effects and becomes unstable as you surpass the natural limits of the leg. So in order to go faster then the horse, we had to replace the horse itself. Eventually technology prevailed and we created the engine. It could generate more thrust and could operate at a higher RPM. Thus we surpassed the speed of biology.

Next we took to the skies. The propeller was used intially. This worked by displacing air. So then we ran into the next limit. How can you go faster then air when the air doesn't want to move any faster. There were some examples of prop based planes that tried to surpass the speed of sound. But again we ran into the same problems. It took way too much energy to do it and you ran into big stability issues.

So we replaced the prop. And moved to emission propulsion, the rocket. Chemicals or energy are emitted and pushes the transport. Finally we beat the speed of sound.

So now we have again arrived at the same fork in the road. Emission is currently our best known method, and the fastest thing we know of that is emitted is light. So how to we go faster then light? Again it takes alot of energy to beat it using the same method and again we run into weird anamolies if we were to do it.

So again we must create a new method of propulsion. And just like the reciprocating engine was unknown to early man on horseback and the jet engine was unknown to early pioneers of flight, the next method is currently unknown to us.

I keep hearing this argument from laypeople: "people used to think x wasn't possible to do and then we did it, so we'll figure out how to travel to other stars." I'm of the opinion that we're going to hit a brick wall on this particular iteration since in this case the laws of physics kinda state that we simply can't do it. Kinda makes all those "possible alien civilizations" irrelevant too, if we can't realistically reach them and they can't realistically reach us, their and our existence has absolutely no bearing on each other.

That being said, maybe we don't need to "invent" that new idea for travel? If we make the current technology a lot more efficient we could start trying to reach the nearest stars with unmanned craft. Sure it would take forever, but we've already accepted that: it's going to take New Horizons another 5 years to get to Pluto and it's already been going for 4. With Proxima Centauri being 4.3 light years away, maybe it will eventually be feasible to send some unmanned probes there with flight periods of less then 100 years...