# Hawking Time Travel Experiment

1. Mar 15, 2012

### LuckyNate

((Wasnt sure where to post this one, but i felt this spot was good))

Okay Dr. Stephen Hawking conducted a time travel experiment in an attempt to prove that time travel will be invented one day. The basic idea was to throw a party for time travellers and announce the time and location of the party AFTER the party had already happened. The idea was that if anyone showed up to the party it would prove they found out about it in the future and had travelled backward thru time in order to attend.

While no time travellers were found to be in attendance, this did not PROVE that time travel will not be invented, only that nobody came. This could be explained due to a number of causes, a few of which I would like to touch on and eliminate here.

One big problem I immediately felt was obvious in this experiment was this...why should a time traveller go out of his way to attend a party thrown by Dr. Hawking back in the early 2000s (or 1990s, not sure when that party happened)? Of course, upon further reflection, what better event to attend than this one if you really could travel through time? I therefore threw out this possible explanation for the non-attendance of our time traveling friends.

Another possible explanation is the existence of a code of conduct or other preventive force which will grow alongside the advent of time travel and prevent those who wish to attend from being able to do so. However, I find it hard to believe that in all the time after time travel is invented nobody will EVER break the rules or overcome this preventive force, so again not a real solid answer as to why the party went unattended.

It therefore seems to me that if someone were able to travel time and knew of the invitation, that they WOULD attend the party eventually, so why then DID the party go unattended? It suddenly occurred to me that the conditions of the experiment are NOT mutually exclusive, and that our linear perception of the past may inhibit us from properly understanding the results of the experiment. The reason that nobody attended the time travel party is that the time travel hasn't been invented YET.

Doesn't it seem that the party would necessarily go unattended until AFTER such time as the experimental conditions are met (in other words AFTER the travelers go back in time)? After this happens, thinking back will reveal that we all remember when Dr. Hawking threw the party, and who it was attended by. These sort of nonlinear time effects may already be in play in our existing lives day to day, changes even to our own personal life history would be quite undetectable to beings who can perceive only the one dimension of time that we ourselves are limited to.

So, time traveler hopefuls, please don't give up just yet, there is still time to attend the Hawking Time Travel Party if you work hard and get that thing built!

Nate

2. Mar 16, 2012

### John232

Maybe they just didn't get the inventation. Or, maybe they new there wouldn't be any girls at the party... But, I think since Hawking already spilled the beans on no one showing up that it would be impossible for a time traveler to change the results of the experiment. Say a time traveler did find out when and where the party was supposed to be, he would also surely know that no one showed up, so how then could he arrive at the party because no one showed up and then change himself so that he heard that he did show up and then arrive for the same reason? So if he could change the past I think there would only be a 99% chance that the experiment could be succesful even if they tried to attend the party, and we would be in 1% of the cases it wasn't succesfull. The grandfather paradox would prevent the time traveler from changing himself, so then if he could change an event in the past that changed himself he would in effect would only be creating an alternate timeline. He could be affraid to create an alternate timeline that he was never born, that would in turn prevent the experiment from getting positive results once again. I think all it proves with some degree of certainty is that Stephen Hawking or anyone at Cambridge, didn't invent time travel.

If the alternate timeline scenario was true, then there would have only been one timeline the experiment didn't work because the next alternate would have worked and then so on etc. Then a majority of the timelines would have had a positive result and odds are that we would be in a timeline where it did work.

Last edited: Mar 16, 2012
3. Mar 16, 2012

### cyberfish99

The whole idea of time travel is that time is not linear. if it was, then time travel wouldnt allow the travel backwards, only forwards. There are too many reasons as to why they wouldn't show up. Most of all could be, maybe they did, it just so happened that the two different parallel universes spawned from hawking's party and the difference was in the one universe, the travellers showed up, and the other universe can be considered our universe. So they did show up, just wrong universe!

4. Mar 16, 2012

### Fastman99

Maybe only closed timelike loops are allowed modes of time travel. What I mean to say is that perhaps time travel is only possible if A causes B, and B causes C, and then C causes A, thus closing a loop between those three events. For example, you could only send a message to your past self if you had already received a message from your future self to send a message to your past self. Then you would inevitably do it. That was probably confusing, so I'll try a simple example with regular particles and tachyons, which can be observed to go back in time in the right frame of reference.

Take two particles 1 and 2 and suppose they are moving toward each at some high fraction of the speed of light. Particle 1 emits a tachyon to 2, call the emission event A. Particle 2 receives the particle, and call that event B. Event B is outside the lightcone of event A, and thus in some frame of references, event B happened before event A. Now if particle 2 sends another tachyon immediately after event B, it could be fast enough to reach particle 1 before A happens. Call when particle 1 receives the tachyon from 2 event C. Event C would occur before event A in every frame of reference, since both events lie on particle 1's world line. The only way this could happen is if C causes A to happen. Event C happens first and causes event A, the emission of the first tachyon. If you draw a Minkowski diagram of this, you get a causal triangle between A, B, C.

Causality would have to occur in a loop in order to make time travel possible. The only explanation for it would be that tachyons do some crazy stuff, and that it was just meant to be. Now, if it were possible to somehow create these loops, how would you get an entire human being in the loop?

5. Mar 16, 2012

### John232

Makes me wonder what versions of string theory that would also make this prediction, seems like it would be cutting it close if their where universal explosions from two universes "touching" each other. I would agree that time is not linear or parrallel to space itself, considering it is a dimension and all spatiel dimensions are not parrellel to each other.

6. Mar 17, 2012

### MathematicalPhysicist

You're overthinking it.

If a time traveller would attend such a party he might be captured by the people who helped organize it and they would know that he's a time traveller or a crazy man.

7. Apr 27, 2012

### gopolks

8. Apr 28, 2012

### Staff: Mentor

Time travel to the future is simple, as long as you ignore engineering problems. Just build a rocket which can reach relativistic speeds, use it for a while and come back to earth. Done.
Astronauts in the ISS do that all the day, but they need "1 year minus some microseconds" to travel 1 year into the future as they are quite slow compared to light.

Another possible option for the empty party: Maybe it is possible to travel to the past - but only if there had been some preparations for this events in the past.
Therefore, you have to invent time travel first and then build some machine in spacetime which can be used as the exit point of a time travel later on. As it was not invented at the time of the party, nobody could show up there.

9. Apr 29, 2012

### gopolks

Build A rocket that can reach relativistic speed, somehow I dont think that will get funding, still the idea that it could work is memorizing.

10. Apr 30, 2012

### nitsuj

I saw this too. Hawking has a good sense of humor.

11. Sep 16, 2012

### GDM42

Obvious flaws in the experiment.

1: Implying anyone is there to receive the message at all disaster, disease, etc.
2: Or ideology and social conditions are entirely unacceptable "from our viewpoint" Example World Order feudalism or other undesirable form of government that they wouldn't want to raise an alarm in the past.
3:Or they did receive the invitation and chose not to attend, solely because no one likes a smart a. LOL

It was fun to watch, but I'm not surprised that he was alone.

12. Sep 16, 2012

### mrspeedybob

Or, time travel is possible but the engineering of it requires the device to be in existence at the earliest time you wish to travel to. For example, a box that I could step into, and then step out of an hour previous. Obviously I could not travel to a time before I built the box.