The concept of time travel

I recently heard an interesting explanation of time as being measured by entropy. The overall entropy of the universe is always increasing, so if you were able to measure that overall entropy, it would act as a kind of universal timestamp. This means that time is merely the particular set of conditions of every tiny piece of the universe, and according to the laws of thermodynamics, it would rule out time travel: entropy is always increasing in a closed system and you can't decrease it.

However, time dilation and such with relativity do make for interesting thoughts about what it really means to "time travel".

Correct. Entropy is what physicists refer to as 'time's arrow'; time progresses in a way such that total entropy in the universe is always increasing. But this ALONE does NOT rule out the possibility of time travel. The second law of thermodynamics is merely a consequence of time progressing in a way that increases entropy. In other words, the second law of thermodynamics is a result of time's arrow, and not vice versa.



I find that many, many people completely misunderstand the concept of relativity. As I wrote in a previous post on the same page, the word 'relativity' itself already implies that it's relative; depending on how fast one frame of reference is moving in relation to another, you have time dilation, mass increase, and elongation relative to another frame of reference. Therefore, time travel is impossible; time travel involves appearing back at the same place but at a different time, which is impossible according to relativity because you're at the same frame of reference. In other words, according to today's bulk of scientific knowledge we have, time travel is impossible. If you want to know what happens if you travel close to light speed (exceeding it is impossible for obvious reasons) to some place and back, see my previous post.

Also, I don't think black holes and gravity provide a means to time travel, at least, with current scientific knowledge. Gravity is still a relatively fuzzy area of physics; we have no idea how it operates, just that it exists and what its effects are. Plus, if you reason with what Einstein said about frames of reference, technically, inside the black hole and outside of it are different frames of reference, so even if it's possible to leave it, by similar logic, it does NOT mean you can time travel.

Personally, I think that time travel, no matter how much I want it to be true, is simply wishful thinking. Putting it in perspective, time is a concept. Time is an idea by man to measure the duration of an entity's existence and whatnot.

How can anyone travel through a concept?

I like this one. Just plain old "How can you do that within the confines of simplistic logic?" Thanks, I couldn't have said it better myself.

a little off-topic, but since everybody is talking about relativity, i'd like ask if "maximum speed", which is the speed of light, is the maximum speed of an object that goes towards or away from a point in a frame of reference which speed is zero...

....so, that means if something tries to accelerate further than the speed of light, it's time, relative to the frame, would probably speed up? or maybe slow down? ... so as to maintain the ratio and rate of displacement relative to that frame...

Has anyone read "The Time Traveller's Wife"?

Some people may not have a choice when it comes to time travelling. What if you are born with the ability, or rather defect, yet unable to control it? You may be sleeping on your bed peacefully at night and in the next moment, you find yourself naked on an expressway, 20 years ago, or into the future.

On the other hand, like what many people have mentioned, having control over such an ability brings about heavy responsibilites. Any action that one takes in the past may have a serious impact on the future. The world will no longer be the way that s/he knew it.

If time travel was possible, shouldn't someone in the future have already visited us?

That's what they said about Tesla, that his ideas are so far advanced that he was a time traveller.

No travelling back in time, so many possible changes can occur from virtually anything appearing in a place that in an original time it wasnt already. If time travel was possible going back shouldnt be done, however going forward would be awesome. I would love to just "boop" go check my future relatives or something, for that matter from the point where time travel is possible that society could go forward and give first hand accounts of their time. Of course going forward into the future would allow for a massive technological buildup in a short period of time which would be awesome to see if you dig sociology. Then again if we have developed time travel, would it mean we have reached a pinacle of technology?

if time travel was possible, Nazi Germany should have never existed
(i'm talking about C&C: Red Alert)

time travel is like turning lead into gold, which was the dream of alchemy

however, the most you could do with "time traveling" which would seem most realistic is to preserve your own existence: cold sleep, slowing down your own time (or speeding up the time of everything else around you), and such

its like 2am right now lol so im not gonna try to go to deep into this, but i want to ask if anyone has read the "Ender" series of books by "Orson Scott Card" its perhaps my favorite series of books in the world. Ive read each of them AT LEAST 2 times and starting with the second one: "Speaker for the Dead" it starts dealing more in depth with relativity, etc. And yea.......i'll try and post something of more substance when im able to start actually being able to seeeee my keyboard through all the yawning ankmldm ds m, c,m.JH:KRLZJNRS?GMDs.dg..............*error*.......*errorrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr*

If you go back in time, you better get the destination coordinates correct because the Earth is constantly in orbit and rotation... or make your time machine a spaceship!

Ultimately I believe that time travel is functionally impossible. As in, you just can't do it no matter how many black holes or flux capacitors you have.

But supposing you could "go back in time", what you would essentially be doing is forcing a collapse of a separate wave function almost completely identical to your own "world", except the difference between the worlds upon collapse from a quantum state is that a "you" identical to yourself in the first world is brought into being in the second world at a point where your second world self is younger. In other words, you effectively jumped to an earlier reality, even though there is no apparent change within your first world. To your first world self it would be like nothing happened at all, the experiment was a complete failure! But what actually would have happened is the creation of a whole new alternate universe and to this "identical self" it would seem as if the experiment was a success! Of course, any "changes" your alternate self would make to the second world would not effect the first world at all, because it's a separate existence to begin with.

we think the same way XD

Yes. I have read all of those books and they do show some level of... I guess life preservation. Are you talking about the ability to live almost and indefinite amount of time while moving at the speed of light? or are you talking about the weird instant teleport in the last books?

p.s. The first book was the best, but the others are a fun read as well.

True, it is impossible and even if you did manage it you may just cause a time rift or even start an entirely different universe but one thing is for sure. If I went back in time I would Google that last 20 winning lotto numbers and take them with me. :twisted: (I need the money)

you could actually do a lot more than that: take all the winning lotto numbers you could find and go back in time on the oldest winning number

Could'nt starting from the furthest back, alter what would be chosen in the future? If not then it would be the most interesting form of money laundering ever. If you start from most recent and planned to go back to each previous time to win the lotto, the cash should already have been placed into you're present account. Kinda like the whole Bill and Ted where would I leave the key thing.

you're right
any alterations on the past could potentially alter the near future
so the next winning lotto numbers would be invalid

but if your reason to go back to the past was to win the lottery, then your future self would try not to go back to the past to win the lottery
so there would be two instances of yourself in the future

if this was the case, another use for time traveling is to duplicate yourself XD

[quote="jonsmth"][quote="Coro"]

Your both thinking way to hard. Go back to 1980's win one lotto and invest it all in Apple. It probably would have grown to about 20 billion by now and I would finally have enough to buy Cuba. That country could be like a fixer up housing project on a massive scale.

we like cash

better yet, go back to a past where a temple or tomb is waiting to be plundered

or go back to a past where you will be treated like a god