Time Travel: Possible or Impossible?

Great Debates
61

Alright then…after reading through everyones post, I found myself getting dumber. Not that anyones theories or opinions are at all unintelligent. But, I have to admit, reading everyones point of views have twisted my own personal views…which isn’t necessarily a bad thing.

Now, from what has been discovered about the relativity of time. Time travel into the future is very possible, simply by slowing down time for self through the rate of movement. The only thing that prohibits this is a vehicle that can generate enough energy to propel a human being as fast or faster than the speed of light.(Not to forget the affects of moving this fast on the human body.) Although this can be achieved now, but only in measurements of seconds.

So lets say we have what it takes to do this. The pilot of this vehicle has a twin. The pilot travels out a one year from earth at the speed of light. Upon his return back to Earth, his/her twin has aged what? 6-7 years to the pilots one year?
I can’t disagree with this, simply because I haven’t studied physics.

But what I am having a serious issue with is, understanding what time is now. Yes, yes, I know, I know, a simpleton will tell me time is a form of measurement. That is not what I’m asking. The question is just that, “What is time?” What dictates the “movement” of time? Is time a force with momentum?

I’m an artist, so I’m better with picturing things to help myself understand.

Through explanations of traveling to the speed of light or beyond. The thing or person can (to loosely put it,)“cheat”, time that has once governed him or her through the rate of speed (or placement in other galaxy?)

For example:
There is a pond and you were able to generate a whirl pool in it’s center. This whirlpools center represents time.

Now, we drop a row boat in it’s center. It’s stuck because it cannot generate enough energy to drive out. Only to experience the full effects of it’s center/time.

Now, we take a motor powered boat. It has enough power to drive out of it’s center but not enough to go beyond it(we’ll say its on inner edger of it.) So this motor powered boat, is still affected by the whirlpool, but instead of sharing the affects/effects of the whirlpools center, it is now traveling around the centers slower rate of speed/time.

They say astronauts experience time traveling but in mere seconds. Is this due to the speed of the launch, or for being in orbit?

Now the above example may be wrong to compare to or use as an example of time. But…it’s the best I could come up with for myself.

Sorry if any of this is confusing, but I’ve managed to confuse myself pretty good. So it’s only fair.

62

Well, you are wrong. Time is a literal, physical thing.

Planck time as I understand it is the smallest meaningful time.

63

[nitpick]
You cannot travel at or above the speed of light (as measured in a vacuum). It is an absolute limit. You can get arbitrarily close to the speed of light but never reach it. Only massless (rest mass) particles can travel at light speed. Anything with mass that reaches light speed would have a lot of funky and impossible things happen to it (e.g. an infinite mass, time stops).
[/nitpick]

Yes, this is what would happen. The astronaut undergoing acceleration would age more slowly than his twin.

Time is not a set-in-stone kind of thing as most people’s intuition would inform them. This was Einstein’s brilliant insight with Special Relativity. He realized some issues with moving very fast and very slow and taking measurements. The classical way of looking at it would produce results that would mean people could make measurements of a speed of light higher than the speed of light. Thing is the speed of light will always be measure as the same by any observer in any reference frame (e.g. guy on spaceship zooming about and guy on earth). In order for the speed to be measured as the same by both observers time needs to speed up or slow down.

In short there is no preferred reference frame and any experiment done in one will come out the same in the other. Time needs to be flexible to allow this and that is exactly what occurs.

Try this YouTube visualization then. Helps a lot. Remember no one should measure a speed faster than light speed so the “classical” interpretation is wrong. They then show how time dilation fixes what would otherwise be paradoxical. Pretty good visualization.

It is due to both. Acceleration does it to you and when in orbit you are in constant acceleration (moving in a circle is a state of constant acceleration…even though you are moving at a steady speed you are changing direction all the time and that change can be viewed as an acceleration).

64

So lets say we have what it takes to do this. The pilot of this vehicle has a twin. The pilot travels out a one year from earth at near speed of light. Upon his return back to Earth, his/her twin has aged what? 6-7 years to the pilots one year?
I can’t disagree with this, simply because I haven’t studied physics

Thank you for the explanations.

Now, by this astronauts measurement, he/she has traveled for one year at near speed of light. Is it at all possible that this astronaut would age equivalent to the 6-7 years that his twin has aged, only to do it in one year? Hypothetically, all that has changed is the perception of the astronauts state of time? Astronaut, thinks and in fact did travel for only one year. But those on earth has actually experienced 6-7 years. So would he too experience this on a cellular level?

Or am I again lost…lol

65

Nope.

His actual clock will move more slowly. The “slowed down” astronaut however will perceive everything as normal. To him 1 sec = 1 sec. His perception of time remains unaffected.

Again, it is frames of reference.

1 Frame of Reference is the guy on earth.

Another frame of reference is the guy in the spaceship.

They will actually disagree on some things when viewing each other. As noted in that video I linked simultaneity will be broken (they will disagree on the order of events). Again look at the video. To the guy on the cart the photon are moving straight across the room. To the outside observer the photons are tracing out an angle.

As for how much you slow down it depends how close you get to the speed of light. Time slows down for you when you fly in an airplane (this has been experimentally tested) or even a car for that matter. The difference however is vanishingly small. It is not a linear progression either. You do not see noticeable time dilation till you are 85% or so of light speed. The closer you get the slower and slower it moves. Get close enough and as I noted before you could pass 32,000 years in a tad over 3 seconds.

ETA: I should note the above has been verified experimentally. Einstein is spot on in this regard.

66

Is this really time travel? Seems to me like you’re really just slowing the body’s decay and your own observation of time. Same thing as SciFi movies “deep sleep” or people freezing themselves to be revived in the future.

Literal, sure. We’ve defined it and it has a specific meaning. Physical? How so? Even planck time is just a number based on the movement of light. The light is the physical thing. Time is just a concept based on the properties of that physical thing. Time doesn’t exist independent of some physical thing used to define it. To me, that means it’s just a concept that we came up with.

67

I get your point. But add in a (admittedly hypothetical) wormhole as I described and you could pop back and forth at will.

And, as far as you are concerned, you moved yourself forward into the distant future in a matter of moments. Even if it is one-way it would still appear to you like you jumped forward in time.

68

dedmonwakin:

Here’s another illustration to help you with what you see in the video I linked. It may be a bit easier as a first step in getting your head around it.

Imagine you are on a train with a table in front of you. The train is moving forward. You bounce a ping-pong ball on the table. What do you see? The ping pong ball bouncing straight up and down (you can try this in a car too). If I asked you to draw the ball’s trajectory you’d draw a vertical line (up and down).

Now imagine I am standing on the train platform as you pass by. Someone asks me to draw the ball’s trajectory. I would not see the ball going straight up and down. Instead, because it is moving forward with the train, I would see the ball describe and arc. It’d hit the table at one end of the platform, start traveling up and come down at the other end of the platform.

Which of us is right? Both of us are. It is all based on which frame of reference you are using (inside of train or on platform).

You can extrapolate that out. Hold real still a second. Are you moving? Yes and no. Compared to your desk you are not moving. But in reality the earth is revolving, the earth is orbiting the sun, the sun is orbiting the galaxy and the galaxy itself is moving. To an observer outside our solar system you are moving quite a lot. Or, from our perspective, the observer outside our solar system seems to be the one moving. Who is right? We both are.

Melts the brain I know. :smiley:

69

If you want a visual explanation try this video. It actually goes beyond time to ten dimensions.

Also, part of the disconnect is we are all time travelers. We just travel at 1 second per second. Relativistic speeds don’t change how fast you are moving through time within your frame of reference, they just change your frame of reference. To make an analogy with spatial motion, picture two people traveling to the same place in space, say going from one house to the next. If they take different paths to get there they can travel different total distance (say 1 mile and 2 miles) but still end up in the same place. Relativistic speeds warp the “path” you take through time so that you can reach a certain point in time in less seconds, just like taking a short cut can let you reach a point in space going fewer miles.

Jonathan

70

If time travel is invented, I expect lots of people will want to go see the crucifixion and it’ll be very crowded.
I’ll be the guy holding the JOHN 3:16 sign.

71

Whack-a-Mole it seems you forgot to actually link the video you are claiming you linked back in post 63 or I am link blind. Could you please post the link as I am very interesting in seeing it. Thanks. :slight_smile:

72

Doh! :smack:

Sorry.

Here it is: Visualization of Einstein’s Special Relativity (nifty vid…helped me a LOT to visualize it a lot better)

73

Thanks. I can not watch youtube at work but I will definitely be checking it out once I get home. This is a very intersting thread btw.

74

Here’s a site with some great visualizations and clear explanations of time dilation and the twin paradox.

For those of you arguing that time is a human construct, do you feel that space is also a figment of our imagination, or does space have a physical reality?

75

FYI, almost nothing at that site (and in that video) has anything meaningfully to do with what scientists and mathematicians are talking about when they talk about higher dimensions.

It’s roughly talking about what they’re talking about up to dimension 3,* but after that, it goes nuts.

-FrL-

*And even there, the video gives a terrible explanation, difficult to follow unless you already know what it’s talking about.

76

I appreciate the agreement, in part, but, like measuring physical properties, TIME (minutes, hours, days) is the measurement of events.

77

Don’t just proclaim it, show it.

78

Sure (bolding mine).

Pretty sure no one has debunked Al yet on this one.

That or we could give you a watch. :wink:

79

Wow, reading about quaternions makes my head hurt.

I guess my views on time really come down to this: there’s only one me. For argument’s sake lets say time is the 4th dimension and we’re all moving through it together. To me that would still make time travel impossible as far as going to the past/future. Since I’m moving through time, that means for any infinitely small instant in time, I’m going to pass through it instantaneously. To an observer stationary in time, I basically blink in and out of existence. So going to any particular point in this 4th dimension after I’ve been there means I won’t be there anymore and will never be there again (since I’ll continue moving forward). Going to a point ahead of me means I’m not there yet, but eventually I’ll blink in and out.

There was something I saw on TV once, maybe it was a Twilight Zone episode. The story was basically that this person managed to time travel jump a few seconds ahead. He was in an empty world since nobody else had gotten there yet. However, he continued to move through time normally so the rest of the world never caught up to him. He basically ended up alone forever. The story might have been the opposite where he jumped back and was forever behind everyone. I wish I could find it to watch again because I don’t remember it all that well and would like to watch it again. I think this is what would happen if time really was the 4th dimension and somebody found a way to speed/slow/jump through it.

Anyway, after all that, it makes a lot more sense to me that time is just a human concept and not some actual 4th dimension. That doesn’t mean I discard the possibility of some 4th dimension and beyond, just that I don’t think our concept of time is that 4th dimension.

As far as special relativity and the speed of light being the same in all frames of reference, it’s not that hard to explain without the existence of time. It just means that a clock, a human made object, is affected by its speed. To a fast moving observer, his clock is running slower, and the light is moving slower relative to him, which makes the speed calculation the same. However, this is just my admittedly amateur understanding of the theory, and you guys will probably laugh at me.

80

No…time really slows down in an accelerating reference frame. This has been proven in numerous experiments and all are in keeping with Einstein’s predictions. Not only that, they need to account for time dilation in our GPS satellites so they remain accurate. The time dilation they experience is small but they use super accurate clocks to do their thing and their movement is enough that even the minor relativistic effects on their clocks would eventually add up and make them worthless. So, there is a practical application of Special Relativity.

Not only does time slow down when you go really fast but distance in the direction of travel contracts. If you could go light speed the universe would appear infinitely thin to you. The combination of this contraction and time slowing down conspire to make it so anyone, in any frame of reference anywhere will get the same answer when measuring the speed of light.

Lastly time as a dimension is not considered a spatial dimension. That is why they usually refer to 3 dimensions + 1 Time dimension to distinguish it from four spatial dimensions. That said it is a dimension after a fashion. If I want to meet you somewhere in space we would use three coordinates to specify its location (in 3d space that we live in). That is fine and will get us both to the same place. But there is a fourth coordinate you can use. When will we meet at that point? In this way we need to use four coordinates to specify a point in spacetime.