In Which We Discuss Time, and Time Travel

[Chazumi]

I have always been fascinated and curious about this subject, but sadly I still don't know too much about it. Wiki says "Do not attempt at home" but some things I guess I don't understand. A good quote I read from Philip Jose Farmers To Your Scattered Bodies Go book was: "Time is just a device used to describe events in a linear fashion." This quote stemmed from the fact that on the riverworld of his book people were immortal (kind of).

Some questions I have about time and time travel are:

1. Where does our modern calendar come from? I believe it's the gregorian version, I read that in Guns, Steel, and Germs but forget the author.

2. Wiki seems to make me think that forward time travel is a lot more plausible than backwards time travel. Of course as long as you discount chryostasis, would this only be possible by reaching light or near-light speeds?

3. From question 2, doesn't Einstein's theory of relativity say you cannot travel the light of speed? I am a little shady on what he exactly proved with that theory. Speaking to my dad about near light or light travel a few years ago we posed the theory that if you were traveling at say, 100,000mps (Miles per second) (speed of light being 186,000mps), wouldn't a single grain of space dust rip your ship apart?

4. What about parallel universes, do these (supposedly of course) exist in a different dimension similar to 1st, 2nd, 3rd, and 4th (4th being time itself I believe), such as 5th, 6th etc., or does the 4th dimension support these parallel universes?

Are there any questions you have, or answers to these?

 

[holy king]

ask this guy about the dangers of time travel:

 

[emzie]

3. From question 2, doesn't Einstein's theory of relativity say you cannot travel the light of speed? I am a little shady on what he exactly proved with that theory. Speaking to my dad about near light or light travel a few years ago we posed the theory that if you were traveling at say, 100,000mps (Miles per second) (speed of light being 186,000mps), wouldn't a single grain of space dust rip your ship apart?

It's a serious concern to the Space Shuttle program. In 1983, a paint chip (or something along those lines) hit a window on the Challanger causing this

Stuff in orbit travels at 16,000mph. Per hour. Clearly such ultra-fast travel would have to overcome 'space junk' though 'space junk' would be rare outside star systems.

 

[stormbind]

It has been hypothesised that holes in dimensions allow the passing of energy and that gravity may be a force that originates in some other dimension.

In France, they soon intend to switch on an accelerator (made of relatively small amounts of matter) that is designed to make tiny black holes. Sadly, this scares me, and hopefully Mise will explain to us why it is known to be safe to make small holes that may grow exponentially and suck in much larger of amounts of matter (the size of solar systems).

 

[brennan]

You mean the Large Hadron collider at CERN.
The idea that the LHC will produce small black holes is not actually supported by the Standard Model. Even if it did, these would be subject to rapid decay by Hawking Radiation, and they are so small as to be unlikely to interact much with the surrounding matter. Source.

 

[gangleri2001]

ask this guy about the dangers of time travel:

He is not a time traveler.

 

[holy king]

He is not a time traveler.

pff, he's his own grandfather...

 

[stormbind]

You mean the Large Hadron collider at CERN.
The idea that the LHC will produce small black holes is not actually supported by the Standard Model. Even if it did, these would be subject to rapid decay by Hawking Radiation, and they are so small as to be unlikely to interact much with the surrounding matter. Source.

Doesn't Hawking Radiation require anti-matter and warp coils?

 

[MrCynical]

2)Travelling at close to the speed of light would essentially result in you travelling forward in time (faster than normal). Just head out from Earth at 99% light for a few months (from your perspective), turn round and come back, and you'd find many years would have passed for everyone else. Travelling close to, but not at, the speed of light is definitely posible, though it would require a huge amount of energy to accelerate you to that speed. Would obviously be a one way trip though.

3)There are a number of important equations which will produce a divide by zero error if you try and plug the speed of light into them. From the number of properties (such as mass) that would work out as zero, infinity or nonsense at light speed, it probably isn't possible.

An object hitting you with a relative velocity of 100,000 miles per second would do an incredible amount of damage. It would probably convert most of its mass straight to energy (another practical problem with getting a ship near light speed since space is not a perfect vacuum). Even at the orders of magnitude lower velocities encountered in current space travel, a very small object can do a lot of damage.

4)The 4th dimension is generally taken to be time, rather than some alternate universe. I've never really seen an intelligible explanation of the alternate universes theory - surely they'd each have their own set of space and time dimensions, which are nothing to do with our own? I suppose you could sort of treat the spectrum of every possible choice that could be made as another axis - 5th, 6th or whatever dimension. Question I've always wanted an answer to is why 3 sspace and 1 time dimension? It isn't very symmetrical.

 

[pau17]

It seems any backwards time travel to our time or before would have to have already happened. Which would link the past and future in some weird ways. I haven't really gotten my head around it but I'm not really sure that it's possible.

But yes, I heard that flying paint chips could potentially be as destructive as a hand grenade if they hit the space station.

Also, this program has a chapter on parallel universes:

http://www.pbs.org/wgbh/nova/elegant/program.html

 

[Rhymes]

I read an article some years ago that explained how time changes speed depending on the speed variation between two bodies... Basically, the faster you move, the slower time moves.

On realistic proportions, if you spent all of your life traveling around the globe in a concorde jet, you would travel forward in time by about 10 seconds.

If someone could move around the globe at the speed of light, time would be X time slower. (as far as I remember the factor was something like 8?). So if he would travel 1 full year (from his point of perception) at the speed of light, he would land on earth and 8 years would have passed.....

 

[pau17]

I read an article some years ago that explained how time changes speed depending on the speed variation between two bodies... Basically, the faster you move, the slower time moves.

On realistic proportions, if you spent all of your life traveling around the globe in a concorde jet, you would travel forward in time by about 10 seconds.

If someone could move around the globe at the speed of light, time would be X time slower. (as far as I remember the factor was something like 8?). So if he would travel 1 full year (from his point of perception) at the speed of light, he would land on earth and 8 years would have passed.....

Yeah, some of that discussion is going on in this thread:

http://forums.civfanatics.com/showthread.php?t=271008&page=8

...and here is a link I posted in it about the time issue:


http://en.wikipedia.org/wiki/Lorentz_transformation

 

[dwaxe]

FYI, the reason space debris normally wouldn't hit a space shuttle, satellite, or space station, is because the cloud of space debris is much farther out in orbit.

 

[LightFang]

Objects get heavier as they near the speed of light. So you can't travel at the speed of light in a vacuum because then you'd be infinitely heavy.

 

[emzie]

Objects get heavier as they near the speed of light. So you can't travel at the speed of light in a vacuum because then you'd be infinitely heavy.

Are you calling me fat?

 

[LightFang]

Are you calling me fat?

Man, see what I have to deal with? Not only corpulent, but also doesn't know when I'm insulting him!

 

[History_Buff]

From the top.

Some questions I have about time and time travel are:

1. Where does our modern calendar come from? I believe it's the gregorian version, I read that in Guns, Steel, and Germs but forget the author.

It essentially derives from the Roman one. People have know since at least Babylonian times how many days were in a year, and have been producing decent calendars. The Julian Calendar was used by the Romans, but it was off on the proper year length (~366.25 sidereal days) and so it drifted over time.

The Gregorian calendar was introduced to correct the problem, and is the source of the current leap year rule. The general idea is to hold a certain day close to the Vernal Equinox, which I think was done to hold Easter close to the same point each year (which for the Catholic church was a big deal).

However, calendars are annoying and complicated. They are modelled around solar days which is meaningful, but days lengths change, and they can't be used to predict extra-terrestrial happenings. That's why TAI is so awesome. Very stable, and easy to keep track off. GPS time is a simple integer offset of TAI, and so is UTC. UTC is more complicated though, because there's leapseconds involved.

Basically time is a big mess. I took a course in University that was nearly half time systems. It was unpleasant.

2. Wiki seems to make me think that forward time travel is a lot more plausible than backwards time travel. Of course as long as you discount chryostasis, would this only be possible by reaching light or near-light speeds?

Wiki lies Forward 'time travel' can be created through time dilation. Move really fast, and your time relative to the slow parts of the world slows down. Time dilation occurs the second you start moving at any velocity, but it's not noticible until you get into orbital speeds. The clocks on the GPS satellites are told to ocsillate slower however, to account for time dilation. To see whole years dissapear, you would need to be very close to c.

3. From question 2, doesn't Einstein's theory of relativity say you cannot travel the light of speed? I am a little shady on what he exactly proved with that theory. Speaking to my dad about near light or light travel a few years ago we posed the theory that if you were traveling at say, 100,000mps (Miles per second) (speed of light being 186,000mps), wouldn't a single grain of space dust rip your ship apart?

Essentially yes. It should be impossible to move faster than the speed of light. But what the theory actually says is that information cannot travel faster than the speed of light. Thats something of a confusing concept though, look up group velocity if you want to know more.

But keep in mind that Special Relativity doesn't reconcile itself well with quantum physics, so it might well be flawed somewhere.

As for the grain of dust, yeah, it probably would. Force projected is a function of momentum, which is the product of your mass and velocity. Even really light particles with high relative velocities can be very dangerous. And since space (particularly LEO space) is rapidly filling up with assorted space junk, it's not a pleasant thought.

4. What about parallel universes, do these (supposedly of course) exist in a different dimension similar to 1st, 2nd, 3rd, and 4th (4th being time itself I believe), such as 5th, 6th etc., or does the 4th dimension support these parallel universes?

Are there any questions you have, or answers to these?

Multidimensional theories are very theoretical. Scientist are looking at them, but I don't think any proposed system ties into the Standard Model very well.

 

[History_Buff]

FYI, the reason space debris normally wouldn't hit a space shuttle, satellite, or space station, is because the cloud of space debris is much farther out in orbit.

Not the case. Thats true at Medium and High Earth Orbits, but at Low Earth Orbits, where the shuttle and ISS operate, there is a bigger and bigger cloud of space debris accumulating, and it is becoming a serious problem. Most satellites launched are just used until they fail, at which point they are left floating up there, or blown up and then left floating up there.

And the stuff in higher orbits does eventually get pulled down into low earth orbit.

 

[Defiant47]

Backwards time travel could easily cause a paradox causing the destruction of the universe, so that leads me to believe that it's not possible.

 

[scy12]

I have just traveled and i am now traveling in the future so i do believe it's possible to time travel in the future. The most reliable way to time travel into the future is not to die. And cell replacement might be a way to do so. Other ways could be i imagine uploading your personality at a computer.