Time Travel

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Time Travel

Postby Humigotchi » Fri Apr 02, 2004 12:51 am

I'm basically in love with this topic, the basic theory is stated that you must be going the speed of light, and then you should travel into a wormhole to become a traveller in time.
And now just recently I have discovered scientists have already sent particles 8 times the speed of light.
This is an amazing thing.
If we could ever take control of the speed of light, and make a safe space shuttle go that speed (which is about 200, 000, 000 meters per second), we could get to Andromeda in about 4.3 years.
This is an amazing thing once again.

I'd like to hear your opinions on this
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Postby Dev » Fri Apr 02, 2004 1:24 am

Wow your smart. Can you like give us the website? Dude, this sounds so interesting. Sorry for the short replies, i don't feel really good today
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Postby TerraFrost » Fri Apr 02, 2004 2:23 am

wikipedia.org has some interesting (and easy to understand) articles on the varrious subjects you've touched on... here they are:

using wormholes to travel back and foward in time:
http://en.wikipedia.org/wiki/Time_trave ... _wormholes

faster than light "travel":
http://en.wikipedia.org/wiki/Speed_of_l ... xperiments

as far as space ships being able to travel at or faster than the speed of light... i believe there was a scientific american article that talked about possible engine designs (although all of them depended on technologies / theories that hadn't yet been developed), but perhapes my memory fails me... i can't find any websites talking about such things, either...
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Postby Neosurfur » Sat Apr 03, 2004 5:48 pm

Wow... that is pretty cool, but what effect would that have on the human body? O.o O_O
Can you amagine going that fast for 4 years???
Plus that would take sooooo much money the gov't wouldnt know what to do except tax us,..., but back on the subject...wow, see if you can find anything on this effect on the body and please reply. :MIB
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Postby paleofrrrost » Tue Apr 06, 2004 3:46 am

TerraFrost wrote:<snip>
as far as space ships being able to travel at or faster than the speed of light... i believe there was a scientific american article that talked about possible engine designs (although all of them depended on technologies / theories that hadn't yet been developed), but perhapes my memory fails me... i can't find any websites talking about such things, either...


I can't talk authoritatively about "faster than light" travel, btu I can talk about "close to the speed of light" travel.

One of the weird things that Einstein predicted was that the faster you travel, the slower time passes for you. I forget what the exact formula is, but it's not too complicated.

The example usually given involves twins. One stays on Earth, the other travels at something like 80% of the speed of light to someplace, then comes back. The twin who stayed on Earth will be older than the twin who traveled.

This effect is called "time dilation."

Another interesting thing is how fast you can go in space just by constantly accelerating. Our current space ships (rockets) only accelerate for a short period of time, a few minutes, then coast most of the way. They coast at thousands of miles per hour, but that's pretty slow in space.

If you can accelerate constantly for a long period of time, you can achieve enormous speeds. You don't have to accelerate hard to do this either; it can be a very gentle acceleration, just as long as it is constant.

An example of how this can shorten space travel involves travel to Mars. The way we do it now, we launch a rocket that burns for a short time, then the spaceship coasts around the sun eventually catching up with Mars. It's a journey that takes months.

I don't have the math right in front of me right now, but if I remember correctly, an acceleration of as little as 1/10 of a gee (or 0.98 meters per second per second) will get you to Mars in about 7 days. The same acceleration will get you to Pluto in 7 weeks.

To picture how little this acceleration is, a car accelerating from a stop at 1/10 gee would take 10 or 11 second to get to 30 mph. On the other hand, if the car could keep accelerating at that rate for an hour, it would be going almost 8000 mph. If the car kept that slow acceleration up for 24 hours, it would be going almost 190,000 mph. If it kept it up for a month, it would be going 5 or 6 million mph.

Anway, when I first read about this, I started wondering what that would mean in terms of making interstellar travel possible. I worked up a spreadsheet that let you enter an acceleration, and then it would tell you how long it would take to get to verious locations, like Alpha Centauri, the Andromeda Galaxy, across the universe, you know, the places everyone wants to go. :)

I quickly realized that unless I took relativity into account, my math was meaningless because it showed me exceeding the speed of light fairly quickly. So I found a formula that took time dilation into account and put it in my spreadsheet.

In a nutshell, what it showed was that if we could design a ship that could achieve a constant acceleration of one gee, meaning the passengers would feel the same force that we do on the surface of earth, humans could travel anywhere in the universe within a typical lifespan of 70 years. This is because the spaceship would be traveling so close to the speed of light that the passengers' time would slow down and they would still be alive at the end of the journey, even though thousands of years might have passed on Earth.

It's weird, and I don't think I did a good job of explaining it. It's a lot clearer if you just do the math.

The main thing is, interstellar space travel is in theory possible already. It's just up to the engineers now, to build a spaceship that will support humans for years, and to give it a propulsion unit that will accelerate it at one gee for years.

The only problem is that it would be one-way travel. You couldn't come back and tell anyone about it, because everyone left behind would be long dead. So true two-way travel would still require faster-than-light travel.

Somebody else will have to figure that one out. I can't.
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Postby ChatOmbre » Tue Apr 06, 2004 4:11 am

Wow... that's awesome! And I think you explained it fine.
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Postby TerraFrost » Tue Apr 06, 2004 5:32 am

The main thing is, interstellar space travel is in theory possible already. It's just up to the engineers now, to build a spaceship that will support humans for years, and to give it a propulsion unit that will accelerate it at one gee for years.


while this an understandable conclusion given newton's laws of motion, which state that F=ma, i believe it still violates the general theory of relativity, which redefines F to be equal to mass times acceleration times gamma, where gamma is defined as 1/sqrt(1-v/c), where v is the velocity and c is the speed of light.

at slow speeds - which is where newtons laws of motion are usually applied - gamma is usually *very* close to one. thus, newton's definition of force and einstein's definition of force are practically the same. however, as v approaches c, gamma approaches infinity, as does force. it will always do this, no matter the mass or the acceleration (save for in the case where mass is equal to zero). newton's definition of force doesn't do this. thus, we have a small contradiction, and thus, any conclusions based on newton's laws as v approaches c, are incorrect - atleast assuming the general theory of relativity trumps newton's laws of motion, which it does.

to modify your proof of the plausibility of intersteller travel so as to account for this aspect of the general theory of relativity, force would have to be increased, exponentially, as the velocity increased. in other words, it would take more effort to accerate 9.8 m/s^2 when you were traveling at a velocity equal to half the speed of light than it would to accelerate 9.8 m/s^2 when you were traveling at a velocity of, say, 10 m/s. it would take infinite force to travel faster than the speed of light (which is also quite possible according to newton's laws of motion).

on another note, time dialation occurs in conjunction with a reduction in physical distances, as per the lesser known lorentz contraction. a proof by contradiction follows.

assume no reduction in physical distances takes place. further, assume that the speed of light is 2 m/s (the speed of light need only be finite bounded for this proof). if an object (object A) travels at this speed of light (2 m/s) for 10 seconds, it will have traveled 20 meters. due to time dialation, however, the passage of time of objects not traveling at the speed of light (let's call one of these objects object B) will be longer than the passage of time for objects traveling at the speed of light. for the sake of argument, lets assume that a minute passed for those objects that weren't traveling at the speed of light. this would mean that while object A was traveling at 2 m/s from object A's perspective, object A would be traveling at 1/3 m/s from object B's perspective. this contradicts the fact that speed of light is constant, no matter the perspective (ie. it isn't allowed a reference frame), and as such, proves that reduction in physical distances *must* take place.

a demonstration of the fact that the speed of light is constant, no matter the perspective, is given in one of the thirteen episodes of cosmos (i forget which one).
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Explanation of these physics

Postby Humigotchi » Thu Apr 08, 2004 4:57 am

The questions you have asked are easily answered, Neosurfur asked about the question of the space module being able to support human life.
Basically, the speed of light isn't like the space ship is going so fast, but time is slower to us, so we may be going at say, 80 miles per second, and a minute lasts like, maybe a day or so.
So the answer to that question isn't that the module is going so fast that we wouldn't be able to survive, it is just the question of, can the human in the module survive for the period of 4.3 years or so.
This is all caught up into the theory of time dilation, which was explained almost precisely before.

Then, there was paleos statement of not knowing which theory of einsteins it was.
Mostly, that theory is relatively, which, by the way is the most massively stated theory, and is one of the most important theories in knowledge itself.

Now that confusion is gone, I want you to use your imagination.
The Russians have, after the U.S' many tries at time travel, taken this idea, and tried it themselves.
They have chosen three couples for a ship, which is about 23 ft x 28 ft.
The couples are mr. and mrs. jones, mr. and mrs. jackson, and mr. and mrs. moody.
These people were chosen because of the fact, if you send some random person into space for 4 or 5 years, they will lose their sanity because of loneliness and wither away and die, whereas couples will stand longer because they have someone they love there with them.
This ship travels through a complex navigated system in space to the galaxy m81 at 719, 915, 629 meters per second, which means they will arrive at the galaxy in about 7 or 8 years.
They depart.
At about 3.7 years through, the moodies die because of lack of atmosphere and "regular" gravity, this happens also with the jacksons.
At 7 years the jones are the only ones left, and they arrive at a civilized planet called Baron 660.
The complications to this are random, we don't know what could happen.
The jones then die because as they enter Barons atmosphere, the gravity crushes them due to the planets weight and pull to the sun.

The reason we haven't been really studying into this (the government I mean) is because even if we had the ship going at those speeds safely, what if there are black holes, asteroids, a complex gravitational pull.

What if....
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Postby Gigafrost » Thu Apr 08, 2004 4:05 pm

Wouldn't speed not really be a problem? Acceleration is what causes force. The only way I could see speed really being the problem is if going near-light speeds causes the electrons orbiting atoms to behave differently (since they travel at near-light speeds?) and that would modify the chemical interactions a bit? Hmmm...

Unfortunately, relativity deals with big distances and quantum mechanics deals with short ones (as I understand it). As I understand it, trying to figure out how both of these work is a major goal, hence why scientists want to be able to create artificial black holes (whose event horizons are supposed to be a good place to study how quantum mechanics and spacial relativity are related to eachother?)

Hmmm....
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Postby TerraFrost » Thu Apr 08, 2004 6:16 pm

Wouldn't speed not really be a problem? Acceleration is what causes force.


well, if the above alternative equation for force is true, then speed would indeed be a problem - especially as the speed in question approaches the speed of light.

The only way I could see speed really being the problem is if going near-light speeds causes the electrons orbiting atoms to behave differently (since they travel at near-light speeds?) and that would modify the chemical interactions a bit?


if the above equation is true, then why would you need to know what atomic interactions make it possible? i mean, i took newton's definition of force to be true without having heard of any sort of atomic leve justification for it. for me, the deciding factor for deciding it was true was that it was somewhat intuitive and an authority figure said it was true. neither of these really work for my above post. for one, i don't really have an authoritative website citing what my above post said, and for two... it's rather hard to be intuitive with the speed of light. time dilation isn't intuitive, although it's generally accepted as truth.
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Postby Gigafrost » Thu Apr 08, 2004 6:32 pm

Ah...the speed in that formula didn't stand out. I see. :)
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Re: Explanation of these physics

Postby paleofrrrost » Sun Apr 11, 2004 2:07 am

Humigotchi wrote:Then, there was paleos statement of not knowing which theory of einsteins it was.
Mostly, that theory is relatively, which, by the way is the most massively stated theory, and is one of the most important theories in knowledge itself.


Minus 10 points for reading comprehension .... ;)

I didn't say I don't know which theory ... that's easy, it's the Theory of Special Relativity. What I don't know is the exact formula I used to take into account time dilation when I was calculating what speed would be obtained over a given period of time and distance for a given acceleraion.

When I find it, I'll post it.
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Postby paleofrrrost » Sun Apr 11, 2004 2:16 am

TerraFrost wrote:
paleofrrrrost wrote:The main thing is, interstellar space travel is in theory possible already. It's just up to the engineers now, to build a spaceship that will support humans for years, and to give it a propulsion unit that will accelerate it at one gee for years.


while this an understandable conclusion given newton's laws of motion, which state that F=ma, i believe it still violates the general theory of relativity, which redefines F to be equal to mass times acceleration times gamma, where gamma is defined as 1/sqrt(1-v/c), where v is the velocity and c is the speed of light.

at slow speeds - which is where newtons laws of motion are usually applied - gamma is usually *very* close to one. thus, newton's definition of force and einstein's definition of force are practically the same. however, as v approaches c, gamma approaches infinity, as does force. it will always do this, no matter the mass or the acceleration (save for in the case where mass is equal to zero). newton's definition of force doesn't do this. thus, we have a small contradiction, and thus, any conclusions based on newton's laws as v approaches c, are incorrect - atleast assuming the general theory of relativity trumps newton's laws of motion, which it does.

to modify your proof of the plausibility of intersteller travel so as to account for this aspect of the general theory of relativity, force would have to be increased, exponentially, as the velocity increased. in other words, it would take more effort to accerate 9.8 m/s^2 when you were traveling at a velocity equal to half the speed of light than it would to accelerate 9.8 m/s^2 when you were traveling at a velocity of, say, 10 m/s. it would take infinite force to travel faster than the speed of light (which is also quite possible according to newton's laws of motion).


My plausibility argument (I don't think I "proved" anything) didn't say anything about force; I only assumed constant acceleration. How one achieves that constant acceleration is a problem for the engineers. ;)

As I told Humigotchi, when I find the exact formula I used, I'll post it. Then we'll have details enough for an actual argument. :)
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Postby TerraFrost » Sun Apr 11, 2004 4:33 am

My plausibility argument (I don't think I "proved" anything) didn't say anything about force; I only assumed constant acceleration. How one achieves that constant acceleration is a problem for the engineers.


ah. in that case, a better plausibility argument wouldn't have a steadily increasing application of force (as a constant acceleration would do), but rather, would apply a *huge* and momentary initial force, resulting in *rapid* initial and momentary acceleration. this situation, i believe, better clarifies the problem engineers would have to deal with (and indeed are dealing with) - that problem being how to create the most powerful engine possible.

As I told Humigotchi, when I find the exact formula I used, I'll post it. Then we'll have details enough for an actual argument.


i can't imagine a debate about the validity of a formula, heh :)
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Postby Real_Pochacco » Sun Apr 11, 2004 6:54 am

Now, whenever I talk about time travel, I always feel like I have no idea what I'm talking about, but I do know that at singularities (wurmholes) the laws of physics break down. Like they don't work. Ebeh?

Now talk to me about nuclear fusion, and I know a whole lotta stuff.
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