Time travel?

[silverpig]

Originally posted by: jb
you did bring up some things i forgot. what i was getting at/questioning is that:
why the infinite mass? isn't the speed of light approx. 300 000 kilometers per second? doesn't that give a finite mass?
whatever... i'm getting sick of this topic..

the lorentz factor is 1/sqrt(1-v^2/c^2). You multiply your rest mass by this factor to get your relativistic mass as you travel at some velocity v. For v small (like every day velocities, even airplanes), this factor is very very close to 1 so you don't notice any change. But you can see as v -> c, v^2/c^2 -> 1, and this means that you have sqrt(1-something close to 1) which is very close to 0. So as you approach c, you are dividing your rest mass by a number that gets closer and closer to 0, causing your relativistic mass to approach infinity.

 

[LRRockBox]

Hawking did a paper ( I think last year) determining the theoretical possibility of time travel. I'm sure you can dig it up, although understanding it might be a different matter (no pun intended).

Peter R.

 

[imported_jb]

oh ok. so the answer now is:
probably not, because we have mass.
-and if you did go that fast, you'd probably f* up the universe, with all that mass and energy.

 

[JediJeb]

One thing I have always wondered about come from the matter to energy equation where Energy derived from isotopic decay is equal to the mass destroyed times the square of the speed of light E=mc^2. If you have a nuclear reactor traveling near the speed of light the fuel would have infinite mass and also the mass destroyed would approach infinate mass therefore the energy evolved would approach infinity. Would that not theoretically provide the infinite energy needed to accelerate past the speed of light?

 

[silverpig]

Originally posted by: JediJeb
One thing I have always wondered about come from the matter to energy equation where Energy derived from isotopic decay is equal to the mass destroyed times the square of the speed of light E=mc^2. If you have a nuclear reactor traveling near the speed of light the fuel would have infinite mass and also the mass destroyed would approach infinate mass therefore the energy evolved would approach infinity. Would that not theoretically provide the infinite energy needed to accelerate past the speed of light?

Nice try... But no. Think of increasing mass as an energy battery. You put energy into something and it goes faster. After speeding up so much, it won't go any faster, but it's mass will increase. When you destroy this mass via e=mc^2 you don't contribute to making your ship go any faster, you just make it more massive. I'll do an approximation example here:

100 kg ship with 10 kg matter/antimatter fuel going at a very high fraction of c.
React the 10 kg of matter/antimatter and expel energy in photons out the back of the ship.
Because of mass increase you now have a 110 kg ship going at the same speed. (in reality it'll be a 109.xxxx kg ship going at your previous velocity plus a small bit). Of course this is really messy because i'm mixing masses from one frame with another, but i'm pressed for time right now so this'll have to suffice.

 

[Sk8orDie]

http://www.popsci.com/popsci/s...12543,211498-1,00.html <--- good article on time travel

1) as for the statement that if time travel was possible we would know about it because they would have come back here, this is my thinking. Humans only have a limited time on this earth, and by the time we figure out time travel, we'll probably have the ability to survive in some pretty harsh conditions, so what are the odds they would come back here and potentially screw things up? wouldn't they wanna go explore, so there's a possiblity they just wouldn't be interested in coming here.

2) as for not being able to instantaneously appear where other matter is, from what i've read, when you travel through time it's not instantaneous, your moving backward in time. Therefore, when you reach a point in time in the past you've "moved into it", giving the atoms time to move out of the way.


This is proabably all wrong as i'm studying business now and have no backround in physics or math, but it's just my two sense.

 

[mogulxlnc]

Greetings,

A beautiful dicussion going in here. I would like to add a note over here that what Quran says about time travel:

[In the Name of Allah, the Most Gracious, the Most Merciful.]

"Glory to [Allah] Who did take His servant for a Journey by night from the Sacred Mosque to the farthest Mosque, whose precincts We did bless,- in order that We might show him some of Our Signs: for He is the One Who heareth and seeth [all things]". [ Chapter 17. Isra', The Night Journey]

In the night of Ascension our Prophet Mohammad [Peace be upon him and his family] along with Archangel Gabriel [Jibraeel] visited Masjid Al Aqsa in [Palestine/Israel] than went for Masjid Al Haraam in Mecca [Saudi Arabia]. Than went for Heavens and beyond the Lote Tree of the Farthest boundry [Sidrat Al Muntahaa]. He met Almighty Allah in a place beyond time and imagination and came back to his home. All this in one night. Point to be noted that the chain of his door was still swinging and his ablution water was still there and his bed was still warm.

Allah did this in a fraction of time.This night is 27th of the month of Rajab in Islamic Calender.
We Muslims on these grounds believe that time travel has been made.

One more quote from Quran:

In the Name of Allah, the Most Beneficent, the Most Merciful
1. Verily, We sent it down in the night of al-Qadr.
2. And what will make you know what the night of al-Qadr is?
3. The night of al-Qadr is better than a thousand months.
4. Therein descend the angels and the Spirit [Archangel Gabriel] by their Lord's permission with all Decrees.
5. Peace! Until the appearance of dawn.

Here it is mentioned that Night of Al-Qadr [Night of Power] which can be any of the last odd nights of the Holy month of Ramadhan is better than a thousand months.

If you guyslook at this equation that Night of Power = 1000 months.
You can easilly calculate that how time becomes nearly frozen for a specific period of time.

I added this brief note just for the sake of discussion. Not for imposing my religious beliefs on anyone else.

Let the discussion Begin!

Farhan Zulfiqar Mughal

 

[imported_jb]

i refuse to beleive any mentions of time travel from a religion. any journeys, like those stated above, cannot be taken literally and must be written off to delusions of the human mind. i like to attribute stuff like that to ergot poisioning.

 

[DrPizza]

Hmmm...

Bizarre thought... I just put a bunch of things together in my head.. and came up with this:

IF time travel were possible - you're going to appear in some location in space. Wouldn't it be a good idea to not suddenly appear in the same location that, say a wall or a tree isn't in? Thus, travelling in time to a location on earth wouldn't be practical - no matter where you "landed", you'd have to worry about whatever bugs or pollution particles or air molecules or whatever was in your way.

SOOOooo, the best place to arrive at would be some place in space where the density of atoms is FAR lower than on or near the surface of the earth.


Now... ever notice that most of the alleged encounters with aliens aboard UFO's are humanoid in appearance? Maybe that's US, coming back in time... the UFO's are really just time machines

 

[TuxDave]

A thought that I just had. Assuming a single timeline, if a person goes back in time, he has to make sure he doesn't disturb anything to ensure that HIS timeline will continue undisturbed. If he alters anything that changes the situation, then he will be instantly obliterated. So MAYBE with that in mind, people HAVE been travelling back in time, but they purposely travel in a way such that we cannot detect nor interact with them. That way they can ensure that the timeline will be unaffected.

 

[Spinne]

If you want to know weather time-travel is possible, you need to see if solution to the General Relativity equations arise that permit time travel. The problem is that the GR equation is very very difficult to solve and currently there are only two exact solutions - the Schwarzschild metric and the Kerr metric. Both are solutions for isolated point-masses. All other theories apply approximations/simplifications to the equation to the point where it is solvable, often numerically. The problem is that sometimes the simplifications tend to be very exotic physically, so we can't be sure that the approximation/simplification physically possible to replicate by humans in the near future.

 

[Zero Plasma]

I didn't read all the posts so if someone allready said this please quote me to tell me. But it is thought possiable to travel to the future by taking say material the same mass of the planet Jupiter and using
it to construct around yourself(or someone builds it around you) an incredibly dense spherical shell whose
diameter is just a bit larger then the critical diameter needed for that mass to collapse to a black hole.
In Einstein's theory of gravity it shows that there would be no gravitational effects inside.
To not be killed while getting into the shell it would have to be very large.Then the forces being placed on the shell would be adjusted so it would slowly compress around you.You would be in a gravity well so to speak,
so photons traveling from you would have to fight against the gravity, thus losing energy so they would be
redshifted so they would have a longer wave length and time would pass more slowly then normal.
You would see time passing faster then normal becasue photons would be blueshifted.

The full idea can be found in a varity of books time on tavel or the internet.
But I do think it's a very interesting topic.

 

[silverpig]

Yeah Smoke0, that's possible, but unfortunatly the materials needed don't exist... I think you need something about 1/10th the mass of the sun in a 10 m radius.