Time Travel.

• Maenad wrote on 2012-07-08 15:58
  Time travel to the future IS possible via time dilation. A hyperspeed 95% lightspeed train circling the Earth could very well be built and offered as a service.
  
  Observing the past is possible but very impractical. It requires teleportation via wormhole. The amount of years ago that you may observe is exactly equal to the number of light years away that you teleport. Impractical due to you needing a hypertelescope to observe any actual event in any detail at all.
• Drizzit wrote on 2012-07-10 01:43
  Given that time travel requires harnessing the energy of a black hole, it'll be a long time before we have to worry about it. By then, we might even have evolved enough to be responsible with it.
• Kueh wrote on 2012-07-10 01:48

  Quote from Araria;903708:

  A hyperspeed 95% lightspeed train circling the Earth could very well be built and offered as a service.

  
  
  I would object to this. Somehow supposing that you could manage to get the tremendous amounts of energy to propel the train in the first place (which you couldn't), the train would still have to fight the air molecules. Supposing you were willing to build it in an atmosphere of any sort, the immense friction would wreak havoc on both the train, and the surrounding area near the tracks.
  
  If at all, the train would have to be built in a vacuum.
• Odin wrote on 2012-07-10 21:30
  Theoretically if you built a time machine, and then stored it for a thousand years, you could then use that time machine successfully anywhere along that thousand year time period where the machine definately existed.
  
  But you still risk inducing Universe-destroying paradoxes doing this.
  
  It's better not to time travel at all. Just your very presence in an alternate time-space irreversibly alters that time-space from the quantum level up.
• Maenad wrote on 2012-07-13 07:50

  Quote from Kueh;904938:

  I would object to this. Somehow supposing that you could manage to get the tremendous amounts of energy to propel the train in the first place (which you couldn't), the train would still have to fight the air molecules. Supposing you were willing to build it in an atmosphere of any sort, the immense friction would wreak havoc on both the train, and the surrounding area near the tracks.
  
  If at all, the train would have to be built in a vacuum.

  
  
  Circling the Earth implies it would be above the atmosphere.
• Kueh wrote on 2012-07-13 08:21

  Quote from Araria;908201:

  Circling the Earth implies it would be above the atmosphere.

  
  
  It most certainly does not. Besides, how would you anchor the rails if they were free-floating in space? Without doing so, significant portions of the already massive amounts of energy that you're using to propel the train would also go into spinning the halo-like rails.
  
  The only way to really counteract it would be to make the rails very massive, or be attached to something massive, and that would defeat the purpose of building it around the earth specifically in the first place.
• Xemnas wrote on 2012-07-13 08:30
  I know it isn't possible, and I'm personally glad it isn't. One slight change in anything and everything we know now could be drastically changed or removed completely.
• RebeccaBlack wrote on 2012-07-13 08:46
  Change isn't necessarily a bad thing. There's no way the past is perfect and had a completely positive effect on everything.
• Maenad wrote on 2012-07-13 09:29

  Quote from Kueh;908230:

  It most certainly does not. Besides, how would you anchor the rails if they were free-floating in space? Without doing so, significant portions of the already massive amounts of energy that you're using to propel the train would also go into spinning the halo-like rails.
  
  The only way to really counteract it would be to make the rails very massive, or be attached to something massive, and that would defeat the purpose of building it around the earth specifically in the first place.

  
  
  First we have to build the very first fusion reactor before we can start talking about energy costs.
• Kueh wrote on 2012-07-13 09:36

  Quote from Araria;908271:

  First we have to build the very first fusion reactor before we can start talking about energy costs.

  
  
  A hundred million fusion reactors operating at 100% efficiency would consume enough fuel for a hundred earths and still not be able to propel an apple at 50% the speed of light for 100 years. Let alone a train full of people at 98%.
• Retard wrote on 2012-07-19 10:28
  I just want to be able to relive past great experiences...
  
  But i guess daydreaming and dreaming is enough too...
• Conor wrote on 2012-07-19 17:14
  I don't think it's possible due to the whole time and space not being linear thing.