Re: TIME warp

2011-06-07 Thread Felix Hoenikker
Hi guys,

Time travel is actually possible, as long as you are consistent (i.e.
Novikov self-consistency principle).  Please consider the argument for
it, beginning at:

http://www.reddit.com/r/askscience/comments/hr4x2/physicists_what_do_you_think_of_the_following/

Continue the discussion there at reddit if you would like.

Thank you!
F.H.


On Fri, Jun 3, 2011 at 12:09 PM, Travis Garrett
travis.garr...@gmail.com wrote:
 Hi Roc,

   Sure.  Let me go ahead and start by assuming that we need to exist
 in an environment that began in a state of low entropy (so that life
 can evolve during the increasing entropy phase - I could also
 examine this assumption, but that's another discussion...).  GR then
 does some interesting things.  First, gravity in GR couples to energy
 and momentum, and everything has energy and momentum, so, er, it
 couples to everything (binding them all together like the one ring I
 suppose).  It can thus essentially get everybody on the same page
 when things are starting out - forcing everybody (all the particle
 species) to pay attention and synchronize their behavior...

  GR can then do something quite cool.  If you feed the Einstein
 equations with a scalar field that happens to have much more potential
 energy than kinetic energy, then the spacetime responds by growing
 exponentially (i.e. the curvature is in the time direction - the
 spatial directions are driven to be very flat (i.e. the angles inside
 a triangle add up to 180 degrees), with the overall scale factor
 growing exponentially (i.e. the overall size of the triangle is
 growing exponentially in time)).  Thus, consider some complex universe
 with a lot of entropy.  Entropy is an extensive quantity, and thus if
 we consider some tiny volume element dV then there can't be much
 stuff inside dV, and therefore there is very little entropy inside
 dV.  If we can get a scalar field inside that dV to satisfy the
 condition that its potential energy is much larger than its kinetic
 energy, then blammo, we get inflation and that dV region can grow
 larger than our Hubble volume in a tiny fraction of a second (and then
 scalar field can decay, ending inflation, to be followed by a
 standard big bang...).

  It is by no means an open and shut case - there are lots of details
 to be filled in - but I think the overall picture makes a lot of
 sense...

    Sincerely,
           Travis

 On Jun 2, 6:35 am, Roc roc...@gmail.com wrote:
 nice answer.
 could you elaborate on this, though?

 Why then should spacetime be curved?  There are at least 2 good reasons:

 1) it allows for a big bang to happen, thus starting things off in a state

  of low entropy.

 thanks

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Re: TIME warp

2011-06-03 Thread Travis Garrett
Hi Roc,

   Sure.  Let me go ahead and start by assuming that we need to exist
in an environment that began in a state of low entropy (so that life
can evolve during the increasing entropy phase - I could also
examine this assumption, but that's another discussion...).  GR then
does some interesting things.  First, gravity in GR couples to energy
and momentum, and everything has energy and momentum, so, er, it
couples to everything (binding them all together like the one ring I
suppose).  It can thus essentially get everybody on the same page
when things are starting out - forcing everybody (all the particle
species) to pay attention and synchronize their behavior...

  GR can then do something quite cool.  If you feed the Einstein
equations with a scalar field that happens to have much more potential
energy than kinetic energy, then the spacetime responds by growing
exponentially (i.e. the curvature is in the time direction - the
spatial directions are driven to be very flat (i.e. the angles inside
a triangle add up to 180 degrees), with the overall scale factor
growing exponentially (i.e. the overall size of the triangle is
growing exponentially in time)).  Thus, consider some complex universe
with a lot of entropy.  Entropy is an extensive quantity, and thus if
we consider some tiny volume element dV then there can't be much
stuff inside dV, and therefore there is very little entropy inside
dV.  If we can get a scalar field inside that dV to satisfy the
condition that its potential energy is much larger than its kinetic
energy, then blammo, we get inflation and that dV region can grow
larger than our Hubble volume in a tiny fraction of a second (and then
scalar field can decay, ending inflation, to be followed by a
standard big bang...).

  It is by no means an open and shut case - there are lots of details
to be filled in - but I think the overall picture makes a lot of
sense...

Sincerely,
   Travis

On Jun 2, 6:35 am, Roc roc...@gmail.com wrote:
 nice answer.
 could you elaborate on this, though?

 Why then should spacetime be curved?  There are at least 2 good reasons:

 1) it allows for a big bang to happen, thus starting things off in a state

  of low entropy.

 thanks

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Re: TIME warp

2011-06-02 Thread Roc
nice answer.
could you elaborate on this, though?

Why then should spacetime be curved?  There are at least 2 good reasons:

1) it allows for a big bang to happen, thus starting things off in a state
 of low entropy.


thanks

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Re: TIME warp

2011-05-30 Thread Travis Garrett
Hi Selva,

   A straightforward and dry answer would be: it is a consequence of
the Einstein field equations of General Relativity (GR), and one
could then go on to do a derivation which demonstrates the time
dilation near a large dense mass.  The more interesting question
(which I think is what you are really getting at) is: Well, ok, fine,
but why do we exist in a universe which is governed by the equations
of GR?  I think the answer to this intriguing question lies in a
combination of (at least) three parts.

  The first is that GR includes Special Relativity (SR) as the limit
in flat spacetime (and also in small, local regions in curved
spacetime).  SR essentially stems from having an absolute speed limit
(in our case the speed of light), and an absolute speed limit is
useful because it makes causality well defined (e.g. the toddler
threw their juice on the floor because they weren't allowed any more
cookies, the dog then licks up the juice, the dog proceeds to pee on
the rug, etc. etc., the dad drives out to the beer store, etc.
etc...).  SR then links together space and time in a way which is
quite non-intuitive to us (which isn't too surprising since the speed
of light is so much faster than anything we deal with at the everyday
level) - so that for instance a clock moving past at high velocity
runs more slowly.

  As noted SR is then essentially embedded within the curved spacetime
of GR.  Why then should spacetime be curved?  There are at least 2
good reasons: 1) it allows for a big bang to happen, thus starting
things off in a state of low entropy.  And also: 2) GR includes
Newtonian gravity as the standard limiting case, which allows for very
long-lived orbits (in 3 spatial dimensions) as needed by biological
evolution to generate complex organisms.  And, now that I think about
it, eternal inflation (essentially preceding the big bang) allows for
viable effective field theories to be found among a landscape of
vacua, so that in total the big bang produces viable (~ Standard
Model) environments in an initial state of low entropy.

  I'd thus roughly guess that time dilation near massive bodies is
essentially a side effect of the equations that produce these other
vital effects... (althought conceivably there could also be some
reason for time dilation to be useful at some distant point in the
future...)

   Sincerely,
Travis

On May 29, 2:39 pm, selva selvakr1...@gmail.com wrote:
 why is there time dilation near a heavy mass ??

 On May 17, 12:31 am, selva selvakr1...@gmail.com wrote:



  hi everyone,

  can someone explain me what a time warp is ? or why there is a time
  warp ?
  well yes,it is due to the curvature of the space-time graph near a
  heavy mass.
  but how does it points to the center of the mass,how does it finds
  it..
  and explanation at atomic level plz..

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Re: TIME warp

2011-05-29 Thread selva kumar
i was not talking about going back in time..but slowing time..
it happens near a huge mass right ?


On Sun, May 22, 2011 at 8:32 PM, 1Z peterdjo...@yahoo.com wrote:



 On May 18, 12:56 pm, ronaldheld ronaldh...@gmail.com wrote:
  Are you talking about a Star Trek term or for certain space-times,
  the ability to go forwards or backwards in time relative to a distant
  observer?
 
  Ronald
 
  On May 16, 3:31 pm, selva selvakr1...@gmail.com wrote:
 
   hi everyone,
 
   can someone explain me what a time warp is ? or why there is a time
   warp ?
   well yes,it is due to the curvature of the space-time graph near a
   heavy mass.
   but how does it points to the center of the mass,how does it finds
   it..
   and explanation at atomic level plz..

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

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Re: TIME warp

2011-05-29 Thread selva
why is there time dilation near a heavy mass ??

On May 17, 12:31 am, selva selvakr1...@gmail.com wrote:
 hi everyone,

 can someone explain me what a time warp is ? or why there is a time
 warp ?
 well yes,it is due to the curvature of the space-time graph near a
 heavy mass.
 but how does it points to the center of the mass,how does it finds
 it..
 and explanation at atomic level plz..

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Re: TIME warp

2011-05-22 Thread 1Z


On May 18, 12:56 pm, ronaldheld ronaldh...@gmail.com wrote:
 Are you talking about a Star Trek term or for certain space-times,
 the ability to go forwards or backwards in time relative to a distant
 observer?

 Ronald

 On May 16, 3:31 pm, selva selvakr1...@gmail.com wrote:

  hi everyone,

  can someone explain me what a time warp is ? or why there is a time
  warp ?
  well yes,it is due to the curvature of the space-time graph near a
  heavy mass.
  but how does it points to the center of the mass,how does it finds
  it..
  and explanation at atomic level plz..

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

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Re: TIME warp

2011-05-18 Thread ronaldheld
Are you talking about a Star Trek term or for certain space-times,
the ability to go forwards or backwards in time relative to a distant
observer?
 
Ronald

On May 16, 3:31 pm, selva selvakr1...@gmail.com wrote:
 hi everyone,

 can someone explain me what a time warp is ? or why there is a time
 warp ?
 well yes,it is due to the curvature of the space-time graph near a
 heavy mass.
 but how does it points to the center of the mass,how does it finds
 it..
 and explanation at atomic level plz..

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