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Interstellar Travel and time taken for the trip. (No time dilation for the Earth)

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  Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-01 03:25 -0700
    Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Dirk Van de moortel <dirkvandemoortel@hotspam.not> - 2017-09-01 13:23 +0200
    Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) "Paul B. Andersen" <relativity@paulba.no> - 2017-09-01 14:15 +0200
      Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) mlwozniak@wp.pl - 2017-09-01 06:09 -0700
    Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) rotchm <rotchm@gmail.com> - 2017-09-01 06:20 -0700
      Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) mlwozniak@wp.pl - 2017-09-01 07:05 -0700
      Re: Interstellar Travel and time taken for the trip. (No time  dilation for the Earth) The Starmaker <starmaker@ix.netcom.com> - 2017-09-01 12:40 -0700
        Re: Interstellar Travel and time taken for the trip. (No time   dilation for the Earth) The Starmaker <starmaker@ix.netcom.com> - 2017-09-02 12:19 -0700
    Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Odd Bodkin <bodkinodd@gmail.com> - 2017-09-01 19:37 +0000
    Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-02 03:26 +0200
      Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) xxein1x1@gmail.com - 2017-09-02 22:34 -0700
        Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) xxein1x1@gmail.com - 2017-09-02 22:48 -0700
        Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-03 10:18 +0200
          Energy (was: Interstellar Travel and time taken for the trip. (No time dilation for the Earth)) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-03 15:52 +0200
            Re: Energy (was: Interstellar Travel and time taken for the trip. (No time dilation for the Earth)) Ethel Ocallaghan <unlgclo@awlwaac.ag> - 2017-09-03 13:56 +0000
              The problem of crackpots (was: Energy) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-03 17:32 +0200
      Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-03 18:43 -0700
        Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-03 18:55 -0700
          Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-03 19:03 -0700
            Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-05 08:22 +0200
              Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) mlwozniak@wp.pl - 2017-09-04 23:32 -0700
              Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-05 04:11 -0700
                Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Gary Harnagel <hitlong@yahoo.com> - 2017-09-05 05:06 -0700
                  Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) mlwozniak@wp.pl - 2017-09-05 05:17 -0700
                    Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Gary Harnagel <hitlong@yahoo.com> - 2017-09-05 05:26 -0700
                      Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Istrátora Metiku <untw@nwpovu.un> - 2017-09-06 12:42 +0000
                  Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-05 22:11 -0700
                Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-05 14:33 +0200
                  Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-06 00:33 +0200
                    Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-05 22:48 -0700
                    Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Istrátora Metiku <untw@nwpovu.un> - 2017-09-06 13:03 +0000
                  Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-05 22:46 -0700
                    Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-06 13:04 +0200
                      Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-06 05:05 -0700
                        Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) mlwozniak@wp.pl - 2017-09-06 05:25 -0700
                        Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-07 02:10 +0200
                          Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-06 20:40 -0700
                            Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-07 13:15 +0200
                              Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) mlwozniak@wp.pl - 2017-09-07 05:42 -0700
                              Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-07 21:56 -0700
                              Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-07 21:58 -0700
          Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-05 07:57 +0200
            Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) mlwozniak@wp.pl - 2017-09-04 23:19 -0700
              Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-05 03:38 -0700
                Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) mlwozniak@wp.pl - 2017-09-05 04:52 -0700
                  Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-05 22:08 -0700
            Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-05 03:58 -0700
              Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-05 14:22 +0200
            Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-05 14:03 +0200
          Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-05 08:26 +0200
            Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-05 04:12 -0700
        Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-04 06:42 +0200
          Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-04 05:35 -0700
            Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-04 21:49 +0200
              Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-04 19:35 -0700
                Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-05 07:41 +0200
                  Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-05 03:53 -0700
                    Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-05 14:15 +0200
                      Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-05 22:17 -0700
                        Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-06 12:44 +0200
                          Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-06 05:19 -0700
                            Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-06 15:34 +0200
                              Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-06 08:53 -0700
                                Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-06 18:02 +0200
                                  Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-06 21:02 -0700
                                    Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-07 11:31 +0200
                                      Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Erika Milling <kak@kiilwgil.lc> - 2017-09-07 15:46 +0000
                                      Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-07 21:44 -0700
                            Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-06 16:01 +0200
                              Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) mlwozniak@wp.pl - 2017-09-06 07:11 -0700
                              Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-06 08:57 -0700
                                Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-06 09:01 -0700
                                  Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-07 02:25 +0200
                                    Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-06 20:49 -0700
                                      Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-07 11:42 +0200
                                    Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) mlwozniak@wp.pl - 2017-09-07 01:23 -0700
                                      Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-07 02:01 -0700
                                Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Odd Bodkin <bodkinodd@gmail.com> - 2017-09-06 12:56 -0500
                                  Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) mlwozniak@wp.pl - 2017-09-06 12:44 -0700
                                  Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-06 20:36 -0700
                                    Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-07 12:04 +0200
                                    Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Odd Bodkin <bodkinodd@gmail.com> - 2017-09-07 12:14 +0000
                                Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-09-06 20:12 +0200
    Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) bigal95210@gmail.com - 2017-09-05 15:48 -0700
      Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) gehan.ameresekere@gmail.com - 2017-09-05 22:49 -0700
        Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) "Dono," <sa_ge@comcast.net> - 2017-09-07 07:32 -0700

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#430648 — Interstellar Travel and time taken for the trip. (No time dilation for the Earth)

In this recent talk on interstellar travel, Ryan Weed talks about interstellar travel using anti-matter propulsion.

https://www.youtube.com/watch?v=EBebWBjpWIQ

http://www.wired.co.uk/article/ryan-weed-wired-2015

Curiously, he ends with the suggestion that long distance travel would not be so attractive because the traveler will be returning to an Earth that exists far in the future.

But this cannot be. Imagine a ray of light or a beam of light sent to the moon and back, to a reflector on the moon. The time taken from the sending of the beam to its return will be around 1.3 seconds each way.

Extend this to light sent to a planet 10 light years away, and it takes 10 years for the outbound trip and 10 years for the return trip, as measured by 'clocks and trees on Earth'.

Any spacecraft, probe, robot, anything that goes out to that planet at the speed of light and comes back will be back in 20 years time.  If not travelling at the speed of light, it will go out and return in a specific time frame, for example at half the speed of light it will take double the time. 

Now where is the time dilation in that?

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#430656

Op 01-sep-2017 om 12:25 schreef gehan.ameresekere@gmail.com:
> In this recent talk on interstellar travel, Ryan Weed talks about
> interstellar travel using anti-matter propulsion.
> 
> https://www.youtube.com/watch?v=EBebWBjpWIQ
> 
> http://www.wired.co.uk/article/ryan-weed-wired-2015
> 
> Curiously, he ends with the suggestion that long distance travel
> would not be so attractive because the traveler will be returning to
> an Earth that exists far in the future.
> 
> But this cannot be. Imagine a ray of light or a beam of light sent to
> the moon and back, to a reflector on the moon. The time taken from
> the sending of the beam to its return will be around 1.3 seconds each
> way.
> 
> Extend this to light sent to a planet 10 light years away, and it
> takes 10 years for the outbound trip and 10 years for the return
> trip, as measured by 'clocks and trees on Earth'.
> 
> Any spacecraft, probe, robot, anything that goes out to that planet
> at the speed of light and comes back will be back in 20 years time.
> If not travelling at the speed of light, it will go out and return in
> a specific time frame, for example at half the speed of light it will
> take double the time.
> 
> Now where is the time dilation in that?

For the traveller, the distance covered is less than 10
light years, so they will need less than 20 years to
get there and return home.
See https://en.wikipedia.org/wiki/Length_contraction

Dirk Vdm

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#430659

Den 01.09.2017 12.25, skrev gehan.ameresekere@gmail.com:
> In this recent talk on interstellar travel, Ryan Weed talks about interstellar travel using anti-matter propulsion.
> 
> https://www.youtube.com/watch?v=EBebWBjpWIQ
> 
> http://www.wired.co.uk/article/ryan-weed-wired-2015
> 
> Curiously, he ends with the suggestion that long distance travel would not be so attractive because the traveler will be returning to an Earth that exists far in the future.
> 
> But this cannot be. Imagine a ray of light or a beam of light sent to the moon and back, to a reflector on the moon. The time taken from the sending of the beam to its return will be around 1.3 seconds each way.
> 
> Extend this to light sent to a planet 10 light years away, and it takes 10 years for the outbound trip and 10 years for the return trip, as measured by 'clocks and trees on Earth'.

And as measured by the travelling photon the duration of
the journey was zero.
> 
> Any spacecraft, probe, robot, anything that goes out to that planet at the speed of light and comes back will be back in 20 years time.  If not travelling at the speed of light, it will go out and return in a specific time frame, for example at half the speed of light it will take double the time.
> 
> Now where is the time dilation in that?
> 

A clock in the travelling spacecraft will show that the duration
of the journey is less than what the clock on the Earth shows.

https://paulba.no/pdf/TwinsByMetric.pdf
https://paulba.no/twins.html

-- 
Paul

https://paulba.no/

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#430666

W dniu piątek, 1 września 2017 14:15:41 UTC+2 użytkownik Paul B. Andersen napisał:
> A clock in the travelling spacecraft will show that the duration
> of the journey is less than what the clock on the Earth shows.

A lie, as expected from fanatic trash. It's not just a theory anymore, 
we have GPS.

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#430667

On Friday, September 1, 2017 at 6:25:36 AM UTC-4, gehan.am...@gmail.com wrote:

> Curiously, he ends with the suggestion that long distance 
> travel would not be so attractive because the traveler will 
> be returning to an Earth that exists far in the future.
> 
> But this cannot be. 

When you leave your place in the morning & you come back to it later in the evening, you arrive there "in the future"; You left at 8 am and reappeared there at 5 pm. it does happen!


> Any spacecraft, probe, robot, anything that goes out to that 
> planet at the speed of light and comes back will be back in 
> 20 years time.  If not travelling at the speed of light, it 
> will go out and return in a specific time frame, ...
>
> Now where is the time dilation in that?

It is there but you just left it out. 
WRT earth, its a 20 yr trip. But wrt the traveler (his wristwatch), it
indicates but 17 yrs, say.  

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#430670

W dniu piątek, 1 września 2017 15:20:58 UTC+2 użytkownik rotchm napisał:

> It is there but you just left it out. 
> WRT earth, its a 20 yr trip. But wrt the traveler (his wristwatch), it
> indicates but 17 yrs, say.

Well, it can happen; but it would only mean that the traveller
should take his wristwatch and put it into a trash can, where it 
belongs.
If you were not too stupid to take a look at "year" dictionary
definition you would know how your idiot guru fooled himself.

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#430716 — Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth)

rotchm wrote:
> 
> On Friday, September 1, 2017 at 6:25:36 AM UTC-4, gehan.am...@gmail.com wrote:
> 
> > Curiously, he ends with the suggestion that long distance
> > travel would not be so attractive because the traveler will
> > be returning to an Earth that exists far in the future.
> >
> > But this cannot be.
> 
> When you leave your place in the morning & you come back to it later in the evening, you arrive there "in the future"; You left at 8 am and reappeared there at 5 pm. it does happen!
> 
>


You wake up in the morning
and you're back in the past again...

or, you never arrived  "in the future".


morning and evening are both the same place.


Where is the future?

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#430843 — Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth)

The Starmaker wrote:
> 
> rotchm wrote:
> >
> > On Friday, September 1, 2017 at 6:25:36 AM UTC-4, gehan.am...@gmail.com wrote:
> >
> > > Curiously, he ends with the suggestion that long distance
> > > travel would not be so attractive because the traveler will
> > > be returning to an Earth that exists far in the future.
> > >
> > > But this cannot be.
> >
> > When you leave your place in the morning & you come back to it later in the evening, you arrive there "in the future"; You left at 8 am and reappeared there at 5 pm. it does happen!
> >
> >
> 
> You wake up in the morning
> and you're back in the past again...
> 
> or, you never arrived  "in the future".
> 
> morning and evening are both the same place.
> 
> Where is the future?



There is only the ...Now.

Not the Here, the Now.

The Here is overthere...

the Now is overhere.

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#430713

<gehan.ameresekere@gmail.com> wrote:
> In this recent talk on interstellar travel, Ryan Weed talks about
> interstellar travel using anti-matter propulsion.
> 
> https://www.youtube.com/watch?v=EBebWBjpWIQ
> 
> http://www.wired.co.uk/article/ryan-weed-wired-2015
> 
> Curiously, he ends with the suggestion that long distance travel would
> not be so attractive because the traveler will be returning to an Earth
> that exists far in the future.
> 
> But this cannot be. Imagine a ray of light or a beam of light sent to the
> moon and back, to a reflector on the moon. The time taken from the
> sending of the beam to its return will be around 1.3 seconds each way.
> 
> Extend this to light sent to a planet 10 light years away, and it takes
> 10 years for the outbound trip and 10 years for the return trip, as
> measured by 'clocks and trees on Earth'.
> 
> Any spacecraft, probe, robot, anything that goes out to that planet at
> the speed of light and comes back will be back in 20 years time.  If not
> travelling at the speed of light, it will go out and return in a specific
> time frame, for example at half the speed of light it will take double the time. 
> 
> Now where is the time dilation in that?
> 

Two comments. 

No material object can be sent anywhere at the speed of light. 
All the times you mentioned are earth times, not traveler times. 

-- 
Odd Bodkin -- maker of fine toys, tools, tables

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#430783

gehan.ameresekere@gmail.com wrote:

> Extend this to light sent to a planet 10 light years away, and it takes 10
> years for the outbound trip and 10 years for the return trip, as measured
> by 'clocks and trees on Earth'.
> 
> Any spacecraft, probe, robot, anything that goes out to that planet at the
> speed of light and comes back will be back in 20 years time. 

No “spacecraft, probe, robot, anything” *that has non-zero mass* can “go out 
to that planet at the speed of light (relative to Earth)”.

(The magnitude of) its momentum is

  p = γ m v

  γ = 1∕√(1 − v²∕c²),

where m is the object’s mass, and v is its relative speed.

The limit of the momentum that would have to be imparted to it in order to 
go from relative speed zero to the speed of light, would be, in the Earth 
rest frame:

  lim p = lim  m v∕√(1 − v²∕c²) = +∞.
  v→c     v→c

You could also say that the object’s total energy is

   E = E₀ + Eₖ = γ m c²

with the rest energy

  E₀ = m c².

Its kinetic energy Eₖ is therefore

  Eₖ = E − E₀ = γ m c² − m c² = m c² (γ − 1).

The limit of the kinetic energy that would have to be transferred to it in 
order for it to go from relative speed zero to the speed of light, would be

  lim Eₖ = lim m c² (1∕√(1 − v²∕c²) − 1) = +∞.
  v→c      v→c

    [With regard to at-light or faster-than-light interstellar travel, as 
     you mentioned it, that does not mean that it is physically impossible.  
     For example, the Alcubierre warp drive, for example, works by 
     contracting space in front of the spaceship (based on general 
     relativity), so that the spaceship never really travels at high 
     relative speeds.  It would only have an *apparent* speed that is or is
     faster than the speed of light.  This would also solve the problem of
     involuntary time travel to the distant future.  Unfortunately, although
     the energy requirements could be reduced considerably in the meantime,
     the required negative energy for the warp is still hard to come by.]

> If not travelling at the speed of light, it will go out and return in a 
> specific time frame, for example at half the speed of light it will take
> double the time.

For the earthbound observer.  Not for the traveler, because the traveler is 
not traveling 10 light-years to that planet, but for them *the planet* is 
traveling *to them* and *away from them* *less than 10 light-years* (length 
contraction) …
 
> Now where is the time dilation in that?

… therefore, their clocks will not have advanced as much as the earthbound 
observer’s during either part of the journey.

When they meet again, the earthbound observer must interpret that as that 
the traveler’s clocks have been running slower than their own during the 
journey (time dilation).

And the (former) traveler has to conclude that they have also traveled into 
the future (although without an earthbound clock/calendar/etc. to look at, 
they might not realize that immediately¹).

The more interesting question here is why the traveler does not also observe 
the earthbound observer’s clock having advanced less than their own.  
Because that cannot be explained with either time dilation or length 
contraction (but it can be explained consistently within special 
relativity).

This is a standard problem; google “"twin paradox"”.

I would consider the aforementioned knowledge to be special relativity 
*basics*.

HTH

_________________
¹  Scientifically correct in that regard, that is the premise of
   <spoiler code="rot13">“Cynarg bs gur Ncrf”</spoiler>, among
   similar science-fiction stories.
-- 
PointedEars

Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.

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#430889

On Friday, September 1, 2017 at 9:27:00 PM UTC-4, Thomas 'PointedEars' Lahn wrote:
> gehan.ameresekere@gmail.com wrote:
> 
> > Extend this to light sent to a planet 10 light years away, and it takes 10
> > years for the outbound trip and 10 years for the return trip, as measured
> > by 'clocks and trees on Earth'.
> > 
> > Any spacecraft, probe, robot, anything that goes out to that planet at the
> > speed of light and comes back will be back in 20 years time. 
> 
> No “spacecraft, probe, robot, anything” *that has non-zero mass* can “go out 
> to that planet at the speed of light (relative to Earth)”.
> 
> (The magnitude of) its momentum is
> 
>   p = γ m v
> 
>   γ = 1∕√(1 − v²∕c²),
> 
> where m is the object’s mass, and v is its relative speed.
> 
> The limit of the momentum that would have to be imparted to it in order to 
> go from relative speed zero to the speed of light, would be, in the Earth 
> rest frame:
> 
>   lim p = lim  m v∕√(1 − v²∕c²) = +∞.
>   v→c     v→c
> 
> You could also say that the object’s total energy is
> 
>    E = E₀ + Eₖ = γ m c²
> 
> with the rest energy
> 
>   E₀ = m c².
> 
> Its kinetic energy Eₖ is therefore
> 
>   Eₖ = E − E₀ = γ m c² − m c² = m c² (γ − 1).
> 
> The limit of the kinetic energy that would have to be transferred to it in 
> order for it to go from relative speed zero to the speed of light, would be
> 
>   lim Eₖ = lim m c² (1∕√(1 − v²∕c²) − 1) = +∞.
>   v→c      v→c
> 
>     [With regard to at-light or faster-than-light interstellar travel, as 
>      you mentioned it, that does not mean that it is physically impossible.  
>      For example, the Alcubierre warp drive, for example, works by 
>      contracting space in front of the spaceship (based on general 
>      relativity), so that the spaceship never really travels at high 
>      relative speeds.  It would only have an *apparent* speed that is or is
>      faster than the speed of light.  This would also solve the problem of
>      involuntary time travel to the distant future.  Unfortunately, although
>      the energy requirements could be reduced considerably in the meantime,
>      the required negative energy for the warp is still hard to come by.]
> 
> > If not travelling at the speed of light, it will go out and return in a 
> > specific time frame, for example at half the speed of light it will take
> > double the time.
> 
> For the earthbound observer.  Not for the traveler, because the traveler is 
> not traveling 10 light-years to that planet, but for them *the planet* is 
> traveling *to them* and *away from them* *less than 10 light-years* (length 
> contraction) …
>  
> > Now where is the time dilation in that?
> 
> … therefore, their clocks will not have advanced as much as the earthbound 
> observer’s during either part of the journey.
> 
> When they meet again, the earthbound observer must interpret that as that 
> the traveler’s clocks have been running slower than their own during the 
> journey (time dilation).
> 
> And the (former) traveler has to conclude that they have also traveled into 
> the future (although without an earthbound clock/calendar/etc. to look at, 
> they might not realize that immediately¹).
> 
> The more interesting question here is why the traveler does not also observe 
> the earthbound observer’s clock having advanced less than their own.  
> Because that cannot be explained with either time dilation or length 
> contraction (but it can be explained consistently within special 
> relativity).
> 
> This is a standard problem; google “"twin paradox"”.
> 
> I would consider the aforementioned knowledge to be special relativity 
> *basics*.
> 
> HTH
> 
> _________________
> ¹  Scientifically correct in that regard, that is the premise of
>    <spoiler code="rot13">“Cynarg bs gur Ncrf”</spoiler>, among
>    similar science-fiction stories.
> -- 
> PointedEars
> 
> Twitter: @PointedEars2
> Please do not cc me. / Bitte keine Kopien per E-Mail.

xxein:  Just when I thought you were sensible, you spout hogwash.

With regard to an Alcubierre warp drive or whatever, it can't work like that.  Either Einstein's meanings are misinterpreted, he's nuts or the whole idea is concocted out of fairy dust.  If you approached me at such speed, would my space contort?  Would I notice my star field contorting just because of your journey?  How far would such an effect extend?  Forget about energy requirements.  Ptooey!

Length contraction of space?  Whether LC is physical or geometric projection, it is only valid for the moving object - not any surrounding space.  Again Einsteinian-like fantasy.

Purely speaking, we know that a moving clock beats slower than a stationary one.  Forget relative speeds.  Because the functions are non-linear wrt speed and clocks, relative speeds wont work.  Only absolute speeds wrt to absolute light speed can.  And don't go to the extension that all observers measure c as val(c) because that too is misleading.  The magic word here is "measured" and that is a washout because time dilation and length contraction go hand in hand so that the moving observer always measures c to be val(c) with his moving sticks and clocks.

Relative and subjective time is what a clock measures - not absolute time.  Absolute time is beyond even being stationary wrt light's speed because light has no constant speed in the universe.  Rather, light is subject to gravity (bent, pushed and pulled) just like anything else.  It goes into considering a light medium or, as I believe, a moving ether that controls all movement - universal expansion, inflation, and all matter movement.  Sadly, we can see the effects but we cannot detect the cause.  Even worse, we misidentify "empty" space as being empty.  To say a truly empty space is expanding would be like saying a nothing is expanding which is why there must be an *ether* in this universe (and all universes unto themselves in a similar manner).  When I say all universes, I mean even the oniony ones, green ones, hard and soft ones, flaky ones, smooth ones, curly ones, smirky ones, sczerl ones, mxyzptlk ones, myxplt ones like ours, meaningless ones, nonexistent ones and the various others beyond any categorization of any type.  We just don't know - and prove it throughout any time.

A little lighthearted in an unknown existence, but us nonetheless.

Btw, energy is just our way of quantifying an existence of or change of action.

Have a happy one.  Good day.

[toc] | [prev] | [next] | [standalone]

#430890

On Sunday, September 3, 2017 at 1:34:26 AM UTC-4, xxei...@gmail.com wrote:
> On Friday, September 1, 2017 at 9:27:00 PM UTC-4, Thomas 'PointedEars' Lahn wrote:
> > gehan.ameresekere@gmail.com wrote:
> > 
> > > Extend this to light sent to a planet 10 light years away, and it takes 10
> > > years for the outbound trip and 10 years for the return trip, as measured
> > > by 'clocks and trees on Earth'.
> > > 
> > > Any spacecraft, probe, robot, anything that goes out to that planet at the
> > > speed of light and comes back will be back in 20 years time. 
> > 
> > No “spacecraft, probe, robot, anything” *that has non-zero mass* can “go out 
> > to that planet at the speed of light (relative to Earth)”.
> > 
> > (The magnitude of) its momentum is
> > 
> >   p = γ m v
> > 
> >   γ = 1∕√(1 − v²∕c²),
> > 
> > where m is the object’s mass, and v is its relative speed.
> > 
> > The limit of the momentum that would have to be imparted to it in order to 
> > go from relative speed zero to the speed of light, would be, in the Earth 
> > rest frame:
> > 
> >   lim p = lim  m v∕√(1 − v²∕c²) = +∞.
> >   v→c     v→c
> > 
> > You could also say that the object’s total energy is
> > 
> >    E = E₀ + Eₖ = γ m c²
> > 
> > with the rest energy
> > 
> >   E₀ = m c².
> > 
> > Its kinetic energy Eₖ is therefore
> > 
> >   Eₖ = E − E₀ = γ m c² − m c² = m c² (γ − 1).
> > 
> > The limit of the kinetic energy that would have to be transferred to it in 
> > order for it to go from relative speed zero to the speed of light, would be
> > 
> >   lim Eₖ = lim m c² (1∕√(1 − v²∕c²) − 1) = +∞.
> >   v→c      v→c
> > 
> >     [With regard to at-light or faster-than-light interstellar travel, as 
> >      you mentioned it, that does not mean that it is physically impossible.  
> >      For example, the Alcubierre warp drive, for example, works by 
> >      contracting space in front of the spaceship (based on general 
> >      relativity), so that the spaceship never really travels at high 
> >      relative speeds.  It would only have an *apparent* speed that is or is
> >      faster than the speed of light.  This would also solve the problem of
> >      involuntary time travel to the distant future.  Unfortunately, although
> >      the energy requirements could be reduced considerably in the meantime,
> >      the required negative energy for the warp is still hard to come by.]
> > 
> > > If not travelling at the speed of light, it will go out and return in a 
> > > specific time frame, for example at half the speed of light it will take
> > > double the time.
> > 
> > For the earthbound observer.  Not for the traveler, because the traveler is 
> > not traveling 10 light-years to that planet, but for them *the planet* is 
> > traveling *to them* and *away from them* *less than 10 light-years* (length 
> > contraction) …
> >  
> > > Now where is the time dilation in that?
> > 
> > … therefore, their clocks will not have advanced as much as the earthbound 
> > observer’s during either part of the journey.
> > 
> > When they meet again, the earthbound observer must interpret that as that 
> > the traveler’s clocks have been running slower than their own during the 
> > journey (time dilation).
> > 
> > And the (former) traveler has to conclude that they have also traveled into 
> > the future (although without an earthbound clock/calendar/etc. to look at, 
> > they might not realize that immediately¹).
> > 
> > The more interesting question here is why the traveler does not also observe 
> > the earthbound observer’s clock having advanced less than their own.  
> > Because that cannot be explained with either time dilation or length 
> > contraction (but it can be explained consistently within special 
> > relativity).
> > 
> > This is a standard problem; google “"twin paradox"”.
> > 
> > I would consider the aforementioned knowledge to be special relativity 
> > *basics*.
> > 
> > HTH
> > 
> > _________________
> > ¹  Scientifically correct in that regard, that is the premise of
> >    <spoiler code="rot13">“Cynarg bs gur Ncrf”</spoiler>, among
> >    similar science-fiction stories.
> > -- 
> > PointedEars
> > 
> > Twitter: @PointedEars2
> > Please do not cc me. / Bitte keine Kopien per E-Mail.
> 
> xxein:  Just when I thought you were sensible, you spout hogwash.
> 
> With regard to an Alcubierre warp drive or whatever, it can't work like that.  Either Einstein's meanings are misinterpreted, he's nuts or the whole idea is concocted out of fairy dust.  If you approached me at such speed, would my space contort?  Would I notice my star field contorting just because of your journey?  How far would such an effect extend?  Forget about energy requirements.  Ptooey!
> 
> Length contraction of space?  Whether LC is physical or geometric projection, it is only valid for the moving object - not any surrounding space.  Again Einsteinian-like fantasy.
> 
> Purely speaking, we know that a moving clock beats slower than a stationary one.  Forget relative speeds.  Because the functions are non-linear wrt speed and clocks, relative speeds wont work.  Only absolute speeds wrt to absolute light speed can.  And don't go to the extension that all observers measure c as val(c) because that too is misleading.  The magic word here is "measured" and that is a washout because time dilation and length contraction go hand in hand so that the moving observer always measures c to be val(c) with his moving sticks and clocks.
> 
> Relative and subjective time is what a clock measures - not absolute time.  Absolute time is beyond even being stationary wrt light's speed because light has no constant speed in the universe.  Rather, light is subject to gravity (bent, pushed and pulled) just like anything else.  It goes into considering a light medium or, as I believe, a moving ether that controls all movement - universal expansion, inflation, and all matter movement.  Sadly, we can see the effects but we cannot detect the cause.  Even worse, we misidentify "empty" space as being empty.  To say a truly empty space is expanding would be like saying a nothing is expanding which is why there must be an *ether* in this universe (and all universes unto themselves in a similar manner).  When I say all universes, I mean even the oniony ones, green ones, hard and soft ones, flaky ones, smooth ones, curly ones, smirky ones, sczerl ones, mxyzptlk ones, myxplt ones like ours, meaningless ones, nonexistent ones and the various others beyond any categorization of any type.  We just don't know - and prove it throughout any time.
> 
> A little lighthearted in an unknown existence, but us nonetheless.
> 
> Btw, energy is just our way of quantifying an existence of or change of action.
> 
> Have a happy one.  Good day.

xxein:  It is fun pretending to know, is it not?  Too bad for us.

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#430896

xxein1x1@gmail.com wrote:

> On Friday, September 1, 2017 at 9:27:00 PM UTC-4, Thomas 'PointedEars'
> Lahn wrote:

Attribution line, not attribution novel.

> [50+ lines of uncommented quotes]

Good grief.

>> The limit of the kinetic energy that would have to be transferred to
>> [a massive object] in order for it to go from relative speed zero to
>> the speed of light, would be
>> 
>>   lim Eₖ = lim m c² (1∕√(1 − v²∕c²) − 1) = +∞.
>>   v→c      v→c
>> 
>>     [With regard to at-light or faster-than-light interstellar travel, as
>>      you mentioned it, that does not mean that it is physically
>>      impossible. For example, the Alcubierre warp drive, for example,
>>      works by contracting space in front of the spaceship (based on
>>      general relativity), so that the spaceship never really travels at
>>      high relative speeds.  It would only have an *apparent* speed that 
>>      is or is faster than the speed of light.  This would also solve the
>>      problem of involuntary time travel to the distant future. 
>>      Unfortunately, although the energy requirements could be reduced
>>      considerably in the meantime, the required negative energy for the
>>      warp is still hard to come by.]
>> 
>> […]
> 
> xxein:  Just when I thought you were sensible, you spout hogwash.

That does not mean much to me coming from a pseudonymous Googlodyte who 
cannot even quote/post properly (despite being told several times how to 
post correctly to Usenet).

> With regard to an Alcubierre warp drive or whatever, it can't work like
> that.

  “They said warp speed could not be achieved.”

    —Sybok in “Star Trek Ⅴ: The Final Frontier” (Paramount Pictures, 1989)

SCNR ;-)

> Either Einstein's meanings are misinterpreted, he's nuts or the
> whole idea is concocted out of fairy dust.

Please read <https://en.wikipedia.org/wiki/Alcubierre_drive> and do not make 
mention of it again until you did.

> If you approached me at such speed, would my space contort?

With any way of FTL travel, I would not really approach you at FTL speed; 
AISB, it is only an *apparent* speed.

> Would I notice my star field contorting just because of your journey? 

(Interesting question.)  No, I don’t think so.  If I could use a warp ship, 
and

  (a) your location would be along and close to its path, you would not 
      notice anything.  The same as you are not noticing that you are
      sitting in a region of curved spacetime right now.  Spacetime is
      *locally* flat.  (Therefore, locally, special relativity suffices.)

  (b) your location would be near the end of its path, it would suddenly 
      appear to you, its length appearing stretched over the distance that
      I travelled (several light-years), then quickly restored to normal
      proportions as I “get out of warp”™.

But you might not survive my arrival because I am carrying with me a bunch 
of relativistic particles.

Probably I should not use “warp drive”™ within your star system ;-)

> How far would such an effect extend?

That depends on the “warp factor”™.

Maybe we need to impose a “warp speed limit”™ ;-)

> Length contraction of space?

No, you are confusing special with general relativity.

> [pseudo-scientific word salad]
> 
> energy is just our way of quantifying an existence of or change of action.

The latter is true: E = −∂S∕∂t.  It is the relation that helps to derive the 
four-momentum and the energy–momentum relation from that:

<https://en.wikipedia.org/wiki/Four-momentum#Derivation>

-- 
PointedEars

Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.

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#430915 — Energy (was: Interstellar Travel and time taken for the trip. (No time dilation for the Earth))

Thomas 'PointedEars' Lahn wrote:

> xxein1x1@gmail.com wrote:
>> energy is just our way of quantifying an existence of or change of
>> action.
> 
> The latter is true: E = −∂S∕∂t.  It is the relation that helps to derive
> the four-momentum and the energy–momentum relation from that:
> 
> <https://en.wikipedia.org/wiki/Four-momentum#Derivation>

I would like to add that the discussed statement is only *partially* true 
because of the exclusive “just” (“only”) in there.

The action principle, for example in Lagrangian mechanics (where the action 
is defined as S = ∫_{t₁}^{t₂} L dt, where t₂ > t₁ are times, and L is the 
Lagrangian) is *only one of several equivalent ways* of looking at it in 
physics, as Richard P. Feynman explains so beautifully in his second 
“Messenger” lecture “The Character of Physical Law: The Relation of 
Mathematics and Physics” (Cornell University, 1964):

<https://www.microsoft.com/en-us/research/project/tuva-richard-feynman/>
<http://www.cornell.edu/video/playlist/richard-feynman-messenger-lectures>
<https://youtu.be/kd0xTfdt6qw>        (that particular lecture)
<https://youtu.be/kd0xTfdt6qw?t=1986> (that particular discussion)

See also: <https://en.wikipedia.org/wiki/Energy#Scientific_use>

-- 
PointedEars

Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.

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#430916 — Re: Energy (was: Interstellar Travel and time taken for the trip. (No time dilation for the Earth))

Thomas 'PointedEars' Lahn wrote:

>> xxein1x1@gmail.com wrote:
>>> energy is just our way of quantifying an existence of or change of
>>> action.
>> 
>> The latter is true: E = −∂S∕∂t.  It is the relation that helps to
>> derive the four-momentum and the energy–momentum relation from that:
>> <https://en.wikipedia.org/wiki/Four-momentum#Derivation>
> 
> I would like to add that the discussed statement is only *partially*
> true because of the exclusive “just” (“only”) in there.

Nonsense, you are stupid like hell. Nothing new here.
*	_P L O N K_	*

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#430924 — The problem of crackpots (was: Energy)

The ’nym-shifting troll trolled as "Ethel Ocallaghan" <unlgclo@awlwaac.ag>:

> Thomas 'PointedEars' Lahn wrote:
>>> xxein1x1@gmail.com wrote:
>>>> energy is just our way of quantifying an existence of or change of
>>>> action.
>>> 
>>> The latter is true: E = −∂S∕∂t.  It is the relation that helps to
>>> derive the four-momentum and the energy–momentum relation from that:
>>> <https://en.wikipedia.org/wiki/Four-momentum#Derivation>
>> I would like to add that the discussed statement is only *partially*
>> true because of the exclusive “just” (“only”) in there.
> 
> Nonsense, you are stupid like hell. Nothing new here.

The lecture I referred to, which was deliberately not quoted by the troll, 
Feynman concludes with this:

  “To summarize, I would use the words of Jeans, who said that, the Great 
   Architect seems to be a mathematician. And for you who don't know 
   mathematics, it's really quite difficult to get a real feeling across for 
   the beauty, or the deepest beauty, of nature. C. P. Snow talked about two 
   cultures. I really think that those two cultures are people who do and 
   people who do not-- people who have had and people who have not had this 
   experience of understanding mathematics well enough to appreciate nature 
   once.

   It's too bad that it has to be mathematics and that mathematics for some 
   people is hard. It gets reputed – I don't know if it's true – that when 
   one of the kings was trying to learn geometry from Euclid, he complained 
   that it was difficult. And Euclid said that there's no royal road to 
   geometry.

   And there's no royal road. We cannot, as people who have looked at these 
   things, the physicists, cannot convert this thing to any other language. 
   You have, if you want to discuss nature, to learn about nature and to 
   appreciate nature. It's necessary to find out the language that she 
   speaks in.

   She offers her information only in one form. We are not so unhumble as to 
   demand that she change before we pay any attention. It seems to me that 
   it's like all the intellectual arguments that you could make would not in 
   any way, or very, very little, will communicate to deaf ears what music, 
   the experience of music, really is.

   And all the intellectual arguments in the world will not convince those 
   of the other culture, the philosophers who try to teach you by telling 
   you qualitatively about this thing. Me, who's trying to describe it to 
   you, but it's not getting across because it's impossible. We're talking 
   to deaf ears. And it's perhaps that the horizons are limited which 
   permits such people to imagine that the center of the universe of 
   interest is man. Thank you.”

Q.E.D.

> *	_P L O N K_	*

Until the troll posts using yet another pseudonym.

-- 
PointedEars

Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.

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#430990

On Saturday, September 2, 2017 at 6:57:00 AM UTC+5:30, Thomas 'PointedEars' Lahn wrote:
> gehan.ameresekere@gmail.com wrote:
> 
> > Extend this to light sent to a planet 10 light years away, and it takes 10
> > years for the outbound trip and 10 years for the return trip, as measured
> > by 'clocks and trees on Earth'.
> > 
> > Any spacecraft, probe, robot, anything that goes out to that planet at the
> > speed of light and comes back will be back in 20 years time. 
> 
> No “spacecraft, probe, robot, anything” *that has non-zero mass* can “go out 
> to that planet at the speed of light (relative to Earth)”.
> 
> (The magnitude of) its momentum is
> 
>   p = γ m v
> 
>   γ = 1∕√(1 − v²∕c²),
> 
> where m is the object’s mass, and v is its relative speed.
> 
> The limit of the momentum that would have to be imparted to it in order to 
> go from relative speed zero to the speed of light, would be, in the Earth 
> rest frame:
> 
>   lim p = lim  m v∕√(1 − v²∕c²) = +∞.
>   v→c     v→c
> 
> You could also say that the object’s total energy is
> 
>    E = E₀ + Eₖ = γ m c²
> 
> with the rest energy
> 
>   E₀ = m c².
> 
> Its kinetic energy Eₖ is therefore
> 
>   Eₖ = E − E₀ = γ m c² − m c² = m c² (γ − 1).
> 
> The limit of the kinetic energy that would have to be transferred to it in 
> order for it to go from relative speed zero to the speed of light, would be
> 
>   lim Eₖ = lim m c² (1∕√(1 − v²∕c²) − 1) = +∞.
>   v→c      v→c
> 
>     [With regard to at-light or faster-than-light interstellar travel, as 
>      you mentioned it, that does not mean that it is physically impossible.  
>      For example, the Alcubierre warp drive, for example, works by 
>      contracting space in front of the spaceship (based on general 
>      relativity), so that the spaceship never really travels at high 
>      relative speeds.  It would only have an *apparent* speed that is or is
>      faster than the speed of light.  This would also solve the problem of
>      involuntary time travel to the distant future.  Unfortunately, although
>      the energy requirements could be reduced considerably in the meantime,
>      the required negative energy for the warp is still hard to come by.]
> 
> > If not travelling at the speed of light, it will go out and return in a 
> > specific time frame, for example at half the speed of light it will take
> > double the time.
> 
> For the earthbound observer.  Not for the traveler, because the traveler is 
> not traveling 10 light-years to that planet, but for them *the planet* is 
> traveling *to them* and *away from them* *less than 10 light-years* (length 
> contraction) …
>  
> > Now where is the time dilation in that?
> 
> … therefore, their clocks will not have advanced as much as the earthbound 
> observer’s during either part of the journey.
> 
> When they meet again, the earthbound observer must interpret that as that 
> the traveler’s clocks have been running slower than their own during the 
> journey (time dilation).
> 
> And the (former) traveler has to conclude that they have also traveled into 
> the future (although without an earthbound clock/calendar/etc. to look at, 
> they might not realize that immediately¹).
> 
> The more interesting question here is why the traveler does not also observe 
> the earthbound observer’s clock having advanced less than their own.  
> Because that cannot be explained with either time dilation or length 
> contraction (but it can be explained consistently within special 
> relativity).
> 
> This is a standard problem; google “"twin paradox"”.
> 
> I would consider the aforementioned knowledge to be special relativity 
> *basics*.
> 
> HTH
> 
> _________________
> ¹  Scientifically correct in that regard, that is the premise of
>    <spoiler code="rot13">“Cynarg bs gur Ncrf”</spoiler>, among
>    similar science-fiction stories.
> -- 
> PointedEars
> 
> Twitter: @PointedEars2
> Please do not cc me. / Bitte keine Kopien per E-Mail.


There are many planets within 100 light years, as mentioned here, so nothing to worry about. It is not as if hundreds of years will pass before any probe sent out returns. How would an extremely distant probe navigate is another question, by star maps I suppose. There already may be an Android app for that one, using your phone camera.

https://en.wikipedia.org/wiki/List_of_nearest_terrestrial_exoplanet_candidates


"And the (former) traveler has to conclude that they have also traveled into
the future (although without an earthbound clock/calendar/etc. to look at,
they might not realize that immediately¹)."

This is the part I do not fully understand. As someone said, you always travel into the future when you go on a trip and return from that trip. For the earth person or instruments or whatever there is no confusion. For the traveller, and the traveller could be a robot, what does it matter? For a machine it makes no difference at all how many years have passed on Earth. For a person, they know that it will be X amount of years before he can return to Earth.  If the traveller is an engineer they may not even think relativity is true.

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#430991

A journey to a distant star 50 light years away will take at least 100 light years round trip. This is of course in Earth years since we all start out on Earth. 

So I would think that a better description of the twin paradox would be to say that the time taken for an interstellar journey and return will take the number of years us earth bound people will calculate it will take, and due to certain unexplained effects, the persons or robots on board will appear to be younger than the persons on Earth. 

I believe that relativity only affects the translation of quantities and measures between a moving frame and the home frame, and not reality.

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#430994

So where is this "travelling into the future"? Where is this "Time dilation?". 

It would be interesting to look at an experiment using video cameras and video transmissions between the travelling probe and the Earth. No mathematics will be used.

Actually would it be possible to simply #simulate# a relativistic space excursion using only slowed down clocks? That's a good topic for later.

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#431133

gehan.ameresekere@gmail.com wrote:

> So where is this "travelling into the future"?

If both the Earth clock and the starship clock show zero when you leave, and 
the Earth clock shows 10 years but the starship clock shows only 8 years 
when you return, how else would you as the traveler describe this situation 
than that you traveled 2 years into the future?

> Where is this "Time dilation?".

If both the Earth clock and the starship clock show zero when the traveler 
leaves, and the Earth clock shows 10 years but the starship clock shows only 
8 years when the traveler returns, how else would you as the person on Earth 
describe this situation than that the traveler’s clock has been running 
slower than your own during the roundtrip, and that therefore time must have 
passed slower for them than for you – must have been dilated?

> It would be interesting to look at an experiment using video cameras and
> video transmissions between the travelling probe and the Earth. No
> mathematics will be used.

It will show to/on the person/video recorder on Earth that the clocks on the 
starship/probe have been running slower than their own during the roundtrip; 
and to/on the person/video recorder on the starship/probe that the Earth 
clock has been running slower than their own, but jumped ahead (with the 
numbers above, from 3.2 years to 6.8 years) when they decelerated and 
reversed course.  Light travel time excluded, of course.

A Minkowski spacetime diagram with timelike and lightlike worldlines, and 
lines of simultaneity, makes that obvious.

> Actually would it be possible to simply #simulate# a relativistic space
> excursion using only slowed down clocks?

For the reason mentioned above, no.  You have to have that time jump, too.

-- 
PointedEars

Twitter: @PointedEars2
Please do not cc me. / Bitte keine Kopien per E-Mail.

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