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Groups > sci.physics.relativity > #430783
| From | Thomas 'PointedEars' Lahn <PointedEars@web.de> |
|---|---|
| Newsgroups | sci.physics.relativity |
| Subject | Re: Interstellar Travel and time taken for the trip. (No time dilation for the Earth) |
| Date | 2017-09-02 03:26 +0200 |
| Organization | PointedEars Software (PES) |
| Message-ID | <34221433.10thIPus4b@PointedEars.de> (permalink) |
| References | <7a2245c1-0f89-41df-8571-afb3f24e8930@googlegroups.com> |
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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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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