Sundial with "multitudinous faces"?

Jeff Wilson · 13 May 2011, 18:05 · from 2011-May.txt.gz

This is the message as the crawl holds it, before anything here touched it. What the conversation shows has been through ingest: transfer encodings decoded, attachments dropped, quote markers repaired, and the archiver’s ? resolved into quotation marks and dashes. Those repairs are judgements and some of them are wrong, which is what this page is for. Email addresses are obscured here as they are everywhere else on the site, so it is before our repairs rather than byte for byte.

From: jwilson at io.com (Jeff Wilson)
Date: Fri, 13 May 2011 13:05:53 -0500
Subject: (urth) Sundial with "multitudinous faces"?
In-Reply-To: <136906.58189.qm at web114718.mail.gq1.yahoo.com>
References: <BANLkTi=Av8hgtqywSRrR2u2RK1besHpTBg at mail.gmail.com>	<4DCB99B5.9090009 at io.com>	<A4F1B6DA-7F73-4378-A889-3518B09A8DCA at butcherbaker.org>	<BANLkTimfpzXR86OM+rS70VXQVF6V3dKGYw at mail.gmail.com>	<BANLkTimFOJ2tbs42r+AdaU_DGq5ow4G2AQ at mail.gmail.com>	<426F9A20-11AC-4493-AE69-5D8162933F6A at butcherbaker.org>	<BANLkTikE9n4fvYpwQ6Zj2v7JVB+_bYza6A at mail.gmail.com>	<BANLkTina2hR=CT=MhAAiayaEq853NG5YvQ at mail.gmail.com>	<4DCC1FEC.9090904 at gmail.com>	<881344.47809.qm at web114712.mail.gq1.yahoo.com>	<4DCC4497.5070602 at gmail.com>
	<136906.58189.qm at web114718.mail.gq1.yahoo.com>
Message-ID: <4DCD7301.10005 at io.com>

On 5/13/2011 12:47 PM, Jerry Friedman wrote:
>> From: James Wynn crushtv at gmail.com

> Let me try to explain the same thing as Dan'l and Sergei.  When the sun is at a
> certain place in the sky (I mean when Urth is aiming the Citadel at a certain
> angle to the sun), the sundial will show a certain time.  A day later, the
> sundial will show  a similar time, and 365 days later [*], an even more similar
> time.  But if it was morning on Mongo during the first reading, there's no
> reason for it to be morning on Mongo at the later two readings, since Mongo's
> day presumably isn't the same length as Urth's.

Is it the same time everywhere on Mongo at once? :)

>> Of course, I might have been taken in by metaphor: They could have been
>> actually saying that if you travel instantaneously to a distant star, you are
>> moving FORWARD in Time since the star we can see from Earth is some number years
>> ago. Or something along those lines.

Since the rate of time's progression is relative, you can't say travel 
is instantaneous without saying in which frame of reference it is 
measured as instantaneous. Since other, equally valid frames of 
reference measure the time between your departure and your arrival as 
having finite, you can switch over to a frame where it was negative, and 
do the instantaneous thing in that one, then find one where that was 
negative, and do it again, etc., and that's how you end up  returning 
before you left.

> Well, if there's FTL travel, then something is wrong with relativity (as I think
> Dan'l said), so we don't have a basis to say what would happen.

There are numerous relativity-compatible physics models that seem to 
allow for time travel, but explain the lack of of observed time travel 
by positing it requires improbable arrangements of nigh-unobtainable 
resources. Robert L Forward's negative mass as dramatized in his novel 
TIMEMASTER is once example: matter whose density is negative causes a 
negative curvature of space-time, opposing the positive curvature from 
positive mass, among other weird things, but complies with all known 
physical laws.

-- 
Jeff Wilson - jwilson at io.com
Computational Intelligence Laboratory - Texas A&M Texarkana
< http://www.tamut.edu/CIL >

An unofficial mirror of a public mailing list · about & removal requests · download the archive · before the list · original archive at urth.net