From: Samantha Atkins (samantha@objectent.com)
Date: Thu Dec 14 2000 - 02:33:57 MST
hal@finney.org wrote:
>
> Mike Lorrey writes, regarding http://arxiv.org/abs/physics/9804020,
> which describes ancient Indian knowledge of the speed of light:
>
> > this is one more april fools joke. the speed of light was not first
> > calculated by measuring the time differences that light took to travel
> > from Io to Earth in the 1600's depending on whether it was moving toward
> > or going away from earth (how would they measure these times? The could
> > only have done so by redshift of spectral lines, which would have given
> > us relativity long before Einstein).
>
> First, it's clearly not an April Fool's joke. The abstract reads,
>
> We survey early Indian ideas on the speed of light and the size
> of the universe. A context is provided for Sayana's statement
> (14th century)that the speed is 2,202 yojanas per half nimesha
> (186,000 miles per second!). It is shown how this statement may
> have emerged from early Puranic notions regarding the size of
> the universe. Although this value can only be considered to be an
> amazing coincidence, the Puranic cosmology at the basis of this
> assertion illuminates many ancient ideas of space and time.
>
> So the author himself is claiming only that this value is a coincidence.
I wonder. It would not be terribly surprising to me if humans were
advanced enough to know this at one time and then regressed (perhaps
with the help of some major cataclysms) to a point where even that such
existed earlier was only legend with no physical evidence (so far).
India especially has legends of humans and gods (transhumans, aliens?)
flying about in flying machines (vimanas) and cast bolts of energy and
missles of devasting power at one another. Very interesting.
>
> Second, the story about measuring the speed of light in the 1600's is
> real. You don't measure redshift due to Io's motion; you measure the
> difference in travel times due to the Earth's motion around the sun.
> Earth is 16 light-minutes closer to Jupiter at one point in its
> orbit than six months later, and so the measured interval between
> Io's orbits would slow for 6 months and then speed up for another 6.
> An astronomer correctly deduced that this was because of light taking
> more time to get to the Earth at some points in its orbit than at others.
> See http://www.phys.virginia.edu/classes/109N/lectures/spedlite.html
> for discussion on early measurements of the speed of light.
>
So this makes it even more likely that the speed of light was known in
India quite some time ago.
- samantha
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