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And my thanks to Renee for this interesting information.

Thanks also to Frank Reed for his stereo views of our near stellar neighbours at
www.historicalatlas.com/stars

This was something I have wondered about but had never imagined could be shown
so graphically, in 3D no less. Had no idea there were so many red dwarfs in the
nieghbourhood - guess they are so dim that they are normally not noticed.

-----Original Message-----
From: Navigation Mailing List [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM] On
Behalf Of Renee Mattie
Sent: Thursday, 13 January 2005 7:11 AM
To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
Subject: Re: Cel nav in space

Peter,

Anything could, presumably, travel at a relative velocity close to c.
It's just that the energy required to accelerate the mass to that velocity is
enormous.

According to Special Relativity, Neutrinos travel at close to the speed of light
(assuming they have mass), or else at the speed of light (assuming they have no
rest mass).  They're a little hard to pin down.

Of course, we know that Einstein's General and Special Relativity don't agree
with quantum theory, and string theorists
(http://www.pbs.org/wgbh/nova/elegant/)
tell us that relativity doesn't get it quite right.  It is possible that the
neutrino doesn't actually exist.  It *MIGHT BE* possible to exceed the speed of
light, but maybe only for subatomic particles.

I doubt that there will be any practical application of near-light (speed
relative to the stars near enough to steer by) or faster-than-light navigation
within my lifetime or that of my children.

It is fun to think about, though.  Figuring the corrections to apparant
altitudes or apparant angles between distant bodies due to refraction caused by
atmosphere is one thing.  Figuring position and orientation from the angles
between stars from various points in the galaxy (Are you SURE you could
recognize Vega if you were right next to Alpha Centauri?), correcting angles for
the Lorentz contraction as a function of relative speed and angle relative to
your direction of travel -- well, you won't get by with a copy of Bennets and a
lifeboat sextant.

Many thanks to everyone who has contributed to this thread.
Something my daughter (a six-year-old aspiring astronaut) and I can enjoy
looking into.
Well, perhaps in a few years, after she has had a chance to study trig.

Renee


> -----Original Message-----
> From: Navigation Mailing List
> [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM] On Behalf Of Peter Fogg
> Sent: Thursday, January 06, 2005 7:11 PM
> To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
> Subject: Re: [NAV-L] Cel nav in space
>
> Does anything (apart from electro-magnetic energy itself) travel at
> speeds close to c?
>
> ________________________________________
> Frank Reed wrote:
> At 99% of the speed of light, time aboard ship would slow by a factor
> of 7.
> So for shipboard passengers, the trip would only take 290 thousand
> years.
> Hmmm... Still stinks. Ok, let's crank it up to 99.99% of c.
> That raises the time dilation factor to 70.7 so the trip would take
> merely 29 thousand years. Every "pair of nines" in that fraction of c
> adds a factor of ten to the time dilation so to get the journey down
> to less than three years of shipboard time, we would need to travel at
> 99.99 99 99 99 99% of the speed of light. You age three years aboard
> ship, everything else ages two million years (time dilation factor is
> 1000000/sqrt(2).
>

   

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