# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

**Re: Cel nav in space**

**From:**Peter Fogg

**Date:**2005 Jan 14, 11:38 +1100

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{at}LISTSERV.WEBKAHUNA.COM] On Behalf Of Renee Mattie Sent: Thursday, 13 January 2005 7:11 AM To: NAVIGATION-L{at}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{at}LISTSERV.WEBKAHUNA.COM] On Behalf Of Peter Fogg > Sent: Thursday, January 06, 2005 7:11 PM > To: NAVIGATION-L{at}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). >