John,
I agree that the limitation is not on traveling between places, it is on
traveling between events. He arrives (in your table) at an earth time of
3.6x10^10 yrs after take-off. He cannot arrive (with the given parameters)
at any event earlier than what is then occurring at his destination (he has
missed his luncheon date :)
Thanks for the nice development.
-Bob
Bob Sciamanda
Physics, Edinboro Univ of PA (Em) http://www.winbeam.com/~trebor/
trebor@winbeam.com
----- Original Message -----
From: "John Mallinckrodt" <ajm@csupomona.edu>
To: "Bob Sciamanda" <trebor@winbeam.com>; "Forum for Physics Educators"
<phys-l@carnot.physics.buffalo.edu>
Sent: Wednesday, February 22, 2006 3:04 PM
Subject: Re: [Phys-l] geometry of spacetime (was: relativisitic mass ...)
| Bob S wrote:
|
| >John M wrote:
| >
| >>The fact that that object *appears* to another observer to
| >>asymptotically approach the speed of light is the *observer's*
| >>problem!
| >
| >Whatever this means, is it not in the same way the "object's" problem
that
| >the left behind observer "appears" to asymptotically approach the speed
of
| >light?
| >
| >We understand that speed is a relative quantity and that the idea of an
| >"intrinsic" speed is without meaning or use. So what's the point?
|
| I agree with most of what you and John D have had to say about my
| remarks, but I think there IS an important point to be made by noting
| that relativity places no MEANINGFUL limits on travelers. In fact,
| quite the contrary.
|
| For instance, a person starting from rest and moving for 25 years
| with a constant and PERFECTLY comfortable acceleration of 1 light
| year per year squared (one "light per year"?), travels a little over
| 300 light years in a Newtonian universe. In a relativistic universe
| a stationary observer would determine that the same person travels
| not quite 25 light years.
|
| Both of these distances are overwhelmingly meager compared to the
| size even of JUST our own galaxy, they barely get us to a few other
| stars, but the relativistic result looks most discouraging. It seems
| to bolster the idea that there is a fundamental "speed limit" imposed
| by relativity and I think many have internalized that idea to the
| point that statements like "things get harder to accelerate" acquire
| far more cachet than they deserve.
|
| To counter this notion, I like to point out that the traveler him or
| herself can reach objects over 30 billion light years away, about
| twice the size of the entire observable universe by accelerating at
| that same rate for 25 years as measured by his or her own clocks.
|
| See <http://www.csupomona.edu/~ajm/professional/talks/atgtc.pdf> for
| a not very elegant look at these issues.
|
| --
| John "Slo" Mallinckrodt
|
| Professor of Physics, Cal Poly Pomona
| <http://www.csupomona.edu/~ajm>
|
| and
|
| Lead Guitarist, Out-Laws of Physics
| <http://www.csupomona.edu/~hsleff/OoPs.html>
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