Text 28599, 89 rader
Skriven 2007-05-05 07:06:15 av John Hull (1:123/789.0)
  Kommentar till text 28598 av Jeff Binkley (1:226/600)
Ärende: Muslems
===============
Jeff Binkley -> Bob Ackley wrote:
 VH>>>>>> And explain how we can cross interstellar space?

 TA>>>> Given the fortitude and acumen displayed by our African
 TA>>>> ancestors travelling from Africa to the Middle-East and Europe
 TA>>>> in their time, I think we can master interstellar space to our
 TA>>>> next new habitant in our time.

 VH>>> I just asked this question of John.  We want to go to a planet
 VH>>> that is 10 light years away.  At an accleration of 1G, how long
 VH>>> will it take us to get there?

 BA>> Couple of centuries, most likely.  Note that you can't accelerate the
 BA>> whole way, at the halfway point you have to start decelerating,
 BA>> presumably at the rate of 1G.

 JB> I posted this a couple of days ago:

 JB> Actually it isn't as difficult as you are making it.  If you assume that
 JB> your braking deceleration is the same as your acceleration then you
 JB> simply divide the distance by half to calculate the midway point of
 JB> acceleration.  Once you have the answer then you multiply by 2 to get
 JB> the total time.  Mass and thrust are irrelevant because Vern said
 JB> acceleration was constant.  Of course where does the force of 1G
 JB> acceleration come from ?  Well Vern will have to let us know that trick.

 JB> Now the issue here is the speed of light.  If we assume Einstein is
 JB> right then the question becomes how quickly do we reach the speed of
 JB> light under 1G acceleration and then we will go the speed of light the
 JB> rest of the way to the midpoint, unless we can't reach the speed of
 JB> light by the midpoint.

 JB> The acceleration rate of 1G (using earth as the reference for G) is 9.8
 JB> m/s^2.  Easier to round to 10 m/s^2 .  The speed of light is 300,000
 JB> km/s .  Without using Calculus the formula for acceleration in Physics
 JB> is:

 JB> v = v0 + at

 JB> v0 is initial velocity
 JB> a is acceleration
 JB> t is is time
 JB> v is current velocity
 JB> in this case we are starting from rest so v0 = 0 .  Thus the time it
 JB> takes to get to the speed of light becomes:

 JB> 300,000,000 m/s = 10 m/s^2 * t

 JB> or 30 million seconds which or just over 347 days.  So at that point we
 JB> will travel at the speed of light until 347 days before arrival and then
 JB> we start braking.

 JB> We haven't solved for X yet to determine the distance traveled in the
 JB> 347 days on either end of the trip.  I'll leave that for anyone
 JB> interested in going further with this.


 JB> ==========================

 JB> The answer is somewhere between 11 and 12 years.  If someone is
 JB> interested I'll do the mth to get th exact number.


 JB> Jeff


I found a website that went into the physics in much greater detail, and I
wasn't really into doing all that math.  But, the gist of what they said is
close to what you said above.  The nearest start is roughly a 15 year trip.  By
the time we feel up to trying that, I have no doubt that we will have the means
to induce some sort of hibernation sleep which will make it relatively easy for
the crew.  The real problems are earth-side.  If we send a ship out to a star
that is far enough away but still reachable, they may spend 30 years in
cryosleep, but hundreds of years will pass here on earth.  There is the very
real possibility that we could discover and build a ship in that time capable
of actually overtaking them and arriving before they do.

However that sort of thing plays out, I was referring to our own backyard in my
original posts, not interstellar travel.  As I said, I think Mars will be
visited in my lifetime, and possibly we will even see the beginnings of
industrial ventures to the asteroid belt and some of Saturn's moons.

-- 
John
..
My Blog: Mad Gorilla's Jungle:      http://madgorilla.terapad.com/

--- Thunderbird 1.5.0.10 (Windows/20070221)
 * Origin: The Eastern Star - Fidonet Via Your Newsreader (1:123/789.0)