Some Words of Wisdom

To know is nothing at all; to imagine is everything.~ Albert Einstein 

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maximum diameter of universe

relativity of motion :

Interestingly, from an external frame of reference, 0 is stationary.
But from the point of view of either A or B, 0 is receding from them at the speed of light!
And A and B are separating (i.e. the space/distance between A and B is expanding/increasing)at twice the speed of light!
So motion is relative to one's observational frame of reference.

If O is tbe point of origin of the universe and the maximum velocity of the Big Bang wave front was "c" (assuming that the wave front generated by the Big Bang propogated outward in all directions at the maximum allowable speed) ,
then A and B represent the outer boundaries of an expanding sphere.
The distance between A and B is the diameter of the universe wch is expanding at a maximal velocity of 600,000 km/second.
Accepting that the universe is 13.7 billion years old(13.7 billion years to zero time) we can calculate the number of seconds in 13.7 billion years =X seconds*.
Since the diameter of the universe is expanding at 600,000km each second,
the present diameter of the universe is:  600,000km x X seconds* =
13.
7 billion years x 31,536,000 s/ year =  13.7 x 10^9 years x 31,536 x10^3 s/year=  4,320,43.2 x10^12 seconds

6x10^5km/s x 4,320,432 x10^11s = 25,922,592 x 10^16 km = 2.6 x 10^23 km

*How many seconds in a year:
60 s/minute
60 minutes/ hr
3600 s/hour
24 hr/day
86400s/day
365 days/ year
31,536,000 s/ year

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In one year light travels 9.5 x10^12 km
In 13.7 x 10^9 years it will have travelled  130.15 x 10^21 km =1.3 x 10^23 km

radius of universe = 1.3 x 10^23 km 
diameter = 2.6 x 10^23 km

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V=d/t. (velocity =distance/time )
v=c= maximum allowable velocity of expansion.
d= distance from point of origin to outer edge or boundary = radius of universe
t= 13.7 billion years(time from t=0 to now)

d=vt
v= c=9.5x 10^12 km/year
d=9.5x 10^12 km/year X 13.7 x10^9years =130 x10^21 km =1.3 x 10^23 km (this is the radius from center to outer edge, and the maximum distance light has travelled in 13.7 billion years)
Hence diameter = 2r= 2.6 x 10^23 km