The Rotational Speed of Babylon 5
There are two pieces of direct evidence concerning the rotation of Babylon 5. There are a number of exterior sequences in the TV shows which show the front end of the station rotating. We can try to estimate one complete period of rotation by looking at timed quarter-rotations of the station and measuring when a regularly-spaced marker (such as a Cobra Bay arm) disappears into shadow under the Spine. Unfortunately, there are not many long-enough film sequences and it is hard to estimate the times accurately.
Another piece of evidence comes from the season 2 closing episode [tFoN], in which Sheridan leaps from the booby-trapped core shuttle towards the rotating inner circumference of the Carousel, which Susan Ivanova says is rotating at "60 miles per hour". To check this, we can reverse-engineer from the speed necessary to simulate 1g acceleration inside the Carousel.
From the later TV shows and [SM] p14-15, it's clear that a large portion of the main Carousel is built to a standard internal radius, so assume this is the 1g level. It extends through Green and Red Sectors; the heaviest Blue Sector deck would then experience less than 1g. The wider parts of the Carousel would experience more than 1g, which is consistent with providing environments with different strengths of gravity. Starting with some known data:
The internal radius of the Carousel, r is d/2 = 362m.
Standard acceleration due to gravity g = 9.81m/s².
One formula has g = v²/r, where v is the tangential velocity. So, v = sqrt(r*g) = 59.59m/s, or 60m/s to the nearest m/s.
This contradicts Ivanova in [tFoN] where she says "60 miles per hour". If this were true, the Carousel would experience only about 1/5g and station personnel would be jumping around like moonwalkers! We can show this from the same formula:
Ivanova's velocity v1 = 60 miles/h = 96.561km/h = 26.82m/s.
Acceleration g1 = v1²/r = 1.987m/s², which is 0.203g.
So, I'm afraid I have to insist that: "Ivanova is NOT always right, Ivanova is NOT God and I will NOT always listen to Ivanova" (after her outburst in [aVitW1]), sorry, Susan! But it's instructive to notice that, if we convert her "60 miles per hour" into 60m/s, we are back in the right ball-park. Perhaps she simply mis-read the units in the station manual, in her haste to help Sheridan!
From the tangential velocity at the internal circumference, we can estimate the period of rotation. The internal circumference of the Carousel is 2275m. This distance would be covered in one rotation. According to Ivanova, the station only rotates at 26.82m/s, which works out at one rotation every 2275/26.82 = 84.82 seconds, approximately one minute and 15 seconds. If our more accurate estimate of 59.59m/s is used, then the station completes one rotation every 2275/59.59 = 38.18s, approximately every 38s.
We can cross-check this figure using another formula for the acceleration due to rotation: g = a²*r, where a is angular velocity in radians/s. There are 2*pi radians in a single rotation, so:
These two calculations are in close agreement, showing that the formulae do calculate the same quantities. For scientific accuracy, we must go with a rotational period of 38s and a tangential velocity of 60m/s.
