Scaling Bank's Culture
I love the Culture novels by Iain M. Banks but sometimes had problems visualising the scale of things, speeds, relative distances, that sort of thing. I do understand my local area and hence tried scaling everything down so that I could relate it to units I was more familiar with. This is what I came up with:
On a scale of 1cm = 1 million km: ( 1:10^11 ) -
Our Sun is the size of a small grape (1,392,684km, so 1.3 cm)
An orbital (of diameter 3 million km) would be 3cm across, 1/100 mm wide, and (earth orbit 149 million km) orbit at a distance of 1.5 m from our sun, (Hence, 1AU is also 1.5m)
All planets would be very small, even Jupiter at 1.4mm
Neptune would orbit at a distance of 45m
The Oort cloud distance is 7.5 to 12km
1 light year (9 * 10^15 metres) is 94km, so the speed of light is 94km per year, 259m per day, 11m/h
So alpha centauri is approximately 400km away, so a bit further than the distance from London to Paris
There are around 50 systems in a globe of 1600km radius - Space, really, really empty, especially around our part of the other galaxy. If we look instead at an average density globular cluster that would have 0.4 stars in 142Km radius sphere, rising to 100+ in centre, but still places even the closest stars tens of km apart.
The entire galaxy is 100,000 light years across, so 9,400,000km in our scale A plate class GSV can travel at 104 kilolights, so 104*11 = 1,144 km/h (about 710 mph, a bit over Mach 1), it would reach alpha centauri in about 20 mins (ignoring acceleration & deceleration, call it an hour)
A range class GSV can do 144 kilolights = 1584 km/h (or 984 mph, mach 1.4) and could cross the galaxy (without stopping!) in about 250 days (plus acceleration and deceleration time again), and reach the Magellenic clouds in 400 days.
The Andromeda galaxy is 2.5 million light years away, so about 17 years at full speed
In comparison, if we are normal size , travel on foot at 6km/h = 0.545 lights, so perhaps we can imaging ourselves as a in-system module.
Travelling by car at 100km/h equates to 9 kilolights so a better comparison to culture space craft is airplanes in our scale.
(I may have messed up a few calculations, please let me know, but I found this exercise useful in understanding the scale of the Culture).