Back on Earth, centuries ago, the tradition of three-ring circuses developed so that different kinds of acts could be run simultaneously to hold the audience's interest. Comedy in one ring, skill in another, death-defying acrobatics in a third, for instance. That's considered old-fashioned nowadays, but some of the circuses on Earth still do it -- mostly the ones with a permanent, fixed location.

The Armstrong Circus is one that travels among the colonies as well as around Earth. Space is at a premium.

Accordingly, they only have one ring, and the audience in a wide circle around it. The way they manage simultaneous acts is vertically.

So when the lights lower, the first act -- two elephants, and several spangled people perched atop them -- bursts onstage to jaunty music and applause, and it's only a couple of minutes before a long expanse of silk ribbon descends from the catwalk with an acrobat artfully tangled in it.