"So, an engineer and a mathematician are leaving a lecture. The engineer says, 'I just don't understand how you can visualize objects in seven-dimensional space.' The mathematician says, 'Oh, that's easy. You just visualize the n-dimensional case, and then set n equal to seven.'"

"I've never liked that joke. The punchline is intended to be absurd, but it's not: that's actually how you do it."

"Really?"

"Okay, fine. You visualize the three-dimensional case, and then set three equal to seven."