Just tried again, and I see a shimmering sun in all three browsers. I also tried from my phone (not on Wi-fi, so different IP) and I get the same shimmering sun. Clearly Randall Munroe doesn’t like me - or just turned off the JS cleverness.
In my browser (way-old Firefox version running on way-old Linux platform), with JavaScript disabled, I get a mundane strip in which a male and a female character discuss the purchase of a simple desk lamp, as informed by various on-line reviews that they find. With JavaScript enabled, I see the Northern Lights strip, in which one of the characters says he only saw clouds.