Look up "Solar Simulator." It's a real device scientists use to test the effects of sunlight on various things, from solar panels to satellites (depending on the size of the simulator).
Flerfs think NASA has one that they bring out during the day and float in the sky just to make Flerfs look stupid, when in reality, they don't need any help looking stupid.
Could be in response to the guy who wants to bring flat earthers to Antarctica. He wants to prove a globe by showing them, that there is 24 hours of daylight there. Now the flat earthers a fabulating about a sun simulator as a counter to it.
I've delved down this hole myself in recent months because it's fun. YouTube channels I'd recommend for people wanting to laugh at flerfers:
The ones I can think of off the top of my head are: SciManDan, Creaky Blinder, Conspiracy Toonz, David McKeegan and Fight The Flat Earth (FTFE). I've also been watching a lot of Planet Peterson lately, but his way of doing things is very much "say something stupid and I will verbally lay into you until you admit you're a fucking dumbass" which I'm sure can grate on some people and make him come across as very obnoxious and rude.
But they will all help educate you on why flat earth (and other conspiracies aside) are stupid, to varying degrees, espeically Dave McKeegan if you're into photography.