Let's say have no artifacts in my library and I cast Madcap Experiment. I die. Buuuuut, what if I exile Geistblast to copy Madcap Experimentand send the "copy" to my opponent. Which damage goes on the stack first?
What do you mean, "send the copy" to your opponent? You still control the copy. Geistblast does not let you change the controller of the copy, just its target, and Madcap Experiment has no target.
Both the copy and the original resolve revealing cards from your library and dealing damage to you.
Which damage goes on the stack first?
The damage does not go on the stack. Only the spells themselves.
The original Madcap Experiment goes to the stack first, then Geistblast's ability that you activate in response. The ability resolves first, creating the copy. The copy will be on the stack above the original Experiment and will resolve first. But see above, both copy and original deal damage to you, never to your opponent.
You eat the damage from the copy of Madcap Experiment and, well, die in an even more spectacular manner. Madcap Experiment doesn't target players (or anything else, for that matter) and the copy created by Geistblast is controlled by you, therefore you will be the one revealing cards from your deck and die due to not having any artifacts.
What do you mean, "send the copy" to your opponent? You still control the copy. Geistblast does not let you change the controller of the copy, just its target, and Madcap Experiment has no target.
Both the copy and the original resolve revealing cards from your library and dealing damage to you.
The damage does not go on the stack. Only the spells themselves.
The original Madcap Experiment goes to the stack first, then Geistblast's ability that you activate in response. The ability resolves first, creating the copy. The copy will be on the stack above the original Experiment and will resolve first. But see above, both copy and original deal damage to you, never to your opponent.
Edit: Sniped