I was just thinking if a nuke hit Voldemort, would he be completely unharmed due to his Horcruxes making him immortal, or would he turn to ash?
In general, what would happen if Muggle technology were used against him?
The Dark Lord’s body would die if he was hit by a nuclear bomb and was unable to stop it with magic. Having Horcruxes doesn’t do anything to prevent the body from dying, they just tie the soul to life so that it remains earthbound even if the body is killed.
“Well, you split your soul, you see,’ said Slughorn, ‘and hide part of it in an object outside the body. Then, even if one’s body is attacked or destroyed, one cannot die, for part of the soul remains earthbound and undamaged. But, of course, existence in such a form …”
- Harry Potter and the Half-Blood Prince, Chapter 23 (Horcruxes)
The soul contained in a human being remains intact, no matter what happens to the body. Since this presumably applies to highly destructive causes of death like being burned by Fiendfyre, it should also apply in the case of a nuclear blast.
“Seeing that Harry and Ron looked thoroughly confused, Hermione hurried on, ‘Look, if I picked up a sword right now, Ron, and ran you through with it, I wouldn’t damage your soul at all.’
‘Which would be a real comfort to me, I’m sure,’ said Ron.
‘It should be, actually! But my point is that whatever happens to your body, your soul will survive, untouched,’ said Hermione. ‘But it’s the other way round with a Horcrux.”
- Harry Potter and the Deathly Hallows, Chapter 6 (The Ghoul in Pyjamas)
There’s also no reason to think it’d be impossible to kill a wizard with Muggle weapons, provided they weren’t able to stop the weapon with magic. In his footnote for “The Wizard and the Hopping Pot”, Albus Dumbledore mentioned how Muggles were indeed able to kill some wizards in their witch hunts.
“1 It is true, of course, that genuine witches and wizards were reasonably adept at escaping the stake, block, and noose (see my comments about Lisette de Lapin in the commentary on “Babbitty Rabbitty and Her Cackling Stump"). However, a number of deaths did occur: Sir Nicholas de Mimsy-Porpington (a wizard at the Royal Court in his lifetime, and in his death-time, ghost of Gryffindor Tower) was stripped of his wand before being locked in a dungeon, and was unable to magic himself out of his execution; and Wizarding families were particularly prone to losing younger members, whose inability to control their own magic made them noticeable, and vulnerable, to Muggle witch-hunters.”
- The Tales of Beedle the Bard
Therefore, what would happen is he’d be ripped from his body like he was when he was hit by the rebounding Killing Curse - he wouldn’t die but his body would be killed.
“I was ripped from my body, I was less than spirit, less than the meanest ghost … but still, I was alive. What I was, even I do not know … I, who have gone further than anybody along the path that leads to immortality. You know my goal – to conquer death. And now, I was tested, and it appeared that one or more of my experiments had worked … for I had not been killed, though the curse should have done it.”
- Harry Potter and the Goblet of Fire, Chapter 33 (The Death Eaters)
If he was successfully hit by a Muggle weapon and he couldn’t stop it in time, the Dark Lord’s body would be killed, but it wouldn’t kill the soul within him, since even highly destructive causes of death don’t kill the soul. His soul was also tied to life by the Horcruxes, so it’d remain on earth in spirit form.