Selected snippet, on the subject reparo spell
“What’s this that I hear about the Mending Spell?” Julia cut in before the bickering started up again.
“Hermione thinks the Mending Spell is actually rather powerful.” Raj said.
“It’s convenient for fixing fine china…” Abraxas said doubtfully.
“But that’s the point, isn’t it? It doesn’t stop at something as small as a teacup. Nutley’s spell reconstructed the Coliseum that was reduced to rubble. Just in that moment, her Mending Spell instantly made obsolete several building restoration and fixing spell. Suddenly anyone who had inherited a house and was satisfied with how it looked will be able to preserve it as it is forever, as long as they kept casting the spell regularly!” Hermione finished.
The magnitude of Reparo’s abilities had only dawned on most of them then.
"You’ll understand better the significance of what Nutley achieved if you recall a recent concept in Advanced Transfigurations class," Tom spoke up.
“Permanent transfiguration relies on knowing the nature of the object you’re changing?” Abraxas made a random guess.
“Order is always unravelling into disorder.” Julia suddenly said.
“It’s that thermos-law thing Hermione mentioned.” Adil said while rubbing his forehead, probably trying to recall it.
“Second Law of Thermodynamics,” Hermione clarified. Her housemate snapped his fingers with a relieved expression.
“That’s the whole ‘some processes are irreversible’ thing, isn’t it?” Abraxas said. “You can permanently transfigure wood into ash, but you can’t do the opposite.”
“You can’t reverse the flow of time.” Tom said.
“But we can use a time turner.” Julia disagreed.
It was Hermione who shook her head. “No, no. You’re transporting an object, a person to an earlier point in time, but you’re not undoing anything. Isn’t it one of the major warnings given to anyone who managed to get a license to use a time turner? You can’t change events that are already known and established in your timeline. Cross that at your own peril.” They were following Novikov’s principle, obviously.
“Some processes are irreversible, as Abraxas had said, while Julia and Shafiq made a good point on how order is always unravelling. Time cannot be made to flow in reverse, as Hermione had pointed out.
Now, wouldn’t the fact that Reparo can restore an object to its condition at an earlier point in time (though obviously not too far into the past), meant that it has some degree of ability to cut through time and space built into it?” Tom stepped in once more.
He was too good at keeping track of the conversation’s details and then drawing everyone’s attention, at ensuring they all realised the magnitude of the point he was making.
“Now, you’d have to wonder about the older spells Nutley had read about and integrated into her Mending Spell, isn’t it? My hypothesis is that she’d studied more than one spell or fragments of one that came from Atlantis and used them as the foundation for her spell.”
“Why cut through time and space?” Hermione asked curiously.
“To create a copy of the less-broken form of the object from an earlier point in time.” He answered.
“Or, it only has the ability to peer into the past and retrieve the information of what the broken object’s fixed form looked like and recreate that at the present time. It might not even be necessary for the spell to be able to interact with the past as long as it can take the information it needed.”
Abraxas followed their conversation with wide eyes.
Tom nodded slowly. “You’re right. That is also plausible.”
Taken from "Strange Attractors", a Harry Potter fanfiction; chapter 44 | ffnet | Ao3
