Professional authors say it’s important to keep the reader suspending his disbelief. How could he buy into the story of Elantris without believing that Aons channel the power of Dor and do miracles? The reader must believe that in this imaginary world things exist just like the author describes them. If the writer can make the reader do that, he is halfway through to success.
There are a few things which throw me as reader out of the story. One of those is the sentence: “Then the time slowed down”. Alternatively it can be “He (she) saw everything in slow motion”. It happens, when something important is going on and the writer wants to explain everything in details. For him it’s quite convenient if the “time slows down” since he has more time (read: more words) to guide us through that moment.
But for me it works differently. When I read that sentence I roll my eyes and I murmur “not again, please”.
Just take a fight scene as an example, this phenomenon with the speed of the time tend to happen when guys beat up each other. Let’s say Jack is about to hit Dave, who stares right at him, lifting his hands to defend himself. Time doesn’t give a damn, it flows as it does all the time. Jack punches Dave in the face in a millisecond sending him in the air so he lands on his back. Dave may be able to dodge, or deflect the blow and score a hit on Jacks stomach. It’s because Dave is quicker and he can do it in half millisecond. It has nothing to do with time, it’s fine with its normal speed, thank you. Jack’s blow and Dave’s counter attack what happens damn quick.
If Dave really sees it in slow motion, than it’s a different story. He may be a time traveller superhero, cleaning the streets from bad guys like Jack. Or he may possess a device messing up with the flow of time. Or something else happens. But either way, when “time slows down” I immediately switch to time-traveller science-fiction mode. Which means I’m out of thriller mode, out of fantasy mode, out of romance mode. Out of the story whatever I read. Neo here is the example when time really slows down. But now I’m in sci-fi mode, as I said.
Unfortunately this phrase became so cliché, it is widely accepted.
By the way, I just came across this interesting post, which questions the same thing.