This really cool guy called Dragondrawing33 came up with the Science of Loops which I thought would be great to post on here because it's insanely cool. Everything below is a direct quote from him, and I do have permission to write this on here though please remember that the explanation is not mine. Thanks!
The Science!!! Of Time Loops
Hahaha! Sorry, it just hit me that I'm learning general Relativity to explain a bird-lady Timelord, WITHOUT even being paid to do so!
Ymbrynes are the bird-human shapeshifter, babysitter, and time manipulators of the peculiar book series- Miss. Peregrines home for peculiar children. And I have been asked to explain their Time Looping ability.
The Ymbrynes are able to loop time in a restricted area, closed off to anyone who isn't peculiar (or Syndrigast, translating to literally "Peculiar spirit"), and has to be reset once-a-day. The peculiars staying in the loop, stay the same age, presumably forever if undisturbed, but will age forward if they leave the loop. How are they doing this?
There are several ways to time travel, the first is called Time Dilation. (I am going to put this very simply, and I encourage you to learn this yourself, it's very interesting) According to the Theory of Relativity, proposed by Albert Einstein in 1905, Time dilation is a difference is time measured by two or more observers, due to velocity or a large gravitational force.
This is very complicated, but I'm doing it anyway! If I take two clocks, I leave one on Earth and launch the other at a black hole, if I was able to somehow observe both at the same time, I would see that the clock orbiting the black hole is ticking slower than the one on Earth. This is because large gravity sources, alter and distort space and time.
There is another way to utilize time dilation, Velocity. Velocity is effectively, speed as well as the direction of motion. Using the same example, if I launch a clock into space traveling hundreds of miles per second, and leave the other on Earth, the one in space will be ticking slower than the one on Earth, this is because it's not just gravity that affects spacetime, velocity does too.
Believe it or not, some humans have time traveled, and no, I'm not saying Timelords live among us, or that the creator of the Simpsons is from the future. Astronauts on the ISS (International Space Station) have to adjust their clocks because their moving so quickly through space, approximately 17,227 miles per hour, 15.54 orbits per day, time relative to them is slower than it is to all us earthbound people.
But all this is time traveling into the future, how am I supposed to bring Thomas Jefferson Machine guns if I can't travel back in time? Thankfully Kurt Gödel solved my problem for me, by discovering Closed Time-like Curves. Kurt Gödel was weird, he saw conspiracies and loopholes everywhere, and on Albert Einstein's Thirtieth birthday, he presented him with the ultimate loophole, a way to travel back in time without having to travel faster than the speed of light. Traveling faster than the speed of light, which in a completely empty space, devoid of even air, is 299,792,458 meters per second, is impossible, with what we know about the universe thus far. This is going to get even more complicated than time dilatation, just hold on!
You know that if you want to travel faster in a car, you have to apply more pressure to the gas pedal right? Well, it's the same concept for accelerating up to the speed of light, if you want to go faster you have to use up more fuel. And at the speed of light, the energy requirements would be effectively infinite, because, at some time, you're going to reach a point where the amount of fuel you're carrying, is adding more weight to the ship then the energy it's producing is enough to accelerate, and thus you'll need more fuel to go faster, basically, this is the speed limit of the universe.
Kurt Gödel's Closed Time-like curve theorem states that if you have a massive gravitational force, say a black hole, and if the said gravitational force is spinning at ludicrous speeds, then due to the fluid nature of time, you're going to have areas of space-time where it loops back on itself. Boom! Time travel to the past is possible!
Do you have a headache yet? ME TOO!
Miss. Peregrin is creating a large gravitational force and spinning it, reversing time. But there's a problem (Isn't there always?) actually, several problems
Miss. Peregrin would have to be creating a gravitational force equivalent to that of a neutron star, tearing apart the Earth and Moon in the process. So let's just assume Miss Peregrine's peculiarity allows her to contain the gravitational force in a small area, which is impossible, but I want to keep theorizing, so just accept this. The far bigger problem is that, if this is truly how Loops work, then it would violate Causality, or the flow of time, in theory, there should be multiple groups of Peculiar children capable of interacting with each other.
But how many? How many different groups of Peculiars stalk Cairnholm Island? In the first book, we learn that the peculiars were stuck in the year 1940 and that Miss Peregrine resets the loop right after sunset, seconds before a bomb from a Nazi air raid would have been dropped on their heads. I couldn't find any mention of when the present in the book is set, so we're going to assume its set in the year the book was published, 2011, we can multiply the difference of years by the number of days in a year, 365. Giving us (Drumroll please!) 734,015 different groups of peculiar children, eleven in each group, making 8,074,165 individual's existing on the same small island, living in the same house, and interacting with each other.
Miss Peregrine was wrong, these Loops aren't safe havens for the peculiar, they're death traps.
-Special thanks to Lupa for suggesting this topic-