Three questions about time

Question

Since I don't want to abuse to the ASK QUESTION form, and since those questions are all about time, I decided to write them all here. Hope it's ok.

First Question

Could it be possible (how?) to create some regions, in the Universe, in which the times seems like to stop (for a little while)? I mean: if we could be able to hide some event from the light, would be able the same to hide it from the time?

Second Question

Since there is a deep connection among observers light and the passage of time, wold the time still exist if there weren't any observer? Why?

Third Question

Isaac Newton introduced the idea of a $t$ variabile, which stands for time, to describe how do objects move. But Quantum Mechanics does consider the time in a very different way with respect upon the Classical view of Newton. Nay, according to the Planck scale units the time variable is not applicable. So shall we come back to Newton's period (and earlier) and try to eliminate the $t$ variable?

Namely: could we reformulate the entire Quantum Mechanics theory/formalism without using the time variable? I read that Carlo Rovelli did something about.. but no clue where to find some material!

Thank you all for the attention. If someone thinks I should split the question in three different ones, just tell.

Answer 1

Question 1:

If a region of space contained no energy (and thus no matter or information), it would not be possible to measure the passage of time in that region. It's important to mention however, that such regions do not exist as there will always be quantum fluctuations.

Question 2:

According to basically all accepted theories, the answer is yes. If everything on earth that can "observe" were to disappear, only to magically reappear 100 years later, we could figure out that it had been 100 years using any number of different methods.

Answer 2

Question1:

If you and your clock are sufficiently close together and in free fall, you are in a local Lorentz frame and there is no way for you to locally tell (such as by seeing your clock slow down) what the mass distribution (ie: different regions of space) is around you.

However, if you put the clock in a region of space that is different than yours, then it is possible to see that clock speed up, slow down, or even approach stopping wrt your clock. For, example put the clock near a black hole and you observe the clock from far away. To you, the clock will appear to slow down or even stop as it approaches the Schwarzschild radius. Conversely, if you were near the black hole and the clock was far away, you would see the clock going faster than your own clock.

Question2:

Since x,y,z,t are part of a four vector, you question about t existing is a question about x',y',z', and t' existing in a boosted frame. So your question is really does all space-time exist, not just t, if there is no observer. Hmmm...kind of philosophy.

Question 3:

I don't think you can eliminate t as a parameter for evolving physical systems because it is unique in always advancing to positive values for observers in all frames as the system evolves.

You could imagine parameterizing the change in all physical systems by the angle of your clock hand in its clockwise advance. However, another observer in a frame rotating a little faster than the clock hand would see the clock hand rotating backward toward negative angle. This exemplifies t as unique (and indispensable in parameterizing the change in systems) in that it only changes toward the positive direction. There is no frame we can transform to in which t reverses direction. You can't get away with just using the angles, boosts, or spatial positions of an object to parameterize evolution.