LOVE OF PHYSICS & COSMOLOGY

“A Paradox of time travel that occurs when a future event is the cause of past event, which in turn is the cause of the future event. Both events then exist in spacetime, but their origin cannot be determined”.                                                   When you hear of time, you often think of this intangible concept advancing single-fold into the future. The idea that time keeps passing outside of our control is almost self-evident with the circular motion of the moon around the earth, and the earth around the sun. The tools with which we measure time have become so sophisticated and duration is now recorded with such precision that one can hardly doubt the reality that the time is constantly advancing. Yet beyond our universe, the concept of time doesn’t exist since time is inextricably linked to space and none can exist without the other. But is time ...

If you were asked to describe how you can move through the Universe, you'd probably think of all the different directions you were free to move in. You could go left or right, forwards or backwards, and upwards or downwards; that's it. Those three independent directions, described by something as simple as a grid, describe all the possible ways once can move through space. But those three dimensions are far from all there are. There's a fourth dimension that's just as important, even though it's very different: time. We're always moving forward through time, sure, but it's just as much a dimension as any of the spatial ones. Whether you say we live in a four-dimensional Universe described by the fabric of space-time, or a 3+1 dimensional Universe, where we have three spatial plus one time dimension, you cannot separate these entities from one another while still being physically correct. Let's try and understand why.                   ...