On the model of Halliday's Systemic Functional Linguistic Theory, the single dimension of time can be understood as circumstances of the unfolding of processes: location and extent (duration or frequency).
On the model of Einstein's General Theory of Relativity, intervals of time, the distance between two temporal locations, are not uniform across the Universe, but are either relatively contracted or expanded (dilated). On the one hand, the cosmological expansion since the Big Bang is the ongoing relative contracting of time intervals. On the other hand, the presence of matter has the effect of relatively expanding time intervals — not "curving" time — with the distance between temporal locations increasing with relative proximity to the centre of mass. (The limiting case is the singularity of a black hole, which is the expansion of time intervals to ∞.)
To relate this to the unfolding of processes, a useful example is the ticking process of a clock. If time intervals are relatively contracted, then there is less time between successive ticks, which means that the clock is ticking relatively faster, which means that all processes are unfolding relatively faster. If time intervals are relatively expanded, then there is more time between successive ticks, which means that the clock is ticking relatively more slowly, which means that all processes are unfolding relatively more slowly.
The gravitational expansion of time entails that someone at sea level ages relatively more slowly than someone on a mountain top, since all their biological processes unfold relatively more slowly than the person further from the Earth's centre of mass. It also entails that there is no unfolding of processes at the singularity of a black hole, since a process would take an infinity of time to unfold.
For clear thinking, it is important to distinguish time from the processes that measure and are measured by it. For example, time doesn't run relatively faster or slower, processes do; time (like space) doesn't flow, processes do.
Time differs from the three dimensions of space in an important way: there is locomotion in space, but not in time. It is possible to travel from one spatial location to another, but not from one temporal location to another. To "travel" from 1pm to 2pm is merely to endure for one hour. That is, the notion of time travel derives from a category error: that time is precisely the same type of dimension as space.
To relate this to the unfolding of processes, a useful example is the ticking process of a clock. If time intervals are relatively contracted, then there is less time between successive ticks, which means that the clock is ticking relatively faster, which means that all processes are unfolding relatively faster. If time intervals are relatively expanded, then there is more time between successive ticks, which means that the clock is ticking relatively more slowly, which means that all processes are unfolding relatively more slowly.
The gravitational expansion of time entails that someone at sea level ages relatively more slowly than someone on a mountain top, since all their biological processes unfold relatively more slowly than the person further from the Earth's centre of mass. It also entails that there is no unfolding of processes at the singularity of a black hole, since a process would take an infinity of time to unfold.
For clear thinking, it is important to distinguish time from the processes that measure and are measured by it. For example, time doesn't run relatively faster or slower, processes do; time (like space) doesn't flow, processes do.
Time differs from the three dimensions of space in an important way: there is locomotion in space, but not in time. It is possible to travel from one spatial location to another, but not from one temporal location to another. To "travel" from 1pm to 2pm is merely to endure for one hour. That is, the notion of time travel derives from a category error: that time is precisely the same type of dimension as space.