It is commonly believed that time is another dimension like the three dimensions of space that we are familiar with. But while we can move back and forth in both directions in the three spatial dimensions, we are forced to always travel at a constant speed in one direction through time. What makes time special that it only goes one way? Is it just a limitation of our brains? Perhaps we really exist in all times at once but we’re only able to perceive it as traveling forward through time? Or maybe we’re just not given the ability to accelerate/decelerate in the time dimension as we are in the space dimension?

In physics, time is all over the place. Velocity is measured in terms of distance/time or meters per second. In most cases it is assumed that meters and seconds are constant units that don’t change. But what happens when they do change? And if time is another dimension like space then are meters and seconds really the same thing? One second is just some number of meters in another dimension? How many meters = one second?