Absolute time is the notion of how time flows in the universe before the advent of the formulation of special relativity. Get a description of the concepts of relative and absolute time with help from an experienced physics professional in this free video clip.

### Transcript

Hello, my name is Walter Unglaub, and this is describe the concepts of relative and absolute time. So, first let's mention absolute time. Absolute time is the notion of how time flows in the universe before the advent of the formulation of special relativity. So, with absolute time, we say that in a given inertial frame, meaning no acceleration. So, either in this coordinate system, a person is not moving or moving at a constant velocity. If we compare this frame to another frame of someone walking at a constant velocity, relative to this person. Then the passage of time for each of these people is the same. In other words, the rate at which time flows, in which the clock moves and evolves in time, is the same everywhere in the universe. Regardless of who's point of view you're looking at. This is extremely different than how the universe actually works. In reality, time is relative. And the reason for this is that the speed of light is finite and it's a constant. Regardless of how fast you're traveling. So, because the speed of light denoted by C, is not infinite but rather is finite and is the same in all inertial frames. Then let's do the same comparison. I have my lab frame. So, we have a person with a watch and they observe the frame of someone traveling at some finite velocity V. But let's say that this velocity is very large, close to the speed to light. It turns out that some interval of time in the lab will not be the same as some interval of time observed in this frame from the lab's point of view. If we want to know by how much these differences in time vary. Then we can actually write down an equation after several formal derivations. Where we see that the amount of time that has stretched in this frame, from the lab's frame point of view. Is equal to a factor gamma times delta T-two. Where this gamma factor is equal to one over the square root of one minus the velocity squared divided by speed of light squared. So, we see that this velocity approaches the speed of light, than this denominator will start to get smaller and smaller. Meaning gamma becomes larger and larger. That means that this time is being dilated. So that the rate at which time flows is much larger, much slower in this frame when viewed from this lab frame. So, we see that time is relative. And this is due to the aforementioned reasons where the speed of light is finite and the same in all frames. My name is Walter Unglaub, and this is describe the concepts of relative and absolute time.