# B So time is the 2nd dimension

1. Aug 10, 2016

### mmmchicken

Because it takes time to get from one point to another?

2. Aug 10, 2016

### Staff: Mentor

Usually it is considered the 4th dimension, since there are 3 spatial dimensions.

3. Aug 10, 2016

### Staff: Mentor

It also takes time when you don't move. Dimension means that one cannot be converted into another. You could replace time by velocity (preferably that of light in a vacuum), but you cannot replace length by time or vice versa.

4. Aug 10, 2016

### jack476

Basically, yes. We can hypothetically set up a coordinate system where three of the axes represent locations in space and an additional axis represents a "location" in time. That gives rise to the notion of the interval, the separation in both space and time, which unlike spatial separation is not observed to be different by observers with different velocities.

5. Aug 10, 2016

### mmmchicken

How can there be time with no movement? There's nothing to measure?

6. Aug 10, 2016

### Staff: Mentor

Your heartbeat measures time. An atomic clock measures time, and it doesn't move at all (relative to the earth's surface).

7. Aug 10, 2016

### mmmchicken

Why isn't this preferred?

8. Aug 10, 2016

### mmmchicken

not measuring but confirming