# How can time be a dimension

1. Nov 8, 2014

### MichaelH

How can time be a dimension, if it is a human construct, to measure the rate of change?

I'm only in high school, sorry if this is a silly question

2. Nov 8, 2014

### Bandersnatch

Hi MichaelH, welcome to PF!

Why won't you tell us what is your understanding of a dimension first? Before you formulate your answer, consider that one could ask a similar question to yours: "How can length be a dimension, if it is a human construct, to measure the distance?"

3. Nov 8, 2014

### MichaelH

My understanding of a dimension is a property of an object that is measurable in units.

However doesn't time depend on things changing, because in theory if everything stopped moving/changing time would be still. However the dimensions of length, breadth and hight are independent of each other.

I'm just trying understand.

4. Nov 8, 2014

### Fredrik

Staff Emeritus
The mathematical definitions (there are several of them) are more like "the number of numbers required to identify a point". A point in space (a location) is identified by three numbers. A point in spacetime (an event) is identified by four. That's really all there is to it.

Physicists also use the word "dimension" for something that does have something to do with units. They say things like "v has dimensions of length divided by time" to indicate what sort of units they intend to use.

The word also means something in plain English, something that doesn't have a lot to do with mathematics or physics. For example "the dimensions of this box is 30 cm × 50 cm × 15 cm".

5. Nov 8, 2014

### Staff: Mentor

It is not a human construct. Using the word "time" to refer to it is a human construct, but the thing that the word refers to is not. Same with "dimension".

6. Nov 8, 2014

### Doug Huffman

Perimeter Institute cosmologist Lee Smolin asks the same question. You will be able to understand his popular books on the subject.
I am a sustaining contributor to the Wikimedia Foundation.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook