# How can you best define the concept of time? How can we say that time started after the Big Bang? How did this arbitrary concept first come about?

Mar 13, 2018

Time is a very slippery concept.
Are you wanting a concept based on the "conventional"?
Or are you willing to consider radical ideas?

See below references

#### Explanation:

See this: http://www.exactlywhatistime.com/

Check this out: $\text{There Is No Such Thing As Time}$

https://www.popsci.com/science/article/2012-09/book-excerpt-there-no-such-thing-time

Time can get very philosophical !!

Mar 15, 2018

Time is the fourth dimension of four dimensional spacetime.

#### Explanation:

Time used to be thought of as an independent variable. It was considered that time passed at the same rate for all observers. It went linearly from past to future. This is the Newton model. Velocity is distance divided by time. So, time as a concept is the interval between two events.

This model was proved incorrect. Relativity describes the universe as four dimensional spacetime. Time is the fourth dimension. Every object has event which are points in spacetime. The distance between event is both spacial distance and the time interval between events.

Different observers each experience time passing at the same rate. Observers also observe time passing more slowly for others who are travelling at high speed or in a strong gravity field.

As time is a dimension of spacetime, it makes no sense of saying "before" the big bang. Spacetime came into existence at the big bang. So, time came into existence at the big bang.

Mar 19, 2018