Nothing. Time still passes even if objects stop moving.
So, even if the Universe stopped expanding and the planets stopped rotating, time would still go on. Similarly, whether you’re standing still or moving in a car, time will just continue.
I think that this question might have come from someone learning about Einstein’s Theory of Relativity, and the idea that clocks run at different speeds when you’re moving. While it’s true that, when you’re moving extremely fast, your clock moves at a different rate than when you’re standing still, time will still keep moving forwards.
An explanation of Einstein’s theory of relativity
What Einstein’s theory is trying to describe is what happens when things move at the maximum speed possible – which is the speed of light – and what happens when the force of gravity is very strong.
"The whole of 20th Century technology would not have been possible without the understanding of Einstein’s Theory of Relativity from the beginning of the 20th Century."
In terms of a simple explanation of how the theory works, I’d say that we have a lot of intuition about what happens when objects move at normal speeds – such as a car driving along the road – but when things are moving at speeds approaching the speed our light, our everyday intuition fails.
When objects move at speeds close to the speed of light there are many unusual effects relative to everyday experiences. For example, if you’re moving extremely fast, then your clock slows down relative to people who are not moving.
Einstein’s Theory of Relativity plays an important role in many aspects of contemporary life. For example, with UPS positioning systems it’s extremely important that they take into account the relativistic effects of gravity – or the GPS wouldn’t give correct positioning. An understanding of objects moving at or near the speed of light is absolutely crucial for modern technology.
Many things we use rely on understanding and being able control electromagnetic radiation – which includes radio waves, microwaves, X rays, visible light… all these kind of waves move at the speed of light. So when you use a mobile phone, that relies on electromagnetic radiation, while radar relies on radio waves.
The whole of 20th Century technology would not have been possible without the understanding of Einstein’s Theory of Relativity from the beginning of the 20th Century.
Michael Emil as 'The Professor' and Theresa Russell as 'The Actress' in a scene from Nicolas Roeg's 1985 film Insignificance.