Does our universe have a 4th dimension?
Yes, our universe has a fourth dimension which is time.
The universe was until just over a century ago considered to have three dimensions of space. Time was considered an independent variable which flowed at the same rate from past to future for everyone. Isaac Newton built his laws of motion based on this.
In the late nineteenth century it was found that this model didn't work. Time can't pass at the same rate for everyone. This was the foundation for the theory of relativity.
Relativity describes the universe as a four dimensional spacetime with time being the fourth dimension. This means that space and time are linked
The consequence of relativity are somewhat bizarre. Time passes slower the faster you travel. Time also passes slower the stronger the gravitational field is.
Now we have to think of events being positions in four dimensional spacetime. We are all travelling at almost the speed of light along the time dimension!