It has been well stated that the radius of the observable universe is about 45 billion light years across in current time, but that the outer edge of the universe is expanding about 3.5 times faster than the speed of light. Layman discussions of this situation is that it is not the light at the edge of the universe that is moving faster than the understood speed of light, but that the space itself is moving the stuff that makes up light at a speed faster than that light stuff itself would move on its own.
The edge of the universe is supposedly expanding. A concept that helps explain how scientists detect this is what is called redshift. Scientists are able to determine the intensity of light and use that intensity to speculate on how far or close that light is. They have examined this concept for a long time and pretty much have it nailed down. Based on conclusions (in a more complicated process) about the properties of light and other things, they are able to determine based on observations of light coming this way towards Earth that the universe is such and such a size.
A question I haven’t seen asked yet (because I haven’t looked hard enough) is if space is expanding, what is it that space is expanding into? The universe is said to be expanding, but into what is space expanding? What exactly is beyond the visually observable universe? We seem to be seeing things in the universe, using advanced equipment, that possibly no longer exist. Phantom images of the past like a photograph that finally got developed when you decided to develop it but it still an old image unconnected with the present. It is interesting that there is possibly a part of overall infinite existence that is well outside the observational and mechanical grasp of people.
One of the best technical outcomes from science it seems is to better understand and harness gravity itself and space-time (not that I am advocating such things). I have not seen anything in the output of science and technology that shows the literal harnessing of gravity and space-time. Yet, such things could have far greater impact than fuel based propulsion and energized movement and reception of data. Yet, even if those things were achieved, it would remain the case that there are things well outside the domain of what can be biologically experienced and understood.
Gautier Talks About Life 