I have a science degree in mathematics and am very familiar with the concept of infinity. It is very useful but very hard to explain. The simplest way I can think of is that something just keeps going, without limit. Some things have a fixed starting point and extend infinitely away from it e.g. a single beam of light. Sounds simple, doesn't it and could apply to the universe or to time itself.
However, even light is not that simple. Light has all the properties of radiation but it also has properties that match a stream of particles, all travelling in the same direction. How can it be two things at once. It isn't. It is the one thing but our ways of explaining it are clumsy. Some of us are now just content to look upon light as one of the marvels of the universe, to appreciate its wonder and beauty and be grateful. Without light our planet would be nothing but death.
I don't think, science notwithstanding, that we fully understand the concept of time either. We measure it, plug values into equations and we know that our lifetimes are finite but what about time itself? Is time infinite and if it is, is it infinite in both directions? We have a word for infinite time - eternity. Since I have a weak understanding of infinity, I cannot even begin to understand what eternity would look like.
So, I don't waste any time trying to understand such lofty concepts. I do know that I am alive now and I know that the sun is very likely to rise in the East each morning giving me an allocation of time and I hope to spend most of it experiencing beauty and passing on some intangibles to my family and other humans I may encounter each day. A friendly smile, a helping hand or just a small slice of my time.
I know that i sound rather like I am preaching but I am just trying to explain to people who find ideas of creation, big bangs, multiverses and other challenges to the mind really important, that everybody doesn't share the same passionate interest. This is not a criticism. It is just a difference in perspective.
Over, and out.