Picture the biggest thing you have ever seen. And then imagine that thing is so big that it stretches out forever. This object would be infinite. 

Most things we encounter in the world are finite, meaning they have a beginning and an end, a top and a bottom. They have a size that can be measured. If you continually chop something finite in half, eventually you will reach a unit too small to be divided. An infinite thing, on the other hand, can be chopped forever.

This mind-bending concept is the subject of a new documentary, A Trip to Infinity. 

Infinity is difficult to pin down. As physicist Delilah Gates says: "Is infinity a number, an idea, a place? Probably all of the above."

For centuries, the infinite was thought to exist beyond the physical world. In ChristianityA major world religion based on the teachings of Jesus Christ. , only God is infinite. PhilosophersPeople who ask big questions about the meaning of life and how we should live. saw the infinite as something too big for the human mind to grasp.

Mathematicians and scientists, on the other hand, have treated infinite as if it were a number.

Today, thinkers take the idea of infinity very seriously. Space exploration has revealed a universe that might stretch on forever. And the discovery of subatomic particlesThe minuscule pieces of matter that make up atoms. Scientists have discovered 36 so far. has shown that the world could be divided into smaller units than once imagined.

Opinions are divided on whether the world is actually infinite. For astrophysicistScientists who try to understand the contents of the universe. Sara Webb, the universe is always growing. It thus has no end

Others note that we do not know whether this growth will continue. And, as historian Kevin Orrman-Rossiter points out, we can never know: "A voyage of proof would need to be infinite in order to prove... that space is infinite." A traveller into infinity would never report back.

This idea that we can never truly understand infinity is also contested. Physicist David Deutsch believes that humans will eventually learn everything interesting. Some, however, set strict limits on human ability. As philosopher Jennifer Nagel puts it: "We've only got a certain life span. We're going to die, and we think pretty slowly... We can't just say everything is going to be knowable."

Yes: Modern science has made huge strides. But there are many huge questions - the origin of human thought, the true size of the universe, the reason we exist - that remain far out of reach.

No: Time and time again, humans have learnt things that once seemed out of reach. We have gone into space and seen the atoms that make up the world. Who is to say we cannot keep discovering forever?

Or... Humans have limits. But we are a species of makers. We may not be able to explore an infinite world with our own skills. But perhaps, one day, we could create computers that do it for us.