In the 5th century BC Greek philosopher Parmenides proposed that the universe was not made of many things, but rather is a single indivisible substance, an eternal now that encompasses all time and all entities.

And if the universe is one, then all change is impossible, for the very idea of change suggests something transforming from one state to another, but since according to Parmenides all states occur simultaneously, change is impossible.

After receiving heavy criticism from his contemporaries, Parmenides' student Zeno of Aelia came to his defense by creating a series of paradoxes that seek to prove that time and change are, in fact, utter nonsense.

Consider a situation in which a motorcyclist races a man on foot.

Let's assume the man is given a 50 meter head start.

By the time the motorcyclist reaches the 50 meter mark, the man will have moved a small distance forward, and when the motorcyclist catches up to the ensuing spot, the man will have moved farther still.

If there are an infinite number of measurable distances between any two points, the man will always be a minute distance ahead of the biker.

This then will go on indefinitely, and the biker will never catch the man.

But this is absurd, for our perceptions tell us the motorcyclist would quickly overtake the man.

Therefore, Zeno's paradox tells us that our perceptions are flawed, and that a change in distance is preposterous.

In another of his paradoxes, Zeno talks of an arrow being shot at a target.

If it takes the arrow one second to travel 60 feet, it would take 0.5 seconds to travel half that distance, a quarter second to travel half that distance, and so on.

If this process continues, we will eventually reach a unit of time during which the arrow will occupy a space at complete rest.

Let's call this unit of durationless time a moment.

If the arrow's trajectory is the sum of these stationary moments, then how will the arrow ever reach its target?

And thus, motion is nonsensical.

Zeno's paradoxes have challenged scholars, philosophers, and mathematicians for over 2,500 years.

If nothing else, they force us to continuously reconsider our reasoning about the nature of space and time.