The Now That Never Is

In the classic Mel Brooks’ spoof Spaceballs, the evil Lord Dark Helmet and his henchman, Col. Sandurz, are searching for the protagonist. Frustrated at their lack of progress, they reach for a videotape of the very movie that they’re in. When they arrive at the present scene and see themselves on the screen, Lord Helmet expresses his exasperation, and the following dialogue ensues:

Lord Helmet: When does THIS happen in the movie?

Col. Sandurz: NOW. You’re looking at now, sir. Everything that happens now is happening now.

Lord Helmet: Go back to then!

Col. Sandurz: What?

Lord Helmet: THEN!

Col. Sandurz: I can’t!

Lord Helmet: Why not?

Col. Sandurz: We passed it!

Lord Helmet: When?

Col. Sandurz: Just now!

Lord Helmet: When will then be now?

Col. Sandurz: SOON!

As always, humour is the perfect way to communicate our frustrations with difficult concepts. In this case, the brilliant Mel Brooks made a quick joke out of one of the most perplexing concepts we experience: the very act of experience itself, the now that makes up the ever-passing present.

Philosophers, scientists, artists, poets, and theologians have all grappled with the meaning of now. And we really haven’t made much more progress than Spaceballs.

The asymmetry of time, also known as the arrow of time, is one of the most perplexing aspects of reality.

The Now that Defines

At first glance, the concept of now seems utterly simple. What we call the present is the inflection point between past and future. We remember the past, and have access to it via our memories, but we don’t know what will become of us in the future. As we glide along, moving forward in time, the future becomes the past at the precise moment of the present.

Indeed, this is encoded in physics through the concept of the event. Physicists understand that our universe consists of an imaginary four-dimensional grid called spacetime, an interwoven fabric of three dimensions of space and one dimension of time. All of physics – collisions, decays, interactions, everything – happens on top of that four-dimensional stage.

This allows us to specify a precise point for every single occurrence. This is the event: a four-dimensional address in the fabric of spacetime. If we bump into each other on the sidewalk, we can assign an event to that interaction: it happened at a specific place in space, and a specific moment in time.

From this language, we can construct what now means. For example, I am sitting at my desk typing this article. My location in space is fixed – I’m at my chair (well, to be pedantic, the Earth is spinning and orbiting the Sun, our Sun is orbiting within the galaxy, and so on, but let’s leave that to the side for the sake of simplicity). Every strike of my finger against the keyboard can be marked by an event: the time I hit the ‘t’ key, followed by the time I hit the ‘I’ key, and so on.

In four-dimensional spacetime, this sequence of points stretches to become a line, stretching from the past to the future. This is my worldline, the path I take through both time and space.

As I age, as I move forward in time, I advance along that worldline. The now is my current position in time on that worldline, with the (known) past stretching behind me and the (yet to be known) future stretching ahead. The now is as simple and straightforward to define as my current position in space – it’s right here.

The Now that Enforces

But there is something different about the nature of time. We can choose wherever we go in space – left or right, up or down, forward or backwards – but we must go into our futures, and we can’t go into our pasts. The asymmetry of time, also known as the arrow of time, is one of the most perplexing aspects of reality.

When it comes to time, we’re stuck on a train that always moves forward. The lack of agency when it comes to our experience of time is deeply frustrating. As physicist Lee Smolin put it, “The world is presented to us as a series of moments. We have no choice about this. No choice about which moment we inhabit now, no choice about whether to go forward or back in time.”

Or, as Tom Stoppard put it bluntly in his play Arcadia, which explored the nature of time, “You cannot stir things apart.”

The now then becomes the gatekeeper, the filter that takes the many branching possibilities of the future and prunes them to become the single line of the past. Just like geometric points in space have no volume, the now in time has no extension. It is fleeting, ephemeral, and temporary. We are constantly experiencing a sequence of nows, each one advancing into the next, but each one as brief as the last.

We have long grappled with the dual nature of the now. It is, on one hand, the only thing we can truly hold onto, because the past is no longer accessible, and the future is only hypothetical. As the Argentine writer Jorge Luis Borges said, “Everything happens to a man precisely, precisely now. Centuries of centuries and only in the present do things happen; countless men in the air, on the face of the earth and the sea, and all that really is happening is happening to me.”

Yet despite its concreteness – it is perhaps the only thing about time that we can really call real – it slips by us as quickly as it comes. We know the now, well and truly in our hearts, and experience the passage of time within ourselves, but also know that it passes by. As the American philosopher Rebecca Goldstein put it, “Is there anything we know more intimately than the fleetingness of time, the transience of each and every moment?”

The Now that Divides

So, we can establish a personal, intimate relationship with the now. I can draw my worldline. I can point to times in my past and recall them as once being my present. There used to be a now, and it no longer is. I can think about possible events in the future and wonder if they will someday become a now. I can feel the flow of time, sometimes quickly and sometimes slowly.

But can we broaden this concept beyond the personal? Can we agree on a universal now? Can establish a common, mutual frame of reference for dividing up time?


We know from Einstein’s special theory of relativity that there is no such thing as a universal now. The world of pre-Einstein physics was dominated by Isaac Newton’s revelations on the nature of forces and the universality of gravity. But to keep his mathematics consistent, Newton had to assume the existence of a universal reference frame.

There was, in his reckoning, somewhere out there in the imaginary aether, a master clock ticking away. This master clock kept absolute time, a perfect rhythm to underscore all movements, all interactions. No matter where you were in the universe, you could rely on that universal clock to provide a common now that everybody could agree on, like the music cuing a dance.

Einstein put that right in the trash. This is the point of relativity. Einstein discovered that you could either have universal sets of physical laws, or universal frames of reference, but not both. And since physical laws appeared (and continue to appear) universal, the master clock had to go.

Different observers will have different measurements of the flow of time. A year for you, sitting on the surface of the Earth, will only be a few seconds for me, if I’m traveling close to the speed of light. This is not some trick of perception or impression; it’s grounded in the very nature of reality itself, the same spacetime that gives us the framework of our experiences. Two different observers, traveling at two different speeds, will disagree about the length of time between two events.

It gets worse. If two events are separated widely enough in space, different observers can also disagree about the ordering of those events. Let’s say you’re sipping tea when a distant supernova goes off. To you, the supernova occurred after you took a drink. To an observer whizzing by this region of the universe in a rocket at close to the speed of light, you took your drink before the supernova went off.

This is called the relativity of simultaneity, but I like to call it the death of the universal now. I have my now, you have your now, and we will never, ever agree. Yes, we can use Einstein’s math to translate from one reference frame to another, but I can never replicate your experience, your flow of time, from my point of view.

The Now that Deceives

This intense intimacy with regards to the now invites another potential line of thinking. Perhaps what we call the flow of time, what we call the sequence of nows, is an illusion, something crafted within our brains.

Perhaps then the expanse of time exists in the same way that the expanse of space exists. It’s just… there, existing. This is known as the block universe, where the entire four-dimensional hunk of the cosmos, past and present, is already there. What we call the now is an artifact of our consciousness, and what we call the passage of time is nothing but.

In this view, there is nothing special, nothing real, about the now. It has no more consequence than any random point in space. It’s arbitrary. As James Gleick summarized in his book Time Travel: A History, “The future is just like the past, you can see it in the mind’s eye, neatly diagrammed. Our experience to the contrary is merely a product of mental states, memories, perceptions, and anticipations.”

This point of view is bolstered by the fact that almost all equations in physics do not have a built-in sense of the arrow of time. Now can be anywhere for physics, and past and future are interchangeable. On the brain side, all our sensory inputs – sight, sound, touch, smell, etc. – occur at different intervals, and are constantly out of sync. And yet, somehow, we can construct a now – perhaps because there is nothing to the now outside of what happens in our brains.

In other words, if physics doesn’t care about the flow of time, then why do we?

What all this means for the concept of free will, I will allow the reader to decide.

The Now that Creates

But this is not the end of the story (or this article).

There are some aspects of physics that do seem to have a built-in arrow. Some interactions involving the weak nuclear force are not symmetric when reversed in time, for example, and the whole concept of thermodynamic entropy introduces a seemingly natural temporal ordering into the cosmos.

And while relativity tells us that every now is a personal one, unique to each observer, it doesn’t banish the concept entirely. Events still occur and have significance. Cause still leads to effect. Actions have consequences.

And all the while, we still have to explain why we remember the past, and not the future.

So here we are, back where we started. We’re not sure if time exists outside of ourselves, or if it’s created within us. We’re not sure if the ‘now’ is a construct of our minds or a consequence of reality. We’re not sure if the future already exists, or if the now has the power to turn it into the past.

But we do know something. Whether the now is within us or external to us, it can still be real, and still be powerful.

The American singer-songwriter Patti Smith, in a collection of short stories titled M Train, asked, “Is only the present comprehended?” There is something special about the present that sets it apart from both the past and the future. The now gives us the opportunity to build, to create, to remember, and to make real.

In meditative practice, we are asked to ‘center’ and seek ‘grounding.’ We are instructed to live in the moment, exist in the present, not dwell on the past or overly worry about the future. If the now doesn’t exist, then why bother?

The poet T.S. Eliot found a certain kind of magic here, in the present, “at the still point of the turning world,” where “Except for the point, the still point, there would be no dance, and there is only the dance.”

According to the American writer William Faulkner, “The aim of every artist is to arrest motion, which is life, by artificial means and hold it fixed.” While for Russian novelist Vladimir Nabokov, “Time is but memory in the making, and by telling stories we can stop time.”

The present, the now, gives us the power to create. From the past, we can bring forward memories, stories, artifacts, and they can still exist. We can imagine future possibilities and plan for them, fear for them, delight in them…and they can exist before their time. The now, whether it exists outside us or not, whether we can all agree on it or not, is that ever-shifting point at which we live, and at which reality becomes real.

Or, as Col. Sandurz put it, “Everything that happens now is happening now.”

About the author

Paul M.Sutter is a research professor in astrophysics at the Institute for Advanced Computational Science at Stony Brook University and the Flatiron Institute in New York City. He is also known around the world as the host of several shows, such as How the Universe Works on Science Channel, Space Out on Discovery, and his hit Ask a Spaceman podcast. He is the author of two books, Your Place in the Universe and How to Die in Space, as well as a regular contributor to, LiveScience, and more. Journalists frequently seek his expert advice, especially in his role as the Weather Channel’s Official Space Specialist. In addition to his traditional science outreach, Paul also explores innovative science and art collaborations, such as his work with Syren Modern Dance in Ticktock, a performance exploring the nature of time through movement and narration.

Check out his website at:

For social media, find him on twitter and his social handles are @PaulMattSutter on all channels.