Does Anybody Really Know What Time It is?

Past, present, and future get complicated when you venture into deep space. But there's a simple way to make sense of them.

As 2024 draws to a close, it seemed like the right moment to complete my trilogy of reflections on the nature of time. You can read part one here and part two here.

You are living in the past.

I am living in the past.

We are all living in the past, and there is no way to avoid it. In fact, the only way to make sense of reality on the biggest, astronomical scales is to accept that the entire universe is living in the past. Once you make peace with that, physics will make more sense and, just maybe, your life will make more sense, too.

As I discussed earlier, the finite speed of light means that all news is old news. By the time light (or any form of information, really, since nothing can travel faster than light) reaches you from an event, some amount of time has already gone by. For anything happening here on Earth, the time delay is easy to ignore. Who cares if you’re hearing about conflict in the Middle East 1/30^th of a second after the fact?

But in the cosmic context, time delays become huge, confusing, and potentially disorienting. For a certain type of online truth-warrior, the ambiguity of past and present becomes downright infuriating. Their solution is to smash the glass and break out the emergency “well, actually” response.

Pretty much every time I write about an upcoming astronomical event somewhere far off in interstellar space (such as the likely impending eruption of the star T Coronae Borealis), the keyboard warriors turn up to set me straight. I talk about the event in relation to human experience, as something about to happen. Someone promptly chimes in with a correction along the lines of, “You mean it happened long ago and we just don't know about it yet!”

I recently posted on social media about the slight possibility that the bright star Betelgeuse might soon go supernova and light up our skies. Right on cue, along came the responses: “So it may have already gone supernova?” “May already have gone.” “It could have already gone supernova.” My colleague Tom Levenson offered a pointed reductio ad absurdum to the conversation. I noted that, most likely, it will take another 100,000 years before Betelgeuse explodes. “Or will have taken,” he replied, before adding, “Timeslines (sic) are a pain in the ass.”

Well said, Tom. There is nothing like astronomical distances and the finite speed of light to make you aware of how nebulous the idea of “now” is. Hey, even the band Chicago got it, in their cheesy way. The peculiar truth is, every perception of the world is a perception of the past. What we call “now” is really the moment that light or other information reaches us.

In everyday life, those the gap between the two is so small that we cannot notice it, but it is always there. Information time lag is embedded into the physics of our existence.

How Soon is Now? (The Astronomical Mix)

When you say, “It's gonna happen now”
Well, when exactly do you mean?
See I’ve already waited too long
And all my hope is gone

—The Smiths

Morrissey and The Smiths got it, too. “Now” is the one and only way we can perceive the world. It is how we move through physical reality, and it is how we experience events and assemble them into narratives that give our lives meaning.

Trying to adopt an God’s-eye perspective on the universe so that you can perceive some unique cosmic “now” may sound clever, but it’s a half-formed concept that (well, actually) leaves you understanding less than you did before you started. There is no master cosmic reference clock, just as there is no master cosmic ruler. The Big Bang provides a common start for all of the observable universe, the whole story beginning 13.8 billion years ago—but it’s neither practical nor meaningful to try to set you watch by it.

Unless you are an omniscient being (which I doubt, but feel free to leave a comment if you have convincing evidence) you cannot observe events across all of space and time. You are stuck in a what-you-see-is-what-you get reality, just like all the rest of us. So why are so many people so eager to fight the idea of living in the now?

The problem, I suspect, is that people don’t like questions; they like answers. Specifically, they like absolute answers that make them feel like they have the big picture. Google Maps has trained us all to expect that we can find any location, anywhere, zoom in on it, and determine exactly how long it takes to get there. When astronomers talk about objects happening in distant parts of the universe, it’s difficult not to picture them as destinations on a Cosmic Maps grid.

Modern cosmology further encourages that tendency to expect that everything in the universe can be described by a well-defined time and place. After all, researchers are constantly studying objects that lie beyond human vision—colliding black holes, swirling galaxy clusters—and measuring their properties, placing them billions of light years away, at times before the Earth even existed. With such sweeping powers of vision, it seems only reasonable to expect that we should be able to extrapolate what is happening “now” anywhere on our Cosmic Maps screen.

If you read those cosmology stories closely, though, you’ll notice that researchers do not talk about the geographic distance to objects in the distant, early universe. They talk about the “light-travel time” or “lookback time.” They are describing how long it took light from that distant object to travel to Earth. Put another way, they are measuring the amount of elapsed time between the “now” we are living in and the “now” of the object they are looking at. It’s a relative answer, in a universe that is defined by the rules of relativity.

Like or not, that’s the only kind of “now” we get. Sometimes journalists like to play cute with these terms and extrapolate how far away a distant galaxy is today, as if that were some kind of meaningful idea. But an imaginary extrapolation of something that you cannot see and cannot ever know accurately is not meaningful. It is a kind of fantasy. Reality is seeing things as they are, even as we know that all of the “nows” you can see are visions of the past.

Taking inspiration from Morrisey and The Smiths, I argue that the only way to avoid disappointment is to make peace with the “now” you’ve got, and stop obsessing about “nows” that you will never experience.

In the case of Betelgeuse, that bright star in Orion shining high in the south on a winter night from the U.S., we can say that it has not exploded yet from our perspective. At some point in our future, Betelgeuse will blaze as a brilliant supernova. At some point farther in our future, it will have completely faded from view. It is irrelevant if some of those events are already in the past from other perspectives. The only sensible way to define the timing of an event is by the moment when its information reaches you.

That “now” has not yet arrived…but it could soon, and when it does, it will be spectacular. The illustrations above show what Orion will look like someday in the future.

All this temporal philosophizing has immediate, personal implications. Earlier I wrote that you are living in the past, but I myself was playing some games with time when I said that. The “now” that you and I perceive is always at least a little out of date, but it’s the only “now” we have to work with. It’s the only one that matters, the only one that requires a response.

Does anybody really know what time it is? Yes, it’s “now.” How soon is now? It arrives at the moment of perception. The time to act—to do good deeds, connect with friends, make amends, be creative, express love, experience joy—is not connected to some theoretical time in the past or future, or to some imaginary and out-of-sight location. There is no clever gotcha that gets you out of the moment and allows you to play God.

The time for action is always, simply, “now.”