Time flies like an arrow. Fruit flies like a banana.
Hello! It’s me, Boop! I’m the Discovery World Spokesturtle. It’s July! I know, right? I don’t know where June went either. I saw it outside just a minute ago, and it was doing really well. I turned my back for a moment, and it was gone. June happened, right? June was a thing? May took forever, but May always takes forever. Anyway, June will probably turn up again at some point. July is here!
What have Beep and I up to this week? We’ve been… waiting. We are waiting for Summer Camps at Discovery World to start. We are waiting for Discovery World to reopen. The waiting, as singer-songwriter and musician Tom Petty said, is the hardest part. And the Aquarists said they were bringing us a snack, so we are waiting for our snack. Soon, they said. What is soon? How long is soon? You can’t measure soon. Time is weird.
And it’s not just weird now. Time has always been weird.
Let’s say you’re at a friend’s house. You each have the same astonishingly accurate and precise watch. Because you’re friends, you sync your watches precisely. It’s time to go, so you hop on your bike and race home as fast as you can. When you get home, your watch and your friend’s watch are out of sync. Not by much – less than a quadrillionth of a second, maybe – but a measurable amount. The flow of time depends on how fast you’re going relative to your friend. You were going faster, so less Time passed for you and more Time passed for your friend.
The flow of Time changes with gravity, too. Let’s say you are falling into a black hole (so much gravity). For you, Time would pass by at its usual pace of one second per second. Lots of horrible things would be happening, including something called spaghettification, but Time would seem to be passing by at its usual rate.
If I watched you fall into a black hole, Time would slow down. Not for me. For you. From my perspective, Time would slow down so much that you would never reach the event horizon of the black hole. Of course, I would not simply watch you fall into a black hole. I would leap into action and try to save you from falling into a black hole! I have no idea how I would do that, but I would do my best!
Anyway, Einstein figured all this out, and it’s more complicated than that, but so is everything. But this is not the weirdest thing about Time. The weirdest thing about Time is that no one knows what it is.
Okay, in a very real and obvious (and important but sort of boring) sense, Time is what clocks measure. A second is 1/86,400 of one day, which is what you get when you multiply the number of hours in a day by the number of minutes in an hour by the number of seconds in a minute. That’s clock time. Clocks measure the periodic oscillation of a thing – a pendulum, a quartz crystal – and translate that into seconds, minutes, and hours.
Science Time is a bit different in that it’s the same but more precise. In 1967, the second was defined by the International Bureau of Weights and Measures at their 13th General Conference of Weights and Measures as, “the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom.” That’s science time. It’s always science time at Discovery World!
So everyone knows what Time is. Maybe it’s better to say that no one really knows why Time is the way it is.
Space is easy. We get space. We move through the three dimensions of space all the time, everywhere we go. You can walk to your friend’s house at the top of a hill. You can walk back to your house at the bottom of the hill.
Your friend’s house is located in Time. It has a duration. It wasn’t before. Then it was. It is. It will continue to be. And then at some point in the future, it won’t be. And there are time coordinates just like there are space coordinates. Your friend invites you over to her house at a specific time (10am, say), and you show up at that time. It would be rude not to.
But we can’t move around in Time in the same way that we move around in space. You can go back to a point in space. You can’t go back to a point in Time.
But why? Why does Time seem to happen in only one direction? Why can we remember the past but not the future?
Physicists talk about entropy and the arrow of Time. You can’t unscramble an egg or unmix the cream out of your coffee or unchew a mealworm. That sort of thing. Some physicists, though, believe that Time and entropy might only seem like they’re related, but that Time doesn’t happen because of entropy.
Some physicists think that only the present is real. Some physicists think that the past and present are real, but not the future. Some physicists think that the past, present, and future are all real.
And a few physicists think that at some point Time will end. According to these physicists, the reason it seems that the expansion of the Universe is accelerating is not because of Dark Energy. It’s because Time is slowing down. One day, Time will stop and the Universe will freeze. As terrifying (and probably untestable) as this hypothesis might be, it would happen billions of years from now. So not something to worry about. Also, they could be wrong.
Physicists and other scientists like biochemists, biologists, archaeologists, geologists, paleontologists, and astronomers work in different scales of Time. Physicists might work in tiny, tiny timescales – from yoctoseconds to femtoseconds and nanoseconds. And then there are the centuries, millennia, galactic years, eons, and increasingly larger chunks of Time that archaeologists, geologists, and astronomers work in.
The fastest chemical reactions in the body happen within a few quadrillionths of a second. That’s super-fast. Proteins fold much more slowly, within microseconds and milliseconds.
Mayflies live for 24 hours. Greenland sharks can live for around 300 years. There’s a bristlecone pine in California that is 4,851 years old. That’s about as old as the Great Pyramid of Giza, I think. Glass sponges (marine creatures) can live over 10,000 years. There is a clonal colony of quaking aspens in Utah that is around 80,000 years old. As an order, turtles have been around for something like 220 million years.
Rocks are even older than turtles. Well, some are. There are plenty of rocks that are “being born” right now. But there are rocks and rock formations in Baraboo, Wisconsin that are around 1.8 billion years old. They are part of the Baraboo Range, a very old mountain range that has eroded slowly over nearly two billion years. Devil’s Lake State Park is part of the Baraboo Range. And the oldest rocks on Earth are older than the Earth. They came from outer space. They were meteoroids, once upon a Time.
Us turtles don’t really understand infinitesimal slivers of Time like nanoseconds or femtoseconds. Nor do we truly understand vast swaths of time like millennia or galactic years. Our lives are made of hours, minutes, and moments. Our lives are made of firsts. And lasts. And all the wild, beautiful, and heartbreaking adventures in between. We measure our lives in seasons and stories.
Each of us turtles has a place in Time. We are part of a generation, one of a few generations of turtles living on the Earth at the same Time. And as we grow up and grow older we watch ourselves and the world change from our different places in Time. We watch new generations come and older generations go. Our responsibility is to make sure the story continues.
I’d like to think that the past is very real. We can’t physically go there, but all of turtle (and human) history is out there for us to explore and puzzle out and learn from. We can explore the history of Earth over billions of years. And the history of the Universe over billions and billions of years.
I’d like to think that the future is real, too. We just have to build it.
I’d also like to think that the Aquarists will be here soon with our snack. And here they are! They’re so awesome.
You’re awesome, too. And Beep and I will see you… soon.
Oh! And watch out for turtles on the roads! We’re not as fast as your cars. Thank you!