I’m reading a lot these days. I’ve been totally ignoring my favorite fictional authors for quite a while and have been focused instead on a number of different authors who write about two topics of special interest to me: time and space. It’s like an addiction. I can’t get enough. Mind you, I don’t really think that’s a bad thing because I’m having way too much fun to quit. No, any concern I have simply pertains to the rate at which I am consuming the material.  I worry about how much I am missing, not retaining. This material can be tough to get your head around, at least for me. To guard against this, I’m approaching reading these books like my wife and I approach traveling the world; that is, we view the very first visit to a new place more as a scouting mission than a single event vacation, knowing (or at least, wanting to believe) that we will return sometime to see the place again. This causes us to focus on what we are seeing and doing a little more closely. Thus, I read a science book and then… I return and read it again, hoping something sticks. Hope springs eternal.

I’m enjoying my readings immensely, although as a result, I have had an interesting wake-up call recently. It’s not due to my having necessarily read something new, because I am positive I have been told the same information previously, probably more than once. But this time when I read it, something clicked, and I thought, “Wow, this universe is a whole lot stranger than I realized.”

As a kid and, if truth be told, even as an adult, I have sometimes wondered what was happening at this very moment in time on a planet very far away in a distant galaxy. As I was sitting on the grass and puffing on my pipe while looking at the stars, was there some alien doing exactly the same thing at just the same time on the other side of the Milky Way? I kind of liked this thought. There’s some comfort in it, I think. In any event, nothing lasts forever, and I recently had this reverie shattered big time.

Interestingly, the description of my thought about the alien is a rather common way that people think about such things. It seems to just make sense that we should be able to wonder what some alien is doing across the universe at this exact same moment in time. Doesn’t that sound rational? Well, it may make sense to wonder about it and it may sound rational, but it is still wrong. You see, the universe doesn’t work this way.

Don’t get me wrong. The universe where you can validly wonder what some alien is doing on a planet far away at this exact moment in time did exist at one time. In fact, it was the only universe in town and the way it worked was taught at all the major educational institutions for centuries. I’m talking about a Newtonian universe, of course. This particular universe was all the rage for quite a while, right up to the time of its destruction.

This scenario about the alien is only valid in a universe where there is something called, absolute time. In a universe with absolute time, time exists outside of everything else. Time is independent. Separate. Think of it this way:  Do you believe that if you removed all the physical matter from the universe, time would still go marching on, ticking off the seconds like some disembodied timepiece? If you do, then you believe in absolute time, as did Newton. He believed even if the universe were completely empty, time would still exist. Thus, a second of time on Earth is the same as a second of time on some alien world light years from Earth – when compared to the absolute time of the universe. Although it is true that this is exactly the kind of universe required to fulfill my fantasy about the alien, science tells us that we don’t live in that universe and neither did Newton.

Einstein, of course, was the culprit who rained on Newton’s parade. Einstein’s theory of special relativity, which has been experimentally verified over and over again, shows us that there is no such thing as absolute time. Time is in fact, relative. And in a relative universe like the one we live in, the very question, “What is the alien doing at this exact moment across the universe?” is nonsensical, because your moment and the alien’s moment will never be the same. The alien’s experience of time and your own will always differ. How much they differ depends on how fast you are moving relative to the alien. For my benefit, more than yours, let me try to explain with another analogy:

Let’s say you’re Wiley Coyote, sitting in your backyard on January 1, 2018, staring out at the stars above. Suddenly you see the star, Polaris, explode at exactly midnight. You continue to watch. One hour later, at 01:00, you observe the star, Betelgeuse, exploding. Wow!

Excited by these developments, you call up your good friend, Mr. Roadrunner. He tells you that at midnight he just happened to be speeding past your house at 99% the speed of light and he agrees with you that Polaris exploded at exactly 00:00 on January 1^st. But, he also swears on his mother’s grave that Betelgeuse exploded at exactly the same time as Polaris, not an hour later. Huh? Wait a minute. You clearly observed an hour difference between the two stellar events, but Mr. Roadrunner says there was no time difference at all! How can this be? You can’t both be right, or can you?

The answer, according to Einstein and relativity, is that yes, you can both be right.

What is meant when scientists say that time is relative is that the passage of time depends on how fast you are going. You don’t notice time passing any differently (in your own frame of reference, time passes at one second per second as usual), but when you compare clocks with someone else who was moving at a different speed than you, that’s when things get weird and you notice your clocks don’t match.

As I said above, this is provable science and has been demonstrated over and over again. And it gets stranger. General Relativity teaches us that that the flow of time not only depends on how fast you are going i.e., your velocity, it also depends on your local gravitational field. This means that the flow of time also depends on your position in space! This is why GPS satellites are calibrated to take account of the altitude they are flying from earth and the time dilation effect they experience. If they weren’t calibrated this way, predicted GPS distances on your Garmin unit could be way off and you’d get lost. A 50 nanoscecond difference in time between the satellite and a GPS device on earth can mean an error of 15 meters. An adjustment of 38 microseconds per day is required to keep our GPS units accurate, otherwise we could end up as far as 11 kilometers off our marks!

As an interesting side note, scientists have demonstrated the ability they now have to measure the difference in time between a single stair step! That’s right, walking up the stairs, each stair is higher, thus farther away from the gravity of the earth, so time is different for each step! Fortunately, we are talking time differences so absurdly minute (picoseconds) that we don’t notice any difference, not until we start moving really fast.

So, time being relative means that when you compare notes with someone regarding the passage of time, they will only agree with your clock if you have both been in the same frame of reference (say, sitting in the backyard).

So much for my childhood fun thinking about the alien. Sorry, Newton, but absolute time does not exist! I won’t go into it here, but be aware that Newton also believed in absolute space. Similar to absolute time, absolute space meant to Newton that if you removed all the matter from the universe, space would still exist. Separate, independent. You probably have already guessed that absolute space is also not true. It doesn’t exist. It’s safe to say that Einstein’s theories have shown us that when it comes to the universe, it is literally everything there is and nothing else. Nothing exists outside the universe! And we measure both time and space relative to other stuff that exists within the universe.

This revelation made me feel a bit like the “overfed, long-haired leaping gnome” reaching for his pearl (most everyone should get this song reference, I would think). It was eye-opening and added to the mystery that so attracts me to theoretical physics. What an amazing universe we live in! Newton was scarily smart, even though he got some things wrong. For Newton, both absolute time and space existed on their own, outside of the universe.  Einstein nuked both these ideas with his laser-sharp intellect.

Fun stuff to think about.

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