Immaterial Mortality

 In 1905 Albert Einstein published his groundbreaking Special Theory of Relativity. I've written before about how revolutionary his ideas were. They solved a conundrum that had been bedeviling physicists for several years, regarding the properties of light. Whereas scientists had been considering time to be constant for all observers (regardless of their location or motion), the speed of light was seen as variable, being dependent on an observer's behavior. Einstein proved it to be the opposite. He began with the assumption that the velocity of light would be seen as identical for everyone—regardless of how fast they moved or where they were. The consequence of this premise is that the passage of time is a variable; the march of time depends on your speed... that is, while time is not a constant, the speed of light is.

One commonly-expressed result of his relativity theory is the so-called “Twin Paradox.” Calculations (later proved by measurements) showed that, if one twin takes off on a rocket ship and returns some time later, the traveling twin will be a tad younger than the twin who stayed home. This is very counterintuitive. Time for the traveling twin actually passes more slowly.

These relativistic effects are not usually seen until an object travels at a significant fraction of the speed of light, but it does show up for something that many people use every day: their smart phones, for locating themselves on the planet's surface. The GPS system must use relativistic calculations; otherwise your position would be tens of yards (or meters) in error. Your smart phone directions would have you driving into brick walls or into a lake. Well, sometimes that does happen, but the error can be mostly attributed to human inattentiveness.  

I have made some relativistic example calculations to illustrate the lapsed time for space ships of various speeds to travel to our nearest galaxy (Andromeda) and back.  Andromeda is about 2.5 million light years away. In other words, light would require 5 million years to travel to Andromeda and return... at least that's the elapsed time we observers back on Earth would measure. If time is relativistic, however, what would be the elapsed time for our space traveler at these different speeds? It would be less, according to Einstein; how much less would be a function of how fast the ship traveled. To illustrate this, I have shown the elapsed time in the table below for a spaceship at five different speeds.

Spaceship speed	50,000 miles per hour	0.5c	0.9c	0.999c	C
Round trip time	35 billion years	4400 years	1260 years	120 years	Zero time

The first entry in the table is for a hypothetical spaceship whose speed is roughly comparable to today's spacecraft: it does the trip at 50,000 miles per hour (83,000 km per hour). To illustrate how slow this is, the trip would require some 35 billion years! Clearly, we must go faster.

For the second entry in the table, I assume a spaceship that can travel at half the speed of light (0.5C, where “c” is the scientific symbol used for light speed, which is 186,000 miles per second, or 300,000 km per second.) It will be a long time—if ever—before we'd reach that kind of speed. Nonetheless, for illustration purposes, the round trip to Andromeda would require 4,400 years for those aboard that ship, if they traveled at half the speed of light. That’s still a very long trip.

Let's say our imaginary ship could travel at 90% the speed of light (0.9c). Now the trip for those on board would be down to 1,260 years. Let's go even faster: to 99.9% the speed of light (0.999C). Then the trip could be finished in a mere 120 years.

For reasons I won't go into here, no real spacecraft could ever reach these speeds, despite the accomplishments of the starship USS Enterprise on “Star Trek,” which can reach warp speed eight—some eight times the speed of light! That's a fun way to fly around space, but is entirely fictional. Unfortunately, those interstellar distances will remain way beyond us mortals.

I've included one more interesting calculation in the table: the lapsed time to and from Andromeda Galaxy, for something that manages to travel right at the speed of light. (One of the consequences of Einstein's theory is that nothing can ever exceed the speed of light; it's an absolute upper bound.) For that light-speed trip, no time has passed at all! In fact, an object traveling at the speed of light can traverse the entire universe (and back, if it wishes) and never register any time lapse!

What kind of “thing” could travel at the speed of light? Well, light itself does, which we may describe as photons zinging along at c. Photons can do this only because they have no mass... they are completely immaterial. A consequence of  photons being massless is that they always are moving at the speed of light... they can exist only as moving particles.

So if you could ride along with a photon at the speed of light, you would in essence become immortal. Of course, your material being would never withstand the trip, but the massless photon can. So, for us material mortals back home, photons would require five million years for the round trip to Andromeda, but to them, they do it in no time at all.  That, it seems to me, is a definition of immortality.

As I pondered this fascinating result recently, it occurred to me that, while we material beings are mortal—often also described as being temporal, ephemeral, or perishable critters—some religions consider our souls to be immortal. If we do have a soul, it is immaterial; it is massless.

So a massless soul—like the massless photon—can only exist as something traveling at the speed of light. It could go on its merry way forever (that time lapse of “forever” being what we stationary mortals would measure), taking no time at all, from its perspective. Would that not be a definition of our soul being immortal?

Can't Go Faster Than Light

Most of us have heard that the speed of light is the absolute upper speed limit of the universe. This fact was realized by Albert Einstein over 100 years ago, as he wrestled with what came to be known as his Special Theory of Relativity. He made an absolutely brilliant breakthrough, after struggling for several years with the dilemma of what would happen if we were able to race through space at velocities approaching the speed of light.... sometimes called relativistic speeds.

Einstein published his famous Special Relativity paper in 1905, at the tender age of 26, after having anguished for some 10 years over the paradox of travel near the speed of light. His special theory has a number of brilliant insights, but I'll focus here on just one of them: that the speed of light truly is an absolute upper speed limit. Nothing, not even light itself, can go faster. Here's a simple example of why that's true, and I'll use the TV series “Star Trek” as an illustration.

As millions of “Star Trek” viewers know, the USS Enterprise cruised through interstellar space, going “where no one has gone before,” and often at warp speed—that is, faster than light. Cap'n Kirk (or Cap'n Jean Luc Picard, in the follow-on series) would often command Scottie to move post haste to the next star system, let's say at warp factor 3—in other words at 3 times the speed of light. In critical circumstances, Kirk would even order a speed of warp factor 8! Sounds good, but those are impossible velocities. Here's how Einstein's theory demonstrates why.

Let's suppose that the Enterprise is temporarily based on Planet Zenon, where it is undergoing an extensive refurbishing. While the overhaul is going on, another (slower) starship, the USS Intrepid, leaves Zenon, headed for Earth, at 60% the speed of light, but they have inadvertently left behind an important document. Not to worry, says Cap'n Kirk; as soon as the Enterprise is ready to fly, we'll chase after the Intrepid at warp factor 3, catch up with them, and deliver the document well before they get back to Earth. 
 
Unfortunately, however, overhaul work on the Enterprise goes excruciatingly slowly. It's now four years later when Kirk's ship finally departs, at 3 times the speed of light. At that rate it requires them only one year to catch up with the slower Intrepid, which has been tootling along for five years, but has only gotten three light years away. Thus they meet in space five years after the Intrepid had departed—five long years of travel for the slow Intrepid, but just one for the speedy Enterprise. Still sounds OK. But...

I won't go in to all the details by using Einstein's complex equations of his special theory. Let me simply leap to the weird result that his theory predicts. From the perspective of the crew on the Enterprise (going at 3 times the speed of light), they left at year four and caught up with the Intrepid at year five. But if you use Einstein's relativistic equations, you get the impossible situation that, from the Intrepid's perspective, they were met by the Enterprise one year before (yes, before!) the Enterprise had even left Planet Zenon! 
 
I realize I've thrown around some possibly confusing numbers here, but the bottom line is, if faster-than-light speed is proposed, Einstein's special theory predicts an effect (the meeting with the Enterprise) before its cause (the finish of the rehabbing of the Enterprise). It's like saying that I celebrated my first birthday a year before I was born, or an arrow hits the target before the archer draws the bow! Clearly this is impossible. It's like time running backwards. We cannot have effects happening before the cause. 
 

Scientists have many times conducted experiments that verify Einstein's Special Theory of Relativity. The theory is right. In other words, the speed of light is an absolute upper speed limit. If it wasn't, things going faster than light would literally turn clocks backwards. Sorry, Cap'n Kirk, you can't do warp 3... and especially warp 8. But Star Trek was science fiction, after all.