Chapter 19 & 20 of 'Einstein' - all chapters at

19. Albert imagined himself back on the trolley in the Bern town center and asked himself the following question: If this rickety old trolley were traveling at a speed approximating the speed of light, what would happen to time?

He continued to stare at the rays of light spilling out from his study into the living room. It was a straightforward question, simply put. He repeated it, aloud to himself, "If the trolley was traveling close to the speed of light, what would happen to time?" He tried to imagine traveling at 186,000 miles per second on a trolley, he wasn’t getting an image. At least, not one that was helpful. Something was missing. He looked again at the light. Maybe the juxtaposition of light and time within a single frame of reference did not provide a complete picture. In other words, maybe there was not enough going on to allow an insight. Maybe he needed more points of view in order to get a clearer picture of what might happen in this unusual environment. Albert pondered this thought for a moment. To get another point of view, or frame of reference, for what was happening as the trolley approached the speed of light, maybe he should consider adding another trolley to the thought experiment. He did not know if it would help, but if one trolley traveling near the speed of light could be instructive, maybe two trolleys travelling near the speed of light would be twice as good. He decided to change his question, or rather, add a second trolley to it. What would happen to the rate of time if two trolleys were traveling near the speed of light, but one was traveling faster than the other, closer to the speed of light? The answer to this question was not immediately obvious to Einstein. He thought for a few moments and asked himself the direct question: Would time pass at a different rate for the two trolleys? He stared into space again, this time with a perplexed look on his face.

It did not seem possible that time would pass at a different rate for the two trolleys. Still, the advantage of thought experiments was to explore the impossible, or at least the very unlikely. The evidence pointed where it pointed, and Einstein could reject it or pursue it, depending on his state of mind. Einstein pursued the thought. He assumed that if time really did pass at a different rate near the speed of light, then it would probably change gradually. Let's assume, for argument's sake, that time would slow down as one approached the speed of light. If sixty seconds were no longer really sixty seconds as one approached the speed of light, then it would probably change from being sixty seconds in duration gradually. For instance, a minute might be fifty-nine seconds in duration as one accelerated to eighty percent the speed of light, then fifty-eight seconds in duration as one accelerated to ninety percent the speed of light, etc. It would continue to move even more slowly at greater speeds. Thus, in his thought experiment, a minute would be fifty-nine seconds in duration on the slower trolley, and fifty-eight seconds in duration on the faster trolley. It was an extraordinary thought. However, with the assumption that the rate of the passage of time really did change, i.e., slow down, approaching the speed of light, then this description of events might be accurate. No one could know for sure, but on an abstract level, it seemed that the experiment would play out this way if it were possible to conduct it or even simulate those conditions. Albert thought about this possibility and what it suggested.

What would happen to all those theories the great Isaac Newton had developed, if at these incredible speeds, time were really as unpredictable as a bouncing ball on an uneven surface? No, time would not really be "unpredictable" under those conditions, he corrected himself. There would be predictability, even if the absolute-ness of time were in jeopardy. There would still be laws governing the rate of its passage, whether it was slowing down or speeding up as it approached the speed of light. Right? Yes, he answered. Well, probably yes. Albert closed his eyes and considered the two trolleys as they hurtled through space, one behind the other and losing ground, with nothing impeding their acceleration as they approached the speed of light. Clocks on board marked the passage of time on each trolley. If Einstein were right in his imaginary experiment, the second hand on the clock in the faster trolley was advancing ever-so-slightly more slowly than the second hand on the clock in the slower trolley. If time really did slow down as one approached the speed of light, this would be the reality on the trolleys. Albert fidgeted in his chair as he continued to play out the scenario he had created. Sure, it was fine to imagine how the passage of time on one trolley might relate to the passage of time on the other, imagining that it might pass at a different rate, but he thought there was more to the story. He continued to expand the experiment. For instance, suppose there were people on the two trolleys as they traveled at these fantastic speeds. One would need to put aside the fact that no one could possibly withstand the pressure and heat of traveling at such a speed, just like one needed to put aside the fact that one of those rickety old trolleys could travel more than twenty-five miles an hour, much less at a speed approaching 186,000 miles per second.

But putting those physical realities aside for the sake of the thought experiment, suppose there were people on the trolleys and an external event occurred as they sped past. This external event could be anything from an asteroid smashing into Jupiter to the explosion of a star in the vast regions of space. How would such an external events look to the travelers? he asked himself. He grimaced slightly as he asked this question, sitting in the stuffed chair in the almost-dark living room. It was a difficult question to answer, no matter how good one was at thought experiments. As soon as he asked it, however, Einstein knew it was an important question. And it led to a potentially much more important one. How would the riders on the two trolleys experience the external event, as time passed at a different rate in each of the trolleys? Albert had an answer, but it was one that surprised even him. "Differently," he said softly, to the empty room. "They would experience the external event at different times." 20. Albert opened his eyes and sat, straight as a rod. If it was possible that two observers could experience the same event at different times, there was no such thing as simultaneous events – events happening at the same moment for everyone, no matter what they were doing or where they were. He raised both hands, with his palms up, as if to ask, How could I not have thought of this before? A wave of excitement passed through the young scientist as he pondered this insight, which was much more than a disagreement with current understanding. Without simultaneous events, an important part of the Newtonian view of the world would crumble. The concept of simultaneous events was an essential element of absolute time. If all viewers of an event, no matter what their perspective, did not experience an event at the same moment, then Einstein would argue that there was not one "absolute" moment at which the event occurs. The experience of an event therefore depended on the observer’s perspective, or frame of reference; in other words, it was relative. Albert Einstein was part of a Western tradition of thinkers who based truth in logic. For months, even years, he had been wandering through a wilderness of un-logic and non-sense because of the pervasive problems with mechanics. He could not be centered as long as the logic explaining the way the world worked was flawed.

Until now. Until this moment. The demise of simultaneous events had the potential to change everything. It was not just another problem solved; it was an insider's view to the organization of the world. Einstein believed that this insight had the potential to provide the key to explaining the disturbing problems with mechanics. It could support the principle of a universe organized without benefit of a series of absolutes, but instead organized according to principles that would allow for viewers in different locations, traveling at different speeds, to experience events at different times. But was it real or just the ravings of a desperate man? As his adrenaline rush continued, Albert took the simplest example he could, involving a person on a moving train. It did not even need to be in outer space. It could be right there in Bern. He would use beams of light and assume that the speed of light was constant. The Michaelson-Morley experiment had recently confirmed that this speed did not change, no matter what. He imagined a person aboard a moving train, where there was one light source ahead of the train and another behind it. The beams of light from the two light sources were activated simultaneously. He noted that in classical physics, it was obvious that the person on the train would experience both beams of light at the same time. But Albert would say the obvious was no longer true. He would contend that if one light source was positioned ahead of the train and a second light source was positioned behind the train, and the beams of light were activated at the same moment, the light ahead of the train would have less distance to travel. Light was not instantaneous; it traveled at a finite speed just like everything else. (Except perhaps gravity, but that was a different question.) The beam of light activated in the direction the train was heading toward would reach the train before the light the train was heading away from, though the difference would be so slight that it would be impossible to measure. Common sense would suggest that this was impossible. Events happened at a particular moment, and that moment was the same for everyone. Right? Wrong! Albert thought. Thus, the experience of events depended on the position and movement of the observer, which was a very different proposition from anything Newton ever conceived or ever wrote into any of his mechanics. It signaled the death knell for the concept of simultaneous events – that is, it would signal its death knell, as soon as Albert turned his attention to the mathematics and proved what he had just conceived mentally.

He suspected, however, that he had just discovered why Isaac Newton had never been able to prove the existence of absolute time.

It didn’t exist.

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