## Sunday, May 13, 2018

According to time dilation, as I understand it, stationary clocks run faster than clocks moving near the speed of light. That's illustrated by the clock paradox and the twin paradox. If an astronaut rides a rocket to a distant planet, traveling near the speed of light, then returns, he will be younger than his identical earthbound twin. Indeed, centuries may have passed on earth. However, that's not quite accurate since the return trip reverses direction.

Time dilation is thought to disprove Newtonian absolute time. However, that depends in part on how we define time. As I understand it, time dilation means a physical process operates at a faster rate in a stationary system than a system moving near the speed of light. So the astronaut on the rocket ages more slowly. But is the rate of a physical process equivalent to time itself? Speeding up a process isn't equivalent to speeding up time, is it? For instance, some humans live longer than others because they seem to be aging more slowly. At 110, their physical condition is similar to an octogenarian. But that's not due to time slowing down in their bodies.

Mind you, this doesn't mean Newton was right, because it goes to the nature of time. What is absolute time? Is time a property of a physical (or mental) process, or is a physical (or mental) process a property of time? Is time a principle independent of the things it conditions? Is time a general principle, which physical (or mental) processes exemplify?

Can we tell? Can timebound observers assume a detached perspective to discern what time is really like, apart from its affect on us? We're so conditioned by time that it's hard to describe time directly.

That's an issue in science generally. We use the five senses to perceive the physical world. But the senses filter the world. So there's a conundrum: we can't sense the world without the filter, but the filter screens out certain features while tinting other features. The question then is whether we can reconstruct what the world is really like from reflections and refractions.

Take a pond. I can see the sky mirrored in the pond. I can see reflected trees and shadows overhanging the pond. Normally, I can compare the reflection to viewing the sky and trees directly. But what if my knowledge of the world was confined to the reflection? Can I reconstruct what the world is really like from the fluid mirror? That distorts reality. Ripples. The color of sunlight. And there's a more subtle change because a mirror-image reverses chirality.

Years ago I was standing on a dock at night, looking at the moonlight on the water. It wasn't just generic moonlight. If you look closely, the image of the moon is reflected on the water. Repeated images of the moon. Wave action breaks it up, scattering the beams.

If you couldn't look straight at the moon, if all you had to go by was the reflection, you'd see many moons. How would you do physics or astronomy from that viewpoint? Could you infer that one large moon was produced all these little snapshots of itself? Can we infer an unfiltered view of the world from our filtered input? Can we filter out the filter without going blind? Can we separate the information from the filtering effect without losing key information?