Day of the Bruise, 4th of Hagwinter, 525 M.E. (Castor): After Day of the Fall, we have Day of the Bruise. And to think some people feel the Universal Solar Calendar has no sense of humor. 

It was a sitting day today. Topics that came to mind include time and memory, and the intersection of time and memory, which we'll call mental models. 

What is time? Are we travelling through time or is time travelling through us? Why does it sometimes seem to go faster and other times slower, and when it seems to change speed, is it just our perception that's different, or does time itself actually slow down and speed up? Nothing can go faster than the speed of light, but if you were to travel in a spaceship faster that the speed of light like some science fiction posits and you turned on your headlights, would you see anything ahead or would your spaceship warp-speed ahead of the photons? If you turned around and looked backwards, would all you see is black, as light couldn't catch up to your spaceship? 

If you send two beams of light in opposite directions, is the speed that the photons travel away from each other twice the speed of light? If nothing can exceed the constant, c, the speed of light, does the space-time continuum curve so that the beams are travelling away from each other at c, not 2c? 

Is time even really a thing? It's always the eternal present, it's always "now," so can it be argued that the past is just memory and the future only imagination? Is time, the progression from one instantaneous now to the next, merely a construct of the mind to link our memories to our present experience, and our present experience to our future expectations? If the only way to measure time, be it stopwatch, clock, sundial, or whatever, requires the passage of time and we're always in the eternal now, is there really any measurement at all?

When Marty McFly goes "back in time," it's always "now" to Marty - he's experiencing everything in his real time. "Now" he's getting in a DeLorean in the year 1985, "now" he's stepping out of the car in the 50s, and "now" he's back in 1985 again. It doesn't make sense to me that it can always be "now" to Marty, but "not now" to the rest of the universe.

Other questions came up about memory but I don't remember them now.