The tick is like the tock. So simple that one takes it for granted. One assumes that across the universe the tick and tock echoes equally. It is such a universal law here on Earth that like gravity it is unbreakable. Yet, like gravity, it is hardly universal at all. Just beyond the protection of our atmosphere both fall apart.
When man first walked the Earth no tick or tock echoed in its brain. There was simply light or no light. Now we are driven to nervous breakdowns by its continuous repetition. We invented the clock and made ourselves slaves to it soon after.