LMR-122 · Cosmology
Arrow of Time
The equations of physics don't pick a direction. Your kitchen does.
§ A first look
§ Depths
Six ways into the same idea — from bedtime story to chalkboard. No order required.
L1 · Crayon
Told like a bedtime story.
For a curious 10-year-old. No jargon. Just a picture in your head.
Watch a video of a glass shattering. You can tell instantly whether it's playing forward or backward. Time clearly has a direction. But here's the weird part: almost every equation in physics works the same forward and backward. So where does the arrow even come from? Probably from the universe starting in an extremely tidy state, and slowly getting messier ever since. The 'past' is just the direction where things were neater. The 'future' is just where the mug breaks. It is, suspiciously, also where you have to clean it up.
§ Strange but true
- 01The universe is stranger than your intuition. This is a rule, not an exception.
- 02Every fact in physics was once an outrageous guess. Most still feel like one.
- 03If it doesn't bend your brain a little, you haven't read it carefully enough.
§ From the field journal
Arrow of Time
"The equations of physics don't pick a direction. Your kitchen does."
— observed, sketched, not yet fully understood.
§ Nearby
Constellations near Arrow of Time
→
Entropy
The reason your room gets messier on its own.
→
Heat Death
The universe's quiet, lukewarm forever.
→
Spacetime
Space and time aren't a stage. They're an actor.
→
Time Dilation
Move fast, age slow. Sit in deep gravity, age slow. Time is weather.
→
Big Bang
Not an explosion in space. An expansion of space.