1 One Unbreakable Rule
Yesterday is untouchable. Once something has happened, it can never unhappen. That single sentence is the starting block for everything that follows.
2 Frozen Past = No Motion, No Heat, No Mess
If nothing in the past can change, nothing in it can move. Zero motion means absolute-zero temperature. At that temperature there is only one possible arrangement, so the past’s entropy is exactly zero — perfect order.
3 Why Early-Universe Order Isn’t a Mystery
Cosmology textbooks often add a “past hypothesis” to explain the Big Bang’s low entropy. We don’t need that extra guess. Anything classified as past must already sit at zero entropy, because the rule above says it is motionless and perfectly ordered.
4 Where We Actually Live: the Infinite Skin
Many books call the present a “razor-thin instant,” but that phrase suggests time is a river we rush through. A more helpful picture is Gabriel’s Horn — a mathematical trumpet.
- Shape: Stretch the curve
y = 1/xinto three dimensions by spinning it around its axis. - Surprise: The horn’s inner surface is infinite; you could paint forever and never cover it all. Its internal volume, however, is finite.
Think of that endless inner skin as the Eternal Now. It isn’t a slice that passes; it’s a vast, always-present surface where two worlds meet:
| Region | What Lives There |
|---|---|
| Inside Wall (Horn’s skin) | The unchanging record of everything already locked into history |
| Outside Air | All the possibilities that haven’t happened yet |
Every moment you experience is simply a new dot on that surface: a choice sliding from the open air of potential to the lacquered wall of fact.
5 How Quantum Uncertainty Fits the Picture
Physics gives this rule: Δx × Δp ≥ ℏ/2.
- Pin-point position → zero momentum → the event sticks to the horn’s inner wall (it becomes past).
- Precise momentum → fuzzy position → the event hovers outside, still future.
The rule is just another way of describing which side of the horn a possibility occupies.
6 The Whole Logic in Five Lines
- Past can’t change → things in it don’t move.
- No motion → absolute-zero temperature.
- Absolute zero → zero entropy.
- Entropy starts low automatically; it only grows as we step farther from the horn’s narrow throat of perfect order.
- Uncertainty marks the border: fixed events cling to the wall; free ones float outside.
7 Take-Home Image
Stop picturing “now” as a knife-edge flashing by. Picture it as an endless, shining surface — the inner skin of Gabriel’s Horn — where each new choice lands, sticks, and joins the flawless mosaic of yesterday.