Sabine Hossenfelder
New Theory Explains How Time Began
Summarised with Bite · 7 min read
A team from Perimeter Institute claims to have solved quantum gravity by proposing the universe started as 4D space without time, then quantum fluctuations created a boundary where one dimension became time. This elegant model explains the Big Bang, inflation, and matter creation while sidestepping the usual mathematical breakdowns, though it relies on one unproven assumption about how gravity transitions at extreme energies.
0:00 – 2:18
The Quantum Gravity Problem That Won't Go Away
Einstein's General Relativity and quantum mechanics are both wildly successful theories. Yet they refuse to cooperate where it matters most: inside black holes and at the Big Bang, the places where gravity becomes so intense that quantum effects should dominate. The problem isn't that physicists can't write down a quantum version of gravity. They can. Einstein's equations convert into quantum form just like electromagnetism or the nuclear forces did. The issue is that this quantum gravity breaks down precisely when you need it, at the extreme conditions where space and time should be fluctuating wildly. The root cause is embarrassingly simple. Gravity's strength is governed by Newton's constant, which has units (like meters or seconds attached to it). Compare that to electromagnetism, where the coupling constant alpha is approximately 1/137, a pure number with no units. The strong and weak nuclear forces work the same way. To make quantum gravity behave properly, you'd need gravity's strength to also be dimensionless. Without that property, the math spirals into infinities and nonsense exactly when you're trying to describe what happens at a black hole's center or the universe's first moment.
3 more sections in the app
- 2:18 – 3:14Quadratic Gravity: The Elegant Solution Nobody Uses
- 3:14 – 4:21A Universe Born From Dimensionless Space
- 4:21 – 5:31The Gap in the Logic
