Immediately after the Big Bang, the Universe underwent ultra-fast expansion, an idea proposed by Alan Guth and developed by Andrei Linde. When the expansion stopped, the field-energy began to oscillate like a giant swing. The rhythmic pushes of this field turned quantum jitters into real particles — and the void started filling with matter.
Precise computer modeling revealed a surprising picture. The birth of matter was uneven: short perturbations arose in sharp jumps, as if the swing was kicked randomly but forcefully; long waves grew smoothly and leisurely. This intermittent process instantly heated the Universe from near absolute zero to unimaginable temperatures. In mere moments, particles of the future Standard Model were born, and entropy — the measure of disorder — surged, setting off an irreversible path toward complexity and chaos.
From near absolute zero after inflation, the Universe instantly heated up to unimaginable temperatures: thus began the hot Big Bang familiar to us from textbooks.