“If the rate of expansion one second after the Big Bang had been smaller by even one part in a hundred thousand million million, it would have recollapsed before it reached its present size. On the other hand, if it had been greater by a part in a million, the universe would have expanded too rapidly for stars and planets to form.”
- January 8, 1942 – March 14, 2018
- British
- Theoretical physicist, science writer
- Announced the black hole singularity theorem and Hawking radiation, and contributed to the popularization of science with his book “Talking about the Universe”
Quote
“If the rate of expansion one second after the Big Bang had been smaller by even one part in a hundred thousand million million, it would have recollapsed before it reached its present size. On the other hand, if it had been greater by a part in a million, the universe would have expanded too rapidly for stars and planets to form.”
Explanation
This quote highlights the fine-tuning of the universe’s expansion in its early moments, a critical concept in cosmology. Hawking is pointing out that the initial conditions of the universe, particularly the rate at which it expanded immediately after the Big Bang, were incredibly delicate. The universe, if it had expanded even slightly differently, could have led to a completely different outcome. If the expansion rate had been slower, gravity would have caused the universe to collapse back on itself before it could reach its current size. If the expansion had been faster, the universe would have spread out too quickly for matter to clump together and form stars, planets, and galaxies.
This is a key aspect of the anthropic principle, which posits that the universe must have the precise conditions necessary for life to arise, or we wouldn’t be here to observe it. The fact that the universe’s expansion was so perfectly tuned to allow the formation of stars and galaxies is seen by some as extraordinary. This fine-tuning raises questions about the origin of the conditions that enabled the universe to evolve into its current state, with some suggesting it could point to a multiverse or other underlying principles of nature that we don’t yet understand.
In modern cosmology, this type of observation has led to important debates about the nature of the cosmos, from the theory of cosmic inflation to more speculative ideas about higher dimensions or multiple universes. The universe’s precise balance is a reminder of the mystery at the heart of cosmology: why did the Big Bang unfold in such a way that life, and the laws of physics we observe, became possible? It is a question that continues to fuel both scientific inquiry and philosophical reflection.
