In a previous article, Alon Retter argued the big bang was a white hole – a time-reversed black hole, the possible existence of which has been brought to popular attention by Carlo Rovelli. But the big bang and the white hole have crucial differences in their structures, which creates more questions than answers, writes Geraint F. Lewis.
Where did our universe come from? What gave birth to all the matter that formed into stars, planets, and people? Astronomers tell us that our cosmos was born in a fiery event almost fourteen billion years ago and has been expanding ever since, but while this Big Bang picture accurately explains the universe's evolution, the ultimate origin remains mysterious. A radical suggestion is that our universe is a white hole, the mirror image of a black hole, but is this physically reasonable?
To answer this, we will need to understand what a white hole is. To do this, we need to understand a little about their more famous alter egos, black holes.
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The universe is full of incredible things, but black holes are perhaps the most incredible. With matter crushed down to infinite density and a gravitational pull that prevents anything from escaping, black holes have been found across the universe. Supermassive black holes, billions of times the mass of the Sun, have been identified in the hearts of galaxies, while smaller black holes are known to roam between the stars. In the last decade, new gravitational wave detectors have revealed the unmistakable signature of merging black holes deep into the cosmos.
Mathematically, black holes are part of Einstein’s general theory of relativity, originally derived in Karl Schwarzschild’s explorations of relativity in 1916. However, black holes remained a theoretical curiosity until the 1960s when astronomical evidence finally convinced us that black holes truly existed.
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A word of caution, however, as while the mathematics of relativity permits white holes, whether they physically exist remains unanswered. No conclusive evidence points to white holes existing in our universe.
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