In his 1980 book Cosmos, Carl Sagan famously wrote, “If you wish to make an apple pie from scratch, you must first invent the universe.” Credit: Moritz Kindler on Unsplash If you follow their threads back in time, the ingredients for a deliciously satisfying apple pie - apples, flour, cinnamon, heat, etc. - wind their way back to before the observable universe. Existence was contained in a vacuum then, a void empty except for quantum fluctuations. According to leading cosmological models, the vacuum was fairly stable and may have existed in this state for a very long time, but it had a weakness. When quantum fluctuations caused a region of space to spontaneously become more stable (to have lower energy) than its surroundings, a “bubble” of greater stability formed. According to cosmological models, this “bubble” of stability rapidly expanded at nearly the speed of light. Multiple bubbles may have occurred at the same time, coalescing and bringing the entire vacuum i
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