"Hawkings Bummer Birthday: No Eternal Universe."
- "Cosmologists Forced to 'In the Beginning'":
- Here are the models in brief and why they don’t work:
- Eternal inflation: Built on Alan Guth’s 1981 inflation proposal, this model imagines bubble universes forming and inflating spontaneously forever. Vilenkin and Guth had debunked this idea as recently as 2003. The equations still require a boundary in the past.
- Eternal cycles: A universe that bounces endlessly from expansion to contraction has a certain appeal to some, but it won’t work either. “Disorder increases with time,” Grossman explained. “So following each cycle, the universe must get more and more disordered.” Logically, then, if there had already been an infinite number of cycles, the universe would already been in a state of maximum disorder, even if the universe gets bigger with each bounce. Scratch that model.
- Eternal egg: One last holdout was the “cosmic egg” model that has the universe hatching out of some eternally-existing static state. “Late last year Vilenkin and graduate student Audrey Mithani showed that the egg could not have existed forever after all, as quantum instabilities would force it to collapse after a finite amount of time (arxiv.org/abs/1110.4096).” No way could the egg be eternal.
- The upshot of this is clear. No model of an eternal universe works. Vilenkin concluded, “All the evidence we have says that the universe had a beginning.” An editorial at New Scientist called this, “The Genesis Problem.”