Astronomers investigating the possibility of multiple universes have, over the last decade, come to accept the multiverse as fact. Some even think it may actually explain why our universe has certain properties, but not others. But in a new paper, researchers attempt to tame the notion by proposing that our minds are projecting a too-good-to-be-true image of reality.
It's a mind-bending idea that has been suggested before, particularly by string theorist Stephen Hawking. However, this paper, posted by theoretical physicist John S. Bell and astrophysicist Avi Loeb of the Harvard-Smithsonian Center for Astrophysics, has a few new twists. They argue that the multiverse is ultimately unlikely to exist because of the known features of how particles behave.
According to Loeb, "What was more essential is that it made your knowledge of the universe much, much easier." "It is necessary to have this observation in order to accept the existence of a multiverse since if several worlds are present around you, they don't appear to interact with one another very much. It turns out that there can be no multiverse if there is no interaction."
A theoretical model of the three worlds model in which the speed of light, both redshift and gravitational lensing can be accounted for.
The work was inspired by the multiverse concept put forward by Yale University astrophysicist Eddie O'Brien, who described how many universes might be in an eternal inflationary state. According to O'Brien, when a region of space is stretched to an infinite size and new particles are created, they experience an incredibly high rate of expansion — far faster than that of our universe. But at some point, the rate of expansion slows. And as the universe continues to stretch, the matter in each bubble can sometimes get together in the same spots to create a similar universe. This can result in similar properties like densities, masses, and even star formation, and have these universes interact like ours. And this can give rise to multiple universes.
In our universe, this process happens very quickly, in 10-43 seconds. But according to O'Brien's model, it happens over a period of about 10 trillion years. And, if this were the case, then theoretically there could be many universes all at the same time, each outnumbering our own. According to O'Brien's research, those infinite bubbles of universes would eventually begin gravitationally attracting each other — essentially forming a bigger bubble, or a multiverse.
In Bell and Loeb's model, that expansion doesn't happen quickly enough to form a multiverse. In their paper, they calculate that each universe has an infinite number of particles in it — and that any interaction is essentially only possible if every particle were equal.
According to Bell, the likelihood of any contact causing things to interact with everything else is so remote that it would not even be detected. Therefore, there cannot be any interaction between particles.
Instead, the researchers conclude that our perspective on the world is too limited. If there is a multiverse, then that would mean that there could be things that we cannot detect, like dark energy and dark matter, that are accelerating the expansion of the universe. And dark energy and dark matter seem to be, in every sense of the word, unknown. According to Bell, it seems unlikely that the quantum effects necessary for these to be a real thing "are perfectly described by a theory that is totally integrated."
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