## a parallel universe? -- 12/6/23

**Today's selection -- from Parallel Worlds by Michio Kaku.** If electrons can exist in two places at the same time, why not universes themselves?:

“In the *Hitchhiker's Guide to the Galaxy*, the bestselling, irreverent, wacky science fiction novel by Douglas Adams, the hero stumbles upon a most ingenious method of traveling to the stars. Instead of using wormholes, hyperdrives, or dimensional portals to travel between galaxies, he conceives of harnessing the uncertainty principle to dart across the vastness of intergalactic space. If we can somehow control the probability of certain improbable events, then anything, including faster-than-light travel, and even time travel, is possible. Reaching the distant stars in seconds is highly unlikely, but when one can control quantum probabilities at will, then even the impossible may become commonplace.

“The quantum theory is based on the idea that there is a probability that all possible events, no matter how fantastic or silly, might occur. This, in turn, lies at the heart of the inflationary universe theory--when the original big bang took place, there was a quantum transition to a new state in which the universe suddenly inflated by an enormous amount. Our entire universe, it appears, may have sprung out of a highly unlikely quantum leap. Although Adams wrote in jest, we physicists realize that if we could somehow control these probabilities, one could perform feats that would be indistinguishable from magic. But for the present time, altering the probabilities of events is far beyond our technology.

The front cover of the 1996 CD release of The Primary Phase, one of the first BBC CD releases. |

“I sometimes ask our Ph.D. students at the university simpler questions, such as, calculate the probability that they will suddenly dissolve and rematerialize on the other side of a brick wall. According to the quantum theory, there is a small but calculable probability that this could take place. Or, for that matter, that we will dissolve in our living room and wind up on Mars. According to the quantum theory, one could in principle suddenly rematerialize on the red planet. Of course, the probability is so small that we would have to wait longer than the lifetime of the universe. As a result, in our everyday life, we can dismiss such improbable events. But at the subatomic level, such probabilities are crucial for the functioning of electronics, computers, and lasers.

“Electrons, in fact, regularly dematerialize and find themselves rematerialized on the other side of walls inside the components of your PC and CD. Modern civilization would collapse, in fact, if electrons were not allowed to be in two places at the same time. (The molecules of our body would also collapse without this bizarre principle. Imagine two solar systems colliding in space, obeying Newton's laws of gravity. The colliding solar systems would collapse into a chaotic jumble of planets and asteroids. Similarly, if the atoms obeyed Newton's laws, they would disintegrate whenever they bumped into another atom. What keeps two atoms locked in a stable molecule is the fact that electrons can simultaneously be in so many places at the same time that they form an electron ‘cloud’ which binds the atoms together. Thus, the reason why molecules are stable and the universe does not disintegrate is that electrons can be many places at the same time.)

“But if electrons can exist in parallel states hovering between existence and nonexistence, then why can't the universe? After all, at one point the universe was smaller than an electron. Once we introduce the possibility of applying the quantum principle to the universe, we are forced to consider parallel universes."

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