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Paul Halpern is a professor of physics at St. Joseph’s University and the author of 18 popular science books, including: spark of creativity, quantum labyrinth, Einstein’s dice and Schrödinger’s catand synchronicity. He is a recipient of a Guggenheim Fellowship and a Fellow of the American Physical Society.
Below, Paul shares five key insights from his new book. The appeal of the multiverse: different dimensions, other worlds, and parallel universes. Listen to the audio version read by Paul himself on the Next Big Idea app.
1. Curiosity pushes us to think outside the box of observability.
“Take the picture or it doesn’t happen” is a commonly used phrase. In today’s technological age, where cameras are almost everywhere, we yearn for photographic proof of everything. We are therefore fascinated by the extraordinary pictures taken by the James Webb Space Telescope of the early galaxies of the universe after the Big Bang. If our instruments could pick up signals from across the universe, we could systematically map them and perhaps develop testable theories about everything. Many who reject the idea of a multiverse argue that everything in science must be completely verifiable.
Perfect measurability would be ideal, but it doesn’t happen. First, the speed of light sets a hard limit on what we can detect. It divides enclaves called. observable universe From potential areas beyond that. The actual universe may be infinite, but only a finite region can be directly detected. But that doesn’t stop you from wondering what lies beyond those limits. In the absence of direct evidence, indirect evidence can be very convincing.
Just as volcanoes reveal Earth’s interior, perhaps their impact on the observable universe will reveal aspects of the rest of the universe, including the possibility of other expanding universes with larger multiverses. I might. When we are on the upper floors of a stable high-rise building, we assume that there is a solid foundation underneath without even visiting the bedrock. Similarly for the universe, indirect evidence may be sufficient when direct observation is not possible.
2. Quantum reality is like an infinite hotel with a strange key system.
Quantum physics poses even greater frustration for those seeking complete specificity and verifiability in science. Compared to classical mechanics, in the quantum realm physical observations such as position and velocity are no longer fundamental. Rather, as the brilliant scientist John von Neumann emphasized, the key to the theory is the evolution of quantum states in an abstract realm of infinite dimensions called . Hilbert space.
“Indirect evidence can be very convincing in the absence of direct evidence.”
Mathematician David Hilbert, for whom the term was coined, reportedly used the analogy of a hotel with infinite rooms as a way to address the concept of infinity. According to von Neumann, the representation of a quantum system depends on the experimenter’s choice of what he is trying to measure. Hilbert’s hotel is such that guests are given a key to only one of the hallways and are prohibited from exploring other hallways. Rooms are then randomly assigned within the selected hallway. Similarly, in a quantum system, after an experimenter observes a certain physical parameter, such as position, a state collapses to one of its values with a certain probability. One may wonder why observer choice is so important.
In the mid-1950s, young physicist Hugh Everett III developed one of the first scientific multiverse models that eliminated the role of an observer. Rather than collapsing, the quantum state maintains all possibilities indefinitely. The problem is that the observer’s consciousness also diverges along parallel lines of reality and remains stuck in a variety of possibilities. Such a concept is Many-worlds interpretation The theory of quantum mechanics has been controversial since its inception.
3. Inflating space seems as simple as blowing bubbles.
Another type of multiverse model derives from a general explanation of why the observable universe is so smooth and regular. inflation model. According to that scenario, the currently detectable portion of the universe would have gone through a superfast epoch of exponential expansion shortly after the Big Bang. The effect was like quickly stretching a wrinkled sheet in all directions to make it flat and uniform. Inflation therefore explains why, on the largest scales, the density of matter and energy has a remarkable uniformity.
Physicist Andrei Linde has developed a successful mechanism to explain how quantum fluctuations in the energy field could easily cause the cosmic region to expand rapidly in the violent conditions of the early universe. But, as he quickly discovered, the induction of inflation is not an isolated phenomenon. Rather, it’s very easy to generate, meaning it happens very often and continues to happen. eternal inflation. So instead of imagining a single big bang, it’s helpful to imagine the primordial universe as a bubbly bubble bath. One of those bubbles has grown into our universe, but there may be other universes out there as well. Astrophysicists continue to search for evidence of collisions between our universe and neighboring universes.
4. Telescopes and calculations reveal the strangeness of the observable universe.
Cosmologists’ understanding of the universe is based on Einstein’s technical excellence. general relativity. In an early version of his model, before researchers discovered the expansion of the universe, Einstein introduced a stabilizing factor called the cosmological constant. It acts to provide a kind of continuous external pressure. In 1998, researchers discovered that the universe was not only growing, but also expanding faster. A small cosmological constant models the growth acceleration well. Around the same time, theorists discovered a way to calculate what the cosmological constant would be if it were caused by the energy of a quantum field emerging from the vacuum of space, and they found a very high value. If theory predicts a large cosmological constant, why should the detected cosmological constant be small in the universe?
“In 1998, researchers discovered that not only is the universe growing, but its expansion is accelerating.”
inside anthropic principleProposed by Brandon Carter in the 1970s, the conditions of the universe are limited by the fact that they must eventually produce intelligent observers. Otherwise we wouldn’t be here. One way he thinks about this idea is to imagine a multiverse that houses a large number of alternative parallel worlds. Only a few of them have the right ingredients to give rise to stars, planets, and life, including a relatively small cosmological constant. So, according to that view, since we are here, the cosmological constant is very small in our universe. In most other universes, it is very large.
5. Encountering alternate selves is not how science deals with the multiverse.
What we fail to find in science, even in speculative fields, is the general idea that each of us is an almost dual being with a different personality in another field of reality. It’s a concept. We can’t suddenly go through a portal and meet our doppelgänger. While it’s fun to imagine otherworldly versions of Spider-Man or Batman teaming up to take down the bad guys, such encounters have no basis in physics.
According to theorists, a true wormhole connecting our universe to other universes would require the mass of a galaxy and would obliterate Earth if created nearby. Doesn’t matter; they become essential in the film as plot devices that allow for strange encounters with alternate histories. Scientific and cultural depictions feed each other, but they remain distinct.
To listen to the audio version read by author Paul Halpern, download the Next Big Idea app now.
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