Imagining the possibility of life in a universe without the weak force

February 5, 2018 by Bob Yirka, report
Credit: CC0 Public Domain

A team of researchers at the University of Michigan has conducted a thought experiment regarding the nature of a universe that could support life without the weak force. In their paper uploaded to the ArXiv preprint server, the researchers suggest life could be possible in such an alternative universe, but it would definitely be different from what we observe in ours.

Physicists have debated the possibility of the existence of alternate universes for some time, though there is no evidence they exist. In this new , the team at UM wondered if one or more of the laws of physics that we have discovered in this might not exist in others—if they do exist. Because it would be hard to imagine a universe that could exist without gravity and the strong and , the team instead focused on the weak force—the one behind such things as neutrons decaying into protons.

The team wondered what a universe without the weak force would look like. To visualize it, they created a simulation of such a universe starting from the Big Bang. In the simulation, matter was still created and condensed into stars, but from there on, things would be different, because in our universe, the weak force is responsible for the creation of the . In a universe without the , the existence of anything other than stars would require more free protons and fewer neutrons (because they could not decay). In such a universe, neutrons and protons could link up to make deuterium.

Stars fueled by deuterium instead of hydrogen, the researchers note, would still shine, they would just look different—likely redder and larger. But such stars could also serve as the source of all of the elements in the periodic table prior to iron, and the stellar winds could carry them out into space. If planets happened to form, they further note, they could hold water made from deuterium rather than hydrogen—and it is not impossible to imagine, they suggest, life forms made with deuterium water.

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More information: Universes without the Weak Force: Astrophysical Processes with Stable Neutrons, arXiv:1801.06081 [astro-ph.GA]

We investigate a class of universes in which the weak interaction is not in operation. We consider how astrophysical processes are altered in the absence of weak forces, including Big Bang Nucleosynthesis (BBN), galaxy formation, molecular cloud assembly, star formation, and stellar evolution. Without weak interactions, neutrons no longer decay, and the universe emerges from its early epochs with a mixture of protons, neutrons, deuterium, and helium. The baryon-to-photon ratio must be smaller than the canonical value in our universe to allow free nucleons to survive the BBN epoch without being incorporated into heavier nuclei. At later times, the free neutrons readily combine with protons to make deuterium in sufficiently dense parts of the interstellar medium, and provide a power source before they are incorporated into stars. Almost all of the neutrons are incorporated into deuterium nuclei before stars are formed. As a result, stellar evolution proceeds primarily through strong interactions, with deuterium first burning into helium, and then helium fusing into carbon. Low-mass deuterium-burning stars can be long-lived, and higher mass stars can synthesize the heavier elements necessary for life. Although somewhat different from our own, such universes remain potentially habitable.

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5 / 5 (1) Feb 05, 2018
Imagining the possibility of life in a universe without the weak force
Weak force is very important as it prohibits the collapse of matter into singularities. The weak force also plays an important role in nuclear fusion, the reaction that powers the Sun, stars and terrestrial life. The first step in hydrogen fusion is to smash two protons together , it creates an unstable form of helium (2He), which has a nucleus with two protons, as opposed to the stable form of helium (4He), which has two protons and two neutrons. The next step is where the weak force comes into play. Because of the overabundance of protons, one of the pair undergoes beta decay. After that, other subsequent reactions, including the intermediate formation and fusion of 3He, eventually form stable 4He. Without the weak force several thousands of the nuclei that we register as unstable and radioactive would be stable..
not rated yet Feb 06, 2018
If my body used deuterium water instead of the lighter water that life here on Earth is mostly made of, then I would weigh a lot more. Humans would have to be shorter, maybe more like Neanderthals?
not rated yet Feb 06, 2018
If the water on the Earth would be formed mostly by deuterium, then the oceans would be gray or green instead of blue and they would pass more light for algae and cyanobacteria. And the terrestrial organisms would be also affected, because the ice wouldn't cover the surface of water during winter, but it would collect itself at the river bottom. The climate would be warmer because of missing Arctic ice caps reflecting the light, and so on.

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