No, we haven’t finally found evidence for a parallel Universe
The ANITA experiment found cosmic rays shooting out of Antarctica. One interpretation claims “parallel Universes,” but is that right?
The concept of parallel Universes is quite appealing, offering us the fantasy of a Universe where the wrongs we’ve done in our life were righted by a version of ourselves who made better judgments. It’s feasible that scientific findings here on Earth could yield evidence for the existence of parallel Universes, which has long been a staple of science fiction. However, despite some claims, a new discovery utilizing cosmic rays by the ANITA experiment does not provide the evidence required to draw those spectacular conclusions. This is why.
For some of us, the concept of parallel Universes inspires our greatest fantasies. If there are other Universes where certain events had different outcomes — where just one crucial decision went a different way — perhaps there could be some way to access them. Perhaps particles, fields, or even humans could be moved from one Universe to another, allowing us to live in a Universe that is superior to our own in certain aspects. These notions have a presence not only in science fiction, but also in theoretical physics, ranging from the infinite number of possible outcomes of quantum mechanics to Multiverse concepts.
But do these ideas have anything to do with observable, measurable reality? Recently, a report appeared claiming that we’ve discovered proof for parallel Universes using the ANITA (ANtarctic Impulsive Transient Antenna). True, the experiment discovered evidence for cosmic ray particles that is challenging to explain using conventional physics alone. However, jumping to the most fantastical, outlandish, revolutionary explanation is entirely premature. We must exercise extreme caution in all fields of research to avoid trying to kid ourselves. We must attempt to disprove any new, wild notions and instead ensure that known natural laws cannot possibly explain what we’re observing.
When we approach science with appropriate scepticism, we observe that the evidence for a parallel Universe almost vanishes.
One depiction of the multiverse concept is an example of multiple, independent universes, causally detached from one another in an ever-expanding cosmic ocean. (Credit: Ozytive/Public domain)
Parallel Universes are one of those intriguing notions that captures our imaginations and drives us to explore their existence, but it is also an idea that is extremely difficult to prove. Parallel Universes first appeared in the context of quantum physics, which is known for producing unforeseen results even when you know everything about how you set up your system. When you shoot a single electron through a double slit, you can only guess where it will land; you cannot forecast exactly where it will appear.
One fascinating idea, known as the many-worlds interpretation of quantum physics, argues that all possible outcomes occur, but only one event can occur in each Universe. To account for all the possibilities, an infinite number of parallel Universes are required, but this interpretation is just as valid as any other. There are no experiments or observations that support this theory.
The Many Worlds Interpretation of quantum mechanics holds that there are an infinite number of parallel Universes that exist, and making an observation simply selects one path. This interpretation is conceptually interesting, yet it may add nothing to actual physics. (Credit: Christian Schirm/Wikimedia Commons)
The concept of the Multiverse is another source of parallel Universes in physics. Our observable Universe began 13.8 billion years ago with the hot Big Bang, but that was not the beginning. A very distinct phase of the Universe occurred before to the Big Bang to set up and give rise to it: cosmological inflation. A Big Bang occurs when and where inflation ends.
However, inflation does not cease everywhere at once, and the places where it does not end continue to inflate, creating additional space and maybe more Big Bangs. In fact, once inflation begins, it is nearly impossible to stop it from occurring in perpetuity, at least somewhere. As time passes, more Big Bangs occur, all of which are unconnected, giving rise to an infinite number of independent Universes: a Multiverse.
While it is predicted that many independent Universes will be produced in an inflating spacetime, inflation never stops everywhere at once, but rather only in different, independent zones separated by space that continues to inflate. This is the scientific basis for a Multiverse, and why no two Universes will ever intersect. There just aren’t enough Universes created by inflation to hold every possible quantum outcome due to particle interactions within a single Universe. (Credit: MUSTAFABULENT / Adobe Stock)
The main issue with both of these theories is that there is no mechanism to test or constrain the predictions of these parallel Universes. After all, how can we hope to reach another Universe if we’re stuck in our own? We have our own physical laws, but they are accompanied by plenty of quantities that are constantly conserved.
Particles do not appear, disappear, or transform; they can only interact with other quanta of matter and energy, and the outcomes of those interactions are also determined by physical laws.
We have yet to identify an interaction that requires the presence of something other than our own, isolated Universe to explain in all of the experiments we’ve ever performed, observations we’ve ever recorded, and measurements we’ve ever taken.
The Standard Model of particle physics explains three of the four forces (except gravity), the entire array of known particles, and their interactions. It is questionable if there are new particles and/or interactions discoverable with colliders we can build on Earth, but there are many outstanding questions, such as the observed absence of strong CP violation, with the Standard Model in its current form. (Credit: Contemporary Physics Education Project/CPEP, DOE/NSF/LBNL)
However, according to various accounts on the ANITA experiment’s unexpected discoveries, scientists in Antarctica have discovered evidence for the existence of parallel Universes. This would be incredibly revolutionary if true. It’s a lofty claim that would demonstrate that our current understanding of the Universe is inadequate, and that there’s far more to learn and discover than we ever thought possible.
These other Universes would not only exist, but matter and energy from them would be able to cross over and interact with matter and energy in our own Universe. If this claim is true, some of our wildest science fiction fantasies may become a reality. Perhaps you could travel to a Universe:
- Where you chose the job overseas instead of the one that kept you in your country?
- Where you stood up to the bully instead of letting yourself be taken advantage of?
- Where you kissed the one-who-got-away at the end of the night, instead of letting them go?
- Or where the life-or-death event that you or your loved one faced at some point in the past had a different outcome?
So, what was the extraordinary evidence that proved the existence of a parallel Universe? What observation or measurement resulted in this remarkable and unexpected conclusion?
The ANITA (ANtarctic Impulsive Transient Antenna) experiment — a balloon-borne experiment that’s sensitive to radio waves, discovered radio waves of a certain set of energy and directions originating from beneath the Antarctic ice.
This is great; it’s exactly what the experiment was supposed to do! We have all kinds of cosmic particles traveling through space, including the ghostly neutrino, in both theory and practice. While many of the neutrinos that travel through us are emitted by the Sun, stars, or the Big Bang, some are emitted by massively energetic astronomical phenomena such as pulsars, black holes, supernovae, or even mysterious, undiscovered things.
The Antarctic Impulsive Transient Antenna (ANITA) experiment, which picked up signals of apparently impossible particles as it dangled from its balloon over Antarctica, is about to be launched. (Credit: NASA)
These neutrinos also have different energy, with the most energetic ones being the rarest and, to many physicists, the most interesting. Neutrinos are mostly invisible to regular matter — you’d have to pass a typical astrophysical neutrino through about a light-year’s worth of lead to have a 50/50 shot of stopping one — therefore they can realistically originate from any direction.
Most of the high-energy neutrinos we observe, however, are formed when other cosmic particles (also of extremely high energies) collide with the upper atmosphere, resulting in particle cascades that also produce neutrinos. Some of these neutrinos will pass almost completely through the Earth, only interacting with the final layers of the Earth’s crust (or ice) to generate a signal that our detectors can detect.
While high-energy particle showers are common, it is largely muons that make it down to Earth’s surface, where they can be detected with the correct equipment. Neutrinos are also produced, with some of them passing through the Earth, however this explanation for the ANITA signal is less compelling than some of the more ordinary options. (Credit: Alberto Izquierdo; Francisco Barradas Solas).
The uncommon events observed by ANITA were compatible with a neutrino travelling through the Earth and creating radio waves, but with energy so high that uninhibited travel through the Earth should not be possible. So we must now put on our skeptical goggles and ask some critical questions about how seriously we should take these observations.
- How many events like this did they see? They witnessed three similar situations. Just three.
- Was it necessary for them to pass through the Earth? No. The first two could have been regular air-shower tau neutrinos (one of three types of neutrinos permitted) rather than neutrinos that travelled through the entire Earth, while the third could simply have been part of the experimental background.
- Is there any confirmation from IceCube, Antarctica’s other, larger neutrino detector? This is the crucial question, because a more sensitive experiment should have detected a more persuasive signal than ANITA did. As it turns out, the existence of IceCube is an incredible piece of evidence that disfavors the idea that these neutrinos came through the Earth. IceCube would have seen a signal if high-energy tau neutrinos were travelling through the Earth (and the Antarctic ice). And, without a doubt, they have not.
When a neutrino interacts with the clear Antarctic ice, secondary particles are produced that leave a trace of blue light as they pass through the IceCube detector. The absence of high-energy tau neutrinos detected by IceCube effectively rules out an astronomical origin for whatever caused the radio waves observed by ANITA. (Credit: Nicolle Rager Fuller/NSF/IceCube)
Scientifically, this means that:
- ANITA saw radio signals that it could not explain,
- their leading hypothesis was that high-energy tau neutrinos are traveling upwards through the Earth,
- and that hypothesis was refuted by IceCube observations,
- teaching us there is no astrophysical point source out there that is creating the particles that ANITA is indirectly seeing.
So where, in all of this, do the parallel Universes come in? Because there were only three possible explanations for what ANITA observed.
- Either there was an astrophysical source for these particles,
- or there’s a flaw in their detector or their interpretation of the detector data,
- or something very exotic, remarkable, and beyond the Standard Model (known as CPT violation) is happening.
Some very good science ruled out the first option (back in January of 2020), which means it’s almost certainly the second option. The third? Well, if our Universe cannot violate CPT, maybe this comes from a parallel Universe where CPT is reversed: an explanation that’s as unlikely as it is poorly reasoned.
This diagram shows the various ways signals can reach ANITA while it floats over Antarctica attached to a balloon. Simply said, a reflected cosmic ray could be confused for a cosmic neutrino that passed through the Earth and decayed shortly before being detected by ANITA. (Credit: ANITA Collaboration/NASA)
In fact, physicist Ian Shoemaker proposed a spectacular but mundane explanation for what ANITA saw back in April of 2020: ultra-high-energy cosmic rays could have simply reflected off of certain types of ice at or near the Antarctic surface, creating the illusion that these particles traveled through the Earth from ANITA’s perspective. Remember that in science, we must always rule out all conventional explanations that do not involve new physics before resorting to a game-changing explanation. Several astounding assertions have been made during the last decade that have collapsed following additional study. We haven’t discovered dark matter or sterile neutrinos; cold fusion isn’t real; and the unachievable “reactionless engine” was a failure.
There’s an incredible story here about good science. An experiment (ANITA) discovered something unexpected and reported their findings. Following it up was a far superior experiment (IceCube), which ruled out their leading interpretation. It strongly suggested that something was wrong with the original experiment, and absolutely commonplace hypotheses involving no new physics might fully explain for everything we’ve seen. More science, as always, will help us figure out what’s going on. For the time being, based on the scientific facts available, parallel Universes will have to remain a silly idea reserved for science fiction and fantasy.