Decades ago, astrophysicists were filled with hopes of finding dark matter. Dark matter is invisible mass that causes galaxies to spin much faster than the gravity of stars would allow on their own. But subterranean traps set up on Earth to catch what appear to be dark particles have spent years just measuring subterranean silence.
There should be five times more dark matter around us than normal everyday matter, including stars, planets and humans. So physicists who have failed to find this missing blob of space (seen in recent results from his XENONnT experiment in which I participated) are vying for an explanation. But most such attempts merely tweak existing theories or turn to battle-worn alternatives to suggest the same thing. It’s a massive experimental effort to build the most sensitive instrument ever, and they’ve seen nothing.
Unless astrophysicists make big, new, and different moves in dark matter, the search will only stagnate until it dwindles. Fortunately, the disturbing reality that we’re on the wrong track has caused some people to return to the blueprint to seek new avenues of discovery rather than rereading old paths. These more ambitious, sometimes radical and outlandish ideas, whether they succeed or not, at least try to take into account dire circumstances.
Ambiguous Possibility
Desperate physicists began looking to the skies for answers when a detector on Earth failed. For example, one new kind of dark matter search is looking for distorted galaxies that are manifestations of ‘fuzzy dark matter’. The theory holds that dark matter particles are so incredibly light that they behave more like waves than particles.Fuzzy dark matter particles at once, like how you tune into the same satellite radio station in both New York and Los Angeles, rather than a bunch of small, localized mass fires that pass through the Earth like invisible bullets. are everywhere in the galaxy
On a galactic scale, hazy dark matter forms a bath at the bottom of rippling waves, buzzing together like quiet static fluff. Their combined gravitational force still holds the galaxy together, but diffuse fuzzy particles never collide with atoms like conventional particles, so seeing them with detectors on Earth is impossible. you can’t.
Versions of this idea floated around for decades, until theorists realized that this kind of dark matter could have a characteristic effect on galaxies that can be looked for with the right kind of telescope. For example, this wavy fluff forms natural peaks and valleys across the galaxy as a result of the interference of so many wave particles stacked on top of each other. By carefully tracking the motion of stars within the galaxy, we can see signs of these changes, potentially demonstrating the rippling nature of galactic glue.
These astronomical features make fuzzy dark matter particularly attractive at a time when hopes for underground dark matter exploration are waning.
gravity detector
Some ambitious experimenters have begun exploring ways to use modern quantum mechanical sensors to record the tiny gravitational pull of individual dark matter particles as they pass through Earth. They fear that the gravitational pull of dark matter could be the only connection to the ordinary matter world.
However, particles can only be measured in the laboratory if they have another interaction that is much stronger than gravity. Because gravity exerts a much gentler pulling force than any other force, the gravitational force of an individual particle is too small to be noticed. It can only be measured collectively. This makes it a kind of nightmare scenario, as it makes direct detection of gravity-only dark matter impossible. Or so I thought.
Scientists are now trying to come up with new, gravity-sensitive technologies that are much smaller than conventional detectors. Current experimental quantum mechanical sensors may only work if the dark matter particles are very heavy. But in the face of the terrifyingly growing possibility that gravitational-only dark matter is real, exploring this research avenue may yield new and ingenious techniques that can detect lighter particles. There is no necessity.
back to basics
A small but staunch faction of physics has long argued that what we don’t understand is gravity, not the structure of the universe. The idea is gaining new momentum as the evidence remains gravitational.
One novel idea in this area comes from Dutch theoretical physicist Erik Verlinde. He challenges the idea that gravity is a force. Instead, he derives from the observation that the second law of thermodynamics requires that the “entropy” of the universe, a number that quantifies how things “mix together”, tends to increase. start. Verlinde argues that the phenomenon we call “gravity” is simply the result of this tendency. Apples on the ground make up a world that is somehow more stirred together than apples on trees.
To illustrate this, he turns to black holes, the wonders of gravity. Thanks to black holes, it was known since his 1970s that gravity and entropy are related. When an object falls into a black hole and gets bigger, its entropy increases. However, Verlinde put this relationship between gravity and entropy into practice and generalized it to show that by cleverly rearranging the law of entropy, we can obtain the familiar law of gravity.
According to Verlinde, mistaking the law of entropy for another force led us to misunderstand the motion of stars around galaxies. His theory predicts all that movement without relying on dark matter. Ideas are polarizing. Critics have pointed out that the predictions of the “entropic gravity” theory are incompatible with quantum measurements of very cold neutrons, and other theorists have only come to his Verlinde’s defense. But in an age when hope for dark matter is fading, polarization is a good thing. Like Verlinde, more people should think big and gather heat.
The dark matter experiments of the last decade have built on the beautiful simplicity of the hypotheses they were trying to prove. When they left it out instead, a cottage industry emerged and invented more complex versions of the hypothesis to explain the current detector’s evasion and justify its successor. It’s not simple, it’s inertia.
This is the nature of science. It’s easier to pivot than fully shift gears. But at some point, it’s time to go big or go home. Our best hope is to move in new directions, breaking down long-standing pillars of theory and resolving the most embarrassing holes in our cosmic picture.
This is an opinion and analysis article and the views expressed by the author or authors are not necessarily Scientific American.
