Cosmologists base their expectation custodia samsung a 3 2016 of the expansion rate a rate known as the Hubble constant on measurements of cover iphone 6 antiurto radiation emitted shortly after the Big Bang. This radiation reveals the precise ingredients of the early universe. Cosmologists plug the ingredients into their model of cosmic evolution and run the model forward to see how quickly space should be expanding today.

Original story reprinted with permission from Quanta cover store via del corso Magazine, an editorially independent publication of the Simons Foundation whose mission is to enhance public understanding of science by covering research developments and trends in mathematics and the physical and lifesciences.

Yet the prediction falls short: When cosmologists observe astronomical objects such as pulsating stars and exploding supernovas, they see a universe that’s expanding faster, with a cover iphone 5 aliexpress larger Hubble constant.

The discrepancy, known as the Hubble tension, has persisted even as all the measurements have grown more precise. Some astrophysicists continue to debate whether the tension might be nothing more than a measurement error. But if the discrepancy is real, it means cover iphone xs max apple something is missing from cosmologists’ model of the universe.

Recently, theorists have been busy imagining new cosmic ingredients that, when added to the standard model, would rev up the universe’s expected expansion rate, making it match observations.

“Discovering anomalies is the fundamental way that science makes progress,” said Avi Loeb, a cosmologist at Harvard University and one of dozens PIERCE THE VEIL FRANKENSTEIN AVENGE Cover iPhone 8 of researchers who have proposed solutions to the Hubble tension.

These are some of the top ideas for what could be speeding up cosmic expansion.

The standard model of cosmology incorporates all the familiar forms of matter and radiation and their interactions. It also includes the invisible substances known as dark energy and dark matter, which together make up some 96 percent of the cosmos. Because so ONE DIRECTION MY KINGS Cover iPhone 8 little is known about these dark ingredients, they are perhaps personalizza cover iphone 7 the obvious negozio di cover milano place to begin tampering with the standard model. “That’s what you have at your disposal to change the expansion rate of the universe,” Loeb said.

The custodia samsung tab a6 2018 standard model assumes that dark matter consists cover iphone 6 plus personalizzate of slow PANIC AT THE DISCO BLACK WHITE Cover iPhone 8 moving particles that don’t interact with light. But what if we also assume that dark matter is not made of just a single substance Since many different kinds of visible particles exist quarks, electrons and so on there might be multiple dark particles as well.

In a paper published last summer in Physical Review D, Loeb and two collaborators considered a form of dark matter that decays into a lighter particle and a massless particle known as a dark photon. As more and more dark matter samsung tab e custodia decayed over time, they reasoned, its gravitational pull would have lessened, and thus the expansion of the universe would have sped up, relieving the Hubble tension.

But making small changes cover r like this to the standard cosmological model can have unwanted knock on effects. “It’s very easy to come up with all kinds of compra cover online custodia cellulare samsung s4 mini slight modifications,” said Marc Kamionkowski, a theoretical physicist at Johns custodia samsung note 2 bianco Hopkins University but it’s hard cover slim iphone 7 to do so, he said, without ruining the model’s perfect fit with a wealth of other astronomical observations.

By varying the decay rate and the amount of dark matter that is lost in each decay, Loeb and colleagues selected a model of decaying dark matter that they say still agrees with other astronomical observations. “If you add this ingredient to the standard model of cosmology, everything holds together,” Loeb said.

Yet he remains dissatisfied with the decaying dark matter idea, in part because it introduces two new uncertain quantities into the equations.

“In this case, you add two free parameters in order to resolve one discrepancy and I’m uneasy about amazon cover apple iphone 6 that,” he said, comparing decaying dark matter to the epicycles in Ptolemy’s Earth centric model of the universe. “I would rather cover iphone 5s tumblr have two discrepancies explained by one parameter.”

Ever since the surprise discovery in 1998 that the expansion of the universe is accelerating, cosmologists have included a repulsive dark energy in their model of cosmic evolution. But its nature remains a mystery. The simplest possibility is that dark energy is the “cosmological constant” the energy of space custodia in pelle samsung s3 neo itself, with a constant density everywhere. But what if the amount of dark energy in the universe isn’t constant..

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