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Doing Without Dark Energy

Three mathematicians have a different explanation for the accelerating expansion of the universe that does without theories of “dark energy.” Einstein’s original equations for General Relativity actually predict cosmic acceleration due to an “instability,” they argue in paper published recently in Proceedings of the Royal Society A.

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What Lies Beyond The Edge Of The Observable Universe?

You’ve probably read about how the Universe is expanding, and has been expanding since the beginning of time. Over the course of 13.8 billion years or so, it’s stretched from the size of a billionth of a proton to the vast, unknowable expanse it is today. In fact, recent research suggests that it’s actually expanding faster than our current laws of physics can explain, and that’s kind of a problem.

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Dark matter: The mystery substance physics still can’t identify that makes up the majority of our universe

Cosmologists are heading back to their chalkboards as the experiments designed to figure out what this unknown 84 percent of our universe actually is come up empty.

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The Universe Began With a Big Melt, Not a Big Bang – Issue 53: Monsters – Nautilus

There are two tantalizing mysteries about our universe, one dealing with its final fate and the other with its beginning, that have…

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Do gravitational anomalies prove we’re not living in a computer simulation?

Is our entire universe just a computer simulation? Theoretical physicists believe they’ve found proof that our universe is far too complex to be captured in any simulation. According to the researchers, the hypothesis is done in by gravitational anomalies, tiny “twists” in the fabric of spacetime.

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New insights on dark energy

The universe is not only expanding – it is accelerating outward, driven by what is commonly referred to as “dark energy.” The term is a poetic analogy to label for dark matter, the mysterious material that dominates the matter in the universe and that really is dark because it does not radiate light (it reveals itself via its gravitational influence on galaxies). Two explanations are commonly advanced to explain dark energy. The first, as Einstein once speculated, is that gravity itself causes objects to repel one another when they are far enough apart (he added this “cosmological constant” term to his equations). The second explanation hypothesizes (based on our current understanding of elementary particle physics) that the vacuum has properties that provide energy to the cosmos for expansion.

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Scientists Unveil New Inventory of Universe’s Dark Contents | Quanta Magazine

The first major results from the Dark Energy Survey signal the start of a new era of cosmology.

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Scientists Unveil New Inventory of Universe’s Dark Contents | Quanta Magazine

The first major results from the Dark Energy Survey signal the start of a new era of cosmology.

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It’s possible that there is a “mirror universe” where time moves backwards, say scientists

Although we experience time in one direction-we all get older, we have records of the past but not the future-there’s nothing in the laws of physics that insists time must move forward. In trying to solve the puzzle of why time moves in a certain direction, many physicists have settled on entropy, the level of molecular…

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It's possible that there is a "mirror universe" where time moves backwards, say scientists

Although we experience time in one direction-we all get older, we have records of the past but not the future-there’s nothing in the laws of physics that insists time must move forward. In trying to solve the puzzle of why time moves in a certain direction, many physicists have settled on entropy, the level of molecular…

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A Strange New Theory of How Space-Time is Emerging

“A metaphorical chip holding all the programming for our universe stores information like a quantum computer.” This is the radical insight to the foundation of our Universe developed by Mark Van Raamsdonk, a professor of theoretical physics at the University of British Columbia, that says that the world we see around us is a projection from a set of rules written in simpler, lower-dimensional physics-just as the 2D code in a computer’s memory chip creates an entire virtual 3D world. “What Mark has done is put his finger on a key ingredient of how space-time is emerging: entanglement,” says Gary Horowitz, who studies quantum gravity at the University of California Santa Barbara. Horowitz says this idea has changed how people think about quantum gravity, though it hasn’t yet been universally accepted. “You don’t come across this idea by following other ideas. It requires a strange insight,” Horowitz adds. “He is one of the stars of the younger generation.”
“We’re trying to construct a dictionary,” says Van Raamsdonk, that allows physicists to translate descriptions of our complex universe into simpler terms. If they succeed, they will have found the biggest jigsaw piece in the puzzle of a Grand Unified Theory-something that can describe all of the forces of our universe, at all scales from the atomic to the galactic. That puzzle piece is, specifically, something that can describe gravity within the framework of quantum mechanics, which governs physics on small scales. Such a unified theory is needed to explain the extreme scenarios of a black hole or the first moments of the universe.” The catacylst for Van Raamsdonk’s theory was a 1998 paper by Juan Maldacena a theoretical astrophysicist at Princeton’s Institite for Advanced studies that proposed that to understand quantum gravity through string theory, you can look instead to the much more ordinary, well-described system of quantum mechanics called quantum field theory that concluded that it seems that all the information about our complex multi-dimensional world can be described using a simpler, lower-dimensional language-just as a 3D image is projected from the 2D screen of a hologram, or a 3D computer gaming world created from a 2D memory chip. “After that, people wrote thousands of papers just testing whether that could be true,” says Van Raamsdonk. “No one has actually proven it, but we’re as certain about it as about anything in physics,” he added.

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The theory of parallel universes is not just maths – it is science that can be tested

The existence of parallel universes may seem like something cooked up by science fiction writers, with little relevance to modern theoretical physics. But the idea that we live in a “multiverse” made up of an infinite number of parallel universes has long been considered a scientific possibility – although it is still a matter of vigorous debate among physicists. The race is now on to find a way to test the theory, including searching the sky for signs of collisions with other universes.