The Universe Doesn’t Need Dark Energy To Expand Faster, Says New Theory
Mathematicians argue in a new paper that the accelerating expansion of the universe can be explained without dark energy.
“Dark energy” is a mysterious force that is predicted to take up more than 68% of our universe. Since observations in 1990s that the expansion of the universe is accelerating, dark energy has been the leading hypothesis to explain why. Now three mathematicians claim they can show why the expansion is speeding up without the need to invoke dark energy, which they call "a fudge factor".
The idea of dark energy is linked to Einstein’s Theory of General Relativity. Believing in 1917 that the universe was static and looking to address the issue of “vacuum energy”, Einstein added a cosmological constant to represent an anti-gravitational force. When the fact of universe’s expansion was confirmed, Einstein shelved the constant, calling it his greatest mistake.
But in order to explain why the expansion is speeding up, the idea of the cosmological constant came back into fashion as being interchangeable with dark energy - a fact that did not sit well with Blake Temple and Zeke Vogler from the UC Davis and Joel Smoller from the University of Michigan, Ann Arbor. In their new paper they argue that invoking dark energy is not necessary since Einstein’s equations in the original theory of General Relativity are correct. What needs adjusting is the idea that the universe expands in a uniform way.
“We set out to find the best explanation we could come up with for the anomalous acceleration of the galaxies within Einstein’s original theory without dark energy,” said Temple.
The mathematicians explain that cosmological models based on Friedmann equations, which govern the expansion of space in the universe, assume that matter is expanding evenly throughout. But the equations actually show this kind of space-time model is unstable, propose the scientists. Any disturbance will put it into acceleration.
The scientists says that the universe as a whole cannot be measured as one static entity, as its inherent instability prevents that. Instead, you can measure local space-times created by the instability. These would have the same cosmic accelerations as in the theories of dark energy, maintain the mathematicians.
“The math isn’t controversial, the instability isn’t controversial,” Temple said. “What we don’t know is, does our Milky Way galaxy lie near the center of a large under-density of matter in the universe.”
Their paper also includes predictions that can be tested to separate their model from dark energy models.
You can read the paper in the Proceedings of the Royal Society A.
Want to know more about dark energy? Check out this video:
What can 3D printing do for medicine? The "sky is the limit," says Northwell Health researcher Dr. Todd Goldstein.
- Medical professionals are currently using 3D printers to create prosthetics and patient-specific organ models that doctors can use to prepare for surgery.
- Eventually, scientists hope to print patient-specific organs that can be transplanted safely into the human body.
- Northwell Health, New York State's largest health care provider, is pioneering 3D printing in medicine in three key ways.
Torn between absolutism on the left and the right, classical liberalism—with its core values of compassion and incremental progress whereby the once-radical becomes the mainstream—is in need of a good defense. And Adam Gopnik is its lawyer.
- Liberalism as "radical pragmatism"
- Intersectionality and civic discourse
- How "a thousand small sanities" tackled drunk driving, normalized gay marriage, and could control gun violence
As Game of Thrones ends, a revealing resolution to its perplexing geography.
- The fantasy world of Game of Thrones was inspired by real places and events.
- But the map of Westeros is a good example of the perplexing relation between fantasy and reality.
- Like Britain, it has a Wall in the North, but the map only really clicks into place if you add Ireland.
The lost practice of face-to-face communication has made the world a more extreme place.
- The world was saner when we spoke face-to-face, argues John Cameron Mitchell. Not looking someone in the eye when you talk to them raises the potential for miscommunication and conflict.
- Social media has been an incredible force for activism and human rights, but it's also negatively affected our relationship with the media. We are now bombarded 24/7 with news that either drives us to anger or apathy.
- Sitting behind a screen makes polarization worse, and polarization is fertile ground for conspiracy theories and fascism, which Cameron describes as irrationally blaming someone else for your problems.
SMARTER FASTER trademarks owned by The Big Think, Inc. All rights reserved.