The Newtonian and Einsteinian theories are often praised for their "astounding" predictive power, yet are unable to explain the motions and movements of the stellar systems of the universe.
Galaxy Uniform Cohesion
Galaxies are observed to spin as if they were solid disks, but according to theory, the center of the galaxy should be spinning much faster than the edges. In order to explain the rotation of galaxies modern astronomers need the entire galaxy filled with some kind of substance which holds the stars strongly together.
“ According to theory, a galaxy should rotate faster at the center than at the edges. This is similar to how an ice-skater rotates: when she extends her arms she moves more slowly, when she either extends her arms above her head or keeps them close to the body she starts to rotate more rapidly. Taking into consideration how gravitation connects the stars in the galaxy the predicted result is that average orbital speed of a star at a specified distance away from the center would decrease inversely with the square root of the radius of the orbit (the dashed line, A, in figure below). However observations show that the galaxy rotates as if it is a solid disk as if stars are much more strongly connected to each other (the solid line, B, in the figure below). ”
Galaxy Rotation Rate
In addition, Galaxies as a whole are observed to spin too fast for their alleged size, beyond the point where, according to theory, the stars should fly away from each other.
“ In the 1930s, Swiss astronomer Fritz Zwicky first observed that some galaxies were spinning so fast that the stars in them should fly away from each other. Unfortunately, Zwicky had personality clashes with many in the astronomy community, so his views weren’t taken very seriously.
In 1962, astronomer Vera Rubin made the same discoveries and had nearly the same outcome. Though Rubin didn’t have the same issues of temperament that Zwicky did, many disregarded her work because she was a woman. Rubin maintained her focus on the problem and, by 1978, had studied 11 spiral galaxies, all of which (including our own Milky Way) were spinning so fast that the laws of physics said they should fly apart. Together with work from others, this was enough to convince the astronomy community that something strange was happening. ”
Distaste of the Scientific Community
“ For decades, astronomers have noticed that the behavior of galaxies and galaxy clusters doesn’t seem to fit the predictions of general relativity. Dark matter is one way to explain that behavior. Likewise, the accelerating expansion of the universe can be thought of as being powered by a dark energy.
All attempts to directly detect dark matter and dark energy have failed, however. That fact “kind of leaves a bad taste in some people’s mouths, almost like the fictional planet Vulcan,” said Leo Stein, a theoretical physicist at the California Institute of Technology. “Maybe we’re going about it all wrong?”
For any alternative theory of gravity to work, it has to not only do away with dark matter and dark energy, but also reproduce the predictions of general relativity in all the standard contexts. “The business of alternative gravity theories is a messy one,” Archibald said. Some would-be replacements for general relativity, like string theory and loop quantum gravity, don’t offer testable predictions. Others “make predictions that are spectacularly wrong, so the theorists have to devise some kind of a screening mechanism to hide the wrong prediction on scales we can actually test,” she said. ”