From Katia Moskvitch at Quanta:
The neutron-star collision was just the beginning. New data in the months since that discovery have made life increasingly difficult for the proponents of many of the modified-gravity theories that remain. Astronomers have analyzed extreme astronomical systems that contain spinning neutron stars, or pulsars, to look for discrepancies between their motion and the predictions of general relativity — discrepancies that some theories of alternative gravity anticipate. These pulsar systems let astronomers probe gravity on a new scale and with new precision. And with each new observation, these alternative theories of gravity are having an increasingly hard time solving the problems they were invented for. Researchers “have to sweat some more trying to get new physics,” said Anne Archibald, an astrophysicist at the University of Amsterdam.
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?” More.
But at least they recognize and admit it. There is no shame in being wrong. Admitting it puts us on the road to being right.
“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. More.
See also: Proposed dark matter solution: “Gravity is not a fundamental governance of our universe, but instead a reaction to the makeup of a given environment.” Dark matter could be the answer to a number of cosmology questions but it could also be the phlogiston or ether of today’s science – substances that were assumed to exist because their existence would solve a problem but th problem was not properly understood. When it was, no one needed those substances to exist. Time will tell, we hope.
Supernova analysis questions dark energy cosmic acceleration
Take back Nobel prizes for accelerating expansion of universe? Dark energy might be an illusion say some researchers. But we thought only a denialist was allowed to doubt the accelerating expansion of the universe. Rules change?
Post-modern physics: String theory gets over the need for evidence
6 Replies to “Alternatives to Einstein’s gravity face challenges from evidence”
What is spacetime made of again? I’d like to see the physical evidence for its existence. Einsteinian physics is just math and zero physics. It explains nothing. In fact, it conjures up all sorts of pseudoscientific magic to explain why gravity appears to act instantaneously at a distance (as Newton correctly assumed) even though it is hypothesized to propagate at c.
The fact is that both Einsteinian and Newtonian gravity theories are falsified because they cannot explain the rotational velocity of galaxies without invoking some invisible or otherwise undetectable dark matter.
Isn’t it more accurate to say that they predict the existance of dark matter?
Yet GPS systems are based on Einsteinian physics.
The existence of spacetime? Um, buy a big clock? 🙂
Of related interest,
There are two fairly profound problems with physicists hoping to find some type of variance in the universal constants of nature so as to confirm their exotic theories. Number 1, Atheistic Naturalism/Materialism itself has no clue why the universal constants should be constant in the first place. In fact, modern science was born out of the Christian presupposition that there should be unchanging universal laws governing the universe.
Moreover, most atheists do not seem to realize that if the universal constants were actually found to have even a small variance in them, as they presuppose, then this would destroy our ability to practice science rationally, for it would undermine our ability to mathematically model the universe in a reliable fashion. For example, if the speed of light constant, or if the invisible glue that holds nuclei together, varied, e=mc2 would be totally useless to us as a reliable description of reality:
Of related note, although it would destroy our ability to do science if the universal constants were found to have some type of unpredictable variance, it is interesting to note that Darwinian evolution itself is not based on any known universal constant but is based on “unpredictable’ randomness, and that is the primary reason it is, as Murray Eden pointed out, ‘inadequate’ as a scientific theory:
Professor Murray Eden of MIT, in a paper entitled “Inadequacies of Neo-Darwinian Evolution as a Scientific Theory” stated that “the randomness postulate is highly implausible and that an adequate scientific theory of evolution must await the discovery and elucidation of new natural laws—physical, physico-chemical, and biological.”
,,Moreover, presupposing that randomness and/or chaos can produce the unchanging universal constants of the universe, as the Atheistic Naturalists ultimately believes in his multiverse scenarios, is a direct contradiction that borders on sheer insanity. It is equivalent to someone believing down is up, and black is white.
Whereas, on the other hand, Christian Theism predicts the constants of the universe to be unchanging. For instance Christianity predicts the universe to be “flat”, whereas atheists have no clue why it is flat:
Bob O’H @3: The existence of spacetime? Um, buy a big clock?
Did you know that nothing can move in spacetime by definition? Do you know why Karl Popper called spacetime “Einstein’s block universe in which nothing happens?” Obviously not.
You have not answered my question. What is spacetime made of? Or, as Kant would succinctly put it, if spacetime exists, where is it?
Food for thought: