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Physicists and Philosophers Hold Peace Talks If only for three days

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Physicists typically think they “need philosophers and historians of science like birds need ornithologists,” the Nobel laureate David Gross told a roomful of philosophers, historians, and physicists in Munich, Germany, paraphrasing Richard Feynman.

But desperate times call for desperate measures.

Fundamental physics faces a problem, Gross explained—one dire enough to call for outsiders’ perspectives. “I’m not sure that we don’t need each other at this point in time,” he said.

It was the opening session of a three-day workshop, held on December 7 in a Romanesque-style lecture hall at Ludwig Maximilian University (LMU Munich) one year after George Ellis and Joe Silk, two white-haired physicists now sitting in the front row, called for such a conference in an incendiary opinion piece in Nature. One hundred attendees had descended on a land with a celebrated tradition in both physics and the philosophy of science to wage what Ellis and Silk declared a “battle for the heart and soul of physics.”

 

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Why String Theory Is Not Science

undefinedImage credit: flickr user Trailfan, via https://www.flickr.com/photos/7725050@N06/631503428.

Ethan Siegel, CONTRIBUTOR

There are a lot of different ways to define science, but perhaps one that everyone can agree on is that it’s a process by which:

knowledge about the natural world or a particular phenomenon is gathered,
a testable hypothesis is put forth concerning a natural, physical explanation for that phenomenon,
that hypothesis is then tested and either validated or falsified,
and an overarching framework — or scientific theory — is constructed to explain the hypothesis and that makes predictions about other phenomena,
which is then tested further, and either validated, in which case new phenomena to test are sought (back to step 3), or falsified, in which case a new testable hypothesis is put forth (back to step 2)…

and so on. This scientific process always involves the continued gathering of more data, the continued refining or outright replacing of hypotheses when the realm of validity of the theory is exceeded, and testing that subjects that theory to either further validation or potential falsification.

 

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Is String Theory Science?

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The idea that our Universe is part of a multiverse poses a challenge to philosophers of science.
Credit: R. Windhorst, Arizona State Univ./H. Yan, Spitzer Science Center, Caltech/ESA/NASA

 

A debate between physicists and philosophers could redefine the scientific method and our understanding of the universe
By Davide Castelvecchi, Nature magazine on December 23, 2015

Is string theory science? Physicists and cosmologists have been debating the question for the past decade. Now the community is looking to philosophy for help.
Earlier this month, some of the feuding physicists met with philosophers of science at an unusual workshop aimed at addressing the accusation that branches of theoretical physics have become detached from the realities of experimental science. At stake is the integrity of the scientific method, as well as the reputation of science among the general public, say the workshop’s organizers.
Held at the Ludwig Maximilian University of Munich in Germany on December 7-9, the workshop came about as a result of an article in Nature a year ago, in which cosmologist George Ellis, of the University of Cape Town in South Africa, and astronomer Joseph Silk, of Johns Hopkins University in Baltimore, Maryland, lamented a “worrying turn” in theoretical physics (G. Ellis and J. Silk Nature 516, 321–323; 2014).

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What Are Quantum Gravity's Alternatives To String Theory?

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Image credit: CPEP (Contemporary Physics Education Project), NSF/DOE/LBNL.

 

The Universe we know and love — with Einstein’s General Relativity as our theory of gravity and quantum field theories of the other three forces — has a problem that we don’t often talk about: it’s incomplete, and we know it. Einstein’s theory on its own is just fine, describing how matter-and-energy relate to the curvature of space-and-time. Quantum field theories on their own are fine as well, describing how particles interact and experience forces. Normally, the quantum field theory calculations are done in flat space, where spacetime isn’t curved. We can do them in the curved space described by Einstein’s theory of gravity as well (although they’re harder — but not impossible — to do), which is known as semi-classical gravity. This is how we calculate things like Hawking radiation and black hole decay.

But even that semi-classical treatment is only valid near and outside the black hole’s event horizon, not at the location where gravity is truly at its strongest: at the singularities (or the mathematically nonsensical predictions) theorized to be at the center. There are multiple physical instances where we need a quantum theory of gravity, all having to do with strong gravitational physics on the smallest of scales: at tiny, quantum distances. Important questions, such as:

What happens to the gravitational field of an electron when it passes through a double slit?
What happens to the information of the particles that form a black hole, if the black hole’s eventual state is thermal radiation?
And what is the behavior of a gravitational field/force at and around a singularity?

 

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The quantum source of space-time

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Black holes such as the one depicted in Interstellar (2014) can be connected by wormholes, which might have quantum origins.

Many physicists believe that entanglement is the essence of quantum weirdness — and some now suspect that it may also be the essence of space-time geometry.

Ron Cowen

16 November 2015

In early 2009, determined to make the most of his first sabbatical from teaching, Mark Van Raamsdonk decided to tackle one of the deepest mysteries in physics: the relationship between quantum mechanics and gravity. After a year of work and consultation with colleagues, he submitted a paper on the topic to the Journal of High Energy Physics.

In April 2010, the journal sent him a rejection — with a referee’s report implying that Van Raamsdonk, a physicist at the University of British Columbia in Vancouver, was a crackpot.

His next submission, to General Relativity and Gravitation, fared little better: the referee’s report was scathing, and the journal’s editor asked for a complete rewrite.

But by then, Van Raamsdonk had entered a shorter version of the paper into a prestigious annual essay contest run by the Gravity Research Foundation in Wellesley, Massachusetts. Not only did he win first prize, but he also got to savour a particularly satisfying irony: the honour included guaranteed publication in General Relativity and Gravitation. The journal published the shorter essay1 in June 2010.

 

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