Simple Math Could Bridge Quantum Mechanics and General Relativity

One of the great problems of modern physics has been the failure to reconcile the theory of quantum mechanics, which deals with the behavior of fundamental particles, with Einstein’s general theory of relativity, which describes gravity and therefore the behavior of things on a larger scale.  There are some inherent contradictions in the two theories that suggest areas where our understanding is incomplete.

This article at the Scientific American website discusses a recent paper that uses "simple math" to "present a straightforward way for quantum particles to move smoothly from one kind of ‘topological space’ to a very different one."  The article notes that while this may present progress in the reconciliation of the two theories, there is no claim the the theories have been brought together in unifying a theory of quantum gravity:

The analysis does not model gravity explicitly, and so is not an attempt to formulate a theory of ‘quantum gravity’ that brings general relativity and quantum mechanics under one umbrella. Instead, the authors, including Nobel laureate Frank Wilczek of the Massachusetts Institute of Technology (MIT) in Cambridge, suggest that their work might provide a simplified framework for understanding the effects of gravity on quantum particles, as well as describing other situations in which the spaces that quantum particles move in can radically alter, such as in condensed-matter-physics experiments.

The original paper can be found here. 

Brian Greene offers explanation on the Higgs field and mass

The following post by Brian Greene offers additional (and very interesting) insight into the Higgs field and how fundamental particles derive mass.  In short most of the mass that exists in everyday objects made up of atoms does not come from the Higgs field, but instead results from the nuclear forces inside of the atoms ("gluons").  Because energy and mass are interchangeable this energy imparts the vast majority of the mass to the particles that make up atoms.

Hi Everyone,

Following up on my somewhat cryptic statement on twitter (@bgreene), I want to briefly explain a point about the Higgs idea that, on a few occasions, I’ve seen incorrectly reported.

The Higgs field provides mass to fundamental particles like electrons and quarks, and that’s extremely important. But when it comes to the mass of ordinary matter such as you and me and trucks and baseballs, most of the mass does not arise from the Higgs field.

Ordinary matter is made from atoms, whose mass mainly comes from protons and neutrons—which, in turn, are each made from three quarks. But if you add up the masses of the quarks (whose mass comes from the Higgs) the total is only a few percent of the mass of a proton or neutron. So where does the bulk of the mass of protons and neutrons come from?

The answer comes from Einstein’s famous E = mc^2, written in the equivalent but more illuminating form m = E/c^2, where it establishes that energy (E) yields mass (m). The quarks inside a proton are held together by a kind of nuclear glue (“gluons”), and that glue that harbors significant energy. Indeed, most of the mass of protons (and neutrons) comes from that energy.

So, while the Higgs gives mass to the quarks and other fundamental particles, it’s the energy of the gluons that is responsible for most of the mass of the protons and neutrons, and hence the mass of familiar matter.

--Brian Greene

More on the Higgs Boson

Below is an extended description of the Higgs Boson (and field) by Dr. Ed Copeland of the University of Nothingham and Sixty Symbols. The interviews also include discussion of who will receive a Nobel Prize if the Higgs is discovered:

 

Brian Greene on the Higgs at the Aspen Ideas Festival last week


In this clip from NOVA’s The Fabric of the Cosmos with Brian Greene, Peter Higgs himself explains the origins of the hypothetical elementary particle that could help explain how matter was created:

Watch The Higgs Particle Matters on PBS. See more from NOVA.

Modified theory of gravity or dark matter?

There was a time when the idea of dark matter pervading the universe was considered by most cosmologists as a radical theory not to be taken very seriously. However, over time ever more evidence from observations of galaxies, and galaxy clusters and the afterglow of the big bang pointed to the existence of dark matter.

Despite the adoption of dark matter as the best current explanation for observations, some researchers prefer an idea known as Modified Newtonian Dynamics (MOND) which is basically a theory that gravity works a little differently than currently understood on larger scales.

In this paper, Stacy McGaugh, an astronomer at the University of Maryland, College Park, reports that MOND can explain an observed correlation between the mass and the rotation speed of galaxies. McGaugh gathered data from various sources on 47 galaxies that contain more hydrogen gas than stars. The mass of the gas can then be estimated directly. McGaugh made a plot of visible mass versus rotation speed for the galaxies. He then plotted the prediction that comes straight out of MOND in a few lines of algebra. The MOND line went right through the data. "You draw the line and the data fall right on it," McGaugh says. "No muss, no fuss." He reports the result in a paper in press at Physical Review Letters.

Does this mean gravity may work differently on large scales, and that observations of large scale structures in the universe may be explained without invoking dark matter? Most astronomers would still say the evidence for dark matter is too strong for the theory to be discarded, but some believe the jury is still out on the dark matter verdict.

More Evidence Against Dark Matter?

Gravity Doesn't Exist?

This paper argues that gravity "doesn't exist." More specifically the author Erik Verlinde, described by the New York Times as a respected string theorist and professor of physics at the University of Amsterdam, says gravity is emergent from the laws of thermodynamics.

If you have difficulty understanding the paper, do not be alarmed, according to this article in the Times: "some of the best physicists in the world say they don’t understand Dr. Verlinde’s paper, and many are outright skeptical."