As a measure how far can this be taken? Some like to think like Smolin, and Smolin's reference to Glast is a important one:)This defines his limits.
Others, have decided to go beyond this.:)
Some of Lee's points can be agreed with, for example:
It is desirable to find a background independent formulation of string/M-theory
Such a formulation would likely to answer the questions whether the landscape approach to string/M-theory is correct; why it's not; what it should be replaced with.
An attempt to revive Mach's principle means to argue that the gravitational waves do not exist. It is a struggle to return us not only before General Relativity; it is a program to return the humankind to the pre-Newtonian era and the dark Middle Ages. Some people may be permanently impressed by Mach's principle and some people may find it shallow after a closer scrutiny. These two groups may be composed of equally nice people. But the difference is that the critics of Mach's principle have a good physical intuition; its advocates are philosophers who are unable to think analytically and quantitatively and they prefer to insist on prejudices that can be shown flawed by a five-minute-long quantitative argument.
OK, let me start with the questions about relationism and Mach's principle. I highly recommend you the second popular book by Brian Greene, "The Fabric of the Cosmos", where the relative vs. absolute debate is covered in the first chapters. And the presentation is very nice.
The aim of this paper is to explain carefully the arguments behind the assertion that the correct quantum theory of gravity must be background independent. We begin by recounting how the debate over whether quantum gravity must be background independent is a continuation of a long-standing argument in the history of physics and philosophy over whether space and time are relational or absolute. This leads to a careful statement of what physicists mean when we speak of background independence. Given this we can characterize the precise sense in which general relativity is a background independent theory. The leading background independent approaches to quantum gravity are then discussed, including causal set models, loop quantum gravity and dynamical triangulations and their main achievements are summarized along with the problems that remain open. Some first attempts to cast string/M theory into a background independent formulation are also mentioned.
The relational/absolute debate has implications also for other issues such as unification and how the parameters of the standard models of physics and cosmology are to be explained. The recent issues concerning the string theory landscape are reviewed and it is argued that they can only be resolved within the context of a background independent formulation. Finally, we review some recent proposals to make quantum theory more relational.
The calorimeter design for GLAST produces flashes of light that are used to determine how much energy is in each gamma-ray. A calorimeter ("calorie-meter") is a device that measures the energy (heat: calor) of a particle when it is totally absorbed.
While some people are looking for consistant means of determinations, others apply "conceptual situations" and bring forth comprehension of a kind. Now to this degree, that "gluonic perception is being adjusted" to see these values. The Smolins and others understood well the limitation of these views? Are there any?
All of the structures we observe in Saturn's radio spectrum are giving us clues about what might be going on in the source of the radio emissions above Saturn's auroras," said Dr. Bill Kurth, deputy principal investigator for the instrument. He is with the University of Iowa, Iowa City. Kurth made the discovery along with Principal Investigator Don Gurnett, a professor at the University. "We believe that the changing frequencies are related to tiny radio sources moving up and down along Saturn's magnetic field lines."
The auroral ionosphere is a natural emitter of radio waves, and many of these emissions are observable at ground level. Several types of radio emissions have been well documented using a variety of ground-based, stepped-frequency receivers (see reviews by LaBelle [1989] and LaBelle and Weatherwax, [1992]). In particular, auroral roar is a relatively narrowband emission at roughly 2 and 3 times the local electron cyclotron frequency ( ) [Kellogg and Monson, 1979; Kellogg and Monson, 1984; Weatherwax et al., 1993, 1995]. Much effort has been made in characterizing the seasonal, diurnal, and spectral characteristics of auroral roar to aid in determining its generation mechanism [e.g., Weatherwax et al., 1995.
THEMIS's ground network of all sky imagers will have the density and time resolution to detect auroral onset within 10s and 0.5 degrees of longitude. The University of Calgary will deploy 16 imagers across Canada, combined with imagers in Alaska the THEMIS array will consist of 20 ground-based observatories (GBOs). Each GBO will consist of a white light all sky camera and a host of support equipment such as a computer, GPS antenna, and a satellite dish (in the event that an internet connection is not available at the site). [more information on GBOs]
Astronaut's view of the Aurora Australis, or southern lights, from aboard Space Shuttle Discovery 1991 (Courtesy: NASA)
Mathematics is not the rigid and rigidity-producing schema that the layman thinks it is; rather, in it we find ourselves at that meeting point of constraint and freedom that is the very essence of human nature.- Hermann Weyl
However, Hawking's semiclassical calculation leads to an exactly (piecewise) thermal final state. Such a mixed state in the far future violates unitarity - pure states cannot evolve into mixed states unitarily - and it destroys the initial information about the collapsed objects which is why we call it "information loss puzzle". A tension with quantum mechanics emerges.
It was worry about the possibility that string theory would lead to the present situation, which Susskind has so ably described in his recent papers, that led me to invent the Cosmological Natural Selection [CNS] idea and to write my first book. My motive, then as now, is to prevent a split in the community of theoretical physicists in which different groups of smart people believe different things, with no recourse to come to consensus by rational argument from the evidence.
The purpose of this note is to provide a possible answer to this question. Rather than the radical modification of quantum mechanics required for pure states to evolve into mixed states, we adopt a more mild modification. We propose that at the black hole singularity one needs to impose a unique final state boundary condition. More precisely, we have a unique final wavefunction for the interior of the black hole. Modifications of quantum mechanics where one imposes final state boundary conditions were considered in [6,7,8,9]. Here we are putting a final state boundary condition on part of the system, the interior of the black hole. This final boundary condition makes sure that no information is “absorbed” by the singularity.
(a) Compactifying a 3-D universe with two space dimensions and one time dimension. This is a simplification of the 5-D spacetime considered by Theodor Kaluza and Oskar Klein. (b) The Lorentz symmetry of the large dimension is broken by the compactification and all that remains is 2-D space plus the U(1) symmetry represented by the arrow. (c) On large scales we see only a 2-D universe (one space plus one time dimension) with the "internal" U(1) symmetry of electromagnetism.
If conceived as a series of ever-wider experiential contexts, nested one within the other like a set of Chinese boxes, consciousness can be thought of as wrapping back around on itself in such a way that the outermost 'context' is indistinguishable from the innermost 'content' - a structure for which we coined the term 'liminocentric'.
The goal of ISCAP is to bring together theoretical physicists, astrophysicists, and observational astronomers to address key problems in particle physics and cosmology that require a broad confluence of expertise and perspective.
"The gravitons behave like sound in a metal sheet," says Dvali. "Hitting the sheet with a hammer creates a sound wave that travels along its surface. But the sound propagation is not exactly two-dimensional as part of the energy is lost into the surrounding air. Near the hammer, the loss of energy is small, but further away, it's more significant."
Here’s an analogy to understand this: imagine that our universe is a two-dimensional pool table, which you look down on from the third spatial dimension. When the billiard balls collide on the table, they scatter into new trajectories across the surface. But we also hear the click of sound as they impact: that’s collision energy being radiated into a third dimension above and beyond the surface. In this picture, the billiard balls are like protons and neutrons, and the sound wave behaves like the graviton.
If conceived as a series of ever-wider experiential contexts, nested one within the other like a set of Chinese boxes, consciousness can be thought of as wrapping back around on itself in such a way that the outermost 'context' is indistinguishable from the innermost 'content' - a structure for which we coined the term 'liminocentric'.
In this setting of the spherical mass M, we define the value rS = 2M as the Schwarzschild radius of the mass. If the mass has a radius less than rS, then it is called a black hole. In that case, the surface r =rS is called the event horizon of the black hole.
A circle of radius r has a curvature of size 1/r. Therefore, small circles have large curvature and large circles have small curvature. The curvature of a line is 0. In general, an object with zero curvature is "flat."
The familiar extended dimensions, therefore, may very well also be in the shape of circles and hence subject to the R and 1/R physical identification of string theory. To put some rough numbers in, if the familiar dimensions are circular then their radii must be about as large as 15 billion light-years, which is about ten trillion trillion trillion trillion trillion (R= 1061) times the Planck length, and growing as the universe explands. If string theory is right, this is physically identical to the familiar dimensions being circular with incredibly tiny radii of about 1/R=1/1061=10-61 times the Planck length! There are our well-known familiar dimensions in an alternate description provided by string theory. [Greene's emphasis]. In fact, in the reciprocal language, these tiny circles are getting ever smaller as time goes by, since as R grows, 1/R shrinks. Now we seem to have really gone off the deep end. How can this possibly be true? How can a six-foot tall human being 'fit' inside such an unbelievably microscopic universe? How can a speck of a universe be physically identical to the great expanse we view in the heavens above? (Greene, The Elegant Universe, pages 248-249)
Physics at this high energy scale describes the universe as it existed during the first moments of the Big Bang. These high energy scales are completely beyond the range which can be created in the particle accelerators we currently have (or will have in the foreseeable future.) Most of the physical theories that we use to understand the universe that we live in also break down at the Planck scale. However, string theory shows unique promise in being able to describe the physics of the Planck scale and the Big Bang.