DETF as a career counselor
Another wayside village on the road to the thesis topic is the previously mentioned Dark Energy Task Force report published on June 6 (6/6/06 for you doomsters). This "task force" was created as a combination of two science advisory counsels (like the ones who brought you the food pyramid) to report to the DOE, NASA ,and NSF on what they should do about figuring out Dark Energy. They are reporting mainly to scientists who now wear manager hats so they need a combination of good detective work for the ones who are still or recently were scientists and good beaurocratese for the ones who control the money.
Now, why should time and management be spent on a slight curvature of a nominally straight hubble flow graph? Because whatever makes that curve possible represents a very large departure from either the standard model, the particle physicists golden T-Shirt or the miraculas general relativity solution. A large departure from a well established theory seems to always earn us physicists a gold star, once its understood. Another reason the problem is so "vexing", to use the words of the Quarks to Cosmos top ten problems list, is that in the last thirty years the physics community has seen the creation of an entire new branch on their scale invarient tree. Some of the smartest most competitive minds in the physics world from places like theoretical gravity, so called "high energy" (particle physics), and plain old astronomers are now Cosmologists. This community occupies the central area of the physics Venn Diagram. In many cases these people have other interests and retain titular roles in their former areas but in reality compete mainly in the cosmology arena.
This field became largely popular with the discovery of the CMB and its variations but really exploded with the discovery of the problem of the "missing mass". Thus begins the perfectly exeptable practice of validating one theory (supersymmetry) with the postulates of another, Dark Matter = missing mass. Using one and other as crutches to prove theories otherwise unprovable at that time, theoretical astrophysicists and particle physicists founded a new Commonweal. Recall as well the rising popularity of so-called "multidisciplinary" work. This was an age where large "consortiums" of scientists struggled to add their thin veneer to the towering pile of paradigm built by their fathers and one monthly journal in the nineteenth century had become ten. The habits and traditions built then are bearing fruit today where thousands of papers a year are published electronically or in numerous and divers peer reviewed journals on possible configurations of alternative gravity, quantum fields, strings, branes, and on and on; all to solve this problem of why the hubble flow is curved.
This Task Force is a physicists response to this glut of theory by saying, "Hey wait, we're empiricists, lets measure this!" Of course no one ever really stopped measuring the universe, as evidenced by the "stage II" (now projects) listed in the report, but noone ever really sat down and thought about proving more than yes there is a problem.
What this paper draws out is a practical four part program for figuring out what is causing that curve. Each part is a different way of measuring properties of objects like their brightness, shape or size. Using this information one might be able to back out a "observed or intrinsic distance" and by looking at spectral features, might construe also a redshift z. To do this one needs models, as most astrophysics has been based on models for 60 years, this is exactly the way its always been done. A model is simply a way we think the thing (cluster, supernova, etc) works which provides a way to turn what we measure, (spectral features, light curves, etc) into what we want to know (intrinsic distance, velocity, growth factor etc). We then use another model to turn those distances and velocities into an estimate of the cosmological parameters, like the fraction of energy needed to close the universe and the number used by the DETF the "equation of state" parameter. In each case the model we use includes a number of steps where GR plays an important role. This I consider one of the cruxes of the problem. Those on the task force have taken what appears to be a very consensus building position by choosing the dominant model and "going with it", nominally a very sensible modern science decision, but in this case ignoring the fact that their entire empirical approach relies on a theoretical house of cards.
This is the landscape from a young physicist in the sticks. Lots of big fishes competing to be the first to solve the mystery, pushing for big projects and money but the possibility of something fundamental tugs at the mind.
Now, why should time and management be spent on a slight curvature of a nominally straight hubble flow graph? Because whatever makes that curve possible represents a very large departure from either the standard model, the particle physicists golden T-Shirt or the miraculas general relativity solution. A large departure from a well established theory seems to always earn us physicists a gold star, once its understood. Another reason the problem is so "vexing", to use the words of the Quarks to Cosmos top ten problems list, is that in the last thirty years the physics community has seen the creation of an entire new branch on their scale invarient tree. Some of the smartest most competitive minds in the physics world from places like theoretical gravity, so called "high energy" (particle physics), and plain old astronomers are now Cosmologists. This community occupies the central area of the physics Venn Diagram. In many cases these people have other interests and retain titular roles in their former areas but in reality compete mainly in the cosmology arena.
This field became largely popular with the discovery of the CMB and its variations but really exploded with the discovery of the problem of the "missing mass". Thus begins the perfectly exeptable practice of validating one theory (supersymmetry) with the postulates of another, Dark Matter = missing mass. Using one and other as crutches to prove theories otherwise unprovable at that time, theoretical astrophysicists and particle physicists founded a new Commonweal. Recall as well the rising popularity of so-called "multidisciplinary" work. This was an age where large "consortiums" of scientists struggled to add their thin veneer to the towering pile of paradigm built by their fathers and one monthly journal in the nineteenth century had become ten. The habits and traditions built then are bearing fruit today where thousands of papers a year are published electronically or in numerous and divers peer reviewed journals on possible configurations of alternative gravity, quantum fields, strings, branes, and on and on; all to solve this problem of why the hubble flow is curved.
This Task Force is a physicists response to this glut of theory by saying, "Hey wait, we're empiricists, lets measure this!" Of course no one ever really stopped measuring the universe, as evidenced by the "stage II" (now projects) listed in the report, but noone ever really sat down and thought about proving more than yes there is a problem.
What this paper draws out is a practical four part program for figuring out what is causing that curve. Each part is a different way of measuring properties of objects like their brightness, shape or size. Using this information one might be able to back out a "observed or intrinsic distance" and by looking at spectral features, might construe also a redshift z. To do this one needs models, as most astrophysics has been based on models for 60 years, this is exactly the way its always been done. A model is simply a way we think the thing (cluster, supernova, etc) works which provides a way to turn what we measure, (spectral features, light curves, etc) into what we want to know (intrinsic distance, velocity, growth factor etc). We then use another model to turn those distances and velocities into an estimate of the cosmological parameters, like the fraction of energy needed to close the universe and the number used by the DETF the "equation of state" parameter. In each case the model we use includes a number of steps where GR plays an important role. This I consider one of the cruxes of the problem. Those on the task force have taken what appears to be a very consensus building position by choosing the dominant model and "going with it", nominally a very sensible modern science decision, but in this case ignoring the fact that their entire empirical approach relies on a theoretical house of cards.
This is the landscape from a young physicist in the sticks. Lots of big fishes competing to be the first to solve the mystery, pushing for big projects and money but the possibility of something fundamental tugs at the mind.
posted by Danny at 1:40 PM
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