ATLAS Mural

ATALAS commissioned an impressive mural of their detector that has just been completed. Artist Josef Kristofoletti created the massive mural of the Large Hadron Collider's ATLAS detector on the outside wall of loop point 01. The mural was commissioned by the ATALAS experiment after Kristofoletti first painted a similar, though much smaller, mural on the side of the Redux Contemporary Art Center in Charleston, South Carolina. Kristofoletti found inspiration for the art by merging his enjoyment of classic Italian Renaissance murals and his life long fascination with science. He says that the humongous size of ATALAS and the tiny particles it finds make the Large Hadron Collider fascinating, like an unprecedented modern cathedral of science. The event depicted in the mural shows an actual event recorded by ATALAS of a Z boson decay into two muons.

There are more concept pictures here or finished pictures from CERN here.

Skeptical: Philosophical Umpire

Making good decisions is complicated. Game theory applies logic and mathematics to determine the optimal course of action for individuals when acting in the presence of other participants. Now, individual actions must take into account logic, morals, and personal preference, but there are general rules or situations in which the optimal course of action is clear. This comic (or infographic?) by SMBC illustrates the application of game theory to a classic problem, the prisoners dilemma, and by extension morality.

The prisoners dilemma is a great way to find your moral compass. We can apply a similar decision matrix as used above to many different kinds of situations, like Pascal's wager, where one attempts to bet on the existence of God. The logic of pascal's wager concludes that one should believe, or at least act as if one believes in God (this result is unsatisfactory to many, but wait I have a response). I was recently considering applying a decision matrix to answer the question, 'Should you believe in science?' There are other ways to phrase the question, like 'Should you be a skeptic?' or 'Should you follow logic?' Decision theory gets tricky here. In order to answer the question I recalled an analogy a professor used in a philosophy class I took long ago. My professor wanted us to consider a philosophical umpire calling a game. The umpire could either state that she was very vigilant such that she, 'calls em as I see em' (admitting fallibility), or the umpire could say that, 'I call them as they are' (denial of fallibility).  In the situation before replays I could almost see the umpire taking either stance with reason because they are the final arbiter on the field. In this modern age it is completely untenable for an umpire to state that she calls everything'as they are because replays are available. In life any experience that can be repeated is like a game with replays; an experiment is a game with replays. We all must be like the philosophical umpire and we can reason out how to behave using these ideas.

Below I have made a logic table. On the left vertical axis is the true outcome of an event with respect to how you perceived it and on the top horizontal axis is how you see yourself judging the event. The conclusion of the table is that application of the scientific method is really powerful. Admitting that you make errors in judgement means that you always allow potential for improvements in the future outcomes, but insistence on being right leads you to a false world view. I think that scientists, skeptics, and atheist have essentially the same goal and are all standing in the top right corner there jumping up and down trying to get people to choose to be skeptical.

	'calls em as I see em' (skeptic)	'calls em as they are'
right	positive result, skeptic world view, positive future results positive result, superficially correct world view, positive future results negative result, skeptic world view, potential for improved future results negative result, false world view, negative future results
wrong

It almost seem to be a tautology that logic says you should use logic to understand the world. This decision matrix casts doubt on the result of all other decision matrices like Pascal's wager such that we can escape being certain that belief in God is best, but simultaneously this result casts doubt on itself. Paradoxically what this really seems to say is that you should be skeptical about being skeptical.

Magnetic Fields in Cosmology

The existence of magnetic fields on cosmologically large scales is an unsolved problem in astrophysics. Theory favors a universe that did not begin with any magnetic fields present and classical magnetohydrodynamics restricts the spontaneous emergence of a magnetic state under the influence of ideal forces. In a paper entitled Twisting Space-Time: Relativistic Origin of Seed Magnetic Field and Vorticity appearing Physical Review letters Swadesh Mahajan and Zensho Yoshida propose a universal magnetic field generating effect using ideal special relativistic fluid dynamics. Mahajan and Yoshida's insight was that in describing magnetic fields, which are mathematically equivalent to a vorticity, a careful application of ideal dynamics in the framework of distortions caused by special relativity may result in the spontaneous emergence of a magnetic state in contrast to the previous theoretical result.

Magnetic fields are found to be important in every scale hierarchy of the universe. Most notably detailed images of galaxies paradoxically display regions of chaotic turbulence and beautiful grand coherent designs at once. Thus it is clear that turbulent motion on scales below hundreds of parsecs does not necessarily destroy coherent optical or magnetic features over scales of kiloparsecs. Indeed, magnetic fields are indirectly observed at optical and radio wavelengths by detecting the polarization of the electromagnetic field through the Faraday effect and also by the Zeeman splitting effect. The Faraday effect is the rotation of the linear polarization vector of light which occurs when polarized radiation passes through a magnetized and ionized medium. Radio observations are the most powerful technique and by measuring both the dispersion and polarization rotation the mean of the magnetic field along the line of sight can be measured. Such observations indicate a wide range of magnetic field are present in astrophysics. The image at right below shows the magnetic fields present in M51 which are likely similar in structure and strength to that of the Milky Way.

The total radio continuum emission from the "whirlpool" galaxy M51 (distance estimates range between 13 and 30 million light years) is strongest at the inner edges of the optical spiral arms, probably due to the compression of magnetic fields by density waves. The vectors give the orientations of the regular magnetic fields as derived from the polarized emission. The field lines follow nicely the optical spiral arms. Unexpectedly, strong polarized emission is observed also between the optical arms which indicates the action of a dynamo. This image was observed with the VLA in its most compact configuration at 6cm radio wavelength (broadband continuum). As the VLA cannot detect the diffuse, large-scale radio emission, data from the Effelsberg 100-m telescope in Germany at the same wavelength was added. Investigator(s):  Rainer Beck (MPIfR Bonn, Germany), Cathy Horellou (Onsala Space Observatory). Image courtesy of NRAO/AUI

Microguass fields are present in galaxies at scales of a few kiloparsecs and on the much larger scales of megaparsecs ordered fields of perhaps a few orders of magnitude less are present in galaxy clusters. Magnetic fields in astronomy are controlled by induction of partially ionized gas. A common model for creating these magnetic fields is the dynamo effect wherein an electrically conductive fluid accelerated by some kinetic force generates convective motions in the fluid; it is plausible that a turbulent hydromagnetic dynamo of some kind coupled to an inverse cascade of magnetic energy wold give rise to regular galactic magnetic fields. Following the basic dynamo theory magnetic field lines can be simulated for galaxies which are consistent with observations. The dynamo theory is actually a mechanism for maintaining or growing fields rather than creating them, but it is expected that minuscule primordial magnetic field seeds in the early universe of cosmological origin drive the magnetic fields observed today.

The magnetic dynamo and the primordial magnetic seed theories are both unsatisfactory. The model wherein the the large scale magnetic field in galaxies is the result of the twisting of a cosmological magnetic fields by galactic differential rotation is not satisfactory because a primordial field wound up by differential rotation ultimately decays in an effect known as flux expulsion. The primordial seed theory must explain the presence of large magnetic fields in higher redshift objects when the universe was much younger when the fields should not have had sufficient time to grow. Researchers disagree over what initial primordial field strength is necessary to create the magnetic fields seen today; estimates vary from as large as 10^-9 gauss [1] to 10^-30 gauss [2], but either way an alternative model would be welcome.

Mahajan and Yoshida's work was motivated by the search for a universal mechanism for magnetic field generation. They key to creating a magnetic field is the vorticity of an ionized material which is analyzed in this paper with topological constraints. In mathematical terms fundamental cosmology requires a topological constraint on the vorticity of the universe (consider that you wouldn't expect the universe to have a preferred rotation), however this constraint can be broken by the application of special relativity. The problem of magnetic fields lies in the fact that vorticity must vanish for every ideal force such as the entropy conserving thermodynamic forces (this can be proven though the governing Hamiltonian dynamics of an ideal fluid where ultimately Kelvin's circulation theorem shows that if the initial state has no circulation the later sate will also be vorticity-free). Introduction of the Lorentz factor γ=(1-(v/c)²)^-1/2 from special relativity destroys the exactness of the ideal thermodynamic force and allows spontaneous vorticity.

The authors find a new term that provides a magnetic field growing mechanism as long as the kinetic energy is inhomogeneous. The authors mechanism can provide a finite seed for even mildly relativistic flows. They provide an example for very standard parameters (electron density n=10¹⁰ cm³, temperature T= 20 eV and velocity, v, compared to c of v/c=10^-2) and find their relativistic drive mechanism remains dominate over other effects until magnetic fields of 1 gauss or so which is much larger than most magnetic fields ever observed, thus the relativistic drive is the only dominant effect. The relativistic drive mechanism will likely help us understand, among other things, the origin of magnetic fields in astrophysical and cosmic settings.

References:

[1] Beck, R., Brandenburg, A., Moss, D., Shukurov, A., & Sokoloff, D. (1996). GALACTIC MAGNETISM: Recent Developments and Perspectives Annual Review of Astronomy and Astrophysics, 34 (1), 155-206 DOI: 10.1146/annurev.astro.34.1.155

[2] Davis, A., Lilley, M., & Törnkvist, O. (1999). Relaxing the bounds on primordial magnetic seed fields Physical Review D, 60 (2) DOI: 10.1103/PhysRevD.60.021301

[3] Mahajan, S., & Yoshida, Z. (2010). Twisting Space-Time: Relativistic Origin of Seed Magnetic Field and Vorticity Physical Review Letters, 105 (9) DOI: 10.1103/PhysRevLett.105.095005

The Future History of the Universe

Current observations of our universe indicate that the universe is expanding at an accelerating rate. The expansion of the universe will eventually place all galaxies which are not gravitationally bound to the Milky Way beyond our observable horizon (yet I caution that the notion of a horizon is a subtle point and a source of expanding confusion). Galaxies will cease to be brilliant. The passing of time will see stars exhaust all of their fuel. Stars will cease to shine. Black holes will evaporate due to Hawking radiation dispersing a bath of dull photons into the universe. Black holes will cease to exist. The universe will cool as it expands to a uniformly frigid temperature. Entropy will be maximized. The universe will be cold, dark, and lonely.

The future history of the universe described above is an implicit result of the standard cosmology accepted today. It is an extrapolation of accepted theory into the distant future. There is good reason to be skeptical of extraordinary predictions which is why the big bang and the past expansion history of the universe is the major focus of cosmology and not predicting the future of the universe. We need to know exactly what happened in the past to understand the reasons for the accelerating expansion (what is dark energy?). The current observations and the 'standard cosmology' I speak of are part of what is known in physics as the concordance model of cosmology. Every peer reviewed research paper that discusses the universe has this one sentence in it that goes something like this (taken from generic research paper on cosmology and extragalactic astrophysics):

Throughout this paper we assume a Friedmann-Lemaître-Robertson-Walker metric with a standard cosmology with Ω_M=.3, Ω _Λ=.7, H₀=70 km s^-1 Mpc^-1.

Lets break down this generic statement and see what it implies. The Friedmann-Lemaître-Robertson-Walker metric implies we are assuming a universe which is consistent with a homogeneous isotropic expanding universe, the Ω values are dimensionless energy density parameters which quantify the energy contribution from matter (mostly dark matter, denoted M) and dark energy (denoted Λ), and finally the H₀ value is the Hubble parameter in units of kilometers per second per megaparsec which describes how fast, v, an object at a given distance, d, is moving away from us such that H₀=d/v. The statement effectively means that the universe is flat (it is conceivably possible that you could travel a very long way in one direction and end up where you started, like what happens if you travel around the earth, but observations indicate that this is not the case so we conclude the universe has no curvature) and the universe is expanding in such a way that the universe will not collapse back down on itself. Thus our best guess is that the universe will keep expanding forever. The consequence of this, and this is the crux here, is that as time moves forward entropy inexorably increases (this is the second law of thermodynamics) to the point that all ordered processes, complex systems, life and semblance of thought is impossible.

If you lived forever it would be hard to avoid the situation where eventually you and your fellow space travelers were huddled around a few dieing stars in a bland galaxy in an exhausted void. There are small stars which are burning today and will be burning in 100 billion years and more stars will form for a while. But eventually, stars really will shut down and cool. You could try to travel to another galaxy, but that would take a long time (if the distance to our neighbor galaxy Andromeda was held constant it would take about 2.5 million years to travel there at the speed of light), and even then there would be few stars and most problematically most other galaxies would have receded beyond our horizon. Where would you want to head in this barren universe? Recent studies of the entropy of the universe indicate that the majority of the entropy in the universe is actually contributed by super massive black holes. Interestingly gravity is rather unlike most systems in thermodynamics. Generally entropy is increased by say smashing something into many pieces, but for gravity when energy is uniformly distributed gravity is quite low compared to the state where matter has collapsed into stars or to the extreme state of a black hole. There is one more step in producing more entropy which occurs as black holes slowly emit radiation in the form of Hawking radiation. A black hole the mass of the sun would emit Hawking radiation for 2 × 10⁶⁷ years which is much longer than the current age of the universe at 13.7 × 10⁹ years. A super massive black hole of 100 billion solar masses, about the mass of our entire Milky Way galaxy, would emit Hawking radiation for 2 × 10¹⁰⁰   years. You could hang out near one of these black holes for a while as a source of energy because the black hole would still be producing entropy. Finally, all the black holes would also evaporate and the universe would consist of a diffuse gas of photons and leptons. Any activity in the universe would be very limited at this point and what did occur would take truly epic time scales.

The concordance cosmology, the theoretical models, and the measured parameters implicitly assume that the end of the universe is cold, dark, and lonely. The universe ending as cold void in which life can no longer be sustained is sometimes known as the Big Chill. At this point there is only speculation, perhaps it is philosophical. The universe may expand again in a secondary inflationary epoch or the vacuum may decay into an even lower energy state. Actually, there are other possible scenarios such as the Big Rip in which dark energy pulls apart the fabric of space through some exponentially increasing expansion. Revisionist history is the best kind of history, so when talking about the future history revisions are always welcome. There may already be information about universe which has been erased that would change our expectations. One example of the universe erasing information is if the radius of curvature of the universe is much greater than the horizon distance then observing this curvature would be like trying perceive the curvature of the earth just by looking at the horizon so as the universe, or earth, expanded observing curvature could more difficult. Paradoxically, conceding that there is information about the universe which has been erased which would indicate an ultimate fate other than the one outlined here also supports the argument that the ultimate fate of the universe is an extremely high entropy state.

Conceding that the universe may not be infinite or that the end is simply cold and lonely is very difficult for some. This theme was explored in Issac Asimov's story The Last Question in my previous post. In this story man ponders how the heat death of the universe can be avoided. Man asks the greatest computer created how the second law of thermodynamics can be reversed. [spoiler alert] After hundreds of billions of years the computer still cannot answer the humans. Ultimately all of humanities mental facilities from the trillions of humans spread throughout the universe merge their minds with this ultimate computer to from a singular unified mental process. The question is asked again and there is still no answer. Time goes on until space and time cease to exist, however the ultimate mind continues to ponder the question in hyperspace and eventually finds an answer. There is no one or no thing left to report the answer to so the mind decides to show the answer by demonstrating the reversal of entropy. The mind spends another eternity determining how to do this and writing a careful program to execute. Upon execution of the program the mind reverses entropy and thus creates the universe anew.

The Last Question

The last question was asked for the first time, half in jest, on May 21, 2061, at a time when humanity first stepped into the light. The question came about as a result of a five dollar bet over highballs, and it happened this way:

Alexander Adell and Bertram Lupov were two of the faithful attendants of Multivac. As well as any human beings could, they knew what lay behind the cold, clicking, flashing face -- miles and miles of face -- of that giant computer. They had at least a vague notion of the general plan of relays and circuits that had long since grown past the point where any single human could possibly have a firm grasp of the whole.

Continue reading The Last Question by Isaac Asimov or hear it spoken below.

It is interesting to note that different versions of this story I have encountered state the the sun will burn for ten billion years or 20 billion years. The written story above says twenty while the spoken story says ten. I don't know what the original version said (does anyone out there?). Perhaps this reflects our changing understanding of our sun which suggests that ten billion years is more appropriate.