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arXiv2016

On The Relativity of Redshifts: Does Space Really "Expand"?

In classes on cosmology, students are often told that photons stretch as space expands, but just how physical is this picture? Does space really expand? In this article, we explore the notion of the redshift of light with Einstein's general theory of relativity, showing that the core underpinning principles reveal that redshifts are both simpler and more complex than you might naively think. This has significant implications for the observed redshifting of photons as they travel across the universe, often refereed to as the cosmological redshift, and for the idea of expanding space.

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arXiv2016

The Story of the Neutrino

This is an elementary review of the history and physics of neutrinos. The story of the discovery of neutrino mass through neutrino oscillations is described in some detail. Experiments on solar neutrinos and atmospheric neutrinos played an important part. Recent advances are summarized and future developments are indicated.

physics.pop-ph↗

arXiv2017

The eras of radiation, matter, and dark energy: new information from the Planck Collaboration

Data released by the Planck Collaboration in 2015 imply new dates for the era of radiation, the era of matter, and the era of dark energy. The era of radiation ended, and the era of matter began, when the density of radiation dropped below that of matter. This happened 50,953 \pm 2236 years after the time of infinite redshift when the ratio a(t)/a_0 of scale factors was (2.9332 \pm 0.0711) x 10^{-4}. The era of matter ended, and the era of dark energy began, when the density of matter dropped below that of dark energy (assumed constant). This happened 10.1928 \pm 0.0375 Gyr after the time of infinite redshift when the scale-factor ratio was 0.7646 \pm 0.0168. The era of dark energy started 3.606 billion years ago. In this pedagogical paper, five figures trace the evolution of the densities of radiation and matter, the scale factor, and the redshift through the eras of radiation, matter, and dark energy.

physics.pop-ph↗

arXiv2017

How to run 100 meters ?

The aim of this paper is to bring a mathematical justification to the optimal way of organizing one's effort when running. It is well known from physiologists that all running exercises of duration less than 3mn are run with a strong initial acceleration and a decelerating end; on the contrary, long races are run with a final sprint. This can be explained using a mathematical model describing the evolution of the velocity, the anaerobic energy, and the propulsive force: a system of ordinary differential equations, based on Newton's second law and energy conservation, is coupled to the condition of optimizing the time to run a fixed distance. We show that the monotony of the velocity curve vs time is the opposite of that of the oxygen uptake ($\dot{VO2}$) vs time. Since the oxygen uptake is monotone increasing for a short run, we prove that the velocity is exponentially increasing to its maximum and then decreasing. For longer races, the oxygen uptake has an increasing start and a decreasing end and this accounts for the change of velocity profiles. Numerical simulations are compared to timesplits from real races in world championships for 100m, 400m and 800m and the curves match quite well.

physics.pop-ph↗

arXiv2016

Life, Intelligence and Multiverse

Hypothetical existence of other universes gives an opportunity not only to extend the scope of physics, but the scope of biology, SETI, and METI as well. Some steps of the development of alien life concept shall be briefly summarized, then the multiverse proposal shall be used as a framework of interpretation to introduce an extended taxonomy of possible or at least imaginable types of life and intelligence based on either different biochemistry or physics. Some consequences shall be presented about SETI and METI in connection with both multiverse hypothesis and anthropic principle.

physics.hist-ph↗

arXiv2016

"What's (the) Matter?", A Show on Elementary Particle Physics with 28 Demonstration Experiments

We present the screenplay of a physics show on particle physics, by the Physikshow of Bonn University. The show is addressed at non-physicists aged 14+ and communicates basic concepts of elementary particle physics including the discovery of the Higgs boson in an entertaining fashion. It is also demonstrates a successful outreach activity heavily relying on the university physics students. This paper is addressed at anybody interested in particle physics and/or show physics. This paper is also addressed at fellow physicists working in outreach, maybe the experiments and our choice of simple explanations will be helpful. Furthermore, we are very interested in related activities elsewhere, in particular also demonstration experiments relevant to particle physics, as often little of this work is published. Our show involves 28 live demonstration experiments. These are presented in an extensive appendix, including photos and technical details. The show is set up as a quest, where 2 students from Bonn with the aid of a caretaker travel back in time to understand the fundamental nature of matter. They visit Rutherford and Geiger in Manchester around 1911, who recount their famous experiment on the nucleus and show how particle detectors work. They travel forward in time to meet Lawrence at Berkeley around 1950, teaching them about the how and why of accelerators. Next, they visit Wu at DESY, Hamburg, around 1980, who explains the strong force. They end up in the LHC tunnel at CERN, Geneva, Switzerland in 2012. Two experimentalists tell them about colliders and our heroes watch live as the Higgs boson is produced and decays. The show was presented in English at Oxford University and University College London, as well as Padua University and ICTP Trieste. It was 1st performed in German at the Deutsche Museum, Bonn (5/'14). The show has eleven speaking parts and involves in total 20 people.

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arXiv2016

The Peaks of Eternal Light: a Near-term Property Issue on the Moon

The Outer Space Treaty makes it clear that the Moon is the province of all mankind, with the latter ordinarily understood to exclude state or private appropriation of any portion of its surface. However, there are indeterminacies in the Treaty and in space law generally over the issue of appropriation. These indeterminacies might permit a close approximation to a property claim or some manner of quasi-property. The recently revealed highly inhomogeneous distribution of lunar resources changes the context of these issues. We illustrate this altered situation by considering the Peaks of Eternal Light. They occupy about one square kilometer of the lunar surface. We consider a thought experiment in which a Solar telescope is placed on one of the Peaks of Eternal Light at the lunar South pole for scientific research. Its operation would require nondisturbance, and hence that the Peak remain unvisited by others, effectively establishing a claim of protective exclusion and de facto appropriation. Such a telescope would be relatively easy to emplace with todays technology and so poses a near-term property issue on the Moon. While effective appropriation of a Peak might proceed without raising some of the familiar problems associated with commercial development (especially lunar mining), the possibility of such appropriation nonetheless raises some significant issues concerning justice and the safeguarding of scientific practice on the lunar surface. We consider this issue from scientific, technical, ethical and policy viewpoints.

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arXiv2017

Galileo (1564-1642) and Kepler (1571-1630): the modern scientist and the mystic

The art of advertising one's scientific achievements, of which Galileo was an early master, is a trademark of successful modern science. Dedicated believers and mystics of science, such as Kepler, are less popular. Yet, an alleged rigorous rationalist like Wolfgang Pauli found in his later troubled life a kinship to Kepler's "archetypal ideas".

physics.hist-ph↗

arXiv2016

Bifurcation Adds Flavor to Basketball

We report an emergence of bifurcation in basketball, a single-particle system governed by Newtonian mechanics. When shooting the basketball, the obvious control parameters are the launch speed and the launch angle. We propose to use the three-dimensional velocity phase-space volume associated with the given launch parameters to quantify the difficulty of the shooting. The optimal launch angle that maximizes the associated phase-space volume undergoes a bifurcation as the launch speed is increased, if the shooter is farther than a critical distance away from the hoop. Thus, the bifurcation makes it very important to control the launch speed accurately. If the air resistance is removed, the bifurcation disappears and the phase-space volume distribution becomes dispersionless and shrinks in magnitude.

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arXiv2016

The golden age of Calcutta physics: Difficulties in reconstructing the history

Classes started in the newly established Physics Department of Calcutta University Science College in 1916. Raman, Bose and Saha were three young members of the small physics faculty consisting of barely half a dozen faculty members. Within about one decade, three extraordinary discoveries came from these young men---Saha ionization equation in 1920, Bose statistics in 1924, Raman effect in 1928. However, fortunes of Calcutta University quickly got intertwined with India's freedom struggle led by Mahatma Gandhi exactly at the same time and the physics group got tragically disrupted. Indian physics never succeeded in reaching that height again. This paper discusses the difficulties in reconstructing a critical history of this Calcutta school of physics during the very short epoch of unmatched brilliance.

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arXiv2016

Dreidel Fairness Study

Are dreidels fair? In other words, does the average dreidel have an equal chance of turning up any one of its four sides? To explore this hypothesis, three different dreidels were each spun hundreds of times with the number of occurrences of each side recorded. It was found that all three dreidels tested -- a cheap plastic dreidel, an old wooden dreidel, and a dreidel that came embossed with a picture of Santa Claus -- were not fair. Statistically, for each dreidel, some sides came up significantly more often than others. Although an unfair dreidel does not necessarily make the game itself unfair, it is conjectured that hundreds of pounds of chocolate have been distributed during Chanukah under false pretenses.

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arXiv2016

Quark Wars - a particle physics outreach game in the age of Star Wars

Quark Wars is an all-new, adventure style game. We recommended playing it outdoors. Quark Wars is modeled upon the outdoor game called Hungarian Number War, with notable influence from Star Wars, the American epic space saga. The players form two opposing teams. Both teams elect their own leader. The team members and their leaders wear particle war bonnets on their foreheads. These headdresses consist of three or four cards indicating combinations of elementary particles. The two teams compete by identifying (reading out loudly) the elementary particle cards on the foreheads of their adversaries. Players are allowed to use the terrain to cover their particle identity on their foreheads and may try to hide, run, or band together in a group to win. Quark Wars was tested at a Summer Camp of Berze Science Club in Hungary. Students loved playing Quark Wars, as this game resulted in lots of hilarity and action. In addition, Quark Wars also solidified particle terminology and made the concept of particle identification and discovery more tangible to secondary/middle school students.

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arXiv2017

Berezinskii-Kosterlitz-Thouless Transition and the Haldane Conjecture: Highlights of the Physics Nobel Prize 2016

The 2016 Physics Nobel Prize honors a variety of discoveries related to topological phases and phase transitions. Here we sketch two exciting facets: the groundbreaking works by John Kosterlitz and David Thouless on phase transitions of infinite order, and by Duncan Haldane on the energy gaps in quantum spin chains. These insights came as surprises in the 1970s and 1980s, respectively, and they have both initiated new fields of research in theoretical and experimental physics.

physics.pop-ph↗

arXiv2022

Coin Toss Modeling

The torque-free motion of rigid body in gravitational field is analyzed. The coin lands on a soft surface (such as the palm of the hand) that allows no bouncing. The model assumes the coin as a rigid body with constant angular momentum vector in the body frame, and no air resistance. Unbiased probabilities of heads and tails are obtained for various initial conditions accessible to a usual person.

physics.pop-ph↗

arXiv2017

Reply to Burridge & Linden: Hot water may freeze sooner than cold

In a recent paper in Scientific Reports, Burridge \& Linden misinterpret the Mpemba effect as a statement about the rate of cooling of liquid water, when it is in fact a statement about the rate of freezing of water. Debunking an obviously absurd claim about cooling, they miss the significant effect, its only quantitative experimental study and a theoretical argument that explains the effect and predicts that it occurs only for "hard" water (water with significant dissolved Mg and Ca bicarbonates). This prediction remains to be tested.

physics.pop-ph↗

arXiv2017

Does the Universe have a Hard Drive?

We discuss an apparent information paradox that arises in a materialist's description of the Universe if we assume that the Universe is 100% quantum. We discuss possible ways out of the paradox, including that Laws of Nature are not purely deterministic, or that gravity is classical. Our observation of the paradox stems from an interdisciplinary thought process whereby the Universe can be viewed as a "quantum computer". Our presentation is intentionally nontechnical to make it accessible to as wide a readership base as possible.

physics.pop-ph↗

arXiv2017

Gravitational waves 100 years after Einstein

The LIGO-VIRGO collaboration has detected directly on Earth the gravitational wave signals generated by the collision and the merger of two massive black holes at astronomical distance. This major discovery opens up the way to Gravitational Astronomy, which should revolutionize our comprehension of the structure of the Universe at large scales, with notably the mechanisms of formation of black holes and their role in the evolution of the Universe, the likely emergence of a multi-messenger astronomy joint with electromagnetic radiation, and a better appraisal of the status of general relativity with respect to other fundamental interactions. The theoretical and numerical works on the two-body problem in general relativity play a very important role when deciphering and interpreting the gravitational wave signals.

physics.pop-ph↗

arXiv2017

Qbe: Quark Matter on Rubik's Cube

Quarks can be represented on the faces of the 3x3 Rubik's cube with the help of a symbolic representation of quarks and anti-quarks, that was delevoped originally for a deck of elementary particle cards, called Quark Matter Card Game. Cubing the cards leads to a model of the nearly perfect fluid of Quark Matter on Rubik's cube, or Qbe, which can be utilized to provide hands-on experience with the high entropy density, overall color neutrality and net baryon free, nearly perfect fluid nature of Quark Matter.

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