## Archive for the ‘**PHYSICS**’ Category

## Applying physics to mathematics

**by Tadashi Tokieda**

abstract : Humans tend to be better at physics than at mathematics. When an apple falls from a tree, there are more people who can catch it—we know physically how the apple moves—than people who can compute its trajectory from a differential equation. Applying physical ideas to discover and establish mathematical results is therefore natural, even if it has seldom been tried in the history of science. (The exceptions include Archimedes, some old Russian sources, a recent book by Mark Levi, as well as my articles and lectures.) This TMC Distinguished Lecture presents a diversity of examples, and tries to make them easy for imaginative beginners and difficult for seasoned researchers.

## Chirality Through Classical Physics

**Chris L. Lin**

Chirality, or handedness, is a topic that is common in biology and chemistry, yet is rarely discussed in physics courses. We provide a way of introducing the topic in classical physics, and demonstrate the merits of its inclusion – such as a simple way to visually introduce the concept of symmetries in physical law – along with giving some simple proofs using only basic matrix operations, thereby avoiding the full formalism of the three-dimensional point group.

Read also https://arxiv.org/pdf/2004.08236.pdf

## Memory and entropy

**Carlo Rovelli**

I study the physical nature of traces (or memories). Surprisingly, (i) systems separation with (ii) temperature differences and (iii) long thermalization times, are sufficient conditions to produce macroscopic traces. Traces of the past are ubiquitous because these conditions are largely satisfied in our universe. I quantify these thermodynamical conditions for memory and derive an expression for the maximum amount of information stored in such memories, as a function of the relevant thermodynamical parameters. This mechanism transforms low entropy into available information.

Read more at https://arxiv.org/pdf/2003.06687.pdf

## Graphic Talk about the Universe: Clifford V. Johnson

In his public lecture webcast at Perimeter on February 7, Clifford V. Johnson discussed the process of turning complex scientific topics into compelling visual narratives.

## Effects of exoplanetary gravity on human locomotor ability

**Nikola Poljak, Dora Klindzic, Mateo Kruljac**

At some point in the future, if mankind hopes to settle planets outside the Solar System, it will be crucial to determine the range of planetary conditions under which human beings could survive and function. In this article, we apply physical considerations to future exoplanetary biology to determine the limitations which gravity imposes on several systems governing the human body. Initially, we examine the ultimate limits at which the human skeleton breaks and muscles become unable to lift the body from the ground. We also produce a new model for the energetic expenditure of walking, by modelling the leg as an inverted pendulum. Both approaches conclude that, with rigorous training, humans could perform normal locomotion at gravity no higher than 4 g_{Earth}.

Read more at https://arxiv.org/pdf/1808.07417.pdf

## Upper limit on the Stiffness of space-time

Adrian Melissinos

From the recently observed propagation of gravitational waves through space-time an upper limit can be deduced for the stiffness of space-time through which the gravitational wave propagates. The upper limit is extremely weak, implying that the stiffness of space-time is at least 14 orders of magnitude weaker than that of jello.

Read more at https://arxiv.org/pdf/1806.01133.pdf