The twin paradox: the role of acceleration

J. Gamboa, F. Mendez, M. B. Paranjape, Benoit Sirois
The twin paradox, which evokes from the the idea that two twins may age differently because of their relative motion, has been studied and explained ever since it was first described in 1906, the year after special relativity was invented. The question can be asked: “Is there anything more to say?” It seems evident that acceleration has a role to play, however this role has largely been brushed aside since it is not required in calculating, in a preferred reference frame, the relative age difference of the twins. Indeed, if one tries to calculate the age difference from the point of the view of the twin that undergoes the acceleration, then the role of the acceleration is crucial and cannot be dismissed. In the resolution of the twin paradox, the role of the acceleration has been denigrated to the extent that it has been treated as a red-herring. This is a mistake and shows a clear misunderstanding of the twin paradox.
Read more at https://arxiv.org/pdf/1807.02148.pdf

The Physics of baking good Pizza

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Heat transfer mechanisms in the pizza oven

Andrey Varlamov, Andreas Glatz, Sergio Grasso
Physical principles are involved in almost any aspect of cooking. Here we analyze the specific process of baking pizzas, deriving in simple terms the baking times for two different situations: For a brick oven in a pizzeria and a modern metallic oven at home. Our study is based on basic thermodynamic principles relevant to the cooking process and is accessible to undergraduate students. We start with a historical overview of the development and art of pizza baking, illustrate the underlying physics by some simple common examples, and then apply them in detail to the example of baking pizza.
Read more at https://arxiv.org/ftp/arxiv/papers/1806/1806.08790.pdf

Longest Straight Line Paths on Water or Land on the Earth

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Longest Sailable Straight Line Path on Earth


Rohan Chabukswar, Kushal Mukherjee
There has been some interest recently in determining the longest distance one can sail for on the earth without hitting land, as well as in the converse problem of determining the longest distance one could drive for on the earth without encountering a major body of water. In its basic form, this is an optimisation problem, rendered chaotic by the presence of islands and lakes, and indeed the fractal nature of the coasts. In this paper we present a methodology for calculating the two paths using the branch-and-bound algorithm.
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Longest Drivable Straight Line Path on Earth

Read more at https://arxiv.org/pdf/1804.07389.pdf

Aside

Temporal relationalism

Lee Smolin
Because of the non-locality of quantum entanglement, realist approaches to completing quantum mechanics have implications for our conception of space. Quantum gravity also is expected to predict phenomena in which the locality of classical spacetime is modified or disordered. It is then possible that the right quantum theory of gravity will also be a completion of quantum mechanics in which the foundational puzzles in both are addressed together. I review here the results of a program, developed with Roberto Mangabeira Unger, Marina Cortes and other collaborators, which aims to do just that. The results so far include energetic causal set models, time asymmetric extensions of general relativity and relational hidden variables theories, including real ensemble approaches to quantum mechanics. These models share two assumptions: that physics is relational and that time and causality are fundamental.
Read more at https://arxiv.org/pdf/1805.12468.pdf