Wednesday, December 7, 2016

Review of "Seven Brief Lessons on Physics" by Carlo Rovelli


These seven brief lessons about physics are interesting, enlightening, and (more or less) accessible to non-scientists. The author, Carlo Rovelli, is a theoretical physicist with great enthusiasm for his subject matter.

The lessons (which I'm greatly simplifying) include:

Special Theory of Relativity: The faster you move, the slower time passes. This would be really obvious if you could travel at the speed of light.
General Theory of Relativity: Space is not empty, but composed of particles of some kind. The sun bends space around itself, and the planets circle around the sun because they follow the curve of space (like marbles that roll around a funnel). This explains the 'force of gravity' that prevents the planets from flying off into the galaxy.

Quantum Mechanics: The energy of a field is distributed in 'quanta', or packets of energy, like electrons in an electrical field. But quanta only exist when they're interacting with something else - so they bleep in an out of existence. Moreover, quanta move randomly so we can't know where they'll manifest themselves. (If you can't wrap your mind around this don't feel bad. Albert Einstein couldn't either. LOL)

The Architecture of the Cosmos: Our sun is one star among billions of stars in the galaxy.....and there are billions of galaxies.....and so on. There may even be more than one universe, but we don't know.

Particles: The universe is teeming with particles called electrons, quarks, gluons, photons, neutrinos, and Higgs bosons. Rovelli explains that these particles are 'like bricks in a Lego set' that make up the material things surrounding us. Moreover, 'the nature of these particles and the way they move is described by quantum mehanics' they're always winking in an out of being. All the particles, fields, and forces in the universe are summed up in 'The Standard Model of Particle Physics' which no one understands. Ha ha ha.

Quantum Gravity: Unfortunately the theories of general relativity - where the universe is a continous curved space, and quantum mechanics - where the universe is composed of particles that bleep in and out of existence, contradict each other. But both theories work well. So physicists are trying to merge the ideas in a field of study called 'loop quantum gravity.'

One combined theory suggests that space is not continuous but made up of infinitesimally small 'grains of space' called loops.....connected somewhat like a chain link fence. This theory has repercussions that mess with the reality of time - so it needs a lot more of work.

Probability, Time, and The Heat of Black Holes: The notion of 'time' is elusive and has been the subject of much debate among physicists. Rovelli points out, though, that heat distinguishes the past from the future. As time goes by, heat passes from things that are hotter to things that are colder (for example, a teaspoon heats up in hot tea). The science of heat is called thermodynamics.

We don't know what happens to a gravitational field when it heats up, but a clue might be found in a black hole - a collapsed star with a gravitational field so strong that nothing (not even light) can escape. Black holes are hot - in essence hot 'spots' of space-time. Thus they combine quantum mechanics, general relativity, and thermodynamics. Eventually, scientists might be able to use black holes to reveal the true nature of time.

Ourselves: If humans are composed of ephemeral particles, the same stuff as the rest of the universe, where do we get our sense of ourselves......of being conscious and making decisions. Scientists studying the brain are trying to shed light on this.

I liked the book - which is short and sweet - and recommend it to readers interested in the subject.

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