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27. Natural Reality / B. Modern Physics / 4. Standard Model / d. Mass

[quantity of matter in a thing]

4 ideas
Mass is a measure of energy content [Einstein]
     Full Idea: The mass of a body is the measure of its energy content.
     From: Albert Einstein (works [1915]), quoted by Peter Watson - Convergence 04 'Intro'
     A reaction: If I knew what energy was, this would be very illuminating. This idea is e=mc^2 in words. We now have the Higgs field to consider when trying to understand mass.
In Newton mass is conserved, but in Einstein it can convert into energy [Bird]
     Full Idea: According to Newton mass is conserved, while in Einstein's theory mass is not conserved but can be converted into and from energy.
     From: Alexander Bird (Philosophy of Science [1998])
     A reaction: Perhaps this is the most fundamental difference between the theories. It certainly suggests that 'mass' was a conventional concept rather than a natural one. Maybe the relative notion of 'weight' is more natural than 'mass'.
The mass of protons and neutrinos is mostly binding energy, not the quarks [New Sci.]
     Full Idea: Most of a proton's or neutrino's mass is contained in the interaction energies of a 'sea' of quarks, antiquarks and gluons that bind them. ...You might feel solid, but in fact you're 99 per cent binding energy.
     From: New Scientist writers (Why the Universe Exists [2017], 04)
     A reaction: This is because energy is equivalent to mass (although gluons are said to have energy but no mass - puzzled by that). This is a fact which needs a bit of time to digest. Once you've grasped we are full of space, you still have understood it.
Gravitional mass turns out to be the same as inertial mass [New Sci.]
     Full Idea: There are two types of mass: gravitational mass quantifies how strongly an object feels gravity, while inertial mass quantifies an object's resistance to acceleration. There proven equality is at the heart of General Relativity.
     From: New Scientist writers (Why the Universe Exists [2017], 05)
     A reaction: It had never occurred to me that these two values might come apart. Doesn't their identical values demonstrate that they are in fact the same thing? Sounds like Hesperus/Phosphorus to me. The book calls it 'mysterious'.