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Physics is full of concepts that are counterintuitive. Inertia is an early example of one such concept. But ideas are adopted based on their explanatory power,

Physics is full of concepts that are counterintuitive. Inertia is an early example of one such concept. But ideas are adopted based on their explanatory power, and one way you get places is with an ethos called 'shut up and calculate'. I.e., don't think too hard about the 'counterintuitive' nature of what the theories predict, crunch the numbers and figure out what the predictions are and leave the implications to the philosophers. Once you accept that the speed of light is constant in all reference frames, relativity falls out from that. That in itself is a bit hard to accept, though, which was why it was some number of years between the Michelson-Morley experiment in 1887 and Einstein's paper on SR in 1905. GR basically also comes from 'shut up and calculate' after accepting the principles behind SR but adapting them to non-inertial reference frames (and also the insight behind gravity being a fictitious force), but the mathematics is much more complicated than SR, which I assume is why it took Einstein over a decade to work it out.

CRConrad 5y ago
> Physics is full of concepts that are counterintuitive. Inertia is an early example of one such concept. Huh?!? Try to start a car by pushing it -- or stopping it, even on flat ground, after it's gathered momentum rolling down some slope -- a few times, and inertia becomes utterly intuitive. I'd imagine that worked for medieval oxcarts, too. Or for moving blocks of stone for the pyramids, or Stonehenge.
- mannerheim 5y ago
  Perhaps, but prior to Galileo (or perhaps Avicenna?), Aristotelian physics dominated and motion was explained by 'impetus' (this didn't originate from Aristotle, but instead came long after him). Aristotle distinguished between 'natural' motion, which is the motion of falling objects and 'violent' or 'unnatural' motion, which is caused by some agent (a human throwing a stone, for instance). In the theory of impetus, the agent imbues an object with some impetus, and this impetus is only ever temporary, the object stopping once its impetus is exhausted. Today, sure, we know that friction is a force that acts against the momentum of a moving object, but these were alien concepts a thousand years ago.
drran 5y ago
Hey, hey, hey, hold the horses. The very idea of using the 1887 experiment from Stone Age to defend GR seems ridiculous. I understand why you are doing that: there are no modern experiments, which you can use to defend your point, but still. Moreover, interpretation of Michelson-Morley experiment as «it proves that physical vacuum does not exist» is frivolous. Let me quote Wikipedia: > The Michelson–Morley experiment of 1887 had suggested that the hypothetical luminiferous aether, if it existed, was completely dragged by the Earth. To test this hypothesis, Oliver Lodge in 1897 proposed that a giant ring interferometer be constructed to measure the rotation of the Earth; a similar suggestion was made by Albert Abraham Michelson in 1904. > the first interferometry experiment aimed at observing the correlation of angular velocity and phase-shift was performed by the French scientist Georges Sagnac in 1913. Its purpose was to detect "the effect of the relative motion of the ether". > In 1926, an ambitious ring interferometry experiment was set up by Albert Michelson and Henry Gale. The aim was to find out whether the rotation of the Earth has an effect on the propagation of light in the vicinity of the Earth. The Michelson–Gale–Pearson experiment was a very large ring interferometer, (a perimeter of 1.9 kilometer), large enough to detect the angular velocity of the Earth. The outcome of the experiment was that the angular velocity of the Earth as measured by astronomy was confirmed to within measuring accuracy. The ring interferometer of the Michelson–Gale experiment was not calibrated by comparison with an outside reference (which was not possible, because the setup was fixed to the Earth). From its design it could be deduced where the central interference fringe ought to be if there would be zero shift. The measured shift was 230 parts in 1000, with an accuracy of 5 parts in 1000. The predicted shift was 237 parts in 1000. So, Michelson-Morley experiment confirmed that physical vacuum is dragged with Earth, and then Michelson–Gale–Pearson experiment confirmed that it is not completely dragged by Earth. It far from «physical vacuum doesn't exist» mantra from «shutup and calculate» guys. In this century, * the existence of Higgs boson, which gives mass, and Higgs field, which exists at every point of our Universe, was proved in 2012; * the existence of gravitational waves in physical vacuum is proved by LIGO/Virgo interferometers. Thus, today we have Higgs field, which is presented at every point, which can be used as 0 point, but we cannot detect it. However, we can use CMB (light from distant galaxies with red shift z=1000) as 0 point. IMHO, relativity is not necessary at this point.
- mannerheim 5y ago
jdrc 5y ago
In retrospect, 100% of science looks obvious. This is the nature of discovery. It's a whole lot different from the other side.

CRConrad 5y ago

> Physics is full of concepts that are counterintuitive. Inertia is an early example of one such concept. Huh?!? Try to start a car by pushing it -- or stopping it, even on flat ground, after it's gathered momentum rolling down some slope -- a few times, and inertia becomes utterly intuitive. I'd imagine that worked for medieval oxcarts, too. Or for moving blocks of stone for the pyramids, or Stonehenge.

mannerheim 5y ago
Perhaps, but prior to Galileo (or perhaps Avicenna?), Aristotelian physics dominated and motion was explained by 'impetus' (this didn't originate from Aristotle, but instead came long after him). Aristotle distinguished between 'natural' motion, which is the motion of falling objects and 'violent' or 'unnatural' motion, which is caused by some agent (a human throwing a stone, for instance). In the theory of impetus, the agent imbues an object with some impetus, and this impetus is only ever temporary, the object stopping once its impetus is exhausted. Today, sure, we know that friction is a force that acts against the momentum of a moving object, but these were alien concepts a thousand years ago.

drran 5y ago

Hey, hey, hey, hold the horses. The very idea of using the 1887 experiment from Stone Age to defend GR seems ridiculous. I understand why you are doing that: there are no modern experiments, which you can use to defend your point, but still. Moreover, interpretation of Michelson-Morley experiment as «it proves that physical vacuum does not exist» is frivolous. Let me quote Wikipedia: > The Michelson–Morley experiment of 1887 had suggested that the hypothetical luminiferous aether, if it existed, was completely dragged by the Earth. To test this hypothesis, Oliver Lodge in 1897 proposed that a giant ring interferometer be constructed to measure the rotation of the Earth; a similar suggestion was made by Albert Abraham Michelson in 1904. > the first interferometry experiment aimed at observing the correlation of angular velocity and phase-shift was performed by the French scientist Georges Sagnac in 1913. Its purpose was to detect "the effect of the relative motion of the ether". > In 1926, an ambitious ring interferometry experiment was set up by Albert Michelson and Henry Gale. The aim was to find out whether the rotation of the Earth has an effect on the propagation of light in the vicinity of the Earth. The Michelson–Gale–Pearson experiment was a very large ring interferometer, (a perimeter of 1.9 kilometer), large enough to detect the angular velocity of the Earth. The outcome of the experiment was that the angular velocity of the Earth as measured by astronomy was confirmed to within measuring accuracy. The ring interferometer of the Michelson–Gale experiment was not calibrated by comparison with an outside reference (which was not possible, because the setup was fixed to the Earth). From its design it could be deduced where the central interference fringe ought to be if there would be zero shift. The measured shift was 230 parts in 1000, with an accuracy of 5 parts in 1000. The predicted shift was 237 parts in 1000. So, Michelson-Morley experiment confirmed that physical vacuum is dragged with Earth, and then Michelson–Gale–Pearson experiment confirmed that it is not completely dragged by Earth. It far from «physical vacuum doesn't exist» mantra from «shutup and calculate» guys. In this century, * the existence of Higgs boson, which gives mass, and Higgs field, which exists at every point of our Universe, was proved in 2012; * the existence of gravitational waves in physical vacuum is proved by LIGO/Virgo interferometers. Thus, today we have Higgs field, which is presented at every point, which can be used as 0 point, but we cannot detect it. However, we can use CMB (light from distant galaxies with red shift z=1000) as 0 point. IMHO, relativity is not necessary at this point.

mannerheim 5y ago

jdrc 5y ago

In retrospect, 100% of science looks obvious. This is the nature of discovery. It's a whole lot different from the other side.