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democura

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- TL;DR Summary
- What can we objectively measure? It seems as if everything we measure is either mass or energy. Are there examples of when we measure something differently?

I am interested in finding out what we can objectively measure. How to define what we can measure directly, without (human) models getting involved, as in model-dependent realism as described by Hawking and Mlodinow? It seems as if everything we measure is either mass or energy (or spin?).

Time for example, cannot be measured without being relative or even subjective. How is time measured? We do not measure time directly. We measure the intervals between two events, for example between the emitting of a photon and the measurement of the returning photon. These can for example be measured with an atomic clock. Atomic clocks produce electromagnetic radiation with a precise frequency that causes atoms in the clock to jump from one energy level to another. What we in fact measure is energy.

LIGO, the Laser Interferometer Gravitational-Wave Observatory, explained in a somewhat simplistic way, can measure gravitational waves by measuring the distance two different light waves have traveled. The interferometer has two ‘arms’ which measure the time and distance of a laser (light) travelling from one point to another. Both arms are placed in an angle of 90 degrees. When a gravitational wave hits the interferometer, one of the arms will be slightly elongated and the other one slightly contracted because the gravitational wave will distort space. This will lead to a different travel time for each light wave. Again, we can only (for now) measure gravitational waves by using mass and energy, lasers and sensors in this case.

Time for example, cannot be measured without being relative or even subjective. How is time measured? We do not measure time directly. We measure the intervals between two events, for example between the emitting of a photon and the measurement of the returning photon. These can for example be measured with an atomic clock. Atomic clocks produce electromagnetic radiation with a precise frequency that causes atoms in the clock to jump from one energy level to another. What we in fact measure is energy.

LIGO, the Laser Interferometer Gravitational-Wave Observatory, explained in a somewhat simplistic way, can measure gravitational waves by measuring the distance two different light waves have traveled. The interferometer has two ‘arms’ which measure the time and distance of a laser (light) travelling from one point to another. Both arms are placed in an angle of 90 degrees. When a gravitational wave hits the interferometer, one of the arms will be slightly elongated and the other one slightly contracted because the gravitational wave will distort space. This will lead to a different travel time for each light wave. Again, we can only (for now) measure gravitational waves by using mass and energy, lasers and sensors in this case.