4 ms·
I feel you've done little but directly translate the LIGO experiment into Flatlandian physics. That doesn't answer the question. Use a sheet of paper as your F
by delinka 11y ago
I feel you've done little but directly translate the LIGO experiment into Flatlandian physics. That doesn't answer the question.
Use a sheet of paper as your Flatland. Draw two points, measure the distance. Crinkle up the paper. There's still the same 'distance' of paper between the two points. Should the points be able to travel, they have to traverse the same number of paper molecules whether the paper is crinkled or not. No one living in this Flatland can measure the crinkles in this space because they live inside this space. They would need to step outside their own space with some ability to measure variations in a third dimension.
If the physics of a universe necessitates movement from one point to the next (let's suppose these points are Planck length apart, call them 'Planck-points'), if particles must be translated from Planck-point to Planck-point and can't skip anything in between, how are we to ever measure that Planck length expanded or contracted? Surely if it "takes longer" to traverse an expanded Planck length, then it hasn't expanded, but there now exists more space - more Planck-points.
If gravity wells stretch and contract _matter_ (rather than space), then this fits my mental model. If they actually stretch _space_, within which matter exist and along which matter traverses, I struggle to see how we could ever detect space deformations without stepping outside our own space.
- T-A 11y ago> Use a sheet of paper as your Flatland. Draw two points, measure the distance. Crinkle up the paper. There's still the same 'distance' of paper between the two points. Because the paper is not elastic. Spacetime is; it stretches. So a better analogy would be the rubber sheet with masses rolling around on it, and deforming it, which is often invoked in popular introductions to spacetime curvature. Like all analogies, it has its limitations, but it does capture the essence of the classic Wheeler quote: "Mass tells space-time how to curve, and space-time tells mass how to move." > If gravity wells stretch and contract _matter_ (rather than space), then this fits my mental model. Gravity stretches and contracts space AND matter, the latter to the extent that it can overcome the chemical bonds (and other forces) trying to keep matter together (gravity is weak, so that takes a lot of mass). We see the stretching of matter all the time as tides. Moons torn apart by it when they get too close to their planets (the Roche limit) is a more dramatic example. Spagettification of matter falling into a black hole an even more dramatic one. You can think of gravitational waves as an oscillating, self-sustaining tide traveling at the speed of light. By the way, there is a thread of thought which takes the analogy of spacetime with an elastic solid quite seriously: http://arxiv.org/abs/gr-qc/0408051 http://arxiv.org/abs/gr-qc/0408051