3 ms·

[paraphrasing] "there's a lot of confusion about if space stretches, doesn't that also stretch the light being mesured... ... notice that I didn't say whether

by platz 8y ago

[paraphrasing] "there's a lot of confusion about if space stretches, doesn't that also stretch the light being mesured... ... notice that I didn't say whether space stretches or that time slows down (in response to a passing wave) - since we don't know how exactly space and time are mixed up, we just record that it took longer for the light to come back, but we don't say whether it was a difference in time or a difference in space that cause the slowdown" The Technical Challenges of Measuring Gravitational Waves - Rana Adhikari of LIGO https://www.youtube.com/watch?v=1D2j8nTjOZ4 https://www.youtube.com/watch?v=1D2j8nTjOZ4

acqq 8y ago
This article tries to explain: https://www.forbes.com/sites/startswithabang/2018/09/15/ask-ethan-if-light-contracts-and-expands-with-space-how-do-we-detect-gravitational-waves/ https://www.forbes.com/sites/startswithabang/2018/09/15/ask-... "Ask Ethan: If Light Contracts And Expands With Space, How Do We Detect Gravitational Waves?" It also links to the FAQ at LIGO: https://www.ligo.caltech.edu/page/faq https://www.ligo.caltech.edu/page/faq which for this question ends with: "This varying pattern of misaligned laser beams, observed and recorded over the time it takes for the gravitational wave to pass tells us two things: 1. How much the arms changed length during the light-beams' journeys and, 2. the frequency at which, or how quickly the arms changed lengths (longer then shorter then longer, etc.) in response to the gravitational wave. This information can tell us what generated the gravitational wave in the first place. In this scenario, the actual wavelengths of the beams of light have no bearing on the much more important interference pattern. The effects of the length changes in the arms far outweigh any change in the wavelength of the laser, so we can virtually ignore it altogether."

by platz 8y ago

acqq 8y ago

This article tries to explain: https://www.forbes.com/sites/startswithabang/2018/09/15/ask-ethan-if-light-contracts-and-expands-with-space-how-do-we-detect-gravitational-waves/ https://www.forbes.com/sites/startswithabang/2018/09/15/ask-... "Ask Ethan: If Light Contracts And Expands With Space, How Do We Detect Gravitational Waves?" It also links to the FAQ at LIGO: https://www.ligo.caltech.edu/page/faq https://www.ligo.caltech.edu/page/faq which for this question ends with: "This varying pattern of misaligned laser beams, observed and recorded over the time it takes for the gravitational wave to pass tells us two things: 1. How much the arms changed length during the light-beams' journeys and, 2. the frequency at which, or how quickly the arms changed lengths (longer then shorter then longer, etc.) in response to the gravitational wave. This information can tell us what generated the gravitational wave in the first place. In this scenario, the actual wavelengths of the beams of light have no bearing on the much more important interference pattern. The effects of the length changes in the arms far outweigh any change in the wavelength of the laser, so we can virtually ignore it altogether."