Reply to post: Re: JeffyPoooh: The explanation of interference is slightly wrong in the article...

Boffins' gravitational wave detection hat trick blows open astronomy

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Re: JeffyPoooh: The explanation of interference is slightly wrong in the article...

> > So... How come the laser beam itself isn't shrunk and stretched in precise lock-step with the 4-km long tunnel?

> Thank you! That's exactly what's been confusing me. Can anyone please point out the no doubt obvious explanation for this?

Isn't it simply because the beams are at 90 degrees? Imagine a gravitational wave approaching exactly along the line of one of the arms: that beam will be stretched along its whole length; the other beam is stretched across its width and - crucially - not along its length. It is this difference which is being detected.

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