Hacker Newsnew | past | comments | ask | show | jobs | submitlogin

This will blow your mind.

https://en.wikipedia.org/wiki/Super-Kamiokande

>Mounted on an inside superstructure are about 13,000 photomultiplier tubes that detect light from Cherenkov radiation. A neutrino interaction with the electrons or nuclei of water can produce an electron or positron that moves faster than the speed of light in water, which is slower than the speed of light in a vacuum. This creates a cone of Cherenkov radiation light, the optical equivalent to a sonic boom. The Cherenkov light is recorded by the photomultiplier tubes



> A neutrino interaction with the electrons or nuclei of water can produce an electron or positron that moves faster than the speed of light in water, which is slower than the speed of light in a vacuum.

This is the important but I think confusing part for many people.

The electron/positron is not moving "faster than light" (nothing can) it is moving faster "than the light" in that specific medium (water).


It is moving faster than light, but c, the "speed of light" constant, is only called that because it's the speed of light in a vacuum and water isn't a vacuum. The constant c is actually a fundamental constant of our universe relating spatial and temporal dimensions, which is why going faster isn't possible (that's time travel) but the velocity of photons in one medium or another is just an observable fact like the viscosity of a particular brand of jam.


Two parts really blow your mind:

- the images are stunning, especially if you search for "super kamiokande boat"

- even with 50 kilotons of water they record just tens of events per day: https://www.slac.stanford.edu/econf/C0805263/Slides/Raaf.pdf



And they had an unfortunate incident[1] resulting in the loss of 7000 out of the 11200 photon multiplier tubes.

Incompressible fluids are no joke.

[1]: https://www.nature.com/articles/35106691




Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact

Search: