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Milleuros3 karma

Every time I hear about LISA I am deeply amazed that you will be able to accurately aim a laser between spacecrafts at several million of kilometers. I've studied space technologies and physics, and your technology seems almost impossible. Beyond my understanding at least.

In a few words, can you tell how will you aim the lasers so accurately even taking into account the spacecraft motion during aiming? What was in your opinion the most incredible technical feat you had to overcome?

Thanks for doing this AMA, and please keep on working I almost cannot wait for the day we get big results from LISA

Milleuros2 karma

(Not OP, but a physicist)

Precisely.

Light slows down when entering matter, e.g. the air or ice. Some particles may slow down "less" than light, and they end up being faster in that specific material.

But they are still slower than the speed of light in vacuum.

The light emitted is called the Cherenkov effect.

Milleuros1 karma

(Not OP, but a physicist)

The incoming neutrino already has a massive energy. When it interacts, it will break down and emit a charged particle, either an electron or a muon (plus some other stuff) depending on which kind of neutrino it is. Since the neutrino was going really fast, the resulting particle also has an enormous energy and goes extremely fast.

Now, the particle does not go faster than light in vacuum. But since light slows down when entering matter (e.g. ice), the particle can go faster than light in that material and create a shockwave, a blue/UV flash that can be detected

Milleuros1 karma

Hi, just watched the live announcement. Very exciting time! I'm a PhD student working on cosmic rays as well, so excuse me if I bombard you with questions :)

  • In your opinion, why didn't Icecube detect the neutron star merger last year?

  • Why aren't nearby pulsars detected? The Vela/Crab/Geminga pulsars are very bright in gamma rays, I'd suppose they also accelerate cosmic rays to high energies, probably producing neutrinos as well?

  • We know that cosmic rays can go up to 1020 eV or higher. However the detected blazar is too far away for particles of such energy to reach us, right? Thinking about the GZK cutoff here

  • What's the status on the IceCube upgrade? I met Francis Halzen, he told us about a 10 km3 detector.

    • Side question, as a future PhD in cosmic ray physics, is there a chance for me to go to the South Pole and work on IceCube itself? I would love to
  • Did you go to the South Pole? How was it?

Thank you for this AMA and congratulations for the incredible discovery.

Milleuros1 karma

Hi Andy, fellow particle physicist here, doing a PhD in Geneva.

For many physicists, the choice between academia and industry is a tough one at the end of a thesis. What do you feel is the biggest upside of doing that startup, what would you have definitely missed if you stayed in Academia? Are you still connected to the world of fundamental research?