5 ms·

The abstract of this paper is one of the funnier descriptions I have come across about how hard it is to stop a neutrino: https://journals.le.ac.uk/ojs1/index.

The abstract of this paper is one of the funnier descriptions I have come across about how hard it is to stop a neutrino: https://journals.le.ac.uk/ojs1/index.php/pst/article/view/859 https://journals.le.ac.uk/ojs1/index.php/pst/article/view/85...

dfee 6y ago
> We find that a thickness of 34000 light years would be necessary if a sheet of osmium were used, whereas neutron star matter could achieve this at 189 km thickness. We conclude that a neutrino sail is not a practical method of propulsion. Not practical, hmm?
- short_sells_poo 6y ago
  I think that even if we ignore the practicality of building it, at that thickness the neutron star material would immediately collapse into a black hole :)
  - jbay808 6y ago
    The osmium, too!
    - ur-whale 6y ago
      New theory: maybe black holes are scrapped alien neutrino detectors?
  - dmurray 6y ago
    How about a whole system of neutron stars, in orbit around each other, separated by vacuum, arranged for a given straight-line path in order that at any point in time that path intersects at least 189 km worth of neutron stars? Is this possible? I'm considering a loose definition of the word "possible" here, but could such an arrangement exist without collapsing to a black hole under gravity or being torn apart by centrifugal force?
    - serf 6y ago
      >How about a whole system of neutron stars, in orbit around each other that's a neat idea. the orbital mechanics involved are pretty mind-boggling, but I guess a civilization that could create a system of neutron stars could probably deal with the math ;).
  - ajuc 6y ago
    Even a very small blackhole would catch all neutrinos that pass it, right? So maybe we could use them as neutrino detectors and/or sails :) Hm, can we detect big black holes that way - looking at their neutrino shadow?
typon 6y ago
Thanks for sharing that, hilarious. Neutrinos really are shy aren't they?
- googlryas 6y ago
  I always thought neutrinos would be a much better medium for other civilizations sending out messages to the rest of the universe because of this fact. Radio waves like SETI is looking for attenuate at a significant rate and seem very primitive compared to harnessing neutrinos.
  - SmooL 6y ago
    Might be great for sending your message through space, but how to capture and read it back again?
hinkley 6y ago
On the other hand, someone is trying to harness neutrinos for power: https://www.power-technology.com/features/neutrino-energy-harnessing-the-power-of-cosmic-radiation/ https://www.power-technology.com/features/neutrino-energy-ha... One of my far-future-tech fantasies is that we someday learn to make photovoltaics that are powered by cosmic rays and/or neutrinos.
- JumpCrisscross 6y ago
  Why not communications? Neutrino-based communication is borderline ideal. A properly-aimed low-energy beam will make it to its target, obstructed or not.
  - carlob 6y ago
    ...and through its target...
  - saberdancer 6y ago
    Next step in HFT.
  - skykooler 6y ago
    Serious answer: because bandwidth is terrible. A transmitter the size of the LHC can only produce enough neutrinos (a few quadrillion per second) for a detector to receive a hundred per second or so. Accounting for noise, that means you can only achieve a few bytes per second at best, and again, that's with using the LHC to produce the neutrinos in the first place. With far less power you could instead use ultra-low frequency radio waves and still get better bandwidth.
    - iso947 6y ago
      You’d think the HFT lot would jump at the chance to knock 100ms off Singapore to New York.
      - nikanj 6y ago
andrewflnr 6y ago
I'm surprised it's still so thick with neutron star matter. I would have thought that was at least a scifi route to efficient neutrino capture.
spodek 6y ago
Then you probably haven't read John Updike's poem Cosmic Gall. All of us who worked on neutrinos at FermiLab did. Neutrinos, they are very small. They have no charge and have no mass And do not interact at all. The earth is just a silly ball To them, through which they simply pass, Like dustmaids down a drafty hall Or photons through a sheet of glass. They snub the most exquisite gas, Ignore the most substantial wall, Cold-shoulder steel and sounding brass, Insult the stallion in his stall, And, scorning barriers of class, Infiltrate you and me! Like tall And painless guillotines, they fall Down through our heads into the grass. At night, they enter at Nepal And pierce the lover and his lass From underneath the bed - you call It wonderful; I call it crass.
- PKop 6y ago
  One of the funnier, not funniest
lokedhs 6y ago
A physics paper I was actually able to fully comprehend. I'm happy this paper exists for no other reason than to make an amateur like myself feel they understand something.

dfee 6y ago

> We find that a thickness of 34000 light years would be necessary if a sheet of osmium were used, whereas neutron star matter could achieve this at 189 km thickness. We conclude that a neutrino sail is not a practical method of propulsion. Not practical, hmm?

short_sells_poo 6y ago
I think that even if we ignore the practicality of building it, at that thickness the neutron star material would immediately collapse into a black hole :)
- jbay808 6y ago
  The osmium, too!
  - ur-whale 6y ago
    New theory: maybe black holes are scrapped alien neutrino detectors?
- dmurray 6y ago
  How about a whole system of neutron stars, in orbit around each other, separated by vacuum, arranged for a given straight-line path in order that at any point in time that path intersects at least 189 km worth of neutron stars? Is this possible? I'm considering a loose definition of the word "possible" here, but could such an arrangement exist without collapsing to a black hole under gravity or being torn apart by centrifugal force?
  - serf 6y ago
    >How about a whole system of neutron stars, in orbit around each other that's a neat idea. the orbital mechanics involved are pretty mind-boggling, but I guess a civilization that could create a system of neutron stars could probably deal with the math ;).
- ajuc 6y ago
  Even a very small blackhole would catch all neutrinos that pass it, right? So maybe we could use them as neutrino detectors and/or sails :) Hm, can we detect big black holes that way - looking at their neutrino shadow?

typon 6y ago

Thanks for sharing that, hilarious. Neutrinos really are shy aren't they?

googlryas 6y ago
I always thought neutrinos would be a much better medium for other civilizations sending out messages to the rest of the universe because of this fact. Radio waves like SETI is looking for attenuate at a significant rate and seem very primitive compared to harnessing neutrinos.
- SmooL 6y ago
  Might be great for sending your message through space, but how to capture and read it back again?

hinkley 6y ago

On the other hand, someone is trying to harness neutrinos for power: https://www.power-technology.com/features/neutrino-energy-harnessing-the-power-of-cosmic-radiation/ https://www.power-technology.com/features/neutrino-energy-ha... One of my far-future-tech fantasies is that we someday learn to make photovoltaics that are powered by cosmic rays and/or neutrinos.

JumpCrisscross 6y ago
Why not communications? Neutrino-based communication is borderline ideal. A properly-aimed low-energy beam will make it to its target, obstructed or not.
- carlob 6y ago
  ...and through its target...
- saberdancer 6y ago
  Next step in HFT.
- skykooler 6y ago
  Serious answer: because bandwidth is terrible. A transmitter the size of the LHC can only produce enough neutrinos (a few quadrillion per second) for a detector to receive a hundred per second or so. Accounting for noise, that means you can only achieve a few bytes per second at best, and again, that's with using the LHC to produce the neutrinos in the first place. With far less power you could instead use ultra-low frequency radio waves and still get better bandwidth.
  - iso947 6y ago
    You’d think the HFT lot would jump at the chance to knock 100ms off Singapore to New York.
    - nikanj 6y ago

andrewflnr 6y ago

I'm surprised it's still so thick with neutron star matter. I would have thought that was at least a scifi route to efficient neutrino capture.

spodek 6y ago

Then you probably haven't read John Updike's poem Cosmic Gall. All of us who worked on neutrinos at FermiLab did. Neutrinos, they are very small. They have no charge and have no mass And do not interact at all. The earth is just a silly ball To them, through which they simply pass, Like dustmaids down a drafty hall Or photons through a sheet of glass. They snub the most exquisite gas, Ignore the most substantial wall, Cold-shoulder steel and sounding brass, Insult the stallion in his stall, And, scorning barriers of class, Infiltrate you and me! Like tall And painless guillotines, they fall Down through our heads into the grass. At night, they enter at Nepal And pierce the lover and his lass From underneath the bed - you call It wonderful; I call it crass.

PKop 6y ago
One of the funnier, not funniest

lokedhs 6y ago

A physics paper I was actually able to fully comprehend. I'm happy this paper exists for no other reason than to make an amateur like myself feel they understand something.