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Comment by wcoenen | Hacker News Reader

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/85...

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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.

One of the funnier, not funniest

> 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?

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 :)

The osmium, too!

New theory: maybe black holes are scrapped alien neutrino detectors?

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?

>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 ;).

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?

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.

On the other hand, someone is trying to harness neutrinos for power:

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.

Why not communications? Neutrino-based communication is borderline ideal. A properly-aimed low-energy beam will make it to its target, obstructed or not.

...and through its target...

Next step in HFT.

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.

You’d think the HFT lot would jump at the chance to knock 100ms off Singapore to New York.

That's assuming the LHC has less latency than 100ms.

That's not someone harnessing neutrinos for their power, that's someone harnessing technobabble for it's ability to separate rubes from their money.

If I'm reading that paper above correctly, which despite its silly premise appears to have been seriously written (by undergrads, but the numbers pass the smell test), neutrinos have ~1/70th the power flux of solar anyhow, assuming you could catch all of them, which you can't.

Yeah I wondered about that. And their initial target application sounds pretty sketchy too. You have a brand new power source, you sell it to NASA first, not to Motorola, right?

From a little poking around it sounds like cosmic rays have a more useful power flux.

This thing is bizarre. It reads and looks like the standard "use trappings of actual science to sell bullshit", except they don't seem to be selling anything?

To be "charitable", maybe someone multiplied the solar neutrino flux/sqcm by their "maximum" energy (wikipedia numbers: 17e10 x 8e6 ~= 0.2w) and thought "that could power things!!!"

But more likely this is some sort of deliberate scam.

The science doesn't add up here. There are dozens of fluffy "this-will-save-the-world" articles without any substance which eventually led me to a single website that claims to represent a team working on that technology. That site seems to be seeking investors.

Without a miraculous scientific breakthrough the math doesn't add up. We don't know of any way to capture neutrons in a way that would provide meaningful power. For those reasons, I'll suggest this is more likely a scam than a sincere or realistic effort.

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

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.

Might be great for sending your message through space, but how to capture and read it back again?

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.

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