Comments on: Too Big To Fail

By: Rene

Rene — Tue, 16 Aug 2016 21:52:12 +0000

In your blog article I miss the reference to the observations done by the Pierre Auger Observatory (2008) which links UHECR to supermassive black holes activity in nearby AGN galaxies (eg Cen A). They also confirmed the GZK cutoff and the the high energy decline in the spectrum of cosmic rays.

By: Brian Koberlein

Brian Koberlein — Tue, 16 Aug 2016 20:02:41 +0000

Yes, such a hypothetical craft would need to shield itself from background radiation.

By: Tom Jarzyniecki

Tom Jarzyniecki — Tue, 16 Aug 2016 17:41:24 +0000

I realize I’m writing a few days late here, and please forgive my goofy sci-fi mentality, regarding the bit about “…cosmic ray moving at nearly the speed of light will observe this radiation greatly blue shifted” Would this mean that anything moving near-ish the speed of light would have this problem? for instance, a hypothetical craft with 1g acceleration could end up moving that ‘fast’, would it have to contend with blue-shifted background radiation, and if so wouldn’t that be, well not great for things like hull integrity? I realize that moving at even fractions of the speed of light would be transformatively dangerous even in mostly empty outer space, but I was just curious if blue-shifting is a general thing we could observe if traveling fast enough.

By: K.J.

K.J. — Mon, 15 Aug 2016 20:24:49 +0000

Gravity Assist?
It seems the Uni is filled to the rim with gravitational lenses. Cosmic rays are particles with mass, and even more affected by curved space-time as photons and neutrinos are. Maybe these particles get acceleratied during their long journey by gravity, just as we slingshot our spacecrafts around planets to reach higher velocity for free. Could it be the cosmic rays are, lets say “blueshifted”, because of gravitational attraction(s) while on route?
Un-educated guess, don’t take it too serious 🙂

By: K.J.

K.J. — Mon, 15 Aug 2016 20:19:20 +0000

It also means the cosmic rays “feel” (interact with) the CMB as higher energy photons…so it gets more energy from it when they bump into each other. We observe this CMB as microwave which means it has alot less energy for us, as for the mentioned cosmic rays.

By: rich krulik

rich krulik — Mon, 15 Aug 2016 16:07:34 +0000

How is this sentence relevant to the discussion: “But because of relativity, a cosmic ray moving at nearly the speed of light will observe this radiation greatly blue shifted. Instead of a sea of faint microwaves, these cosmic rays observe CMB photons as high energy gamma rays.”

By: Brian Koberlein

Brian Koberlein — Mon, 15 Aug 2016 13:23:11 +0000

I use “observes” as a shorthand for “detects from its vantage point.” This in no way implies it has some kind of awareness.

By: Stephen Syputa

Stephen Syputa — Mon, 15 Aug 2016 00:34:56 +0000

I am a tad confused. Perhaps it’s a terminology issue. How is it that a cosmic ray OBSERVES anything? Observation requires awareness. Are you implying a theoretical observer sort of riding along on a cosmic ray?

By: Jean Tate

Jean Tate — Sun, 14 Aug 2016 21:50:36 +0000

Hmm … I thought that the supermassive black holes in galactic nuclei can interact with the surrounding medium to produce ultra-relativistic jets of particles, which radio astronomers detect by the thousand (perhaps even million)? And aren’t some of these jets within ~50 Mpc?

While it’s really challenging to estimate the composition of UHECRs (ultra-high energy cosmic rays) – what proportion electrons? positrons? protons? iron nuclei?? – some attempts have been made, and the spectrum does seem to include more heavier particles above the knee (if I remember correctly). No such ‘ground truth’ for UHECRs at or above the ankle, though, sadly …