“Energy is liberated matter, matter is energy waiting to happen.” –Bill Bryson

When it comes to the Universe, you might think that energy really is only limited by rarity: get enough particles accelerated by enough supermassive, super-energetic sources, and it’s only a matter of time (and flux) before you get one that reaches any arbitrary energy threshold. After all, we’ve got no shortage of, say, supermassive black holes at the hearts of active galaxies.

Galaxy NGC 1275, as imaged by Hubble. Image credit: NASA, ESA, Hubble Heritage (STScI/AURA).

Galaxy NGC 1275, as imaged by Hubble. Image credit: NASA, ESA, Hubble Heritage (STScI/AURA).

And yes, we do find cosmic rays hundreds, thousands or even millions of times the energy that the LHC can achieve. But when we think about the Universe in detail, these cosmic rays aren’t unlimited in their energy, but are rather stopped in their tracks by the most unlikely of sources: the ultra-low-energy cosmic microwave background, left over some 13.8 billion years after the Big Bang.

The spectrum of cosmic rays. Image credit: Hillas 2006, preprint arXiv:astro-ph/0607109 v2, via University of Hamburg.

The spectrum of cosmic rays. Image credit: Hillas 2006, preprint arXiv:astro-ph/0607109 v2, via University of Hamburg.

Come get the full story on the most energetic particles in the Universe, and learn why we have those limits at all!

Comments

  1. #1 eric
    July 29, 2016

    I find cloud chambers fascinating to watch. Any time I see one in a museum or science exhibit, I usually end up standing there much longer than planned. Evidently they’re relatively easy to build (there are loads of DIY videos and guides on the web), but I haven’t yet taken my minor obsession to that stage. 🙂

  2. #2 dean
    United States
    July 29, 2016

    “I find cloud chambers fascinating to watch”

    Yes. It’s amazing to think that a device so simply described and constructed is associated with such interesting results.

  3. #3 Denier
    United States
    July 29, 2016

    Cloud Chamber! What a great idea! My kid is too young to appreciate it now, but I’m definitely going to put it in the mental filing cabinet for a future science project.

  4. #4 Elle H.C.
    July 29, 2016

    Objection: “The Large Hadron Collider (LHC) will collide in 2015 protons at √s ≃ 14 TeV. This impressive energy is still about a factor of 50 smaller than the centre-of-mass energy of the highest energy cosmic ray so far observed, assuming primary protons.”

    While for the LHC the collision rate is even 1.000.000.000 higher then in nature. It’s like saying on elephant is more intense than all the +1 billion chinese people in the world.

  5. #5 Elle H.C.
    July 29, 2016

    Et encore the link to the paper:
    http://arxiv.org/pdf/1604.07584.pdf

  6. #6 Narad
    July 29, 2016

    That illustration up top is an excellent example of why one should be careful in choosing a typeface for a math italic vee, BTW. The one used has the usual problem of looking too much like a nu to the casual eye.

  7. #7 Dean
    July 29, 2016

    My eye took it as square root of s at first glance.

  8. #8 Michael Kelsey
    SLAC National Accelerator Laboratory
    July 29, 2016

    @Denier #3: Dry ice and alcohol, and a small aquarium are all you really need. There are half a dozen versions on Instructables (http://www.instructables.com) and who knows how many more via Google. Good luck!

  9. #9 See Noevo
    July 29, 2016

    Regarding candidates for “most energetic particles”,
    why no mention of the components of the things that allegedly comprise about 75% of the universe – dark energy and dark matter?

    Probably because you don’t know what they are or what comprises them.
    Or whether they actually exist.

    Still, given Ethan’s near-obsession with the dark stuff, I’m a bit surprised he didn’t address them here.

    P.S.
    I think I heard the Democratic Party Platform includes something like ‘Explore uses of the wealth of dark energy as means of reducing fossil fuel use.’

    Sounds like another winner.

  10. #10 See Noevo
    July 29, 2016

    Typo correction: About 95% of the universe.

  11. #11 eric
    July 29, 2016

    @9: here is the Dem 2016 platform. I invite anyone and everyone to decide for themselves whether SN is accurately describing it or spouting bullflop (hint: the word “dark” does not appear even once in all 55 pages).

    Yet another example of you choosing to put words in other people’s mouths rather than attempting to read or understand their position.

  12. #12 Narad
    July 29, 2016

    Yet another example of you choosing to put words in other people’s mouths rather than attempting to read or understand their position.

    S.N. is just reusing a trolling attempt. He seems to be very proud of things that he comes up with on his lonesome and imagines to be witty, such as “get some rest, eric.” Got to get as much mileage as possible out of those zingers.

    It’s kind of like the “Neil deGrasse Tyson is the Al Sharpton of science” line. That appears to have gotten extended play on Disqustink.

  13. #13 See Noevo
    July 29, 2016

    “@9: here is the Dem 2016 platform.
    I invite anyone and everyone
    to decide for themselves whether SN is accurately describing it or spouting bullflop (hint: the word “dark” does not appear even once in all 55 pages).”

    I invite anyone and everyone to comment whether you actually took my P.S. in #9 seriously.

    I’m curious if you lack a sense of humor as much as eric.

    But thanks, eric, for giving me my best laugh of the night.

  14. #14 Narad
    July 29, 2016

    ^ This is also a pretty shopworn attention-whoring routine on S.N.’s part:

    Still, given Ethan’s near-obsession with the dark stuff, I’m a bit surprised he didn’t address them here.

    He’ll periodically show up at RI with some idiocy along the lines of “if you ever decide to write about something other than vaccines” regardless of whether any of the recent posts have had anything to do with vaccines.

    It’s not just tedious and stupid, it’s a pathetic display of the sort of self-centeredness that most people outgrow by the age of 8 or 9. His rejection by the fairer sex and resultant misogyny are no surprise whatever: everything is about S.N.

  15. #15 Narad
    July 29, 2016

    I invite anyone and everyone to comment whether you actually took my P.S. in #9 seriously.

    Nothing whatever that emanates from your keyboard is worth taking seriously. However, the uniform level of rank stupidity is more than enough reason to treat it all on a similarly uniform level.

  16. #16 Elle H.C.
    July 29, 2016

    @SN,

    For what it’s worth I have to laugh too; you guys are bickering over peanuts while someone’s trying to set you on fire. So the image I have from you is that of Michael Jackson and the famous Pepsi commercial with ***sparks*** flying around setting his air on fire, and he just keeps dancing: http://youtu.be/dgb-zCnz9mE

    🙂 🙂 🙂 🙂 🙂

  17. #17 Paul Dekous
    July 31, 2016

    @ Elle #4,

    See Zeno’s grain of milet:
    http://plato.stanford.edu/entries/paradox-zeno/#GraMil

    “… Zeno’s reasoning is false when he argues that there is no part of the millet that does not make a sound; for there is no reason why any part should not in any length of time fail to move the air that the whole bushel moves in falling. (Aristotle Physics)”

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