“We have been forced to admit for the first time in history not only the possibility but the fact of the growth and decay of the elements of matter. With radium and with uranium we do not see anything but the decay. And yet, somewhere, somehow, it is almost certain that these elements must be continuously forming. They are probably being put together now in the laboratory of the stars. … Can we ever learn to control the process. Why not? Only research can tell.” -Robert Millikan

Ah, energy, if only you were free, limitless, and easily accessible. If you were, we could do anything we wanted, no problem. Including making those pesky, rare, unstable elements and particles.

Say hello to lead. All the way up there at element 82 on the periodic table, lead is the heaviest element that’s stable, or that doesn’t radioactively decay. Everything heavier, including your friends radium, uranium, and plutonium will all decay. That means that, given enough time, they spit out various particles and turn into lighter elements.

In order to make these, or any other heavy, unstable particle, nucleus, or element, you need a huge amount of energy. For the heavy nuclei, we either need a very intricate man-made fusion apparatus, like this one at Sandia Labs,

or some wonderful source of astrophysical energy, like a supernova!

Of course, there are relatively light, unstable particles, too. Some of them, like the muon, take less energy to make than even a single proton! A muon has nearly identical properties to an electron (including charge), but it’s about 200 times more massive. With a half-life of between one and two microseconds, a muon is actually one of the longest-lived unstable particles, measured very accurately by particle accelerators. But there’s a much more exciting place, for me, that they come from.

There are very, very high-energy particles whizzing around through space, in all directions, known as cosmic rays. They come from all sorts of wonderful places, like our Sun, neutron stars, black holes, and the centers of galaxies, but they also come from remnants of supernovae! If one of these high-energy cosmic ray particles smacks into something like a proton, say, in the Earth’s atmosphere, something wonderful happens.

We get a whole “shower” of unstable particles! We can detect a bunch of these decay products, including electrons, positrons, protons, anti-protons, and photons, but you might be surprised to learn that we also detect muons!

Why is that so surprising? Well, even if you assume these muons move at the speed of light — the speed limit governing all matter in the Universe — you still find that your muon shouldn’t make it even 1 kilometer before decaying away. Yet these muons that we find can be traced back to originating all the way in the upper atmosphere, tens of (up to even a hundred) kilometers away! In fact, there are so many of them that, if you hold your hand up to the sky, you’ll get about one muon passing through it every second!

Why do so many muons make it down to you if their lifetime is so short?

Well, one of the funny things about these muons is that they are moving at almost the speed of light. And when you move close to the speed of light, time slows down for you! This isn’t just true of twins when one of them travels in a rocket ship and one stays home, either.

It works for subatomic particles, too! While you might think these muons are aging 10, 20, or even 100 microseconds, they can move so quickly that — from their reference frame — they might not even last for a single microsecond before they make it all the way from the upper atmosphere down to your hand.

And that’s why the seemingly impossible — particles living longer than their measured lifetimes — happen all the time. Pretty amazing stuff, and a great way to get you psyched for the Labor Day weekend! Enjoy!

Comments

  1. #1 NewEnglandBob
    September 3, 2010

    So if the Labor Day Weekend arrived at nearly the speed of light then the weekend would feel to us like it lasted two months.

  2. #2 lily
    September 3, 2010

    Everything you just said is amazing. That really made my day.

  3. #3 Sphere Coupler
    September 3, 2010

    I like the way you think NewEnglandBob.

    ;?)

    and for those in other countries, they would notice nothing unusual.

  4. #4 Sphere Coupler
    September 3, 2010

    So then, if a cosmic muon traveling at near the speed of light was created in a event horizon would it ever reach the center of a black hole?

  5. #5 Timberwoof
    September 3, 2010

    Nice article.

    I often read about how important Einstein’s work on Relativity was to the understanding and development of nuclear energy. But the simple fact, easily discovered, about the ages of particle showers from cosmic rays, would eventually have led us to those principles. People would have pounded their heads on tables trying to figure out what was going on, but eventually, they would have figured it out. How much later? Would I still be on the bus, writing this on my MacBook, and posting it via WiFi?

  6. #6 josephsmidt
    September 3, 2010

    Very interesting write up and I learned a lot. It would be fun to go visit those Sandia labs. :)

  7. #7 Lycanthrope
    September 3, 2010

    Mr. Siegel, you may consider my mind blown. This is really freakin’ cool.

  8. #8 Brian
    September 4, 2010

    I always thought that bismuth, not lead, was the heaviest stable element. Surprise. It turns out that bismuth-209 actually has a half-life … of 10 quintillion years! So some people still consider it to be stable (including the folks who printed my periodic table, apparently), but technically it’s radioactive. Ha!

  9. #9 crd2
    September 4, 2010

    Ethan,

    I think I speak for all of us when i say that you should most definitely quit your job teaching and just post 3 new articles every day for our entertainment (and no were not going to pay you). I get so bummed when it takes u 3+ days to write a new piece, but its always worth the wait.

    Regarding time dilation: Its always been my understanding there is an opposite for everything in our universe. If so what would the opposite of time dilation be? If time slows down as velocity increases, why doesn’t time speed up for extremely slow or stationary objects? Can we make something move (or not move)in a way that speeds up time? If I decreasing my velocity assuming I was traveling 99% speed of light that, in essence, be the opposite b/c time is effectively speeding up as my velocity decreases, or am I missing something? If I had 3 twins, and I put one in a rocket, left one to live a normal life, and strapped the other one down so he could never accelerate, shouldn’t the immobile one age faster as the traveling one aged slower? I know the answer is no because the speed of the normal twin compared to the immobile one isn’t great enough to affect time, but I like to think if I hold really still when my girlfriend is yelling at me it will some how end soon.

  10. #10 Vagueofgodalming
    September 4, 2010

    I feel the caption on that last diagram should be “Aha, Carruthers! I have aged you forty years with my Muon mind grip!”

  11. #11 David Marjanović
    September 4, 2010

    Its always been my understanding there is an opposite for everything in our universe.

    Well… no. Newton’s actio est reactio applies to impulse; it’s not a general philosophical concept.

    If I had 3 twins [sic!], and I put one in a rocket, left one to live a normal life, and strapped the other one down so he could never accelerate, shouldn’t the immobile one age faster as the traveling one aged slower?

    Yes, but not measurably.

  12. #12 AMW
    September 4, 2010

    I love this blog. i always learn something awesome, and the great pictures are the icing on the cake. Thanks!

  13. #13 Omega Centauri
    September 4, 2010

    The temperatures and pressure needed to make fusion of heavier elements are astondingly high. Science is struggling to make the easiest reactions (between deuterium and Tritium practical. Things like ordinary hydrogen, of three heliums to make carbon are much much tougher. To get the stuff al the way to iron, which is the lightest element per nuclean (i.e. you can get energy fusing lighter elements to Iron, beyond that you are storing energy into the heavier nuclei. So stuff like Uranium weigh abit more per nuclei than Iron (or lead), and give off energy as they decay to lighter elements. Core collapse supernova happen when a stars core becomes iron, and it can no longer extract any more fusion energy (but loses a lot due to neutrinos). But in any case the difficulty of fusing these heavier elements is extreme, I can’t imagine we will ever be able to do it. (But we can collide a couple of heavy nuclei in a particle acceleration, and make tiny tiny amounts of heavier nuclei.

  14. #14 Sili
    September 4, 2010

    Brian,

    The discovery that the last isotope of Bismuth is also radioactive is very recent. I’ve only heard of it in the last year or so. So I think the printers can be forgiven for not having incorporated that tidbit yet.

    They’ve been pretty fast with Röntgenium and Copernic(i)um, though.

  15. #15 Ethan Siegel
    September 4, 2010

    Although long suspected (at least as early as the 1940s) to be unstable, Bismuth-209 was regarded as a long time as the heaviest stable element.

    But as of 2003, we’ve been able to quantify its half-life: http://www.nature.com/nature/links/030424/030424-6.html

    But I can’t fault anyone too much for not knowing about this very, very long-lived decay process. Still, it makes one wonder if elements like lead don’t decay, too, just on unobservably long timescales… for now.

  16. #16 Mike
    September 4, 2010

    My college Physics prof. performed an in-class experiment which demonstrated this very phenomenon. It was absolutely amazing to understand what I was seeing, and greatly contributed to my love of Physics.

  17. #17 wabz
    September 5, 2010

    There are very, very high-energy particles whizzing around through space, in all directions, known as cosmic rays. They come from all sorts of wonderful places, like our Sun, neutron stars, black holes …

    How does anything ‘come from’ a black hole?

  18. #18 Jimmy handbags
    September 5, 2010

    I am just trying out your new predictions platform.
    This is interesting for Collective intelligence purposes and well done.
    Could I have more background information on that project? Having worked at Yahoo!
    Answers, Flickr and Community products out of Canada, I like to discover interesting projects like this.

  19. #19 air max 90
    September 6, 2010

    Com certeza a liderança que possue as características mencionadas na sua postagem em geral não é reconhecida pela “tropa de liderados”, é permanentemente questionada, não é capaz de entregar resultados duradouros e difícilmente sobrevive no dinâmico mundo das corporações sérias e que possuem o compromisso final que é a entrega com qualidade dos seus serviços e produtos à clientela.

  20. #20 Robert S
    September 6, 2010

    wabz, there are two ways, one is radiation from the accretion disc, the other is cooler and involves virtual particle pairs where one of the particles falls into the black hole and the other flies away.

  21. #21 Yossarian
    September 7, 2010

    Ethan – awesome, awesome blog.

    Robert S – I don’t understand how a black hole can lose mass through Hawking radiation. Ok so a particle pair emerges out of the ether at a specific point in space and one of the pair is sucked in whilst the other is ejected. But why is it only ever the anti-particle that is swallowed up? Surely it’s a 50:50 and therefore the black hole will gain as much from these particles as it loses.

    Please remember my pop-physics status when posting a response ;-)

  22. #22 Eric Lund
    September 7, 2010

    Yossarian: What you are overlooking is that antiparticles have positive mass, too. So from the point of view of mass, it doesn’t matter whether the particle or the antiparticle escapes; the black hole loses that much mass either way. You are probably right about the 50:50 probability, since if the black hole were preferentially spitting out one kind of matter it would charge up enough to become noticeable.

  23. #23 BenHead
    September 7, 2010

    Still, it makes one wonder if elements like lead don’t decay, too, just on unobservably long timescales…

    Yeah, yeah, that’s what they said about protons!!

  24. #24 Sphere Coupler
    September 7, 2010

    Still, it makes one wonder if elements like lead don’t decay, too, just on unobservably long timescales…

    Yeah, yeah, that’s what they said about protons!!

    Someday…maybe we will be saying that about quarks.

  25. #25 Sphere Coupler
    September 8, 2010

    “Someday…maybe THEY will be saying that about quarks.”

    Just so I’m not misunderstood I was referring to an isolated quark, not a quark in color confinement.
    We have yet to see an isolated quark, let alone the decay of such.

  26. #26 Kevin
    September 8, 2010

    So, does the fact that the muons travel ~100km in what appears to the muon to be < 2µs imply that the from the point of view of a hypothetical observer on the muon, it's going > 50Gm/s, i.e., faster than the speed of light (300Mm/s)?

  27. #27 Kevin
    September 8, 2010

    Re post 26–the middle line of the post disappeared. I meant to say:

    So, does the fact that the muons travel ~100km in what appears to the muon to be less than 2 microseconds imply that from the point of view of an observer on the muon, it’s travelling at greater than 50Gm/s, i.e., faster than the speed of light (300Mm/s)?