back to article Ten-trillionths of your suntan comes from intergalactic photons

Astronomers led by the International Centre for Radio Astronomy Research (ICRAR) in Australia have calculated that ten trillionths of your suntan comes from beyond our local galaxy. Professor Simon Driver, lead author of the research, published today in The Astrophysical Journal, said that each square metre of the Earth is …

  1. Bronek Kozicki
    Coat

    Ten galaxies worth of sunscreen, please

  2. Anonymous Coward
    Anonymous Coward

    WRONG

    I don't have a suntan, because I live in a cyberpunk underground lab, amongst the whirr of CPU fans.

    I get my vitamin D by scraping lichen off rock-faces in hydroponics.

  3. Pascal Monett Silver badge

    "10^21 photons pour into each square metre of the Earth every second"

    Well, each square meter facing the Sun, that is. Which is still 250,036,000 km2.

    So that's 2,550,360,000,000,000,000,000,000,000,000,000 photons per second that are bouncing off Earth's surface.

    Yikes.

    1. Anonymous Coward
      Anonymous Coward

      Re: "10^21 photons pour into each square metre of the Earth every second"

      Well, they aren't ALL bouncing off the surface, or it would get cold rather quickly!

    2. asdf

      Re: "10^21 photons pour into each square metre of the Earth every second"

      Nuclear fusion is where its at baby. Still blows my mind the average energy output per mass unit isn't much greater than a lizard's energy output (when averaged over whole sun). The Sun however makes it up on the number of units of mass (though of course a small minority of the Sun is producing the vast majority of the energy).

    3. Bill Gray

      Re: "10^21 photons pour into each square metre of the Earth every second"

      Minor point: it's each square metre perpendicular to the sun, and many of those 250 million square kilometres are tilted away at some angle. Rather than use half the surface area of a sphere (2pi * r^2), use the cross-sectional area of the earth (pi * r^2). So it's 1.27 x 10^33 photons/second, half the result you got.

  4. Anonymous Coward
    Anonymous Coward

    Ah, now I know ..

    .. where freckles come from. From Spaaaaaaace.

    :)

  5. Anonymous Coward
    Anonymous Coward

    Bathe in the warmth for trillions of years?

    Damn, you mean I won't be able to get a startan?

  6. m0rt

    "But don’t worry, although energetic intergalactic photons - at micron wavelengths - can be damaging, you'll need to bathe in the warmth for trillions of years before they inflict long lasting damage. Solar photons are more dangerous as they make up a larger proportion."

    But if your atoms in your body are effectively replaced every 7 years (G.C.S.E Biology in the earliest years so this might be wrong), does this mean that it isn't a problem?*

    *looking past the obvious of near as dammit immortality not yet attainable

  7. Anonymous Coward
    Anonymous Coward

    "But fear not – our galaxy has in-built SPF protection"?

    First time I've heard the inverse square law described as that...

    1. Anonymous Coward
      Coat

      Re: "But fear not – our galaxy has in-built SPF protection"?

      First time I've heard the inverse square law described as that...

      Same applies if you're big boned. Applying the Journalistic Ignorance of Physics principle, you can see that if a hambeast has twice the surface area as a non-hambest, the exposure will be halved, because we all get the same photonic exposure.

      Or something like that.

  8. allthecoolshortnamesweretaken

    "The study is part of ICRAR’s aim to understand exactly how atoms in the early universe clumped together to form molecules and eventually whole galaxies."

    Duh, someone didn't follow the instructions on the packet and didn't stir the mix properly*. So naturally it clumped.

    * Seven times clockwise, one time anti-clockwise, repeat.

  9. Nathan 13

    poor intergalactic photons

    They have travelled for millions, even billions of years and the 1st thing they could strike is possibly an overweight blob of human skin.

    Still as they have been travelling at the speed of light, to them the billion year journey passed instantly lol

  10. Rich 11 Silver badge

    Pitiful

    Half of the ultraviolet photons coming from other galaxies are also made less harmful as they bump into the dust grains, losing energy in the process.

    Imagine tirelessly travelling all that intergalactic distance -- millions upon millions of light years -- only to get knackered by bouncing off a speck of dust before reaching anywhere interesting. Poor photons.

    1. Little Mouse Silver badge

      Re: Pitiful

      I hate it when that happens too, mostly because it means that I have to ponder the concept of photons losing energy. Do they slow down? Do they lose mass?

      Damn you, relativistic physics!

  11. Anonymous Coward
    Anonymous Coward

    So the advice is still to avoid sunbathing at night?

    1. tony2heads
      Unhappy

      @disgustedoftunbridgewells

      I fear that for many readers of El Reg they should avoid sunbathing completely; this is not for their benefit, but for those around them.

  12. JeffyPoooh
    Pint

    "Ten-trillionths"

    "Ten-trillionths"

    Is that ten one-trillionths, or one ten-trillionth?

    100:1 ratio of confusion possible. All hinging on the interpretation of the little dash.

    I presume the latter, but I wouldn't bet much.

    1. JeffyPoooh
      Pint

      Re: "Ten-trillionths"

      Found another source.

      Apparently it's ten one-trillionths. The bigger of the two interpretations.

      I'd write that as 'ten trillionths', not "ten-trillionths". The dash adds only confusion.

  13. David 132 Silver badge
    Boffin

    Oh no, another thing to worry about.

    But don’t worry, although energetic intergalactic photons - at micron wavelengths - can be damaging, you'll need to bathe in the warmth for trillions of years before they inflict long lasting damage.

    "An experiment was carried out to determine the harmfulness of intergalactic photons.

    Step 1) A volunteer human being was placed in an environment with exposure to the photons,

    Step 2) The condition of the volunteer was checked after 2.0 trillion years,

    Step 3) The volunteer was found to be very dead.

    Conclusion: intergalactic photons are very harmful to humans over the trillion-year scale. Also, based on further experiments of the same methd, we can confidently state the same is empirically true of: oxygen, Labrador puppies, honey, and soft fluffy pillows."

  14. jake Silver badge

    One wonders ...

    ... how long it'll be before the holistic set manage to "package" intergalactic photons and try to pass them off as a "sunburn cure".

  15. herman Silver badge

    Their arrogance is mind boggling. These photons travel 100s of light years, to come and hit me. Why? I haven't done anything to them.

  16. This post has been deleted by a moderator

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