Cosmic Radiation Makes Trees Grow Faster 162
Diamonddavej writes "The BBC reports that researchers at the University of Edinburgh have found that Galactic Cosmic Rays (GCRs) somehow makes trees grow faster. GCRs vary according to the 11-year solar cycle, with more GCRs hitting the Earth during solar minimum when there is a lull in the solar wind, which normally acts to protect the inner solar system from external galactic radiation. The mechanism might have something to do with GCRs increasing cloud cover, which diffuses sunlight and increases the efficiency of photosynthesis. Nevertheless, the researchers remain mystified and are requesting further ideas and research collaboration to test hypotheses. (How about Radiation Hormesis, AKA 'Vitamin-R?')" Here is the paper's abstract at the journal New Phytologist. The researchers say: "The relation of the rings to the solar cycle was much stronger than to any climatological factors. ... As for the mechanism, we are puzzled."
Re:Repeat after me: Correlation Is Not Causation (Score:4, Informative)
Are you saying that tree growth may be causing cosmic radiation?
Re:Breaking News (Score:5, Informative)
Re:Once upon a time (Score:4, Informative)
objects do not become radioactive unless they are bombarded with neutron radiation, high energy protons or extremely high energy gamma radiation capable of ejecting a proton or neutron to form a radioactive isotope. Simply irradiating an object does not necessarily make the object radioactive. Now in so far as plants having a higher growth rate due to radiation, I haven't heard much on the subject other than radiotropic melanized fungi [wikipedia.org] living near Chernobyl having a substantially increased growth rate.
Re:causality is possibly wrong (Score:3, Informative)
Though there is little variation at visible and near UV wavelengths, the solar flux has a huge (factor of three) variation with the solar cycle in the extreme UV: http://www.usc.edu/dept/space_science/sem_data/SEM%20Data%20Graphs/SEM_1996-2009.jpg [usc.edu].
EUV and X-ray photons constitute a marked fraction of the total solar output. A much larger fraction than you would expect from the short-wavelength tail of the black-body spectrum of the solar surface. Indeed, these emissions are mostly from the corona, not the surface: EUV at 171A http://www.lmsal.com/YPOP/ProjectionRoom/latest_TRACE_171.html [lmsal.com], and an X-ray image http://www.lmsal.com/YPOP/ProjectionRoom/latest/sxt/full/sxtdag_512.gif [lmsal.com].
Such high-frequency photons are absorbed in the very upper layers of the atmosphere. However, roughly 50% of the secondary energetic effects (heating, fluorescence, ionization-recombination emission, etc.) will reach ground level instead of going back out into space.
If something here on earth is varying with the solar cycle, the first cause to consider is therefore the solar EUV and X-ray flux.