One of the main reason for the decrease in cosmic rays, according to scientists, is the reduced solar wind. Other reasons include the sun's reduced magnetic field, and a flattening out of the solar "heliospheric current sheet," a kind of skirt around the sun that guides cosmic rays. The new level of cosmic rays still isn't as great as they were a couple hundred years ago, but it's still much higher than we're used to. Scientists claim the increase isn't dangerous to us — but that just means they haven't found any danger yet. Time to buy an extra-thick metal umbrella, I think. [NASA via Science Daily]

New Scientist reports on a new paper from David Smith at the University of Arizona in Tucson and the University of Texas, Austin's John Scalo that declares that the sun's heliosphere protection shrinks as the solar system passes through very dense gas and dust clouds, exposing us to harmful space dust and cosmic rays. Smith notes that planets orbiting red dwarf stars aren't affected by similar shrinkage due to their closeness to the star:

The bottom line is that habitable planets around red dwarfs are better protected from climate catastrophes than Earth is.

Don't feel too under threat, however; according to the paper, Earth is only being exposed to cosmic rays between one and ten times every billion years.

Sun leaves Earth wide open to cosmic rays [New Scientist]

If you're wondering how NASA scientists plan to test the limits of radiation tolerance, you may be happy to know that they're taking the Mythbusters approach, and just planning to shoot a dummy with a high energy proton beam until things go wrong, according to Space.com:

The "Phantom torso" dummy consists of natural bone, simulated skin and organs, and real human blood cells. "We put blood cells in small tubes in the stomach and in some places in the bone marrow," said Francis Cucinotta, chief scientist for NASA's Radiation Program at the Johnson Space Center in Houston. "One of the questions we have is whether the less shielded parts of the bone marrow will be [much harder hit]." ...Apollo astronauts had a near-miss between the Apollo 16 and 17 missions to the moon, when an erupting sunspot unleashed a record-setting barrage of solar radiation in 1972. Researchers plan to recreate that event's effects at NASA's Space Radiation Lab at Brookhaven National Laboratory in Upton, New York, by using a high-energy beam of protons on the European Space Agency's Phantom Torso, named Matroshka. Matroshka also has a NASA counterpart named Fred. Both dummies have flown in experiments aboard the space shuttle and the International Space Station to show how chronic exposure to background radiation affects the human body.

If they don't become super-elastic, then I'm at least hoping that one of the dummies will develop the potential to turn green and super-strong in the event it ever gets angry.

NASA to Blast Dummy Astronaut with Deadly Radiation [Space.com]