Distant supernovae affect Earth
Life and climate change at mercy of cosmic rays
Exploding stars that spew light-speed particles in their death throes had major impact on early life on Earth and still plays a role in its climate, says a Danish report.
That charged particles from supernovae unimaginable distances away would impact life on Earth may sound like an impossible-to-track offshoot of the chaos theory to many. It equates to a butterfly flapping its wings and a hurricane starting half a world away, but now Danish scientist Henrik Svensmark has proved the linkage between cosmic rays and the Earth’s climate.
When a star explodes, it shoots out ultra-fast particles that travel through space until they hit something. When Earth happens to be in their path, and the particles bust into our atmosphere, the result is the creation of free electrons. These just happen to be the building blocks of clouds – as water vapour clings to the particles, it slowly condenses into the fluffy, white objects that an block the sun.
So the more cosmic rays piercing our atmosphere, the more clouds there are. The more clouds there are, the cooler the Earth is as a result of being in the shade.
The experiments were conducted in a vacuum-sealed chamber that imitated the lower atmosphere at the Danish National Space Centre. An ultriaviolet lamp played the role of the sun, and real cosmic rays were caught to see the effects.
About 2.4 billion years ago our Milky Way galaxy was experiencing a sort of mid-life crisis. There was a period of many supernovae explosions and a resulting hail of cosmic rays hitting Earth. Those rays affected how well life on Earth was able to thrive.
Svensmark studied sedimentary rocks from long ago in Earth’s history. The rocks serve as a veritable time-machine for the ocean’s life-holding abilities, because heavy carbon (carbon 13) is stored in rocks. When bacteria grows in the ocean it absorbs carbon 12 and leaves its heavier atomic brother to be soaked up by rocks and shell-making creatures.
Comparing the stellar record of star explosions and heavy carbon in the oceans, Svensmark concluded that life on Earth and the explosions were linked. During lulls in the star explosions, life was more likely to thrive on Earth.
“The odds are 10,000 to 1 against this unexpected link between cosmic rays and the variable state of the biosphere being just a coincidence and it offers a new perspective on the connection between the evolution of the Milky Way and the entire history of life,” Svensmark says in a statement.
Though our galaxy is a calmer place today, with less supernovae taking place, cosmic rays still play a role in our climate. Earth has always been protected from cosmic rays by solar winds. That’s the bubble of space surrounding our Solar System that is affected by the Sun’s magnetic shield. Without it, there would be so many cosmic rays hitting Earth that life would probably not survive the radiation effects.
In the last century, the Sun’s magnetic field has more than doubled in strength. As a result fewer cosmic rays can hit our atmosphere and create good conditions for cloud formation.
Fewer clouds in the lower atmosphere could be a factor in the rising global temperatures over the last century.
