An international team of scientists hasaccurately measured how much of the light striking, or tanning yourbody comes from outside of our galaxy. Depending on your currentlevels of self-esteem, those photons, many of which traveled forbillions of years to reach Earth, are either incredibly lucky, or youmay have just ruined a very, very long trip.
As you wander around soaking up thesummer sunshine, your body will be struck by roughly a sextillionlight particles, or photons eachsecond. The researchers ascertained the various sources ofphotons with wavelengths varying from a fraction, to millimetres of amicron by analyzing deep images harvested by a veritable cornucopiaof space telescopes, including the Hubble, Spitzer, Herschel and WISEobservatories.
The work formed part of an overarchingeffort aiming to better understand how the universe went from a massof atoms in the aftermath of the Big Bang, to the complex and highlystructured universe we exist in today.
So here's a breakdown of the origins ofphotons privileged enough to end their existence by striking you.Prepare to get lost in a sea of 1s and 0s. The obvious and mostbountiful source of tan comes directly from our Sun, which providesan astonishing 1,000,000,000,000,000,000,000 photons per square metreper second.
We get a further300,000,000,000,000,000,000 photons per square metre per secondreflected onto us from our atmosphere. 10,000,000,000,000,000 extraphotons per square metre per second leftover from the Big Bang (as ifcreating the cosmos was not enough), and another 100,000,000,000,000photons per square metre per second reflected from random pieces ofdust scattered throughout the solar system.
Finally, we receive a mere10,000,000,000 photons per square metre per second fromextra-galactic background sources, cast out by distant stars andmatter being consumed by voracious black holes. So, when it comesdown to it, photons originating outside of our galaxy constitute ameasly trillionth of your tan. In fact, you would need to be exposed to this level of radiation fortrillions of years for it to do any kind of damage.
So, next time you're showing off yourhard earned tan, don't give all of the credit to the Sun, because thewider cosmos had a (very, very) small part to play as well.
