[MUSIC]

Right now we’re sitting in the middle of a storm. Not rain, though. There’s

an invisible shower of subatomic particles pouring down on our bodies.

Every second, dozens of cosmic rays zip through your body, millions per day. Most come from

our sun, in the solar wind, but some were shot out ages ago from distant supernovas,

maybe from even beyond our galaxy.

Of course these particles are invisible, unless you've got one of these.

Behold the COSMOTRON 5000!!!

Actually this is a cloud chamber, a particle detector that's going to show us these invisible

cosmic rays.

A cloud chamber is an amazingly simple particle detector. It's just a sealed container with

an alcohol-soaked cloth on top, a metal plate on the bottom, sitting on top of a tray of

dry ice. That creates a super-saturated alcohol vapor inside, so that any charged particles

that come battering through will rip electrons off of that alcohol and clouds will spontaneously

form.

You'll see these beautiful streaks wherever that cosmic radiation comes beaming through.

Earth’s magnetic field protects us from most of these high energy particles, diverting

them toward the poles where they cause auroras as they react with the upper atmosphere. But

even with that force field in place, a few of them do make it down to us.

A lot of the radiation that we’re detecting is secondary radiation, which happens when

solar particles react with molecules high in the atmosphere like BAM and tear away subatomic

particles like WOOSH.

And this is where it gets weird.

Particles like muons are unstable, and they should only be able to travel down a few hundred

meters from the upper atmosphere before decaying and disappearing. Yet here they are, down

at the surface of the Earth. How? The answer is relativity.

Because muons are traveling more than 98% the speed of light, they experience a phenomenon,

predicted by Einstein, called time dilation.

Let's say there's a kitchen timer strapped to the muon. Because it's traveling so fast,

to us, from our reference point here on Earth, the kitchen timer ticks more slowly. But to

the muon time passes normally. So from our point of view, the muons exist for much longer

than they really should. Their lives are extended thanks to special relativity.

That is cool.

This ionizing radiation might have helped shape life on this planet.

If one of those particles knocks an electron loose from an atom in our DNA, it can introduce

a mutation. Our cells have evolved to repair that damage, so most of it’s harmless, but

on the early Earth, this ionizing radiation may have produced the first mutations that

allowed complex life to exist. Maybe at least.

I built this cosmic ray detector for about $30. I put some links down in the description

in case you'd like to try it yourself, and I hope you do. If you see anything cool, share

your results with me.

Who woulda thought, all you need to see invisible time traveling subatomic particles from another

galaxy is some rubbing alcohol and a fish tank.

Stay curious.