*click click*
*click*
just kidding!
Welcome to possibly the weirdest video I've made!
What you're currently listening to is the radioactive decay of 280 bananas.
Each click is one atom of radioactive potassium converting into one atom of stable calcium and an electron.
The electron (beta radiation) hits the Geiger counter
and ionises the gas inside the machine
which allows it to conduct electricity
and make a click.
Whilst on average it takes radioactive potassium 1.25 BILLION years for half of it to decay
it is completely random whether or not a single atom will decay
which is why the clicks are so irregular.
That was a good bit!
The ratio of radioactive:stable potassium isotopes is pretty much the same in all living things
(and yes, there's radioactive potassium in humans too)
but because bananas contain more potassium than most fruits, we can detect it more easily.
280 bananas should give off beta radiation about 4200 times a second
which is a quarter of a million clicks a minute
or 1.1 million clicks in the space of a 4.5 minute video.
You may be able to notice
(if you listen very carefully)
that there are not 1.1 million clicks in this video
(though I admit, I haven't counted)
That's because most of the electrons will either be emitted in the wrong direction (away from the Geiger counter)
or absorbed before they can reach the Geiger counter
You should have realised by this point that bananas are both radioactive and harmless
(unless you throw them into a comedy club audience, in which case bruising may occur)
Radioactivity doesn't always equal "bad".
Some of it can be quite good.
Like the stuff that kills cancer cells.
It's all about the size of the dose.
You yourself are radioactive.
You contain radioactive potassium and radioactive carbon
and if we could detect it all, you'd give off about 8000 clicks a second.
That's the equivalent of 533 bananas
and a third of a banana.
You may think it's silly
(and it is)
but people use the "banana equivalent dose" to give an idea of how much radiation something exposes you to.
Eating one banana exposes you to one "banana equivalent dose" of radiation
(duh)
A dental X-ray is about 50 bananas
A flight from London to New York is about 800 bananas
(the atmosphere is so much thinner at altitude that there's less air shielding you from cosmic rays)
On a daily basis, we're exposed to the equivalent of about 100 bananas of radiation from natural sources
(or more if you live in more radioactive places like Cornwall where there's a lot of granite)
A lethal dose of radiation is equivalent to 35 MILLION bananas
In contrast, it would only take 195 bananas to kill you if you ate them
and whilst it would be the potassium killing you
you'd die from potassium chemical poisoning long before you died of potassium-related radiation poisoning
which is a cheery thought.
In reality, if you ate a load of bananas, you wouldn't become more radioactive
at least, not in the long term
because the body is very good at maintaining the same amount of potassium at all times.
When you die, however,
(and yes, I am talking about death again)
(you probably weren't expecting to confront your own mortality when you clicked on a pile of bananas)
But when you die, you stop eating
and so you stop taking in any more radioactivity in your food
be that radioactive potassium or radioactive carbon
(other radioactive elements are available)
but the radioactive atoms in your body are still randomly decaying into non-radioactive forms
so your overall level of radioactivity drops at a predictable rate after you die
and this is how we can measure how old things are using carbon dating.
We see how much less radioactive carbon a fossil has now compared to the amount we find in living things
and so can work out how long ago it stopped eating (aka died).
Who knew there's so much to banana radiation?
If you're interested in why I had 280 bananas
(and that's not an unreasonable question)
you can watch my previous (non-radiation based) video on bananas.
Thank you to Dr David Mills from Queen Mary University for lending me the Geiger counter
and to you for watching 4 minutes 33 seconds of banana decay.
Perhaps you should be questioning your life choices
(just saying)