It’s one of the most well-known car ‘hacks’ in existence and one that was even tried out on Top Gear once by Jeremy Clarkson. Picture this scenario: perhaps you want to check your car is definitely locked, or maybe you want to unlock it for passengers who’ve reached the car ahead of you. The car’s too far away for the remote central locking to work unaided, so you press the key fob up against your head, and hey presto, you see those hazard lights flashing away to display your success. Accompanied by a very loud beep if you have a modern Alfa Romeo.
We’ve seen some claim before that this is merely because you’re holding the remote higher than you might be otherwise, but it’s easy enough to disprove that theory yourself by trying the key against and away from your head. If the fob making contact with the head, your body is surely boosting the signal, but how? What’s actually going on inside that bag of meat known as ‘you’? For the answer, we can turn to YouTube, and a chap called Kyle Hill.
We’ll let Kyle get into the hardcore science-y stuff that answers this question because A) he’s clearly smarter than us and B) we’d hate to deprive him of some juicy YouTube views. But to sum up, it’s all to do with water.
Around 60 per cent of the human body is made up of water. And water, Kyle explains, responds in a very helpful way to electromagnetic waves when inside a cavity, like your body. When the radio waves from the key go into your water-dense body, a ‘dielectric resonator’ is created. This increases the amplitude of the waves, and thus, the range of the signal.
And yes, this means you don’t necessarily need a human body to pull of the trick. You could use a container of water instead, as Kyle demonstrates.
Source: YouTube via Jalopnik