Every material thing is made of atoms. Even a small chunk of ‘thin air’ the size of a sugar cube will contain – at sea level and a temperature of zero degrees Celsius – around 45 billion billion atoms.
But of course each atom is tiny. Comparing one to a line that’s just a millimetre long is about the same as comparing a sheet of paper to the height of the Empire State Building. And if you wanted to see with your naked eye the atoms in a single drop of water, you’d have to somehow enlarge that drop until it was more than 14 miles across.
But even atoms, small as they are, are mostly empty space – the solidity we experience around us is an illusion. If an atom was the size of a cathedral, the nucleus would only be roughly the size of a fly in the middle.
Buzzing around the nucleus are a cloud of even tinier electrons. We know that these are negatively-charged. We also know that when you try to push the negative pole of one magnet against the negative pole of another, you face resistance because the one pole repels the other.
So when you sit in a chair, you are not actually sitting on it but instead levitating above it at a height of one angstrom (a hundred millionth of a centimetre) …. because your body’s electrons and those of the chair are implacably opposed to any closer intimacy.