By Hamish Johnston in Portland, Oregon
Any guesses as to what you are looking at?
The red shape is a “person” sitting in a small room. The temperature at the surface of the person is 25 degrees – the temperature of your clothes, apparently – and the temperature of the room is 20 degrees.
The image is from a huge simulation of how air circulates in a room with floor and ceiling vents that was done by John McLaughlin and colleagues at Clarkson University.
The yellow plumes are warm air rising from the sitting person – and McLaughlin looked at how tiny particles comparable to viruses or pollen behaved in the room. He found that the plumes tend to concentrate the particles over the person’s head – and then they fall down onto the poor person!
This could be bad news in a hospital, for example, where there could be lots of nasty bugs floating around.
So if your head is getting dusty, perhaps it’s because you are sitting perfectly still in a small room.