Hot stuff: the thermal cameras giving us a new way of seeing our bodies

How do our bodies regulate themselves – and is it even true that we have a single body temperature? New technology will tell us

Detailed thermal imaging reveals heat map of a badminton player – video

I’m one of those people who always feels cold. Maybe it’s my upbringing in the chilly north, or maybe it’s down the quirks of my own physiology, but I’m reliably found next to the fire, hiding from draughts that no-one else had noticed, or buried inside enough jumpers to stock a small shop. At the other end of the scale, when everyone else is sweating buckets, I’m basking smugly because I’m finally at a comfortable temperature.

Like most of us, my attitude towards my body temperature is similar to Goldilocks’ attitude to porridge – it’s either too cold, too hot, or 37C, which is just right. But I’ve rarely considered the fascinating details of exactly how our bodies regulate their temperature, and whether it’s even true that we have a single body temperature anyway.

Thermal cameras are about to give each of us a whole new way of seeing ourselves. The basic technology has been around for years, creeping along the path to maturity. But the latest cameras are finally able to show us the detail of the thermal world at a speed and with a resolution that comes close to a normal video camera. This is not a fuzzy, blurred world; it’s varied, revealing, and astonishingly detailed. When the opportunity came up to put one of the latest cameras to the test, I had no hesitation about what I wanted to do: take it to my badminton club to watch my own body coping with the thermal stress created by running around after a shuttle.

When I’m playing badminton, I’m thinking about the movement of my body: how do I move forward to take a net shot, and are my shoulders rotating as I hit a smash? But at the same time, my body is quietly getting on with another task of coordination: it needs to shunt away all the heat my muscles are generating.

The thermal camera shows both the scale of the challenge and part of the solution. Like the night time view over a city in the dark, my blood vessels shine out, transporting heat that will be lost at my skin. My right shoulder is a few degrees hotter than my left (I’m right-handed). It wouldn’t have occurred to me that my ankles were hot, but there they are, lit up like Christmas tree decorations. My skin temperature varies over many degrees, and in those patterns you can see clear evidence of the inner workings of me. I’ve never had much interest in watching myself on TV or video, but this is mesmerising.

And it isn’t just about me. There’s a clear reminder of the physics that makes this sort of view possible: a reflection off the wooden floor, copying my every move. We’re used to thinking of our world in terms of the colours of the rainbow, but the rainbow only contains a tiny fraction of all the light out there. In some of the colours beyond the rainbow, our world is never dark and it’s those colours that the camera is using. The light with the longest wavelength that we can see is red, at around 700 nanometres. But the camera is detecting infrared light with much longer wavelengths – 10,000-12,000 nanometres – and every one of us is a lightbulb at those wavelengths.

The fundamental laws of physics say that any object with a non-zero temperature will emit light, and the colour of that light depends in a very precise way on that temperature. The camera is working backwards from that infrared colour to calculate the position of each pixel on the thermal scale. Just like any other light, those colours can be reflected and focused, and the physics says that this camera can never lie.

It will be a few more years before cameras like this are more generally available. But this sneak peek into this new view of ourselves has convinced me that a giant leap in our appreciation of temperature is on its way. The list of possible practical applications is impressive enough, but I think that the real value will be a much broader sense of our place in the physical world that we inhabit. Everything has a temperature, and bringing all that detail into focus gives us a new way of looking at how our world works.

And now I know that my ankles glow. I can’t tell you how happy that made me.

  • Thanks to Rob Hollingworth, who wielded the camera, and my badminton coach Stuart Wardell for their enthusiasm and willingness to join in this game.
  • The first episode of From Ice to Fire: the Incredible Science of Temperature will be broadcast on BBC4 at 9pm on Thursday 15 February