Coming up, the imminent threat of autonomous killer robots.

I think it takes us into a world in which nobody wants to live.

And just like Star Wars, lasers become effective weapons.

You can't see the laser beams, you can't hear them.

It's hard to know that anything is going on a lot of the time.

Plus, what's wrong with how we measure temperature? And what is temperature anyway? This is the

nature podcast for May the 28th, 2015. I'm Adam Levy. And I'm Kerry Smith.

Last week, Adam went on a bit of an excursion to an 18th century country manor in Buckinghamshire, just north of London,

where a group of scientists were meeting to talk about temperature.

Hanging above the grand staircase at Chichley Hall in Buckinghamshire,

there's a very stern-looking portrait of Lord Kelvin.

In the mid-1800s, Lord Kelvin called for a new temperature scale,

which would recognise that there was a coldest possible temperature, absolute zero.

It's appropriate that his portrait is staring at me, because in the next door room, about

50 scientists are getting hot under the colour about temperature all over again.

Michael de Podesta from the UK's National Physical Laboratory is one of them.

We're deciding what we mean by one degree and the process by which that gets

translated into practical reality.

And there I was thinking I knew what a degree was.

Why do physicists want to change the system?

I asked conference organiser organizer Graham Matchen,

also from NPL, what was wrong with the old way of defining temperature.

...