 How do you know how likely something is to kill you? In the 1970s, Stanford professor Ronald Howard came up with the micromort as a rather neat way of putting a number on the chances of dying while engaged in some activity like skydiving or driving down the street or eating a peanut butter and jelly sandwich. One micromort represents a one in a million chance of you keeling over while doing what you're doing. The more micromorts, the greater the likelihood of you not being around too long. Micromorts are great if you're worried about your short term chances of dying and if you are interested in finding out more about them, I'd highly recommend checking out last week's mental floss video with John Green. But micromorts aren't much good for risks that you don't notice until years later. Like the risk of dying from cancer for instance because of something you did some time ago or the chances of an early demise because you didn't eat your veggies. This is where microlives come in. To help make sense of these long term risks, University of Cambridge professor David Spiegelholter recently came up with the microlife as a way of estimating how what you do now might affect how long you live in the future. A microlife is the probability of something you do increasing or decreasing your expected adult lifespan by 30 minutes. That may not sound a lot, but racking up negative 10 microlives a day, which you could be doing if you smoke 15 to 24 cigarettes per day for example, is like taking 5 hours off your life every 24 hours you live. Most things we do can be expressed as microlives. Being a man rather than a woman for instance will cost you 4 microlives. Being considerably overweight could cost you upwards of 2.5 microlives. Eating a portion of red meat will cost you 1 microlife as well watching 2 hours of TV. Even the time you spend sitting down watching this video could be costing you negative 0.02 microlives or half a minute of your natural lifespan. On the other hand, you'll probably live longer because of the really useful stuff you learn from risk bites and this is where microlives get interesting because they indicate how some things extend your life as well as decrease it. Eating 5 portions of fruit and veggie day for instance is worth around 4 microlives, giving you on average an additional 2 hours for every day you eat healthily. 20 minutes of moderate exercise from rest is worth 2 microlives and drinking 2 or 3 cups of coffee a day is the equivalent of 1 microlife. Of course, microlives are averaged over large populations. The chances that you personally will live 30 minutes longer than you would because you just drowned 3 cups of coffee are remote. And there are plenty of other factors to consider when it comes to understanding how long you will live and the quality of your life as you age. But as a quick way of getting your head around what is good and bad for you in the long run and making smart decisions on risks, they're pretty useful. For more information on microlives and micromorts, check out the links below and don't forget to stay safe.