Supernovae can predict the future

Supernovae are the biggest explosion in the universe. The result of the death of a star. And 2016 saw the biggest in recorded history. It was so great that, briefly, it was 600 billion times brighter than our sun and 20 times brighter than all the stars in the milky way. Hard to comprehend. But it is this brightness that allows scientists to measure the rate at which the universe is expanding, which in turn, could help us determine its fate.

Understanding the universe’s rate of expansion can help us build theories to how it might end. If it shrinks we may end up with the opposite of the big bang…a big crunch. However, if it continues to expand, the result is just as grim. With growing size may come lower temperatures, eventually killing us all in what physicists call thermal death. Of course, the silver lining is humans might not be around at the time for either of these options. I’m dishing out the depression here, aren’t I. Either way, by using supernovas to predict the rate of expansion we can possibly work out which of these options (or an alternative) is most likely and when.

If something is consistently the same brightness we can measure how far away it is by how dim it appears. Think of a light bulb. It's consistently the same brightness (given a few variables), but the further you move from it, the dimmer it looks. Eventually the light bulb would disappear out of view completely. In space, we call these objects ‘standard candles’ and our galaxy's standard candle is a star called a Cepheid variable. By measuring the dimness of the star we can predict its distance from us. However, just like the light bulb would be useless in space, Cepheid variables are useless for really long distances. This is because really far away telescopes can’t see individual stars. We need something brighter. Here's where the type 1a supernova comes in. It's consistently VERY bright. Brighter than ANY Cepheid variable. Bingo. To calculate this distance we use a formula called the inverse square law. This nifty bit of maths basically says the further away from an object you are, the greater the light from it will spread out.

Now we can make an experiment for measuring how much the universe is expanding. Any ideas what it could be?

1. Measure the distance away a supernova is from Earth.

2. Measure it again at a later date.

3. Has it moved closer, further away or stayed the same?

OK, I've obviously simplified this experiment quite heavily, but it gets the point across. Whatever the answer is we have a rough idea of whether the universe is shrinking, expanding or staying constant. Thanks supernova. Now I can work out which way we are all going to die (if we're not dead already).

Sweet dreams folks.