Abstract- 20200201- 11

When Past And Future Flip!

An EcoChi Vital Abstract

This article was posted January 15th 2020, written by Kelly Oakes, New Scientist.

Breakfast in my house is a causal affair. The kettle boils because I have switched it on. The toast acquires its golden crust because I put it in the toaster. The butter makes its way to the table because I removed it from the fridge. For all the weirdness that the universe throws at us, these are simple truths that we can take for granted. The past is the past. The present precedes the future. Cause comes before effect. Except when it doesn’t. Physicists have started to realize that causality might not be as straightforward as we thought. Instead of cause always preceding effect, effects can sometimes precipitate their causes. And, even more mindbogglingly, both can be true at once. In this version of events, you would be opening the fridge because the butter was already on the table, and your toast would be perfectly golden both before and after you put it in the toaster. You wouldn’t just be making breakfast – your breakfast would also be making you. Playing fast and loose with causality does more than make for confusing mornings. It could shake physics to its very foundations. No longer having a definite order of events goes against the picture of the universe painted by general relativity, and even hints at a reality beyond quantum mechanics, the best model we have of the subatomic world. Until now, we have largely bumbled along in just one direction: forwards. “The arrow of time has a huge impact on our lives,” says physicist Julian Barbour. The arrow of time has been fired, and there seems to be no stopping it. That doesn’t mean its path is always smooth. Albert Einstein’s theories of relativity added a complication to our picture of time. It turns out that time runs slower for observers travelling at higher speeds, as well as for those in the presence of enormous gravitational fields. For example, if one of a pair of twins spent five years – by their watch – in a spaceship travelling at near light speed, upon return to Earth they would have aged a lot less than their sibling. And events that appear simultaneous to one observer can appear sequential to another. There is one important condition, however. Even if two events appear to take place simultaneously, they can only be causally connected if there is time for one to influence the other. As information can’t travel faster than the speed of light, that produces a hard limit on which events might cause each other. Because it takes 8 minutes for light to travel between the Earth and sun, for example, the sudden explosion of the sun would take 8 minutes to have any consequences on Earth. That seemed to be about as complicated as time could get. But then, a few years later, quantum mechanics got involved. Among its weirdest predictions is the notion of quantum superposition: the idea that an object can be in two different states at the same time. Letting go of our intuitive idea of causality may seem like a radical step, but it could lead to a clearer picture of how the universe really works. That is something to ponder over breakfast.