We've had an interesting question grace our Instagram inbox.
So it's time, once again, to: Ask ARSE!
"Hi ARSE,
I was hoping you could answer a few questions. Why can't energy be created or destroyed? Why is the amount of energy always constant, and the amount of energy can't be increased or decreased? What makes it impossible for energy to be destroyed? What makes it impossible for energy to be created?" - @Tobiastwotoes
Thanks Tobias Two Toes, if that is your real name.
Okay, firstly let's tackle what the nature of energy actually is.
What is Energy?
The question "Why can't energy be created or destroyed?" is putting the cart before the horse.
When you study physical systems, you'll see that there is some quantity that seems to be conserved. If one billiard ball hits another, it transfers its motion to the other. If you discharge a battery, heat comes out. A piston is pushed by heated gas. Over the millennia, people have observed these phenomena and found ways to use them.
It felt like something made things move around, heat up, light up, and animated the world around us. In time, these phenomena were studied in detail, and conservation laws became apparent. While the quantity could change into different forms, the amount stayed the same.
Over time, once physics was established as a science, we figured out what energy is and why it's conserved. There's actually a physical quantity with units of Joules, which is conserved in time if physical laws are symmetric in time (in the sense that the laws governing a physical system don't change with time). And Emily Noether proved this.
Therefore, the real question is why nature's laws don't change on their own. But it looks like at least on the time scales we can observe, they're not changing. Therefore, physical systems will exhibit a constant quantity through time.
Historically, we called this energy.
Why can’t energy be created or destroyed?
The simplest answer is something can’t come from nothing. And something can’t truly become nothing. Simple as that. This is a matter of existence. Nothing isn't the absence of something, it's simply a thought that there could be something, but there isn't. Without humans and without that thought, there is only existence and non-existence.
The energy to live and function is created by consuming food. Electrical energy is created by burning fuels or harnessing wind, water etc. This energy comes from something and is transformed into another form of energy again and again.
Now the 'something' is really complicated.
Will we ever know why there is something? A reason for existence? Maybe. But someday we will totally understand the something.
We're definitely aware it exists, and we've called it energy. No problem there. Living with it, trying to figure it out, and working with it is hard.
Our study of it has helped us understand energy has different conditions. Mass, wave, field, and force are all obvious, but it only has two states: working or not. At rest, all energy cannot hold information and cannot be observed.
Energy appears to have been put to work by an event. That's what we call the big bang.
Defining the 'we' is key. Sentient beings are the 'we'. The state of the energy wouldn't matter if there was no sentient life. Nobody to observe. Nothing knowing it's there. And it wouldn't matter if there was energy.
There was a lot of activity shortly after the big bang, and the first two elements were formed. Population III stars came from those elements. There were no planets, nothing to make them from, but their rapid collapsing formed the first 26 elements that made up our universe from which population II stars were born containing planets with no life as many of the elements needed were still missing.
Our universe is made up of all 92 elements thanks to the death of population II stars. Planets could now support life if they had the right conditions and elements.
Eventually, sentient life evolved and beings existed that could observe and understand the information of the universe they lived in. Suddenly, work-energy was different from rest energy.
Because we began to observe and justify the actions of energy around us.
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