Is the Universe Running Out Of Energy? | Unveiled

Is the Universe Running Out of Energy?

Energy is what everything in the universe needs to function. Humans need to eat and drink so we can keep going, while distant stars need huge amounts of fuel to continue to burn. But is this cosmic power source in limited supply?

This is Unveiled, and today we’re answering the extraordinary question; is the universe running out of energy?

The first law of thermodynamics, one of the fundamental principles of physics, is the conservation of energy: that energy cannot be created or destroyed. It can only be converted from one type of energy into another. If you’re holding a baseball, for example, your arm is full of potential energy; if you exert yourself and throw the ball, it becomes kinetic energy, causing the ball to move. Because of this fundamental rule, all the energy that will ever exist already exists, and has done since the Big Bang 13.8 billion years ago. But even if energy can’t be destroyed, that doesn’t mean it can’t be changed so dramatically that it becomes useless.

This is where the second law of thermodynamics comes in: that the entropy of an isolated system will always increase over time - with “entropy” being how much “useless” or “unavailable” energy a system has. As entropy increases, then, so too does the amount of disorder or chaos in that system; it becomes increasingly random. In the case of today’s question, the isolated system is our entire universe which, if you accept it’s an isolated system, is being filled with more and more useless energy as time goes on.

It doesn’t matter that entropy can actually decrease in a non-isolated system (like inside a human being, for example), because that decrease is always offset by whatever’s happening in that system’s surroundings. But an isolated system has no surroundings to in any way affect, dilute or reverse entropy. And so, as we live and breathe today, as everything exists right now, we could (according to some of the more prominent theories) be slowly marching towards a state where the universe is made up of 100% useless energy: maximum entropy.

There is a relatively new phenomenon to consider, too, though; dark energy. Dark energy is, by far, the most abundant substance in the universe – but it’s also the most mysterious. We don’t really know what dark energy is, just that it occupies roughly 70% of the universe and doesn’t have the same properties as baryonic, or ordinary, matter - the stuff which makes up every planet, star, and living creature on Earth, but still just 5% of the universe as a whole.

Dark energy is thought to be able to counteract gravity and is a key part of the puzzle of cosmic expansion. When, in the early twentieth century, it was discovered that the universe is expanding (contrary to what scientists previously believed to be true), we initially thought that gravity would ultimately cause expansion to slow down, drawing all objects in the universe back together. But we now know that that’s not what’s happening at all. Instead, phenomena like redshift and observations on the dimness of supernovas have proven that everything in the universe is moving further away at an accelerating rate… and it’s thought that dark energy is what’s ballooning to fill the gaps created in space. Crucially, though, we haven’t yet been able to directly observe or detect dark energy, to conduct any real research on it - though there are theories linking it to entropic energy (or force), the “useless” remnant of entropy.

Dark energy or not, though, what would actually happen if all of the energy in the universe was converted to the point that it had all been effectively “used up”?

Heat Death is one of the most popular theories on how the universe will meet its ultimate end. Also called the “Big Freeze”, it’ll happen when the universe finally reaches thermodynamic equilibrium – when there’s nothing left to convert into entropic energy. In this state, the universe will simply run out of thermal energy, meaning every star dies and every planet ceases to function. It isn’t the only theory on the end of all things, but it is in line with current models of cosmic expansion; stars really are getting progressively dimmer, not only because they’re moving further away but also as the universe runs out of the fuel needed to keep them burning. In fact, a 2010 study by the Australian National University, while focussing more on black holes, even suggested that entropy was thirty times higher than we’d previously thought. That’s thirty times more useless energy than we even predicted we had!

Findings like those would suggest that the universe is already out of the prime of its life - that it really is running out of energy - because those numbers are only going to get worse. But on the bright side, time scales for the lifespan of the cosmos are often much larger than we can even comprehend. It’s estimated, for example, that heat death will take roughly 10 to the power of 100 years, or one googol to play out; that’s a 1 with 100 zeroes coming after it! Since the sun is scheduled to expand and destroy the Earth in just a few billion years’ time, then, it’s highly unlikely that any humans will be around when heat death finally happens.

To turn the idea on its head, it highlights how we’re actually incredibly fortunate to exist in the universe at this exact point in space and time. It’s well known that we live a perfect, life-enabling distance away from our sun (even if it will eventually kill us), but some scientists suggest that we’re also in a “temporal goldilocks zone”, as well. We have all the important ingredients for life, and we really don’t have to worry about one day falling victim to the Big Freeze. Galactic Chemical Evolution has, essentially, turned out just fine for right here, right now; the universe is at just the right stage of its massive energy conversion process to make life on Earth possible. It’s not exactly that the stars have aligned for us, more that the physical fundamentals have.

Interestingly, entropy isn’t only a physics problem, though. It has also been explored in relation to human psychology and biology - with some scientists even suggesting that entropy is what’s powering human consciousness… the idea being that a person’s consciousness is, in a way, the entropic produce of their own system; an unknowable, potential measure of “how their brain works”. By some, it has even been proposed that entropy is integral to the evolution of life itself; that as life develops, it’s forging its inevitable way toward eventual equilibrium. One scientist, Ilya Prigogine, won a Nobel Prize for his study into this especially strange area of science, in the 1970s. But, that’s for another video!

For now, though, unless the laws of thermodynamics are wrong, we know that the universe does have a limited supply of useful energy… It’s not exactly “running out of” energy, but it is converting it into something else, seemingly on a one-way street toward equilibrium and heat death. But, if that is what ultimately happens, then it won’t be for at least another googol years’ time. And that’s really, really far into the future!