Our universe has an expiration date. But how and when the universe’s end will come depends on an ongoing tug-of-war between the two heaviest hitters in existence – all the matter in the cosmos versus the dark energy contained in the seemingly empty space between everything.
Birth of the Universe
To understand how this battle started, we have to go back to the beginning. Our universe burst into existence nearly 14 billion years ago during an event known as the Big Bang. This cosmic fireworks display set matter hurtling outward in all directions and sparked a runaway expansion that continues today.
As space stretches, entirely new regions spring up in between everything. So the universe is constantly gaining more ground. Galaxies are like dots on an inflating balloon – they race away from each other as new balloon material appears between them.
What’s driving this growth spurt?
The Expanders – Dark Energy
Scientists think a mysterious force called “dark energy” is responsible. This invisible energy, woven into the very fabric of space itself, packs a mean punch. It exerts outward pressure that flings galaxies apart and causes empty space to swell.
Dark energy makes up 69% of all existence – far outweighing all the physical stuff inside galaxies. So it dominates the cosmic landscape. Even though dark energy remains elusive, it’s a heavyweight champion when it comes to shaping our universe’s fate.
The Contractors – Matter
On the other side, we have all matter – from specks of space dust to stars, planets, gas clouds, asteroids, black holes, and dark matter. This collective mass accounts for 31% of the universe. Even spread thin across billions of lightyears, matter carries serious gravitational clout. Everything with mass attracts everything else. So matter pulls inward on itself and the universe, trying to slow that breakneck expansion from the Big Bang.
This enduring battle between outward pressure from dark energy and inward pull from matter will decide how our universe will end. To reveal the possible endings, we have to analyze an X factor – the behaviour of dark energy itself.
Does its strength stay steady forever? Does it get weaker or stronger over time?
Fate #1: Constant Dark Energy – Heat Death
Dark energy will prevail in the conflict if it keeps things steady. Matter becomes more and more diffused throughout freshly formed regions of space as the cosmos expands. However, that empty space also gives rise to extra dark energy, which quickens the expansion even further. This starts a vicious cycle of uncontrollably rapid growth. The universe doubles in size approximately every 12 billion years.
Eventually, matter loses all large-scale battles. But locally, gravity can keep small structures intact. In a few billion years, the galaxies nearest to us will fuse into one mega-galaxy containing trillions of stars. But other galaxies will recede from view as space expands, leaving us alone in a seemingly endless void.
Over hundreds of billions of years, all stars in the mega-galaxy will die out as the last vestiges of gas needed to form new stars disappear. White dwarfs, neutron stars, and even black holes will cool and go dark. Eventually, only burned-out stellar cores remain, orbiting quietly until gravity loosens its hold. Then one by one, they float away into the abyss.
In around 100 trillion years, matter disintegrates entirely as black holes evaporate. In the end, dark energy splits all remaining particles and molecules down to their constituent atoms and subatomic bits. Anything that could undergo change or evolution is gone. All that exists are lone particles suspended in eternally expanding nothingness. This slow-burn demise is called the Heat Death.
The universe becomes an ultra-cold, featureless wasteland – one particle per universe. Space stretches boundlessly while time ceases to have meaning. Nothing happens, and it keeps not happening for infinity. Talk about boring! Surely, other more exciting endings are possible…
Fate #2: Increasing Dark Energy – The Big Rip
Yikes! If the power of dark energy ratchets up over time, it goes berserk. Matter doesn’t just lose this battle – it gets obliterated dramatically. Dark energy will overwhelm gravity and gain the ability to tear material objects apart. Scientists call the violent end The Big Rip. And it could kick off as early as 20 billion years from now.
At first, empty space pushes in between galaxies, isolating each in a continuously inflating bubble. Soon only our local group remains visible. Within billions more years, the brutal expansion invades star systems. The dark energy isolates stars from each other and finally stretches the space between planets and their sun. Hello, intelligent life.
Months later, no object remains intact. Dark energy shreds stars, planets, moons, asteroids and spaceships alike. A few minutes after that, atoms break down into subatomic rubble as electrons rip away from nuclei. Moments before the end, black holes implode. Then finally, in the last tiny fraction of a second, dark energy overwhelms spacetime itself. Reality is torn apart at the seams.
Fate #3: Decreasing Dark Energy – The Big Crunch
If dark energy fades away, matter makes a comeback for the ages! Its gravitational pull takes over and brings everything crashing back together. Scientists call this blocked-universe body slam the Big Crunch.
Billions of years in the future, galaxies merge into globs as the universe shrinks. Eventually, stars and planets find their personal space invaded. Solar systems from across the cosmos collide in flashy mergers. But these are the least of your worries.
Radiation left over from ancient stars and explosions gets concentrated into an increasingly small volume of space. Within a few hundred million years, the inky void glows red-hot with old radiation. Any scrap of matter not liquefied or vaporized gets brutally slow-cooked. Ultimately all stars, planets and black holes condense into a searing fireball of plasma.
From there, theories diverge. Perhaps space and time rewind into a dimensionless point like at the beginning of the Big Bang. Or everything bounces back for a fresh start – a cosmic case of resurrection! Unfortunately, we have zero proof that this yo-yo effect ever happened before or will happen again. But hope springs eternal!
The Most Likely Universe’End
Based on current data, most experts think dark energy will remain constant indefinitely. So isolating Heat Death gets the most votes for how our universe will terminate. An eternally expanding cosmos may sound bleak.
But looking on the bright side, that grants us possibly trillions more years to travel between stars before the lights wink out. Perhaps our descendants will even find ways to preserve intelligence almost indefinitely through epic periods and space!
We simply have to wait and witness our universe’s next acts to know for sure. For now, the cosmic drama continues…Stay tuned!