Today I attended my virtual morning writing group, did a bit of unpacking, met a friend for lunch, worked from a really old library with a great view for a few hours, and then went to a talk about the end of the universe.

The talk was entirely in Swedish, so this was great practice for my listening comprehension. I am posting my notes below, cleaned up and all translated to one language, but still very rough. You should have seen the orginal svengelska monstrosity I had jotted down. Note that these are very rushed notes of a talk in a language I’m still learning. Expect mistranslations/typos/inaccuracies/etc. These are just for me, as much for language learning as anything else.

And here’s how it all ends: A glimpse into the fate of the universe

13x13 lecture series at Uppsala University

By Carlos Perez de los Heros, Professor in the Department of Physics and Astronomy.

A brief history of the universe

Key ingredients shaping our understanding of the universe:

• Quantum mechanics/quantum field theory
• Elementary particle theory
• Einstein’s general theory of relativity
• Thermodynamics

Using these theories, we can make predictions about the universe’s past, present, and future.

Earth’s Fate: Challenges to habitability

We alla vet att vi ska dö. Men frågor är inte bara om oss, men om alla livande organismer. Vi ska gå steg på steg.

1. Gravitational collapse into the sun

• Gravitational waves slowly drain energy from massive objects, causing spirals inward.
• The Earth will eventually spiral into our sun, though this is billions of years away.

2. Phase locking

• Earth’s rotation may stabilize, locking one side perpetually facing the Sun.
• This creates extreme temperature contrasts: ~+60°C on one side, ~-60°C on the other.

3. Meteor impacts

• There are ~10,000 known Earth-crossing objects.
• Large impacts (e.g., 15km radius) occur roughly every 20 million years but won’t destroy the planet.

4. The sun’s evolution (Viktigt: was explicitly mentioned that diagrams were ej i skala!)

• The sun will grow into a red giant as it exhausts hydrogen fuel.
• Earth will face extreme heat before the sun becomes a white dwarf.
• End of Earth as we know it.

The sun will increase in size - not an explosion, just growing.

Our problem will be apparent way before it becomes a white dwarf, because the sun will crash into us way before that happens. It’ll get pretty warm.

Galactic fate

Evolution of galaxies

• Galaxies form, evolve, and eventually die, in… “star kitchens”? losing the ability to form new stars as materials are depleted.
• Milky Way and Andromeda will collide in ~5 billion years.
• Despite this merger, individual stars and planets will likely remain undisturbed initially.

The long-term perspective

• Over 100 billion years, all galaxies in the Local Group will merge into one large galaxy.
• By 325 billion years, the universe’s expansion isolates all gravitationally bound structures.

Heat death and the end of stars

• 10¹² years: Star formation ceases as galaxies run out of gas clouds.
• 10¹⁵ years: Last stars die, shrinking into white dwarfs or collapsing into black holes.
• The universe is populated by supermassive black holes, isolated dead stars, inert gas clouds, and some surviving planets.

The final frontier: black holes and beyond

1. Hawking radiation

• Black holes evaporate over time.
• A 1-million-solar-mass black hole would take ~10⁶⁶ years to evaporate completely.
• This process leaves behind only radiation.

2. Proton decay

• Proton decay, if it occurs, would dismantle all matter.
• Experiments suggest a proton lifespan of possibly 10³⁴ years.

3. Heat death

• After black holes evaporate and unstable particles decay, the universe becomes an empty, cold expanse filled with faint radiation.

Vacuum decay: The potential last catastrophe

• The vacuum is not truly empty but filled with quantum fluctuations.
• The Higgs field’s energy state may not be the lowest possible.
• A quantum tunneling event could trigger a vacuum decay, radically altering the laws of physics and creating a new universe.
• Entirely random and unpredictable—could occur anytime, anywhere.

An example of a fish in water was used, where a water to a fish is what a vacuum might be to us. But water isn’t always water… something can change, and then water, the fish’s ‘vacuum’ turns to ice and affects processes of everything around it, essentially making it “another world” for the fish.

Q&A Highlights

Q: Is there life after death (of the universe)?

• Life as we know it will have ended far before vacuum decay.
• Some theories suggest the universe could contract and lead to another Big Bang, but current evidence points to eternal expansion.

Q: Something about dark energy?

• A cosmological constant driving the universe’s accelerating expansion.

Q: Somthing about parallel universes, couldn’t make out specifics…

• The idea stems from trying to explain the Big Bang: our universe may be one of countless “bubbles” in a multiverse. Many years ago we thought we were the center of the world and that was not true. Then we thought our galaxy was the center of the world, not true. Now we think our universe is the center of the world. Maybe not? Our universe may be one of many.