"Can you tell me how the universe began?"
"As far as we know, the universe began at 1 × 10-13 quectoseconds. By 1 × 10-5 qs, the Grand Unified Theory separated into the three fundamental forces we know today: The Strong force, the Gravitational force, and the Electroweak force. But the Universe wasn't done. At the instant of the Big Bang, the observable universe was only 1 × 10-5 qm apart. In the first 0.001 qs, our portion of the Universe rapidly expanded to become 1 × 1030 qm apart. That's so big it would take us 3.3 × 1021 qs to cross."
"But we only live for 100 qs!
If we're lucky!"
"It's worse than that. The Universe is still constantly expanding. By the time you make it across, the universe could be billions of times larger. It probably won't even be the same universe you know. Below 1015 K, the fundamental forces of the universe will change, and the electroweak force will split into two unrecognizable forces."
"What do you mean by 'unrecognizable'?"
"Well, as you know, the Universe is basically a plasma of quarks in a sea of gluons. The electroweak force bonds these quarks into molecules which create our bodies. In 1018 qs, however, the electroweak force will no longer act over long distances. Even worse, the two of the three bosons which mediate the electroweak force will all but dissapear."
"What happens then?"
"Then the Universe will end. Without the electroweak interaction, there's no way for chemistry to function. In essence, the Universe ceases to support life, its particles become spread thin over unimaginable amounts of space, and it dies a cold, dark death."
"This article says that at 1 × 1017 zs, the temperature of the Universe will drop below 1.7 × 1012 K, and the quarks which make up our body will begin to condense into "hadrons". Once this happens, the chemistry we rely on to breathe, live, and think will no longer be possible. Quantum chromodynamics as we know it will come to a stop."
"Doesn't matter to me. I'll be long dead."
"It says here: "Scientists are still attempting to synthesize hadrons in the lab, but it's extremely difficult to cool quarks to temperatures low enough to bind them together. Whatever properties hadrons turn out to have, one thing is clear: The Universe as we know it will be a much different place."
"Couldn't we just keep a bunch of space heaters around?"
"I don't think so. Eventually we'll run out of energy to power them with. The Second Law of Thermodynamics means that eventually all temperatures must equalize. No, our time here is limited."
"Do you think life could happen afterwards?"
"I wouldn't bet on it. There just won't be enough free energy left in the future."
"Here, look what it says: 'By 1021 zs (a hundred billion billion zs!), more than 99% of all these hadrons will be annihilated by antihadrons.'"
"So, not only will every quark in our body be unrecognizable, but 99% of them will be gone altogether?"
"And then it looks like the same will happen with leptons. And photons."
"What are you doing after class?"
"Hey, do you think life existed before us?"
"Like life on other planets?"
"No, like life that's completely different from us. Life not made of carbon and atoms and molecules."
"Oh. Probably not."
"Like imagine right after the big bang. Could there have been life that evolved, grew, and died before us?"
"Or maybe there'll be life after we die off."
"Well, pretty soon now everything will be gone but black holes. Didn't you hear the professor? In 1040 years, every proton and neutron in the Universe will have decayed."
"Maybe those black holes will have intelligence."
"Are you kidding? When we're gone, we're gone. Nothing floating in cold dead space could ever have intelligence, let alone humanity."
"I guess you're right. When we're gone, we're gone."
How are you feeling?
My smallest sensor nerves have 1089 years of Hawking radiation left.
My largest neurons have 1095 years.
100 billion black holes make up our bodies, and none of them will last past 10100 years.
What happens then?
Then we wait for the heat death in 101000 years.
You mean 'the photons and leptons that used to be us' wait for the heat death.
Our thoughts are slowing down, too.
And we're getting farther apart.
I love you.
love you too.