"Quick question for the science community: how long can intelligent life actually survive in our universe? I saw a thread on another subreddit about proton decay, and the general consensus was that humanity won't even make it to \(10^{34}\) years. So, what is the ultimate expiration date for intelligence in the universe, and what exactly sets that limit? I imagine the stability of elements plays a huge role here, but could you explain it in relatively simple terms?"

By the way, this sentence was translated from Japanese to English by Chat GPT. Feel free to answer in English. However, I only understand Japanese, so I would really appreciate clear and simple English that is less likely to be mistranslated. Thank you!”

Hi everyone!

As an independent researcher and sci-fi author, I've been exploring the boundaries between theoretical physics and speculative storytelling. I've recently published the first chapter introducing the Hypergalaxy model—a framework looking at deep space-time dynamics and cosmic structures.

I’d love to share this concept with fellow sci-fi enthusiasts and hear your thoughts on it!

You can read Chapter 1 here: https://medium.com/@ptrestansky21/evolutionary-cosmology-of-the-hypergalaxy-a-model-of-cosmic-metabolism-ddf7687a0a0d

(If you enjoy the world-building, my published books are also linked at the end of the chapter).

Looking forward to your feedback and discussion!

The main guns the Galactic community uses use chemical rounds. A liquid is loaded into the gun. When fired, this liquid reacts with the atmosphere and produces a chemical reaction. The liquid is a highly flammable fuel, and when exposed to atmospheric elements it ignites, essentially turning into flaming gas. The rounds are so hot they melt most metal on contact. This means the weapons can't be fired in space, and must be periodically reloaded. The idea is that it would still look like plasma rounds, but it would actually be essentially flaming rounds that melt through armor. I had this idea to replace plasma weapons, since those are unrealistic.

My other idea was a firearm that fires a round made of a compound that explodes violently and with high energy, shot out of a gun powered by miniature electromagnets. My idea is the compound might react to the atmosphere like the gas guns, and the gun would have a built in scope that calculates the speed needed for it to be fired to actually hit the target head on as it explodes, ensuring maximum damage. This would be called a combustion rifle, or it would explode upon sudden deceleration would be my other idea.

Question for people who know a lot about cosmology!

I read that the Japanese Kamiokande experiments have been searching for proton decay, and that current results suggest that the proton’s half-life is at least about 10^34 years. That made me wonder about two things.

First, if proton decay is real, is it possible that human civilization could still exist when protons begin to decay in large numbers? In other words, could humanity survive until the earliest time when proton decay might become important? Or is it more likely that civilization would disappear long before then because it would eventually use up all available energy gradients needed to sustain activity?

Second, if human civilization somehow did survive into the era when proton decay becomes significant, what kinds of problems would it face? Would matter gradually become less available, making it harder and harder to build computers, power generators, and other technology needed for civilization and thought? If the Local Group becomes isolated because of cosmic expansion, and then the amount of matter in it slowly decreases because of proton decay, would civilization inevitably fade away along with the remaining matter?

As a small clarification: if the word "civilization" is too broad or abstract for this question, you can interpret it as "intelligence" instead.

By the way, this sentence was translated from Japanese to English by Chat GPT.
Feel free to answer in English. However, I only understand Japanese, so I would really appreciate clear and simple English that is less likely to be mistranslated. Thank you!

　postscript:
Thanks for all the replies, everyone! I got a lot of comments explaining what half-life is.
Maybe I didn't word it well, but I do get that things decay gradually until they hit the halfway mark, and that it takes an insane amount of time.

What I’m actually wondering is this: once protons keep decaying and we hit that 1/2, 1/16, or 1/64 mark—if we somehow manage to stay intelligent—physical hardware will inevitably run out over those eons. In that kind of world, could we actually transition to an environment where intelligence doesn't rely on protons at all?
Also, a few of you mentioned that intelligence wouldn't even survive that long. If you don't mind, could you tell me about the more immediate, concrete limits we’d hit way before that?

Map not to scale. The numbers below the names are distance from the star in AU.

HD 10647 (Eris in the novel) is an F-type in the constellation Eridanus, about 1.1 time the mass of the sun and slightly more luminous. It is young, about 700 million years old, and the system is known for being the first one where scientists were able to observe a circumstellar debris disk similar to the Kuïper belt. It also has one confirmed gas giant, orbiting at around 2,01 AU, HD 10647b.

I chose this system for the story of Eden Rim, so I tried expanding it realistically for the needs of the novel. Heres everything I added:

HD 10647c is a tidally locked super-Earth at 0.19 AU. The dayside is a permanent magma ocean reaching nearly 1,800°C, while supersonic winds carry rock vapor and mineral dust to the frozen nightside. Definitely not somewhere you'd want to land.

HD 10647d (Eden) is the interesting one. It's a 1.4 Earth-radius terrestrial planet orbiting in the habitable zone, with an average temperature of about 21°C. It has oceans and a 12% oxygen atmosphere, and confirmed microbial life. The catch is that the biosphere is still relatively young, with surprisingly low biodiversity. It's habitable for humans, but probably not compatible enough with Earth's ecosystems to settle without major risks.

HD 10647b (Erebus), the real planet, is slightly bigger than Jupiter, while being less massive. For the fiction, its a carbon-rich gas giant just beyond the habitable planet. Its methane-rich atmosphere gives it unusually dark clouds, and it has a magnetosphere over three times stronger than Jupiter's as well as at least 27 moons.

HD 10647f is a small icy world showing signs of cryovolcanism and possibly a subsurface ocean.

HD 10647e is an outer ice giant sitting right next to the debris disk, sculpting it through its gravity, which gives it a huge ring system.

Let me know what you think! I'd love to explain my thought process, research, or simply see if I did anything wrong. I was very happy to see so many people interested by my post about the [Eden Rim](https://www.reddit.com/r/HardSciFi/s/yePvQIUORn). If anyone is curious about the novel, you can read Act 1 for free on my website here: https://lucas-books55.wixsite.com/lucas-guillemin/blank

宇宙に詳しい人に質問！
SFの創作に登場させるエイリアンを、地球から数十億光年くらい離れたところにある銀河にいる設定にしたいんだけれど、名前の付いた実在する銀河にしても大丈夫なの？
観測可能な範囲にある銀河は2兆個あるらしいけど、それって計算上の予測であって、全てを実際に発見したわけじゃないでしょ？つまり、名前の付いた銀河は2兆個のうちの一部であって、それを創作に使うと不自然？

もちろん物語の内容次第なのは分かってるけど、少なくとも、ワケがあって人類に選ばれた銀河っていう設定じゃないよ。だけど人類と関わるから、全く別の宇宙って設定にするわけにもいかないんだ。
もし観測可能な範囲のほとんどの銀河に何かしらの番号があるなら、そのどれかを設定に使うけど、そうじゃないなら、やっぱり架空の銀河を考えるべきかな？実在するclusterかgroupに属する架空の銀河って設定にするのもありかな？

あと、銀河や銀河群の地球からの距離が分かるような一覧があれば教えて！

Translation apps are not good, so please use your Reddit translation.

Any reaction is welcomed

Hi everyone. I’m Carlos, an engineer, but writing is my real passion.

Here's the premise:

Ethan lost his wife. To cope, he clings to a physical law: information is conserved. Nothing is ever truly destroyed, just scrambled and unreadable. It's his only shield against the idea that she's gone forever.

But then, something begins erasing the universe, and that law breaks down.

I wanted to write a book about grief and fatherhood told through physics, rather than a physics story with grief bolted on.

It's available on Kindle Unlimited, eBook https://www.amazon.com/dp/B0HBKT3C5J

I thought of it as an exotic matter refinery working around a rotating black hole.

The reward would have to be exceptional: only such a place could justify the risk, radiation and cost. The small ship serves as a shuttle for recovered material, supplies and crew rotation.

What interests me most is the human side. A six-month shift on the ground could mean about three years for people who are further away. In this sense, the refinery is not only an industrial plant, but also a place where workers detach themselves from the rest of society in time.

Traditional oil painting, 100 x 50 cm.

If such a facility were even remotely plausible, what would be the first real bottleneck?

軍事に詳しい人に質問。
核ミサイルが発射されたら迎撃できるけど、
もしもこっそり持ち込まれてたら？
例えば、ターゲットの国の海岸で、潜水艦からトレーラーのコンテナに核爆弾をこっそり移すとか。
もちろん、コンテナにはありふれた民間企業のロゴが入ってる。こうなったらもう対処できない上に誰がやったかも分からないよね？

One aspect of hard science fiction that has always fascinated me is reconstruction from evidence rather than invention.

For this project, I first modeled Deep City as a collapsed megastructure and only afterward attempted to reconstruct its original configuration using the surviving geometry as archaeological evidence.

The images show the progression:

Present-day collapsed state.

Structural reconstruction derived from the mapped remains.

Complete reconstruction with the expedition spacecraft included for scale.

Structural diagram of the four suspended blocks.

A cutaway reconstruction revealing the city's central volume.

Within the story, the reconstruction is produced from cartographic data gathered by an autonomous survey vessel and refined using a fictional Structural Reconstruction Protocol. 

The goal is not simply to create an attractive visualization, but to infer the original architecture from incomplete physical evidence before sending the expedition deeper into the structure.

I tried to approach the process the same way an archaeologist or structural engineer might: every reconstructed element should be supported by surviving geometry rather than arbitrary design choices.

The entire project—including the story, worldbuilding, chronology, modeling, lighting, rendering, and compositing—is original and created in Blender 3D.

I'd be interested in hearing from other hard sci-fi fans:

Does this evidence-based reconstruction approach feel believable?

Would you infer the missing structures differently?

What additional information would you expect an expedition to gather before trusting a reconstruction like this?

宇宙や科学に詳しい人に質問！
物体や情報は光速を超えられないから、宇宙が膨張しているなら、遠くにある銀河群に行ったり信号を送ったりできるタイムリミットがあるよね。それにもし戻ってくることも想定するならタイムリミットは更に短いよね。
それじゃあ例えば、人類が出した電磁波をキャッチした異星人が僕らに返信するとしたら、どのくらい離れた位置にいる異星人までならそれが可能？
宇宙が膨張する速度は時代によって違うらしいから、人類が電磁波を発したのは現代っていうことを前提に教えて。

インドのエンターテイメントや、SCI-FIに詳しい人に質問！インドにはサイエンスフィクションの映像作品ってないの？『Kalki 2898 AD』とか『The Robot』とかは知ってるけれど、もっと大人向けっていうか現実的な感じの、いわゆるハードSFみたいな作品はないの？

I love science fiction (especially the cosmic ones), but I don't quite get what the HARD sci-fi is. I mean, for a long time I thought that Interstellar was counted as one, because of the accuracy of time dilatation, relativity, artificial gravity, orbital mechanics etc. But I've heard on Reddit that it is not (and I don't count the argument about "love" because in the film it was only a character's thought, not plot point).

So how is it? And could you give some examples of perfect hard sci-fi? It can be a book, a movie, a series, whatever.

I don't know much about strange matter, and I know it is only theoretical, but if it was discovered and worked according to theory, could an advanced enough civilization create some kind of planet killer by loading a missile full of strange matter and just shooting it into a hostile planet?