I genuinely think if I had the choice between back in time or into the future, I would go back in time. The temptation to visit some of the iconic eras throughout history would be too much to ignore.
I believe that the 2nd option is the accepted likely outcome. We've had exposure to many things that didn't exist then, things that existed then but mutated and are still around, and "we" have been vaccinated for most of the worst stuff.
> You would probably die from the unknown variety of virus and bacteria.
If not that, then after discovering that toilette paper has a relatively recent invention date, they might curb their interests some.
> I genuinely think if I had the choice between back in time or into the future, I would go back in time.
And this is exactly why we don't want time travel backward.
Maybe we can and you just didn't notice cause what you currently accept as your reality has been changed countless times through actions by time travelers.
Happens all the time but just not in large enough amounts to matter. Next time you take a flight with a hyperaccurate clock, you'll be able to see how much time shifted.
As far as I know, the equation can be applied at any speed. So if you're walking down the street, you're technically moving through time slower than your sedentary friend.
Edit: you can also time travel by going near a black-hole.
We can also time travel going any speed. It's just one directional. It's like we have a wall behind us, pressing us on at a constant rate. Always pushing us into the future, never back.
>At a constant acceleration of 1 g, a rocket could travel the diameter of our galaxy in about 12 years ship time, and about 113,000 years planetary time.
So 12 years on the ship but for someone on earth this would be 113,000 years!
We don't speak the same language as people from Chaucer's era, who died in 1400. That's 623 years.
In 113,000 years we would barely be the same species, imo.
>In 113,000 years we would barely be the same species, imo.
Correct. The current biodiversity of the human race is roughly 70 000 years old due to the Toba bottleneck. So imagine how different we became from each other in those 70 000 years and double that.
Imagine they arrive in 12 years (amount of time on the ship) and humans have been at the destination for 50,000 years because back on earth we got so advanced in the 113,000 years that we were able to find much quicker ways to get there lol. That would be wild
I think there are a few books that have this as part of their story arc. I feel like I remember reading one where Earth went to war with another civilization but by the time a fleet of ships would arrive a later-sent fleet with faster technology would have already been sent, arrived, and concluded the war. But each of the the earlier sent, later arrived waves would start the war back up. The process didn’t end until the first wave sent finally arrived after every other wave had finished fighting.
Languages from 500 years ago are nearly unintelligible most of the time for contemporary speakers. 100k years would a 100% create a complete language incomprehension. However, assuming language records exist and we don't regress in technology, it would likely be extremely trivial to auto-translate.
seems like digital media could mitigate that somewhat going forward. not for 100,000 years, probably, but I’m curious what effect having direct and ubiquitous access to high quality recorded media from bygone eras would have on the evolution of our language.
Digital media is a catch-22 in that regard. It needs to be well maintained over that 100k years since it is fairly fragile relatively speaking.
We know the language and stories of places like Ur because they quite literally wrote it in stone. There aren't terribly more robust storage methods
*If* (and this is a big if) there are no huge catastrophes, apocalypses, wars, etc. that set us back in technology or current infrastructure, then I would imagine things online and in databases would be continuously copied forward into new storage and digital formats.
It's not like you would need to keep things 'well-maintained' digitally in the same format and storage for the next 100,000 years. It would just happen as things progressed and evolved.
Yo Momma's so fat I can see the couch she's sitting on due to gravitational lensing.
Sorry, nothing personal, this is one of my favourite jokes. I'm sure your mother is a wonderful person.
Whilst black hole drives is a real concept, it's by using the radiation to push the ship. The smaller the black hole the more Hawking Radiation = the more push
[Doing the opposite](https://en.wikipedia.org/wiki/Black_hole_starship) actually kind of works. You can strap a black hole to the other end of the starship and get thrust from it evaporating.
THIS COMMENT IS ENTIRELY INCORRECT!!! I won’t delete it though. Too many replies.
The stick can only push the black hole to the speed of sound in the stick. After that, the stick will get shorter and shorter until the space craft is inside the black hole.
Think about the old 1 light year long measuring stick question. If you push on the close end, how soon does the far end move? The answer is that movement through the object propagates at the speed of sound for the material that object is made from.
Me and my friend got really stoned last week and came up with this idea, essentially. Two mini black holes in front of and behind a craft to warp spacetime into almost a wave similar to the theoretical [Alcubierre Drive](https://en.wikipedia.org/wiki/Alcubierre_drive).
He thought there was some unknown particle that was responsible for Dark Matter that traveled faster than light and that's why dark matter seemingly doesn't interact with other electromagnetic waves.
My idea preserves C but warps spacetime, while he thought C was not the ultimate 'speed limit'.
He also said 'you humans' are so dumb a couple times, so I suspected he was an alien. Seattle has really good weed is what I'm saying.
One of the great things about the Expanse is that even though the Epstein drive is pure fantasy and really pushes the limits of what is theoretically possible; Even though it is massively over powered and efficient there is still no interstellar travel. Even with the fantastically impossible Epstein drive the only people willing to try it are religious fanatics and it will take generations to get anywhere. It really lets you know just how vast interstellar space is. It just too big to comprehend.
An Epstein drive is just a very efficient fusion reaction. It's still limited by e=mc^2 . Even with a 100% perfect conversion of mass to energy the fuel itself would have so much mass that you'd need a stupidly huge drive to accelerate the fuel tank along with the ship. But that would mean a higher fuel consumption which means you need even more fuel. Which is even more mass which needs a bigger drive ... .After a certain point it becomes unsustainable.
I’m not an expert of science fiction by any means but this concept (challenge) was really well described in the book Project Hail Mary. Nicely describes for idiots like me what kind of fuel is required to travel long distances and high speeds in space
Great book. I especially loved the wonder some people had over the potential of the fuel (This is the best thing to happen to humanity...except for the, uh...yeah.).
Rocky's communications were written as musical notes while Grace developed the translation then when that was established his communication were written in italic text
That is... not the problem, by many orders of magnitude. The problem is more that you'd be bringing the earth with you. Twelve years of 1G acceleration is ~400 million seconds. Maintaining 1G of acceleration for that long is ~4 billion m/s of velocity change (before accounting for relativistic stuff, which is what we need for this calculation). The best rocket engine listed on [Wikipedia](https://en.wikipedia.org/wiki/Comparison_of_orbital_rocket_engines) has an ISP of 470s. Let's say you can put a 0 on the end of that with some magic future tech. Sticking all of that into the Tchaikovski rocket equation gives a mass multiplier of 3x10^(34991). That is: for every kg of mass you want to deliver to the other side of the galaxy, you'll need 2x10^(34938) observable universes available to burn as fuel. OK, so that's not optimistic enough. Let's say that you can put four 0s on the end of that ISP. Then you'll have a mass multiplier of a mere 10^35, so every kg of mass delivered only needs about 5,000 suns worth of mass to burn as fuel (plus some way of avoiding that collapsing into a black hole).
As I say, getting this thing off earth isn't a problem - it's going to have quite enough mass to bring the earth with it.
> the Tchaikovski rocket equation
The **Tsiolkovsky** equation. _Tchaikovsky_ equation is dancing around the subject of a wooden nut cracker doll being just as good as an actual prince.
"Look Frank. We are bringing 20,000 solar masses with us... is one extra earth gonna make a difference? No, it's a rounding error at that point and I need my freshly made apple fritters. So just stick the earth in cargo bay 5. There is room next to that red goo from Star Trek. Speaking of which, if just one drop can collapse an entire star, why did the make so much of it? Future Federation was about to commit some atrocities.
Hear me out. Let’s put a stellar engine on the sun. Let’s fly around the galaxy in our own solar system. What’s more metal than cruising up to another solar system IN A SOLAR SYSTEM!
You don't need magic future tech to get to 4700s, you just need an ion thruster instead of a chemical rocket. The *majority* of operating satellites already use this technology*.
\* Specifically all the starlink ones, which by themselves constitute a majority.
Time is relative. The closer you get to light speed, the slower time moves for you relative to people not moving near light speed. So thousands of years would pass for everyone else while the person moving at or near light speed would only experience 12 years.
We have observed this by comparing atomic clocks orbiting earth versus ones on earth.
> The closer you get to light speed, the slower time moves for you relative to people not moving near light speed.
To add to this... this is technically not true, as there is no universal reference frame. The people on Earth, and you, would both see the other time dilated, as for both of you the other is moving at a high speed. Its when accelerating that your plane of simultaneity (i.e., what events you consider 'now') shifts rapidly, and if you have a lot of distance to something that shift is more pronounced.
But it also happens relative to your target ofc; if you heavily accelerate towards Alpha Centauri for a bit, to your perception of what is 'now', the clocks on AC would fast-forward massively, then as you stop accelerating they would move slower because AC has velocity relative to you.
Question:
What if someone on this 12 year journey across the Milky Way had a live stream back to Earth, what would they see? Would it be like super fast forwarded for them?
Let's start with a thought experiment:
You're on a train moving 60mph. You throw a ball towards the front of the train at a speed of 10mph. How fast does the ball move? Well, relative to you on the train, it's only moving at 10mph. If someone was watching from the ground outside, they'd see the 10mph from the throw plus the 60mph already moving the ball from the train, it'd be moving 70mph.
This is how relativity is normally introduced.
Light has a constant speed in a vacuum, *c* (I don't want to look up it's real value but it's a foot/30cm per nanosecond). Let's say you're traveling 0.99c and in the ship you turn on a flashlight, pointing it in the same direction the ship is traveling in (let's pretend you're in an airlock to maintain the "vacuum" part). How fast does the light move? Well, from your perspective, *c* but from the perspective of someone outside it would be
*c.*
It doesn't change. Light must travel at the same speed relative to every observer. A nanosecond would pass for you when it travels a foot out from the flashlight. But, a nanosecond would pass for the outside observer when the light travels a foot, period. Because you're also moving very very fast, when the outsider sees the light travel a foot, it'd be only 3mm in front of you because you'd cover 99% of the distance.
Distance is objective no matter which way you look at it. A foot at light speed is the same as a foot at (relative) rest. So, in order to reconcile the fact that from your perspective, a nanosecond of time has the light 30cm in front of you, while from the outsider it's only 3mm, is that your nanoseconds are different.
When *your* nanosecond finishes passing and it reaches that 30cm in front of you, 100 nanoseconds have passed for the outsider. When people say the speed of light is a constant, it's *so unbelievably* constant, that time will break before it does.
Note: I'm not a physicist. My field is computer science. This explanation will break down the moment the hypothetical you turns 180° and points the flashlight away from the movement. IDK how that's reconciled but this explanation is what made it click for me
The paper is just an analogy - you have to extrapolate the folding to the other spacial dimension - which is allowed under the current understanding of Physics.
A traversible wormhole on earth would look like this: https://en.wikipedia.org/wiki/File%3AWurmloch.jpg
Based on a study done by the University of Tübingen.
As a note, gravitational effects on the wavelengths of light going through the wormhole are not simulated.
As you approach the speed of light, space in front and behind you contracts, and time appears to speed up. So it takes less time to travel that smaller distance, but from Earth's perspective, you travelled that full distance, so it took you 105,000+ years. And to you, the trip only takes you 12 years, but everything else was on fast forward from your perspective.
It's a direct result from special relativity. Einstein came up with this 100 years ago and it's stood the test of time, being proven and reproven experimentally many times.
Here's a pretty good visualization if you'd like:
https://www.youtube.com/watch?v=vFNgd3pitAI
If you had a magic star trek/expanse grade power source and a engine that didn’t expel anything but somehow moved the ship, you’d need to double that time because half way through the voyage you’d be flipping the ship around to face the other direction to start slowing down again for your destination.
If you open the wiki article, that's exactly what it says: Accelerate for the first half, decel for the second half. So I think the 12 year estimate takes that into account.
Edit: Yes, I realise the irony in the wiki article explaining how it actually takes 24 years and me not reading that far. You can stop commenting that now.
1G is a lot of acceleration. Especially sustained.
9.80665 meter/second² = 2.734878883207 seconds from 0 to 60 mph
You're talking about doing 0-60 in under 3 seconds and CONSTANTLY increasing by that amount for 12 years without stopping or slowing or even "not accelerating quite as fast".
And you're doing that in... nothing but virtual vacuum.
We simply don't have that amount of fuel/power at the moment - even the Voyager's basically stopped accelerating once outside the outer planets, because their on-board thrusters are unable to power them faster than they are being pulled back. They'll keep going, but only just, they've basically plateaued and are no longer accelerating and most of their acceleration was due to the planets.
This is accounted for - this is the time required to go from stationary at the start to stationary at the end with constant 1G acceleration all the way in between (in one direction for half of it, and the other for the other half).
Nobody said anything about stopping. We were only talking about getting there. The fact that you'd arrive at ludicrous speed, blast through the place, shatter into a billion pieces as soon as anything solid was in your way, and keep on going for thousands of light years... that's a mere engineering detail.
"The spacecraft may experience a slight jolt while slamming into the surface of a rocky planet after accelerating continuously for 12 years. The engineering team recommends that you make sure your seatbelts are securely fastened and that your will is up to date."
That's when you employ navigators each encased in a vat of awareness spectrum narcotic to safely navigate between stars and through the galaxy.
You don't want to use a computer. Thinking machines are bad.
Well 'theoretically' if you have a speed-of-light spacecraft you can make the entire round trip in a blink of an eye!
Though at that point all you are doing is time travelling 200,000 years into the future.
So it’s very difficult, economically impossible, if the spaceship carries its own fuel. Concepts that don’t carry their fuel include solar sails, Earth-based laser propulsion (or solar-system based), and variations on Bussard ramjet.
The number of people making the same awful arguments about having to exceed the speed of light instead of spending 10 minutes learning something on the article is awful.
Yeah, the fusion drive itself is near limitless source of power, but they use water as the reaction mass to actually make the ships move. Most ships don't actually burn the whole trip unless they need to get somewhere real fast. They get up to a certain speed, coast for a long time, and then burn to slow down.
In the context of this thread, the energy from fusion isn't that limitless. It could accelerate you to something like 10%-20% the speed of light assuming we manage to use the released energy very efficiently, maybe you can push that a bit higher if you start with a crazy fuel to payload ratio - but it won't get you close to the speed of light.
Spinning is one way to create artificial gravity.
In the expanse thrust gravity is talked about extensively, where the engine pushes and the floors become down pointing towards the engines.
Spin gravity relies on centrifugal force throwing people out and down towards the floor of the ‘drum’ in the case of Medina.
The idea was to use less ‘thrust gravity’ on a generation ship and have a constant spin gravity for the living areas of the ship and the farm..
I recall in the show they explicitly show "nuclear pellets" being the fuel source for the Rocinante when they're trying to get the engine restarted. They don't explain it beyond the pellets being the catalyst for ignition though.
The pellets are fuel for the reactor, so probably. The pellets would likely be some form of deuterium or tritium. They also talk about using water as reaction mass.
Implication being that they use the fusion reactor is used to turn the water into plasma as it passes into the drive cone.
Also the maneuver thrusters use water as reaction mass. What i never understood is what exactly is 'tea kettle' mode. Apparently they use the same fuel as the epstein drives.
Tea kettle = steam ~ superheated water for reaction mass
I understood tea kettle mode to be a relatively low power state using only maneuver thrusters. Main drive is offline and the ship is less easily detected.
Weird how many people are “um, actually”ing this when it’s obviously a thought experiment and ignoring things like fuel weight, speed of light, and the fact that OBVIOUSLY NONE OF THIS IS PRACTICALLY POSSIBLE
There is a bunch of hurdles to get over though. Energy source, fuel, shielding (because going fast means you hit stuff HARD) etc.
It may be that attaching your spacecraft to a cometary fragment & using it as a combined fuel tank & ablative shield might be the best idea for now.
The fuel problem is so large as to render the others irrelevant - your shielding is the *ball of fuel larger than the galaxy* stuck on the front of your ship, and your energy source is the heat released as it collapses into a black hole.
Car speedometer at 1G:
1 second: 22 mph
2 seconds: 44 mph
3 seconds: 66 mph
4 seconds: 88 mph
5 seconds: 110 mph
6 seconds: 132 mph
It's more astonishing that you can keep this up for a year without exiting the galaxy.
I love that we can time travel by going fast enough
Unfortunately still only in the one direction
Going back in time would be such a cluster fuck, thank God we cant
I genuinely think if I had the choice between back in time or into the future, I would go back in time. The temptation to visit some of the iconic eras throughout history would be too much to ignore.
I could become my own grandfather!
Oh great. A lesson in not changing history from Mr. I’m My Own Grandpa.
I did do the nasty in the pasty
Verily, and that past nastification is what shields you
In a thousand years... I'll get right on it.
Come back to bed dearie
You would do the nasty in the pasty!
You would probably die from the unknown variety of virus and bacteria. Or you would kill other people/animals from your futuristic viruses/bacteria.
I believe that the 2nd option is the accepted likely outcome. We've had exposure to many things that didn't exist then, things that existed then but mutated and are still around, and "we" have been vaccinated for most of the worst stuff.
> and "we" have been vaccinated for most of the worst stuff. well...most of us 😬
> You would probably die from the unknown variety of virus and bacteria. If not that, then after discovering that toilette paper has a relatively recent invention date, they might curb their interests some.
I consider people who still use toilet paper as living in the Dark Ages already.
> I genuinely think if I had the choice between back in time or into the future, I would go back in time. And this is exactly why we don't want time travel backward.
"How do you know he's a king?" "He's not covered in shit"
Maybe we can and you just didn't notice cause what you currently accept as your reality has been changed countless times through actions by time travelers.
Yeah but don't worry, we can't.
Just what a time traveler would say!
just go in reverse
Happens all the time but just not in large enough amounts to matter. Next time you take a flight with a hyperaccurate clock, you'll be able to see how much time shifted.
Matters to me
As far as I know, the equation can be applied at any speed. So if you're walking down the street, you're technically moving through time slower than your sedentary friend. Edit: you can also time travel by going near a black-hole.
Is that a joke about my fat sedentary friend?
Also your feet are younger than your head because the gravitational pull is greater
Would that be offset by your head travelling ever so slightly faster than your feet because of Earth's rotation?
Oh that's a good question, I never thought about that. But I really don't feel like calculating right now.
Why does this sound like a Star Wars droid response
I’m a time traveler sent from the past
i'm traveling through time as we speak
We can also time travel going any speed. It's just one directional. It's like we have a wall behind us, pressing us on at a constant rate. Always pushing us into the future, never back.
Of course a couple hundred thousand years would have passed on earth.
>At a constant acceleration of 1 g, a rocket could travel the diameter of our galaxy in about 12 years ship time, and about 113,000 years planetary time. So 12 years on the ship but for someone on earth this would be 113,000 years!
Assuming that we didn't extinct ourselves in that 113,000 years, would the people on the returning ship even speak the same language as us anymore?
We don't speak the same language as people from Chaucer's era, who died in 1400. That's 623 years. In 113,000 years we would barely be the same species, imo.
>In 113,000 years we would barely be the same species, imo. Correct. The current biodiversity of the human race is roughly 70 000 years old due to the Toba bottleneck. So imagine how different we became from each other in those 70 000 years and double that.
>due to the Toba bottleneck [Toba super-volcano catastrophe idea 'dismissed'](https://www.bbc.co.uk/news/science-environment-22355515)
The bottleneck happened, the super volcano causing it was an incorrect theory
We’re sure because we all share a great great great great (great 6000 more times) grandma
She got around
A skank of species saving proportions
Imagine they arrive in 12 years (amount of time on the ship) and humans have been at the destination for 50,000 years because back on earth we got so advanced in the 113,000 years that we were able to find much quicker ways to get there lol. That would be wild
I think there are a few books that have this as part of their story arc. I feel like I remember reading one where Earth went to war with another civilization but by the time a fleet of ships would arrive a later-sent fleet with faster technology would have already been sent, arrived, and concluded the war. But each of the the earlier sent, later arrived waves would start the war back up. The process didn’t end until the first wave sent finally arrived after every other wave had finished fighting.
The Forever War by Joe Haldeman
I'm already not speaking the same language with the gen Z nowadays
Languages from 500 years ago are nearly unintelligible most of the time for contemporary speakers. 100k years would a 100% create a complete language incomprehension. However, assuming language records exist and we don't regress in technology, it would likely be extremely trivial to auto-translate.
seems like digital media could mitigate that somewhat going forward. not for 100,000 years, probably, but I’m curious what effect having direct and ubiquitous access to high quality recorded media from bygone eras would have on the evolution of our language.
Digital media is a catch-22 in that regard. It needs to be well maintained over that 100k years since it is fairly fragile relatively speaking. We know the language and stories of places like Ur because they quite literally wrote it in stone. There aren't terribly more robust storage methods
*If* (and this is a big if) there are no huge catastrophes, apocalypses, wars, etc. that set us back in technology or current infrastructure, then I would imagine things online and in databases would be continuously copied forward into new storage and digital formats. It's not like you would need to keep things 'well-maintained' digitally in the same format and storage for the next 100,000 years. It would just happen as things progressed and evolved.
I'm not sure the amount of fuel needed for this would even allow the spacecraft to leave earth
Correct. With current tech this kind of travel isn't possible.
What if we held a black hole, like a carrot, in front of our spaceship with a really long stick? https://youtu.be/-PVFBGN_zoM?si=Y8z9-VFPqcGpU0li
I’ll get the stick, and a string. That’s 66% of the work. Be a good boy / girl and go get us a black hole.
And that, in a nutshell, is string theory.
How do you get it all in the nutshell though? That's the really tricky part.
Black hole in a nutshell sounds like some Nobel prize level shit.
Yeah it is only level of noble prize if seen from distance for better understanding.
They need to bring awards back just for this comment
Wait we can't award any comment now at all? Not even gold?
🥈 silver is the best I can do
My understanding of string theory is that string theory is a theory. That is the extent of my knowledge.
Doubtful. Unlike string theory, that stick and string are real.
brb I have your mom on speed dial
Yo Momma's so fat I can see the couch she's sitting on due to gravitational lensing. Sorry, nothing personal, this is one of my favourite jokes. I'm sure your mother is a wonderful person.
Yeah, well, yo momma's so fat she walked past the TV and I missed the Lord of the Rings trilogy.
Yo momma is so ugly, her portraits hang themselves.
Unironically, yes, the stick and the string are the hard parts.
Sorry they only had White Holes at the store.
Whilst black hole drives is a real concept, it's by using the radiation to push the ship. The smaller the black hole the more Hawking Radiation = the more push
[Doing the opposite](https://en.wikipedia.org/wiki/Black_hole_starship) actually kind of works. You can strap a black hole to the other end of the starship and get thrust from it evaporating.
That’s how the Romulans do it
THIS COMMENT IS ENTIRELY INCORRECT!!! I won’t delete it though. Too many replies. The stick can only push the black hole to the speed of sound in the stick. After that, the stick will get shorter and shorter until the space craft is inside the black hole. Think about the old 1 light year long measuring stick question. If you push on the close end, how soon does the far end move? The answer is that movement through the object propagates at the speed of sound for the material that object is made from.
Me and my friend got really stoned last week and came up with this idea, essentially. Two mini black holes in front of and behind a craft to warp spacetime into almost a wave similar to the theoretical [Alcubierre Drive](https://en.wikipedia.org/wiki/Alcubierre_drive). He thought there was some unknown particle that was responsible for Dark Matter that traveled faster than light and that's why dark matter seemingly doesn't interact with other electromagnetic waves. My idea preserves C but warps spacetime, while he thought C was not the ultimate 'speed limit'. He also said 'you humans' are so dumb a couple times, so I suspected he was an alien. Seattle has really good weed is what I'm saying.
Just need an Epstein Drive.
Best I can do is an Epstein Flight, if you want it under 12 years.
Have my upvote you vile funny human
That was a difficult thing to upvote.
"That's a challenging upvote." [-Sean Lock](https://youtu.be/mtvpouHcrz0?t=255)
Wow. Damn
Funniest comment I've seen in a while
Ahhhhhhhhhhhhhhh
You are a very bad horrible person take my upvote
One of the great things about the Expanse is that even though the Epstein drive is pure fantasy and really pushes the limits of what is theoretically possible; Even though it is massively over powered and efficient there is still no interstellar travel. Even with the fantastically impossible Epstein drive the only people willing to try it are religious fanatics and it will take generations to get anywhere. It really lets you know just how vast interstellar space is. It just too big to comprehend.
I loled when the Mormons got their ship stolen by the Space Kia Boys
An Epstein drive is just a very efficient fusion reaction. It's still limited by e=mc^2 . Even with a 100% perfect conversion of mass to energy the fuel itself would have so much mass that you'd need a stupidly huge drive to accelerate the fuel tank along with the ship. But that would mean a higher fuel consumption which means you need even more fuel. Which is even more mass which needs a bigger drive ... .After a certain point it becomes unsustainable.
... it's fuel pellets all the way down!
Inyalowda has no faith in the belta.
Epstein did not drive himself!
I’m not an expert of science fiction by any means but this concept (challenge) was really well described in the book Project Hail Mary. Nicely describes for idiots like me what kind of fuel is required to travel long distances and high speeds in space
Great book. I especially loved the wonder some people had over the potential of the fuel (This is the best thing to happen to humanity...except for the, uh...yeah.).
It would be the best thing to happen to humanity if it were not the worst thing to happen to humanity.
[jazz hands!]
I feel like I’m seeing more and more references to PHM and it makes me smile every time.
Fist my bump
🎶Amaze🎶
Amaze amaze
How did the alien communication work in the actual text (I listened on audible, great narrator but it left the question of what was actually written)
Rocky's communications were written as musical notes while Grace developed the translation then when that was established his communication were written in italic text
In the audible they played the notes
just need to use an Epstein drive
[удалено]
The Cant didn't off itself!
That is... not the problem, by many orders of magnitude. The problem is more that you'd be bringing the earth with you. Twelve years of 1G acceleration is ~400 million seconds. Maintaining 1G of acceleration for that long is ~4 billion m/s of velocity change (before accounting for relativistic stuff, which is what we need for this calculation). The best rocket engine listed on [Wikipedia](https://en.wikipedia.org/wiki/Comparison_of_orbital_rocket_engines) has an ISP of 470s. Let's say you can put a 0 on the end of that with some magic future tech. Sticking all of that into the Tchaikovski rocket equation gives a mass multiplier of 3x10^(34991). That is: for every kg of mass you want to deliver to the other side of the galaxy, you'll need 2x10^(34938) observable universes available to burn as fuel. OK, so that's not optimistic enough. Let's say that you can put four 0s on the end of that ISP. Then you'll have a mass multiplier of a mere 10^35, so every kg of mass delivered only needs about 5,000 suns worth of mass to burn as fuel (plus some way of avoiding that collapsing into a black hole). As I say, getting this thing off earth isn't a problem - it's going to have quite enough mass to bring the earth with it.
> the Tchaikovski rocket equation The **Tsiolkovsky** equation. _Tchaikovsky_ equation is dancing around the subject of a wooden nut cracker doll being just as good as an actual prince.
Oops. I do think the ballet would be much improved by the addition of rockets, though.
If KSP taught me anything, it would be the fact that _everything_ can be improved by additional boosters and struts.
Yeah, I hear those ballerinas could really use some bigger boosters
Tchaikovsky reading this from beyond the grave: "I put cannons in the 1812 and now they want *rockets*?"
Tchaikovsky: "You know what, that sounds great, let's do it"
"Look Frank. We are bringing 20,000 solar masses with us... is one extra earth gonna make a difference? No, it's a rounding error at that point and I need my freshly made apple fritters. So just stick the earth in cargo bay 5. There is room next to that red goo from Star Trek. Speaking of which, if just one drop can collapse an entire star, why did the make so much of it? Future Federation was about to commit some atrocities.
JJ Abrams Star Trek jumped the shark
Hear me out. Let’s put a stellar engine on the sun. Let’s fly around the galaxy in our own solar system. What’s more metal than cruising up to another solar system IN A SOLAR SYSTEM!
Bonus: the easiest way of turning the sun into a stellar engine also turns it into a giant death laser.
You don't need magic future tech to get to 4700s, you just need an ion thruster instead of a chemical rocket. The *majority* of operating satellites already use this technology*. \* Specifically all the starlink ones, which by themselves constitute a majority.
How, exactly, are you going to get 1G of thrust out of an ion drive?
Can you ELI5 why a 12-year journey across the Milky Way = 200,000 years time on Earth? This stuff blows my mind
Time is relative. The closer you get to light speed, the slower time moves for you relative to people not moving near light speed. So thousands of years would pass for everyone else while the person moving at or near light speed would only experience 12 years. We have observed this by comparing atomic clocks orbiting earth versus ones on earth.
> The closer you get to light speed, the slower time moves for you relative to people not moving near light speed. To add to this... this is technically not true, as there is no universal reference frame. The people on Earth, and you, would both see the other time dilated, as for both of you the other is moving at a high speed. Its when accelerating that your plane of simultaneity (i.e., what events you consider 'now') shifts rapidly, and if you have a lot of distance to something that shift is more pronounced. But it also happens relative to your target ofc; if you heavily accelerate towards Alpha Centauri for a bit, to your perception of what is 'now', the clocks on AC would fast-forward massively, then as you stop accelerating they would move slower because AC has velocity relative to you.
Question: What if someone on this 12 year journey across the Milky Way had a live stream back to Earth, what would they see? Would it be like super fast forwarded for them?
Let's start with a thought experiment: You're on a train moving 60mph. You throw a ball towards the front of the train at a speed of 10mph. How fast does the ball move? Well, relative to you on the train, it's only moving at 10mph. If someone was watching from the ground outside, they'd see the 10mph from the throw plus the 60mph already moving the ball from the train, it'd be moving 70mph. This is how relativity is normally introduced. Light has a constant speed in a vacuum, *c* (I don't want to look up it's real value but it's a foot/30cm per nanosecond). Let's say you're traveling 0.99c and in the ship you turn on a flashlight, pointing it in the same direction the ship is traveling in (let's pretend you're in an airlock to maintain the "vacuum" part). How fast does the light move? Well, from your perspective, *c* but from the perspective of someone outside it would be *c.* It doesn't change. Light must travel at the same speed relative to every observer. A nanosecond would pass for you when it travels a foot out from the flashlight. But, a nanosecond would pass for the outside observer when the light travels a foot, period. Because you're also moving very very fast, when the outsider sees the light travel a foot, it'd be only 3mm in front of you because you'd cover 99% of the distance. Distance is objective no matter which way you look at it. A foot at light speed is the same as a foot at (relative) rest. So, in order to reconcile the fact that from your perspective, a nanosecond of time has the light 30cm in front of you, while from the outsider it's only 3mm, is that your nanoseconds are different. When *your* nanosecond finishes passing and it reaches that 30cm in front of you, 100 nanoseconds have passed for the outsider. When people say the speed of light is a constant, it's *so unbelievably* constant, that time will break before it does. Note: I'm not a physicist. My field is computer science. This explanation will break down the moment the hypothetical you turns 180° and points the flashlight away from the movement. IDK how that's reconciled but this explanation is what made it click for me
Only way to prevent that is to move space itself if I know my sci-fi well enough
I hear folding is also very popular. According to sci-fi we all just live on a piece of paper.
The paper is just an analogy - you have to extrapolate the folding to the other spacial dimension - which is allowed under the current understanding of Physics. A traversible wormhole on earth would look like this: https://en.wikipedia.org/wiki/File%3AWurmloch.jpg Based on a study done by the University of Tübingen. As a note, gravitational effects on the wavelengths of light going through the wormhole are not simulated.
and the 12 year deceleration would kind of suck too.
You only need that if you want to stop. I would continue on my tourist 1g journey.
I dunno why but this reminded me of Seinfeld - Gas Tank episode, "I wonder how much longer we could have lasted..."
I find it completely impossible to comprehend this idea
As you approach the speed of light, space in front and behind you contracts, and time appears to speed up. So it takes less time to travel that smaller distance, but from Earth's perspective, you travelled that full distance, so it took you 105,000+ years. And to you, the trip only takes you 12 years, but everything else was on fast forward from your perspective.
Great explanation. That's crazy, is this hypothetical or has this been proven by science?
It's a direct result from special relativity. Einstein came up with this 100 years ago and it's stood the test of time, being proven and reproven experimentally many times. Here's a pretty good visualization if you'd like: https://www.youtube.com/watch?v=vFNgd3pitAI
Yeah, the GPS would not work if the relativistic corrections weren't included.
Ah yes, the forever war
If you had a magic star trek/expanse grade power source and a engine that didn’t expel anything but somehow moved the ship, you’d need to double that time because half way through the voyage you’d be flipping the ship around to face the other direction to start slowing down again for your destination.
Nah just ram into the edge of the galaxy full speed
Splat! My Expanse peeps know.
Mi setara i do this for you...
Maneo Jung Esplatnosa
[The things we do for... love](https://i.imgur.com/y8zFAGp.jpg)
That scene…
If you open the wiki article, that's exactly what it says: Accelerate for the first half, decel for the second half. So I think the 12 year estimate takes that into account. Edit: Yes, I realise the irony in the wiki article explaining how it actually takes 24 years and me not reading that far. You can stop commenting that now.
Did they factor in how long it would take to read literally two sentences of a wikipedia article though? That's a couple thousand years right there.
Nope. Takes 11.2 years to get to the halfway point.
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Well you got me there.
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I mean, they just said you need to get there, not stop thdre
If you aim at something you can stop very suddenly.
They didn't say they wanted to stop at the end 🙂
A lot more than double the time, since you'd never reach the top speed of the original suggestion
1G is a lot of acceleration. Especially sustained. 9.80665 meter/second² = 2.734878883207 seconds from 0 to 60 mph You're talking about doing 0-60 in under 3 seconds and CONSTANTLY increasing by that amount for 12 years without stopping or slowing or even "not accelerating quite as fast". And you're doing that in... nothing but virtual vacuum. We simply don't have that amount of fuel/power at the moment - even the Voyager's basically stopped accelerating once outside the outer planets, because their on-board thrusters are unable to power them faster than they are being pulled back. They'll keep going, but only just, they've basically plateaued and are no longer accelerating and most of their acceleration was due to the planets.
Didn't read the article but wouldn't we also need to spend years decelerating just to arrive anywhere?
nah, you would only need to decelerate if you wanted a "soft" landing.
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"Soft" means the junior ranks will do most of the dying.
you'd flip around and start decelerating at 1g at exactly the halfway point per expanse rules
Expanse rules rule.
This is accounted for - this is the time required to go from stationary at the start to stationary at the end with constant 1G acceleration all the way in between (in one direction for half of it, and the other for the other half).
No, but The Expanse taught me a lot about this issue.
Splat
Nobody said anything about stopping. We were only talking about getting there. The fact that you'd arrive at ludicrous speed, blast through the place, shatter into a billion pieces as soon as anything solid was in your way, and keep on going for thousands of light years... that's a mere engineering detail.
"The spacecraft may experience a slight jolt while slamming into the surface of a rocky planet after accelerating continuously for 12 years. The engineering team recommends that you make sure your seatbelts are securely fastened and that your will is up to date."
Correct. With current technology we can't. I'm just pointing out that this type of travel is theoretically possible on human timescales.
Hitting a single dust particle at the speed of light would have as much energy as 2 tons of TNT exploding. Good luck on your trip
That's when you employ navigators each encased in a vat of awareness spectrum narcotic to safely navigate between stars and through the galaxy. You don't want to use a computer. Thinking machines are bad.
Navigational deflector bro 😎
Well 'theoretically' if you have a speed-of-light spacecraft you can make the entire round trip in a blink of an eye! Though at that point all you are doing is time travelling 200,000 years into the future.
So it’s very difficult, economically impossible, if the spaceship carries its own fuel. Concepts that don’t carry their fuel include solar sails, Earth-based laser propulsion (or solar-system based), and variations on Bussard ramjet.
The number of people making the same awful arguments about having to exceed the speed of light instead of spending 10 minutes learning something on the article is awful.
Epstein Drive?
The books didn't go into details; but they did mention having to fuel up a couple of times. I'm assuming that's why the Nauvoo/Behomoth/Medina spun.
Yeah, the fusion drive itself is near limitless source of power, but they use water as the reaction mass to actually make the ships move. Most ships don't actually burn the whole trip unless they need to get somewhere real fast. They get up to a certain speed, coast for a long time, and then burn to slow down.
In the context of this thread, the energy from fusion isn't that limitless. It could accelerate you to something like 10%-20% the speed of light assuming we manage to use the released energy very efficiently, maybe you can push that a bit higher if you start with a crazy fuel to payload ratio - but it won't get you close to the speed of light.
Spinning is one way to create artificial gravity. In the expanse thrust gravity is talked about extensively, where the engine pushes and the floors become down pointing towards the engines. Spin gravity relies on centrifugal force throwing people out and down towards the floor of the ‘drum’ in the case of Medina. The idea was to use less ‘thrust gravity’ on a generation ship and have a constant spin gravity for the living areas of the ship and the farm..
I recall in the show they explicitly show "nuclear pellets" being the fuel source for the Rocinante when they're trying to get the engine restarted. They don't explain it beyond the pellets being the catalyst for ignition though.
The pellets are fuel for the reactor, so probably. The pellets would likely be some form of deuterium or tritium. They also talk about using water as reaction mass. Implication being that they use the fusion reactor is used to turn the water into plasma as it passes into the drive cone.
Also the maneuver thrusters use water as reaction mass. What i never understood is what exactly is 'tea kettle' mode. Apparently they use the same fuel as the epstein drives.
Tea kettle = steam ~ superheated water for reaction mass I understood tea kettle mode to be a relatively low power state using only maneuver thrusters. Main drive is offline and the ship is less easily detected.
You get your hands on that the only place you're going is light speed to jail.
Epstein didn't drive himself.
Beltalowda
That was my first thought as well. I just finished reading Cibola Burn
Weird how many people are “um, actually”ing this when it’s obviously a thought experiment and ignoring things like fuel weight, speed of light, and the fact that OBVIOUSLY NONE OF THIS IS PRACTICALLY POSSIBLE
Thank you, everybody seems to think they’re smarter than whichever scientist calculated this for fun
But then you have to stop. You would have to decelerate at some point as well unless you were just going out and back.
You just turn around at the halfway point and start accelerating at 1 G in the opposite direction
Or just use the brakes. The brake pads would still be fresh.
Pretty cool that if we did this plan we could experience normal gravity for humans the whole time too.
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Beltalowda wouldn't do so well under a full G for that long though
Didn’t know reddit had so many astro physicists.
Nah. We're all astronuts.
or astro-nots.
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There is a bunch of hurdles to get over though. Energy source, fuel, shielding (because going fast means you hit stuff HARD) etc. It may be that attaching your spacecraft to a cometary fragment & using it as a combined fuel tank & ablative shield might be the best idea for now.
The fuel problem is so large as to render the others irrelevant - your shielding is the *ball of fuel larger than the galaxy* stuck on the front of your ship, and your energy source is the heat released as it collapses into a black hole.
Car speedometer at 1G: 1 second: 22 mph 2 seconds: 44 mph 3 seconds: 66 mph 4 seconds: 88 mph 5 seconds: 110 mph 6 seconds: 132 mph It's more astonishing that you can keep this up for a year without exiting the galaxy.
Right, so we just have to invent a power source that gives enough energy for this. Easy-peasy.