7 ms·

I never thought of c being a real problem to space travel. Sure, on the timescale of our lives c is sloooow because moving between stars automatically necessita

I never thought of c being a real problem to space travel. Sure, on the timescale of our lives c is sloooow because moving between stars automatically necessitates a multi-generational approach and/or huge amount of resources. The big problem however, is that we have no place to go. We are tied to earth. Our bodies are made for a specific gravity constant, specific distance from a specific star, specific atmospheric mix of gases, a pre-existing DNA-based fauna and flora, etc. Quite simply, when it comes to colonization: there's no place like home. Every other place sucks for our bodies. Once we achieve the singularity(tm) and upload our consciousness (or get replaced by AI), we can turn down the clock speed on the matrix (say turn 1,000,000 real years into 1 matrix year), and like magic c stops being a practical limitation. Sending message (or travelling) from one side of the galaxy to another would take a 'matrix month' .. turn the clock down even further and you can make galactic communication instantaneous.

rwcarlsen 8y ago
You could actually reach almost anywhere in the galaxy within a single human lifetime (the traveler's lifetime that is) using only 1-G constant acceleration: https://en.wikipedia.org/wiki/Space_travel_using_constant_acceleration https://en.wikipedia.org/wiki/Space_travel_using_constant_ac... No FTL required. We just need to figure out how to use propellant efficiently enough among a few other slightly difficult challenges.
- macspoofing 8y ago
  The challenge is still communication (it's going to take you 100k years to send a message from one end to another) and synchronization (it took you 60 years to get to your destination, but hundreds of thousands of years have passed for your peers)
  - TheSpiceIsLife 8y ago
    This can be solved by simply not communicating.
    - macspoofing 8y ago
      That's true. Or just dealing with the time-lag.
- magduf 8y ago
  The problem with this is that, by the time you get anywhere, a ridiculous amount of time has passed back on Earth, and also on the destination planet (since the reference frame for the other planet is very close to Earth's). So if you travel around to hundreds of planets, pretty soon all the stars have gone nova and you're nearing the heat-death of the universe, even though you may not have aged much.
  - rwcarlsen 8y ago
    Minor concerns.
    - dorgo 8y ago
      Limiting believes
  - state_less 8y ago
    If we make it for another hundred or few thousand years more without killing ourselves, I'd imagine we might be able to shoot self replicating ships out at near C, then beam copies of ourselves to each ship, expanding out everywhere at near C. We might be able to be everywhere. I imagine we could 'live inside' a projected VR world that looks like earth or some other massive online world unless we wanted to go out camping at whatever planet we were orbiting.
    - saiya-jin 8y ago
      copy of me ain't me but another human, i wouldn't consider it much closer compared ie to my best friend
      - state_less 8y ago
        Consider an arm that has 'fallen asleep' or placed under local anesthetic. It feels foreign, but you take care of it still as if it were your own. One has to simply extend their idea of themselves outside of what their neurons are directly touching to see the linkage between another human and themselves. Here is a case where two people are brought in more direct contact, which seems to me to hold the door open for future possibilities. It makes it easier to see how two might merge, at least in a rough accidental sort of way. https://kottke.org/17/11/these-conjoined-twins-can-share-each-others-thoughts-vision https://kottke.org/17/11/these-conjoined-twins-can-share-eac... https://www.nytimes.com/2011/05/29/magazine/could-conjoined-twins-share-a-mind.html https://www.nytimes.com/2011/05/29/magazine/could-conjoined-... Have a good one.
- mortenjorck 8y ago
  Are you familiar with The Expanse? Based on the way G-forces are presented in the TV adaptation (I presume the book does something similar), I take it the Epstein Drive is supposed to be a constant-acceleration design, which in the story is limited to intra-solar travel (though presumably the generation ship Nauvoo was designed to use it for interstellar). I mention this because your comment made me think: Even staying within the solar system, how short would a trip between Earth and Mars have to be to start to pose relativistic problems? I wonder at what point frequent travelers would start aging noticeably more slowly. (If this is dealt with in the books, now I’ll really have to read them.)
  - wyattpeak 8y ago
    At relativistic speeds, Mars and Earth are ludicrously close - between 4 and 20 minutes apart at light speed. So even travelling arbitrarily close to the speed of light, at the greatest possible distance, you could only gain 20 minutes on the folks back home per trip. A round trip weekly at average distance (just going with 12mins/trip because the details get complicated), 48 weeks a year for 40 years would leave you just over a month younger than those who stay put.
- TheSpiceIsLife 8y ago
  And, if you can work out how to do 1G acceleration, you can probably work out how to 2 or 3 or 4G acceleration. That's going to get uncomfortable, but most people should be able to cope with 2 or 3G acceleration for short periods.
- anonytrary 8y ago
  > I never thought of c being a real problem to space travel. > We just need to figure out how to use propellant efficiently enough among a few other slightly difficult challenges Both of these sentiments are pretty common misconceptions I've seen on HN. First, if c was infinite, the energy required to accelerate a constant amount would grow quadratically. This alone is a tough problem. Maybe we could "just" solve it. On the other hand, if c was finite, the energy required to accelerate would grow exponentially. This is more than a "slightly difficult" problem.
WalterBright 8y ago
With genetic engineering, we can adapt our bodies to other situations.
- macspoofing 8y ago
  I suspect there are very real limits as to what you can do with DNA. Regardless, I'm not sure if splitting humanity into many other species is something you want to do. And you still haven't solved any issue with distance communication and different reference planes.
  - WalterBright 8y ago
    I doubt people could be perfectly adapted by gene engineering, but one could reduce the life support requirements significantly. For example, shorter people could probably deal with heavier gravity better.
    - ordu 8y ago
      And they are cheaper to accelerate, because of lower mass.
marcosdumay 8y ago
Any finite speed limit ultimately imposes a O(t^2) rate of growth into a civilization, while the natural rate of growth of a biological system is O(e^t). The universal speed limit dictates how much of the Universe humans (or whatever comes after us) can ever visit, because of the Hubble constant. A universal speed limit limits the size of a computer that can still have coherent "thoughts".
- macspoofing 8y ago
  OK. How is this fact relevant exactly in this case?
- perl4ever 8y ago
  Why t^2 and not t^3?
  - haneefmubarak 8y ago
    IIRC, it's because of surface area and not volume.
  - marcosdumay 8y ago
    Because it's a rate of growth, not total size. Or, if you are more geometrically inclined, because growth happens over the surface, the volume is already conquered stuff.
- p1mrx 8y ago
  One could speculate (based on the anthropic principle) that this speed limit is one of the reasons we're still alive. It might protect us from runaway von Neumann probes, false vacuum bubbles, and similar events.
- anonytrary 8y ago
  > while the natural rate of growth of a biological system is O(e^t). The theoretical growth rate; in practice this is impossible to keep up due to biological resource limitations. > The universal speed limit dictates how much of the Universe humans (or whatever comes after us) can ever visit, because of the Hubble constant. So unless every point in space was an "agar plate for humans", ready to serve us and house our breeding, we'd run into resource limitations far before any theoretical maximum due to finite c and expansion.
dmd 8y ago
You should read "Lockstep". https://smile.amazon.com/dp/B00H6E6ATI/ https://smile.amazon.com/dp/B00H6E6ATI/
inamberclad 8y ago
> Every other place sucks for our bodies. The ones we know. Earth-like planets are hard to spot from very far away.
pasquinelli 8y ago
i always wonder what people mean by uploading consciousness. like, faster than light travel, i know what it means even if it's not possible, but to upload my consciousness... what, in theory, is supposed to happen? what does it happen to?
ringbugger 8y ago
I have been to burger king a little too often lately and I would be totally fine with a 0.75g planet now. The "life corridor" is certainly very narrow. But I am sure there are at least some places. Maybe we find a world near a smaller red dwarf, which will last for trillions of years. Maybe we also don't make that planet uninhabitable in a few thousand years, for once.
tshanmu 8y ago
this sounds a lot like Hindu philiosophy ;)

rwcarlsen 8y ago

You could actually reach almost anywhere in the galaxy within a single human lifetime (the traveler's lifetime that is) using only 1-G constant acceleration: https://en.wikipedia.org/wiki/Space_travel_using_constant_acceleration https://en.wikipedia.org/wiki/Space_travel_using_constant_ac... No FTL required. We just need to figure out how to use propellant efficiently enough among a few other slightly difficult challenges.

macspoofing 8y ago
The challenge is still communication (it's going to take you 100k years to send a message from one end to another) and synchronization (it took you 60 years to get to your destination, but hundreds of thousands of years have passed for your peers)
- TheSpiceIsLife 8y ago
  This can be solved by simply not communicating.
  - macspoofing 8y ago
    That's true. Or just dealing with the time-lag.
magduf 8y ago
The problem with this is that, by the time you get anywhere, a ridiculous amount of time has passed back on Earth, and also on the destination planet (since the reference frame for the other planet is very close to Earth's). So if you travel around to hundreds of planets, pretty soon all the stars have gone nova and you're nearing the heat-death of the universe, even though you may not have aged much.
- rwcarlsen 8y ago
  Minor concerns.
  - dorgo 8y ago
    Limiting believes
- state_less 8y ago
  If we make it for another hundred or few thousand years more without killing ourselves, I'd imagine we might be able to shoot self replicating ships out at near C, then beam copies of ourselves to each ship, expanding out everywhere at near C. We might be able to be everywhere. I imagine we could 'live inside' a projected VR world that looks like earth or some other massive online world unless we wanted to go out camping at whatever planet we were orbiting.
  - saiya-jin 8y ago
    copy of me ain't me but another human, i wouldn't consider it much closer compared ie to my best friend
    - state_less 8y ago
      Consider an arm that has 'fallen asleep' or placed under local anesthetic. It feels foreign, but you take care of it still as if it were your own. One has to simply extend their idea of themselves outside of what their neurons are directly touching to see the linkage between another human and themselves. Here is a case where two people are brought in more direct contact, which seems to me to hold the door open for future possibilities. It makes it easier to see how two might merge, at least in a rough accidental sort of way. https://kottke.org/17/11/these-conjoined-twins-can-share-each-others-thoughts-vision https://kottke.org/17/11/these-conjoined-twins-can-share-eac... https://www.nytimes.com/2011/05/29/magazine/could-conjoined-twins-share-a-mind.html https://www.nytimes.com/2011/05/29/magazine/could-conjoined-... Have a good one.
mortenjorck 8y ago
Are you familiar with The Expanse? Based on the way G-forces are presented in the TV adaptation (I presume the book does something similar), I take it the Epstein Drive is supposed to be a constant-acceleration design, which in the story is limited to intra-solar travel (though presumably the generation ship Nauvoo was designed to use it for interstellar). I mention this because your comment made me think: Even staying within the solar system, how short would a trip between Earth and Mars have to be to start to pose relativistic problems? I wonder at what point frequent travelers would start aging noticeably more slowly. (If this is dealt with in the books, now I’ll really have to read them.)
- wyattpeak 8y ago
  At relativistic speeds, Mars and Earth are ludicrously close - between 4 and 20 minutes apart at light speed. So even travelling arbitrarily close to the speed of light, at the greatest possible distance, you could only gain 20 minutes on the folks back home per trip. A round trip weekly at average distance (just going with 12mins/trip because the details get complicated), 48 weeks a year for 40 years would leave you just over a month younger than those who stay put.
TheSpiceIsLife 8y ago
And, if you can work out how to do 1G acceleration, you can probably work out how to 2 or 3 or 4G acceleration. That's going to get uncomfortable, but most people should be able to cope with 2 or 3G acceleration for short periods.
anonytrary 8y ago
> I never thought of c being a real problem to space travel. > We just need to figure out how to use propellant efficiently enough among a few other slightly difficult challenges Both of these sentiments are pretty common misconceptions I've seen on HN. First, if c was infinite, the energy required to accelerate a constant amount would grow quadratically. This alone is a tough problem. Maybe we could "just" solve it. On the other hand, if c was finite, the energy required to accelerate would grow exponentially. This is more than a "slightly difficult" problem.

WalterBright 8y ago

With genetic engineering, we can adapt our bodies to other situations.

macspoofing 8y ago
I suspect there are very real limits as to what you can do with DNA. Regardless, I'm not sure if splitting humanity into many other species is something you want to do. And you still haven't solved any issue with distance communication and different reference planes.
- WalterBright 8y ago
  I doubt people could be perfectly adapted by gene engineering, but one could reduce the life support requirements significantly. For example, shorter people could probably deal with heavier gravity better.
  - ordu 8y ago
    And they are cheaper to accelerate, because of lower mass.

marcosdumay 8y ago

Any finite speed limit ultimately imposes a O(t^2) rate of growth into a civilization, while the natural rate of growth of a biological system is O(e^t). The universal speed limit dictates how much of the Universe humans (or whatever comes after us) can ever visit, because of the Hubble constant. A universal speed limit limits the size of a computer that can still have coherent "thoughts".

macspoofing 8y ago
OK. How is this fact relevant exactly in this case?
perl4ever 8y ago
Why t^2 and not t^3?
- haneefmubarak 8y ago
  IIRC, it's because of surface area and not volume.
- marcosdumay 8y ago
  Because it's a rate of growth, not total size. Or, if you are more geometrically inclined, because growth happens over the surface, the volume is already conquered stuff.
p1mrx 8y ago
One could speculate (based on the anthropic principle) that this speed limit is one of the reasons we're still alive. It might protect us from runaway von Neumann probes, false vacuum bubbles, and similar events.
anonytrary 8y ago
> while the natural rate of growth of a biological system is O(e^t). The theoretical growth rate; in practice this is impossible to keep up due to biological resource limitations. > The universal speed limit dictates how much of the Universe humans (or whatever comes after us) can ever visit, because of the Hubble constant. So unless every point in space was an "agar plate for humans", ready to serve us and house our breeding, we'd run into resource limitations far before any theoretical maximum due to finite c and expansion.

dmd 8y ago

You should read "Lockstep". https://smile.amazon.com/dp/B00H6E6ATI/ https://smile.amazon.com/dp/B00H6E6ATI/

inamberclad 8y ago

> Every other place sucks for our bodies. The ones we know. Earth-like planets are hard to spot from very far away.

pasquinelli 8y ago

i always wonder what people mean by uploading consciousness. like, faster than light travel, i know what it means even if it's not possible, but to upload my consciousness... what, in theory, is supposed to happen? what does it happen to?

ringbugger 8y ago

I have been to burger king a little too often lately and I would be totally fine with a 0.75g planet now. The "life corridor" is certainly very narrow. But I am sure there are at least some places. Maybe we find a world near a smaller red dwarf, which will last for trillions of years. Maybe we also don't make that planet uninhabitable in a few thousand years, for once.

tshanmu 8y ago

this sounds a lot like Hindu philiosophy ;)