5 ms·

"Interstellar" travel will likely never happen. The distances involved are so vast as to boggle the mind. Private ventures offer the promise of opening up spa

"Interstellar" travel will likely never happen. The distances involved are so vast as to boggle the mind. Private ventures offer the promise of opening up space, but they won't break physics. Like it or not, we as a species are stuck here, likely forever.

ktizo 15y ago
Never is a much longer time than the distances involved.
FD3SA 15y ago
All well and good...assuming that human life spans cannot be extended significantly. Fortunately, there are some very smart people who disagree with that assumption [1][2]. 1. http://www.sens.org/ http://www.sens.org/ 2. http://halcyonmolecular.com/ http://halcyonmolecular.com/
sien 15y ago
With known physics we could do interstellar travel: http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)#Interstellar_missions http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsi... It would be unbelievably expensive right now however. But give it a century or two and things could well change. If a space elevator was built it would slash the cost.
drewblaisdell 15y ago
"Never happen" =/= "never in our lifetime"
InclinedPlane 15y ago
Such pessimism has nothing to do with fundamental limitations. Once humanity has had perhaps centuries of experience with orbital habitats then the idea of a large "generational" starship won't seem so unlikely. With functional fusion power and highly efficient recycling systems the ability to have an interstellar city ship which spends hundreds or thousands of years isolated from the rest of civilization may not seem so unlikely. Also consider that interstellar space holds far more destinations than we have currently cataloged. Begin with a colony near a comet out in the deepths of the Oort cloud. Then make a hop to another comet, free roaming planet, brown dwarf, or red dwarf that is very likely to be within a single light year distant. At each destination repair, refuel, resupply and move on. In a time span of only a fraction of the age of human civilization significant populations of humans will spread out from our Solar System and diffuse through interstellar space.
hahainternet 15y ago
This is remarkably negative. There are a number of ways to explore without having to break physics. Constant 1g acceleration makes nearby galaxies accessible, nevermind nearby solar systems. Returning from exploration? Reporting results? That isn't going to happen. Colonizing the universe? There's nothing at all stopping it in physical law.
- drostie 15y ago
  Constant 1g acceleration makes nearby galaxies accessible, nevermind nearby solar systems. "Break physics" is relative -- things which can be allowed by the laws of physics can be so humanly implausible as to be useless to discuss. I mean, let me just be totally clear about this. In relativity, to get your time dilation factor γ up, you need a lot of kinetic energy K. How much? Well E = γ m c² = m c² + K, so K = (γ − 1) m c². If you wanted to go to the nearest galaxy -- which is 25,000 light years away on the other side of the Milky Way -- and you wanted to do it with any sort of vehicle in 25 years -- you would have to take along about 1000 times the mass of your vehicle as fuel. More importantly, whatever fuel you're using to accelerate you're also using to decelerate, so you actually need 1,000,000x fuel to start with, to get your 1,000x fuel up to speed for most of the journey. So your 10^5 kg shuttle orbiter would need to come with 10^8 kg slowdown fuel. That's what we're sending around, you've got to build the Great Pyramid at Giza out of antimatter and find a way to carry it with you, just to get the shuttle to do this in a reasonable time. Now c² is about 10^17 J/kg so we need about 10^25 J to slow down, and to send this would require 10^28 J. For perspective, our largest nuclear blasts (Tsar Bomba's 50 megaton yield) are 2 * 10^17 J, so you'd need fifty million of those to launch. Or you could just carry the US with you, that has an annual power consumption of 10^22 J -- wait, make that a million copies of the United States, before you could launch. Of course, antimatter is unstable and you might want to carry the Tsar Bomba around as a massive fuel source instead, but the Tsar Bomba actually only carried an energy yield of around 10^-4 m c², so you would need to have 10,000 times more mass (10 million space shuttles to decelerate your one) if you wanted to do it with nuclear bombs.
  - hahainternet 15y ago
    The reason I mentioned no returning of data is that it obviously is not plausible within 25 years. I appreciate you doing the mathematics, but you don't base it on the 1g acceleration I mentioned, as far as I can tell.
dodo53 15y ago
I think what it will take is mind uploading. Once a sentience can suspend until interesting circumstances are detected, I'm sure some wealthy people will go decide to go off explore the galaxy / take a punt on van neuman machine mining.

ktizo 15y ago

Never is a much longer time than the distances involved.

FD3SA 15y ago

All well and good...assuming that human life spans cannot be extended significantly. Fortunately, there are some very smart people who disagree with that assumption [1][2]. 1. http://www.sens.org/ http://www.sens.org/ 2. http://halcyonmolecular.com/ http://halcyonmolecular.com/

sien 15y ago

With known physics we could do interstellar travel: http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)#Interstellar_missions http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsi... It would be unbelievably expensive right now however. But give it a century or two and things could well change. If a space elevator was built it would slash the cost.

drewblaisdell 15y ago

"Never happen" =/= "never in our lifetime"

InclinedPlane 15y ago

Such pessimism has nothing to do with fundamental limitations. Once humanity has had perhaps centuries of experience with orbital habitats then the idea of a large "generational" starship won't seem so unlikely. With functional fusion power and highly efficient recycling systems the ability to have an interstellar city ship which spends hundreds or thousands of years isolated from the rest of civilization may not seem so unlikely. Also consider that interstellar space holds far more destinations than we have currently cataloged. Begin with a colony near a comet out in the deepths of the Oort cloud. Then make a hop to another comet, free roaming planet, brown dwarf, or red dwarf that is very likely to be within a single light year distant. At each destination repair, refuel, resupply and move on. In a time span of only a fraction of the age of human civilization significant populations of humans will spread out from our Solar System and diffuse through interstellar space.

hahainternet 15y ago

This is remarkably negative. There are a number of ways to explore without having to break physics. Constant 1g acceleration makes nearby galaxies accessible, nevermind nearby solar systems. Returning from exploration? Reporting results? That isn't going to happen. Colonizing the universe? There's nothing at all stopping it in physical law.

drostie 15y ago
Constant 1g acceleration makes nearby galaxies accessible, nevermind nearby solar systems. "Break physics" is relative -- things which can be allowed by the laws of physics can be so humanly implausible as to be useless to discuss. I mean, let me just be totally clear about this. In relativity, to get your time dilation factor γ up, you need a lot of kinetic energy K. How much? Well E = γ m c² = m c² + K, so K = (γ − 1) m c². If you wanted to go to the nearest galaxy -- which is 25,000 light years away on the other side of the Milky Way -- and you wanted to do it with any sort of vehicle in 25 years -- you would have to take along about 1000 times the mass of your vehicle as fuel. More importantly, whatever fuel you're using to accelerate you're also using to decelerate, so you actually need 1,000,000x fuel to start with, to get your 1,000x fuel up to speed for most of the journey. So your 10^5 kg shuttle orbiter would need to come with 10^8 kg slowdown fuel. That's what we're sending around, you've got to build the Great Pyramid at Giza out of antimatter and find a way to carry it with you, just to get the shuttle to do this in a reasonable time. Now c² is about 10^17 J/kg so we need about 10^25 J to slow down, and to send this would require 10^28 J. For perspective, our largest nuclear blasts (Tsar Bomba's 50 megaton yield) are 2 * 10^17 J, so you'd need fifty million of those to launch. Or you could just carry the US with you, that has an annual power consumption of 10^22 J -- wait, make that a million copies of the United States, before you could launch. Of course, antimatter is unstable and you might want to carry the Tsar Bomba around as a massive fuel source instead, but the Tsar Bomba actually only carried an energy yield of around 10^-4 m c², so you would need to have 10,000 times more mass (10 million space shuttles to decelerate your one) if you wanted to do it with nuclear bombs.
- hahainternet 15y ago
  The reason I mentioned no returning of data is that it obviously is not plausible within 25 years. I appreciate you doing the mathematics, but you don't base it on the 1g acceleration I mentioned, as far as I can tell.

dodo53 15y ago

I think what it will take is mind uploading. Once a sentience can suspend until interesting circumstances are detected, I'm sure some wealthy people will go decide to go off explore the galaxy / take a punt on van neuman machine mining.