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> Personally I still think that we've just scratched the surface of the laws of the universe and it's not impossible that we'll have another wave of theories th

> Personally I still think that we've just scratched the surface of the laws of the universe and it's not impossible that we'll have another wave of theories that will make our current understanding of physics seem hopelessly outdated by the end of the century. I hope that this the case, otherwise humanity will die on this planet. If there are no new physics then there is no faster-than-light travel and escaping earth will be pretty much impossible.

ChrisSD 8y ago
I'm not sure new physics will help with that. Faster than light travel, if possible, would really screw with causality. Besides, we can always travel the slow way. Either with ships built for multi-generational habitation or some way to suspend/resume human life over long periods.
- wtetzner 8y ago
  Well, it depends on what you mean, I guess. You can't travel through space faster than light, but if we could figure out how to create and use wormholes, for example, we could potentially travel to places that are out of reach when traveling through space.
  - akvadrako 8y ago
    No, that would have the same problem - being able to send information back in time. We also have no theory of traversable wormholes that doesn't involve imaginary energy, so it's just fantasy.
    - wtetzner 8y ago
      I don't know much about this stuff, so take this as me being genuinely curious. > No, that would have the same problem - being able to send information back in time. Would it? If a wormhole is connecting two points in spacetime, then could time also be traversed at the same time? E.g. traveling through the wormhole would move you far enough forward in time to not cause any problems?
      - akvadrako 8y ago
        Sure, you can travel 1 light year if you also go 1 year ahead in time without any causality issues.
  - deleted 8y ago
    [deleted]
- yoodenvranx 8y ago
  > Faster than light travel, if possible, would really screw with causality Well, the assumption abiut causality is based on our current understanding of physics. Perhaps we just don't understand the problem well enough and there are ways around the causality problem
Santosh83 8y ago
We may not need FTL travel, at least for interstellar exploration, as opposed to intergalactic. Even a ship going at 50% of light speed would put hundreds of stars within a reasonable time-frame, especially coupled with advances in cryogenic technology. If humanity's only goal is to avoid extinction by colonising another planet (what a dreary prospect), then this ought to be quite enough.
- coldtea 8y ago
  Or maybe the universe is indifferent to our goals, and we're stranded in this rock without sufficient materials and ways to get away, no matter how inventive we can be. (The same way inventiveness doesn't matter if you found yourself in the middle of Antarctica with no food, no heating, and no materials to make a compass).
  - tajen 8y ago
    Don’t say that! It shatters so many people’s dreams, which they really really think are reasonable and will come true. More seriously, I wonder what happens if we let people believe life on Mars is feasible, and we only tell them a century later that it was unrealistic. Will they massively invest in it? Given the time it took for Galileo to persuade thick-headed people that the Earth ran around the Sun despite their beliefs, and how much they were ready to torture for this reason, I wonder how far the belief of Mars can go.
  - bsder 8y ago
    Actually, we seem to be unnaturally lucky in this regard. I think if the Earth was something like 40% more massive, we wouldn't be able to leave the surface with chemical propulsion.
    - foota 8y ago
      Wow, that's a really awesome factoid. This QA goes more into this observation: https://space.stackexchange.com/questions/14383/how-much-bigger-could-earth-be-before-rockets-wouldt-work https://space.stackexchange.com/questions/14383/how-much-big... From what's there it looks like it's a lot higher than 40% as a limit.
A2017U1 8y ago
With a constant 1g acceleration up until near the speed of light you can cross the observable universe in a human lifetime. To the other side of the galaxy it would be 12 years https://en.wikipedia.org/wiki/Space_travel_using_constant_acceleration#Ship_reference_frame https://en.wikipedia.org/wiki/Space_travel_using_constant_ac...
- jerf 8y ago
  And what does modern physics say is necessary to maintain a constant 1g acceleration for years at a time?
  - pacala 8y ago
    A ball of iron the size of Earth. I'll show myself out now.
  - A2017U1 8y ago
    To reach close to the speed of light (~0.9c?) it'll take about 1 year before turning off the engine, and then another year of deceleration if you're planning to do anything else besides travel around at relativistic speeds. Going to Mars using antimatter with the same 1g acceleration the entire time (reversing half way) will take a few weeks and require a small fraction of a gram of antimatter. Ignoring the significant engineering problems like heat disappation, storage if it's not used instantly, you could get two years worth of thrust from antimatter measured in grams and cross the galaxy in just over a decade, in Earth time the trip would be >100,000 years.
- noddy1w 8y ago
  Isn't the milky way 100000 light years across?
  - cygx 8y ago
    Time dilation: At a constant acceleration of 1g, 100k galactic time reduces to 12 years ship time. Cf the link provided in the comment you're replying to.
  - 8y ago
jotm 8y ago
Why would you need FTL? There's a whole system to colonize in our backyard. Teraforming seems daunting, but start one dome at a time and it grows from there. And the technology is pretty much there, it's just that the will isn't. Is taking an FTL ship to another galaxy, even with a known habitable planet, that much easier than creating a dome city on Mars? What if they're barely habitable? Who is going to do that and what for? Same resources, and no one wants to because Earth already has it all (and yes, by the time they're exhausted, it will be too late for anything). Colonize the solar system, and if FTL is created, great, if not, meh.
Nasrudith 8y ago
It is perfectly possible to travel vast distances without FTL: just self-sustaining generation ships that are capable of operating indefinitely. A very boring solution to the problem admittedly. It is even possible without generation ships if the understanding of biology advanced enough to allow for indefinite cell repair, or 'state restore' of DNA. Obviously beyond our capabilities but there is no 'special sauce' required just a lot of depth. Although it brings to mind the irony that if one has the capability to live in space within artificial environments indefinitely, gather resources within it, and produce more of them there isn't technically a need to find any habitable planets. If such a state is reached there are only two things to worry about - self destruction and entropy or cosmic scale events that a planet wouldn't be safe from anyway.
otabdeveloper2 8y ago
> escaping earth The fact that you're trying to 'escape' your home points to some deep-seated psychological problems that won't be fixed by just running away.
- adwn 8y ago
  > The fact that you're trying to 'escape' your home points to some deep-seated psychological problems that won't be fixed by just running away. It's a figure of speech, don't over-analyze it.
- yoodenvranx 8y ago
  The sun will explode in x million years. When that happens the current inhabitants of earth _have_ to escape earth.
- dang 8y ago
  Personal attacks will get you banned here, so please don't post like this again. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
CM30 8y ago
Given we've got about 7.5 billion years until the sun burns out, and about 1 billion years before anything may become completely uninhabitable, it's pretty unlikely either new technology or space colonisation won't have happened before then. I mean, for comparison humans have been around in a modern form for about 50,000 years... well the chances of something not happening then are few and far between. Probably could have launched millions of generation ships between now and then.
goatlover 8y ago
> I hope that this the case, otherwise humanity will die on this planet. If there are no new physics then there is no faster-than-light travel and escaping earth will be pretty much impossible. In the long term, we have the entire solar system to work with, which should be plenty to keep us going for a very long time. The Earth is just a small fraction of what's available even if we're stuck with our sun. Frank Drake from SETI thinks that alien civilizations have no good reason to ever leave their home stars, because a star will provide all the energy they will ever need, and traveling light years just isn't worth the cost (assuming no FTL).
Certhas 8y ago
There is basically no chance[1] that new physics would allow meaningful violations of the speed of light bound. It's as well established as conservation of energy. [1] Meaning that, though it's not logically ruled out, you need flying Spaghetti Monster level subterfuge to make it compatible with what we know to be true.
Razengan 8y ago
> If there are no new physics then there is no faster-than-light travel and escaping earth will be pretty much impossible. Interstellar travel and colonization does not necessarily need superluminal travel; it could be done with sub-lightspeed spacecraft capable of hosting multiple generations of humans for many decades, possibly centuries. However getting Earth's nations to cooperate on such a long-term undertaking may be no less difficult than achieving FTL travel.

ChrisSD 8y ago

I'm not sure new physics will help with that. Faster than light travel, if possible, would really screw with causality. Besides, we can always travel the slow way. Either with ships built for multi-generational habitation or some way to suspend/resume human life over long periods.

wtetzner 8y ago
Well, it depends on what you mean, I guess. You can't travel through space faster than light, but if we could figure out how to create and use wormholes, for example, we could potentially travel to places that are out of reach when traveling through space.
- akvadrako 8y ago
  No, that would have the same problem - being able to send information back in time. We also have no theory of traversable wormholes that doesn't involve imaginary energy, so it's just fantasy.
  - wtetzner 8y ago
    I don't know much about this stuff, so take this as me being genuinely curious. > No, that would have the same problem - being able to send information back in time. Would it? If a wormhole is connecting two points in spacetime, then could time also be traversed at the same time? E.g. traveling through the wormhole would move you far enough forward in time to not cause any problems?
    - akvadrako 8y ago
      Sure, you can travel 1 light year if you also go 1 year ahead in time without any causality issues.
- deleted 8y ago
  [deleted]
yoodenvranx 8y ago
> Faster than light travel, if possible, would really screw with causality Well, the assumption abiut causality is based on our current understanding of physics. Perhaps we just don't understand the problem well enough and there are ways around the causality problem

Santosh83 8y ago

We may not need FTL travel, at least for interstellar exploration, as opposed to intergalactic. Even a ship going at 50% of light speed would put hundreds of stars within a reasonable time-frame, especially coupled with advances in cryogenic technology. If humanity's only goal is to avoid extinction by colonising another planet (what a dreary prospect), then this ought to be quite enough.

coldtea 8y ago
Or maybe the universe is indifferent to our goals, and we're stranded in this rock without sufficient materials and ways to get away, no matter how inventive we can be. (The same way inventiveness doesn't matter if you found yourself in the middle of Antarctica with no food, no heating, and no materials to make a compass).
- tajen 8y ago
  Don’t say that! It shatters so many people’s dreams, which they really really think are reasonable and will come true. More seriously, I wonder what happens if we let people believe life on Mars is feasible, and we only tell them a century later that it was unrealistic. Will they massively invest in it? Given the time it took for Galileo to persuade thick-headed people that the Earth ran around the Sun despite their beliefs, and how much they were ready to torture for this reason, I wonder how far the belief of Mars can go.
- bsder 8y ago
  Actually, we seem to be unnaturally lucky in this regard. I think if the Earth was something like 40% more massive, we wouldn't be able to leave the surface with chemical propulsion.
  - foota 8y ago
    Wow, that's a really awesome factoid. This QA goes more into this observation: https://space.stackexchange.com/questions/14383/how-much-bigger-could-earth-be-before-rockets-wouldt-work https://space.stackexchange.com/questions/14383/how-much-big... From what's there it looks like it's a lot higher than 40% as a limit.

A2017U1 8y ago

With a constant 1g acceleration up until near the speed of light you can cross the observable universe in a human lifetime. To the other side of the galaxy it would be 12 years https://en.wikipedia.org/wiki/Space_travel_using_constant_acceleration#Ship_reference_frame https://en.wikipedia.org/wiki/Space_travel_using_constant_ac...

jerf 8y ago
And what does modern physics say is necessary to maintain a constant 1g acceleration for years at a time?
- pacala 8y ago
  A ball of iron the size of Earth. I'll show myself out now.
- A2017U1 8y ago
  To reach close to the speed of light (~0.9c?) it'll take about 1 year before turning off the engine, and then another year of deceleration if you're planning to do anything else besides travel around at relativistic speeds. Going to Mars using antimatter with the same 1g acceleration the entire time (reversing half way) will take a few weeks and require a small fraction of a gram of antimatter. Ignoring the significant engineering problems like heat disappation, storage if it's not used instantly, you could get two years worth of thrust from antimatter measured in grams and cross the galaxy in just over a decade, in Earth time the trip would be >100,000 years.
noddy1w 8y ago
Isn't the milky way 100000 light years across?
- cygx 8y ago
  Time dilation: At a constant acceleration of 1g, 100k galactic time reduces to 12 years ship time. Cf the link provided in the comment you're replying to.
- 8y ago

jotm 8y ago

Why would you need FTL? There's a whole system to colonize in our backyard. Teraforming seems daunting, but start one dome at a time and it grows from there. And the technology is pretty much there, it's just that the will isn't. Is taking an FTL ship to another galaxy, even with a known habitable planet, that much easier than creating a dome city on Mars? What if they're barely habitable? Who is going to do that and what for? Same resources, and no one wants to because Earth already has it all (and yes, by the time they're exhausted, it will be too late for anything). Colonize the solar system, and if FTL is created, great, if not, meh.

Nasrudith 8y ago

It is perfectly possible to travel vast distances without FTL: just self-sustaining generation ships that are capable of operating indefinitely. A very boring solution to the problem admittedly. It is even possible without generation ships if the understanding of biology advanced enough to allow for indefinite cell repair, or 'state restore' of DNA. Obviously beyond our capabilities but there is no 'special sauce' required just a lot of depth. Although it brings to mind the irony that if one has the capability to live in space within artificial environments indefinitely, gather resources within it, and produce more of them there isn't technically a need to find any habitable planets. If such a state is reached there are only two things to worry about - self destruction and entropy or cosmic scale events that a planet wouldn't be safe from anyway.

otabdeveloper2 8y ago

> escaping earth The fact that you're trying to 'escape' your home points to some deep-seated psychological problems that won't be fixed by just running away.

adwn 8y ago
> The fact that you're trying to 'escape' your home points to some deep-seated psychological problems that won't be fixed by just running away. It's a figure of speech, don't over-analyze it.
yoodenvranx 8y ago
The sun will explode in x million years. When that happens the current inhabitants of earth _have_ to escape earth.
dang 8y ago
Personal attacks will get you banned here, so please don't post like this again. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html

CM30 8y ago

Given we've got about 7.5 billion years until the sun burns out, and about 1 billion years before anything may become completely uninhabitable, it's pretty unlikely either new technology or space colonisation won't have happened before then. I mean, for comparison humans have been around in a modern form for about 50,000 years... well the chances of something not happening then are few and far between. Probably could have launched millions of generation ships between now and then.

goatlover 8y ago

> I hope that this the case, otherwise humanity will die on this planet. If there are no new physics then there is no faster-than-light travel and escaping earth will be pretty much impossible. In the long term, we have the entire solar system to work with, which should be plenty to keep us going for a very long time. The Earth is just a small fraction of what's available even if we're stuck with our sun. Frank Drake from SETI thinks that alien civilizations have no good reason to ever leave their home stars, because a star will provide all the energy they will ever need, and traveling light years just isn't worth the cost (assuming no FTL).

Certhas 8y ago

There is basically no chance[1] that new physics would allow meaningful violations of the speed of light bound. It's as well established as conservation of energy. [1] Meaning that, though it's not logically ruled out, you need flying Spaghetti Monster level subterfuge to make it compatible with what we know to be true.

Razengan 8y ago

> If there are no new physics then there is no faster-than-light travel and escaping earth will be pretty much impossible. Interstellar travel and colonization does not necessarily need superluminal travel; it could be done with sub-lightspeed spacecraft capable of hosting multiple generations of humans for many decades, possibly centuries. However getting Earth's nations to cooperate on such a long-term undertaking may be no less difficult than achieving FTL travel.