4 ms·

Not having celestial navigation would also make such exploration more difficult.

mistercow 3y ago
Yeah, although given that ancient humans figured that out, maybe it wouldn’t take an advanced civilization very long. That’s probably the biggest flaw with the idea. Like, imagine a civilization at our stage, minus the stuff we learned by having a night sky (no universal gravitation; computers and radio, but no GPS; quantum physics but no general relativity, and so on). Now they manage to voyage into the cold, dark night. How quickly can they catch up? Decades maybe, but probably not centuries. I think the other question is cultural. How much do they _care_ about space, when even the basic concept is new and alien, and studying it is very expensive?
- fnordpiglet 3y ago
  I’d note that navigation was most important on oceans while terrestrial navigation relied on landmarks and maps. I wonder though how much exploration helped lead to an advanced civilization. The exchange of ideas with different cultures was crucial as was the necessity to develop the technologies for exploration beyond navigation alone. It wasn’t until we broadly navigated the planet that we advanced so rapidly after tens of thousands of years of relatively isolated stagnation.
  - TheOtherHobbes 3y ago
    I have a theory that Western culture developed relatively quickly because the geography is basically easily-farmable land around an inland sea with plenty of islands which is easy to navigate and explore. The Egyptians and the Phoenicians lacked the easily farmable land. Greece was fertile but a little arid, Northern Europe was harsher and riskier, but Rome was in a perfect sweet spot. On the other side of the world China had the farmland but not the inland sea, so there was less motivation for sea-borne trade and exploration. So it all started with a tradition that required basic materials science, knowledge of the weather, currents, and seasons, navigation by the sky, and the politics of war and trade across large distances. And it didn't stop until we had explored the entire planet and taken the first steps into space. In between we had to learn about time, navigation, and planetary weather patterns, how to build and power better ships, and more complex politics. It seems like a very natural progression.
    - deleted 3y ago
      [deleted]
    - fnordpiglet 3y ago
      A few notes - Western culture didn’t develop very quickly - the geography had humans for tens of thousands of years before culture developed quickly. Other parts of the world actually developed relatively advanced civilizations long before Europe. I think once it began to develop it developed quickly partially due to the geography, but it was also through trade with the Middle East and Asia, which were the sources of a lot of the technology bootstrap priming Europe to develop rapidly. It’s indisputable that once the ball really began rolling Europe brought us to the modern age rapidly. But I’m dubious of the geography argument personally since it was so late in developing relative to other societies, including those in the americas. China actually was an advanced maritime society, with expeditions across most of the world including to the Americas. In fact in the 1400s China was the world’s most powerful navy. https://en.m.wikipedia.org/wiki/Naval_history_of_China https://en.m.wikipedia.org/wiki/Naval_history_of_China
    - Bene592 3y ago
      China had the sea between China and Japan, and they had some nice oceangoing ships¹. [1] https://en.wikipedia.org/wiki/Junk_(ship) https://en.wikipedia.org/wiki/Junk_(ship)
  - pests 3y ago
    We navigated before compasses or any time of position system. Ships would travel well known routes from one place to another, with no care or knowledge of the actual topology. You knew you could go a straight line from point A to points B and C, and from C to D. Even if D turns out to be near by to A, all that existed were routes between points, and people would likely still travel to C to reach D. It worked despite not really knowing where exactly anything was positioned.
- marcosdumay 3y ago
  > the stuff we learned by having a night sky You are forgetting stuff like platonic modeling of the real world, testing hypothesis on the basis of their predictive values, and integrating the smart people as a community where they exchange ideas. We learned all of those by observing the sky. Of course, there are probably other ways to learn it. But it's not clear at all how viable they are or how long they would take.
- kjkjadksj 3y ago
  We really didn’t even care about space, until we decided spaceflight might lead to easier control of the strings of power through use of icbms or even manned space stations. Then it became an appreciable fraction of our GDP overnight, from no polling of voters only under the pressure of our unelected military authority.
  - mistercow 3y ago
    For space exploration sure, but astronomy was a pretty big deal for centuries before space flight was a remote possibility. But I think the fact that the stars are staring you in the face on a regular basis when you look up has to have been a big influence there. For our hypothetical tidally locked culture, the stars would be, to most people, more akin to the cosmic microwave background. They’d be something scientists could take pictures of and form theories about, but totally removed from everyday experience.
neaden 3y ago
On the other hand, having the sun as a fixed point seems like it could make it much easier, presumably navigation would be based around that.
wolfram74 3y ago
If the planet had a decent magnetic field, it might actually be quite easy to navigate. A sextant would get you "solar latitude" as it were (the angle of the sun relative to the horizon defines a circle), and coupled with magnetic orientation I think that would narrow it down to one of four points on the day side of the planet (where the field lines have a given angle with the radius of the previously defined circle). Given even crude object permanence I think that should fix your position pretty well.
- amluto 3y ago
  On the night side, you could get a decent idea of your absolute position by observing the stars, just like how you can do this on Earth if you have a good clock. On a tidally locked planet, your clock doesn’t need to be very good. I imagine that a similar if somewhat more complex trick works on the day side if there’s a visible moon.
  - jonathanlydall 3y ago
    The stars would still rotate around the planet, but the rotation would be that of the planet rotating around its star. So one would need timekeeping to track where you are in that cycle.
    - amluto 3y ago
      Indeed, but process is quite a bit slower, so you could likely get away with a worse clock.
    - IntrepidWorm 3y ago
      Since the cycle of stellar observation repeats each solar year, the observation would itself be a method of time keeping. One would need only to track the azimuth of a series of regularly positioned star constellations to determine time, and from there one could then ascertain location.
- saagarjha 3y ago
  Do tidally locked planets typically have a magnetic field?
PaulHoule 3y ago
If the sun is always in the same place it is easy to figure out how far you are away from the center. If the planet is so lucky to have a dipolar magnetic field you can get a 2-d position, and it would be easier than being on Earth because you don't need an accurate clock the way you do on Earth: https://www.destination-innovation.com/john-harrison-the-master-craftsman-who-solved-the-longitude-challenge/ https://www.destination-innovation.com/john-harrison-the-mas... … assuming of course you can see the sun which might be trouble when you get sunwards (too many clouds)
- fbdab103 3y ago
  1) I am furious on Harrison's behalf. Great story, if rage inducing. 2) How does one precisely determine noon from the position of the sun? That feels like that would be a sloppy measurement, which would eclipse the error in the clocks.
- Bene592 3y ago
  A planet that Spins only once in one of its years probably isn't dipolar
  - PaulHoule 3y ago
    Mercury has a low rotation rate but it does have a weak magnetic field: see https://en.wikipedia.org/wiki/Mercury%27s_magnetic_field https://en.wikipedia.org/wiki/Mercury%27s_magnetic_field I'm not so sure how easy it is to make a compass that works on a weaker field.
tzs 3y ago
A tidal locked planet is still rotating, just a lot slower than more "normal" planets, so maybe you could use some of the effects of the rotation to help figure out position? For example set up a Foucault pendulum and observe it long enough to determine the angular speed of its precession. From that you can determine your latitude. There will be only two points on the surface of your planet that have that latitude and have your sun in the right place.

Yeah, although given that ancient humans figured that out, maybe it wouldn’t take an advanced civilization very long. That’s probably the biggest flaw with the idea. Like, imagine a civilization at our stage, minus the stuff we learned by having a night sky (no universal gravitation; computers and radio, but no GPS; quantum physics but no general relativity, and so on). Now they manage to voyage into the cold, dark night. How quickly can they catch up? Decades maybe, but probably not centuries. I think the other question is cultural. How much do they _care_ about space, when even the basic concept is new and alien, and studying it is very expensive?

fnordpiglet 3y ago
I’d note that navigation was most important on oceans while terrestrial navigation relied on landmarks and maps. I wonder though how much exploration helped lead to an advanced civilization. The exchange of ideas with different cultures was crucial as was the necessity to develop the technologies for exploration beyond navigation alone. It wasn’t until we broadly navigated the planet that we advanced so rapidly after tens of thousands of years of relatively isolated stagnation.
- TheOtherHobbes 3y ago
  I have a theory that Western culture developed relatively quickly because the geography is basically easily-farmable land around an inland sea with plenty of islands which is easy to navigate and explore. The Egyptians and the Phoenicians lacked the easily farmable land. Greece was fertile but a little arid, Northern Europe was harsher and riskier, but Rome was in a perfect sweet spot. On the other side of the world China had the farmland but not the inland sea, so there was less motivation for sea-borne trade and exploration. So it all started with a tradition that required basic materials science, knowledge of the weather, currents, and seasons, navigation by the sky, and the politics of war and trade across large distances. And it didn't stop until we had explored the entire planet and taken the first steps into space. In between we had to learn about time, navigation, and planetary weather patterns, how to build and power better ships, and more complex politics. It seems like a very natural progression.
  - deleted 3y ago
    [deleted]
  - fnordpiglet 3y ago
    A few notes - Western culture didn’t develop very quickly - the geography had humans for tens of thousands of years before culture developed quickly. Other parts of the world actually developed relatively advanced civilizations long before Europe. I think once it began to develop it developed quickly partially due to the geography, but it was also through trade with the Middle East and Asia, which were the sources of a lot of the technology bootstrap priming Europe to develop rapidly. It’s indisputable that once the ball really began rolling Europe brought us to the modern age rapidly. But I’m dubious of the geography argument personally since it was so late in developing relative to other societies, including those in the americas. China actually was an advanced maritime society, with expeditions across most of the world including to the Americas. In fact in the 1400s China was the world’s most powerful navy. https://en.m.wikipedia.org/wiki/Naval_history_of_China https://en.m.wikipedia.org/wiki/Naval_history_of_China
  - Bene592 3y ago
    China had the sea between China and Japan, and they had some nice oceangoing ships¹. [1] https://en.wikipedia.org/wiki/Junk_(ship) https://en.wikipedia.org/wiki/Junk_(ship)
- pests 3y ago
  We navigated before compasses or any time of position system. Ships would travel well known routes from one place to another, with no care or knowledge of the actual topology. You knew you could go a straight line from point A to points B and C, and from C to D. Even if D turns out to be near by to A, all that existed were routes between points, and people would likely still travel to C to reach D. It worked despite not really knowing where exactly anything was positioned.
marcosdumay 3y ago
> the stuff we learned by having a night sky You are forgetting stuff like platonic modeling of the real world, testing hypothesis on the basis of their predictive values, and integrating the smart people as a community where they exchange ideas. We learned all of those by observing the sky. Of course, there are probably other ways to learn it. But it's not clear at all how viable they are or how long they would take.
kjkjadksj 3y ago
We really didn’t even care about space, until we decided spaceflight might lead to easier control of the strings of power through use of icbms or even manned space stations. Then it became an appreciable fraction of our GDP overnight, from no polling of voters only under the pressure of our unelected military authority.
- mistercow 3y ago
  For space exploration sure, but astronomy was a pretty big deal for centuries before space flight was a remote possibility. But I think the fact that the stars are staring you in the face on a regular basis when you look up has to have been a big influence there. For our hypothetical tidally locked culture, the stars would be, to most people, more akin to the cosmic microwave background. They’d be something scientists could take pictures of and form theories about, but totally removed from everyday experience.

neaden 3y ago

On the other hand, having the sun as a fixed point seems like it could make it much easier, presumably navigation would be based around that.

wolfram74 3y ago

If the planet had a decent magnetic field, it might actually be quite easy to navigate. A sextant would get you "solar latitude" as it were (the angle of the sun relative to the horizon defines a circle), and coupled with magnetic orientation I think that would narrow it down to one of four points on the day side of the planet (where the field lines have a given angle with the radius of the previously defined circle). Given even crude object permanence I think that should fix your position pretty well.

amluto 3y ago
On the night side, you could get a decent idea of your absolute position by observing the stars, just like how you can do this on Earth if you have a good clock. On a tidally locked planet, your clock doesn’t need to be very good. I imagine that a similar if somewhat more complex trick works on the day side if there’s a visible moon.
- jonathanlydall 3y ago
  The stars would still rotate around the planet, but the rotation would be that of the planet rotating around its star. So one would need timekeeping to track where you are in that cycle.
  - amluto 3y ago
    Indeed, but process is quite a bit slower, so you could likely get away with a worse clock.
  - IntrepidWorm 3y ago
    Since the cycle of stellar observation repeats each solar year, the observation would itself be a method of time keeping. One would need only to track the azimuth of a series of regularly positioned star constellations to determine time, and from there one could then ascertain location.
saagarjha 3y ago
Do tidally locked planets typically have a magnetic field?

PaulHoule 3y ago

If the sun is always in the same place it is easy to figure out how far you are away from the center. If the planet is so lucky to have a dipolar magnetic field you can get a 2-d position, and it would be easier than being on Earth because you don't need an accurate clock the way you do on Earth: https://www.destination-innovation.com/john-harrison-the-master-craftsman-who-solved-the-longitude-challenge/ https://www.destination-innovation.com/john-harrison-the-mas... … assuming of course you can see the sun which might be trouble when you get sunwards (too many clouds)

fbdab103 3y ago
1) I am furious on Harrison's behalf. Great story, if rage inducing. 2) How does one precisely determine noon from the position of the sun? That feels like that would be a sloppy measurement, which would eclipse the error in the clocks.
Bene592 3y ago
A planet that Spins only once in one of its years probably isn't dipolar
- PaulHoule 3y ago
  Mercury has a low rotation rate but it does have a weak magnetic field: see https://en.wikipedia.org/wiki/Mercury%27s_magnetic_field https://en.wikipedia.org/wiki/Mercury%27s_magnetic_field I'm not so sure how easy it is to make a compass that works on a weaker field.

tzs 3y ago

A tidal locked planet is still rotating, just a lot slower than more "normal" planets, so maybe you could use some of the effects of the rotation to help figure out position? For example set up a Foucault pendulum and observe it long enough to determine the angular speed of its precession. From that you can determine your latitude. There will be only two points on the surface of your planet that have that latitude and have your sun in the right place.