How do you measure time on a tide locked planet?

[Janus]

I was wondering to what extend tidally locked planets would even experience winds — and if so, of what sort (strength, direction etc.)?

With no rotation, no different levels of heat from the sun hitting any given point on the surface, I struggle to imagine in what ways the star could even influence the weather on the planet — aside from different levels in intensity of the star’s own activity, and the planet’s changing distance to the star during its orbit around it.

Note that most tidally locked planets should be rocky planets around red dwarf stars, not around big stars of the type you described. Meaning, the habitable zone is so close to the star that the planet’s orbit would only take a few (say, 5 to 11) days to complete once.

If there are winds in at least two directions, temperatures in one given location on the surface could then be influenced by whether the wind is currently coming from the day side (warm) or night side (cold). This could “simulate” a day-and-night shift, if not in terms of light exposure, then at least in terms of temperature.

I chimed in here because I have a tidally locked planet in my story, too — so I’m facing the same problems.

One thing to keep in mind is that being tidally locked does preclude having an axial tilt. For example, our own moon is tidally locked, but has a 6 degree axial tilt to its orbit, thus alternates between presenting its North and South Poles to the Earth.
So, an axial tilt could produce "seasonal" changes to a certain degree.

 

[symbolipoint]

What's wrong with a wristwatch?

Plenty of earth times do not have astronomical counterparts: the minute, the hour, the week, the time between when you were supposed to change your oil and the time you actually did,

Whole topic is too long to read; but I did see that quoted post.
Also, "hour-glass". Maybe difficulty with precision, but should work.

 

[DaveC426913]

Sure, but still I think it's more important to ask if - on a planet that has no clear periodic cycles of its own - a culture would evolve a need to "keep time" at all, let alone invent a device to track it moment by moment.

Looking at it the the other way 'round: it could be argued that humans only invented time-keeping because we evolved for a billion years in an environment that is intimately connected with short cycles such as the day/night cycle.

 

[Vanadium 50]

Of course they would need to keep time. How long does it take to cook an egg?

 

[DaveC426913]

Of course they would need to keep time. How long does it take to cook an egg?

I think you're half joking but you make a good argument.

I can see an alien society arising that is more attached to circumstantial and concrete indicators of change in the world* rather than some abstraction of changes like we have encapsulated in clocks.

*The way our ancestors looked to changes in the countryside to know when harvest was coming. That, but writ small.They might learn to know when an egg is cooked by observation - a subtle change in shell colour, a change in its buoyancy, etc. If it didn't happen naturally, they may have developed clever hacks to facilitate it - say, a simple substance that, when added to the water, changes colour when the egg is cooked, etc.

Such changes would be things they are predisposed to be attuned to, since they never really developed a standardized time - and might permeate all aspects of their philosophies. The very idea of standardizing things (such as money) might be foreign to them.

Standardization can be harmful if taken past a certain limit. We humans might learn a thing or two from them.

I'm not suggesting there's a rational basis for this, simply that it would make a creative foundation for the narrative of their culture in the fiction.

 

[Hornbein]

I think you're half joking but you make a good argument.

I can see an alien society arising that is more attached to circumstantial and concrete indicators of change in the world* rather than some abstraction of changes like we have encapsulated in clocks.

*The way our ancestors looked to changes in the countryside to know when harvest was coming. That, but writ small.They might learn to know when an egg is cooked by observation - a subtle change in shell colour, a change in its buoyancy, etc. If it didn't happen naturally, they may have developed clever hacks to facilitate it - say, a simple substance that, when added to the water, changes colour when the egg is cooked, etc.

Such changes would be things they are predisposed to be attuned to, since they never really developed a standardized time - and might permeate all aspects of their philosophies. The very idea of standardizing things (such as money) might be foreign to them.

Standardization can be harmful if taken past a certain limit. We humans might learn a thing or two from them.

I'm not suggesting there's a rational basis for this, simply that it would make a creative foundation for the narrative of their culture in the fiction.

They would certainly have time. It's very basic. Your concept of time doesn't have to be cyclic or period. You can just count seconds since some particular standard moment. Calendars? Dubious.

 

[Hornbein]

One thing to keep in mind is that being tidally locked does preclude having an axial tilt. For example, our own moon is tidally locked, but has a 6 degree axial tilt to its orbit, thus alternates between presenting its North and South Poles to the Earth.
So, an axial tilt could produce "seasonal" changes to a certain degree.

I have read that the ecliptic [tilt of the orbital plane relative to Earth's rotational plane] of the Moon is six degrees. Is that what you are saying? Or is the Moon's axis tilted relative to its plane of rotation?

I expect it is the former. Then an observer on Earth will see the Moon differently in different parts of its orbit. But this is irrelevant to the tidally locked planet's seasons. What matters there is the total amount of solar radiation received. This is the sum of radiation received from all points on the Sun. As the planet moves some points will give you more energy, some less, but I'm pretty sure the sum will remain the same. If so the amount of solar energy at any point on the tidally locked planet will not change with the orbit.

 

[Janus]

I have read that the ecliptic [tilt of the orbital plane relative to Earth's rotational plane] of the Moon is six degrees. Is that what you are saying? Or is the Moon's axis tilted relative to its plane of rotation?

I expect it is the former. Then an observer on Earth will see the Moon differently in different parts of its orbit. But this is irrelevant to the tidally locked planet's seasons. What matters there is the total amount of solar radiation received. This is the sum of radiation received from all points on the Sun. As the planet moves some points will give you more energy, some less, but I'm pretty sure the sum will remain the same. If so the amount of solar energy at any point on the tidally locked planet will not change with the orbit.

The Moon's orbit is tilted at 5 degrees relative to the Ecliptic ( the Earth's orbit around the Sun), but its axis of rotation, is tilted by 6 degrees to its orbit around the Earth. (like the Earth's is tilted at 23 degree to its solar orbit.) This causes a Libration of Latitude, where it presents a bit more of its North pole to the Earth at one point of it orbit, and a bit more of its South pole half an orbit later.

An axial tilt with respect to the orbit would change the angle at which the Sun's light struck the surface at any given point over the course of an orbit. This would effect the surface heating at that point. This change in the angle of Sunlight is a component of our seasons. This effect would be most noticeable near the poles, and the planet would have the equivalent of Arctic and Antarctic circles, with regions near the poles where the Sun rose and set over the course of an orbit.

Keep in mind that "tidally locked" does not equal "keeping the exact same face to the Sun at all times", but means the period of rotation equals the period of the orbit.

 

[russ_watters]

I can see an alien society arising that is more attached to circumstantial and concrete indicators of change in the world* rather than some abstraction of changes like we have encapsulated in clocks.

Time is no more an abstraction than length is.

This entire thread is bizarre to me.

 

[symbolipoint]

Time is no more an abstraction than length is.

This entire thread is bizarre to me.

Someone wants to explore the question, and is receiving some thoughts on the question.

 

[DaveC426913]

Time is no more an abstraction than length is.

It's the clock that is an abstraction of time.

While in principle you are right - a ruler is just as much an abstraction of distance, I still see a difference between:
- this field is 100 of my strides wide
and
- this egg takes 180 of my heartbeats to cook

I grant it's not an inevitable outcome, but evolution - and cultural evolution - is undirected. Rewind and replay it ad you might get totally different results, no?

This entire thread is bizarre to me.

Barring that its premise is positing the implications of a fictional ecosystem on a fictional world, what is bizarre? You you think a totally alien race will draw the same observations of their world as us?

 

[russ_watters]

It's the clock that is an abstraction of time.

While in principle you are right - a ruler is just as much an abstraction of distance, I still see a difference between:
- this field is 100 of my strides wide
and
- this egg takes 180 of my heartbeats to cook

That's an aesthetic concern. It's common, but isn't how physics/physicists view it.

I grant it's not an inevitable outcome, but evolution - and cultural evolution - is undirected. Rewind and replay it ad you might get totally different results, no?

Sure. But what's being suggested here is that without a planet's rotation, there might not be/be a need for time. That's ridiculous. Heck, there's organisms on Earth who never see the sun and they get along just fine, self-regulating. There's also been studies of what happens to people if you deny them access to information about time (have them live in a cave with no clocks).

Barring that its premise is positing the implications of a fictional ecosystem on a fictional world, what is bizarre? You you think a totally alien race will draw the same observations of their world as us?

No, again, the bizarre part is the idea that they could exist and function without understanding time just because they don't see sunrises and sunsets. To me at best the premise comes from a severe lack of vision/creativity.

 

[Drakkith]

No, again, the bizarre part is the idea that they could exist and function without understanding time just because they don't see sunrises and sunsets. To me at best the premise comes from a severe lack of vision/creativity.

I'm not sure anyone is truly advocating a society literally having no concept of time. One must have some concept of it just to actually function. I.E. move around, understand 'now' from 'one footstep ago'. Things like that.

The question is really about timekeeping, not time perception or recognition in my opinion. Does such a society have a calendar? Do they have clocks? What would their society be like without either of these?

 

[DaveC426913]

No, again, the bizarre part is the idea that they could exist and function without understanding time

No. You're overreaching in that conclusion about what's being proposed.

Drakkith nails it:

I'm not sure anyone is truly advocating a society literally having no concept of time. One must have some concept of it just to actually function. I.E. move around, understand 'now' from 'one footstep ago'. Things like that.

The question is really about timekeeping, not time perception or recognition in my opinion. Does such a society have a calendar? Do they have clocks? What would their society be like without either of these?

An analogy: Imagine an alien race, musing about how humans - who evolved over a billion years under the exotic light of a stable yellow dwarf - would know about solar flares. Of course they are aware of concept of flares - that's universal, but would their society revolve around it? Would they wear devices on their tentacles that tell them moment by moment what the radiation level is? Wouldn't that be a weird society? How would they even know when they can sleep outdoors versus indoors? it would be chaos!

 

[Vanadium 50]

The question is really about

I'm not sure there is 100% agreement on this.

There are measures of time that are not related to astronomy. Examples have been given and not challenged, so I don't think this is in doubt.
There are examples of needing to know times that don't involve astronomy either - cooking was given, but there is also how long it takes paint to dry, epoxy to cure, etc. I don't think that anybody seriously doubts this in all but the most trivial way ("But a three-minute egg takes 1/478.7 of a sidereal day!",

I think that definitely answers the original question.

Will different cultures on this planet develop different units for time? Probably - just like on Earth different societies came up with different ways to measure distances and weights. I don't see conversion as some sort of impossibility - we can convert hogsheads to cubic fathoms. Why is this harder?

 

[symbolipoint]

Someone wants to explore the question, and is receiving some thoughts on the question.

You did not see much value in that one.

Think what one SEEs. From one place, to another; the "how much" is length, but we(? or whoever) may see this. How do we see time? People may say time is abstract. Why? Something occurs, like any event. Then while something else does or does not happen, we find a change in the first event. What was this change? Passage of some amount of time. Abstract or not, arguable. We people often understand the idea but how to physically show it, some will feel fine with how it is explained and some others will not feel fine how it is explained.

 

[russ_watters]

Someone wants to explore the question, and is receiving some thoughts on the question.

The claim that time is an abstraction is an anti-mainstream science claim, and such claims are not acceptable here. Such claims are sometimes made in the main forums and are shut down for that reason.

I did over-state a bit when I said the "entire" thread was about this: The OP asks "how do you measure time" and 'how to primitives advance to tell the passage of time' (paraphrase). That's fine and interesting, though it seems like he's asking us to develop his plot for him. The suggestion "maybe they don't" was made in post #3, the implication that lacking external time reference would prevent intelligence in post #10. It's devolved from there into the typical logical extent that maybe time doesn't exist/we created it. That's the part that is nonsense and out of bounds here.

The reason I find it bizarre is due to simple/obvious examples such as V50's boiling egg example. I'm sure you can go back further than that, but it's a pretty obvious example of why a perception/use/measurement of time is critical to even the most basic intelligence. A quick google tells me this is an active area of research in animals, and I'd bet that they will be shown to have a basic grasp of the concept of time too.

Think what one SEEs. From one place, to another; the "how much" is length, but we(? or whoever) may see this. How do we see time? People may say time is abstract. Why? Something occurs, like any event. Then while something else does or does not happen, we find a change in the first event. What was this change? Passage of some amount of time. Abstract or not, arguable.

For non-scientists/pseudophilosophers maybe. For scientists, no. Yes, you et al, are correct at least that laypeople believe that the fact that they can see a meter stick now to measure distance but they have to watch a meter stick over time to measure speed makes distance and time meaningfully different...and for some reason time is less real. That doesn't make it true.

 

[russ_watters]

No. You're overreaching in that conclusion about what's being proposed.

Drakkith nails it:

One must have some concept of it just to actually function.

That seems at odds with what you said previously:

Sure, but still I think it's more important to ask if - on a planet that has no clear periodic cycles of its own - a culture would evolve a need to "keep time" at all,

Was that question rhetorical? It appears to me that Drakkith's answer - the obvious one - is yes. Because it's a basic component of the universe, it's required to make sense of things around us/them.

 

[symbolipoint]

For non-scientists/pseudophilosophers maybe. For scientists, no. Yes, you et al, are correct at least that laypeople believe that the fact that they can see a meter stick now to measure distance but they have to watch a meter stick over time to measure speed makes distance and time meaningfully different...and for some reason time is less real. That doesn't make it true.

In there, you are coming close-to the distinction between what is abstract and what is concrete.

 

[russ_watters]

In there, you are coming close-to the distinction between what is abstract and what is concrete.

Yes, that's the distinction I'm making/my point.

 

[DaveC426913]

It's devolved from there into the typical logical extent that maybe time doesn't exist/we created it.

I must have missed this step. Where did anyone suggest that?

 

[russ_watters]

I must have missed this step. Where did anyone suggest that?

I suppose this is where we start arguing over the definition of "abstraction"? I'll pass. I'll just repeat this:

but still I think it's more important to ask if - on a planet that has no clear periodic cycles of its own - a culture would evolve a need to "keep time" at all, let alone invent a device to track it moment by moment.

And respond again with boiled eggs. Boiled eggs are definitely real/not abstract and they require measuring time to reliably create them.

 

[symbolipoint]

I suppose this is where we start arguing over the definition of "abstraction"? I'll pass. I'll just repeat this:

And respond again with boiled eggs. Boiled eggs are definitely real/not abstract and they require measuring time to reliably create them.

Now we can understand how Time can become less abstract. The idea of the "hour-glass" helps with this.

 

[DaveC426913]

That seems at odds with what you said previously:

Was that question rhetorical? It appears to me that Drakkith's answer - the obvious one - is yes. Because it's a basic component of the universe, it's required to make sense of things around us/them.

In the context of critters living their societal lives, It's not more or less a basic component of the universe than periodic solar flares*. But we don't "keep time" of them.

* which I offer that thy live and die by

I think that's where I see a divergence in opinions here. I am seeing the OP's question - about "keeping time" as more a matter of culture and society than of scientific investigation.

If the critters have science at all, of course they will know what time is. And they will be able to count it. But that doesn't mean the "people" will "keep time".

I keep trying to draw an analogy between Earth time-keeping and Critter solar flare-sensing (cuz they orbit an active red dwarf).

Critters would rightly consider flare activity to be critical aspect of survival - far more than some non-survival time-keeping. Contrarily, we Earthlings are aware of flares and study it in our science, but by and large, it is not part of the mechanism of our society. We don't wear flare sensors on our wrists, or arrange our life schedules around their peaks and troughs.

An ecology that evolved over a billion years to survive based in critical survival clues other than frequent day/night cycles (which Critter don't have) is not that implausible.

Is this analogy too tortured to make the point? Is this getting any clearer than mud?

 

[DaveC426913]

And respond again with boiled eggs. Boiled eggs are definitely real/not abstract and they require measuring time to reliably create them.

No they don't. I already offered several (fictional) ways that a Critter might boil an egg properly without needing to time it:

They might learn to know when an egg is cooked by observation - a subtle change in shell colour, a change in its buoyancy, etc. If it didn't happen naturally, they may have developed clever hacks to facilitate it - say, a simple substance that, when added to the water, changes colour when the egg is cooked, etc.

Or poke a small hole in it and watch what bubbles out.

Frankly, timing an egg is a chancy way of determining if it's cooked, since the method is so dependent on altitude, size of egg, initial temp of water etc. - none of which we can take for granted is constant on an alien world. Better to have the egg tell you directly if it is, in fact, cooked.
I submit that a culture that has not evolved in a day-night cycle for a billion years might find themselves evolutionarily attuned to whole other ways to observe changes. And - like time-keeping has for Humans - it might permeate all aspects of their society.

In other words, I think the predilection for organizing the world by periodic cycles (such as seconds, minutes and days) is plausibly biased toward Earth-centrism, and not universal.

 

[russ_watters]

No they don't. I already offered several (fictional) ways that a Critter might boil an egg properly without needing to time it:
Or poke a small hole in it and watch what bubbles out.

Frankly, timing an egg is a chancy way of determining if it's cooked,

Dave, I'm really having a hard time accepting this argument is serious. I don't know for how many thousands of years humans have been boiling eggs, but in that time(!) we haven't come up with a better way than timing them. As you say, your alternative ideas are purely fictional/speculative. Even if we accept that one of these ideas might actually work it doesn't change the underlying issue, that time is the best/easiest way to do it. The argument doesn't just require that the alternative method be discovered first(!) but that it be discovered and applied exclusively. It requires that beings never even notice the existence of time.

 

[Drakkith]

Dave, I'm really having a hard time accepting this argument is serious. I don't know for how many thousands of years humans have been boiling eggs, but in that time(!) we haven't come up with a better way than timing them.

You have a pot that's X big and you fill it with Y water. Bring to a boil and then throw 3 medium eggs in the water. Once half the water has evaporated the eggs are done. There. Now you're using physical amounts of water instead of units of time to know when your eggs are done. No timekeeping device needed.

Even if we accept that one of these ideas might actually work it doesn't change the underlying issue, that time is the best/easiest way to do it.

Not if you don't have a timekeeping device on hand. Like most people have been without for most of human history. Sundials and other forms of ancient time keeping don't even appear in the archeological record until around 1500 BC. And even those wouldn't really be used for timing the cooking of eggs, as they are too imprecise for such a short amount of time or, in the case of something like a crude water clock, wouldn't be something that most people had in the first place.

Besides, whether something is the 'best' way to do it is irrelevant. People might not have been able to boil eggs to their exact liking every time, but they still boiled them when they wanted.

 

[PeterDonis]

Well, that's what that Star Trek episode was all about.

Stanislaw Lem also had a story about a war between the Dextrorotatory Tups and the Levorotatory Tups.

 

[PeterDonis]

Mercury is basically tidally locked

No, it's not. Its period of rotation is about 58 days and its period of revolution about the Sun is about 88 days.

It used to be believed that Mercury was tidally locked to the Sun but that belief was found to be wrong when spacecraft were able to get close enough to Mercury to make detailed observations, sometime in the 1960s IIRC.

 

[Vanadium 50]

It used to be believed that Mercury was tidally locked to the Sun but that belief was found to be wrong when spacecraft were able to get close enough to Mercur

Not exactly. Mercury is tidally locked, but in a 3:2. A 1:1 is at a lower energy but there is an energy barrier to get there - i.e. small perturbations return to the 3:2, not the 1:1.

The 88 days came from looking at Mercury during the best (optical) observing times. Unfortunately, that is also the times when the same face is visible. It was radio astronomy (at the late Aricebo observatory) that a) didn't have this issue, and b) measured the correct 58 days.

Mariner 10 was years later.

 

[Vanadium 50]

Back to the topic at hand. I was evidently not clear

1. Can time be measured without recourse to astronomy? Yes,
2. Is there a need to measure time that has nothing to do with astronomy? Also yes.,
3. Might the aliens be too dumb to build a clock? I don't know. How dumb are they?

 

[chemisttree]

I would think it would involve a pendulum.

 

[PeterDonis]

Mercury is tidally locked, but in a 3:2.

Yes, technically there are multiple possible tidal resonances. But for purposes of this thread, any but a 1:1 tidal lock will result in the planet's star moving in the planet's sky and therefore giving a cyclical time reference.

 

[DaveC426913]

Might the aliens be too dumb to build a clock? I don't know. How dumb are they?

This is still Earth-centric thinking.

 

[Vanadium 50]

This is still Earth-centric thinking.

Which is a criticism that can be lobbed at any unfavored idea.