Alternate scientific development on a cloud-covered world?

[fishfry]

I've always wondered about the following.

We know that the ancients looked up at the stars, and drew figures in the sand, and invented plane geometry, and trigonometry ; and in the case of Archimedes, even the rudiments of calculus; at least in terms of understanding that infinite processes can be used to understand the world around us.

Now I wonder what would have happened if we lived on a planet that was identical in ever respect to our own, but which was covered with clouds.

So Galileo could still roll a ball down an incline to discover gravitational acceleration. But the ancients could not have looked up at the stars; or seen the sun or the moon. Galileo could not have seen the moons of Jupiter. Nobody would know that the sun rises and sets; only that the sky alternates between bright gray, and dark.

How would math and physics and astronomy have progressed? Ptolemy couldn't compute epicycles because he couldn't look up and see the movements of the planets against the background of the stars.

Yet eventually, everything we know would have been figured out. Eventually we'd have mastered electricity and figured out gravity and built particle accelerators and developed modern mathematics. We'd have built flying machines, and as soon as we did that we'd have gone above the clouds and discovered the sun, moon, planets, and starts.

But it would have taken much much longer, and it would be very different.

What would it have been like? Do you think we would eventually have figured everything out? Or was the early experience of being able to actually see things, not just imagine them, an essential part of humanity's intellectual development?

[webby]

We actually run this hypothetical scenario as the first tutorial in the first year Astronomy course at our university as a 'get them thinking about how to work things out' type of exercise. It's similar to the second exercise on this page (the one about the fictional cloud-covered world of 'Mog').

The hard part is getting the students to stop thinking about what they know about the earth and make a genuine attempt to come up with alternate models of the world (that's the point of the inquisition role). Explaining the seasons is a particularly interesting one.

[eSOANEM]

IIRC at the time, the only evidence for Newton's inverse square law for gravity was that it explained Kepler's laws. It wasn't until the Cavendish experiment over a hundred years later that an experiment which could test it in the lab was performed. Of course, the Cavendish experiment was actually performed to find the value of G and the density of the earth so probably wouldn't have been performed for much longer without Newton's laws of gravitation.

So yeah, gravity would have taken a very long time indeed.

[idobox]

Geometry might have taken a little longer to develop, but it still would have. People needed to measure surfaces, heights and all that kind of stuff, and would have found tools to do it.
And calculus could have been invented while trying to solve a number of problems, for example the trajectory of cannon balls.

Also, the first manned flight happened in 1783. After a few decades, people would have managed to rise above the clouds. The laws of gravity could have been discovered by that time "only" a century or so after it actually happened.

[eSOANEM]

Also, the first manned flight happened in 1783. After a few decades, people would have managed to rise above the clouds. The laws of gravity could have been discovered by that time "only" a century or so after it actually happened.

How long was it after the stars were first seriously observed that Kepler's laws were discovered?

A few thousand years.

Now, even allowing for a much larger population (as would be the case if they started being observed around 1800) and so a faster rate of discovery, it would be very optimistic to expect Kepler's laws to appear after as few as a hundred years. Once Kepler's laws were around (which would be 2000 at an optimistic guess) Newton's laws of gravitation would probably follow quite quickly. Seeing as SR would probably not have been adversely affected hugely by cloud cover as much, GR would probably follow quite quickly after Newtonian gravity.

[idobox]

How long was it after the stars were first seriously observed that Kepler's laws were discovered?

A few thousand years.

Now, even allowing for a much larger population (as would be the case if they started being observed around 1800) and so a faster rate of discovery, it would be very optimistic to expect Kepler's laws to appear after as few as a hundred years. Once Kepler's laws were around (which would be 2000 at an optimistic guess) Newton's laws of gravitation would probably follow quite quickly. Seeing as SR would probably not have been adversely affected hugely by cloud cover as much, GR would probably follow quite quickly after Newtonian gravity.

19th century scientists without the weight of the church and its geocentric view should definitely go faster than middle ages monks or greek philosophers. It was the era of Watt, Maxwell and Boltzmann.

[eSOANEM]

I'm not so certain. For one thing, without astronomical observations, it would be "obvious" that the planet in question was the centre of the universe and so a geocentric view would persist far far longer. Furthermore, even taking that into account, cutting thousands of years of progress to even a couple of hundred years would require over ten times the rate of research. This is probably just about achievable but, getting it down to even 100 years (such that Newtonian gravity appeared only just before SR) seems like you're requiring absurdly fast research/

Furthermore, I don't think we can count on having the same scientists doing similar things or being as good at what they did. Changes in the order of discovery of some things may have meant some scientists never really got into it and never made their contributions. So really, I think the only assumptions we can make about rate of progress are ones based on population in that, in general, a planet with a larger population will progress faster than one with a smaller population.

[idobox]

It's of course very difficult to predict what would happen, but I don't think geocentricism would even exist. To think Earth is the center of the Universe, you have to be aware there is a universe.
Imagine the shock and surprise of the first people to see above the clouds, discovering the sky changes color from black to blue, that there is a freaking ball of fire up there, as well as a huge rocky ball, and countless shining dots. Every scientific minded person on the planet would be fascinated by these phenomena. Within one year, they would realize that the stars appear to move, and it's related to seasons. They should also guess pretty quickly that there is a link between the moon and tides.
I don't know if the technology was good enough to measure planetary distances through parallax, especially from a balloon, but if all the smart guys on the planet studied the problem, it wouldn't take long to come up with heliocentrism.
I mean, heliocentrism was first proposed in 270BC. Scientists would have realized quickly that the sun is incredibly bigger than Earth, and that's easier to explain the motion of stars by having the Earth spin and precede rather than by having the whole sky move.

[eSOANEM]

Before flight above the clouds (we're assuming of course there's cloud cover above all easily scalable mountains), they would have deduced their planet was round and roughly spherical (there are lots of methods for this). They would also see that the cloud cover changes.

From this, the most obvious model is that the world is a ball surrounded by another ball which has things moving on it (the clouds). In this pre-above-clouds-flight world, the world is very definitely the centre of the cosmos.

Once they fly above the clouds, they already have a geocentric model, they just don't know about a load of the other stuff. They'd then extend their previous model to make the clouds-ball actually a cloudy-layer and also to add another sphere with the stars, planets, sun and any moons on it.

As you say, they'd pretty quickly realise that the moon was linked to the tides and that the sun corresponded with day and night (which should still have been observable below the clouds). They'd probably, like the ancients, distinguish between stationary stars and moving planets.

Now, telescopes would have been invented for use on the ground at sea so it seems reasonable that someone would eventually take one up in a balloon. Without large primary lenses however, they probably would not find many more objects visible in the sky than were visible previously, they'd just make them larger. You'd also get people drawing star maps.

It wouldn't be too long before people noticed a few planets which were frequently not visible and moved a lot (the actual planets). Mapping their orbits must necessarily take a significant amount of time because they are not always visible and would require at least one of that planet's years. Given the level of geometry around, it wouldn't be long before they noticed all theses planets' orbits lay roughly in the same plane however, at this stage they would still be thinking geocentrically but they would now be at a similar stage to Copernicus and should quickly switch to a heliocentric position given other advances.

Once they have heliocentricism, Newtonian gravity (or something very much like it) probably would not be far around the corner seeing as by now, electrostatics would have been discovered and well developed.


...


Now the main hold up seems to me to be in mapping the movements of the planets. Assuming a solar system similar to ours, then this would take something on the order of 30 years as an absolute minimum. This is because Saturn, the furthest out (and so longest period) planet observed in ancient times has an orbital period of ~30 years. Of course, you'd need well over one orbital period to properly map the planet's orbit (particularly as it isn't particularly bright all the time) so, even requiring as few as three orbital periods would take at least 90 years.

Now, they might spot a planet with a longer period than Saturn before developing heliocentricism in which case this will take longer.

Anyway, I think this should show that expecting Newtonian gravity in under 100 years (after flight above the clouds) is absurd and two-hundred years would not be unreasonable.

[idobox]

Mars orbit is about 2 years, Venus and Mercury are even shorter. With the telescope they had, they could observe Jupiter and Saturn's satellites which have significantly shorter orbital periods. And knowing other planets have moon is a serious indication that Earth is not special. The orbital period to distance rule could be found in weeks, or months.
They would have realized very quickly that the sun is much larger than Earth, and having observed small bodies orbiting larger ones, the idea of heliocentrism should arise quickly.

Sure, it would have taken some time to confirm Jupiter and Saturn followed the same rules, but you don't need it to get Newtonian gravity.

About the geocentric view, they wouldn't have had a true geocentric view, with Earth at the center of the universe, because they would consider the whole universe to be Earth. A system that stops a few kilometers above the ground.
As scientists discovering the universe is much bigger than they thought, why should they assume everything they see is at the same distance? They would try to measure distance through diurnal parallax, and would fail for the stars, concluding they are absurdly far away, but they would have been able to measure the distance to Mars and Venus, and infer the distance to the Sun (which was done in 1673).
If you look at the history of heliocentrism, you will find a few astronomers who came up with it, but discarded it because of faith or philosophical problems. The idea of heliocentrism is not that hard to have, especially if you already use the scientific method.

On the other hand, astronomers proving the truth of heliocentrism, and the error of religion probably helped promote the scientific method and skepticism, and it is difficult to predict how science would have evolved without these results that have little practical applications, but large philosophical ones.

[eSOANEM]

Mars orbit is about 2 years, Venus and Mercury are even shorter. With the telescope they had, they could observe Jupiter and Saturn's satellites which have significantly shorter orbital periods. And knowing other planets have moon is a serious indication that Earth is not special. The orbital period to distance rule could be found in weeks, or months.
They would have realized very quickly that the sun is much larger than Earth, and having observed small bodies orbiting larger ones, the idea of heliocentrism should arise quickly.

Sure, it would have taken some time to confirm Jupiter and Saturn followed the same rules, but you don't need it to get Newtonian gravity.

Orbital period/distance rule could certainly not be deduced quantitatively in weeks because, in order to deduce the law you need to first measure orbital period. To accurately measure this, you're going to need to not only see how long it takes to return to its starting point but also confirm that its motion from that point is the same. To do this properly will take at least two orbital periods which means that, even if you discount planets further out than the asteroid belt, you've got to allow at least 4 years.

Now it's possible that our Kepler would have deduced the distance/period law from just 3 or 4 data points and use this to predict the period of "Jupiter" and "Saturn" however, as these predictions would not be verifiable for at least 30 years, I suspect that even if the law did spring up early, it would initially be viewed as pointless pontificating and so, until its predictions were verified, I think it would be unlikely for Newtonian gravity to be found.

So, assuming orbital periods and distances start being measured as soon as there's the first flight above the clouds (which seems optimistic), that Kepler's laws are found as soon as there is this data for all the planets up to about Mars (again, this seems unlikely seeing as this data was readily available a long time before Kepler found them) and that Newtonian gravity is found as soon as Kepler's third law is experimentally verified (again, this seems unlikely as it is by no means clear to me that Kepler's second law would have been verified at this point as it would have to have been to deduce Newton's laws of gravitation), we arrive at an absolute lower limit of 34 years after the first flight above the clouds.

Now, as discussed above, I think we can reasonably add a few more years to the time before the stars (and planets) start being properly mapped and their motion timed etc. which will raise that to ~36 years. Then, "Kepler" would probably take a while to deduce his law and would probably wait until he had more than 3/4 data points meaning that (assuming he still does not wait for data from Saturn) taking us to ~55 years. Then, it seems reasonable to raise this to 60 years before Newtonian gravity could reasonably be arrived at (allowing 5 years to develop Kepler's laws and then Newtonian gravity from the data from the planets up to Jupiter).

60 years is vastly less than my initial estimate of a couple of centuries, it seems I was too pessimistic and it is not unreasonable to expect Newtonian gravity within a century of the first flight above the clouds.

This would mean that GR would probably not be significantly delayed (particularly as gravity would be an area of current research as much as electrostatics).

Now, they probably would have developed the idea that Weight=mg already from trying to calculate the ranges of cannon and suchlike, it would be interesting to see how long it was before someone realised this was the same force as that acting on the planets.

[yurell]

We actually run this hypothetical scenario as the first tutorial in the first year Astronomy course at our university as a 'get them thinking about how to work things out' type of exercise. It's similar to the second exercise on this page (the one about the fictional cloud-covered world of 'Mog').

The hard part is getting the students to stop thinking about what they know about the earth and make a genuine attempt to come up with alternate models of the world (that's the point of the inquisition role). Explaining the seasons is a particularly interesting one.

We did that too! The guy who wrote that page (Paul Francis) was our lecturer ... it was great fun.

[idobox]

By the end of the 18th century, 4 moons of Jupiter, and 7 moons of Saturn were known, all of which have orbital periods of a few days. Even if it took 20 years before systematic observation was done, results could be obtained in a few months.
Newtonian mechanics should have been developed by that time, as well as calculus. For ballistic, of course, but also early machines that needed to deal with inertia, like clocks.
If Newton hadn't studied the planets movement, other people would have found out his laws by observing balls on planes and that kind of problems.

And people wouldn't need to wait for Kepler's law to be confirmed with 6 planets and 11 moons rather than 4 planets and a few moons before they postulated the existence of an attractive force, especially at a time when electrostatics was known.

But mostly, all the greatest minds of the time would be working on the subject, a bit like what happened at the beginning of quantum mechanics.

[tomandlu]

This is a fascinating topic, and everyone in my family has expressed some sort of opinion. I like a friend's suggestion - navigation would have been the driver for most development, which, without stars, means emphasis on optics, magnetism, communications, and really, really tall lighthouses... he postulated that the discovery and use of electricity would have come much sooner.

[idobox]

I hadn't thought of that.
Without star navigation, sea travel would have been limited, with most of the traffic following the coast, and that for a very long time. With reduced communications and trade, ideas would have traveled slower, including things like the alphabet or Arab numbers. Empires like Rome, 18th Century Spain, or 19th century France and UK could never have been the size they were, and without the ability to transport large troops far away, wars would have been significantly less common (if you fight only with your close neighbours, you have less opportunities to go to war).
As a result, I expect metallurgy would have progressed slower, and the countries being richer (wars are expensive), craft and trade would have been more developed, causing feudalism to disappear faster, and machines to be invented earlier. The industrial revolution could have started much earlier.

[bigglesworth]

Places like Australia may never have been colonised without navigation by the stars.

[scarecrovv]

Since celestial navigation is possible from airplanes (and was routinely practiced in World War II, I believe), trans-oceanic aircraft may have been developed before trans-oceanic shipping. Since runways are hard to come by in areas where the people haven't seen airplanes before, and helicopters have much more limited range, it's likely that colonization would have started along coastlines (but with sea planes, not ships) and in places with salt flats and dry lake beds where you can land an airplane on natural terrain. Perhaps ships (carrying balloons on tethers, or helicopters, depending on the height of the cloud tops) would have come later, but building ships capable of crossing oceans and carrying aircraft would be a large investment for no immediately obvious gain before it was even confirmed that there was anywhere interesting for them to go.