Imagine if Earth's atmosphere was shrouded in a perpetual layer of clouds or haze. Enough sunlight gets through to make agriculture still possible, but people are completely unable to see the stars. Thus, the science of astronomy can't develop until the invention of aircraft capable of rising above the clouds.
What technologies would never have been invented, or would have developed differently, as a consequence of the starless sky?
As Vincent pointed out, Navigation will suffer a lot. Everyone would need to travel using land based visual cues (mostly). If they discover a compass, it will help some. But can they see there is a ball of fire that lights up the sky? or is it just a general lightening and darkening as the sun travels across the sky? How consistent is the cloud cover?
Without the ability to see that the things are moving around, the stars, the sun etc. then it would leave a rather insular point of view about the planet.
I also think for navigation of ocean's that very tall light houses would be common, with special markings so ships could travel farther out to sea and still be able to navigate and know their location. This would also encourage the creation of better optics as well as tower building technology. The ability to draw good maps to scale would be extremely valuable.
Calendars are going to be hampered a lot. if the only time you have is 'light' and 'dark', no moons, no year, no stars to notice differences? Or is there a moon that can penetrate the clouds near full? if so that could cause a lot of speculation about the the 'big' light and the 'small' light. It would also help set passages of time. Mythology would certainly be a lot different.
Following up with bowlturner's last sentence: "Mythology would certainly be a lot different." This might actually complete reshape the entire history of mankind, even from biblical times. The change to mythos might very well cause faction rivalry to form completely different, forming a wildly different map of the world. And this is long before it affects technology.
Here's something few others have pointed out: religion. The main basis for science arising and becoming as widely accepted as it is today is astronomy. The early astronomers (Galileo and his contemporaries) pointed out that the Sun is fixed and the Earth revolves around it; they were shunned at the time for heresy and blasphemy. If we didn't have their theories, it is entirely likely that religion would dominate our lives today.
Furthermore, it is fairly likely that Christianity would be the dominant religion by far. It is as dominant as it is today because of the empires of Europe, of Britain, France, and Germany, with some Spanish influence. Without astronomy, you don't have anyone rejecting religion out of hand, so the influences Christianity left would have remained, leading to it becoming far more dominant. Other religions would still be observed, but in smaller less pronounced pockets.
Timings would also suffer. Calendars and, importantly, leap years are based on our observations of astronomical phenomena. One month (word origin: "1 moon" > "1 moonth" > "1 month") was originally defined as one cycle of the Moon, 28 days. Over time this definition has been revised to keep up with our other definitions, such as seasons.
Leap years are based on the movement of the Earth around the Sun. As detailed in this article, the Earth actually takes 365.24 days to make one full revolution around the Sun, so adding a day (February 29th) every 4 years keeps us about in sync. If leap years hadn't been invented but some form of rudimentary calendar had, people would get very confused as, over the years, winter moved to summer and summer upped and left to take winter's place.
You are, however, right in assuming that we would eventually make these discoveries. As I see it, this could happen at one of two points:
However the discovery of space is made, there's a lot of discoveries to be made until this society is anywhere near our understanding of the universe. They'll end up several hundred years behind on astronomy, but could well do better than us in other fields, having had more time spent on them because of not spending said time on space exploration.
For questions like these I honestly like to use the tech trees from the civilization games. Its easy to point out that Navigation, as the obvious example, will be impacted. What is harder to discern is the downstream impacts, and that is where a chain like this (albeit a simplistic one) is very useful. Here is an image of the chain.
My answer presupposes one thing: The cloud cover is completely and utterly constant. There are no breaks in the clouds, or at least they are so rare that they are essentially legends that are passed from generation to generation that most never see. I suppose this could also allow for Peter's comment about mountain top monasteries. The short version, the clouds never part or it is exceedingly rare.
As a disclaimer...I am not going into every possible technology...just attempting to demonstrate how things can be looked at differently. I will focus this primarily on early technologies because you can then chase the rabbit down this hole yourself.
Agriculture: While agriculture can still exist per your description it would be negatively impacted in this world. This has huge downstream impact. Agriculture is the basis of all human civilization. It allows for larger cities in which specialization can come to be. This has lasting and on-going impact on the rate at which civilization develops. For example it would be reasonable to assume that humans remain hunter-gatherers for much longer. You can likely use this phenomenon to restrict development to your hearts content...we could remain cavemen. At the very least things get started more slowly.
Navigation: The skies have been used for navigation for as long as humans have traveled. I am not speaking only of ocean navigation but overland as well. While you can certainly still tell where the sun rises and sets things are far less precise and night travel is completely blind.
Religion: This I am including as more of a social development but I feel it is relevant. With no view of heavenly bodies it is reasonable to believe that they do not become deities. There are a few routes you can go here. Concepts like animism and nature spirits could play a larger role. The impact of this is that some early advancements particularly in stonework, mathematics and construction were a result of monument building. That is not to say that religions would still not create large structures but nature related religions are not generally historically known for creating monuments like this. Again, with a change as fundamental as permanent cloud cover you can kinda go wherever you want with this. I am just trying to illustrate the possibilities.
Calendar: Calendar development on earth developed exclusively based on heavenly bodies. A calendar is still useful and would likely be developed, but what would it be based on? Seasons. Sure that can work, but it lacks the precision of using the skies. It also requires other technologies for example temperature readings before it can be anywhere near accurate.
Notes: This is a pretty fundamental change to how the world works. Removing or minimizing the relevance of heavenly bodies in the day to day life of early humanity could cause things to develop radically differently. In the end I don't think you will see technologies that fail to come to be. The timing of them showing up will surely change as will, by necessity, the order in which they are created.
Very interesting concept and one that allows you to tweak the world to your heart's content. Just try to maintain a logical consistency, and if you are unsure whether two developments fit into the world you are creating those would be great questions for the site.
Astronomy could develop anyways, depending how high and how dense clouds are - possibly monks living in monasteries high in the mountains above most of the atmosphere would be able to see the stars - it would be even more spiritual experience for them.
We will probably still being nomads hunting animals and collecting foods.
Maybe I'm putting to much value or astronomy for saying this but in my opinion almost every single achievement of the humankind couldn't be done without the help of astronomy.
The control of the seasons and the creation of calendars with allowed the first humans to became sedentary were thanks to astronomy.
The observation of the positions of the stars in the sky, during what will became the year, was the first sign of season or a calendar that the humankind had. It allowed the first human to establish a settlement and cultivate plants.
If we couldn't became sedentary, we'll be expending to much energy on surviving and probably we will not get much more advances than small tools made of iron or stone and the wheel.
