sight is necessary to understand the cosmos

If with sight you mean "capability of elaborating electromagnetic waves in the range of the visible spectrum", the statement is simply wrong. We have just got the report that the first image of a black hole event horizon was taken thanks to observation in the radio-frequencies.

So, no, sight is not strictly necessary to understand the cosmos. It is true that the broader spectrum one can analyze the more information can harvest, but lacking a fraction of the spectrum is no showstopper.

Also on a human scale, several space missions have succeeded in exploring space without having a camera for exploration. Just think of the Sputnik: it didn't have a camera, so technically it was blind.

And even we don't need to view something to understand it. Whoever takes calculus at a university level can describe your with extreme precision the properties of a multidimensional surface without visualizing it, just by studying the function representing it. And, if you object that calculus is not exactly a standard knowledge, even visually impaired people get a good understanding of the world without seeing it.

"We need to see things in order to accomplish even the simplest task." is quickly debunked by even the briefest consideration of lives of blind scientists here on earth.

Human's lack of natural ability to see x-rays has not diminished our capacity to detect, measure, utilize, and interact with x-rays.

If a society develops to the point of being able to produce electronics and radio technology, then they will have little trouble "discovering" the stars. If they cannot 'see' something naturally, then they will be able to build tools and systems to translate emissions into a data-stream that they can interact with. Exactly the same as humans have done.

Can't see something in nature? Observe its effects as it interacts with something else that you can detect, and use that property to study the phenomenon.

Can't see x-rays? Observe how they cause some materials for fluoresce when struck with x-rays, and use that to explore, study, and refine how you can interact with them.

Can't see anything? Observe how light interacts with specific electronics, and develop a photo-diode or similar to construct tones or vibrations that you can observe, and build that into greater and more refined sensing technology.

You may wish to consider the fact that earth has blind astronomers. There is far more to space related research than being able to see it with your own eyes.

To reinforce how a human's visual senses are just a small part of how we observe the world, consider primitive interactions with fire. What are the main points to observe about fire?

• It is bright


• It makes a loud crackling sound


• It emits heat that can be felt at a distance, and a LOT of heat that can be felt if touching it directly.


• It emits smells based on what is burning and how it is burning


• It changes the look and texture of material it consumes

Two of those points involve sight, three if you count smoke, and four of the five directly involve other senses.

Sight may be useful in learning about fire, but is not required to learn and understand it from a scientific standpoint.

Vision isn't even all that involved in learning to make fire. If you've ever tried using friction and sticks to start a fire, what is the first thing you observe? Do you see that you're beginning to "start a fire"? Of course not, as the first thing you'll observe is that rubbing things can make them warm.

As an experiment: Close your eyes and rub your hands together really hard and fast.

Open your eyes and let your hands cool off, and repeat the same experiment, but this time watch it.

Did being able to see it make it any easier to observe the heat?

Probably not - Because human vision doesn't do much with regards to heat...

So go back to starting a fire with sticks. What is the next thing you observe as you come closer to starting a fire?

• See sparks? No
  


• 
  Smell a change in the wood? Yes.
  

Unless your sense of smell is especially bad, even by human standards, you will smell a change before you even see wisps of smoke. And by that point you will be able to feel a major change in the heat (And heat is related to fire...) far more than you will be able to see something that looks like fire...

If you don't know any thing about starting a fire from sticks, then you might observe that it sometimes becomes easier to start the fire if you feel just the right amount of wind coming from the right direction, and you can quickly learn more about how air is related to fire.

But that was all just how you can observe fire without relying heavily on vision. What about something else important to really advancing science, like electricity?

Primitive interactions include things like:
- Static sparks: See the light, feel the shock.
- Electromagnetism: Moves things, which may be felt or heard
- Current through a wire creates Heat long before it creates visible light...

-TL:DR -

Vision very much helps with the advancement of science. (And would make for a far more rapid advancement through early metal-ages with far fewer nasty burns...) But it is very far from a requirement for an individual or even a species to achieve great scientific advancements.

[Ironically, signing off: - A Visually Impaired Scientist...]

I think your aliens would be better adapted to space exploration than humans are.

Echo location is a spatial sense. It gives you directions and distances and via Doppler shift changes in distances. A species with a sense like that would be able to understand something like the solar system much better than a species that relies on a planar sense tricked up to boost hand eye coordination so that you do not fall out of a tree.

It also maps directly into radar which works with exact same principles and has exact same limitations and advantages. Except it works in space. And radar is a human version so it needs a conversion to something us poor humans can understand. Your aliens would do much better since they would understand all the data about spatial data and movement directly.

You'd need an "echo display" that gives the proper audio response based on computer data and the sounds it receives but apart from being larger and lower resolution that visual analogues it is not that complex.

Generally changing vision to echo location loses things useless for space exploration such as ability to see detail and color and gives useful things such as better spatial sense and sense of motion.

And they also have a superior magnetic field sense. They could sense the planetary magnetic field, large ferrous objects moving in it, the direction the solar wind is coming from. They'd probably know where the sun is even at night.

In space they'd probably feel the solar magnetic field. Certainly the ship could have systems to allow them to do so. And to feel the movement of the ship and even the movements of the planets. Or other ships. And then there is the glorious stuff elemtilas talks about.

Of Course!

That is, assuming these people have the intelligence, resources, sciences, temperament, desire, technological advancements, etc., etc.

If you can see this in the sky:

And something like this orbits your planet:

Then you're more than equipped to get out and take a good look at this:

All of those things should be "visible" to a species who can see magnetic fields the way we see light.

Yes, measuring instruments are more important than senses... and you can have glasses for light polarization

I think the crucial aspect of your alien species is whether or not they are able to build complex measuring instruments and transmit knowledge.

A very important difference between Aristotle and Galileo is the emphasis the latter put on measurement (rather than their intelligence or available senses). At the time, European manufacture was advanced enough to build the instruments that he and others would require to build up their calculations, and later develop the theories that formed the core of mechanics.

The history of space travel would be very different for your species, depending on the way they are able to perceive gravitation, velocity, mass, etc. For example, the early optical telescope would be useless to them but they would have the capacity to notice the effect of the orbit of the moon in the Earth's magnetic field.

From this humble beginnings, they could develop a different type of orbital mechanics perhaps at a slower pace, perhaps faster than humans did. Unfortunately we know very little about magnetoreception to describe a mechanism in detail, but we do know that in some materials "magnetic fields can change the way the charged particles (mainly electrons) respond to the light electromagnetic field". On one side, some phenomena that remained a mistery to humans for millions of years would be a part of everyday life for your aliens...

On the other side, with enough tools and technology, your aliens could build themselves some device to perceive light talking advantage of the polarization of light in a similar way in which we have built a ton of things to measure magnetic fields.

PD I don't think sound is relevant for space travel because it doesn't travel in a vacuum.

I think my answer is: Yes.

Given only echo location it is not possible to discern anything in space or to orient oneself in space. However, to develop space travel, I suppose these aliens would require a high level of technological sophistication anyway. Otherwise some bat would just fly in the direction of "up" and suffocate. Word might get around that this is a bad idea.

If they first develop machinery to enhance their abilities sufficiently they might also realize that space is not just infinite emptiness.

A possible riff off of an echolocation like solution would be to release hundreds of small disposable probes that explode on impact with anything. Then light sensors the aliens have built could read the incoming data, and map out what is around them as a data point in 3D space. They would possibly be able to visualize any object based on their ability to memorize the coordinates reported by their machine, or have the machine create a model in UV or sound that they could "see" or understand. It's kind of like how a cats whiskers provide acute and specific sensory feed back from a specific point which allows the cat to make adjustments to their location with high precision almost instinctively.

The most difficult part would be knowing to look into the sky, when seemingly there's nothing there.

If they knew, they'd undoubtedly have the capacity. Any light that they need to detect, they could convert into ultrasound, magnetic fields, haptic feedback or digital scent. Humans already do this - every sensor measures something we can't perceive with our senses (e.g. atoms, deposits of metal, black holes) and translates it into something we can.
In our world it may be difficult to develop a scent-display, however we are primarily visually-oriented and - across our species' history - invested considerable resources into inventing writing, paper, printing presses, photography and graphic displays. A blind species would invest as much or more resources into other senses, possibly discovering engineering techniques we don't have sufficient incentives to discover.

The larger obstacle is demand. A significant reason why humans value space travel over other scientific discovery is wonder at the stars that we could see, unaided, for all of human history. Mythology of the stars and Moon abounds across continents and millennia. The largest strides in space exploration occurred at the height of Cold War superpowers displaying their influence - it's hard to imagine the Soviets and NATO competing to prove obscure mathematical theorems.

Also, space could only be discovered after the invention of accurate light-sensors (which would be prioritized as much as Smell-O-Vision); so only at our era of cheap technology or later. So no centuries of myths about the stars, spurring these creatures to explore. Only a curious observation whose meaning can't be easily explained to a non-technical bat - similar to obscure mathematics.

So discovery of space could begin with an inventor in the modern day failing to market his useless 'photo-braille device', and accidentally discovering something mind-bendingly impossible.

Others have covered how they sense the universe. Two other factors exist which you will need to resolve to get the necessary technology:

Collaboration
Any significant technology requires collaboration, and storage of knowledge. For us, this is heavily reliant on written materials, diagrams, etc. They will need an equivalent for this. I don’t think speech will suffice to handle building the required infrastructure. Braille (or some similar concept) is a possibility - not sure how well it works for diagrams? - but would be much slower to work with, so this should be taken into account.

Precision & Resolution
Our vision allows us to perceive the universe in very high precision, and this precision is required for us to build the precision tools (that build the tools that build...) that build the necessary scientific and engineering technology.

I believe echolocation is much lower resolution, and there may be physical limits affecting its accuracy. Smell has a much much lower resolution. Touch has limited resolution, and is not appropriate for measuring many things (like the position of a spinning saw blade, or a oxy-torch...!)

This would make the development of the necessary technology much more difficult.

But, when talking about space, sight is necessary to understand the cosmos.

Really? Or is it just necessary that they be spatially aware?

Open your mind. It will take more work on your part, but you can explain it.

We cannot see X-Rays, but we discovered them... and then figured out how to make machines/devices that represented them in a form that we could understand (see them on photographic plates). And then discovered how they could be useful.

Note that X-Ray radiation killed a lot of the early scientist studying it (via cancer) but that didn't stop them. We learned X-Rays, and then we learned new stuff, and now we have MRIs, use sound waves to measure blood flow, etc.

The sun is easy to "see" without "vision".

They would feel the warmth, even if they couldn't see it. (Or feel effects from it if you want it really far away)

It might take longer to "see" the stars and moon(s) than the sun... but eventually a sentient species of sufficient intelligence would figure it out. First they figure out it is there, then they (eventually) figure out how to get a better view (however you decide that is possible).

Almost the entire current understanding of the cosmos is not based on visible light, but on the entire electromagnetic spectrum, of which visible light is a tiny fraction. Even our incredibly primitive space ships today are not navigated by sight.

So no, quite obviously space flight does not require sight when even beings who can see don't use that sense to conduct space flight.

The more interesting question here is whether beings without sight would have ever been interested in the cosmos at all. For as long as we have written records, people were aware of "the sky" and that there is something beyond their reach, because they could see the stars. A species relying on echo-location, for example, would have no such awareness that space exists at all.

However, just like us humans, they would sooner or later invent technology that goes beyond their own senses. We created x-rays and radar, they would probably invent some kind of visible-light sensor.

It's well within the realm of possibilities. Vision is only necessary for us to because it is what we know. If your alien race's dominant senses are as effective for them, as sight is for us, then they could, quite possibly "sense" the nature of the cosmos in their own way.

As humans, our technology has allowed us to overcome our physical limitations over and over again. If your aliens are intelligent enough to create sophisticated technology. And it evolves similar to ours, then (I would think) lack of sight should be an easy hurdle to jump.

They would develop the necessary technologies in a very different order than we did, but I think they would get there.

For example, they might develop electricity and magnetism much like we did, and then radio, and then radio astronomy. That might be their first clue that stars and planets exist. But I think they'd do it.

The only issue I see is that much of our early science was inspired by astronomical observations. They wouldn't have that inspiration. Would they have something else that leads them forward?

(Contrary to what others have suggested, they would probably not be usefully able to understand radar returns by translating them to sound. Light travels almost a million times as fast as sound, so your targets would have to be a million times as far away for that to work. To get binaural perception that sounds anything like what you hear from ears 15cm apart, you'd need a pair of receivers 130km apart. They wouldn't build it until they already had at least crude radar.)

Just wanted to add one minor thing that I didn't see mentioned yet.

One of the current major issues with long-term space travel for humans on the mission to Mars- for example- is the deterioration of our eyes during prolonged durations in micro gravity. In the relatively short amounts of time astronauts spend on the ISS, many of them come back with near-nearsightedness that lasts months or years after their trip. It is logical to predict that if the astronauts were in space even longer, it the negative effects would worsen and could become permanent to the point of blindness.

All that being said, if bat creatures don't rely on juicy gravity eyes to see, but rather echolocation etc, then they won't suffer this induced blindness during prolonged travel which could be a huge advantage over astronauts relying on visuals.