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Kerfudamapa t1_ix8fggy wrote

I believe It all comes down to the angle of light hitting it and being reflected to your eye, and the amount of light that is being reflected really.

In sci-fi, we'll see a spacecraft in detail because that's what the audience is expecting but, more than likely, in deep space with a vast amount of distance to the nearest star you probably wouldn't be seeing much.

However, the same goes for a moon-sized spaceship that is sitting in the earth's shadow in our own solar system. If there's little/no light hitting it that is reflected to your eye then it's effectively invisible to us.

The point being, while all objects do emit light (usually in the infrared; Google black body radiation) it becomes increasingly difficult to see reflected light from a small source point, onto a small object, that you are well distanced from. Maybe if you plan on venturing into deep space you should bring a floodlight or two?

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seanyseanerson t1_ixaisic wrote

So to travel safely in space I guess the ship would have to emit an insane amount of light in all directions to properly monitor for potential collisions. The odds of one are low I guess, but you'd want to know if an object was heading your way.

Perhaps a sort of infrared sonar would be more useful and energy efficient? I dunno.

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Arusht t1_ixb2ubr wrote

Like.. insanely low. So low, that I have no idea where you’re at in the world, but if I got into a car right now, closed my eyes, and drove in a straight line.. I would probably have a better chance of hitting your house.

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imtoooldforreddit t1_ixbi4oj wrote

Space is really empty

If you're picturing dodging like in star wars flying through asteroid fields, that's not what space is like

In our asteroid belt, average distance from an asteroid to the next closest asteroid is about 100,000 miles

For the probes that have gone through the asteroid belt, they had absolutely no way to know if there was an asteroid coming, because the risk of even a single one was basically negligible.

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Saerali t1_ixbsyqj wrote

Oh didn't know it was THAT spread out. How packed would saturn's rings be ?

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Exatex t1_ixbxwxj wrote

Very packed - so packed that although the rings are just 10-100m thick, they block most light going though them

run fact edit: Saturns rings are some of the thinnest things known to us. They have a diameter of ~1 million kilometers.

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tizuby t1_ixciixl wrote

You're off by a factor of 6 with average asteroid distance - and that's just in the most dense parts of our asteroid belt (about ~1,000,000 km or ~620,000mi).

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_AlreadyTaken_ t1_ixb1cok wrote

Radar but space is a lot of empty. The biggest problem is likely micrometorites and high energy atomic scale particles chewing away at you.

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kendiggy t1_ixcgntm wrote

SONAR (SOund Navigation And Ranging) wouldn't work since sound relies on having an atmosphere or body of water/molecules to travel. RADAR (RAdio Detection And Ranging) would be much more effective because radio waves can actually travel through space.

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seanyseanerson t1_ixcsfrh wrote

Thank you. I was thinking of something that sent out pulses of light to read reflections in the same way sonar does but hadn't thought that radar already does the job just fine!

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Webs101 t1_ixckas4 wrote

If you’re flying in space, you’re not relying on the visual spectrum to avoid collisions. Radar will work just fine.

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Blank_bill t1_ixaaher wrote

Just scan ahead of you with a 1meter laser as it boils off a mm of whatever you'll see it.

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Kerfudamapa t1_ixcsgwj wrote

I mean, you'll see a laser reflected back right? Is there much detail to be observed this way?

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Blank_bill t1_ixd9q8e wrote

Depends on how powerful a laser it is, if it's strong enough to ionize the material a spectrometer will give you an idea of what it's made of, if not the glare will only tell you something is there.

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