"There are many many mindboggling facts. My favorite one is always cold welding. Due to lack of oxygen - and in consequence lack of corrosion - you can put two pieces of metal together in the vacuum of space, and they will permanently connect, forming a single piece of metal almost instantly." - myhamsterisajerk https://www.reddit.com/r/AskReddit/comments/vzlxcd/whats_a_fact_about_space_which_will_always_blow/

"Imagine our entire solar system is the size of a beach ball. And you put that beach ball on a beach on the US east coast. The closest "beach ball" to us in the galaxy is on a beach in Portugal. We sent a probe out decades ago and as far as we know, it has only just recently reached the edge of our own beach ball." - seamustheseagull

"Space Fabric. Imagine somehow being able to build a spacecraft which can resist any kind of gravity and other critical conditions, then fly inside black hole just beyond event horizon for a split second and fly back, after exit our galaxy likely doesn't exist anymore even from your PoV it was just there few seconds ago and no one knows how many billions of years you've been there from an Earth's time perspective. Or one would simply die together with the universe and the black hole the same second they go beyond the event horizon who knows." - ExacoCGI

"That there is enough space between the Earth and our Moon to fit in all the other planets." - decitertiember

"The sheer size of it always blows my mind. Just the observable universe is 93 billion light-years in diameter, and it’s estimated that the actual universe is about 250x times that." - CymroCam

"The fact that space isn't just the backdrop in which everything occurs. It actually bends in response to gravity. When you see the James Webb pics for example with the gravitational lensing, the light is going "straight" in that's it's doing what light does and taking the shortest path from A to B. However, space is being bent which is why the shortest path is curved. It's wild that it's warping around us." - RPC3

"that everything in the universe is actually moving through spacetime at the exact same velocity: C, you, me, a rock, and a photon, are all traveling at the same speed." - EvidenceOfReason

"Space," the Hitchhiker's Guide says, "is big. Really big. You just won't believe how vastly hugely mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space. Listen . . ." and so on." - ShiningRayde

"The fact that 'normal' matter only equates to around 5% of the universe as we know it...The rest of it - Dark energy and matter is largely unknown." - huskyhoonigan

"Pretty much everything you look at isn’t even there anymore" - Special-Conference41

"The boötes void. It has a radius of 165 million light years wide, and contains only 60 galaxies in a space that would be expected to have around 2000" - Butter_Garlic_Naan

"That we sent a robot 35 MILLION miles away. That robot took a selfie and sent it back." - JoaneHan

"The largest black hole is the size of Jupiter......'s orbit around the sun" - groovy604

"That we really went to the fucking moon. Imagine telling that to someone from 500 years ago." - ipakookapi

"I wouldn't say fact as it's impossible to know for sure but it's believed that the universe is expanding outwards in three dimensions faster than the speed of light. Further more, if you some how could travel to the edge, what would happen if you continued past it? What's outside of the expanding universe?" - Singulant

"And then you realise 10 billion suns could fit in the largest star" - chug-mug

"Light cannot bend, however objects that have mass can bend the space around them and if light passes through this space then it appears to bend. Buttttt because light travels at a constant speed and if it travels through this bended space it means that light is taking longer to reach its destination, this is impossible as light cannot slow down and is technically not bending, therefore in this bended space time SLOWS down. Blows my mind everytime I think about it." - mister1bollock

"That we will never be able to explore all of it." - roguediamond

"I read somewhere that there is no definite center of the universe because it is expanding infinitely in all directions. Thus any point in the universe is a center - making you the center of the universe." - Common-Transition973

"A photon released during a super nova in some far off galaxy could have spent billions of years and traveled across the entire universe just to end up hitting someone's butt while they were laying on a beach." - HumpieDouglas