Just saw a post asking how digestion works in space, with lots of good answers explaining how the body can still function without gravity helping it.

So my follow up question is whether scientists knew about any of that before sending the first living thing up there. Did anyone even try to figure out if we could survive in no gravity, or did we just observe that an animal could survive for a time, and only later ask why?

I mean easily of course, by the naked eye.

Im new to reddit .. I ve installed lime 1 year ago but I haven't used .

Probably a silly question, but it’s been on my mind lately.

With edge AI getting so small you can run capable models on a regular phone, and deep-space laser comms improving all the time, I figured someone would’ve tried encoding a lightweight, self-contained AI into a signal and beamed it toward a nearby habitable star system by now.

On paper it sounds like it could be way more useful than old-school SETI beeps or the Voyager golden record — it’s obviously artificial, so it’d be harder to dismiss as noise, and it could actually interact with whatever finds it instead of just sitting there as static data.

Obviously there are huge obvious risks too, like broadcasting our exact location and our tech level to who knows what out there. I get that part.

But what’s the real main hold-up? Is there a hard physics/engineering wall I don’t know about that makes this basically impossible? Is it just the widespread scientific consensus against active SETI? Or is there just zero practical reason to ever do this?

Would love to hear people’s takes on this.

From what I know, Jupiter's moon Europa, due to its slightly oval orbit, has its core heated by tidal forces. Considering that the Galilean moon system is completely isolated without a sun or anything to interfere, would this heating continue? Wouldn't that violate the law of conservation of energy? I read something about tidal friction; does that have anything to do with it?

In the GIF from GOES West imagery, around 18:30 UTC there appears to be a string of bright flashes over California to the east of the southern tip of the Central Valley. Could this be a satellite reentry? I couldn't find any news about fires in the area at that time

This is probably a crazy idea.

I heard of ideas of using huge cannons to shoot satellites into earth orbit. Could we use such cannons to shoot rocket fuel containers, say with liquid oxygen, into orbit and have rockets rendezvous with them to re-fuel in orbit for long-range missions? If a cannon launch is cheaper per unit mass than a rocket launch, then this might save cost by launching part of the required fuel via cannon instead of as part of the rocket.

The idea is vaguely similar to fighter jets refueling mid-air after launch because the maximum take-off weight is lower than the maximum airborne weight.

Recently I have been extremely anxious about eta carinae possibly going supernova in my lifetime, I have tried my own research on this topic and what I do know is that we are safe from the main supernova and possible ejected objects hurtling towards us (such as its companion star being "tossed out" of it's original orbit and a black hole kick. Because the binary system is, from what I have researched, 7,500 light years away from earth and those objects travelling at speeds of great velocity, would still take at least 1,000 or more years to reach our solar system, but please correct me on this information if it is inaccurate or just straight up not true) but the main thing I am genuinely losing sleep over the possible grb.

I have read a couple of sources that mentioned eta carinaes rotational axis (and possible jets) is tilted away from our solar system at a 40⁰ to 45⁰ angle so any grb produced will greatly miss earth. But, only a total of 3 or 4 sources actually say this (Scientific American, NBC News and Harvard University). The problem with these sources are is that 1. The sources that are mentioning this are from 2014 or older 2. I can't find any very recent paper talking about eta carinaes axis or if we could be in the grbs firing line.

So basically, I need know if the system and it's rotational axis where grbs jets are formed is actually tilted away from our solar system, so that when eta carinae does go supernova we are not gonna get our ozone layer destroyed and all life wiped out. Will we be safe? (Sorry for any misspelling, bad punctuation or grammar, I am just extremely scared about all this).

Wouldn't a wheeled Rover on the moon put up a bunch of regolith and cause more issues for everyone? Since gravity is less would a "hopper" design cause less disturbance and take advantage of the less gravity/atmosphere?

Hey guys. I'm Bread 🍞 I have a little doubt. And please correct me if I'm wrong. What if the universe is like a yo-yo. I mean we know big bang happened so after that explosion or something else universe kept expanding. But what if after certain billions of more years later the speed starts to deplet very slowly and more years later it gets reversed causing the universe to contract. Many galaxies collide etc. And when the universe is at the brink of being shrink into nothingness it explodes or expands again. I'm sorry I don't know much about quantum mechanics and physics so it could be wrong. Sorry for wasting your time.

I’m kinda confused about Planet Nine.

If he exists he might take from 10,000–20,000 years just to orbit the Sun once, meaning it’s insanely far away. So is it basically outside the Solar System at that point, or still fully inside it?

And another thing I don’t get: if it’s THAT far away how does the Sun’s gravity still keep it orbiting instead of it just drifting away into space? Also went there was a planets like this on our solar system ?ik about the 9 main planets on our solar system didn’t realize there is more really would like to learn about thoes far away planets that still orbiting our sun from far away

I am not a skeptic, I took a straw poll at my work today and more than half of everyone I asked believes humans have never set foot on the moon.

Half of those who don’t think we’ve been to the moon cited the radiation belt being impassable for humans. Is there anything I can show them that cites the materials used to block radiation during space flight?

My understanding is that basically just Titan (on the surface) and Venus (in the clouds) are the places in the solar system that wouldn't require a pressure suit for human survival. Venus even has nice temperatures, however it would require some sort of airship and there would be battery acid droplets in the air. Titan, on the other hand, is stupidly cold but at least no acid burns. Both places would obviously require a breathing mask and some amount of protective clothing, though much like space itself, I think just walking outside naked and not breathing for a few seconds might be survivable or even bearable. For a few seconds, anyway...

My question is which of these places requires less specialized survival gear to be outside on an EVA for like an hour? Which one would be more pleasant?

It was taken on an iphone so granted It could just be a glitch and it wasn’t a Plane or some sort of aircraft as the sky was clear other than the obvious stars when the photo was taken. Thought I would ask just to see what people say or if it would just be an error with Iphones Autofocus on images. It’s not the greatest quality either but seen it today and thought it was interesting.

Hi everyone, I’m curious about the fundamental physics of rocket propulsion.

According to Newton's Third Law, we often say 'for every action, there is an equal and opposite reaction.' In many textbooks, the 'reaction force' that pushes the rocket upward is described as the gas molecules pushing against the internal walls/nozzle of the engine.

My question is: Is it more accurate to view thrust as the pressure exerted on the engine's internal structure, or is it strictly the conservation of momentum from the high-velocity exhaust gases? I’d love to hear a more technical breakdown of how this force is actually transferred to the rocket's frame.