If the balloon malfunctions, they can feel weightlessness until they reach terminal velocity. The problem is they're also going to experience a pretty large acceleration when reaching the surface.

> If the balloon malfunctions, they can feel weightlessness until they reach terminal velocity

Until they start decelerating, which is immediately. They’ll also feel it fairly rapidly, I think.

https://en.wikipedia.org/wiki/Reduced-gravity_aircraft#Opera... (emphasis added):

“The sensation of weightlessness is achieved by reducing thrust and lowering the nose to maintain a neutral, or "zero lift", configuration such that the aircraft follows a ballistic trajectory, with engine thrust exactly compensating for drag”

True. Air resistance is always there, although negligible in the first few seconds.

Weightlessness is very different than just equally balanced forces of drag and acceleration.

If you crush something in a hydraulic press, it might have balanced forces and zero acceleration.

For that matter, Im not accelerating when I lay on the surface of the earth, but I hardly feel weightless.

What do you feel if you're very far from any nearby planet sized object, then?

Falling and weightlessness are identical.

Weightlessness only feels weird because we rarely feel it.

If you were suddenly in empty space (e.g. in an area with zero intrinsic acceleration), you would feel like you are falling.

Because the feeling of falling is actually the feeling of NOT having the constant gravity (i.e. acceleration) you're used to.

If you were born in weightlessness, gravity would be the strange feeling (cue Bane saying, "you only adopted weightlessness, I was born in it").

Falling. Falling towards a planet, star, or galactic core is all pretty much the same. Tidal forces will be a bit different, but those aren't on a feelable scale with most objects.

OK, but as a poor earthling who's never experienced low gravity... surely the force of gravity affects the feeling of "falling" even if you're not in an orbit around some nearby planet sized thing? Does that feel substantially different than, say, falling down an elevator shaft on earth?

"the feeling of falling" -- That's called weightlessness, free-fall, and zero-gee. Being in interplanetary space, being in earth orbit, being in the parabolic Vomit Comet, being in a drop tower capsule, being in an elevator compartment falling down a shaft, stepping off a diving board, there's no difference in the 'feeling'.

https://en.wikipedia.org/wiki/Drop_tube -- https://en.wikipedia.org/wiki/Reduced-gravity_aircraft -- https://en.wikipedia.org/wiki/Free_fall

In a hypothetical universe that contains only you + space, what would you feel?

Same thing: falling.

The opposite of falling is accelerating, and you feel acceleration. A rocket rocketing in an empty universe would feel the same as a rocket rocketing in orbit would feel the same as a rocket just sitting around on Earth. Wait, that last one's different...

We happen to live most of lives in a somewhat exceptional case of constant acceleration (with respect to falling). The ground below our feet has gotten us pretty used to acceleration. But, if you jump, you'll feel like falling too!

If you spent your entire life in an area with gravity prior to that moment, you would feel like you are falling even though you are NOT.

Our brain is used to gravity. That is why weightlessness feels weird.

But falling and weightlessness are indistinguishable to your brain. They are exactly the same thing.

So, if all the gravity around you suddenly disappeared, your brain would initially tell you that you are falling.

Only after some time would you convince yourself that, "No, I'm not falling... Gravity just disappeared. I'm just weightless."

If there is no gravitational field, you don't need a fall to cancel it out.

lonely?

:(

more accurately, you dont feel falling because the magnitude is so low.

Hmm, makes me wonder what percentage weight you would feel at, say, the height of the ISS if you were fixed in a relative location to the Earth (not orbiting at all).

Considering the same question for geostationary orbits had me confused for a moment and then I realised we are not in a fixed location relative to the Earth, thanks to the Earth's spin. I wonder what extra percentage weight we would feel if it weren't spinning.

F = g(m2*m2)/d^2. Earth surface gravity using Earth's radius as d; iss using that radius plus orbital height of 408km. Earth's surface gravity = 9.81m/s2, ISS gravity = 8.66m/s2.

So the answer is, if you could hold the ISS stationary without falling, people in it would feel almost as much gravity. You would have to go much higher than the ISS to feel weightless without orbiting/falling.

Assuming people feel weightless at 1m/s2 or less, you can solve for that! And the answer is 13,600 km.

Thanks to all the replies about the (very small) extra weight at the height of the ISS.

As for the centrifugal force from the Earth's rotation, Wikipedia puts it at about 0.3% (which, added to the effect of the Earth's bulge, means you feel a total of 0.5% less weight at the equator than at the poles).

https://en.m.wikipedia.org/wiki/Gravity_of_Earth#Latitude

You can use Newton's equations for gravity to calculate this.

https://www.quora.com/What-is-the-acceleration-due-to-gravit...

At the ISS, the extra distance from the center of the earth is minimal compared to the radius of the earth itself. Therefore, there wouldn't be a great difference.

Gravity is proportional to 1/r^2 (r being distance), so you could take a stab at computing your ISS question with that info.

The centripetal force question is a little more challenging, but still in the realm of algebra. The complicated part is setting up the problem and understanding where the forces are coming from and if/how they cancel each other.

Since the inverse square law applies and you're only 100 miles away from a planet 25,000 miles in circumference, I think it would be in the high 90's percentage of your weight on earth.

You have to get pretty far away to experience true "weightlessness".

Still, 19 miles vs 250 miles (and static not 17,500 mph) for the ISS - maybe the balloon passengers feel 0.98g?

They still might, depending on how rigorous QA is going to be...

I honestly had no idea this was the case! I assumed it was just space that "had no gravity" what you're saying makes sense though. Mind blown!

I've been part of a space industry non-profit that partners with the Government of Canada to put experiments run by students on planes that do "parabolic flights" to simulate "weightlessness" while falling. Around when I first started, I proposed writing the term "zero gravity" on a webpage we were updating. But as my supervisor adamantly noted at the time, that would have been inaccurate.

The convention was to never use the term "zero gravity," since using that term would perpetuate a common misunderstanding. Instead, we've used the term "microgravity" in its place—which makes sense, as there are still small gravitational forces acting on every object in space.

NASA also published a webpage with a good explanation of what microgravity is, with a nice diagram of how it works (including a visual of the parabolic flight): https://www.nasa.gov/learning-resources/for-kids-and-student...

Space has almost no gravity but you need to be quite far away from other big objects.

Gravity is the attraction of two objects. Space (which is nothingness) has no gravity. Where you are located in space might have gravitational pull relative to an object.

if you have a long enough rope, you could keep the balloon up there and freefall for a while and then brake close to the ground.

Air resistance means you only feel weightless for a few seconds on a long fall.

Indoor skydiving lets you ‘fall’ for hours, but you don’t accelerate so you don’t feel weightless.

fair point, but 100k up hopefully it's a lot smaller. maybe you could pull harder on the rope from the ground as well to balance it somewhat. but yes, you won't be weightless the whole way.

I did not realize this, but makes completely sense. Still super disappointing!