Nothing quite prepares you for becoming weightless, except perhaps being born.
Aboard a specially converted Airbus airliner to experience a parabolic flight organised by France's space agency CNES, I am first pressed and squeezed by a force far greater than me.
Then, dangled upside down as if by an invisible hand, I feel almost unbearably light as I try to find my bearings in a completely new element. Fifteen roller-coaster manoeuvres later, I feel like kicking away the prop of gravity for good.
My companions in this journey of kinetic discovery are European politicians and space agency directors. As part of efforts by CNES to persuade more countries to use its zero G conditions for scientific research, VIPs fill the air.
The night before we got airborne, I found these European space experts in a hotel lobby debating G forces and physics.
They explained that zero G does not mean an absence of gravity, but freefall. Even orbiting astronauts are subject to gravity: They just feel weightless as they tumble in space.
Consider the sensation of lightness you get in an elevator as it starts to go down - and heaviness as it rises - the experts said. If the ropes were to snap, you would be in freefall inside an object which is also in freefall, and so feel weightless.
Like the elevator, a spaceship in orbit keeps falling - but over the horizon - following the earth's curvature.
Our plane ride would give us that experience by briefly tracing a similar curved path, like water droplets flicked up from a hose.
"Think about throwing a rock or a ball. If there is no resistance it goes into a parabola," said fellow passenger Bo Andersen, director-general of the Norwegian Space Centre.
French astronaut Jean-François Clervoy, who runs Novespace, the CNES subsidiary operating the plane, explained how the aircraft would create weightless conditions by ploughing through a series of parabolic arcsacross the sky.
The plane looks from the outside like a normal jetliner. But after climbing steeply, our A300 would become an aluminium tube in semi-controlled freefall until the pilots brought it gradually back to level flight.
Someone asked what would happen if there were an emergency during the 22 seconds we would be in zero G. If something goes wrong, can the crew pull out immediately?
"No way," said chief pilot Stephane Pichene.
"During the parabola we will be flying 20-30 knots below the stall speed of the aircraft. Once you are committed you have to finish."
The pilots explained they would ignore most cockpit alarms in this part of the flight. It was, they said, a reliable plane and maintained even more rigorously than usual.
It simply wasn't designed to do the things we would be experiencing.
"We know which alarms are normal," Mr Pichene said.
On flight day we were told to eat a light breakfast and report for anti-sickness jabs. The more experienced hands advised us to chew gum too.
One last piece of advice before takeoff: "If you use a paper sick bag, please remember to close it afterwards."
In zero-G everything floats.
Inside the plane, about 20 scientists were setting up experiments that might, among other things, help astronauts grow life-sustaining plants on future trips to Mars.
A padded area surrounded by nets was where we and the VIPs would bob about.
After a normal take-off we headed out to a tall canyon of airspace over the sea to avoid turbulence over land.
Over the loudspeaker, Mr Pichene counted down to the first manoeuvre.
As he yelled "pull up" and put on maximum thrust, we started to feel 2G or twice our normal weight. Seated on the padded floor, I felt my body being pressed into the base of my spine.
I thought back to the briefing: It is imperative not to move your head or eyes to avoid confusing the brain and feeling sick.
Mr Pichene counted off the angle of the climb. Twenty degrees, 40 degrees.
We were climbing more than twice as steeply as an airliner at take-off.
At 47 degrees, he shouted "injection" and slung us into the perfect trajectory needed to defy gravity.
Gravity lets go without warning. It feels like plunging into a pool without the resistance of water, only upwards.
Gyrating, spinning - confounding the plodding habits of a lifetime.
I quickly learned thrashing arms and legs achieves nothing.
To move you must push off a surface and once you do, you can't stop until you hit something.
Safety crew anchored to the floor were on hand to prevent injuries and help passengers spin in a ball, arms over their knees, almost in a foetal position.
Bo Andersen was elated: "There is a feeling you can control your movements, but you can't," he said.
I narrowly avoided a mid-air collision with the posterior of a former government minister, and made a mental note that I was flying by the seat of a politician's pants.
On the pilot's command "pull out", we slammed from zero G back to 2G - from weighing nothing to twice our normal weight. Anyone pointing downwards would land on their head with a bump. Anything parked in mid-air like a camera risked getting broken.
The jet flattened out then started another bound upwards.
We performed 15 more of these kangaroo hops across the sky.
Being weightless improves with practice, although my personal ambition of eating M&Ms suspended in mid-air, as astronauts do on television, proved beyond my capabilities.
Surprisingly almost no one got sick. Euphoric, but tired by duelling gravity, we were weightless for a total of six minutes.