From: veritasium
The experience of weightlessness can be “totally freaky” and “way better than expected” [00:00:14]. This profound sensation was achieved aboard a Zero-G plane in France, as part of an invitation from YouTuber Bruce, also featuring Diana, the Physics Girl [00:00:34].
The Physics Behind Creating Zero Gravity Environments
The principle of weightlessness is straightforward: a plane and everything within it must accelerate towards Earth at the same rate as a freely falling object in a vacuum, which is 9.8 meters per second squared [00:00:48]. This means there’s no contact force between an object and its container, making the object feel weightless [00:01:03].
The Parabolic Maneuver
Contrary to simply diving, the process involves a specific parabolic trajectory:
- Climb Phase (Hyper-G): The plane begins climbing at a steadily increasing angle [00:01:16]. During this phase, passengers are pressed into the floor with a force 1.8 times their body weight [00:01:24]. This “hyper-G” effect, caused by the plane’s upward acceleration perpendicular to the floor, makes standing difficult and can cause blood to drain to the feet, leading to dizziness [00:01:30]. To combat motion sickness, also known as the “vomit comet,” it’s advised to lie on one’s back and avoid head movements, as the vestibular system becomes hypersensitive in hyper-G [00:01:51].
- Parabolic Trajectory (Weightlessness): Once the plane is climbing at approximately 50 degrees, the engines are throttled down, and the plane enters a parabolic trajectory [00:02:10]. It’s at this point that weightlessness begins [00:02:17]. The plane and its contents are still moving upward, but accelerating downward [00:02:27]. Throughout this phase, which lasts about 22 seconds [00:03:05], pilots skillfully adjust thrust to counteract air resistance and maintain the precise acceleration of a free-falling object in a vacuum [00:02:46].
- Pull-Out Phase (Hyper-G return): After 22 seconds of weightlessness, pilots pull out of the dive, once again subjecting occupants to hyper-G as the plane accelerates upwards [00:03:09].
In total, thirteen zero-G parabolas were performed, alongside one Martian gravity and two Moon gravity parabolas [00:03:13].
Conducting Experiments in Zero Gravity
Several experiments were conducted to observe phenomena under different gravitational conditions.
Effects of Zero Gravity on Fire and Flames
Flames typically have a distinctive shape due to gravity [00:03:51]. The hot products of combustion are less dense and experience a buoyant force greater than their weight, causing hot air to rise and draw in oxygen to sustain the reaction [00:04:04].
- In 1g: A barbecue lighter flame appears as expected [00:03:39].
- In Hyper-G: The effect of gravity is almost doubled [00:04:25]. This magnifies the difference in weight between hot and cool air, causing the hot air to rise faster and resulting in a longer flame [00:04:27].
- In Zero-G: With much less buoyant force [00:04:47], and no weight or buoyant force, the flame does not rise [00:05:13]. Combustion is less efficient, producing a lot of smoke [00:04:50]. While the flame from the lighter maintained some shape due to fuel flow, otherwise it would form a sphere, as seen on the International Space Station [00:05:20]. Maintaining combustion in space is challenging because combustion products can prevent oxygen from reaching the fuel [00:05:28]. Observing a flame can be a good way to determine the gravitational acceleration of an environment [00:05:36].
Rotating Bodies in Microgravity: The Slinky Experiment
A slinky was brought along to observe its behavior in zero-G, specifically a slow-motion slinky drop concept without gravity [00:05:49]. Since it couldn’t dangle under its own weight, it was swung around a head to stretch it [00:05:54]. The idea was for each coil to stretch to provide the tension needed for the uniform circular motion of the slinky beyond that point [00:06:01].
Upon release, the slinky remained fairly stretched out and continued rotating at roughly the same frequency [00:06:26]. The reason it didn’t contract is that its stretch was initially due to rotation, not weight [00:06:35]. As it continued rotating, the same amount of tension was required to maintain that circular motion, preventing it from contracting [00:06:44]. In zero-G, a stretched slinky can rotate in place without contracting as long as the tension provides the centripetal force [00:06:53].
Challenging Intuition
The experience of weightlessness, particularly the slinky experiment, challenged deeply ingrained intuition, which is primarily formed from experiences within Earth’s gravity [00:07:04]. This highlights the critical need for research in zero-G to better understand physics outside of terrestrial assumptions [00:07:20].
The experience was made possible by the team at NovaSpace and by Bruce of e-penser for the invitation [00:07:28].