Fire in ZERO-G!!

I'm about to experience weightlessness for the first time. Oh my god! Oh my god that is so strange. Oh my god this is totally freaky; this is way better than I expected. I'm just gonna say that right now. Um I'm going up to the ceiling, and here we are. I am ridiculously excited because behind me is a Zero-G plane. I'm in France, I was invited here by the YouTuber Bruce. This is Bruce, Diana Physics Girl. We are going - flying some parabolas - we're going into Zero-G. It's gonna be awesome! C'mon!

The principle behind weightlessness is pretty simple. The plane and everything inside it just need to accelerate towards the earth at the same rate as a freely falling object in a vacuum. That is 9.8 meters per second squared. So, you can think of your body as this pen and the plane as this bottle, and when it's freely falling, there's no contact force between the pen and the bottle, and so the pen feels weightless.

So you might think the way to do this is just to put the plane into a dive. But that's not actually how it works. Instead, the plane starts climbing at a steadily increasing angle. With no windows inside, it's impossible to tell that this is happening, and all you feel is pressed into the floor with a force 1.8 times your body weight. This is because the plane's acceleration is directed upwards and perpendicular to the floor, and it makes standing very difficult. Not only are you nearly twice as heavy, all the blood drains from your head and into your feet - which made me pretty dizzy.

• Ah! Haha! So weak... ugh - Lying on your back is much more comfortable, and we're advised not to move our heads around and look straight ahead because in hyper-G, our vestibular system is hypersensitive to movement, which can lead to motion sickness. And that's why this is sometimes called the vomit comet.

• I kind of like this.

• It is fun, feels like someone lying on you.

• Yeah - Not like that.

Once the plane is climbing at about 50 degrees, the engines are ramped down, and the plane is put into a parabolic trajectory. It's at this point that you start experiencing weightlessness.

• I can feel myself getting lighter... oh that is such a strange feeling... that is so weird...

The plane and you are still moving upward, but you are accelerating downward.

• There's Diana, she's the physics girl.

Then the plane peaks and starts speeding up again towards the Earth. The whole time the plane is accelerating toward Earth with the same acceleration as a free-falling object in a vacuum, the pilots have to very skillfully adjust the thrust to perfectly balance air resistance and maintain exactly this acceleration.

Oh, my goodness - how do you feel?

This is incredible. So, it's like throwing this bottle into the air; the pen inside experiences weightlessness from the time it leaves my hand until it comes into contact again. After 22 seconds of weightlessness, the pilots pull out of the dive again, subjecting us to hyper-G... as the plane accelerates upwards.

In total, we have performed thirteen of these zero-G parabolas - plus one Martian gravity and two Moon gravity parabolas.

Okay, we are now in Mars gravity. In Mars gravity I can do one arm pull-ups... maybe. I am the Martian.

We brought along some experiments to do in zero-G. So, this is in about 1g of gravity; this is what the flame looks like on this barbecue lighter. Now we are gonna try it in hyper-G? And then we'll try it in zero-G and it should be... We will see... (2x).

We take it for granted that flames had this distinctive shape. But that's only because of gravity. The products of combustion have more energy and so, move around faster and take up more space than the cooler air around them. Therefore, there is a buoyant force on them, which is greater than their weight - and so, hot air rises. This helps pull the oxygen from around the flame to continue the reaction.

We are going through hyper-G. I keep blowing out the candle because... the, uhhh... stress of hyper-G is significant. In hyper-G, this effect is magnified since the effect of gravity is almost twice as much. This amplifies the difference between the weight of the hot air and the weight of the cooler air around it - and so, the hot air rises faster... making a longer flame.

Oh my goodness. Look at that flame just... in zero-G 'cause there is... much less buoyant force to carry away... And so, the combustion is not as good; you can see a lot of smoke coming off of that candle. And it's incredible. So, we still have a gas flow, so this is why the flame is not circular. It is not a sphere, but it looks very strange.

In zero-G, the hot air is still less dense than the cooler air... but now there is no weight and no buoyant force. So, the flame doesn't rise as high. This flame still maintains some of its shape because of the flow of fuel from the lighter; otherwise, the flame would form a sphere. Like on the space station. Where it's very difficult to maintain the combustion reaction because it's hard for oxygen to access the fuel with all of the combustion products getting in the way.

So, if you're ever unsure about what the gravitational acceleration is where you are, well, looking at a flame is a pretty good way of finding out.

I also brought along a slinky to try the slow-motion slinky drop but, in zero-G. Of course, here I couldn't dangle the slinky under its own weight, so I swung it around my head instead. The effect should be similar with each coil stretching to provide the tension that keeps... the length of the slinky beyond that... accelerating in uniform circular motion. I wanted to see what happens to the end of the slinky when I let go.

Here we go, 3, 2, 1. Did you catch that? The slinky remained fairly stretched out and kept rotating at about the same frequency as before. Initially, I thought this was a boring result. But then I realized... the reason the slinky doesn't contract is because weight was never part of this equation.

The slinky stretched out in the first place because it was rotating. And since it's rotating after I let go... roughly, the same amount of tension is required to maintain that circular motion. And so, it doesn't contract. In zero-G, it's possible to have a stretched slinky rotating in place without contracting as long as the tension in the slinky provides the centripetal force; it will keep spinning.

This just goes against my intuition, which is made, of course... only out of experiences with gravity. Being weightless was an unforgettable experience. But maybe my favorite part was how it challenged my intuition. And that's the reason we need to do research in zero-G.

I want to say a huge thanks to the team at NovaSpace who made this an unforgettable experience. And, of course, Bruce who runs a French YouTube channel, e-penser for inviting me. You should really go check out his video from the zero-G experience, and of course, Diana, the Physics Girl. Go check out her video on zero-G here.