Why does a candle flame defy gravity and burn upward? What will happen on lighting a candle in space?

We all experienced lighting a candle once in a while. We light it up when the electricity is down, when used as a decoration, and sometimes we even use it for therapy. We could trace back the use of candles in the early 3000 BC, when the ancient Egyptians used it in shrines, temples, etc. And unlike the candles that we have today, the Egyptians made the old version of candles from beeswax.

Just by looking at it, we can already know its importance and say that it has several uses. Until today, the production of candles are still massive; several factories all around the world are contributing to the creation of these wax-based fuels.

As simple as it looks, there are a lot of interesting facts about candles, especially when you light it up. That is why even one of the great English scientists, Michael Faraday, authored a book made explicitly from observing a burning candle, which shows several scientific principles.

Furthermore, a burning candle shows a dull appearance, which makes it easily describable. We often compare the looks of a lit candle with a teardrop. Wherein the small flame on top of the candle has a teardrop shape.

However, this fact often comes along with the question – why does a candle flame defy gravity and burn upward? Because it seems pretty evident that the flame is going upward, causing it to have a teardrop shape. Also, if we have gravity, why does its flame go upwards instead of getting pulled down to the Earth? There are many phenomena in a single candle. And in this article, we are going to look into the scientific explanation as to why candles burn upwards.

Why does a candle flame burn upward?

Before we answer this question, let us first take a look into the fundamentals of flame. It is the combustion of oxygen and fuel, which produces heat energy. This combustion is what we see when we light a candle.

If you observe the flame on the candle, there are three colors present in it. We can see at the blue flame at the bottom part, the orange zone at the middle, and the yellow flame at the upper part of the flame. There is also a thin outer layer of blue flame covering the whole teardrop, which may not be entirely visible by simply looking at it.

All of these parts contribute to how the light in the candle works. Keep in mind that the upward motion in a lit candle is not only visible in candles since all fires here on Earth have the same upward flow. Surprisingly, gravity is the reason why the flame is going upwards.

When we light a candle, several chemical reactions are happening in the flame, which causes it to produce heat and light. Let us first take a look at the blue zone. The blue part of the candlelight is the hottest and the heaviest, that is why it is on the bottom, wherein it has complete combustion and with the most oxygen present. It is also where chemical reactions start to take place – the flame continuously takes in hydrocarbon molecules from the candle, which acts as the fuel.

Hydrocarbon is the primary oxidizer present in modern candles. Once its molecules are within the flame, it will start to break into individual atoms, which would give us one atom of hydrogen and carbon. Besides the hydrocarbon, the flame constantly sips in oxygen atom from the surrounding air – this is the main reason why oxygen is vital in creating fire. No oxygen means no fire. Once the oxygen atom is within the flame, chemical reactions will start to happen.

The hydrogen atom will keep on slamming against the oxygen atom, which would create water vapor. At the same time, some of the carbon atoms will also mix with the oxygen atom, which would then produce carbon dioxide. This reaction would cause warmer air to rise, which we can see in the yellow part of the flame. Compared to the blue zone, this part only has little oxygen, and it comes with the water vapor and carbon dioxide created from the bottom. They will continue to rise and form a convection current around the flame and emitting a full spectrum of visible light.

As for the blue zone, it will continuously take in oxygen from the surrounding air and repeat the process, creating a cycle.

What will happen if we lit a candle in space?

Now that we have this all figured out, let’s follow it up with this question – does lighting a candle in space give the same upward motion? We mentioned earlier that the reason why its flame burns upward is because of gravity. But what if we remove gravity, what would happen?

First and foremost, we cannot create fire in space since it would require air, which is absent in space. However, we can create our fire inside a space shuttle.

Let’s say we are in a space shuttle, and we lit our candle. Instead of having the same teardrop shape, its flame would have a spherical shape and is mostly covered in blue. We can see the spherical shape since, without gravity, it would be impossible to have the same teardrop form – mainly because there is no reason for the oxygen to rise. In space, an object’s weight doesn’t matter, and there is no light or heavy. The same thing goes with air. If air is caught within a flame, it will not be lighter even if heated. Thus, it wouldn’t rise like what we see here on Earth. Instead, it would remain spherical until the flame runs out.

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