Why does a candle flame always point upwards?

Who has never found themselves admiring the flame of a candle and wondering why it always points upwards? If you are like me and have asked yourself this question, in this post we will discover together the fascinating science behind this curiosity so common in our daily lives.

When a candle burns, the flame heats the air nearby and begins to rise. As this hot air moves upward, cooler air and oxygen rush into the base of the flame to replace it. As this cooler air is heated, it also rises and is replaced by cooler air at the base of the flame. This creates a continuous cycle of upward-moving air around the flame, which gives the flame its elongated or teardrop shape.

Since "up" and "down" are functions of Earth's gravity, scientists wondered what a candle flame would look like in outer space, where the force of gravity is minimal and there really is no "up" or "down."

In the late 1990s, NASA scientists conducted several experiments on spacecraft to see how candle flames behaved in microgravity.

As you can see in the NASA photo above right, a candle flame in microgravity is spherical rather than elongated like it is on Earth. Without gravity, there is no "upward" direction for hot air to rise and create a convection current.

One of the most interesting things about candles is that, in addition to their practical function of lighting a room, they also provide a unique visual spectacle. Understanding the science behind the shape of a candle flame, and how that shape is affected by gravity, can further increase our fascination with this object that is so common in our lives.

These NASA studies remind us of the importance of scientific research and exploration of the unknown, and inspire us to continue discovering and learning about the world around us.