Why can fireworks 'draw' hearts, flags, bamboo groves, and other shapes in the sky?

Modern fireworks don't just explode into familiar rings of light; they can create shapes like stars, hearts, the Earth, flags, and even complex forms like boats or bamboo groves.

Fireworks celebrating the successful conclusion of the 14th National Congress of the Party, evening of January 23 - Photo: NAM TRAN

Behind the "light displays" of fireworks are the results of precise calculations in physics, chemistry, and fireworks design engineering.

The image was 'programmed' from inside the firework.

According to HowStuffWorks , a firework launched into the air consists of four main components: a propellant to launch the firework upwards, a delay fuse to time the explosion, a central explosive, and hundreds to thousands of fuel particles—small units containing a mixture of chemicals that create color, sparks, and burning time.

The key point is that these combustion particles are not placed randomly, but are pre-arranged into the desired shape right from the manufacturing stage.

Live Science explains that if the burning particles are arranged in the shape of a star, heart, or smiley face inside the firework, then when the central explosive is detonated, the entire structure will burst open and "draw" that exact shape in the sky.

Essentially, fireworks don't create their own shapes at the moment of explosion. According to an article on the American Physical Society (AIP) website, the image viewers see is simply an enlarged version of a very small geometric structure that already exists inside the firework.

When the central explosive takes effect, the burning particles are ejected almost simultaneously, forming an expanding "particle cloud" in space. In that brief moment, the initial composition is maintained long enough for the human eye to perceive the image.

To achieve this, fireworks manufacturers must carefully consider many factors. According to AIP, the number of burning particles determines the "resolution" of the image, the size of each particle affects sharpness, and the energy of the central explosive determines the degree of expansion of the image.

For example, if the explosive is too weak, the image will be blown out unevenly, while if it's too strong, it can "tear" or distort the image before it has a chance to become clearly visible.

Another crucial factor is the burn time of the particle. According to HowStuffWorks , each particle is designed to burn brightly for a very precise amount of time, long enough for the image to become clear before fading away, rather than extinguishing too quickly or prolonging the burn time and causing blurring.

Spectacular fireworks displays depend on many technological factors - Photo: TECHNIQUEST

Physical limitations and the reason for using ground-based fireworks.

Despite increasingly sophisticated shaping techniques, fireworks are still subject to clear physical limitations.

According to Live Science , the rocket can rotate or tilt as it ascends, causing the image to flip, distort, or change its viewing angle. Just a high-altitude breeze or a slight deviation in its flight path can cause the drawing to no longer be "correct" as originally designed.

Therefore, complex, detailed shapes or those requiring clear "correct orientation," such as letters, logos, boats, or bamboo trees, are rarely created using aerial fireworks. Instead, large-scale displays typically utilize ground-based sculpted fireworks.

Fireworks were shaped into a beautiful bamboo grove during the artistic fireworks display celebrating the successful conclusion of the 14th Party Congress on the evening of January 23rd - Photo: NAM TRAN

With this technique, hundreds or thousands of small firework tubes are fixed onto a metal frame according to a specific design. When ignited simultaneously or in sequence, these fixed points of fire create a sharp, stable image that is less dependent on wind or viewing angle.

According to HowStuffWorks , this is a common method in festivals that need to convey a clear symbol or message to the audience.

AIP concludes that fireworks is now a tightly controlled field of applied physics and chemistry. Each fireworks display is the result of calculations involving geometry, dynamics, combustion reactions, and even meteorological conditions.

Thanks to this, the dazzling images that appear in the sky evoke a festive feeling, while also demonstrating humanity's ability to use science to "paint with light," transforming the tiny structures inside the fireworks into impressive visual moments in mid-air.

High-altitude fireworks display in Hanoi on the evening of January 23rd to celebrate the successful conclusion of the 14th National Congress - Photo: NAM TRAN

HOANG THI

Source: https://tuoitre.vn/vi-sao-phao-hoa-co-the-ve-trai-tim-la-co-bui-tre-tren-bau-troi-20260125143927712.htm