The Enduring Law of Conservation of Mass: From the Big Bang to You

Everything in the universe, from the tiniest atom to the most massive star, possesses mass. What's truly remarkable is that the total amount of mass has remained constant throughout the universe's existence. This principle, known as the law of conservation of mass, governs everything from the birth and death of stars to the formation of planets and even ourselves. But how can the universe expand and evolve while maintaining a constant mass?

Understanding the Law of Conservation of Mass

The law of conservation of mass states that within an isolated system, mass (or matter and energy) cannot be created or destroyed. An isolated system is defined as one where neither matter nor energy can cross its boundaries. While perfect isolated systems are hard to find in our daily lives, the universe itself is considered the ultimate isolated system.

A Simple Illustration

Imagine a closed container with six carbon atoms, twelve hydrogen atoms, and eighteen oxygen atoms. By adding a bit of energy, these atoms can combine to form familiar molecules like water (H2O) and carbon dioxide (CO2). The key is that we can't simply create or destroy these atoms. We're limited to what we initially have.

These atoms can rearrange themselves. For example, they might form more carbon dioxide and water. Add more energy, and they could even form a simple sugar (like glucose) and oxygen gas. Throughout these transformations, the number of each type of atom remains constant: six carbon, twelve hydrogen, and eighteen oxygen.

The energy applied is stored in the bonds between the atoms. This energy can be released by breaking the sugar back down into water and carbon dioxide, again without changing the number of atoms.

Explosive Examples: Methane and Propane

Consider methane (CH4), a gas often associated with natural gas and even cow flatulence. When methane reacts with oxygen (combustion), it produces carbon dioxide, water, and energy. Notice that the four hydrogen atoms in methane end up in two water molecules. No atoms are created or destroyed, only rearranged.

The same principle applies to propane (C3H8), another combustible gas. When ignited in the presence of oxygen, it yields carbon dioxide and water. The three carbon atoms in propane become three carbon dioxide molecules, demonstrating that the atoms simply shift from one molecule to another.

These examples highlight that in any chemical reaction, the matter and energy that go in are always present and accounted for when the reaction is complete. This is the essence of the law of conservation of mass.

The Origin of Atoms: A Journey Back in Time

If mass cannot be created or destroyed, where did all the atoms come from in the first place? To answer this, we need to rewind to the very beginning: the Big Bang.

From the Big Bang to Stars

In the first three minutes after the Big Bang, hydrogen atoms formed from a high-energy soup of particles. Over time, these atoms clustered together to form stars. Within these stars, nuclear reactions fused lighter elements, like hydrogen and helium, into heavier elements, such as carbon and oxygen.

These nuclear reactions release tremendous amounts of energy, which might seem to violate the law of conservation of mass. However, Albert Einstein's famous equation, E=mc², reveals that energy and mass are equivalent. The total mass of the starting atoms is slightly greater than the mass of the products, and this tiny loss of mass is converted into the vast amount of energy released as light and heat.

Supernovas and the Creation of Earth

Eventually, massive stars explode in supernovas, scattering the elements they created across the universe. These elements, along with atoms from other supernovas, eventually coalesced to form planets like Earth.

We Are All Star Stuff

The atoms that make up everything around us, including ourselves, were forged in the hearts of stars billions of years ago. These atoms have been recycled through countless reactions and transformations, always conserved, never created or destroyed. As Carl Sagan famously said, "We are all made of star stuff," a testament to the enduring law of conservation of mass and our deep connection to the cosmos.