"We are stardust" means that a. Earth exists because of the collision of two stars. b. the atoms in our bodies have passed through (and in many cases formed in stars. c. Earth is primarily formed of material that used to be in the Sun. d. Earth and the other planets will eventually form a star.

The phrase 'We are stardust' speaks volumes about the origin of elements that make up everything around us, including our own bodies. Atoms are the tiny building blocks of matter. When the universe first began, it consisted mostly of hydrogen and helium—the simplest elements. Over billions of years, through processes occurring within stars and supernovae, heavier elements were formed. These stars act like cosmic forges, combining smaller atoms to create bigger ones through various nuclear reactions.
Let's simplify it:

• Big Bang: Made hydrogen and helium primarily.
• Stars: Make heavier elements up to iron through nuclear fusion.
• Supernovae: Explosions create even heavier elements and spread them throughout the universe.

Hence, the elements found on Earth and in our bodies, like carbon, nitrogen, and oxygen, originated in stars. This forms the base of the 'We are stardust' concept.

How do stars create these elements? This happens through a process called stellar nucleosynthesis. Stars are incredibly hot, reaching millions of degrees. In such extreme conditions, nuclear reactions occur, where lighter atomic nuclei fuse to form heavier ones. For instance:

• Hydrogen fusion: Four hydrogen nuclei combine to form one helium nucleus.
• Heavier elements: As the star burns through its hydrogen, it begins fusing helium into carbon, oxygen, and so on, up to iron.

Once a star reaches the end of its life, especially if it is massive, it can explode in a supernova. This explosion scatters the elements it has created into space. These materials can then become part of new stars, planets, and eventually, living organisms. Every atom in your body likely originated from such processes inside a star!

It's fascinating to know that the human body is made up of elements that were once in stars. The main elements that comprise the human body include:

• Oxygen (65%): Essential for respiration and cellular functions.
• Carbon (18%): The backbone of all organic molecules.
• Hydrogen (10%): Found in water and most organic compounds.
• Nitrogen (3%): Key element in proteins, DNA, and other organic substances.

Apart from these, the body contains calcium, phosphorus, potassium, sulfur, sodium, and magnesium, all contributing to various physiological functions.
Each of these elements was manufactured in the heart of an ancient star, then scattered across the galaxy by stellar winds or when the star exploded. Eventually, these elements came together to form our planet and all the life it supports. So next time you hear 'We are stardust,' remember—it's not just poetry; it's science!