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What is dark matter and what is antimatter? Are they the same or different? – Namrata, age 13, Ghaziabad, India
Imagine an epic video game with your favorite hero as a character. Another character is a mirror-image twin who shows up occasionally, exploding everything they touch. And, to add an extra level of difficulty, the game includes a mysterious hive of minions hiding at every corner, changing the rules of the game, but never showing themselves.
If you think of these characters as types of matter, this video game is basically how our universe works.
The hero is regular matter, which is everything we can see around us. Antimatter is the mirror-image explosive twin that scientists understand well but can barely find. And dark matter is the invisible minions. It is everywhere, but we cannot see it, and scientists have no idea what it is.
Despite having similar-sounding names, dark matter and antimatter are completely different. Interestingly, physicists like me know exactly what antimatter is, but there is almost none of it around. On the other hand, we have no idea what dark matter is, but there is a lot of it everywhere.
Antimatter: The mirror-image twin
All the regular matter around you is made of basic building blocks called atoms. Atoms have positively charged particles called protons surrounded by tiny negatively charged electrons.
Think of antimatter as regular matter’s oppositely charged twin.
All particles, like protons and the electrons, have antimatter siblings. Electrons have positrons, which are anti-electrons, while protons have antiprotons. Antiprotons and positrons make up antimatter atoms, or anti-atoms. They’re like mirror images, but with their electric charges flipped. When matter and antimatter meet, they destroy each other in a flash of light and energy and vanish.
Luckily, antimatter is very rare in our universe. But some special regular matter atoms, such as potassium, can decay to produce antimatter. For example, when you eat a banana, or any food rich in potassium, you are eating tiny amounts of these antimatter-producing atoms. The amount is too small to affect your health.
Antimatter was discovered almost 100 years ago. Today, scientists can create, store and study antimatter in the laboratory. They understand its properties very well. Doctors even use it for PET scans. They inject tiny amounts of antimatter-producing atoms into your body, and as these atoms travel through your body, the scan takes pictures of the flashes of light from the annihilation of the antimatter and regular matter in your body. This process lets doctors see what is happening inside your body.
Scientists have also figured out that when the universe was born, there were almost equal amounts of matter and antimatter. They…
