Did You Know the Sun Is Getting Lighter Every Second?
4 Minutes
How the Sun loses mass for students, explaining Einstein's equation E = mc², mass-energy equivalence, and nuclear fusion. A Tamil science lesson.
- Thought experiment on pushing an object near the speed of light
- How mass and energy convert into each other using E = mc²
- Proton fusion in the Sun's core releasing energy and losing mass
What this lesson teaches
The Sun loses mass every second because nuclear fusion inside its core continuously converts matter into energy according to Albert Einstein's equation, E = mc². This mass-energy equivalence means that as the Sun generates its tremendous light and heat, it sheds about 4.3 million tonnes of mass every second.
The link between mass and energy
Albert Einstein showed that mass and energy are interchangeable forms of the same thing. In a thought experiment, pushing an object near the speed of light causes extra energy to turn into mass rather than extra speed, which prevents any object with mass from ever reaching or exceeding light speed. For instance, heating a one-kilogram gold bar increases its mass by a tiny amount, and cooling it down reduces that mass as heat radiates away.
The power of Einstein's equation
The equation E = mc² explains that energy equals mass multiplied by the speed of light squared. Because the speed of light is nearly 300 million metres per second, squaring it creates a gigantic multiplication factor. This means that converting even a tiny fraction of mass yields an enormous amount of energy. For example, the atomic bomb dropped on Hiroshima converted only about 0.6 grams of uranium into energy, yet that small amount caused devastating destruction.
Proton fusion in the Sun's core
The Sun is made largely of hydrogen, and its core experiences extreme pressure alongside temperatures reaching 15 million degrees Celsius. Under these fierce conditions, hydrogen atoms break apart into free electrons and protons. Even though protons carry positive charges and naturally repel each other, the extreme pressure and speed make collisions unavoidable. When these protons slam together, they join in a process called nuclear fusion.
Why the Sun gets lighter
During nuclear fusion, the combining protons lose roughly 0.7 percent of their mass. This lost mass is not destroyed; instead, it transforms directly into heat and light energy that travels outward to Earth. Because countless protons fuse continuously, the Sun loses 4.3 billion kilograms, or 4.3 million tonnes, of mass every second. That lost mass converts into an unfathomable quantity of energy, equal to 4.3 million tonnes multiplied by the speed of light squared.