From Hydrogen to Warmth
Stars like our sun do not burn fire or gas the way a campfire does. They run on nuclear fusion.
The sun is made mostly of hydrogen. Deep inside it, gravity squeezes hydrogen atoms so hard and heats them so much that they slam together and fuse.
Four hydrogen atoms get pushed together and turn into one helium atom.
When that happens, something strange but powerful occurs. The helium weighs a tiny bit less than the four hydrogens did. That missing mass does not disappear. It turns into energy.
This follows Einstein’s equation E equals M x C squared, (e-mc2), which means mass can turn into energy. Energy and mass are the same thing.
That is the engine that powers the sun and every star.
What Actually Comes Out Of The Sun?
Three main things are released during fusion.
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Photons
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Neutrinos
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Fast moving particles that carry kinetic energy
The one that warms your face is photons.
Photons are particles of light. They also carry energy. Heat is not a thing by itself. Heat is just energy moving from one place to another. Photons are how that energy travels.
What Reaches Earth?
The sun sends out many kinds of light, including gamma rays, x rays, ultraviolet, visible light, infrared, and radio waves.
Most of the dangerous radiation is blocked by the sun itself or by Earth’s atmosphere.
What reaches the ground is mostly visible light and infrared.
Those photons hit your skin, the ground, plants, water, and buildings. When photons hit atoms, they make those atoms vibrate. That vibration is what you feel as warmth.
So what is really happening is this.
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The sun turns hydrogen into helium.
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That releases energy as photons.
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Those photons travel about 93 million miles through space.
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They hit Earth and shake atoms.
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We feel that shaking as heat.
The Wild Part
The light hitting your face right now was created in the core of the sun. It took about 100,000 years to slowly make its way out of the dense center of the sun. Then it took about 8 minutes to travel through space to Earth.
Every warm moment on this planet is ancient starlight finally arriving.
You are being heated by energy made inside a star.
Not as a metaphor.
Literally.
What E = Mc² Means
E = mc² is a formula that says:
Energy and mass are the same thing, just in different forms.
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E stands for energy.
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m stands for mass.
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c is the speed of light, which is an incredibly large number.
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c² means the speed of light multiplied by itself.
So the equation means:
Energy equals mass times a huge number.
That huge number tells you that even a tiny bit of mass contains an enormous amount of energy.
Why this matters
In everyday life, mass feels solid. A rock, a person, or a planet seems like solid stuff. Energy feels different. Light, heat, electricity, and motion feel invisible and active.
But Einstein showed that mass is really just energy that is packed together very tightly.
When a small amount of mass disappears, it turns into a huge amount of energy.
How The Sun Uses It
Inside the Sun, hydrogen atoms smash together and turn into helium. The helium weighs a tiny bit less than the hydrogen that made it. That missing mass becomes energy.
That energy comes out as light and heat. It travels through space and warms Earth.
So sunlight is literally made from matter that turned into energy.
The Big Idea
Nothing in the universe is truly “just stuff.”
Everything is energy in a slow, frozen form, or energy in a fast, moving form.
E = mc² is the bridge that shows they are the same thing.
A Deeper Way to Understand E = mc²
A powerful way to think about E = mc² is this:
Mass is energy that has been slowed down.
Energy is mass that has been allowed to move.
A rock feels solid because its energy is locked into a tight, stable pattern. Light feels weightless because that same energy is flying through space at the maximum possible speed.
A useful metaphor is money.
Mass is like money stored in a bank account.
Energy is like money being spent.
They are the same thing in different forms. A tiny amount of mass is like a small deposit that earns insanely high interest. When that mass is converted, it releases a huge amount of usable energy. That is what c² represents. It tells you how powerful stored mass really is.
Why the Speed of Light Is in the Equation
The speed of light is not just fast. It is the ultimate speed limit of the universe. Nothing with mass can reach it. Only things with no mass, like light, can move that fast.
So anything with mass has energy trapped inside it because it cannot move at that speed. Light is energy that is already moving at the speed limit.
E = mc² is the exchange rate between energy that is locked in place and energy that is moving freely.
How Gravity and Spacetime Fit In
Newton thought gravity was a force pulling objects together. Einstein realized something much stranger. Gravity is not a pull. It is a bend.
Imagine spacetime as a stretched rubber sheet. Put a bowling ball on it and the sheet sinks. Now roll a marble nearby. The marble curves toward the bowling ball, not because it is pulled, but because the surface itself is bent.
Mass bends spacetime.
Objects move along those bends.
That is gravity.
Earth is not being pulled by the Sun. Earth is moving along the curved spacetime created by the Sun’s mass.
How Einstein Discovered This
Einstein noticed something strange about gravity.
If you are in a falling elevator, you feel weightless. If you are floating in space, you also feel weightless. Your body cannot tell the difference.
That meant gravity and acceleration were deeply connected.
So Einstein asked a radical question. What if gravity is not a force at all? What if it is geometry?
He used math to show that mass and energy tell spacetime how to curve, and curved spacetime tells matter how to move. This became the theory of general relativity.
Later, scientists proved him right by measuring how light bends around stars and how time slows down near heavy objects.
The Big Picture
Mass is not just stuff.
It is energy that curves reality around it.
When you stand on Earth, you are not being pulled downward.
You are standing inside a bend in spacetime made by Earth’s mass.
When sunlight warms your skin, you are feeling matter that turned into energy inside a star.
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Everything is energy.
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Some of it moves.
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Some of it curves space.
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Some of it becomes you.