It has been estimated that within the observable universe there might be as many as a septillion stars.

While each of them is far larger than the Earth, they all differ in terms of age, size, color, and composition.

Despite being very far away away we know a surprisingly large

amount about them through observation and an understanding of the basic

units of matter. Learn more about stars, how they're born and they die, on this episode of Everything Everywhere Daily. When humans first looked up at the night sky they could see lights, but they had no clue what they were.

The first theories held that they were either holes in the firmament with light shining through,

or that there were lights that were somehow fixed in the sky,

except for the fact that there were a few of those

lights that actually moved. Whatever they were, they were very clearly different

than the sun and the moon. Except that some ancient Greek and Islamic astronomers thought that the stars might just be the same thing as our son.

This idea was revived in 1584 by the Italian astronomer Giordano Bruno.

Bruno not only thought that the stars were like our son, but that they also

had planets like Earth, and possibly people just like us. His theories were mostly rejected

by his contemporaries and he was later tried for heresy, but within a century

the idea that the stars were like our sun took hold. But if the stars were like our

sun, then what exactly was the sun? For the longest time people thought that the sun was a

ball of fire and to be honest it wasn't a totally unreasonable assumption given what

people knew at the time it was hot like fire and it was a similar color to fire.

As science advanced and we learned more about things like heat, energy, and the size of the sun,

some things just didn't add up.

One 19th century scientist in particular, Hermann von Helmholz, tried to figure out what made the sun

give off energy. First, he assumed that the sun was on fire and it was literally undergoing

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