We are planning on doing a class about the universe on Saturday, although I still don´t know how to do it. But I have been trying my math out, and this may help show how big the universe is:

I wanted to know how many grains of sand is in a big desert. Well the Sahara desert is the worlds largest hot desert, covering most of Northern Africa. It is about 3,500,000 square miles.

I don´t know on average how deep the sand is in that desert. I imagine if you dig deep enough you would find regular dirt, or clay, or rock. I read that some of the sand dunes are 600 feet high, but there are also a lot of low spots, so with my expertise (a wild guess), I estimated the sand being an average of 300 feet deep.

I took another guess, and guessed that 1,500 grains of sand is in a square inch. A fine sand would probably be more, but a big grain sand might be less.

So, supposing there is an average of 1,500 grains of sand in a square inch, here is the number of grains of sand I calculated there to be in a desert 3,500,000 square miles, and the sand being 300 feet deep: 11,767,472,640,000,000,000,000.

That is a big number, too big to even comprehend.

And now, let´s try to get a number on the number of stars in the universe. By the way, the largest known star in our galaxy is called VY Canis Majoris. I heard that if the Earth were the size of a golf ball, VY Canis Majoris would be the size of Mount Everest. Louie Giglio spoke about that, and he said 7 quadrillion Earths can fit inside of Canis Majoris. If the Earth were the size of a golf ball, that would be enough golf balls to cover the state of Texas, 22 inches deep. There is a photo of Canis Majoris.

Anyways, back to trying to figure out how many stars are in the universe. There is estimated to be between 200 and 400 billion stars in our galaxy, the Milky Way Galaxy.

A lot of astronomers think there are hundreds of billions of galaxies in the universe, but nobody really knows for sure.

If there are 150 billion galaxies in the universe, and each galaxy contains on average 100 billion stars, then there would be 15,000,000,000,000,000,000,000 stars in the universe.

And so here is the number of grains of sand I estimated there to be in the Sahara Desert, compared to the number of stars in the universe I estimated:

Grains of sand in Sahara Desert: 11.7 sextillion

Stars in Universe: 15.0 sextillion

Sextillion is a number followed by 21 zeros.

And here is a math problem for you:

The Milky Way Galaxy is estimated to be 500,000 light years in diameter. Light travels at 186,000 miles per second. How many miles wide is the Milky Way Galaxy?

Also, feel free to check if I calculated the other stuff right, and tell me if I didn´t. It´s really not very hard to do.