Tuesday, June 28, 2022
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How many Grains of Sand are there in the World?

Who hasn’t marveled at the sight of sand as it shimmers in the sun for that perfect holiday setting?

From the hot blazing swathes of desert such as the Sahara Desert to the beaches, the stretch of sand is breathtaking.

Doesn’t it make you wonder how many sand grains there are in the world?

Of course, we can’t know the exact number of sand grains in the world but using some calculation, we can come up with a reasonable and close guess. 

Step by Step plan  

To solve this problem, we can go through the following 4 steps:  

Step 1:

We first determine how many sand grains can fit inside a cube with sides measuring 1 meter.

 To do this, let’s first determine the number of sand grains you get when you line them up along a one-centimeter length.

This comes to about 15 to 25 average-sized grain sands.

Let’s take 20 grains as our average number for the sands that will fit along one side of a centimeter cube.

This means the total number of grains in a 1 cm cube will be: 

20 x 20 x 20 = 8,000 grains

Let’s use this to find out the grains that fit in a meter cube. This will be: 

8,000 x 1,000,000,000 = 8, 000,000,000, 000 grains or 8 billion grains. (8 x 10^12)

Step 2: 

Next, we find the volume occupied by sand in the sandy areas of the world.

We can do this separately for the principal areas that have sand. For simplicity, we will focus on two areas: 

  • Beaches
  • Deserts 

Beaches

Let’s assume that the average sandy beach has a width of 30 meters and a depth of 10 meters. 

We need the figure for beach lengths which is the shoreline.

According to NASA, there are 620,000,000 meters of coastline in the world. 31 percent of these shorelines are sandy beaches.

So, the total length of sandy shoreline is: 

31% x 620,000,000 = 192,200,000 m

Using this we can work out the total volume space of sandy beaches as:

192,200,000 x 30 x 10 = 57,660,000,000 m³

Deserts

Note that not all deserts are covered by sand.

Some deserts are ice deserts such as the polar deserts of the Arctic and Antarctica.

We are interested in semi-arid deserts, hot and dry deserts and coastal deserts which are the ones that harbor sands.

 In total there are 23 such deserts in the world. 

This desert land is about 33% of the earth’s dry land surface.

Since the earth’s land surface is about 57,308, 738 square meters in area, this means the total desert area is 33% of 14,832,600,000,000 square meters. This gives:

0.33 x 14,832,600,000,000 =4.8 x 10^12 m²

Also, sand deserts such as the Sahara are only partially covered by sand. The total percentage of desert that is covered by sand is just 20%

So, we can calculate the total sand area of deserts as:

20% x 4.8 x 10^12 = 959,151.600,000 m² 

The depth of the sand in the desert is roughly 100 meters deep before you meet the bedrock.

So, we can calculate the total volume occupied by sand in all deserts as:

 959,151.600,000 x 100 = 95, 915,160, 000, 000 m³

Step 3: 

Get the total volume of all the sand in both the deserts and beaches.

For this, we simply sum up the volume figure which we obtained for the deserts and the beaches in step 2. 

95, 915,160, 000, 000 + 57,660,000,000 = 9.6 x 10^13 m³

Step 4: 

We are now ready to get the total number of sand grains.

We take the figure we obtained in step 3 and multiply this by the figure we got in step 1 for the number of sand grains in the one-meter cube. 

9.6 x 10^13 x (8 x 10^12) = 4.6 x 10^23 sand grains

Since this figure excludes the sand in rivers like the Nile, it’s a very conservative figure.

Nevertheless, it far exceeds the number of stars in the Milky Way which is 200 billion (2 x 10^11), and is comparable to the number of stars in the universe which is estimated to be 1 x 10^22 to 1 x10^24.

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The Boffins Portal Team
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