In people's minds, the universe is vast.
The number of celestial bodies in the universe is unknown, while the sand on Earth is known.
So when people describe the vastness of the universe, they always say that there are many more stars in the universe than there is sand on Earth.
<h1 class="pgc-h-arrow-right" data-track="4" is this really the case >? </h1>
In response to this problem, the American scientist David Brattner has really calculated, he once led his own scientific research team to calculate the total amount of sand on the earth and the number of stars in the universe.
The results were unexpected.
In fact, both sand and the number of stars in the universe are difficult to calculate. Although the total amount of sand on Earth is fixed, there is no clear volumetric standard for sand to measure, resulting in a large variability that creates an exponential level gap.
Looking at the number of stars in the universe, because the true size of the universe cannot be estimated by humans, the true number of stars in the universe cannot be determined.
The two are difficult to compare, so we can only compare the number of stars in the observable universe with the amount of sand of predetermined size.
Let's start by estimating the number of stars in the observable universe. According to the latest observations from Hubble, the observable universe is a spherical space with the Earth as the center of the sphere and a radius of 46 billion light years.
There are about 2 trillion galaxies in it.
We calculate the average size of these two trillion galaxies by Milky Way standards.
The Milky Way is between 100,000 and 180,000 light-years in diameter and contains between 150 billion and 400 billion stars. Let's take the maximum value of 400 billion to calculate.
The observable universe has about 200 billion Galaxies similar to the Milky Way, each with about 400 billion stars.
So the total number of stars in the observable universe is about 800 trillion billion.
However, it is more difficult to calculate the amount of sand on Earth than the number of stars in the universe
The simplest and most cursory approach is to start with the Sahara Desert, which contains half of the earth's sand, which is the result of a rough estimate by scientists based on data from Earth's remote sensing satellites, rather than a random guess.
Let's first count the number of beaches and deserts on the earth, first calculate the sand of the Sahara Desert, and then multiply by 2 to get the total amount of sand on the earth.
Scientific models estimate that the volume of a piece of sand is 0.0368 cubic millimeters, 1 cubic millimeter has 27.174 sand, then 1 cubic meter has 27.1 billion sand.
The Total Area of the Sahara Desert is 9.06 million square kilometres (9,060 billion square metres). The average depth of its desert is about 150 meters. So the total volume of sand in the Sahara Desert is 13.59 trillion cubic meters.
If there are 27.1 billion sands per cubic meter, the total amount of sand in the Sahara Desert is about 368.3 billion pieces of sand.
Then the total amount of sand on Earth is 736 million billion billion pieces of sand.
The total number of stars in the observable universe is only 800 trillion billion. Not enough for a fraction of the amount of sand in the Sahara Desert.
Although the number of stars in the universe is only a fraction of the total amount of sand on Earth, the total number of celestial bodies in the universe is far greater than the total number of sand on Earth.
Because celestial bodies include not only stars, but also white dwarfs, neutron stars, black holes, comets, planets, moons, etc.
The total number of all celestial bodies in the solar system is about 1.27 million.
Suppose a star system contains the same number of objects as the solar system.
Then the total number of celestial bodies in the universe is at least 1,016 trillion billion billion. This amount far exceeds the total amount of sand on Earth.
So, in the observable universe, there are not as many stars as there is sand on Earth, but the number of all celestial bodies in the universe is much greater than the number of sand on Earth.