How many atoms are there in the visible universe?

Everything in the universe, big or small, young or old Atoms.

Each of these modules has a positively charged nucleus, made up of protons and neutrons and negatively charged electrons. The number of protons, neutrons and electrons in an atom determines which element it belongs to. Elemental table And affects how it interacts with other atoms around it. Everything you see around you is just the configuration of different atoms that interact with each other in unique ways.

So everything is made of atoms but do we know how many atoms there are in the universe?

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To begin with, the average human atom has about 7 octalons or 7 × 10 ^ 27 (7 followed by 27 zeros). We do project on this topic and can state that on average 87% of the atoms in the body are hydrogen or oxygen, and 99% of the atoms are elements such as carbon, hydrogen, nitrogen and oxygen” – say scientific experts. Defender. Based on these vast atoms of an individual, you might think that it is impossible to determine how many atoms there are in the entire universe. You are right: since we know nothing about the true size of the entire universe, we cannot know how many atoms there are in it.

However, the number of atoms in can be approximated Notable The universe – a part of the universe that we can see and read – using some cosmological hypotheses and a little mathematics.

The visible universe

The universe was created in time Big Bang 13.8 billion years ago. When it exploded, from a point of mass and infinite temperature, the universe began to expand outward, and then it did not stop.

Since the universe is 13.8 billion years old and the visible universe is so far away from us that light can travel from the birth of the universe, it can be assumed that the visible universe does not expand by more than 13, 8 billion light. Years in all directions. But as the universe continues to expand, so does it. When we look at the distance Galaxy Or the star, the first thing we see is when it first emits light. But until the light hits us, the galaxy or star is farther away than it was when we saw it. Using cosmic microwave background radiation, we can determine how fast the universe is expanding, because this ratio is stable – which is currently the best assumption of scientists (although some scientists think it could be slower) – which means that the visible universe extends 46 billion years across the sister site of light science, all the light Espace.com.

But knowing the size of the visible universe does not tell us everything we know about the number of atoms in it. We also need to know how much matter or things there are.

Cosmic hypotheses

However, that is not the only thing in the universe. In fact, only 5% of the universe is step by step NASA. The rest include Dark energy And Black material, But since they are not made of atoms we do not have to worry about them for this mystery.

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Comply Of Einstein The famous equation is E = mc 2, where energy and mass, or matter are interchangeable, so it is possible for matter to be created or converted into energy. But Cosmic At the level of the universe, we can assume that the magnitude of the created and uncreated object cancels each other out. This means that matter is finite, so there are always the same number of atoms in the visible universe American scientist. This is important because our image of the visible universe is not a snapshot at the right time.

According to our observations about the known universe, the laws of physics governing it are the same everywhere. Along with the assumption that the expansion of the universe is static, on a larger scale, matter is distributed evenly across the universe – a concept known as cosmological principle. In other words, parts of the universe do not contain more objects than others. This idea allows scientists to accurately estimate the number of stars and galaxies in the visible universe, which is useful because most atoms are in stars.

Simplify the equation

Knowing the size of the visible universe and how it is evenly and neatly distributed throughout the subject makes it much easier to calculate the number of atoms. However, we need to make some assumptions before removing the system.

First, it must be assumed that not all atoms are in stars, even if they are not. Unfortunately, we have a very limited idea of ​​how many planets, moons, and space rocks in the visible universe are compared to stars, which means that it is difficult to add them to the equation. But since most of the atoms in the universe are in the stars, we can get a good approximation of the number of atoms in the universe by finding out how many atoms there are in the stars and ignoring everything.

Second, we must consider all the atoms in the universe Hydrogen Atoms, even if they are not. According to him, hydrogen atoms represent 90% of the total atoms of the universe Los Alamos National Laboratory, And an even higher percentage of atoms in stars, we focus on. You will soon see, which makes the calculations much easier.

Do the math

Now it’s finally time to do the math.

To calculate the number of atoms in the visible universe, we need to know its mass, that is, how many stars there are. The visible universe contains approximately 10 ^ 11 to 10 ^ 12 galaxies, and each galaxy is between 10 ^ 11 to 10 ^ 12 stars. European Space Agency. It gives us somewhere between 10 ^ 22 to 10 ^ 24 stars. For the purpose of this calculation, we can say that there are 10 ^ 23 stars in the visible universe. Of course, this is only the best assumption; Galaxies can vary in size and number of stars, but since they cannot be counted individually, we need to do the trick for now.

On average, a star weighs about 2.2 × 10 ^ 32 pounds (10 ^ 32 kilograms). Science ABCThat is, the mass of the universe is about 2.2 × 10 ^ 55 pounds (10 ^ 55 kilograms). Now that we know the mass or size of the object, we need to see how many atoms are in it. On average, each gram contains about 10 ^ 24 protons Fermilab, A national particle physics laboratory in Illinois. This means that it is similar to the number of hydrogen atoms because there is only one proton in each hydrogen atom (hence the reason we developed the previous hypothesis about hydrogen atoms).

This gives us 10 ^ 82 atoms in the visible universe. To put this in context, there are 100,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000.

This figure is only an approximate estimate based on continuous approximations and assumptions. But as far as our current understanding of the visible universe is concerned, it is unlikely to be far from reality.

First published in Live Science.