Era of Nucleosynthesis – Epochs of the Universe (Mission 05)

This is your mission 05 of the epochs of the Universe.

The Era of Nucleosynthesis is where the fusion of protons and neutrons occurred and formed the first nuclei.

So if you want to travel back in time and experience the Era of Nucleosynthesis, then this article is for you.

Let’s get started!

Table of Contents

Mission 05 of the Epochs of the Universe – Era of Nucleosynthesis

You are now in the fifth epoch of the Universe. As you continue advancing through the epochs, things now start to come together and make sense. 

You have explored all the stages of the Universe’s evolution from the beginning until now. In each era, you see some development.

Now let’s jump right in and explore the Era of Nucleosynthesis.

Mission Timeline – Era of Nucleosynthesis

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Mission Map – Era of Nucleosynthesis

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Mission Data – Era of Nucleosynthesis

  • Current Epoch: Era of Nucleosynthesis.
  • Age of the Universe: Between 0.001 seconds and 3 minutes.
  • Size of the Universe: Around 300 light-years in radius.
  • Current Temperature: Between 10^9 Kelvins and 3000 Kelvins.

Mission Briefing – Era of Nucleosynthesis

The Era of Nucleosynthesis is where the fusion of protons and neutrons occurred and formed the first nuclei. It happens immediately after the Particle Era, between 1 millisecond and three minutes after the Big Bang.

In this epoch, we will see how the atomic nuclei for light elements are formed and even underwent fusion to form the heavier nuclei, such as the helium nuclei.

What were the first atomic nuclei to be formed?

What was the percentage of each element nuclei in the Universe during this epoch?

What was the ratio of hydrogen nuclei to helium nuclei in this era?

Let’s explore the answers to these questions and much more.

What Do You See?

As we saw in the previous epoch, the Universe is expanding, but slower than during the Inflationary Period. 

The size of the Universe has increased to about 300 light-years in radius. 

A light-year is defined as the distance that light travels in one Julian year. 

One light-year is about 6 trillion miles (9 trillion km). So it might be hard to fathom that this is the same Universe that was a tiny singularity in the first epoch, the Big Bang. 

The Universe is now a vast space filled with a “soup of particles.” 

As stated in the Mission Data, you can see that the Universe is getting older as it expands. 

The Era of Nucleosynthesis happens between 0.001 seconds and 3 minutes after the Big Bang. 

Within this timeline, the fusion of the protons and neutrons continued and combined into the first atomic nuclei, the hydrogen nuclei. 

A nucleus is defined as a positively charged central core of an atom that comprises protons and neutrons. 

Some of the protons and neutrons fused further to form the helium and lithium nuclei. 

The fusion did not last for long because the Universe was so dense that the fused nuclei broke apart again after they formed. 

The fusion and breaking apart of the nuclei continued until three minutes after the Big Bang, when the Universe was now cool enough.

In terms of the mass of the nuclei, different masses of the nuclei elements are formed. 

In this era, 75% of the matter was hydrogen nuclei, 25% helium nuclei, and trace amounts of lithium and deuterium nuclei.

The current abundance of light elements in the Universe reflects what occurred during the Era of Nucleosynthesis. 

With the fusion and breaking of particles to form the nuclei, the Era of Nucleosynthesis ended with a primordial mix of hydrogen, helium, and small traces of lithium and deuterium nuclei that later proceeded into the making of the first stars. These were the first nuclei to be formed in the Universe.

We see how the nuclei will bind with other particles in the subsequent epochs to form atoms and even later galaxies and stars.

What Do You Feel?

Between 0.001 seconds and 3 minutes after the Big Bang, the temperature and pressure of the Universe allowed the nuclei fusion to happen, giving rise to nuclei of the first atomic elements. 

The temperature was between 10^9 Kelvins and 3000 Kelvins. Towards the end of the Era of Nucleosynthesis, both the Universe cooled, and the density dropped enough that the nuclear fusion ended. 

The Era of Nucleosynthesis produced very few elements heavier than lithium due to the lack of a bottleneck. 

A bottleneck in this context is the absence of a stable nucleus with 8 or 5 nucleons. Thus, the absence of larger stable atoms limited the amounts of lithium-7 produced during the Big Bang Nucleosynthesis. 

So far, the only stable nuclei proven experimentally to have been made before or during the Era of Nucleosynthesis are helium-3, helium-4, lithium-7, deuterium, and protium.

This epoch begins after matter (particles) has annihilated all the remaining anti-matter (anti-particles). Thus, all the matter is “frozen out,” meaning that matter is no longer spontaneously generated to or from the photons. 

From the simple thermodynamics’ arguments, you can calculate the ratio of protons to neutrons during fusion depending on the Universe’s temperature during this era. 

The fraction of the protons is higher than that of the neutrons because the higher mass of neutrons gives rise to premature decay of neutrons to protons with a half-life of around 15 minutes. 

Half-life is the time interval required for one-half of the atomic nuclei of a radioactive sample to decay.

What is Happening? Scientific Explanation

Here is some scientific background on the Era of Nucleosynthesis.

Appearance

In this epoch, we see how the particles fuse to form the nuclei. At this point, the protons and the neutrons combine into the first atomic nuclei, hydrogen. 

Some particles fused further into helium and lithium nuclei. However, the Universe was so dense that the nuclei split apart again as soon as they formed. 

So as new ones were forming, others were breaking apart. The fusion and the breakup continued as the temperature dropped. Finally, when the Universe was cool enough, the fusion ended. 

At the end of the Era of Nucleosynthesis, the Universe was left with 75% hydrogen nuclei, 25% of helium nuclei, and trace amounts of lithium and deuterium nuclei. 

The Universe was now a primordial mix of hydrogen, helium, lithium, and deuterium.

The Universe has continued to expand, hence the increase in the size of the Universe, from being slightly bigger than a grapefruit in the Particle Era to now being around 300 light-years in radius. This is such a big difference.

As the Universe continues to expand, it cools down as the temperature drops. The Universe’s temperature was between 10^9 Kelvins and 3000 Kelvins during this epoch. 

As the temperature dropped, the Universe cooled enough that the fusion ended. 

Time

The Era of Nucleosynthesis happens after the formation of particles in the Particle Era. It occurs between a timeline of 0.001 seconds and 3 minutes after the Big Bang. In that period, the Universe expanded rapidly by a significant factor.

Also, the particles fuse and break apart as they form the nuclei. Thus, at the end of this epoch, the Universe contained a primordial mix of hydrogen nuclei, helium nuclei, and trace amounts of lithium and deuterium nuclei.

The duration for the Era of Nucleosynthesis is around 180.001 seconds.

Mission Summary – Era of Nucleosynthesis

In summary, the Era of Nucleosynthesis is the epoch where the particles fuse to form the nuclei. It began when the Universe was hot and dense enough to allow for the fusion to occur.

The protons and neutrons combine to form the atomic nuclei. The first atomic nuclei to form were the hydrogen nuclei. Then, some particles fused further to form the helium and lithium nuclei. 

The fusion continued as the temperature went down until it was cool enough that fusion ended.  

When the Era of Nucleosynthesis ended, the Universe was left with a primordial mix of the nuclei of hydrogen, helium, and trace amounts of lithium and deuterium. 

The matter was filled with 75% hydrogen nuclei, 25% helium nuclei, and trace amounts of lithium and deuterium nuclei.

The Universe has expanded, and it’s now big compared to the previous epoch, the Particle Era. 

The size of the Universe is now around 300 light-years in radius. This was such a massive expansion.

The timeline of the Era of Nucleosynthesis is between 0.001 seconds and 3 minutes, which is 180.001 seconds. Therefore, the temperature of the Universe is between 10^9 Kelvins and 3000 Kelvins.

More developments in the Universe occur in the following epochs.

Addition Mission Resources – Era of Nucleosynthesis

Here are some frequently asked questions about Mission 05: Era of Nucleosynthesis.

What Is Primordial Nucleosynthesis?

Primordial nucleosynthesis is when protons and neutrons combine to form the nuclei, the hydrogen nuclei, and heavier nuclei, including helium nuclei. 

The abundance of light elements in the Universe reflects what occurred during this epoch.

What Caused the Era of Nucleosynthesis to End?

By the time the Universe cooled to a temperature of about 3000 Kelvins, the particles had insufficient energy to undergo further reactions. 

This resulted in nucleosynthesis ending after the fusion of particles that formed the hydrogen, helium, lithium, and deuterium nuclei.

What Was the First Element Nuclei to Form?

During the nucleosynthesis process, protons and neutrons combined to form the nuclei. 

The first nucleus to form was the hydrogen nuclei. Hydrogen has the simplest nucleus possible. Its nucleus has one proton and no neutron.

Why Were Heavier Elements Not Formed?

As the Universe expanded, it cooled as the temperature dropped. 

The energy became insufficient for the particles to undergo any more reactions to form heavier elements. 

The heavier elements have their origins in the interiors of the stars.

Epochs of the Universe: Mission Selection