Era of Nuclei – Epochs of the Universe (Mission 06)

This is your mission 06 of the epochs of the Universe.

The Era of Nuclei ends the fusion of nuclei.

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

Let’s get started!

Table of Contents

Mission 06 of the Epochs of the Universe – Era of Nuclei

Now on the sixth epoch, in the Era of Nuclei, we see what happens after forming the nuclei in the Era of Nucleosynthesis. 

The Universe is now taking shape, from the formation of particles to nuclei. 

Although nothing much happens during this epoch, let’s jump right in and explore this era to understand how what happened helped set the stage for the much bigger changes in the epochs that follow.

Mission Timeline – Era of Nuclei

Mission Map – Era of Nuclei

Mission Data – Era of Nuclei

  • Current Epoch: Era of Nuclei.
  • Age of the Universe: Between 3 minutes and 500,000 years.
  • Size of the Universe: It expanded by a factor of 1,000.
  • Current Temperature: Between 10^9 Kelvins and 3000 Kelvins.

Mission Briefing – Era of Nuclei

After the Era of Nucleosynthesis, you now enter the Era of Nuclei. 

In this epoch, we see what happens to the nuclei after their formation in the Era of Nucleosynthesis. 

All the particles in the Universe are in the form of atomic nuclei, such as hydrogen nuclei, helium nuclei, and trace amounts of lithium and deuterium nuclei. 

The Universe comprises fully ionized particles in matter, which is generally a ball of hot plasma.

Why are the electrons and nuclei separate?

What is the state of the Universe in this epoch?

Is light created in this era?

Let’s answer these questions as we get into more detail about the Era of Nuclei.

What Do You See?

In this epoch, we don’t see much change compared to the Era of Nucleosynthesis. It is almost similar to the previous epoch. 

The only different thing is the fusion of nuclei has ended in this epoch. The Universe is expanding, but at a slower rate; hence its size is increasing.

The size of the Universe has increased by a factor of 1,000 compared to its size in the previous epoch. It is a massive space filled with fully ionized particles.

According to the mission data, you can see that the Universe becomes older as it expands. 

The timeline of the Era of Nuclei is between 3 minutes and 500,000 years after the Big Bang. Within this long period, nothing much happened. 

The fusion of the nuclei has stopped. All the while, the Universe remains just a ball of hot plasma filled with fully ionized particles, i.e., hydrogen nuclei, helium nuclei, and trace amounts of lithium and deuterium. 

Three minutes after the Big Bang, the nuclei fusion ended, and no more atomic nuclei were formed. 

The nuclei fusion could not continue because the temperature became too low. Nevertheless, the temperature remained high enough to keep all the atoms ionized; keep all the electrons from binding with the nuclei until around 500,000 years. 

Photons (particles that produce light) were also scattered in the Universe together with the electrons, but they could not react with each other because they were locked into an equilibrium in which the photons could not escape. 

The Era of Nuclei created a lot of light, but it could not be seen anywhere. The Universe’s density was so high that photons would hit the nuclei or an electron before getting anywhere, causing the Universe not to have light. The Universe became opaque to light. 

The timeline of the Era of Nuclei is between 3 minutes and 500,000 years. In this long period, the nuclei fusion ended because the temperature dropped, making the Universe cool enough for the nuclei fusion to not continue.

As you continue to the next epoch, you will see what happens to the atomic nuclei, electrons, 

and photons.

What Do You Feel?

In the Era of Nuclei, between 3 minutes and 500,000 years, the Universe’s temperature dipped, causing fusion to stop. 

The nuclei formation ended, leaving the Universe with ionized atoms. During this epoch, the temperature of the Universe is between 10^9 Kelvins and 3000 Kelvins. 

The temperatures are too high for the nuclei and electrons to combine to form an atom. We will see this in the following epochs. 

As the Universe was expanding, its density also decreased. However, the density was still too high that photons would hit an electron or the nuclei before getting anywhere. 

The photons were trapped amid a hot ball of plasma of positively charged nuclei and negatively charged nuclei. 

Since photons and electrons are scattered in the Universe, free electrons can absorb the photons of any energy making the Universe opaque to light. 

This means that the photons could produce light, but the light could not get anywhere because the electrons were absorbing the photons. So, there was still no light during the Era of Nuclei. 

The pressure of the Universe continuously decreases as the Universe expands. Pressure is indirectly proportional to volume. So as the volume of the Universe increases, its pressure decreases. 

What Is Really Happening? Scientific Explanation

Here is some scientific background on the Era of the Nuclei.

Appearance

In terms of the Universe’s appearance, the difference is not that big when compared to the Era of Nucleosynthesis. 

In this epoch, the nuclei fusion stops because the temperature became too low for the process to continue. At this point, the Universe is a ball of hot plasma that contains fully ionized particles, free electrons, and photons. 

In the Era of the Nuclei, photons (light particles) created a lot of light, but they could not get anywhere. This is because photons of any energy can be absorbed by free electrons making the Universe opaque to light. 

The free electrons absorb all the photons in the Universe. Also, the density of the Universe was so high that photons would hit an electron or the nuclei before it could travel anywhere.

The size of the Universe has increased as it expanded at a slow rate. It has expanded by a factor of 1,000 compared to the previous epoch, the Era of Nucleosynthesis. 

It might be quite hard to fathom that the tiny singularity that existed in the first epochs would increase in size to such a massive universe filled with fully ionized particles, free electrons, and photons.

As the Universe expanded, its temperature dropped. In the Era of the Nuclei, the temperature of the Universe was between 10^9 Kelvins and 3000 Kelvins. 

The temperature drop causes the nuclei fusion to end, leaving the Universe with 75% hydrogen nuclei, 25% helium nuclei, and trace amounts of lithium and deuterium.

Time

The Era of Nuclei happens after the Era of Nucleosynthesis. The timeline of this epoch is between 3 minutes and 500,000 years after the Big Bang. 

In these 500,000 years, nuclei fusion has ended, and the size of the Universe has significantly increased.

In these 500,000 years, the Universe was too hot for particles to form neutral atoms. At this point, the photons could not produce light as the free electrons were absorbing them. So, the Universe was opaque to light.

This epoch lasts for about 500,000 years.

Mission Summary – Era of Nuclei

Generally, in the Era of Nuclei, the fusion of the nuclei stops, and the Universe continues to expand. 

The temperature became too low for fusion to continue. However, the temperature remained high enough to keep all the particles ionized (electrons free from the nuclei). 

The Universe’s temperature is between 10^9 Kelvins and 3000 Kelvins.

The Universe grew more extensive in the 500,000 years. It expanded by 1000 compared to its size in the previous epoch, the Era of Nucleosynthesis. 

It is a massive space that contains ionized particles, free electrons, and photons. The ionized particles comprise 75% hydrogen nuclei, 25% helium nuclei, and trace amounts of lithium and deuterium.

The photons created light, but it could not get anywhere because free electrons absorb photons making the Universe opaque to light. 

In addition to that, photons would hit an electron or the nuclei before traveling anywhere due to the high density.

The timeline of this epoch is between 3 minutes and 500,000 years after the Big Bang.

The formation of the atoms and stellar bodies will occur in the subsequent epochs.

Addition Mission Resources–Era of Nuclei

Get answers to some of the frequently asked questions about Mission 06, Era of Nuclei.

Why Did Neutral Atoms Not Form?

After the particles binding to form the nuclei in the Era of Nucleosynthesis, they did not bind with the electrons to form a neutral atom. 

That was because the Universe’s temperature was too high for the electrons to bind to the nuclei to form a neutral atom.

Did Light Exist in This Epoch?

The photons (light particles) produced light. Still, they could not travel anywhere because the photons were absorbed by the free electrons, making the massive Universe opaque to light. 

Also, the density was high, and photons would hit the nuclei or an electron before getting anywhere.

What Did the Universe Comprise of in This Epoch?

The Universe was made up of fully ionized particles, free electrons, and photons. 

The fully ionized particles were the hydrogen nuclei, helium nuclei, and trace amounts of lithium and deuterium nuclei.

Epochs of the Universe: Mission Selection