Question

Which of the following formed latest in the universe? a) quarks b) protons and neutrons c) hydrogen atoms d) helium nuclei e) gluons

Short answer

Answer: c) Hydrogen atoms

Step-by-step solution

Understand the chronology of particle formation in the early universe

In the very early stages of the universe, it underwent several phases as it cooled down. The Planck epoch, the briefest and earliest phase of the universe, was characterized by extremely high temperatures and energy levels. During this time, all the fundamental forces were combined, and particles like quarks and gluons were present. As the universe expanded and cooled, these particles combined to form protons and neutrons, which eventually combined to form atomic nuclei like hydrogen and helium.

Analyze the order in which the given particles formed

Based on our understanding of the early universe, it's now possible to arrange the given particles in a chronological order: 1. Quarks and gluons formed first, during the Planck epoch and the quark-gluon plasma phase. 2. Protons and neutrons formed as the universe cooled down further. 3. Helium nuclei formed through successive nucleosynthesis processes. 4. Hydrogen atoms formed during the recombination epoch when electrons and atomic nuclei combined to form neutral atoms.

Choose the latest particle formed

The latest particle to form in the list is the hydrogen atom (c), as it was formed last, during the recombination epoch. So, our answer is: c) Hydrogen atoms