By the ‘strength’ of a material, we usually mean the degree to which it can withstand deformation by an external force.
So, the strongest materials are generally those with high densities because the closer the constituent atoms are, the greater the resistance they have to further compression. For normal matter, however, structural properties also affect strength, so the strongest naturally occurring material on Earth (graphene) isn’t actually the densest (osmium).
There are some states of matter that are very dense and therefore ‘stronger’ than ordinary matter. These forms of matter are generally produced when massive stars collapse under gravity at the end of their lives.
A white dwarf, for example, consists of carbon and oxygen nuclei in a cloud of electrons. Due to quantum effects, the electrons have a ‘degeneracy pressure’ that prevents further compression.
However, at sufficiently high densities, such as in neutron stars, the electron degeneracy pressure can be overcome. Here, the star is prevented from collapsing further by the degeneracy pressure of tightly packed atomic nuclei and free protons and neutrons.
The resulting material is a hundred trillion times denser than anything on Earth. The exact structure of neutron stars is complex and uncertain, but theory suggests there’s a thin layer within neutron stars where matter transitions between ordinary matter at the surface and the ultra-dense matter at the core.
Here, the competition between forces from protons and neutrons creates a variety of shapes, which have been named nuclear pasta. It’s this rigidly bound, super-dense material that scientists believe in the strongest in the Universe. It’s at least 10 billion times stronger than steel.
This article is an answer to the question (asked by Colin Davids, Bridgwater) 'What is the strongest material in the universe?'
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