Most of the matter in the universe is invisible. We can’t see it, but we know it’s there because its gravity shapes galaxies, bends light, and holds cosmic structures together. This mysterious substance is called dark matter – and it makes up about 85% of all matter.

Scientists don’t yet know what dark matter is made of. Many possible candidates are being considered, covering a huge range of masses and properties:

• Axions – very light, neutral particles first proposed to solve a problem in particle physics, and now leading dark matter candidates.
  
  
• ALPs (Axion-Like Particles) – similar to axions but predicted by a wider range of theories (e.g. string theory), with different possible masses and interactions.
  
  
• WIMPs (Weakly Interacting Massive Particles) – heavier particles that could interact via the weak nuclear force, long a favorite dark matter candidate.
  
  
• Sterile Neutrinos – hypothetical cousins of normal neutrinos, but without any of the known interactions except gravity.
  
  
• WIMPzillas – ultra-heavy particles that could have formed in the extreme conditions of the early universe.
  
  
• Primordial Black Holes – tiny black holes formed shortly after the Big Bang, acting like massive dark matter particles.
  
  
• Fuzzy Dark Matter – extremely light particles with wave-like properties on galactic scales, possibly influencing the structure of galaxies.
  
  

Identifying which – if any – of these candidates is real would revolutionize our understanding of the cosmos.