National Ignition Facility

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in Livermore, California, is a massive laser-based inertial confinement fusion (ICF) research equipment. In order to induce nuclear fusion reactions, NIF employs lasers to heat and compress a tiny quantity of hydrogen fuel. NIF's aim is to accomplish high-energy fusion ignition and to enhance nuclear weapon maintenance and design by investigating the behavior of matter under nuclear weapon conditions. NIF is the world's largest and most energetic ICF device, as well as the world's largest laser.

This is the world's biggest laser apparatus, costing roughly $3.5 billion to build. This is quite a large number that makes it included in this list of the most expensive science experiments. This project intends to create nuclear weapons by using lasers to trigger nuclear fusion events. This gadget aids in the development of nuclear weapons as well as the production of carbon-free energy.

Price: Around $3.5 billion