The NIST (National Institute of Science and Technology) has developed a watt balance that just about anybody can build. A watt balance is a device to determine Planck's Constant to a high degree of accuracy. The device is a balance that uses a known weight on one side and a current carrying coil on the other. A number of high precision watt balances have been built. Now the NIST has developed one that can be built using Legos for the structure. The total cost is about $634 US. The story is on Phys.Org. NIST physicists build a watt balance using LEGO blocks to measure Planck's constant.

Bill Gill

C is not the speed of light in a vacuum.
C is the universal speed limit.