Physics
Energy-Time Uncertainty Principle
Quick fact
The energy-time uncertainty principle implies that energy conservation can be violated by an amount ΔE, but only for a time Δt such that ΔE·Δt ≥ ħ/2. This fleeting violation enables the existence of virtual particles that carry forces.
Why this is interesting
You may have heard that energy is always conserved. But in the quantum world, nature allows a tiny 'loan' of energy—if it's paid back quickly enough. What allows this loophole?