"As for the forces, electromagnetism and gravity we experience in everyday life. But the weak and strong forces are beyond our ordinary experience. So in physics, lots of the basic building blocks take 20th- or perhaps 21st-century equipment to explore"

This quote by Edward Witten is referring to the 4 basic forces of nature: electromagnetism, gravity, weak force, and strong force. Electromagnetism and gravity are forces that we experience in our daily lives, while the weak and strong forces are beyond our ordinary experience. This indicates that in order to check out and comprehend these forces, we require to utilize sophisticated innovation and devices from the 20th or 21st century. Witten is emphasizing the importance of modern-day innovation in the field of physics, as it is vital for us to be able to explore and understand the basic forces of nature.