The human eye can (with night vision) see light as low as 0.000003 cd/m².
Bright noon sunshine reaches 1,600,000,000 cd/m².
The "inverse square" (aka the square root) of (1,600,000,000/0.000003) is 23,000,000. The Sun could be 23 million times as far away as it is and we would still (barely) be...