This seems so simple to me...maybe I'm just not educated enough to understand? When the sun is out in full view, "space" is not visible to the human eye. That's why, during the day, when we walk out...we can't see stars. Only at night, when the sun is gone, will we be able to see the stars. Yes, astronauts talk about seeing stars but they're also on the back side of the moon or there over night or behind a celestial body that blocks sunlight. Hence the reason they'll be able to see stars.