naked eye

This means the colour olo could not been seen by a person's naked eye in the real world without the help of specific stimulation.

For something not visible to the naked eye, organic chemicals are a huge US export for the UK, totalling close to £3bn last year.

Even during a partial eclipse, it is never safe to look directly at the Sun with the naked eye as it can cause eye damage, including blindness.

Though he admits comparing reports from recent years has got easier due to mobile phone and digital cameras being more sensitive to capturing the aurora than the naked eye.

Most are expected to be visible to the naked eye, though not all seven.