Comets cannot be older than thousands of years due to their composition of mostly ice, as they typically lose about 1% of their mass every time they orbit the sun. Astronomers know this, yet they also believe that the Solar System is billions of years old. Since comets cannot be millions of years old, many secular astronomers have hypothesized that the comets we see today must have entered the inner solar system relatively recently from a more stable orbit, beyond the eroding effects of the sun. This hypothesized locale is known as the Oort Cloud (named after Jan Oort). The Oort Cloud has never been observed. Science requires that all legitimate phenomena be observable, testable, repeatable, and confirmed by peer review. The Oort Cloud meets none of these criteria. How then can it be called scientific?
However, "young" comets fit perfectly well into the Biblical account of creation, as the universe is only thousands of years old, not millions and billions.
The Oort Cloud hypothesis should not be taught as fact in our schools.