The Universe Was Created Recently
The universe is only several thousand years old.
Comets are an example of a natural clock within our solar system. With each orbit around the sun, comets lose considerable mass. They cannot be very old because they cannot survive many orbits.
To get around this problem, many astronomers assume there is a vast cloud of comets out near the edge of the solar system, which releases new comets every so often. This imaginary cloud is called the "Oort Cloud," named after the astronomer who proposed it. The problem is that there is no observational evidence such a cloud exists at all.
Each year our knowledge of astronomy increases with new evidence concerning the origin of our solar system, our galaxy, and our universe. While it is possible to make assumptions beyond what can be observed and verified, the heavens continue to bear witness to recent creation.