1. Less than 300 supernova fragments have been found. At the rate that stars explode, there would be much more if the universe was billions of years old.
2. The moon gets farther from us a few inches every year. This is no problem for a young earth, but for those who believe in an earth about 4.5 billion years old, this creates a problem; because only 1.2 billion years ago the moon would have been almost touching the earth!
3. Because comets loose material over time, the longest they can last is about 10,000 years. If the universe is billions of years old, why do we still have comets?*
4. Earth's magnetic field is slowly decreasing. According to the rate it is decreasing, the oldest it can be is 25,000 years.
5. The oil under the ground is under pressure, and it could only be under that pressure for about 10,000 years before it would shoot out of the ground!
6. The speed of the earth's spin is also gradually decreasing. In fact, a "leap second" has to be added to the calendar every year, to every other year. Obviously, at one time the earth was spinning faster. This is no problem for an earth about 6,000 years old, but it is a big problem for an earth billions of years old!
Source: Dr. Kent Hovind, "The Age of the Earth", Creation Science Evangelism, 2007, Tennessee.
*Note: To counter this argument, evolutionists have come up with the theory that comets are being constantly created in some sort of comet cloud, way out in space. However, until they actually find this amazing cloud, the question remains unanswered.