I have advanced several indicators that the Earth is billions of years old. Radiocarbon dating, for one. Then there's the stratification of the sedimentary rock. There's core samplings of ice and lakebed's. Rings in tree's - including fossilised trees.
http://pubs.usgs.gov/gip/geotime/contents.html
Now, I'll grant you that we're only within a couple of percent of the true and accurate ages of these oldest rocks, and I'll grant you that so far all we're able to do is fix a lower limit for the age of the Earth, but I have to say that 6,000 years is looking almost as unlikely as 6 years.
http://pubs.usgs.gov/gip/geotime/contents.html
Now, I'll grant you that we're only within a couple of percent of the true and accurate ages of these oldest rocks, and I'll grant you that so far all we're able to do is fix a lower limit for the age of the Earth, but I have to say that 6,000 years is looking almost as unlikely as 6 years.