predictions in astronomy are WAY off? I was thinking. scientists use triangulation to estimate the distance from earth to stars. wouldn't this only work properly in 3-D?
Triangulation is only used for the realtively nearby stars - those within roughly 100 light years or so. Beyond that, other methods (increasingly more sophisticated and difficult) are used to find distances to further stars, to the nearer galaxies, to the mid-distance galaxies, to the furthest galaxies...
The fourth dimension is time, and we take the into account in all of our calculations where it would matter. If there are more than 4 dimensions, like string theory would predict, they don't make enough of a difference for us to notice it except when trying to merge general relativity with quantum mechanics.
I assume you are talking about pre and post theory of relativity astronomical observations. "3-D" observations, without considering space-time, are extremely accurate until speed nears the speed of light, or gravity becomes extremely intense. Most common observations were unchanged, and the ones that scientists judge may be affected by relativity have been looked at or are being looked at currently.
the 4th is time and time to us is limited to the mass of our planet ,in other words every mass has dif.time so in away you are right the 4th dimension kinda messes up the math on how old the universe is -being the age only to earth and not other masses
Remember, you can still picture a 2-d object in a 3-d world and be absolutely correct, the same principle applies here. A three dimensional object can be pictured is a 4-d world. It is only the reverse which is impossible.