Let's denote each gold bar from 1 to 9. We will begin by splitting them up into groups of 3: (1, 2, 3), (4, 5, 6), (7, 8, 9). Thus, we can measure group (1, 2, 3), against group (4, 5, 6). We will figure out what group the light bar is in, depending on the outcome of the measurement:

1. Group (1, 2, 3) is heavier than Group (4, 5, 6), suggesting that the light bar is within group (4, 5, 6)
2. Group (1, 2, 3) is lighter than Group (4, 5, 6), suggesting that the light bar is within group (1, 2, 3)
3. Group (1, 2, 3) is equal to group (4, 5, 6), suggesting that the light bar is within group (7, 8, 9)

Now let's denote the group that contains the light gold bar as (A, B, C). We can now use the same application of splitting the bars into 3 groups; in this case, they are just split into A, B, and C. We can now measure A and B against each other to find the light bar:

1. A is lighter than B, suggesting that A is the light gold bar
2. A is heavier than B, suggesting that B is the light gold bar
3. A is equal to B, suggesting that C is the light gold bar

Therefore, we have found the light gold bar in just two measurements.