In the RHIC collider, gold ions are accelerated to about 99.7 percent of the speed of light. What is the resulting relativistic factor gamma?

1. Gamma is 1 divided by the square root of (1 minus v squared over c squared). 2. Substitute v = 0.997c, so v squared over c squared is 0.997 squared, which is about 0.994. 3. 1 minus 0.994 leaves about 0.00599, and its square root is about 0.0774. 4. 1 divided by 0.0774 gives gamma of about 12.9. 5. 1.4 and 7.1 correspond to much lower speeds, and 99.7 simply restates the percentage of light speed rather than computing gamma. 6. So 12.9 is correct, matching a time dilation and length contraction factor of about 13. _Source: OpenStax Physics (CC BY 4.0), Ch 10 "Special Relativity", section 10.2 Consequences of Special Relativity_