Physics Help Forum Schwarzschild Radius help

 Special and General Relativity Special and General Relativity Physics Help Forum

 Sep 27th 2018, 06:28 AM #1 Junior Member   Join Date: Sep 2018 Posts: 7 Schwarzschild Radius help I have been trying to calculate the radius of a blackhole using Scharzschild Radius: R = 2GM/C2 But when I compare my answers to sample question problems, I am consistantly getting different answers. For example A black hole with M (solar) = 3.7 x 10^6M I plug in: (2x(6.67x10^-11)(3.7 x 10^6))/(3x10^8)^2 But the answer I get is: 5.48e-21 The sample problem says it should be: 0.08 au or 16R I have the same issues with every other one too And it doesn't matter what I do -whether I convert Msolar to KG or try to break down the equation further, I still get different answers to those provided. I am not sure where I am going wrong.
 Sep 27th 2018, 06:51 AM #2 Senior Member   Join Date: Oct 2017 Location: Glasgow Posts: 445 You've missed out the solar mass (1 solar mass = $\displaystyle 2 \times 10^{30}$ kg), which needs to be included so the units are in SI. You should have $\displaystyle R = \frac{2 \times 6.67 \times 10^{-11} \times 3.7 \times 10^6 \times 2 \times 10^{30}}{(3 \times 10^8)^2} = 1.482 \times 10^{9} m = 0.0099 AU$ topsquark and Pmb like this.
 Sep 27th 2018, 07:31 AM #3 Junior Member   Join Date: Sep 2018 Posts: 7 Thankyou!