3 | | A uniform cloud of gas will collapse under gravity if its gravitational timescale is shorter than its thermal timescale. That is, if the freefall time of the gas, [[latex($t_{ff} ~ 1/(G\rho)^{1/2}$)]] is less than the time it would take for sound waves to attempt to equilibrate the matter distribution, or the sound-crossing time, [[latex($t_{sc}=R/C_s$)]], where R is the radius of the cloud and Cs is its sound speed. |

| 3 | A uniform cloud of gas will collapse under gravity if its gravitational timescale (the freefall time, [[latex($t_{ff}$)]]) is shorter than its thermal timescale (sound crossing time, [[latex($t_{sc}$)]]). That is, if [[latex($t_{ff} \propto 1/(G\rho)^{1/2}$)]] is less than [[latex($t_{sc}=R/C_s$)]], where R is the radius of the cloud and Cs is its sound speed, a cloud is unstable to collapse. Setting these equal and solving for r gives an estimate of the Jeans length, |

| 4 | |

| 5 | [[latex($\lambda_J \propto (Cs^2/G\rho)^{1/2}$)]] |