The escape velocity is the minimum velocity required for a non-propelled object to escape from the influence of the gravitational force of the primary object. The magnitude of the escape velocity of the Earth is 11.1 km/s. What is the temperature at which hydrogen molecules attain the rms speed equal to the escape velocity of the Earth? According to the kinetic theory of gases, the average kinetic energy of any gas is related to its temperature. The mass of hydrogen molecules can be calculated by taking the ratio of its molar mass to Avogadro's number. Now, rearranging the equation for kinetic energy and substituting the known quantities, the temperature required to attain the escape velocity is calculated. The estimated temperature is a few orders of magnitude higher than the temperature at high altitudes of Earth's atmosphere. This means the hydrogen molecules cannot escape from the Earth's atmosphere. However, during multiple collisions, significant hydrogen molecules attain the escape velocity allowing the loss of hydrogen from Earth's atmosphere.