This baffles me, because the device outlined below could create energy ... Theres two tanks A & B with a microscopic gate between them Air in A & B starts at say 25 degrees whenever a faster than average moving molecule approaches the gate in A a sensor opens the gate and lets in pass into B If a slow moving molecule approaches the gate from B, the sensor opens the gate and allows it into A So perhaps after time t, the air in A is at 23 degrees and the air in B is at 27 degrees In theory the 'sorting gate' could be a very low energy device. The temp difference between A & B could be used to drive a heat engine and get energy out. Where is the flaw in this theoretical argument? I cant find one. In theory particle sorting could be done to generate heat differences??