Meteoroids enter Earths atmosphere from outer space traveling at hypersonic speeds of at least 11 km/s (7 mi/s) and often much faster. Despite moving through the rarified upper reaches of Earths atmosphere the immense speed at which a meteor travels nevertheless rapidly compresses the air in its path, creating a shock wave. The meteoroid then experiences what is known as ram pressure. As the air in front of the meteoroid is compressed its temperature quickly rises. This is not due to friction, rather it is simply a consequence of many molecules and atoms being made to occupy a smaller space than formerly. Ram pressure and the very high temperatures it causes are the reasons few meteors make it all the way to the ground and most simply burn up or are ablated into tiny fragments. Larger or more solid meteorites may explode instead in a meteor airburst.