Why doesn’t the thermosphere feel warm even though many of the sun’s ultraviolet rays are present?

The thermosphere lies between the exosphere and the mesosphere. “Thermo” means heat, and the temperature in this layer can reach up to 4,500 degrees Fahrenheit. If you were to hang out in the thermosphere, though, you would be very cold because there aren’t enough gas molecules to transfer the heat to you. This also means there aren’t enough molecules for sound waves to travel through.