The skin sensors are in the cutaneous and subcutaneous tissues. Inside them, there are various nerves and receptors that can be divided in three groups: mechanoreceptors, nociceptors and thermoceptors. The thermoceptors are the receptors that specify in the acknowledgement of different types of temperatures such as hot and cold. If we touch something with high temperatures (hot or cold) those are the sensors that send the message to our brain.
They developed Trigonometry, used mathematical models to track down the planet Jupiter and developed methods of tracking time that are still used today.
