What motivated and sustained the long distance commerce

Silk Roads, Sea Roads, and Sand Roads?

Explanation:

The desire of elites for hard-to-find luxury items

from distant parts of the Eurasian network, as well as

the accumulation of wealth, especially among

merchants who participated in the trade, motivated

long-distance commerce. Sustaining the commerce were the support of empires and smaller states that benefited directly from the trade; the spread of religious traditions, including Islam and Buddhism, that through shared beliefs tied merchants and sometimes whole societies together over wide regions; and the development of technologies like larger ships and the magnetic compass.

radiative zone

explanation    

radiative zone is the layer of the sun which energy is transferred away from the core by radiation. although, the core is the only part of the sun that produces an appreciable amount of heat through fusion. in fact, 99% of the energy produced by the sun takes place within 24% of the sun's radius.