Bodies are subject to continuous temperature balance with other bodies. They constantly absorb and emit energy. This also takes place in vacuum.
<aside> 📌 Presumtion: Radiant energy does not require a medium and can travel in a vacuum. ↓5↓
</aside>
For the phenomenon of blackbody radiation, PLANK formulated that energy radiation can only take place in portions. The energy absorption of bodies thus also takes place in portions.
The energy portions were later called quanta and subsequently photons.
<aside> 📌 Presumtion: The exchange of radiant energy takes place through photons. ↓6↓
</aside>