Here's why:

* Conduction requires a medium: Conduction is the transfer of heat through direct contact between particles. These particles can be atoms, molecules, or even electrons in a solid. In a vacuum, there are virtually no particles present to transfer heat.

* No particles, no transfer: Without particles to collide and pass on energy, there is no way for heat to be transferred through conduction in a vacuum.

Think of it this way: Imagine trying to play a game of hot potato with no one else to throw the potato to!

Other ways heat can transfer:

* Radiation: Heat can travel through empty space via electromagnetic waves, like the radiation from the sun.

* Convection: Heat can be transferred through the movement of fluids (liquids or gases), which are not present in a vacuum.

Let me know if you have any more questions about heat transfer!