# Necessary ingredients for fusion, part 2.

Dear friends,

Let's talk a bit more about fusion energy.

We have so far mentioned that, for fusion, we need to join together two light nuclei and that, because the nuclei repel, we need very **high temperatures**.

Another necessary ingredient for efficient fusion is “high enough” density. We can intuitively understand that the more densely packed our light nuclei are, when we heat them to very high temperatures, the more likely they are to bump into each other. Conversely, if the nuclei are very sparsely packed, the chances of one hitting another in any given time interval are small. If we want to have an appreciable amount of fusion reactions happening, we therefore need to have a “high enough” density.

In practice, this density is actually quite low compared to the densities we are used to – about 100 000 times less than the particle density of the atmosphere (at sea level). Fusion experiments around the world routinely reach the necessary densities for a measurable number of fusion reactions to occur.

We have seen, therefore, two *necessary ingredients* for efficient fusion, **temperature **and** density**, and that these are routinely part of fusion experiments around the world. There is one more ingredient that is absolutely necessary for efficient fusion which is, however, not met. More on that in our next post!

In the meantime, please continue spreading the word about Fusion Reactors.