Without this, many cycles such as the water cycle and photosynthesis would not exist. What could all these cycles not exist without?

This question appears incomplete

Explanation:

This question appears incomplete. However, one similar substance that, if missing, many cycles (particularly the two cycles/processes provided in the question) will not exist/proceed is the sun/sunlight.

In the water cycle for instance, if there is no sun/sunlight, there will be no heat to allow for evaporation of water from the water-body (ocean, sea, stream or lake) hence there will be no cloud of water droplets in the atmosphere. The implication of this is that, the first process of the water cycle will not proceed, hence the cycle will not exist.

During photosynthesis, carbondioxide reacts with water in the presence of sun/sunlight to produce glucose and oxygen. The absence of sun in this reaction will not lead to the production of glucose which is the useful product of photosynthesis for plant.

From the explanation above, it can be deduced that the absence of the sun/sunlight will prevent the two cycles from existing.

that is wrong, its not thymus.