What are some reasons that more advanced civilizations might want to send out messages to other star systems?

The consumption of fossil fuels could be

This is the number of complete movements of a wave per second.

The first-order reaction a→2b+c has rate constant 0.538 s−1. if the initial concentration of a is 0.867 mol l−1, what is the half-life of the reaction in seconds? remember to use correct significant figures in your answer (round your answer to the nearest hundredth). do not include units in your response.