Complex sentence: The solar luminosity is about 0.07 percent brighter during solar maximum than during solar minimum but observations from spacecraft in the 2000s showed that the ratio of ultraviolet to visible light is much more variable than previously thought.
Split into simpler sentences: The solar luminosity is about 0.07 percent brighter during solar maximum than during solar minimum. Observations from spacecraft in the 2000s showed that the ratio of ultraviolet to visible light is much more variable than previously thought.