The statement that scientists say the universe will end in 5 billion years is not accurate. While scientific theories and models can make predictions about the future evolution of the universe, the exact fate of the universe is still an active area of research and remains uncertain.
As for the observation of galaxies that are 12 billion light-years away, it is important to understand that the light from those galaxies has taken billions of years to reach us. When we observe distant objects in space, we are effectively looking back in time because we see them as they were when the light was emitted.
The current age of the universe is estimated to be around 13.8 billion years. So, when we observe galaxies that are 12 billion light-years away, we are seeing them as they were about 12 billion years ago. This does not mean that the universe has already ended, but rather that we are observing objects from an earlier time in the universe's history.
The future fate of the universe depends on various factors, such as the expansion rate, the amount and distribution of matter and energy, and the nature of dark energy. Scientists propose different possibilities for the future of the universe, including scenarios like continued expansion, a Big Freeze, a Big Crunch, or even a Big Rip. However, the precise outcome is still a topic of active investigation and debate among researchers.