Why do scientists believe the universe is still expanding?

Scientists believe the universe is still expanding primarily due to observations of distant galaxies, which are moving away from us, a phenomenon known as redshift. This observation supports the Big Bang theory, indicating that the universe has been expanding since its inception. Additionally, the discovery of dark energy, a mysterious force driving the acceleration of this expansion, further reinforces the idea that the universe continues to grow. Measurements of cosmic microwave background radiation also provide evidence of the universe's expanding nature over time.