Mechanical Engineers use \(y\) as a coordinate axis at the ground pointing towards the sky. Dissimilar, Aerospace Engineers use \(y\) as a coordinate fixed to a flight-vehicle pointing towards the Earth. This is why Mechanical Engineers have their feet on the ground, and Aerospace Engineers have their heads above the clouds.
Wernher Von Braun once said that we have invented rockets, not to destroy our planet, but to explore the universe. Similarly, we may say that we have discovered thermonuclear energy, not to destroy our planet, but to advance mankind toward a peaceful, galactic culture. Friedwardt Winterberg