This is that a lens produces its biggest effect when it is halfway between source and observer.

ECONOMIST: Cosmology: I spy with my little gravitational lens | The

Understand that with political pressures and global concerns, decisions can be made halfway across the world that have a ripple effect in markets around the globe.

FORBES: Dealing With Short-Term Market Volatility

By deploying so many large, economical aircraft from a vast base, open around the clock and halfway between Europe and Asia, Emirates could in effect run a global hub, reducing European airports to a feeder role and impoverishing their associated flag carriers.

ECONOMIST: Aviation