The conversation between human and AI assistant.
Why don't all stars and galaxies gravitationally lens the light from all the stars and galaxies behind them?
Is there a way to measure the strength of gravitational lensing effects?
Yes, astronomers can measure the strength of lensing by observing how an object's image is distorted by the gravity of a massive object in its foreground. By analyzing the shape and position of the distorted image, they can estimate the mass and distance of the object causing the lensing effect.