Gravitational Lensing

• Gravitational lensing is the bending of light by gravity, resulting in a similar effect as a lens.
• My goal was to understand more about the different types of lensing and to create a fun way to visualize it.

Course Connection and Personal Interest

• Black holes (which are one object that result in gravitational lensing) are stellar objects that we cover in class. We also cover gravitational wells, which is the reason for lensing, so this topic has a strong connection to the course.
• I have personally always been interested in general relativity, but the concepts are hard to grasp and believe. But gravitational lensing shows these concepts in action, and seeing visual evidence of spactime bending is incredible to me.

Significance

• One of the first major confirmations of general relativity (in 1919).
• Can be used to detect dark matter.
• Helps in determining mass of galaxies and clusters.
• Magnifies distant objects, allowing us to study very distant or faint objects.

How Does Gravitational Lensing Work?

• In empty space, a thrown ball keeps moving straight at a constant speed.

• On Earth, the same ball curves downward because gravity changes its path.

• Newton’s gravity explains this using forces between masses.
• But Newton’s law can’t explain how light bends (light has no mass).
• Einstein’s relativity gives a new idea: mass and energy curve spacetime.
• Objects move along the straightest possible path in curved spacetime.
• A ball still “goes straight,” but the space it moves through is curved.
• Light follows these straightest paths too, so its path bends near mass.

• This bending acts like a lens, hence the name gravitational lensing.

Types of Gravitational Lensing

• Strong lensing: arcs, rings, multiple images.
• Weak lensing: small shape distortions used to map dark matter.
• Microlensing: temporary brightening when objects align.