Questions:
1. When a smooth circular object is placed in the path of light, its shadow behind will be dark except for a small bright spot at the centre. What is the spot called? Its discovery in 1818 was a strong indicator that light behaves like a wave.
2. Backed by discoveries like those in Q1, pointing to the possibility that light can behave like a wave, scientists assumed space should be filled with a medium the wave can pass through. Name the famous 1887 experiment that looked for this medium but ended up disproving its existence.
3. The answers to Q1 and Q2 plus other events disrupted what scientists believed they knew of light and space. In 1898, a French mathematician first combined space and time into spacetime and advanced some principles that explained the discrepancy in Q2. Name him.
4. The spacetime of our universe has four dimensions – three of space and one of time. What is the name for a point on this spacetime?
5. Mathematically, spacetime is a ________. This means a very small portion of spacetime will appear flat when zoomed in but can be part of a curved surface when zoomed out – like how the earth appears flat to someone standing on the ground but whose spheroidal shape becomes apparent when standing on a mountain. Fill in the blank.
Visual:
Name this Indian physicist who provided the first, if also incomplete, proof that the general theory of relativity allowed spacetime to become infinitely curved in some places.
Answers:
1. Arago spot
2. Michelson-Morley experiment
3. Henri Poincaré
4. Event
5. Manifold
Visual: A.K. Raychaudhuri
