The Andromeda Paradox and other Oddities of Relativity

Curious about Special Relativity, but afraid it will mess with your head? You might be surprised at what you can learn. This course is designed with the non-physicist in mind. Using only high school algebra, we'll discover how the two principles behind Special Relativity lead to three paradoxes.

• The Andromeda Paradox

• The Twin Paradox

• The Ladder (or Barn Pole) Paradox

We'll then see how these same principles resolve the very paradoxes they give rise to.

By the end of the course, you will be able to describe the principles of relativity and each of the 3 paradoxes. You'll be able to show how these principles affect the flow of time and the measurement of space. Finally, you will understand and use some of the mathematics of special relativity.

Overview:

The Andromeda Paradox challenges our common notions about what the present is. Bob and Alice meet in a park on earth. Meanwhile, the Earth is in danger of an invasion from the  Andromeda Galaxy. For Alice, the warrior ships have already left. For Bob, invasion plans are still on the table in Andromedan Parliament. Who has the correct notion of now? Alice? Bob? Both? Neither?

The Twin Paradox demonstrates an apparent contradiction in how time passes. Alice and Bob are twins. Alice takes off from earth and travels through space. Because of her motion, Bob observes time moving more slowly for Alice. When Alice returns home, Bob expects his twin to be younger than he is. However, from Alice's point of view, it is Bob who is moving. It's also Bob's clock that is running slow. She expects Bob to be younger than she is when she gets back home. Is time broken?

The Ladder (or Barn Pole) Paradox relies on length contraction. When Bob (who can move very quickly) runs with a ladder into a barn, Alice sees the ladder as being just short enough to fit into the barn. But Bob sees the barn moving. For him, the barn has shortened and is too small for the ladder. Can Bob fit the ladder into the barn or not?