Thursday, April 24, 2014

The Famous Twin Paradox

Maybe you have heard about the fantastic story of twin brothers who part ways on their twentieth birthday.  Let's call them Billy and Timmy.  Billy stays on Earth, while Timmy travels at 99.9% the speed of light on his fancy space ship.  Timmy returns to Earth on Billy's fortieth birthday after having explored the universe.  Timmy is visibly younger than Billy.  In fact, he has only been travelling for 326 days as far as he is concerned.  He is yet to turn 21 - he is not legal to consume alcohol in the United States though his ID says he is middle-aged.

Why the time discrepancy?  It has everything to do with speed.  Special relativity, as theorized by Einstein in 1905 and confirmed countless times by modern experiments, says that the faster we move, the slower time passes for us.  This is not science fiction; this is science.

The time ratio, also known as the Lorenz factor, which gives a ratio of the passage of time between stationary and moving observers, is given as follows...


Thursday, April 3, 2014

"Daddy, Who Put the Whole World Here?"

My daughter and I had a brief discussion this morning, on the way to daycare, about the origins of the universe.  I can't imagine that I asked such deep questions as a four-year-old.

It was a true relief for me when she asked where the world came from, because before that, her deep questions were all about death.  While neither the birth of the universe or the death of living things is easy territory to navigate with a Pre-K child, I am far more comfortable discussing the former.

In answer to her question, I first described the idea of a Big Bang, a critical event where the entire universe is restricted to a tiny point at one instant, and then blowing up at the next.  Eventually, atoms form (we have talked about those before), and come together to make stars and planets.  I could not get into the forces that govern these processes - maybe when she's in elementary school.

At some point in my description, I paused to point out that there are parts of this that are still a big mystery.  I was worried that this might disturb her, but she seemed fascinated and unbothered that mommy and daddy don't know absolutely everything.  I explained that we don't know where the matter from the Big Bang came from, or what caused it to bang when it did.