Yearly Archives: 2010

Q: Why is the number 1 not considered a prime number?

Mathematician: Note that when we say that a number is “prime”, all that we are doing is applying a definition that was devised by mathematicians. A prime number is generally defined to be any positive number that has exactly two … Continue reading

Posted in -- By the Mathematician, Math, Number Theory | 41 Comments

Q: If the universe is expanding and all the galaxies are moving away from one another, how is it possible for galaxies to collide?

Physicist: Because the universe isn’t expanding fast enough.  On average all the galaxies are moving apart, but often a given pair will be moving together. Hubble observed that the farther things are away, the faster they’re receding.  Specifically, in the … Continue reading

Posted in -- By the Physicist, Astronomy | 6 Comments

Q: What happens when you fall into a blackhole?

Physicist: Terrible, terrible things. The first thing you’ll be likely to notice as you approach the hole is the tidal forces.  Tidal forces are nothing more than the difference in gravitational force between the near and far side of an … Continue reading

Posted in -- By the Physicist, Astronomy, Physics | 89 Comments

Q: Is the total complexity of the universe growing, shrinking or staying the same?

The complete question was: If you were to look at the universe as an organism, was the early universe a simpler organism than the present-day organism?  Is the total complexity of the universe growing, shrinking or staying the same?  And … Continue reading

Posted in -- By the Physicist, Biology, Entropy/Information | 9 Comments

Q: If two trains move towards each other at certain velocities, and a fly flies between them at a certain constant speed, how much distance will the fly cover before they crash?

The brain teaser comes in a many variations. For example: Trains A and B, 700 miles apart, are heading toward each other on a straight piece of track. Train A is going 85 mph while train B is going 55 … Continue reading

Posted in -- By the Mathematician, Brain Teaser, Math | 13 Comments

Q: Why does oxygen necessarily indicate the presence of life?

Physicist: Short answer: Life is the only thing that makes lots of oxygen. This question comes in the context of a conversation about the Kepler mission.  So far (as of January 11, 2010) 424 “exoplanets” have been discovered and confirmed … Continue reading

Posted in -- By the Physicist, Astronomy, Biology, Physics | 3 Comments