Monthly Archives: January 2013

Q: What is quantum teleportation? Why can’t we use it to communicate faster than light?

Physicist: Contrary to its exciting name, quantum teleportation doesn’t involve any physical stuff suddenly disappearing and then reappearing somewhere else.  Instead it’s a cute, clever, technique for transferring an unknown quantum state of one system (usually a single particle) to … Continue reading

Posted in -- By the Physicist, Entropy/Information, Physics, Quantum Theory | 25 Comments

Q: Since all particles display wave-like characteristics, does that imply that one could use destructive wave interference to destroy or at least drastically change a particle?

Physicist: The wave-like property of particles allows you to do a lot of cute things with particles that would otherwise seem impossible, but making a particle disappear isn’t one of them.  You can use destructive interference to make it very … Continue reading

Posted in -- By the Physicist, Particle Physics, Physics, Quantum Theory | 4 Comments

Q: How does the Oberth Effect work, and where does the extra energy come from? Why is it better for a rocket to fire at the lowest point in its orbit?

Physicist: When a rocket fires it increases its speed by some fixed amount called the “ΔV” (delta V).  If the original speed is W, and the rocket speeds up by ΔV, then the change in energy is: .  So here’s … Continue reading

Posted in -- By the Physicist, Physics | 16 Comments

Q: How do lenses that concentrate light not violate the second law of thermodynamics? If you use a magnifying glass to burn ants, aren’t you making a point hotter than the ambient temperature without losing energy?

Physicist: This is a surprisingly subtle question. It certainly impossible to create new energy, but there’s nothing to stop you from piping energy from one place to another (say, by running hot water from a boiler to somewhere else).  The … Continue reading

Posted in -- By the Physicist, Entropy/Information, Physics | 48 Comments

Q: What makes natural logarithms natural? What’s so special about the number e?

Physicist: “e” shows up on its own a lot, and the frequent appearance of the natural log, ““, follows from that.  Almost all of the uses and importance of e and ln are from results in calculus, but those results … Continue reading

Posted in -- By the Physicist, Math | 7 Comments

Q: If the world were to stop spinning, would the people and everything on it be considered ‘lighter’ or ‘heavier’? Would any change take place? And does centrifugal force have an effect on gravity?

Physicist: Centrifugal force* due to the spinning of the Earth is certainly a measurable effect, but it’s a small effect.  While the spinning of the Earth doesn’t directly affect gravity, it does off-set it a little.  At the north and … Continue reading

Posted in -- By the Physicist, Physics | 59 Comments