Monday, February 25, 2013

Stuck in Traffic? Pass the Time with Physics

When I find myself stuck in traffic, my mind first turns to the shortcomings of public transit for my typical commute - a part of me wishes I still lived downtown.  The next place my mind often wanders to is physics; a surprising number of seemingly abstract scenarios actually describe the motion (or lack thereof) of one's car in a system of interconnected streets.

One such analogy is that of a system of interconnected springs and masses:

Imagine that you are the sixth car waiting, single file, at a red light.  The moment that the light turns green, the first car begins to accelerate, but you do not move.  Each car must wait for the car in front of them to displace in order to proceed forward.  It is the same for the system of masses.

If a force is imparted on the first mass, there will be a time delay before the effect of this force is felt by the tenth mass.  We can think of the springs like spaces between cars, and the masses as the cars themselves.  This analogy is far from perfect.  For one thing, cars are more independent than this model would suggest.  Car 1 is unaffected by all those behind it, whereas the motion of mass 1 is greatly affected by the motion of those behind it.

Thursday, February 21, 2013

I Predict a Space Elevator on Earth in my Lifetime

Most of my readers are aware of my research on and affinity for the space elevator project.  A whole page on this site is devoted to it.  Still, I try not to overload my blog with S.E. related content; is the place for S.E. devotees to stay up to date with the goings on, while is where one goes to get involved in the actual project.

Still, I could not help but give a brief response to George Dvorsky's article that was posted last week on the io9 blog entitled "Why we'll probably never build a space elevator."  In it, Dvorsky lists five problems, which is a strange choice of word to describe what engineers call challenges. While the challenges he discusses are mostly relevant and the discussion mostly accurate, the conclusions he draws from them are odd - it seems as though he arrives at them in order to satisfy the title of the article.

For example, the number one 'problem' with a space elevator is, as the author correctly states, producing a material with a sufficient strength to density ratio with which to construct the tether. Though his numbers on this are not entirely correct, it is true that material science is far from producing a substance rendering S.E. construction feasible.  However, the argument that the project is a dud because construction cannot begin today is absurd.  Over the past one hundred years, the field of material science has taken many leaps, each paving the way to new technologies.  The space elevator is not the first technology that needed to patiently await a strong enough and light enough material, and it will not be the last.

Furthermore, I take issue, personally, with his 'problem #3', about climber excitation, which happens to be one area I have researched extensively.  My research found the extent to which a climber excites the tether (it is proportional to lifted mass, distance climbed, and climber speed), and proposed some reasonable methods to mitigate such effects.  With respect to all of the big challenges associated with the space elevator, this one has been shown to be minor.

Friday, February 15, 2013

"Sir? Can I Just Hover and Let the Earth Turn Towards me?"

There is a prevalent misconception among introductory physics students (not to mention the general public) about flight within our atmosphere.  Admittedly, as a science student long ago, I wondered if I could travel half way around the world along a given latitude in 12 hours simply by hovering in place, say, in a helicopter.  After all, the Earth spins about the axis that extends from its geometric north to south pole once every 24 hours.  I was stunned that it could take more than 12 hours to fly somewhere on the same latitude by airplane.  Were the pilots dummies?  Just sit there and let your destination come to you!

Before addressing this misconception directly, let us investigate just how fast the ground on which you are currently stationed moves with respect to the rotational axis of the Earth.  Using simple kinematics, we can find this relative velocity at the equator, making use of the fact that the radius of the planet is 6,378 km.  The planet rotates through one circumference (40,074 km) in 24 hours, so the relative speed of the surface along the equator is (40,074 / 24 km/h) about 1,670 km/h, or, about twice as fast as a typical commercial airplane cruises.

But, most of us do not live directly along the equator.  We are some angular displacement (latitude) away from it.  If you want to determine the particular surface speed where you reside, multiply 1,670 km/h by the cosine of your particular latitude.  If you are standing in New York City, which is at a latitude of 40.7 degrees, then the land beneath you moves at 1,266 km/h (352 m/s) relative to the spin axis, in a direction perpendicular to it (Eastward).

Can you sense these high speeds?  No.  Organisms can only discern accelerations internally.  If the spin rate of the Earth were to change suddenly, all buildings would fall, oceans would displace, and it would be a really bad day for anyone not living on either geometric pole of the planet.  But, fret not, such an occurrence is extremely unlikely (for an analysis about the amount of energy required to cause the Earth to experience a large angular acceleration, here is a link to a different article).

Tuesday, February 5, 2013

George Carlin, Comedian and Linguist

If I ever find myself uninspired and in need of some kind of pick-me-up, taking in five minutes of George Carlin (1937 - 2008) usually does the trick.  Like many YouTube adventures, what was supposed to be five minutes often becomes twenty or more, but Carlin is great in whatever dose.  He is easily my favourite comedian, and I wish I could have seen him live. 

Part of his allure was that his routines tended to revolve around contraversial topics.  His goal was to disturb the audience from their comfort zone, usually, though not always, stopping just short of being terribly offensive.  Then, once drawn into the subject, he tried to bring members of the audience to his side of the argument (though most members of his audience tended to agree with his views already).

When I think of his act, I usually think of his amazing facial expressions and his brutal honesty.  But if there is one feature that sets him apart from other comedians, it is his mastery of the english language.  It is surprising just how much of his material involves a curiosity with words and expressions.  It was his fascination with 'dirty words' that gave his stand-up career a major boost in the seventies (see Seven Dirty Words circa 1972).  Now is probably a good time to mention that the links in this article contain foul language, which I try to refrain from in the articles on this site.