Q: Trains are numbered so even numbers go eastbound, odd numbers go west. Why? Also what happens to north/south routes? I wonder if it’s because the first train (#1) that left the depot was heading west, away from the home station. —Ray F., Albuquerque, New Mexico

[Courtesy of Amtrak] Amtrak's (West) Coast Starlight is Train 11 from Seattle to Los Angeles, Train 14 heading back north.

A: Trains are numbered much the same as railroad tracks. The idea behind the numbering is simple—so trains going in opposite directions don’t collide. Even-numbered trains travel north and east. Odd-numbered trains travel south and west. Exceptions did occur; for example, the Santa Fe Railroad numbered the opposite way.

Your guess about the #1/odd-numbered trains heading west appears correct. Sam McCall (Encyclopedia of Southeastern Railroads) examined old time tables and found that most northeastern cities, like New York City and Chicago, were the origin of trains. Their first (#1) train left from the northeast and headed west and south. Returning trains (#2) did the opposite and that’s probably how the odd/even convention started.

Model-railroader Bob Hanson figures the practice started about the time that railroads standardized rules and watches. Companies adopted "Railroad Time" at noon on November 18, 1883. However, McCall says, many roads issued timetables before then. So, numbering may predate Railroad Time.

Railroads with only one or two tracks didn’t bother to number their tracks (or trains). That included most trains outside the Boston-Washington-Chicago triangle. They called tracks and trains, the "eastbound" or "westbound".

Big railroad companies numbered their tracks with a clever system that didn’t require re-numbering when they added more tracks. (Related: figure showing the track numbering scheme.) They numbered from the inside out. Pennsylvania did it differently: numbering their tracks consecutively. In the figure, note how all eastbound tracks are grouped together and likewise the westbound tracks. A simple setup avoids confusion and possible collisions.

Sam McCall: Hosam’s college of railroad knowledge

Q: Does the chameleon have a predator? —Hayden,Victoria BC, Canada

 [Gail J. Worth © Used with permission] Male veiled chameleon

A: We know about the chameleon fantastic defenses: camouflage, turret eyes, and stillness. But what are they defending themselves from? Snakes. Especially the Boomslang and Vine Snake. Birds take a toll, too: shrikes, coucals, and hornbills. Man, though, kills most via pesticides and destruction of their natural habitats. The pesticides either kill them directly or kill enough spiders, grasshoppers, flies, mosquitoes, and beetles that they starve to death.

The predators most deadly for captive chameleons (usually kept in big cages) are cats, rats, mice, and prey birds. Even ants and blood-sucking bugs give them a hard time. Not to mention people: leave a cage door open for an instant and discover how fast an escaping chameleon can move.

Wildwatch: Chameleon

[Erik Leitch, University of Chicago] The Degree Angular Scale Interferometer (DASI) in its ground shield on top of the Martin A. Pomerantz Observatory

A: On Sep. 19, 2002 University of Chicago astrophysicists announced a momentous discovery. Using a radio telescope (the Degree Angular Scale Interferometer, DASI) at the National Science Foundation's Amundsen-Scott South Pole Station---they measured a tiny polarization of the fossil radiation that originated from almost the beginning of time, 14 billion years ago. They found that the microwave background radiation in adjacent patches of sky vibrates in slightly different directions. (Related: definitions of polarization and microwave) That may sound less momentous than it is. It means, though, that the Big Bang theory checks. The model predicts just such vibrations and . . . Bingo! We detected them.

Fossil radiation lights up the early universe.

The background radiation shows the Universe 300,000 years after it began---almost the beginning. Until then, it was a blazing hot dense soup of particles (electrons, protons, neutrons, neutrinos)---so dense that light had no free path to shine along. Each photon (bit of light) existed jammed against electrons. Sometimes a photon collided with and scattered off an electron, causing the photon's vibration to line up in one direction---a polarized light particle. But the scattering was so frequent among so many photons that light did not polarize in a net direction.

The Universe, about then, cooled enough for hydrogen atoms to form. This cleared clutter and provided a path for light. The light zoomed off, its direction and polarization recording a snapshot of the primeval particle soup---extremely valuable information as we struggle to understand how the Universe began. We are recovering this data.

"It was like a fog clearing on a humid morning," says Mark Dragovan, astrophysicist at the Jet Propulsion Laboratory. "The scattering becomes less as a fog clears, until you are left with a clear path for the light with no scattering."

The light carries only information from the last scattering, which was during the epoch of electrons combining with protons to form hydrogen. When electrons combined with atomic nuclei, the teeming crowds of electrons diminished. That left fewer free electrons to scatter photons. The particles forming the Universe were, by this time, in slightly uneven globs---with hotter and cooler spots. So, photons struck electrons more from the one direction than another and the fossil radiation received a net polarization. That's the polarization we have recently detected.

The fossil radiation cooled and stretched on its way here.

The light that started towards us 14 billion years ago was the same color as the cooler giant stars are now. But today, we can't see light visible so long ago because expanding space changed the light as it zapped here. The ballooning Universe stretched the light a thousand fold from visible light to longer-wavelength radiation: microwaves---similar to those in microwave ovens. The ancient photons still exist in vast quantities. Ordinary household TV antennas pick up the Cosmic Radiation Background signal. (It’s 1 % of the total static noise).

That's the radiation that the radio telescope, DASI, received at the South Pole, in 2002. By examining its polarization, scientists can determine---not just how lumpy the early Universe was---but how its particles moved. That's a powerful handle on how the Universe formed and how it's evolving.

"Detection of the polarization opens a new door to exploring the earliest moments and answering the deep questions before us," says University of Chicago astrophysicist Michael Turner. Like, what's dark energy; how big are gravity waves. . .

The Antarctic sun: Discovery supports paradoxical views

The University of Chicago: DASI

(Answered Feb. 7, 2003)