# A Brief Physics Lesson: Bicycle Edition

Math? Physics? Those who enjoy brief exercises in applied speculation will certainly learn a thing or two from Rhett Allain, who took some time to consider bicycles and hills. At first blush, it seems an easy enough question: What’s the steepest gradient you could possibly ride on a road bike?

Of course, there is a difference between the simplicity of straightforward mathematics and the complexity of accounting for all the factors required.

I think there are three reasons why a slope would be too steep. For all of these cases, I am going to assume that it is a prolonged slope. This means that you can’t just build up a large speed and zoom up the slope. If this was the case, you could go straight up a wall (which you can for a short time).

Those three reasons are the limitations of human power, center of mass, and friction. If one wishes to point out, “What if you used these tires instead of those?” or, “What if you had a different gear set?” it’s all well and fine to do so, but therein lies the point about the complexity of accounting for all the factors required.

Really, the friction problem might be worse than this. The bike only uses the back wheel for moving forward, so it is the friction on the back wheel that matters. If the biker is leaning forward, the weight distribution might not be even on the two wheels. I will leave this estimation (combining the previous two limits) as an exercise for the reader.

And, of course, one is welcome to pursue such endeavors. (In truth, that might be part of the point.)

File under Whoops: I somehow managed to kill my Linkadelica template. No worries, I guess. I still haven’t figured out exactly what to do with it.

Space Invaders! Or, a note on gravitational lensing.

Helicoprion! Or, the mysterious, spiral-toothed, squid-eating fish of antiquity.

Zen Pencils! Or, an ode to Chris Hadfield.

Dolighan! Or, as long as we’re speaking of Cmdr. Hadfield.

Thunder! Or, what Cmdr. Hadfield sees.

Physics! Or, Rhett Allain uses Neil deGrasse Tyson complaining about The Daily Show logo to teach us some science.

Heat! Fascinating and philosophical. Yes, really.

The upside of being lazy is that you’re not doing anything unpleasant. The downside is that the unpleasantness stacks up at the far end. No, wait, that’s not right. But, you know, sometimes the art of playing catch-up … er … right. Enough about me.

There is plenty going on around the solar system.

First up, Yellowknife Bay, Mars, where our friendly neighborhood robotic space laboratory is still recovering from a memory glitch that forced Curiosity to switch over to its redundant B-side computer:

NASA’s Mars rover Curiosity continues to move forward with assessment and recovery from a memory glitch that affected the rover’s A-side computer. Curiosity has two computers that are redundant of one another. The rover is currently operating using the B-side computer, which is operating as expected.

Over the weekend, Curiosity’s mission operations team continued testing and assessing the A-side computer’s memory.

“These tests have provided us with a great deal of information about the rover’s A-side memory,” said Jim Erickson, deputy project manager for the Mars Science Laboratory/Curiosity mission at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We have been able to store new data in many of the memory locations previously affected and believe more runs will demonstrate more memory is available.”

Two software patches, targeting onboard memory allocation and vehicle safing procedures, are likely to be uplinked later this week. After the software patches are installed, the mission team will reassess when to resume full mission operations.

Meanwhile, somewhere near Saturn, faithful Cassini continues to dazzle as the data returns from the fourth and final Rhea flyby of the Solstice mission:

Cassini flew by Rhea at an altitude of 620 miles (997 kilometers) on March 9, 2013. This flyby was designed primarily for the radio science sub-system to measure Rhea’s gravity field. During closest approach and while the radio science sub-system was measuring the icy satellite’s gravity field, the imaging team rode along and captured 12 images of Rhea’s rough and icy surface. Outbound from Rhea, Cassini’s cameras captured a set of global images from a distance of about 167,000 miles (269,000 kilometers).

Data from Cassini’s cosmic dust analyzer were also collected to try to detect any dusty debris flying off the surface from tiny meteoroid bombardments. These data will help scientists understand the rate at which “foreign” objects are raining into the Saturn system.

Cassini will visit Titan (T-90) at a range of 870 miles (1,400 km) on April 5, 2013.

In more earthly realms, Matt McGrath continues his coverage for BBC of the CITES meeting in Bangkok, Thailand:

Three types of critically endangered but commercially valuable shark have been given added protection at the Cites meeting in Bangkok.

The body, which regulates trade in flora and fauna, voted by a two-thirds majority to upgrade the sharks’ status ….

…. The decisions can still be overturned by a vote on the final day of this meeting later this week.

The oceanic whitetip, three varieties of hammerheads and the porbeagle are all said to be seriously threatened by overfishing.

And maybe a bonus Cassini note, because I so adore the photo:

The ghostly spokes in Saturn’s B ring continue to put on a show for the Cassini spacecraft cameras in this recent image. The spokes, believed to be a seasonal phenomenon, are expected to disappear as Saturn nears its northern hemisphere summer. Scientists continue to monitor the spokes to better understand their origin and evolution.

The small moon Atlas also appears here barely visible in between the A ring and the F ring, which is the thin ring located furthest from Saturn, as the fainter dot close to the A ring. Atlas is closer to the bottom of the image. A bright star also appears in the gap between the two rings, and there are six other stars visible (one through the C ring, near the planet).

# Rhea (R-4) Flyby

It seems a long way to go for a simple answer, but the Cassini R-4 Rhea Flyby slated for Saturday morning (shortly after ten, Pacific Time) is just one of the many simple answers sought by scientists studying the Saturnian system. And that simplicity, in a way, is a striking reminder of what humanity can achieve.

This gravity flyby is designed to understand the internal structure of Saturn’s second largest moon. Is Rhea a homogeneous body or did it differentiate into a core, mantle, and crust like the Earth? The radio science subsystem will use radio waves beamed to Earth to perform precise measurements designed to answer this question.

The good news is that people are talking.

Unfortunately, that’s it.

The bad news is that the discussion needs to take place at all. BBC’s Matt McGrath explains:

New plans to protect elephants, rhinos and other species will be discussed at a critical meeting that begins in Bangkok on Sunday.

Delegates will review the convention on the international trade in endangered species (CITES).

Around 35,000 animals and plants are at present protected by the treaty.

But with a global “extinction crisis” facing many species, this year’s meeting is being described as the most critical in its history.

Naturally, one of the foremost controversies is the idea of secret ballots versus transparancy. “CITES ought to be a transparent body,” said Mark Jones of Humane Society International, “but secret ballots have become easier to implement at the behest of certain parties who don’t want their vote to be known.” Sounds about right.

# Regina: A Beacon of Science, Philosophy, and Skates

I don’t know why, but Chris Hadfield’s orbital photograph of Regina, Saskatchewan, taken earlier today, absolutely fascinates me. Perhaps it’s the bit of perspective we need in order to remember just how cool the world really is, or something like that. But the scale of isolation, the darkness of the city in contrast with the snowy land around it. The neat little boundaries making rectangles; roads, it seems, though if we didn’t know the scale it might as well be counties in Iowa. But it’s Canada.

And tonight, I’m told, the Pats are in Moose Jaw, looking to make it two straight over the Warriors. Hockey makes a lot more sense in the context of Regina, Saskatchewan, nestled amid the snowy plain, viewed from orbit. You know, science, philosophy. Inspired reflections on the human condition. Junior hockey in Canada. Seems obvious.

# Dreams in Martian Red

To the one, it’s always worth a try ….

Wanted: A man and a woman in their early to mid-50s, preferably married. Must enjoy adventure, spending long periods of time together, and sharing space—as in 501 days in a 1166-cubic-foot (33-cubic-meter) capsule and habitat. Interest in the planet Mars also a prerequisite.

Warning to applicants: You will be exposed to unprecedented risks and your long-term health could be compromised. But if the effort goes ahead and succeeds as planned, you will become the first humans in history to journey into deep space and see Mars up close.

Multimillionaire Dennis Tito, the world’s first space tourist, announced today in Washington, D.C., that his newly formed nonprofit organization has taken up the challenge of sending the first humans to Mars.

“We’ve not sent humans beyond the moon in 40 years,” Tito said at a press conference. “… And I think it’s time to put an end to that lapse.”

What’s that? A trip to Mars? With people? Marc Kaufman explains, for National Geographic News, the latest buzz in the human cosmos:

The Inspiration Mars Foundation aims to launch the mission in January 2018, when Mars and Earth are at an especially close point in their 15-year cycle. The plan is to send a man and a woman in a capsule around Mars for a flyby mission similar to the one that surveyed the moon before the Apollo landings ….

…. The Mars project is extremely ambitious, but it is at least plausible because it is simple—at least in terms of rocket science.

According to a paper Tito will present this weekend at an aerospace conference in Montana, if the launch is on target, then the spaceship will need only one rocket burn to change course. With the right trajectory, it will fly to Mars, will pass within a few hundred miles of the surface, and then will be pulled around the planet and given a gravity-assisted fling back toward Earth.

Under the current flight trajectory, the capsule would spend about ten hours within 65,000 miles of Mars.