Comments

1. #1 Michael Fisher

   http://en.gravatar.com/michaeljfisher

   February 2, 2014

   Lovely thing. I wonder if pedestrians & pushchairs work well with unsegregated pedal power there? I assume the Dutch cyclist is more polite than Brit cyclists who use pavements even when safe cycle paths are available.

2. #2 anonymous satanist

   February 2, 2014

   Seeing that it’s Netherlands, it’s more a case of “unimpeded flow of cyclists and pedestrians without being inconvenienced by cars and trucks.” But anyway, yay bikes!

3. #3 G

   February 2, 2014

   How’bout: “How did the bicycle cross the San Francisco Bay Bridge?”

   I tried that once. Took my bike on BART (regional light rail) into San Francisco one day, and on trying to get back, discovered that (in those days) bikes weren’t allowed on BART during commuter hours: which meant a few hours of waiting. “Hell with this!” I thought, and pedaled onto the Bay Bridge at the Bryant Street onramp.

   It wasn’t long before, while pedaling hard, scared of all the cars whizzing by at highway speeds, I heard the “whoop whoop!” of a police siren. Uh-oh. I pulled off at Treasure Island and sheepishly handed over my license (from the state where I’d lived before moving to California a few weeks prior to this adventure) to a California Highway Patrol officer.

   He explained that riding on the bridge was a big no-no, but instead of spending the night in jail I’d only be getting a ticket and a ride to the other side.

   He also pointed out all the places where traffic merging from the right lanes would likely have gotten me killed. Looking at those lane merges from the perspective of “what if I was on my bicycle at that point?”, was an interesting exercise.

   So that’s how the bicycle crossed the San Francisco Bay Bridge: in the trunk of a CHP cruiser, with me sitting in the back seat, embarrassed but safe.

   I paid the ticket and never did _that_ again.

   Here’s to the day when we have a legal & safe bike lane all the way across.

4. #4 Michael Kelsey

   SLAC National Accelerator Laboratory

   February 2, 2014

   @G #1: Good story! Unlike a few other states I’ve had the (mis)fortune to drive in, I have nothing but respect for the Highway Patrol. They don’t do “speed traps” (they *do* run radar along stretches where we always go way too fast), and they do go out of their way to help motorists and others with problems.

   I’ve gotten several (quite justified) speeding tickets from them over the years, and I’ve also had them do things like run a lights-only escort for me all the way from where I hit the median into the nearest Ford dealership to get my car fixed. In the media trope of “good cop/bad cop”, the CHP are usually the good cops.

5. #5 Robert

   February 3, 2014

   The key word here is actually “suspended” as its certainly not the first traffic circle for bicycles. The Netherlands has been building infrastructure for bicyclists for the last century (I once heard we started during WWI when the rest of Europe was busy digging trenches), and I’ve seen several traffic circles for bicyclists which were realised by tunnels under the roads. Where I live there is one traffic circle for cars with a crossroads for bicycles a couple meters below it, a bit like the above picture but with the roles of cars and bikes reversed. That one has existed as long as I can remember (i.e. over 30 years.)

6. #6 eric

   February 6, 2014

   Hi Ethan,
   I will apologize ahead of time for doing an off-topic invasion, but I saw your ‘answers to 22 creationists’ post at Medium, really wanted to reply to it, and have no twitter account.

   First, I think answering those questions seriously and honestly was a great idea. I hope folks read it (plug plug), because I think that’s the right approach to take towards many creationists – treat them as honest questions, and respond with explanations rather than derision.

   But I wil slightly quibble with your 2LOT answer. You say: “…has the entropy of our Universe, from the moment we could first describe it with the Big Bang Theory, ever had a moment where its total entropy decreased? The answer is no. The entropy is always increasing.”
   There are actually two cases where it could “not increase” for a time, both more on the theoretical side but not out of the question for our past universe. The first occurs with inflation: if inflation is so fast that the space between any two objects (photons, particles) is spreading out faster than c, then nothing in the universe can interact and so entropy cannot increase for the duration of that inflationary period. Of course, during this time period one could also just say that our “universe” wasn’t one connected universe, it was many closed systems which ‘opened’ later when inflation slowed down. So it’s not so much a violation of the LOTs as it is a wierd case where you take one big closed system and suddenly, temporarily convert it into many smaller closed systems.
   The second “no increase” period would occur in the more conventional big bang period, with cooling, and is more of a bookkeeping/definitional trick than any real phenomena. Entropy is a measure of the distribution of energy amongst available microstates. The more even the distribution, the higher the entropy. It’s possible to take a high entropy system and suddenly make it lower entropy without doing anything to it, if the universe in which the system resides suddenly gains a large number of available but “empty” microstates. One can imagine this exact thing happening as our universe cools. First the temperature cools enough to make subatomic particles stable, and suddenly all their rotational, vibration, exicational etc. states are available…but empty. Later as electron-nucleus bonding becomes stable, all the electron shells become viables states in which to store energy..but they start off empty. Then even later, when the background drops below eV and molecular bonding becomes stable, you again have a massive increase in number of energy storage states…which start off empty. Now in reality, these transitions were smooth. We didn’t suddenly go from no-protons to lots of protons, the amount of protons in existence at any point in time increased incrementally as the rate of destruction of protons decreased with temperature. But nevertheless, this is a theoretical way to decrease entropy. You can even make a simple classroom exercise out of it. Give your students energy state labels like “rotational.” Give one of them a bunch of chits representing units of energy. Tell them that every time they bump into someone, they have to even out the chits between the two. As they bump, more energy distribution between microstates becomes more even – entropy increases. Now ask them what happens to the calculated entropy of the room if you suddenly add more students. Suddenly, the distribution of energy amongst states became a lot less even, didn’t it! 🙂

7. #7 Ethan

   February 6, 2014

   Hi Eric,

   Thanks for the plug, and for reading and liking it!

   I will point out that the period of the Universe during which it undergoes inflation, as I’ve explained many many many times, is by definition before the Universe could be accurately described by the Big Bang. The Big Bang is predicated on a hot, dense, matter-and-radiation filled state describing the Universe, which is not the case until inflation ends. During that inflationary period of time, entropy is understood to have remained constant, which is still not a decrease.

   The Universe did not have to cool adiabatically as it expanded; it could have (in theory) cooled isothermally or any other different way. However, think — back to chemistry — about the things one can hold constant when making changes to a system. You can change a system isobarically, where the pressure remains constant, isovolumetrically, where the volume remains constant, isothermally, where the temperature remains constant, or adiabatically (which is how the Universe expands), which is sometimes called isentropically, because the entropy remains constant!

   But the process you describe is one that I don’t see how the entropy is decreasing, and I’m trying hard to conceptualize it. Sorry.

8. #8 eric

   February 6, 2014

   No problem. Agree with you on the order of inflation/big bang; which is why I put the inflation-based example first.

   To see how entropy is decreasing, consider an analogous property: cashtropy. Cashtropy is low when one or a few people have all the cash. It’s high when everyone has the same amount of cash (energy is distributed across microstates). To make the analogy work, we say that when two people meet, they exchange cash in some way that evens out the distribution.

   So, you start off with a system where there is only a few people, and one person has all the cash. It gets quickly redistributed, and cashtropy rises. Now suddenly you bring a bunch of people into the room who have no cash. Cashtropy has just decreased (!!!), because it is less evenly distributed. In principle, as the universe cools, that is what has happened at a few points: more microstates have become available. In the instant when they are available but have not yet been used, entropy has actually decreased.

   A more realistic example may be a living room filled with gas. We all know it would be highly improbable that all the gas suddenly moved to one side of the room. What if the universe suddenly and spontaneously added a dining room? In the instant of adding a room, the system went from “even distribution” to “every atom is on one side of the living room/dining room combo.”

   There is really no difference between “high” and “low” cashtropy at this point.

9. #9 eric

   February 6, 2014

   ack, last line was a cut and paste error. Ignore.

10. #10 Oded

    February 8, 2014

    Regarding the music on Medium:

    “Spotify hasn’t launched in your country yet”

    🙁

    Luckily, you made the song available here as well, so I can still enjoy it

11. #11 Ethan

    February 8, 2014

    Is that in Israel, Oded?

    That’s a shame (but good to know); I want to make what I post (or intend to post) accessible to everyone across the world.

12. #12 Brandon Pryor

    West Virginia, United States

    February 12, 2014

    I found this to be very interesting from a physics stand point. The amount of mass that this structure has and it being suspended by a pole with cables hanging off is very interesting. It is a very good idea that not only made traffic better but also is safer for cyclists. This is interesting from the stand point of how this man had this idea. The tension on these cables is probable amazing. I would hate to see what would happen if an earthquake came through and put to much tension on those cables and if one broke.