Wednesday, 14 August 2013

No through road

This is an interesting take on graffiti on road signs.  I've posted some Parisian road sign graffiti before, but this is a new one on me.  No through road for mythical characters here!

No through road for mythical saviours, Jesus, crucified, graffiti, Paris
No through road for mythical saviours
Its interesting though.  When I see people wearing a cross around their necks I usually find myself wanting to ask what the T stands for.

Now I know!

Tuesday, 13 August 2013

More Parisian Graffiti

I have often featured interesting graffiti on Something Surprising.  Near the Pompidou Centre in Paris is this amazing face painted on a wall.  Is it graffiti or, given its location, art?

Graffiti or art - near the Pompidou Centre in Paris
Graffiti or art - near the Pompidou Centre in Paris

My feeling is that it is too good to be considered as modern art of the type favoured for modern art galleries.

I'll settle for calling it good graffiti.

Monday, 12 August 2013

Physics on the Metro

Have you ever spotted how the air moves on metro trains?

On ordinary trains with short carriages there is often a flow of air through the carriage as the train moves along.  It brings blessed relief on those hot summer days!

But something different happens on those trains that are open from one end to the other, and the effect depends strongly on the number of people on the train.

One of those long un-divided trains on Paris metro line 1
One of those long un-divided trains on Paris metro line 1

If the train is fairly empty, you get a strong rush of air from the front to the back as it accelerates.  Quite often the train accelerates in steps, and you get repeated breezes of different strengths, correlating well with the driver's actions.  Then as the train slows down, the air rushes to the front of the train.

This shows that the mass of air inside the train has to be pushed to get it to speed up and slow down.  The push comes from a pressure gradient which is set up as the train changes velocity.  That gradient is established by filling one end of the train with more air, increasing the local pressure.

I had spotted this happening on a journey on an empty train.  The following day on the same metro line I was expecting to observe the same effect.   However, it happened to a much less noticeable extent.  What was different?  The train was full of people standing.  That meant that the air flow was significantly better damped.

The effect is also much clearer if you sit near the middle of the train than it is at the ends - obviously.  After a week of observations I think this is good(ish) physics.

On the other hand . . . on another journey I watched a roller skater walking down stairs (very carefully) and then rolling along the platform.  As he slowed himself down he spread his feet wide apart, lowering his centre of gravity.  To stop himself he brought them sharply back together, lifting his whole body a few centimetres.  It appeared to me at first sight that he had converted his kinetic energy into potential energy in doing this - but on reflection that is not consistent with conservation of momentum.  This wasn't good physics after all.

Perhaps it was just a flourish in his performance after all.

Isn't physics fun?  It gets everywhere!

Sunday, 11 August 2013

Hale and Hearty

Enjoying a visit to Paris, I like to spot words in French that have obviously migrated into English.

Eiffel Tower - just before it was evacuated on August 9th, 2013

This week's word is 'hâlé' (pronounced ah-lay in French), meaning bronzed or sunburnt.  I have no idea how to say the word in such a way as to distinguish it from the more common verb 'aller' meaning 'to go'.  I assume that context is king.

Surely is is the origin of the English word 'hale'.

Saturday, 10 August 2013

Liberty - for the week

I'm away, enjoying a week of holiday.  Guess where I am.

Liberty, equality and fraternity in Paris
Liberty, equality and fraternity

It looks as though I might be in New York, but instead I find myself in Paris again, seeing some of the sites that I have never seen before, and visiting others, like this one, that I have seen from the train many times.

This is a 9m tall replica of the Statue of Liberty, and it can be found on the Isle des Cygnes in the middle of the River Seine.

Replica Statue of Liberty in Paris, on the Isle des Cygnes
Replica Statue of Liberty in Paris, on the Isle des Cygnes
Having walked the length of Isle des Cygnes I didn't see a single swan.

Did you know that is where we get the English word 'cygnet'?