We installed secondary double glazing, one consequence of which was reduction in condensation on inside panes in winter. However, in one room, condensation (or something) appears in SUMMER on the INSIDE of the double glazing ie in between the two panes. The room is more or less south facing, so gets lots of sun over the day. Can this be condensation?

On a long haul flight I wondered with the amount of people who now fly, and the amount of money airlines make, surely one that was as big as an Airbus yet as fast as a concorde would certainly dominate the market in which people want to use.

I am not only concerned with cost as I am sure they would make the money back, but is it possible to make such a big plane fly so fast? 

In the early days of motor vehicles they took more time to put in gear and get moving, and even longer to stop, so an intermediate light warning you that one or other action would soon be needed made sense, but not nowadays.

Having two-light signals, with a longer interval where both directions show red, would surely be a lot cheaper to build, programme and maintain.

Having just endured nights of buzzing motor scooters in Turin, can anybody explain what it is about the sound that irritates me so much but seemingly does not bother Italians who are used to it?

Peter Smith, Leicester, UK

Regardless of whether we travel at the speed of light or not, should our cells not biologically age and decay as per normal? Do we not have an internal biological clock that keeps ticking? Is Einstein proposing that our body will suffer less aging effects when travelling at the speed of light? Someone please help explain this.... 

When I was filling my car in a petrol station the other day the other day I saw a sign requesting that mobile phones be switched off. When I asked the cashier the reason for th request he said that they could cause the petrol vapour to ignite spontaneously.  I know that mobile phones emit radiation but I fail to see how they could ignite petrol.  Is this an urban myth or is it true, and if so, where did the incident that created this situation occur?

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Note to the editor: Please, feel free to edit this question to your liking.

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(a) Let's imagine a boat. The engine pushes the boat in the direction the bow is heading. When rudder is applied, it pushes the aft to the side, changing direction the bow is heading to. Now,  the engine pushes the boat in the new direction. The turn has been made.

(b) Now let's imagine a plane. The plane engine pushes our plane in the direction the nose is heading. When rudder is applied it pushes the tail to the side, thereby changing direction the nose is heading to. Now  the engine pushes the plane in the new direction. The turn has been made.

But no... the turn is, in fact,  done differently.

(c)  The pilot applies the ailerons, banking the plane, thereby splitting the aerodynamic forces from the wings, that has been vertical so far, into vertical and horizontal components; the horizontal one pushes the plane to the side; now the plane is still heading in same OLD direction, but is moving in NEW direction, moving in fact sideways. But  the engine still pushes the plane in the OLD direction. To correct that, the pilot applies the rudder, to change heading of the plane to the direction of its true movement. Now , the engine pushes the plane in the new direction. The turn has been made.

(d) So, here comes the corker. As the rudder in (c) is used for precisely the same  (objective?), as in (b), that is to change the heading of a plane into new direction, why not skip ailerons altogether? Why does a sideways movement need to be introduced first? What purpose does it serve?

Over last twenty years, I have asked this question several pilots, including commercial ones, including airliner pilots. On the (a), (b) and (c)  they had said it is 100% correct. But on (d) best I got back is “It is more efficient that way”. While inquiring further “What does it exactly mean 'more efficient' ? “, they usually assume face, that says “you are obviously too stupid to comprehend... ” and leave it at that.... . Looked to me very much, that they did not know themselves..... .

So, anyone wants to have a go?

Jerzy Sierzputowski, Melbourne, Australia.

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Note to the editor: Please, feel free to edit this question to your liking.

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Fluorescent liquids are commonly used to inspect metallic components. The liquid is painted in a thin film on the surface. It fills any cracks, which can be as small as 2mm long x 1mm deep x 10microns wide. The excess liquid is removed and then the liquid remaining in the crack spontaneously bleeds back onto the surface from the crack. 

Sometimes I don't hear a plane until it makes a loud, sudden, decelleration sort of sound - which I describe as it dropping out of warp - and then just normal jet-like noises after that. Before that, silence! So how? Why don't I hear the plane until that point and what creates the noise? I tried to google this but was unsure how to spell 'beewooooooo' to get the right response...

OK, so this question is not directly about science, but is related to science and scientists.

For the last couple of years I have been walking over Harvard bridge from Boston to Cambridge. The bridge is marked in Smoots - recalling a famous 1958 1958 MIT fraternity prank where Oliver Smoot (at 5 feet and 7 inches) was used as a unit to measure the bridge. The bridge was found out to measure 364.4 Smoots (plus or minus one ear). You can read all about Smoots here:

http://en.wikipedia.org/wiki/Smoot

The pledge class of Lambda Chi Alpha are supposed to re-paint the Smoot markings on the bridge regularly, but I have noticed that on the East side of the bridge that the signs are very faded, many of them so much so that they are unreadable. Over the last year or so the signs have not been repainted at all.

Does anyone have any idea why the signs have not been repainted. Has the recession hit the frat guys and prevented them from investing in paint? Have they just given up? Or have I missed something?

(also here is random picture of a friend on the bridge)