I’ve just returned from vacation and am returning to the blogging stint with a pun. Being relaxed and jovial and all.

Physicists hardly ever take real vacations. You know the kind, where you travel to a place just for the fun of it. Usually we just sneak a day or two extra on a work-related jaunt. (Note that visiting relatives over holidays does not count as a vacation.) However, I’ve had an epiphany in my old (post-tenure) age: real vacations are actually good for you. This year a good friend helped the cause by having a wedding in a place called Sonning-upon-Thames. Who could pass up such an idyllic locale? It was great fun – a few days in the English countryside, the wedding, and then some time in London.

So what does a physicist do while roaming about London? Take a boat cruise down the Thames to Greenwich and visit the Royal Observatory and see the Prime Meridian, naturally. What else?

Turns out the Royal Observatory is a hot tourist spot. It was packed! No wonder, since it is billed as “one of the most important historic scientific sites in the world.” Everybody wants to see the Prime Meridian (Get the pun yet?), which is billed as ” the centre of world time and space.” Their website claims:

It was founded by Charles II in 1675 and is, by international decree, the official starting point for each new day, year and millennium.

Not much of a track record for starting new millenniums, I’d say, but, hey, if it brings in the crowds….

There is lots of cool historical equipment on display, including (i) a piece of Herschel’s telescope (a humongous piece of equipment he built in his backyard – apparently his wife was worried it would fall on the children and kill them). Herschel’s discoveries include Uranus and the solar wind, and (ii) roundish measuring devices (I haven’t a clue what they were used for) that Robert Hooke (a curator at the Royal Observatory) built for Emond Halley, the 2nd Astronomer Royal, of the comet fame. You can also view the Royal telescope which was used for scientific purposes until the 1940′s when the London sky brightness became too bright (wasn’t clear if this was during or after the Luftwaffe).

And, of course, there is the Prime Meridian. The definition of the Prime Meridian was actually an important scientific advancement in its day. It enabled accurate astronomical observations and ship navigation. It paved the way for the discovery of the abberration of light , where the earth’s wobble in its orbit gives an apparent motion to stars. It was previously thought that the stars wobbled from their true position.

So, the pun. You know how when children don’t understand something that is spoken, they assign words that they know to mimic the sound? Well, it seems that adults, when conversing on noisy London streets do the same thing. When I suggested that we visit Greenwich to see the Prime Meridian, my travel companion looked at me funny and replied that we had Indian food the night before. Seems that Prime Meridian sounds awfully like Primary Indian when spoken on a busy, noisy street. Ok, it’s a bad pun, but the checkout lady in the Royal Observatory giftshop doubled up in laughter, and I will never think of the Prime Meridian the same way again.