Einstein's theory of relativity may be E=mc², but it has little in common with everyday life.
Relativity, in our social circles, is measured in beer sums. For example, a 2004 purple Mini, `one lady owner and full service history', will not cost the advertised £9,750, but 4,432 pints.
Similarly, an hour-and-a-half's Premiership football will remove 16 pints from your wallet. Calculating it that way, you know where you are.
By the same scale, an all-day ticket on the City Sightseeing tour of Newcastle and Gateshead - the open-top bus - costs £7, or three pints and a packet of crisps, in exchange for seven hours of fun hopping on and off at 19 stops and five dozen pubs. A bargain by any standard - so all aboard our take on the pub heritage trail.
We start and finish at The Head of Steam on Neville Street in Newcastle - which features nine beers, including Staropramen and Budweiser Budvar from the Czech Republic, bottled beers from every brewing nation and four ales from closer to home. Along Clayton Street, round past The Gate complex and into St Andrew's Street and the Newcastle Arms, which is a fine example of an endangered species - the town centre pub. Shortly after landlord Neil Amos took it over last year, its brasses sparkled, its floorboards shone, its bar gleamed and its beer choice flourished as never before.
The power of elbow grease and six cask-conditioned beers sourced from all over the country led to it being voted Tyneside Pub of the Year 2006, by the local branch of the Campaign For Real Ale (Camra).
"There aren't enough traditional pubs like this left in Newcastle," says Neil, "and for people of a certain age. It has loads of potential; the real ales create their own market and people will go where they'll find them."
Passing Rosie's Bar (née Darn Crook and formerly the Northumberland Arms), we head past Shearer's Bar at St James's Park (as the tour commentary puts it, "the largest place of worship in the city") and The Strawberry.
The Trent House is next: student-friendly and funkily cool, offering McEwan's 80/- and Old Speckled Hen and an unrivalled jukebox. Round the university and onto the Haymarket, the City Sightseeing tape tells us of 15 witches executed on the Town Moor, Queen Victoria's bloomers donated to the Royal Victoria Infirmary, and a medicinal drink developed in a pharmacy on the site of the new Northern Stage building. It was called Glucose Aid. Wonder what happened to it?
Along Percy Street we could visit The Hotspur, another traditional bar untouched by fashion and providing a welcome range of decent ales. Harry Hotspur, the 14th Century Sir Henry Percy and eldest son of the first Earl of Northumberland, is depicted on its swinging sign with an arrow in his head. He had raised his armoured visor during the Battle of Shrewsbury in 1403 to get some fresh air. Whoosh... who ordered Strongbow?
Further along are The Percy Arms, the Three Bulls' Heads - thought to date back to 1788 though today's pub is a rebuild - The Goose and Newcastle Labour Club. A pub-free stretch takes us past Grey's Monument and The Charles Grey, a bar we've yet to darken the door of. We've a bird's eye view of Thomas Heatherwick's controversial, £1.4m Blue Carpet sculpture outside Laing Art Gallery, made of thousands of tons of crushed Harvey's Bristol Cream sherry bottles set into resin. Bristol Blue glass, an 18th Century invention, was used for high-quality decorative tableware like decanters and glasses.
Heading for the Quayside, we pass The Market Lane and Popolo, an upmarket, stylish bar that specialises in continental beers and swish cocktails. The adjacent building with the green canopy was the home of Alderman Fenwick (of the department store) and, before that, was The Queen's Head coaching inn.
We circumnavigate the frighteningly pink Bar 55. Drink and dining al fresco in the middle of one of the nation's busiest roundabouts continues to baffle. We drive past The Waterline, Pitcher & Piano, The Baltic Tavern, Flynn's, The Slug & Lettuce and round the corner to the Red House, Bob Trollope, the Quilted Camel, Offshore, something called Jimmy'z Bar, Lloyd's No 1 and The Cooperage and across the river and around The Sage Gateshead.
Beneath that glass carapace beats two concert halls and four bars. Among their unique features are handpulls designed by Lord Foster, who has a penchant for leaving his architectural finger-prints on every aspect of a building he designs. Apparently, one of the barmen questioned the use of stainless steel on the counter, saying it would mark and dent. Foster & Partners said the firm wanted to see it bear scars as it's all part of people feeling comfortable in their surroundings.
Back across the Tyne Bridge, along Market Street, a sharp left down Grey Street and we pass Fitzgeralds, part of the Sir John Fitzgerald group that operates 30 pubs in the North-East and has a commendable commitment to real ale - a good example is The Bridge Hotel near Castle Keep.
According to Brewers & Bottlers of Newcastle-upon-Tyne by social historian Brian Bennison, it was said on its acquisition in 1896 that "Sir John Fitzgerald may be regarded as one of the pioneers of the Long Bar system which has revolutionised public houses in the North.
"In the old days, houses were subdivided into stuffy, curtained-off apartments, sometimes on separate floors, inconvenient to trader and better-class customer and out of harmony with the modern hotel arrangements.
"Mr Fitzgerald strove to combat this and, by introducing roomy bars and adopting luxurious seating accommodation, he helped to inaugurate a system which has thrown an air of superior respectability into Newcastle hotel life."
The Head of Steam reappears over the top deck and we hop on to the Blue Route circular via Shieldfield and Ouseburn Valley, by The New Bridge, The Stout Fiddler and nearby Queen's Arms, and take a left opposite premises that once charged sixpence and allowed customers to drink all they could. Sadly, Gibson Street Baths has been closed for a number of years.
We go round by The Biscuit Factory's galleries, studios, café and Black Door restaurant, across New Bridge Street at Tanners on Stepney Bank (originally the Tanner's Arms). At the bottom, and once part of a terrace is The Ship Inn (known as `the top Ship', as The Tyne on Maling Street was also called The Ship until 1994). It was bought by George Younger of Alloa in 1933 and stained glass windows at the back bear the name. It became a Flower's pub in 1957, was bought by Nimmo's in 1964 for £4,750, and is now a free house.
The Cluny, where our commentary claims "the food is legendary", sits across the green in a former whisky warehouse. Clientele ranges from undergraduates to grannies, lending it a terrific, off-centre atmosphere. Beers from around the world and all parts of the country are mandatory.
Turning for home, The Egypt Cottage is regarded as Newcastle's first licensed house, existing from the early 18th Century as the Egypt Inn and later as the Egypt Tavern. The area it is in was called Little Egypt, a reference to the amount of grain stored there, piled like pyramids.
The Quayside trail is followed once more, but this journey slips up Side towards Dean Street. The Crown Posada - yet another Fitzgerald's house - is one of the city's jewels. Long, narrow and high-ceilinged with huge Pre-Raphaelite stained glass windows, it remains an oasis of calm and comfort, a provider of excellent ale and a workmanlike corned beef and tomato sandwich. Just one criticism: can the ceiling's stucco, mouldings and cornices please be restored to their former brightly-painted glory?
The most frequent comment from passengers along the two City Sightseeing routes is: "I've never noticed that before." It's the theory of relativity almost becoming relevant. Albert Einstein's paper, On the Electrodynamics of Moving Bodies, introduced the equation in 1905 - and, 101 years later, it's a relatively good way of moving bodies towards pubs and pints. Hold very tight please...
* Research aided enormously by Brian Bennison's Newcastle pub history series, Heady Days, Heavy Nights and Lost Weekends (Newcastle Libraries, £4.99). NewcastleGateshead City Sightseeing Tours depart every hour (Red Route) and every half-hour (Blue Route) from points around the city. Enquiries: 0871 666 0000, www.city-sightseeing.com