Does watercolour painting suffer from an image problem? Do you think of the wild, vaporous seascapes of Turner, or Victorian ladies at their sketchbooks dabbing daintily at wishy-washy flower paintings? Do you associate the medium with radical innovation or with staid tradition? And would Jackson Pollock have appeared quite so heroic flinging thin washes of watercolour around instead of viscous oils?

Susan Hiller describes herself as a curator as well as an artist. She makes work out of objects that she’s collected over the years. She collates information, too, and personal testimonies. These all go toward making works whose primary aim is to question meanings and categories and belief systems. These belief systems are those that are often found on the outer fringes of mainstream norms – or, if you’re put off by the dry language of academe – which Hiller isn’t – the loopy stuff that’s a bit “out there”. Paranormal activity, alien abductions, séances, the healing power of holy water, levitation, auras. All these are dealt with in Hiller’s work.

Rachel Whiteread is best known for her exploration of space, of presence and absence, of how we look at what is present – and absent – in the textures of our lives. House, her life-sized cast of a house in a derelict street in East London, first brought her to fame, and more recently Untitled (Plinth), her mockingly affectionate take on the empty plinth in Trafalgar Square, a resin-cast replica of the plinth itself, literally shaped a new viewpoint of that absence in the heart of the West End.

Multiple images of silhouetted horses cantering against blank backgrounds in grids of movement are what most people associate with Eadward Muybridge. Made in the late 1880s, they have contributed to his lasting reputation as a pioneer of photography and the moving image. So it is astonishing to discover through Tate Britain’s magnificent exhibition of his life’s work, that horses were only part of a story packed with surprises.

Two recently decommissioned fighter jets are in the incongruous setting of Tate Britain's Duveen Galleries. One plane, polished to a mirror sheen, lies belly-up, like an injured animal; the other hangs suspended from the ceiling, its matt surface stripped of its combat colours and stripes, painted instead with faint feather markings, bringing to mind a giant, trussed-up bird. Its stilled presence is both powerfully majestic and inert.

This week a new exhibition with no pretence to seriousness opens at Tate Britain. Rude Britannia: British Comic Art is a comprehensive tour of a great national tradition: having a laugh in a line drawing. The show covers the boardwalk from Gilray and Cruikshank to Gerald Scarfe and Steve Bell. It also includes the work of a cartoonist and illustrator whose world view, more than any other, now seems deliciously quaint and old-fashioned: Donald McGill. All four examples from the exhibition are included here.

A little revolution is taking place at the top of the pop charts. UK artist Tinie Tempah's rap track “Pass Out” has had two weeks at number one, and at the time of writing looks very much like it may successfully fight off Lady Gaga & Beyonce's spectacularly-hyped “Telephone Thing” to make it a third week on top.

Henry Moore is said to have first encountered the image of the reclining figure in Paris in 1925 in a plaster cast of an ancient Mexican Toltec-Maya figure in the Trocadero Museum. It was to become probably his most frequently explored theme, revisited hundreds of times over the following 60 years before his death in 1986. From the relatively realistic to the almost totally abstract, Moore’s reclining figures can be seen in galleries and public spaces all over the world.