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A balanced view of radon

OliUsher27 August 2015

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Thin, fragile, light, and barely visible against the padding that keeps it intact, this object is nevertheless reflects an important period in the history of chemistry – a period in which UCL led the world.

Around the turn of the 20th century, UCL’s chemistry labs saw most of the key discoveries related to the noble gases. William Ramsay isolated helium and argon here in 1895, and went on to discover krypton, neon and xenon in 1898. Over the next few years, experiments at UCL proved that radon, discovered by Friedrich Dorn in Germany, also belonged to this group. (Ramsay won UCL’s first Nobel Prize for his work on these gases.)

The delicate quartz balance in the image above is one of the most important pieces of apparatus used in this research on radon. It was used by UCL chemist Robert Whytlaw-Gray to weigh a sample of radon and determine its density for the first time. A schematic of the balance is shown below:

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The balance held a tiny sample of radon in the chamber on its right, and was balanced inside a vacuum flask with a weight attached to the balance’s other side. Despite the tiny quantity of gas involved, this was enough to determine radon’s properties.

It is held by UCL’s chemistry collections, along with other artifacts relating to this period in UCL’s history, including William Ramsay’s Nobel Prize medal and citation.

 

Vintage space: Venus in 1991

OliUsher28 July 2015

On 5 May 1989, the Space Shuttle Atlantis released the Magellan probe into low Earth orbit.

A short while later, Magellan’s rockets fired, sending it towards the sun.

Magellan being deployed from the Space Shuttle Atlantis on 5 May 1990. Photo: NASA (public domain)

Magellan being deployed from the Space Shuttle Atlantis on 5 May 1989. Credit: NASA

Swinging around our star, it arrived at its destination 15 months later: the planet Venus.

Venus is in some respects the most Earth-like planet in the Solar System. It is a similar size to our planet, has a rocky surface and a thick cloudy atmosphere. However, it is much closer to the sun, and thanks to its atmosphere, experiences a powerful greenhouse effect.

The planet Venus, seen by Mariner 10. Credit: NASA (processing by Ricardo Nunes)

The planet Venus, seen by Mariner 10. Credit: NASA (processing by Ricardo Nunes)

Surface temperatures there are well over 400 degrees Celsius, atmospheric pressure is similar to what submersibles experience a kilometre down into Earth’s oceans, and the ‘air’ of Venus’ atmosphere is full of sulphuric acid.

Exploration of Venus’ surface has been in the form of brief snapshots, taken in the few tens of minutes that landers survive the harsh conditions there. All the landers so far have been Soviet; UCL has a number of their photos in its Centre for Planetary Sciences’ image archive (with a selection available online in high resolution).

The surface of Venus seen by the Venera 13 probe. Credit: UCL RPIF

The surface of Venus seen by the Venera 13 probe. Credit: UCL RPIF

Observing Venus from space is less challenging – and less rushed.

Between 1990 and 1994, Magellan was able to study the planet’s surface at leisure from its position high above the atmosphere. Because of the thick clouds, its images had to be produced by radar rather than optical photography, so they are not in colour. But they are extremely sharp.

Here is one of these images, held in UCL’s archives:

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One of Magellan’s radar images of Venus’ surface. (The image is squint in the original!). Credit: UCL RPIF

Most of the highly processed images from Magellan are produced by multiple passes of the spacecraft over the planet’s surface, building up a complete image of the surface. This particular picture, however, is incomplete, revealing how Magellan’s images are put together. The black stripes show the gaps between the strips observed during different orbits of the planet.

Also in UCL’s archives are some of the planning documents NASA produced as part of the mission, including this full map of the planet’s surface:

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Planning chart for the Magellan mission. Click here for labelled image showing the location of the above radar map. Credit: UCL RPIF

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Solar eclipse

OliUsher20 March 2015

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The clouds didn’t part, but there was a great turnout for the eclipse party in the quad this morning. (So great that all the smartphones made eduroam a bit unreliable – sorry for the occasional breaks in the stream.)

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Thanks everyone for coming – and see you for the next big one in 2026!

Scientific advice on cutting your Christmas cake

OliUsher18 December 2014

Francis Galton was a pioneer of genetics and heredity (if you like him) or eugenics (if you don’t). He was also Charles Darwin’s cousin. Although Galton never worked at UCL, he was close to the institution, in particular as a close collaborator of Karl Pearson, the founder of UCL’s statistics department. Galton left his collections to the college on his death in 1911.

He was unquestionably brilliant, but also a problematic figure, particularly by today’s standards. In his partial defence, the term ‘eugenics’ – which he coined – was far less loaded in his time than it is today. The depravity of the Third Reich was yet to come, and the worst abuses of European colonialism were not widely known. Both, of course, were rooted in the ‘scientific’ racism of eugenics. Moreover, things which are quite uncontroversial today, such as contraception, were considered to be part of eugenics.

But for good reasons, he remains controversial.

Galton cakes

Galton was a polymath, working across disciplinary boundaries and making contributions to many areas of knowledge. One of his more offbeat proposals is reproduced above: a letter to Nature, proposing a new and efficient way of cutting cakes, based on ‘scientific principles’. ‘Scientific principles’ in this case appear to mean avoiding the cut surfaces drying out, no matter how ridiculous the method turns out to be.

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Here at the UCL Science blog, we think his work on cake is like his work on heredity: historically interesting, but contentious.

We would also like to propose a more efficient way of slicing a cake, which like Galton’s, avoids the surfaces drying out, but unlike Galton’s, requires no elastics and produces equally-sized and shaped slices: cut the cake horizontally.

Merry Christmas.

Tip of the hat to Prof Joe Cain.

 

 

 

Fossil crab

OliUsher17 November 2014

Fossilised crab. Credit: UCL Geology Collections

Fossilised crab. Credit: UCL Geology Collections

This specimen, from UCL’s Geology Collections, shows a well-preserved fossilised crab. Its legs are largely intact and even the texture of its abdomen can be made out. The claws, however, are missing.

Crabs’ claws are one way to tell male and female specimens apart (males’ claws are generally larger). Interestingly, the shape of a crab’s underside also hints at its sex in most species.

(Any amateur or expert determinations of this crab’s sex are most welcome in the comments below.)

Crabs have existed since the Jurassic period, 145-200 million years ago.

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High resolution images