by Melvyn Bragg
Doron Swade was in vigorous agreement with Patricia Fara about the tenuous connection between Babbage and modern computing, although there is a continuity in the legend and, after Babbage, nobody doubted one could build an engine. He also wanted to clarify the point about Lovelace often being credited as the first computer programmer. She published the first thing we would now recognise as a program.
DORON SWADE: It’s absolutely understandable that she should be so perceived because the first series of steps of instructions – we would now call it an algorithm – the first step of instructions was published under her name, or at least under her initials. The thing is that the work was Babbage’s. The concept of a program was based on Babbage’s work before Lovelace had any major involvement in the analytical engine.
While there is dispute over the extent to which Lovelace influenced Babbage, John Fuegi has checked through the mountains of correspondence records. Her tone is directive, he found, stopping Babbage from including in the notes a diatribe against the government, which she thought would backfire, telling him not to mess with her language, chastising him for losing papers she sent him. There were five postal deliveries a day in London at that time, and they were exchanging messages continually.
JOHN FUEGI: There can be no serious doubt whatsoever as to who is saying, ‘We need to move to a new stage of things, you’ve done wonderful work and I’m deeply appreciative of it, but there are several things that need to happen, we need to stress the difference … ’
MELVYN BRAGG: And this is Ada in the driving seat?
JOHN FUEGI: This is Ada in the driving seat absolutely emphatically. ‘We’ve got to move beyond difference engine discussion to analytical engine discussion. We’ve then got to move on, once we get this published, we’ve got to then line up the financing and we’ve got to build a prototype and we’ve got to do an advertising campaign.’ Other people in this circle are Brunel and Wheatstone, who are used to raising capital on a large scale to carry things out. So she says, ‘You’ve alienated the government, now we need to use other means.’
There are stories that Ada Lovelace went on to be a hard drinker and a gambler but, from what he has seen in the records, John Fuegi found that she led really quite a dull life in comparison with many other figures of the day. Her husband, though, did have financial problems. He was the owner of 220 estates that stretched south from Hampton Court to the sea, but, by the end of his life, he was borrowing from Annabella Milbanke. Ada Lovelace was gambling, but she was not doing this as much as her husband, who was later described by his descendant, the Earl of Lytton, as being of a somewhat extravagant nature. Ada Lovelace went to the races but that is what other people did, too, and the idea that she was a heavy drinker may have its roots in another, sadder aspect of her life.
JOHN FUEGI: What I think is a far more serious thing, and would be seriously compared with Coleridge, is the kind of medicine that you were given, because she dies very young and she has a very painful condition, probably cancer of the uterus but we don’t know for sure. But what she was given were clearly opiates and this was standard, this was what you did at the time.
In her last years, he emphasised, she was in rather a desperate condition, but the medications she was given were prescribed. Patricia Fara pointed to the school of historical thought that, for all the difficulties of retrospective diagnosis, she might also have had some sort of psychological illness. Then, between the drugs and the drink and possible mental illness, some of her behaviour could be extremely erratic.
PATRICIA FARA: When you read what other people said about her, I think it’s important to bear that in mind, because another interpretation of some of the encomia that have been made of her is that these are her friends trying to placate her, keep her on the straight and narrow, and to be flattering, even if they’re not really quite sincere.
Given that Doron Swade had made a case for Lovelace seeing further than Babbage, and that it was difficult to trace their direct influence on modern computing, Melvyn wanted to nail down their real impact. He was aware that Alan Turing had read Lovelace’s notes, for one thing. Doron Swade said that there was no direct connection between Babbage and modern computing and, although Babbage is called the father of computing, that genealogical metaphor is actually incorrect. The details of his designs were not really studied until the 1970s. Until then, Lovelace’s notes were the most that people had, other than encyclopaedia articles by Babbage primarily on the difference engine. There are conduits between their age and the modern computing age, but we should ask what people might have known of Babbage and Lovelace and by what route.
DORON SWADE: We’re talking about the Lovelace notes, top of the list, then we’re talking about encyclopaedia articles. So, if we’re talking about Babbage’s designs being the DNA of modern digital computer design: absolutely not possible. But the small coterie of people that were continuously involved in automatic computation knew of Babbage, the legend persisted. Turing knew of Lovelace’s notes, Lovelace’s statements that the analytic engine has no pretensions to originate anything.
The principles of modern computing, he said, were essentially reinvented by the pioneers of electronic computers in the late 1930s, early 1940s. For those years, John Fuegi suggested, there is no evidence that the first machines were moving beyond the difference machine in the way Lovelace’s notes moved beyond. They were still continuing with calculation, as though they had gone back to the difference engine rather than the analytical engine. After that it is hard to define historically when computers moved from calculating, say, the simple trajectories of artillery shells and mathematics to general-purpose computing.
Turing, Doron Swade added, was the first person to define a computer in general ways that said, ‘This is a machine that can manipulate symbols that represent things other than numbers.’ In response to John Fuegi, he found that the continuity was where the work of Babbage and Lovelace re-emerged in modern times through Turing, one of the pioneers, who made explicit reference to Lovelace’s notes.
Finally, Melvyn mentioned that, while Babbage never built his engine, Doron Swade did. It has 8,000 moving parts and weighs a number of tonnes. Like the original, it is not binary, but decimal, and those bases provide a very significant difference between Babbage’s work and modern computers, to Patricia Fara’s mind. It does, though, according to Doron Swade, work impeccably.
DARK MATTER
Something in our universe is missing, or rather, almost everything, most of the matter in existence. Scientists first noticed this in the 1930s, observing that galaxies were moving much faster than expected and, at such speed, should have dispersed or evaporated. They theorised that there must be something, as yet unknown, keeping the galaxies in place. A Swiss astronomer, Fritz Zwicky, called this ‘missing mass’ at first, and later ‘dark matter’, which is how we know it now. Before we went on air, at least one of our guests in this programme claimed that, once we do know what dark matter is, we will have solved one of the greatest mysteries in science, linking the Big Bang with the creation of galaxies, planets, earth and everything on it, including us.
With Melvyn to discuss dark matter were: Carolin Crawford, public astronomer at the Institute of Astronomy, University of Cambridge, and fellow of Emmanuel College, Cambridge; Anne Green, professor of physics at the University of Nottingham; and Carlos Frenk, Ogden professor of fundamental physics and director of the Institute for Computational Cosmology at the University of Durham.
The Sombrero Galaxy contains a vast black hole at its centre.
Carolin Crawford took us back to the 1930s and to the astronomer Fritz Zwicky, who was studying clusters of galaxies, which are swarms of galaxies, hundreds of thousands, all contained within a region a few tens of millions of light-years across, all bound together. Zwicky realised that he could use the motion of the galaxies to assess the mass of the cluster.
CAROLIN CRAWFORD: He discovered that they’re moving too fast, they’re moving at speeds of the or
der of 1,000km per second. The whole system should have just dispersed out into space, unless you’ve got more mass there, more gravity there, than you would otherwise have guessed. And that mass, that gravity’s anchoring everything, to keep it as one bound entity.
That is the point at which Zwicky identified this idea of a missing mass, the extra gravity within the system that cannot be seen by an ordinary telescope. Zwicky, at first, called it ‘missing mass’, and it was later termed ‘dark matter’ as it does not interact with light in any way – it does not block it, reflect it or absorb it. Yet there this matter is, around five times the amount of ordinary matter but not visible to astronomers, to be inferred rather than seen directly, and extremely important.
CAROLIN CRAWFORD: It is absolutely fundamental to everything in the universe. Dark matter is what anchors all structures together. Without dark matter, we couldn’t have created galaxies and clusters of galaxies. We wouldn’t have the current universe we see if we didn’t have dark matter that initiated that process right at the beginning of the universe.
There is something called the galaxy rotation curve, which has a role in this story. As Carlos Frenk explained it, a galaxy like our Milky Way is essentially a disc of stars rotating around the centre of the galaxy. A rotation curve describes how fast the stars are moving around the centre, at different distances from the centre. According to Newton’s theory of gravity, we would expect the stars closest to the centre to be going around faster than the stars further out, just like in the solar system, but that is not what scientists noticed.
CARLOS FRENK: To their horror, in the 1970s, they found that actually the stars were moving more or less at the same speed, a few hundred kilometres per second, regardless of where they were. And that was immediately recognised as a very serious problem, because essentially the stars in the outer parts of the galaxy were just going too fast.
If all the material that produces the gravity was in the stars and visible, those far-flung stars should have been flung far from the galaxy. That they had not been ejected provided clear evidence, albeit not accepted by everyone, for the existence of dark matter in galaxies like the Milky Way. There were other computer simulations about the Milky Way in the 1970s by two Princeton physicists, Jerry Ostriker and Jim Peebles, which, at first, led to the discs of galaxies crumpling up into a kind of bar, but prompted the idea that, in order to make galaxies stable, one required this dark matter.
CARLOS FRENK: The simulations were nothing compared to what we can do today, but they did manage ingeniously to assume there was some unseen ‘halo’, a clump of dark matter, and then a beautiful stable galaxy was spotted.
MELVYN BRAGG: Why did they call it a ‘halo’?
CARLOS FRENK: It is a clump. I guess clump is not such an elegant word as halo. I think the idea is that most of it is outside the galaxy, but I always think that all astronomers have saintly tendencies and this is expressed sometimes in our language.
The missing mass is described as dark, but optical light that we can see with our eyes is only a small part of the electromagnetic spectrum, and detectors that are sensitive to different wavelengths reveal very different things in galaxy clusters. Anne Green referred to the X-ray telescopes used by astronomers in the 1970s, which revealed that galaxy clusters contained a large amount of hot gas emitting X-rays, and gravity was trying to pull this gas in and the pressure was trying to stop it collapsing. Looking at this balance between pressure and gravity, it was possible to weigh the X-ray-emitting gas and compare that to the mass of the cluster as a whole.
ANNE GREEN: What they found was there’s actually a lot more [mass in the] hot gas in the cluster than [in the] galaxies, about a factor of ten roughly, but still that’s not all of the missing mass – there’s still five or six times as much stuff in the galaxy cluster on the whole as there is this hot gas. That added more information about what the dark matter had to be. It wasn’t this gas, it was something else.
Melvyn declared himself baffled by how it was possible to weigh all these things that his guests were referring to. Carlos Frenk explained that it is mass that, when put on a scale, registers as weight and, as we learn from Newton and Galileo, mass and weight are one and the same thing. Weighing something means measuring how much gravitating mass the object contains, so, if Melvyn had a mass of 80kg, that would be his weight as well as his mass.
Looking for more inferences of dark matter, Carolin Crawford turned to elliptical galaxies. Carlos Frenk had already referred to the way a flat spiral galaxy was rotating, and the way the rotation of the stars can indicate there is this extra dark matter. Most galaxies in the universe are ball-shaped elliptical galaxies, swarms of stars responding to the gravity of the galaxy, and again they are responding to much more gravity than can be detected from all the light and the stars of the galaxy. Elliptical galaxies are much more massive than spiral galaxies, with much more dark matter and, as with the clusters, there is a big halo of X-ray-emitting gas.
CAROLIN CRAWFORD: This X-ray gas is at temperatures of millions of degrees Celsius – it’s a plasma of fast-moving charged particles and these again should have just dispersed. They’ve got so much energy they should just scatter into space, unless you’ve got more gravity there to anchor them to this galaxy. [This is] evidence that this dark matter is endemic to all galaxies in the universe, whether they be spiral or whether they be elliptical.
This led to discussing the cosmic microwave background and the corroboration that this offers for dark matter. Carlos Frenk told how this background radiation is the heat left over from the Big Bang, emitted when the universe was only 350,000 years old, the equivalent of one day in a human life. As the universe expanded, the radiation cooled and, by the time it had been discovered by two engineers, Arno Penzias and Robert Wilson in 1964, it had cooled to 2.7°C above absolute zero and appeared in the form of microwaves. At the turn of the century, a NASA satellite mapped the temperature of this microwave background radiation, the heat from the Big Bang, and found that the temperature was not uniform but patchy, and, from these patterns of hot and cold spots, we can read what the universe must have had in order to produce such a pattern. From that, we learn that the universe had not only ordinary matter, like the matter of atoms of which we are made, but some form of elementary particle, different from ordinary atoms, and that was the dark matter.
CARLOS FRENK: One way to think about it [is] if you’re given a present in a box that’s wrapped and you don’t know what’s in it, what do we all do? We shake it, right? And from the vibrations in the box we try to infer what’s inside it. Well, this is very similar. This microwave background are sorts of vibrations and, by looking at the vibrations, we can infer what the universe contains.
MELVYN BRAGG: That’s terrific, isn’t it? I mean I’m just in wonder at all this sort of stuff. That’s why we do the programme.
Up until 350,000 years into its existence, the universe was a very hot, dense place and everything was broken down into nuclei, which are positively charged, and electrons, which are separate and, if an atom tried to form, a very energetic photon, a particle of light, would come along and kick the electron out of the atom again. Anne Green described that as a thick gloopy mess of particles that were scattering off each other all the time. However, at that point, in line with conservation of energy, as the expanding universe had cooled down enough, the energy dropped and atoms could form.
There is more evidence of dark matter from gravitational lensing, an idea that follows from Einstein’s theories of gravity, where his theory of general relativity tells us that mass bends space and, when light travels through space, its path becomes bent. By looking at how the path of light is distorted, we can map out how space is bent, and therefore how the matter is distributed. Sometimes, Anne Green added, we have a big galaxy cluster and then a long way behind it is a galaxy, the light of which gets bent around the galaxy cluster rather than travelling in a straight line. The cluster acts like a lens, creating multiple images of
the galaxy distorted into arcs, from which we can map out how much space has been bent and therefore how the matter is distributed.
ANNE GREEN: What you see are peaks where we know the galaxies are in the matter distribution, but surrounding the galaxies is a big additional lump of dark matter and this is the dark matter halo that Carlos has been telling us about already. So it’s telling us where the dark matter is, spread out, extended around the galaxies.
If, as it appears, there is dark matter, then one of the fundamental questions that remains is what might it be made from. The first place to start could be ordinary matter that just happened not to be luminous, perhaps a gas cloud, or black dwarfs that never became large enough to shine like stars. These are made of ordinary matter that, Carolin Crawford told us, is called baryonic matter as it is made of atoms, which are made of neutrons, protons and electrons, which, in turn, are known as baryons. There are problems with such an interpretation, as it is hard to get observations to sustain it. For example, if there is ordinary matter that is not at absolute zero, then it will give off some kind of radiation.
CAROLIN CRAWFORD: If it’s a planet, it could give off infrared radiation, a gas cloud maybe would absorb light. And you have the problem now that, with today’s detectors, if there was enough of this ordinary matter, in the quantities we need to account for the dark matter, we would have detected the glow from it.
With ordinary matter put aside, the trail leads towards non-baryonic matter. Carlos Frenk said that what clinches the fact, that the dark matter can’t be ordinary matter, is the microwave background radiation mentioned earlier, as that unambiguously tells us how much ordinary baryonic matter there is in the universe, and it tells us how much total mass there is, and the two do not add up. The bulk of the mass has to be something different from baryonic dark matter.
