Comparisons – Page 8 – Science-Education-Research

galaxies are like dots on an inflating balloon

An example of a teaching analogy used to explain an abstract idea in a popular science book,

"the galaxies are rushing away from each other at enormous speeds…

the analogy of a balloon with a large number of dots marked on its surface. If the balloon is blown up the distances between the dots increase in the same way as the distances between the galaxies. Here I should give a warning that this analogy is must not be taken too strictly. There are several respects in which it is definitely misleading. For example, the dots on the surface of a balloon would themselves increase in size as the balloon was being blown up. This is not the case for the galaxies, for their internal gravitational fields are sufficiently strong to prevent any such expansion. A further weakness of our analogy is that the surface of an ordinary balloon is two-dimensional – that is to say, the points on its surface can be described by two coordinates; for example, by latitude and longitude. In the case of the Universe we must think of the surface as possessing a third direction.. …
But then what does the radius of the balloon represent, and what does it mean to say the balloon is being blown up? The answer to this is, that the radius of the balloon is a measure of time, and the passage of time has the effect of blowing up the balloon.…

The balloon analogy brings out a very important point. It shows we must not imagine that we are situated at the centre of the universe, just because we see all the galaxies to be moving away from us. For, whichever dot you care to choose on the surface of the balloon, you will find that the other dots all move away from it. In other words, whichever galaxy you happen to be in, the other galaxies will appear to be receding from you."
Fred Hoyle (1960) The Nature of the Universe (Revised ed.)

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Many examples of science analogies are listed in 'Creative comparisons: Making science familiar through language. An illustrative catalogue of figurative comparisons and analogies for science concepts'. Free Download.

phrenology is like the astronomy of Copernicus

An example of an analogy to a scientific idea:

"Typically, Robert Chalmers wrote: 'To me, Phrenology appears to bear the same relation to the doctrine of even the most recent metaphysicians [as] Copernican astronomy bears to the system of Ptolemy'."
Cooter, R. (1984). The Cultural Meaning of Popular Science. Phrenology and the organization of consent in nineteenth-century Britain. Cambridge University Press.

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Phrenology involved the 'reading' of features of personality from the shape of a person's skull (believed to reflect the relative development of different underlying brain faculties.)

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Phrenology was at one time a widely respected 'science', although it would today be seen as a pseudoscience or alternative conceptual framework.

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Historical examples of alternative conceptions

rocky planets condensed like raindrops in a cloud

An example of an analogy used to explain a scientific idea:

"…how could the Earth and the other inner planets – Mercury, Venus, and Mars – ever have been formed? Well, certain quite rare materials did not stay in gaseous form. They condensed out of the gas as solids and liquids in a manner analogous to the formation of raindrops in the clouds of the terrestrial atmosphere."
Fred Hoyle (1960) The Nature of the Universe (Revised ed.)

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magnetic field from the Sun to the planetary material behaves like elastic strings

An example of figurative language in popular science writing:

"Already, more than a century ago, Faraday showed that a magnetic field can be thought of as a collection of lines of force that behave in many ways like elastic strings. So a magnetic field extending outwards from the Sun to the planetary material would behave like a vast aggregate of elastic strings. And as the Sun rotated the strings would become stretched and twisted into a structure rather like a clock-spring. By calculation it can be shown that rather a moderate magnetic field would be sufficient to give a clock-spring winding strong enough to maintain the required connexion from Sun to planets. In short, the torque that conveyed rotational momentum from the Sun to the planetary material was maintained by a magnetic clock-spring. …

Next we bring our clock-spring into action. The magnetic fields existing already inside the solar condensation provided a bridge between the primeval Sun and its newly grown disc. The magnetic field would become wound into a 'clock-spring' and rotational momentum began to pass from the Sun to the disc.

…once they had condensed from the gas these these materials were no longer subject to the clock-spring action of the magnetic field. …

Which stars are without planets? Almost certainly the rapidly spinning blue giants, and for a reason that is readily understood. Any attempt [sic] to transfer rotational momentum from these stars to an outlying planetary disc is frustrated, not by any lack of a magnetic clock-spring, but because the clock-spring becomes much too strong, It becomes so strong that the outlying disc gets blown completely away into space."
Fred Hoyle (1960) The Nature of the Universe (Revised ed.)

That a magnetic field behaved like elastic strings is a simile, although this then get used as a metaphor ("…as the Sun rotated the strings…") that is withour any marking to show the strongs were figurative. Similarly the structure the 'strings' formed was like a clock-spring (another simile); but again this is then used as a metaphor ("…we bring our clock-spring into action…").

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Many examples of science similes are listed in 'Creative Comparisons: Making Science Familiar through Language. An illustrative catalogue of figurative comparisons and analogies for science concepts'. Free Download.

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Many examples of science metaphors are listed in 'Creative comparisons: Making science familiar through language. An illustrative catalogue of figurative comparisons and analogies for science concepts'. Free Download.

matchbox full of material from a star about to supernova contains about 1000 tonnes

An example of an everyday comparison (a matchbox) used to explain an unfamiliar scale phenomenon,

"Calculation tells us a good deal about the state of a supernova just before the outburst….It is so enormously dense that a matchbox full of material taken from is central regions contains about 1, 000 tons. Its surface rotations with a speed of about 10,000,000 miles an hour. And the time required for its catastrophic outburst is as little as one minute. Indeed, if some cosmic jester were to grab hold of the Earth and were to put us near such a body, the whole of the Earth would be entirely crushed and would be spread as thin scum over the surface of the body. This is not just a piece of whimsical nonsense, because much of the material of the Earth actually was at one time part of a supernova."
Fred Hoyle (1960) The Nature of the Universe (Revised ed.)

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A document listing a wide range of examples of science analogies, similes, metaphors and other comparisons, drawn from diverse sources, can be downloaded using this link: 'Creative Comparisons: Making Science Familiar through Language. An illustrative catalogue of figurative comparisons and analogies for science concepts.'

The extract also includes an odd rhetorical flourish:

claim: if some cosmic jester were to grab hold of the Earth and were to put us near such a body, the whole of the Earth would be entirely crushed and would be spread as thin scum over the surface of the body
status of claim: This is not just a piece of whimsical nonsense
justification of status: because much of the material of the Earth actually was at one time part of a supernova.

This makes little sense from a logical perspective. If may well be true both (1) that "if…the Earth would be entirely crushed…" and (2) that "much of the material of the Earth actually was at one time part of a supernova", but (2) offers no rationale that justifies (1).

supernova is a million million million million times as violent as a explosion that would destroy a city

An example of an everyday comparison used to explain a more abstract idea:

"One hydrogen bomb would be sufficient to wipe out the whole of London. But compared with a supernova a hydrogen bomb is the merest trifle. For a supernova is equal in violence to about a million million million million hydrogen bombs all going off at the same time."
Fred Hoyle (1960) The Nature of the Universe (Revised ed.)

Whilst, thankfully, a hydrogen bomb is not an everyday phenomenon, Hoyle uses a well-known city to offer a scale for thinking about a supernova explosion.

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star breaks up like a gigantic Catherine wheel

An example of simile used in popular science writing:

"So long as the radiation that escapes from the surface of a star like this is the sole cause of the collapse nothing very violent can happen. The rotary forces increase too slowly for that. What happens is that the star breaks up, not in one enormous explosion, but through the steady showering off of material, rather like a gigantic catherine wheel."
Fred Hoyle (1960) The Nature of the Universe (Revised ed.)

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massive stars are extremely prodigal

An example of metaphor used in popular science writing:

"…consider a supergiant that contains ten times as much material as the Sun. Such a star would be at least a thousand times brighter than the Sun. The reason for this is that massive stars are extremely prodigal in the rate at which they consume hydrogen."
Fred Hoyle (1960) The Nature of the Universe (Revised ed.)

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Prodigal means "spending or using large amounts of money, time, energy, etc., especially in a way that is not very wise" (https://dictionary.cambridge.org/dictionary/english/prodigal), so arguably this is an anthropomorphic metaphor, as only a sentient being could be wise, or act in a way that was not wise. A star does not consider practical or ethical considerations, but just reflects the laws of physics.

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Many examples of anthropomorphism are listed in 'Creative comparisons: Making science familiar through language. An illustrative catalogue of figurative comparisons and analogies for science concepts'. Free Download.

star runs out fuel like a housewife runs out of coal

An example of an analogy used in a popular science book:

"We know the rate at which hydrogen is being consumed in some chosen star. So if we also know how much hydrogen was initially available it is a fairly straightforward calculation to find how long the supply will last in this star. Every housewife makes similar calculations. Knowing the rate at which you burn coal and how much coal you have got, it is easy enough to see how long it will be before you run out of fuel. The calculations of the astrophysicist are exactly similar to this in principle though more complicated in detail. Hydrogen takes the place of the coal, and the rate at which it is being consumed can be got from the brightness of the star, just as you could get an idea of how much coal you were using from the heat of your fire."
Fred Hoyle (1960) The Nature of the Universe (Revised ed.)

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This example seems anachronistic (as well as sexist) now, but at the time Hoyle was writing most people in urban locations (in the UK at least, and likely in many other countries) had coal fires, and a small 'bunker' outside the house for storing coal. Coal was bought by the bag, delivered to the bunker by a representative of the vendor.

stars Castor and Pollux are partners

An example of metaphor in popular science writing:

"Castor is one of the two bright stars of Gemini, a constellation of the Zodiac. Together with its partner, Pollux, it can be seen on any clear winter night."
Fred Hoyle (1960) The Nature of the Universe (Revised ed.), 1960

[Presumably the observational comment relates to Northern hemisphere observers.]

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Castor and Pollux are named after two mythical half-brothers, and the 'partners' reference is perhaps more relevant to the mythical characters (said to be twins 'gemini' although having different fathers).

Although the stars are in the same constellation, the constellations are not actually closely located groups of stars, but merely groups that have been psychologically associated from the perspective of earth observers. So, although appearing close from our viewpoint Castor and Pollux are actually very far apart. Nor can they be considered as 'partners' by virtue of being similar kinds of stars:

"Castor lies at a distance of 51 lightyears while Pollux is closer at 33.8 lightyears….

Pollux is brighter and shows a more orange-hued colour than its mythological twin…Visually, Castor is dimmer and more yellow than orange Pollux….

Pollux is an old giant star…[whereas Castor] is in fact a complex multiple star."
BBC Sky At Night Magazine

Gemini - star map — The constellation of Gemini (By AugPi – English Wikipedia, CC BY-SA 3.0)

once a stellar family is separated we cannot put them together again

An example of metaphorical language in popular science writing:

"…the general field of stars is really a superposition of many disrupted stellar families – each disintegrating star group contributes a new family…

Once the clusters have separated we mostly find ourselves in the position of the King's men – we can't put them together again … But very recently O. J. Eggen has indeed succeeded in identifying members of several very large old families."
Fred Hoyle (1960) The Nature of the Universe (Revised ed.)

The 'families' are metaphorical (like suggesting the molecules of water within one raindrop are a family),

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The 'position of the King's men' is presumably a reference Hoyle assumed would be familiar to all his readers: from when "all the King's men" could not put Humpty Dumpty together again, after he shattered on falling off a wall. (This will be a very obvious reference to many, but may seem obscure to some readers if not familiar with Lewis Carrol's story of Alice through the Looking Glass ('Through the Looking-Glass, and What Alice Found There'.)

Humpty Dumpty sits on a wall and holds out his hand to Alice. — Illustration of Humpty Dumpty from Through the Looking Glass, by John Tenniel, 1871. (From Wikimedia commons: https://commons.wikimedia.org/wiki/File:Humpty_Dumpty_Tenniel.png)

When Hoyle writes "we can't put them together again" he presumably does not mean the obvious point that we do not have technology that allows us to rearrange stars in space, but rather intends this figuratively – that is, that often (cf. the work of Eggen), we cannot even work out which isolated stars were previously in the same cluster.

groups of stars become separated when passing through dense traffic

An example of metaphorical language in popular science writing:

"These large globular clusters move along orbits that lie for the most part quite outside the plane of the Milky Way. In astronomical phraseology, they spend most of their time in the halo of the Galaxy, not in the disc. And this is precisely why they have managed to survive for so long as separate compact groups – the stellar traffic along their orbits has been low. But similar groups in the disc of the Galaxy moved along orbits where the traffic density was high, with the consequence that they were slowly loosened and their constituent stars gradually escaped into the general field…

The recently formed smaller groups are disrupted still more easily. Indeed, some groups, such as one in the constellation of Perseus, seem to be disrupting spontaneously. Others separate only by passage through dense traffic. The famous group of the Pleiades is not one of the spontaneous disintegrators. But the stellar traffic will inexorably scatter the Pleiades, until in about 500 million years little will remain of this at present spectacular cluster."
Fred Hoyle (1960) The Nature of the Universe (Revised ed.), 1960

A number of terms here seem to be metaphorical in origin, especially the references to stellar 'traffic' ,

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