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{{Infobox scientist
| name = Ivor Catt
| image = Ivor Catt 446.jpg
| alt = Ivor Catt
| birth_date = {{birth date|1935|12|19|df=y}}
| death_date = {{death date and age|2025|6|21|1935|12|19}}
| fields = Electronics engineering, [[Electromagnetism]]
| residence = St Albans, Hertfordshire, United Kingdom
| nationality = English
| workplaces = Motorola; Sperry; Ferranti; Anamartic
| known_for = The Catt Question; wafer-scale integration; [[Electromagnetism|electromagnetic theory]]
}}

'''Ivor Catt''' (19 December 1935 – 21 June 2025) was a British electronics engineer known both for pioneering work on high-speed digital logic and wafer-scale integration and, more controversially, for a heterodox account of electromagnetism built on the ideas of Oliver Heaviside. He took a B.A. in engineering at Trinity College, Cambridge, published influential work on crosstalk and interconnection delay in digital systems, and patented the wafer-scale integration technique commercialised in the late 1980s by the British company Anamartic. From the late 1970s onwards he argued, chiefly in the pages of ''Wireless World'' and its successor ''Electronics World'', that the textbook treatment of electric current, charge and displacement current is incoherent, and he spent four decades pressing the physics establishment for an answer to what became known as the Catt Question.

==Biography==
Catt was born on 19 December 1935 in Devon, England, and spent part of his childhood on an RAF airbase in Singapore, leaving with his mother and sister shortly before the Japanese invasion of 1942. He did National Service in Germany, won a State Scholarship in mathematics, and then read engineering at Trinity College, Cambridge, taking his B.A. degree.

He married Freda Mansfield in 1959; the couple had one son. He lived for many years in St Albans, Hertfordshire, from where he ran his own publishing imprints and, from the 1990s, an extensive personal website archiving his writings and his correspondence with academic physicists. Catt died on 21 June 2025 at Watford General Hospital, aged 89.

==Engineering career==
Catt spent six years during the 1960s working for five different electronics companies in the United States, including Motorola, at the point when digital logic was becoming fast enough that the interconnections between chips, rather than the chips themselves, set the limits on system performance. His response was to treat printed-circuit wiring not as lumped capacitance and inductance but as transmission line, and to analyse logic signals as transverse electromagnetic (TEM) steps propagating between conductors.

The best-known product of that work is his 1967 paper on crosstalk in digital systems, published in the ''IEEE Transactions on Electronic Computers''. In it he distinguished the even mode and odd mode of propagation on coupled lines and derived from their differing velocities the phenomena he named differential crosstalk, fast crosstalk and slow crosstalk — an analysis that displaced the earlier stray-capacitance and stray-inductance rationalisations then used by designers. He followed it with work on signal transmission and interconnection delay in digital systems, and later set out the whole engineering approach in textbook form in ''Digital Electronic Design'' and, with David Walton and Malcolm Davidson, in ''Digital Hardware Design'' (Macmillan, 1979).

Returning to Britain, he worked in the computer industry and continued to publish on high-speed digital design. This side of his output is uncontroversial and well received: the transmission-line view of digital interconnect that he advocated in the 1960s is now standard practice in signal-integrity engineering.

==Wafer-scale integration==
Catt developed and patented ideas on wafer-scale integration (WSI) in 1972. Conventional practice was to dice a silicon wafer into individual chips and discard those containing defects; Catt's scheme instead kept the wafer whole and used a self-configuring interconnection path — christened the ''Catt Spiral'' — that tested each cell in turn and routed around the faulty ones, so that partially faulty wafers (''partials'') could be used rather than thrown away.

Academic journals rejected his papers on the subject, and he eventually published the work in ''Wireless World'' in 1981. In the mid-1980s the British company Anamartic, funded by Tandem Computers and Sir Clive Sinclair among others, was formed to manufacture "superchips" based on the technique. The approach was widely reported as revolutionary, with predictions of cheap supercomputers assembled from mass-produced components and of solid-state replacements for magnetic disk storage. Anamartic shipped its Wafer Stack solid-state memory in 1989, and the product won an industry Product of the Year award; Catt also received ''Electronic Design'' magazine's "best product of the year" award on 26 October 1989. The company was unable to secure a sufficient supply of silicon wafers and folded in 1992.

==Electromagnetic theory==
Catt's electromagnetic writing begins from the engineering situation he knew best — a logic transition travelling down a pair of conductors — and asks whether the conventional description of that situation is self-consistent. His central claim is that it is not, and that the difficulty is not a subtlety at the edge of the theory but a contradiction in its first chapter.

===The Catt Question===
The Catt Question, earlier called the Catt Anomaly, was first put in ''Wireless World'' in 1981–82. Consider a TEM step — a logic transition from low to high — travelling from left to right in the vacuum between two conductors, a signal line and a 0 V line, at about one foot per nanosecond. As the step advances, new lines of electric flux appear between the conductors, and extra negative charge must appear on the surface of the lower conductor to terminate them. Catt's question is simply: where does that new charge come from?

He argued that the available answers exclude one another. It cannot come from the upper conductor, because by definition displacement current is not a flow of real charge. It cannot come from the left along the conductor, because charge arriving from behind the step front would have to travel at the speed of light, which conventional theory forbids for the drift velocity of electric current. Catt therefore put the question to leading physicists and engineers and published their replies verbatim. He classified the responses into "Southerners", who held that the charge comes up out of the body of the conductor — the answer given by Professor (later Sir) Michael Pepper FRS — and "Westerners", who held that it arrives from behind along the line, the answer given by Dr Neil McEwan, then Reader in Electromagnetism at Bradford. Professor Philip E. Secker answered on behalf of the Institution of Electrical Engineers in 1995, and further correspondence followed with Professor Archie Howie FRS of the Cavendish Laboratory and the Nobel laureate Professor Brian Josephson.

For Catt the scandal was less that any particular answer was wrong than that accredited authorities gave flatly contradictory answers and that none would address the contradiction. He insisted throughout that the Catt Question is a question and not a theory: it asks the profession to state, in a signed and dated document, what conventional theory actually says. For years he offered a cash prize, latterly £2,000 lodged with the editor of ''Electronics World'', to any student who could obtain such a statement from an accredited lecturer or textbook author. He closed the offer in 2017, reporting that no one had claimed it.

===Theory N and Theory H===
Catt framed the history of electromagnetism as a succession of theories. "Theory N" is the conventional or Newtonian textbook account, in which a battery drives electric current along wires, and that current is the cause of the magnetic field surrounding the wires and of the electric field between them. "Theory H" is the account he attributes to Oliver Heaviside, quoting Heaviside's own words: "We reverse this; the current in the wire is set up by the energy transmitted through the medium around it." On this reading the primary entity is energy current — the Poynting flow guided between the conductors at the speed of light — and the conductors are, in Heaviside's term, merely "obstructors" in which current and surface charge appear as consequences.

Catt argued that once Theory H reverses the causality in this way, electric current and electric charge become superfluous descriptive baggage that can be excised altogether, leaving the TEM step, or Heaviside signal, as the fundamental object. He called the resulting position "Theory C" and first set it out in ''Wireless World'' in December 1980; it gives his 1982 book its title, ''The Death of Electric Current''. Under Theory C the TEM wave is the only physically possible expression of electric and magnetic field, the two fields are indissolubly linked in the ratio of 377 ohms in vacuo, and static fields and fields propagating at other than the speed of light do not exist. Catt held that this excision also dissolves the Catt Question, since there is then no surface charge whose origin needs explaining.

===Displacement current===
Running through the same series of articles is Catt's sustained argument that displacement current is unnecessary. Beginning with the December 1978 ''Wireless World'' article written with Malcolm Davidson and David Walton, and continuing in the historical survey published in March 1979 and in "Maxwell's Equations Revisited" in March 1980, he traced how the concept entered the theory through Maxwell's mechanical model of the aether and argued that it survives as a formal patch rather than as a physical process. In Catt's account displacement current is not a current at all — no charge moves — and everything it is invoked to explain is already carried by the propagating TEM step. His reading of [[James Clerk Maxwell]] is correspondingly revisionist: he held that the equations as taught are Heaviside's compact reformulation, and that the physical picture attached to them in textbooks is a later accretion.

===Collaboration with Davidson and Walton===
Much of the early theoretical work was joint. [[Malcolm Davidson]] and David Walton co-authored the ''Wireless World'' displacement-current papers with Catt and are named with him on the digital design textbook ''Digital Hardware Design''; the trio's papers are commonly cited as "Catt, Davidson and Walton". Walton in particular contributed to the analysis of the capacitor as a transmission line, the argument later published as "The Resistive Capacitor" — that a capacitor is properly understood not as a lumped store of charge but as a short, low-impedance transmission line in which TEM steps reverberate.

==Criticism of the scientific establishment==
Catt's technical dissent was inseparable from a broader critique of how scientific knowledge is policed. In ''The Catt Concept: The New Industrial Darwinism'' (1971), written after six disillusioning years in American electronics firms, he attacked the hire-and-fire culture of the industry — his "New Social Darwinism" — as a system that systematically destroys the creativity it claims to reward. ''Computer Worship'' (1973) extended the argument to the computer industry's institutional self-regard.

His 1978 paper "The Rise and Fall of Bodies of Knowledge", published in ''The Information Scientist'', set out the general thesis: that a discipline's literature and its peer-review machinery come, over time, to protect the existing body of knowledge rather than to test it, so that a well-posed objection can simply fail to be published, discussed or answered. He documented what he took to be his own case in ''The Catt Anomaly: Science Beyond the Crossroads'' (1996/2001), which reproduces his correspondence with physicists and institutions, and in ''The Hook and the Sting''. In 1989 ''New Scientist'' reported his proposal for an electronic network by which researchers might circulate ideas and bypass what he saw as bigoted editorial censorship.

==Reception==
Catt's engineering work is straightforwardly part of the mainstream record: the 1967 crosstalk paper appeared in an IEEE journal and is still cited, his wafer-scale integration patents attracted major industrial backing, and the resulting product won industry awards. ''New Scientist'' in 1986 caught the ambivalence with which the semiconductor industry regarded him: "Depending on whom you talk to in the generally conservative semiconductor industry, Catt is either a crank or a visionary. For 20 years, he has been refining the theoretical foundations for a revolution in the semiconductor industry."

His electromagnetic work has had a different reception. Academic physics journals did not take up his theoretical papers, and the debate was carried instead in the trade press — ''Wireless World'' and ''Electronics World'' ran his articles and the ensuing letters from December 1978 into the 2010s. Physicists who replied to the Catt Question generally treated it as a question with a settled textbook answer that Catt had declined to accept, and several published resolutions have been offered; Catt's reply was that the resolutions offered were mutually inconsistent, which was his point. His non-technical books met sharp criticism as well: ''Kirkus Reviews'' dismissed ''The Catt Concept'' in 1971 as a contrived and muddled work resting on "one man's bitter and limited experience", though the book was published in six languages.

Among researchers outside the mainstream his work has been influential and widely discussed, and the Catt Question in particular has been taken up, extended and disputed by writers including Forrest Bishop, Stephen J. Crothers and Nigel Cook.

==Selected articles==
* "Crosstalk (Noise) in Digital Systems", ''IEEE Transactions on Electronic Computers'', vol. EC-16, December 1967, p. 749-758.
* "The Rise and Fall of Bodies of Knowledge", ''The Information Scientist'', vol. 12, no. 4, December 1978, p. 137-144.
* "Displacement Current" (with Malcolm Davidson and David Walton), ''Wireless World'', Dec. 1978, p. 51-52.
* "[http://www.ekkehard-friebe.de/displacement-current.pdf The History of Displacement Current]" (with Malcolm Davidson and David Walton), ''Wireless World'', March 1979, p. 67-68.
* "Maxwell's Equations Revisited", ''Wireless World'', March 1980, p. 77-78.
* "The Hidden Message in Maxwell's Equations", ''Electronics & Wireless World'', November 1985, p. 35-36.
* "The Conquest of Thought", ''Electronics & Wireless World'', 1987, p. 1250-1251.
* "The Conquest of Truth", ''Electronics & Wireless World'', 1988, p. 48, 54.
* "[http://www.electromagnetism.demon.co.uk/catanoi.htm The Catt Anomaly]", ''Wireless World'', Internet 2000.
* "The End of the Road", ''Electronics World'', April 2013.

==Abstracts==

* 2012 - "[[What Happened to Electromagnetic Theory]]" ([http://www.naturalphilosophy.org/pdf/abstracts/abstracts_6590.pdf Read in full])
* 2012 - "[[The Resistive Capacitor]]" ([http://www.naturalphilosophy.org/pdf/abstracts/abstracts_6592.pdf Read in full])
* 2011 - "[[Does Faraday Allow Superposition?]]" ([http://www.naturalphilosophy.org/pdf/abstracts/abstracts_6168.pdf Read in full])
* 2011 - "[[The End of Electric Charge and Electric Current as We Know Them, Part 1]]" ([http://www.naturalphilosophy.org/pdf/abstracts/abstracts_6227.pdf Read in full])
* 2011 - "[[The End of Electric Charge and Electric Current as We Know Them, Part 2]]" ([http://www.ivorcatt.org/x121.pdf Read in full])
* 1998 - "[[A Difficulty in Electromagnetic Theory]]"
* 1988 - "[[The Conquest of Truth]]"
* 1987 - "[[The Conquest of Thought]]"
* 1984 - "[[Fundamentals of Electromagnetic Energy Transfer]]" ([http://www.naturalphilosophy.org/pdf/abstracts/abstracts_6588.pdf Read in full])
* 1982 - "[[The Death of Electric Current]]" ([http://www.naturalphilosophy.org/pdf/abstracts/abstracts_6218.pdf Read in full])
* 1980 - "[[Maxwell's Equations Revisited]]"
* 1979 - "[[The Heaviside Signal]]"
* 1979 - "[[The History of Displacement Current]]"
* 1978 - "[[Displacement Current]]"
* 1978 - "[[The Rise and Fall of Bodies of Knowledge]]"
* 1978 - "[[The Two T.E.M. Signals]]"
* 1969 - "[[Signal Transmission in Digital]]" ([http://www.naturalphilosophy.org/pdf/abstracts/abstracts_6237.pdf Read in full])
* 1967 - "[[Crosstalk (Noise) in Digital Systems]]"
* 0 - "[[The Catt Question]]" ([http://www.ivorcatt.co.uk/cattq.htm Read in full])
* 0 - "[[The Transverse Electromagnetic Wave. A TEM Step]]" ([http://www.ivorcatt.co.uk/x142.htm Read in full])

==Books==

* 1996/2001 - "[[The Catt Anomaly: Science Beyond the Crossroads]]" ([http://www.amazon.com/Catt-anomaly-Science-beyond-crossroads/dp/0906340152/ref=sr_11_1?ie=UTF8&qid=1218895806&sr=11-1 Read in full])
* 1996 - "[[The Hook and the Sting]]" ([http://www.amazon.com/Hook-Sting-Ivor-Catt/dp/0906340098/ref=sr_1_10?s=books&ie=UTF8&qid=1305143926&sr=1-10 Read in full])
* 1994 - "[[Electromagnetism I]]" ([http://www.amazon.com/Electromagnetism-I-Ivor-Catt/dp/0906340071/ref=sr_1_16?ie=UTF8&s=books&qid=1218905100&sr=1-16 Read in full])
* 1987 - "[[Oliver Heaviside the Man]]"
* 1980/1986 - "[[Electromagnetic Theory, Volume 2]]" ([http://www.amazon.com/Electromagnetic-theory-Ivor-Catt/dp/0906340039/ref=sr_11_1?ie=UTF8&qid=1218906298&sr=11-1 Read in full])
* 1979 - "[[Digital Hardware Design]]" ([http://www.amazon.com/Digital-Hardware-Design-Ivor-Catt/dp/0333259815/ref=sr_1_1?ie=UTF8&qid=1305134567&sr=8-1 Read in full])
* 1979 - "[[Electromagnetic Theory, Volume 1]]" ([http://www.amazon.com/Electromagnetic-Theory-Ivor-Catt/dp/0906340020/ref=sr_1_13?ie=UTF8&s=books&qid=1218905100&sr=1-13 Read in full])
* 1978 - "[[Digital Electronic Design, Volume 1]]"
* 1978 - "[[Digital Electronic Design, Volume 2]]"
* 1973 - "[[Computer Worship]]" ([http://www.amazon.com/Computer-worship-Ivor-Catt/dp/0273002430/ref=ntt_at_ep_dpi_2 Read in full])
* 1971 - "[[The Catt Concept: The New Industrial Darwinism]]" ([http://www.amazon.com/Catt-concept-new-industrial-Darwinism/dp/024610533X/ref=ntt_at_ep_dpt_1 Read in full])

==Media==

* 2011 - [http://www.worldsci.org/videos/dimdim/event_451_dimdim.flv Does Faraday Allow Superposition?] (Video Lecture)

==External links==
* [http://www.ivorcatt.co.uk/ Ivor Catt's website]
* [http://www.ivorcatt.org/ Ivor Catt's archive site, with 1970s books and articles]
* [http://www.ivorcatt.com/ Ivor Catt's earlier website]
* [http://www.ivorcatt.co.uk/cattq.htm The Catt Question] (animated statement of the question)
* [https://www.oliver-heaviside.com/ivor-catt/ Ivor Catt pages at oliver-heaviside.com]
* [https://archive.org/details/Crosstalk "Crosstalk (Noise) in Digital Systems", 1967] at the Internet Archive
* [https://archive.org/details/DeathOfElectricCurrent "Death of Electric Current", Wireless World, December 1980] at the Internet Archive

[[Category:Scientist|Catt Ivor]]
[[Category:Worldwide List of Dissident Scientists|Catt Ivor]]
[[Category:Electromagnetism|Catt Ivor]]
[[Category:Electrodynamics|Catt Ivor]]