> Einstein saw the whole forest, while Heaviside and Thomson were looking through a magnifying glass at the bark on a single tree.

That's an incorrect characterization.

Heaviside is pre-Michelson-Morley. Einstein is post.

The fact that "Ether doesn't exist. Electromagnetic waves simply transmit without a medium." is a VERY VERY VERY big change in the fundamentals of physics.

That opened the door for the hypothesis that "all physical laws look the same in all inertial frames" because without "Ether" you cannot anoint a preferred inertial frame. The Michelson-Morley experiment was the first test of that hypothesis.

And, to be fair, the kind of fields interpretation that Einstein championed has weaknesses:

1) It's an absolute bear to compute--the Heaviside-Hertz formulations lend themselves to engineering much better pre-computers.

2) It had severe experimental holes--at the time.

For example, the Einstein fields interpretation makes the prediction that an an excited electron in an atom will never decay. That, of course, was nonsense--excited atoms always decay to ground state. Except--now that we can isolate single atoms we absolutely see that single atoms don't decay--only the ensemble interactions cause them to decay.

> Heaviside is pre-Michelson-Morley

I just read the 1893 preface to his Electromagnetic theory vol 1 linked in another comment. It mentions the Michelson and other experiments and talks about how to accommodate them (in now-unfamiliar terms I don't understand).

Einstein didn’t know about the Michelson–Morley experiment.

That is, at best, an open question: http://adsabs.harvard.edu/full/1974Obs....94...81J

And, even if Einstein didn't know about it, people who read Einstein's paper did. That meant that Einstein's paper fell onto fertile soil rather than simply being a mathematical curiosity waiting to be discovered at a later time.

Oliver Heaviside is very often underrated and forgotten and he deserves not to be—even his reformulation of Maxwell's equations into the four that we know and commonly use today alone ought to have him receive better history/recognition in the textbooks. This is probably because he was an outsider to the physics and electrical engineering establishment and he wasn't known to make friends easily, and he didn't abide fools well.

Whilst CliffStoll's quote (and link) is from Paul J. Nahin's article in the Royal Society journal it's also worth highlighting the fact that Nahin has written a full bio on Heaviside (it's mentioned in the article's footnotes but might be overlooked). I have a copy of the book, it is excellent, it's likely the most comprehensive and authoritative written on Heaviside, and I'd thoroughly recommend it: Oliver Heaviside–The Life, Work, & Times of an Electrical Genius of the Victorian Age; Paul J. Nahin PJ ©1988-IEEE ©2002-John Hopkins Uni, ISBN 0-8018-6909-9 paperback ed.

It's all very well to praise Heaviside but if one really wants to get a feel for the extent and depth of his work then I refer one to the following works of his that are on the Internet Archive (they're out of copyright so they can be downloaded). Note, as with many works, the Internet Archive has multiple copies some of which are more readable (or better scanned) than others, so the seemingly multiple entries are not duplicates. Two other points to note, this list is not comprehensive and the IA's file-naming conventions are sometimes skewed or confusing (apologies if I've made any typos):

Electromagnetic Theory, Volume-1, Heaviside, Oliver, 1850-1925, 1893 edition: https://archive.org/details/electromagnetic00heavgoog

Electromagnetic Theory, Volume-1, Heaviside, Oliver, 1850-1925, 1894/1912 ed.: https://archive.org/details/electromagnetict01heavrich

Electromagnetic Theory, Volume-2, Heaviside, Oliver, 1850-1925, 1894/1912 ed.: https://archive.org/details/electromagnetict02heavrich

Electromagnetic Theory, Volume-3, Heaviside, Oliver, 1850-1925, 1893 ed.: https://archive.org/details/electromagnetict03heavuoft

Electrical Papers, Volume-1, Heaviside, Oliver, 1850-1925, 1892 ed.: https://archive.org/details/electricalpapers01heavuoft

Electrical Papers, Volume-2, Heaviside, Oliver, 1850-1925, 1894 ed.: https://archive.org/details/electricalpaper01heavgoog

Electrical Papers, Volume-2, Heaviside, Oliver, 1850-1925, 1894 ed.: https://archive.org/details/electricalpapers02heavrich

Electromagnetic Waves, Heaviside, Oliver, 1850-1925, 1889 ed.: https://archive.org/details/electromagnetic01heavgoog

An upvote to those who upvoted this, every bit shows that more people are becoming acquainted with Heaviside's works.

BTW, a factoid just occurred to me that some may not know, which is that the earth's ionosphere—those ionized layers ≈100-200km above ground that reflect radio waves—is called the Heaviside layer: https://en.wikipedia.org/wiki/Kennelly%E2%80%93Heaviside_lay....

...And now some trivia straight from the almost-completely-useless information dept: somewhat strangely, the Heaviside Layer features in the musical Cats. It's at the point where Macavity the Mystery Cat tries to escape to the Heaviside Layer: https://blog.sciencemuseum.org.uk/cats-and-the-heaviside-lay... https://www.themarysue.com/cats-heaviside-layer-real/

"Up, up, up past the Russell Hotel

Up, up, up, up to the Heaviside layer

Up, up, up past the Russell Hotel

Up, up, up, up to the Heaviside layer"

https://www.youtube.com/watch?v=pKH63cRJ3p4

Methinks, Heaviside would not have approved (but then, that's rather presumptuous of me).