Remember the post a while back where we tried to come up with a list of the 10 greatest physicists? I've been thinking and rearranging and I think I've come up with a list I'm reasonably happy with. There are quite a few great physicists I'm not happy at all about having to leave out, but 10 is a small number and no matter which ten are picked there's at least ten more who have some good cause to feel left out. The criteria is the importance of their contribution to physics, not just their raw brilliance.

To make up for those left out, I'm including a number of unordered Honorable Mentions who at least deserve to be in the top 20 but for one reason or another I decided that the others had a better case. I'm going to start out with two of those today, and the we'll start the Top 10 list proper later this week. We'll keep adding honorable mentions as we go, and over the next week or two we'll count down probably two at a time. Here we go:

Honorable Mention: **Galileo Galilei**

Galileo was at or near the top of numerous submitted lists. Why is he not on mine? If I were making a list of the greatest *scientists* of all time, he would be. He might even be at the top. But it's a list of greatest physicists, and in the modern sense he wasn't really one. He was a natural philosopher, largely because the mathematical nature of modern physics did not yet exist. Natural philosophy was the predecessor science to physics, and he brought it to its completion and ushered in the dawn of physics, though sunrise would have to wait until Newton. Galileo helped lay the foundation for physics, and for all of modern science. From an absolute revelation in our knowledge of astronomy to the invention of the telescope to the first tentative steps toward a theory of force and motion, modern science owes almost everything to the revolution he started. For that matter, his early experiments with the speed of light and his concept of Galilean relativity provided the framework that Maxwell, Lorentz, and Einstein corrected and revolutionized centuries later. If this is an honorable mention, it's about as honorable as it gets.

Honorable Mention: **Emmy Noether**

Emmy Noether is definitely top 10 material, but though it pains me I have to disqualify her on the grounds that she was best known as a mathematician. But her greatest achievement is one in mathematical physics, and it's about as important as mathematical physics achievements get. In 1915 she wrote down Noether's Theorem and started a new era in physics - one in which the basic symmetries of nature were intimately and mathematically connected to the very conservation laws which have stood unbroken since our exploration of physics began. Symmetry of the laws of physics with respect to time implies conservation of energy, symmetry with respect to space implies conservation of momentum, and a host of more subtle and profoundly powerful results.

That's leaving aside entirely the rest of her very substantial pure mathematics accomplishments. Her eponymous theorem by itself is more than enough by itself to ensure her a place with the greatest mathematicians. Einstein and Hilbert both spoke about her work in the highest possible terms, and their opinion counts far more than mine ever could. Like Galileo, "honorable" doesn't begin to cover it.

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Just want to point out that Noether's greatest accomplishment is arguable. If I had to pick one thing, it'd probably be that she pioneered the study of noncommutative rings. You know, things like algebras of operators in quantum mechanics. Of course, this is still restricting to the portion of her work that's relevant to physics. Though of course, I'm biased, being a math grad student who is working in an area where all the theorems at the beginning are hers or Hilbert's...

@Charles

Wouldn't those be the same thing just by looking at the phase space of the problem in question? By looking at the problems' phase space, you geometrically look at the Lagrangian or Hamiltonian. These can be commutative or not, but the geometry and algebra of the system is described by both sets of work. Right?

Justin, I'm not quite sure what you mean. What specifically are you saying can be commutative or not?

Noether's theorem re smooth Lie groups requires a continuous symmetry or at least approximation by a Taylor series for coupling to a conserved current (observable). Only external symmetries first order couple to translation and rotation. Physics (mechanics!) could be in a world of hurt if there were even one non-Noetherian discrete external symmetry that demanded a conserved observable.

There is. Do opposite parity mass distributions violate the Equivalence Principle?

http://www.mazepath.com/uncleal/lajos.htm#b5

symmetries-properties. Red bar and prior paragraph. Charge conjugation is an internal symmetry.

Charles,

The symmetry of the phase space may or may not be commutative. That is, the invariants of the space (group operations) may or may not commute. To take a finite example from quantum chemistry; if I have a cyclic molecule, my vibrational Hamiltonian should also be cyclic, thus commutative. If I have a icosahedral molecule I won't have a commutative Hamiltonian. Granted, the molecule and the phase space can look different, but for a simple case, they will at least have the same symmetry and group invariants.

Your nomination of Galileo for "greatest scientist" is puzzling. His contribution to the astronomical revolution was, after all, anything but scientific. He popularised heliocentricism, but added nothing of substance to it, and for him the pursuit of truth always took poor second place to the preservation of his pride. He deserves credit for his work in terrestrial dynamics, etc, but surely the black marks around his conduct in the heliocentric controversy take him out of the running for any "all time greatest" prize.

Ahh, you meant the symmetry group. Gotcha. That's still just noncommutative group theory, whereas Noether helped put together noncommutative RING theory, which includes the algebra of observables in quantum mechanics. Noncommutative group theory goes back a bit further, because there are virtually no spaces whose symmetry groups are commutative (including finite collections of points!). It's more like taking the collection of all functions on phase space under addition and multiplication. Classically, this is commutative, but in quantum mechanics, it's not.

Adrian: Galileo isn't being nominated here for "greatest" but for honorable mention after not being on the top 10.

Charles: I refer you to the sentence where Matt writes, "

If I were making a list of the greatest scientists of all time, he would be. He might even be at the top."Adrian: point conceded, I missed it when I read the post, focusing on Noether.

My eyes looked for Tesla in this post..

Galileo wouldn't actually be on the top of my greatest scientists list, I'm just saying he'd have a case. A lot of commenters in the nomination post though he should be, even if I don't completely agree. I think he'd definitely be on the top 10 scientists list somewhere, actual position to be determined.

Betul, we're just getting started. Tesla's not out of the running yet!

Great! Looking forward to reading him. He is one of the names that enlightened my dark moments in science, that's why I can't wait :)

I think the great Russian physicist, L.D. Landau clearly belongs on your list. While I realize that there are many names that one could pose for inclusion; Landau's strict accomplishments (Nobel), originality, impact on others, and exposition (his ten volume "course" is without peer) make him an obvious top ten - if not top five. I think living and working behind the iron curtain has hurt him generally; I note that all of your selections are of the political west.

where the hell is max Planck

Adrian: point conceded, I missed it when I read the post, focusing on Noether.