Michael Nielsen: The Michelson-Morley experiment aimed to test ether theories, Einstein’s special relativity developed independently, and the complexity of scientific progress defies central authority | Dwarkesh

Einstein's special relativity emerged independently, challenging misconceptions about the Michelson-Morley experiment's influence.

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Add us on Google by Editorial Team Apr. 10, 2026

Key takeaways

• The Michelson-Morley experiment was initially aimed at testing ether theories, not influencing Einstein’s special relativity.
• Einstein’s theory of special relativity was developed independently of the Michelson-Morley experiment.
• The Michelson-Morley experiment aimed to detect ether by measuring light speed in different directions.
• The experiment did not definitively disprove ether but distinguished between different ether theories.
• Scientific theories like ether illustrate the complexity of falsification in science.
• Lorentz’s concept of local time aligns with experimental observations, supporting special relativity.
• Muon decay rates observed in experiments confirm predictions made by special relativity.
• Scientific progress is complex and not governed by a centralized authority.
• Great scientists can remain wrong even after the scientific community changes its consensus.
• Einstein’s understanding of length contraction was fundamentally kinematic, not dynamic.
• The process of scientific progress involves heuristics that are hard to articulate.
• Theories evolve through a complex interplay of experiments and ideas.
• The historical context of scientific experiments is crucial for understanding their impact.

Guest intro

Michael Nielsen is a Research Fellow at the Astera Institute focused on metascience, tools for thought, and programmable matter. He pioneered the field of quantum computation and co-authored the standard textbook on quantum computing with Isaac Chuang, which has been cited over 52,000 times and remains one of the most highly cited physics books of all time. Nielsen is also a founding figure in the modern open science movement and has extensively researched how scientific progress actually occurs, including collaborating with Patrick Collison on whether scientific progress is slowing down.

The Michelson-Morley experiment and its implications

• The experiment was designed to test theories of the ether, a medium once thought necessary for light propagation.

• What Michelson and Morley thought they were doing was they thought they were testing different theories of what was called the ether.

  — Michael Nielsen

• It aimed to detect the ether by measuring light speed changes as Earth moved through it.

• The idea was that the earth is passing through maybe this aether wind… and if it’s being passed back sort of in the opposite direction it’ll get slowed down a little bit.

  — Michael Nielsen

• The experiment did not definitively prove ether’s nonexistence but distinguished between ether theories.

• What you’re pointing out is actually was trying to distinguish between many different theories of ether.

  — Michael Nielsen

• The results challenged the ether theory but did not directly lead to special relativity.
• Understanding the historical context of ether theory is crucial for grasping its significance in physics.

Einstein’s theory of special relativity

• Einstein’s development of special relativity was independent of the Michelson-Morley experiment.

• It actually wasn’t dispositive for his thinking at all something else completely was going on.

  — Michael Nielsen

• Einstein viewed length contraction as a kinematic effect, not a dynamic one.

• He thinks that length contraction is a dynamical effect… it’s purely kinematics that actually space and time are different than what we thought.

  — Michael Nielsen

• Lorentz’s local time concept aligned with Einstein’s ideas, supporting the theory.
• The muon decay rates observed experimentally matched predictions of special relativity.

• The measured decay rates… match exactly what you expect from special relativity.

  — Michael Nielsen

• Special relativity redefined our understanding of space and time, moving beyond ether theories.

The complexity of scientific progress

• Scientific progress is not governed by a centralized authority or standard procedure.

• There’s progress even though it is hard to articulate the process by which happens the heuristics that are used.

  — Michael Nielsen

• Theories evolve through a complex interplay of experiments and ideas.
• Great scientists can remain wrong long after the scientific community changes its opinion.

• Great scientists can remain wrong for a very long time after the scientific community has broadly changed its opinion.

  — Michael Nielsen

• The process involves heuristics and individual journeys that may lag behind consensus.
• Understanding scientific progress requires recognizing its intricate and non-linear nature.
• The historical context of experiments is crucial for understanding their impact on theories.

Lorentz’s local time and experimental evidence

• Lorentz introduced the concept of local time as a mathematical convenience.

• Lorentz introduces this quantity called local time… it’s what Einstein would later just recognize as time in another inertial reference frame.

  — Michael Nielsen

• Local time aligns with physical reality observed in experiments with muons.
• The decay rates of muons observed in experiments support special relativity.

• They’re decaying way way way too slow… the measured decay rates in 1940… match exactly what you expect from special relativity.

  — Michael Nielsen

• Lorentz’s ideas provided a foundation for Einstein’s theory of special relativity.
• The alignment of experimental evidence with theoretical predictions reinforced the validity of special relativity.
• Understanding Lorentz’s contributions is essential for grasping the development of modern physics.

The role of experiments in scientific theories

• Experiments like Michelson-Morley illustrate the complexity of falsification in science.

• It’s not clear what is being falsified… certainly you can’t induce the theory of special relativity from the fact that one version of the ether seems to be disconfirmed by these experiments.

  — Michael Nielsen

• Experiments serve to distinguish between competing theories rather than provide definitive proof.
• The historical context of experiments is crucial for understanding their implications.
• Experiments are part of a broader process of theory evolution and validation.
• The interplay between experiments and theories drives scientific progress.
• Understanding the role of experiments helps in grasping the complexity of scientific inquiry.
• Experiments provide insights but are not the sole determinants of scientific theories.

The historical context of scientific theories

• The ether theory was a significant concept in the development of modern physics.
• Understanding its historical context is crucial for grasping its impact.
• The Michelson-Morley experiment was a pivotal moment in challenging ether theories.
• The evolution of scientific theories involves revisiting and reinterpreting past ideas.
• Historical context provides insights into the development and validation of theories.
• Theories like ether illustrate the complexity and non-linearity of scientific progress.
• Understanding history helps in recognizing the intricate dynamics of innovation.
• Historical context is essential for understanding the evolution of scientific thought.

The nature of scientific discovery

• Scientific discovery is a complex process involving heuristics and individual journeys.

• There’s progress even though it is hard to articulate the process by which happens the heuristics that are used.

  — Michael Nielsen

• Theories evolve through a complex interplay of experiments, ideas, and historical context.
• Discovery involves revisiting and reinterpreting past ideas and experiments.
• The process is not governed by a centralized authority or standard procedure.
• Understanding discovery requires recognizing its intricate and non-linear nature.
• The historical context of experiments is crucial for understanding their impact on discovery.
• Discovery is part of a broader process of theory evolution and validation.

The evolution of scientific theories

• Theories evolve through a complex interplay of experiments, ideas, and historical context.
• The process involves revisiting and reinterpreting past ideas and experiments.
• Theories like ether illustrate the complexity and non-linearity of scientific progress.
• Understanding evolution requires recognizing the intricate dynamics of innovation.
• The historical context of experiments is crucial for understanding their implications.
• Evolution involves distinguishing between competing theories rather than providing definitive proof.
• Theories evolve through a broader process of discovery and validation.
• Understanding evolution helps in grasping the complexity of scientific inquiry.

Disclosure: This article was edited by Editorial Team. For more information on how we create and review content, see our Editorial Policy.