# Was annihilation considered in 1905?

The positron was discovered in 1932, did physicist have any knowledge or assumed that matter could be annihilated into energy at the start of XX century?

• Does "E = mc^2" count? which is to say, matter/energy conversion has a lot more avenues than antiparticles. Commented Aug 23, 2018 at 13:12
• Annihilation is a more specific concept than matter-to-energy conversion. The former requires antimatter, first theorised c. 1930 from the Dirac equation. But the fact that all exothermic reactions are due to converting mass to energy followed from special relativity in 1905. For example, chemicals undergo small changes in reactions. How much of a change are you looking for? Does chemistry count? Do nuclear reactions?
– J.G.
Commented Aug 23, 2018 at 18:50
• @CarlWitthoft,...such as? Commented Aug 24, 2018 at 5:49
• @J.G., The question means: before 1905 and relativity. What was knownbefore that date? Commented Aug 24, 2018 at 5:51
• Heat from a 'non chemical' source was known. See hsm.stackexchange.com/questions/7475/… Commented Aug 24, 2018 at 18:24

Let us consider the following info on developments prior to 1905.

• Before 1905 (The forthcoming of $$E = mc^2$$) 1881 J. J. Thompson proposed that a charged conductor in motion increases its mass by $$\frac{4}{15} e^2/a$$

• 1904 H. A. Lorentz proposed that $$m_L = m_0 (1 – v^2/c^2)^{-3/2}$$ based on deformable spherical charge.

• 1904 Hasenöhrl derived an apparent mass increase of a moving cavity containing electromagnetic energy E, obtaining $$m_e = \frac{8}{3} E/c^2$$.

• 1905 On Abraham’s suggestion, Hasenöhrl corrected this to $$m_e = \frac{4}{3} E/c^2$$

Based on the study of the historical development of concepts, one may deduce that the equation $$E = mc^2$$ would have been discovered by other physicists sooner or later. However, it is likely that Einstein merely accelerated the development. ref.- >https://files.eric.ed.gov/fulltext/EJ848449.pdf

our contention is that though annihilation of particles was not an acceptable concept prior to 1905 but other ways of energy conversion of mass was being attempted.

• @uhoh-many thanks for the editing..with MathJax it looks good...somehow I am not conversant with it..though its simple... Commented Sep 24, 2018 at 4:33
• @uhoh-thanks sir..i am 76 yr old and barely write with one finger..i will try.. Commented Sep 24, 2018 at 5:33
• well you certainly write some thoughtful and authoritative answers with that finger! I don't know if you like to drift to other SE sites, but I have a math history question that hasn't received enough attention so far: How has the definition of the complex logarithm evolved since Cotes (1682-1716)?
– uhoh
Commented Sep 24, 2018 at 6:30
• thanks ...basically, I am a nuclear physics person but have used maths as a tool-i will try to look up...my experience in using complex logarithm is very limited Commented Sep 24, 2018 at 8:36
• here's a tough one then: Has a nuclear “neutron halo” been measured directly? Anything other than “breaks easily”?
– uhoh
Commented Sep 24, 2018 at 8:46