Hundred years ago, Satyendra Nath Bose changed physics forever

Hundred years ago, Satyendra Nath Bose changed physics forever

Subject: Science and tech

Section: Space tech 

Introduction :

• A fractured, disjointed picture of a new ‘quantum theory’ was emerging in the middle of the biggest upheaval in physics during 1924 .
• This year marks 100 years of Bose’s discovery.
• Bose was born in Calcutta (now Kolkata) in 1894 having mathematical prowess and studied Physics at Presidency College and met another brilliant man Meghnad Saha
• Bose and Saha were appointed as faculty members in Rajabazar Science College.
• At that time physics was changing rapidly and Einstein gave new space and time understanding with theory of relativity.
• The work of Max Planck, Niels Bohr and Einstein had shown that the old physics was incapable of dealing with the microscopic world — the world inside atoms.
• Bose and Saha were teachers of new physics but a challenging period as all the important papers were in German. But this was not a roadblock for them and both became early adapters and together they published the first English translation of Einstein’s papers on general relativity.
• Both of them immersed fully to fine a way out .
• Bose’s now became lecturer in Dhaka University and topic was Planck’s law of black-body radiation.
• Bose could not explain it to students to his satisfaction.

Planck’s law

• Planck’s law, named after Max Planck, founded in 1900.
• It describes the pattern that told physicists physics worked differently in the microscopic.
• It is also probably the most successful guess in the history of physics.
• Planck’s law is about radiation. All hot objects — from a bowl of hot soup to the Sun — emit radiation in a range of frequencies.
• Physicists typically simplify them to an ideal: as objects that can emit light but not reflect it, a.k.a. black bodies.

Earlier attempt by Planck:

Planck looked closely at the data and simply guessed the right formula. It worked like magic. The only problem: it violated the rules of physics.

Origin of idea:

• Just like matter is a collection of discrete atoms, energy too had to be a collection of discrete packets or ‘quanta’. This idea was the birthplace of quantum mechanics.
• Planck’s law was correct, but its derivation was not as it didn’t stand scrutiny. It had to wait until Bose.

Issues involved:

Several attempts to derive Planck’s law suffered from conceptual issue as results from both quantum physics and pre-quantum (or classical) physics was used, thus logically inconsistent.

Planck derivation:

Planck’s own original derivation was based on a model of the black body based on radiation mechanism and classical physics had part of it.

Earlier established theories:

• Einstein had explained the photoelectric effect using the hypothesis that light carries energies in packets.
• The American physicist Arthur Compton had demonstrated that light carries discrete units of momentum.

Issue solved by Bose derivation:

• According to Bose, Planck’s law was independent of the mechanism that produced it.
• Bose synthesized Einstein and Compton hypothesis and eliminated classical physics, thus stripped off essence of problem .
• Bose found the most probable way of distributing energy among quanta of radiation.
• Planck’s law was therefore simply a statistical property of the quanta of radiation, a.k.a. photons.
• The most important result implicit is that total number of photons is not conserved- photons could appear out of thin air and disappear into nothingnes

Bose’s paper pioneered the field of quantum statistics.

• The British physicist Paul Dirac while finalizing quantum theory obtained Bose’s statistics that fundamental particles can be in one of two categories depending on their statistics (i.e. the set of rules to describe them properly): bosons or fermions.
• Bosons : Bosons are the fundamental particles that have spin in integer values (0, 1, 2, etc.).
• Fermions: These have spin in odd half integer values (1/2, 3/2, and 5/2, but not 2/2 or 6/2).

Evaluation of Bose :

• The lecturer, Satyendra Nath Bose, had discovered the correct set of equations to use to work out the behaviour of collections of photons (particles of light).
• A paper from Bose was initially rejected by a journal and Bose mailed paper to Albert Einstein and Einstein loved the paper, translated it to German and sent it to a journal himself.
• Despite a long career in physics, Bose published sparsely and never produced another work of similar value.
• He once described himself as a comet that only came once and never returned. For a comet as bright, though, once can be quite enough.