1900: A physics genius wandering around Europe

Chapter 671 Uranium Nuclear Fission! A Shocking Blunder! Looking back suddenly, the transuranic energy was right there in the dim light!
In real history, the process from Fermi's discovery of transuranic elements to Hahn's proposal of uranium nuclear fission was a complex one.

In May 1934, Fermi bombarded uranium with neutrons and, through a process of elimination, discovered that transuranic elements might have been produced in the products.

This was an absolutely groundbreaking discovery at the time.

At that time, Fermi was already a leading figure in the field of physics, and he was rigorous in his scholarship, so he maintained a highly cautious attitude towards this discovery.

He plans to carefully check it several times before considering publication.

However, the "father" of the youth group, Italian Education Minister Corbino, was eager to make an announcement upon learning the news.

He had been paying close attention to Fermi's lab's achievements, and with such world-shaking academic results, he naturally wanted to publicize them extensively.

Colbino immediately announced Fermi's groundbreaking discovery at the Italian Academy of Sciences Congress, in front of the King and his ministers.

"Fermi has discovered a new element that goes beyond the periodic table!"

The news caused a sensation throughout the country.

Major Italian newspapers rushed to report on it:
"Under the wise leadership of the Fascist Party and the great leader Mussolini, Italy has regained its ancient glory."

"I suggest naming this new element after the leader!"

At that time, Fermi was still very naive, and he was very flustered.

He privately approached Colbino and explained that the results were not necessarily 100% accurate, and hoped that they would not be overhyped.

But Colbino, instead, comforted him:
"Young people should have confidence!"

With all the accolades he received, Fermi began to waver.

Based on his analysis of theoretical and experimental data, he concluded that the product should indeed be transuranium, even though he did not actually separate it.

So he stopped worrying about it.

Thus, with Italy's encouragement, news of Fermi's discovery of transuranic elements swept the world like a storm.

Shocked the world!

The scientific community was immediately in an uproar!

Transuranium, like magic, attracted all the experimental physicists of the time.

However, the scientific leaders were not as easily persuaded as the King of Italy.

Shortly after Fermi's paper was published, the first voice of doubt emerged.

In the same year, German physicist Heinrich Nordak publicly questioned Fermi's results.

This Nordak is no ordinary person either.

She and her husband discovered element 75, rhenium, in 1925 and were experts in the field of elements.

In his article "On Element 93", Nordak points out:

"When Fermi analyzed the reaction products, he only ruled out element 82, lead, and elements heavier than lead, but he did not rule out elements lighter than lead."

Therefore, it cannot be proven that the reaction product is transuranic.

"Unless all light elements are eliminated."

If we only consider this, Nordak isn't all that remarkable.

Fermi would retort: ​​I'd love to do that too! But I really can't.

At that time, the level of chemistry was relatively backward, and the work of separating elements was very complex and difficult.

Moreover, the amount of products generated by nuclear reactions is very small, which greatly increases the difficulty of detection.

The first 30 or so elements may be easy to separate, but the further you go, the more similar the properties of the elements become, making them extremely difficult to distinguish.

It can be said that there were not many chemists at that time who were able to master advanced separation technology.

However, Nordak also mentioned in the paper:

"Fermi may not have created transuranic elements, but rather fragments produced by uranium fission."

"It is conceivable that these fragments are isotopes of elements up to element number 92, rather than transuranic elements."

It can be said that Nordak had actually predicted the possibility of uranium heavy nucleus fission.

However, her paper was met with ridicule from the academic community.

On the one hand, she was a woman with a low status in academia, and she didn't even have the funding to obtain uranium to verify it herself.

On the other hand, thanks to Bohr's droplet model, no one at the time believed that a single neutron could break a uranium nucleus into several pieces.

In 1936, Nordak asked Hahn to endorse her, but the latter refused.

Hahn thought Nordak's views were absurd and that citing Nordak's views would make him a laughing stock in academia.

At that time, Hahn himself was also studying Fermi's transuranium element.

In fact, as early as two years ago, Meitner urged Hahn to repeat Fermi's experiment with her, and later the two found a chemist named Strassmann.

The three of them began their experiment with great enthusiasm.

Between 1934 and 1938, the trio discovered more than a dozen unknown isotopes.

They believe these are isotopes of transuranic elements.

Unfortunately, they still couldn't obtain the actual transuranic element, and were always missing a definitive piece of evidence.

Meitner then redesigned the experiment, while Hahn and Strassmann were responsible for improving the chemical aspects of the experiment.

During this period, the French couple, Irene and her husband, were also researching this topic.

In late 1937, after bombarding uranium with neutrons, Irene did not perform chemical separation but directly measured the reaction products.

Therefore, she discovered a new element that remained in the filtrate after the precipitation of transuranic elements and could be separated from uranium.

After further testing, Elena concluded that it was likely an isotope of element 90, thorium.

After the paper was published, the Hahn trio in Germany expressed strong skepticism about the results.

Because this would mean that a tiny neutron could actually knock an alpha particle out of a uranium nucleus, which is impossible!

They repeated the experiment, and sure enough, they did not find the so-called thorium isotopes.

So Hahn even wrote a letter himself, hoping that Elena would retract the article.

And at a meeting in Rome, he said to Jorio in a chauvinistic manner:
"I haven't publicly criticized your wife because she's a woman."

"But her result is definitely wrong."

When Jolio returned home, he relayed Hahn's opinion to Elena, who then berated him.

"Not only do you not speak up for me, but you also deliberately relay other people's words to me."

Jolio was heartbroken.

Elena completely disregarded Hahn's opinion and continued her experiment.

In May 1938, she published another paper.

This time, she actually discovered an isotope that "looks very much like element 57 [lanthanum]" in the products of neutron bombardment of uranium.

Elena was astonished.

Although she was very unhappy with Hahn, she also agreed with Bohr's theories.

A single neutron cannot cause a uranium nucleus to lose so many protons and neutrons to become element 57.

It's like trying to hit a watermelon with a sesame seed and expecting to end up with a bag of seeds—how is that possible?
So Elena made another mistake, believing it to be an "inexplicable" transuranium element.

Even though it had already been determined to be element 57, due to the inertia of thought, it was still leaning towards transuranic elements.

Bohr really did a lot of harm!
Regardless, Elena's experimental results cast a shadow over transuranic elements, leaving people puzzled.

By 1938, the political atmosphere in Germany and Italy had become increasingly tense.

In July of the same year, Meitner fled Germany to Sweden, and the trio officially disbanded.

In December of the same year, Fermi took his family north to Sweden, and with Bohr's help, escaped Italy and went to the United States under the pretext of receiving the Nobel Prize.

To add to this, Fermi received the Nobel Prize for the application of the neutron and the discovery of transuranium.

Even after Meitner left, Hahn did not give up his experiments on transuranium.

Moreover, he maintained contact with Meitner because he needed the latter's ability to analyze physical theories.

A month ago, he told others: I am not interested in what this lady (Irena) writes.

But now, he shamelessly began to carefully read Elena's articles.

Because more and more experimental results show that the truth about transuranium is not so simple.

In October 1938, after repeating Irene's experiment, Hahn discovered an isotope of element 88, radium, in the product.

This is how he explained it:

"When uranium-238 is bombarded with neutrons, it first releases an alpha particle and transforms into element 90, thorium-235."

"Thorium-235 then emitted an alpha particle and became radium-231."

It can be seen that Hahn had by this time accepted Irena's experimental results: neutrons can indeed knock out alpha particle fragments from atomic nuclei.

However, he still believes that the claim that the product contains lanthanum is nonsense.

In November of the same year, he published his paper.

He then went to Copenhagen, Denmark, to attend a conference. Upon hearing his findings, Bohr immediately expressed his opposition.

Meitner, who was in Sweden at the time, also expressed disbelief after seeing Hahn's paper. She urged him to conduct experiments as soon as possible to confirm it.

So after Hahn returned to Germany from Denmark, he continued his experiments.

In December, his experiment made a breakthrough!
Hahn discovered three more unknown isotopes that could be separated from other elements, but not from barium.

In chemistry, this means that these three isotopes are very likely isotopes of element 56 [barium].

That's incredible.

Hahn encountered the same predicament as Elena had faced.

Uranium, element number 92, can surprisingly generate barium, element number 56, which has a significantly different atomic number!

This overturned Bohr's droplet model.

On December 19, Hahn wrote to Meitner informing him of the experimental results.

Two days later, through further verification, he completely confirmed that the mysterious isotope was indeed an isotope of barium!

Therefore, the lanthanum element that Elena discovered also exists, because barium atoms can transform into lanthanum through beta decay.

At this point, Hahn was convinced that neutron bombardment of uranium nuclei would produce barium, which would then decay into lanthanum.

This phenomenon, which is impossible in physics, has now happened.

He feared that Elena would realize what was happening and try to publish the paper first, so he stopped writing to Meitner to discuss it.

On December 23, Meitner's nephew, Frisch, came to Sweden to visit his aunt.

Meitner then showed him Hahn's letter, and the two decided to consider the possibility of uranium nuclear fission.

At this time, Frisch was studying under Bohr at the Bohr Institute, and he was very familiar with the droplet model.

With his help, the aunt and niece worked together to calculate the problem theoretically.

Finally, as mentioned in the previous chapter, Meitner proved that uranium nuclear fission is theoretically feasible.

Hahn and Elena's experimental results were correct; the uranium nucleus did indeed split!

Fermi's claim about transuranic elements is entirely fictitious; they are merely fragments resulting from fission!

Frisch immediately rushed back to Denmark to discuss the matter with Bohr.

Upon hearing this theory, Bohr slapped his forehead and laughed:

"How could I be so stupid!"

Meitner, on the other hand, couldn't wait to write to Hahn to tell him the good news and to ask him not to rush into writing the paper, but to try to incorporate the theory.

Unfortunately, this time, she never received a reply.

On January 6, 1939, the paper co-authored by Hahn and Strassmann was published.

The two researchers experimentally confirmed that neutron bombardment of uranium can produce barium.

The next day, the paper arrived in Denmark. After reading it, Frisch had no time to defend his aunt.

Because Hahn only discovered this phenomenon experimentally, but did not prove it theoretically.

He wants to publish a paper that will theoretically confirm the existence of uranium fission.

After completing his paper, Frisch even used a cloud chamber to track the fragmentation fragments, proving in the most intuitive way that neutron bombardment of uranium nuclei did indeed cause fission.

On February 11, Frisch and Meitner co-authored a theoretical article published in Nature.

In the paper, Frisch first used the term "fission".

On February 18, Frisch's paper, published under his sole authorship, on observing nuclear fission using a cloud chamber, was then published.

After the paper was published, the relationship between Meitner and Hahn officially broke down.

After they read each other's papers, I wonder what their thoughts were.

The words are divided into two parts.

Just after Hahn published his paper and before Frisch published his.

On January 7, Bohr was invited to the United States to attend a physics conference.

Before boarding the ship, Frisch handed the first draft of his paper to Bohr, whom he greatly respected and hoped would give it a final review.

Another physicist who accompanied Bohr at the time was Rosenfeld.

The journey was long, so Bohr discussed Frisch's paper with his partner, who was shocked after hearing it!
"Uranium nuclei can undergo nuclear fission?"

"Doesn't this mean that Fermi's transuranic element was wrong, and the Nobel Prize made a huge blunder?"

Bohr was probably too tired; he forgot to tell Rosenfeld to keep it a secret because Frisch's paper had not yet been formally published.

On January 16, Bohr arrived in New York, where he was personally greeted by Fermi and a large group of physicists. (At this time, Fermi had only been in the United States for a short period of time.)

Bohr was very professional and did not spread the news of uranium nuclear fission.

However, that evening, Rosenfield was dragged by his friend Wheeler to Princeton to attend a physics club meeting.

At the meeting, Rosenfeld recounted his discussions with Bohr about uranium nuclear fission.

Actually, you can't blame him, because he didn't know Frisch's specific situation either.

His words immediately shocked all the physicists present!
This is absolutely groundbreaking news that will shock the academic community.

The next day, Bohr arrived in Princeton and was shocked to hear the news.

He quickly wrote an article, publicly stating that the theoretical explanation of uranium nuclear fission was thanks to Meitner and Frisch.

Immediately afterwards, he wrote to Frisch: send the paper to Nature magazine for publication as soon as possible.

However, he did not receive a reply from Frisch.

On January 20, Fermi learned about uranium nuclear fission from his friends Rabbi (Chapter 552), Lamb, and others.

At this point, Fermi realized he was wrong; there was no transuranium element.

However, just a month ago, he gave a public speech about transuranic elements.
Fermi felt a mix of emotions.

However, no one looked down on Fermi because of this, or thought he didn't deserve the Nobel Prize.

After all, the four-fermion theory alone was enough to establish his status as a leading figure, not to mention other theories such as neutron bombardment.

At the same time, news of uranium nuclear fission began to spread rapidly.

On January 26, the Fifth Washington Conference on Theoretical Physics urgently invited two leading figures, Bohr and Fermi.

The original topic of the conference was low-temperature physics.

However, as news of uranium nuclear fission spread, the meeting was in complete chaos.

No one is discussing low-temperature physics anymore; all physicists are discussing uranium nuclear fission.

At the meeting, Bohr once again emphasized Hahn's experiments and Frisch's theoretical explanation.

He knew he couldn't stop others from conducting experiments, but he needed to protect Free and Meitner's priority. (Hahn's paper had already been published by this time, so it didn't matter.)
Bohr was indeed a man of impeccable character!
While the meeting was being held, more than a dozen American universities and research institutes, including Columbia University and Caltech, had already begun experiments.

On January 28, someone announced that the phenomenon of uranium nuclear fission had been confirmed.

Subsequently, more physicists proved this result.

Furthermore, it was determined that the uranium that underwent nuclear fission was not uranium-238, but rather the rarer uranium-235.

When the news reached the University of California, Berkeley on the West Coast of the United States, Oppenheimer immediately expressed disbelief.

However, his laboratory immediately confirmed the result.

After staring at the fragmented remains and remaining silent for three minutes, Oppenheimer came to believe in uranium nuclear fission.

On February 7, Bohr published another article in which he explained in detail the origins and development of uranium nuclear fission and advocated for the rights of the aunt and nephew.

Thus, the question of the attribution of uranium nuclear fission came to an end, but research on it only intensified.

All experimental physicists devoted themselves to uranium nuclear fission.

In mid-February, Hahn published his second paper, predicting that uranium nuclear fission would release neutrons along with the nuclear fusion process.

In March, Elena proved through experiments that uranium-235 fission releases more than two neutrons.

These neutrons will then bombard other uranium nuclei, continuing in a snowballing manner to form a chain reaction and release enormous energy.

After reading the paper, Oppenheimer took only a few minutes to think about the possibility of making weapons.

A week later, sketches of a weapon (the atomic bomb) appeared on the blackboard in his office.

At that time, it was just scientists conducting research spontaneously with a scientific attitude; the authorities were unaware of the importance of uranium nuclear fission.

But soon, the truth could no longer be hidden.

The United States, the Soviet Union, the United Kingdom, France, Germany, Italy, and the Sakura Empire, among other powerful nations, officially launched their atomic bomb programs.

A new scientific race has begun!
And in this grand drama about uranium nuclear fission, the most dramatic part is:

In May 1940, McMillan and Abelsen of the University of California, Berkeley, actually found transuranic element 93 in the reaction products of neutron bombardment of uranium, and named it neptunium.

The two were awarded the Nobel Prize in Chemistry in 1951 for this.

Some might wonder: "Why could only these two do the same experiment, and not others?"

Because the two used a cyclotron to accelerate neutrons for their experiments, they were able to precisely control the speed of the neutrons.

(End of this chapter)