At breakfast time I was sitting by the house at Vanavara Trading Post [65 kilometres/40 miles south of the explosion], facing north. [..] I suddenly saw that directly to the north, over Onkoul's Tunguska Road, the sky split in two and fire appeared high and wide over the forest [as Semenov showed, about 50 degrees up—expedition note]. The split in the sky grew larger, and the entire northern side was covered with fire. At that moment I became so hot that I couldn't bear it, as if my shirt was on fire; from the northern side, where the fire was, came strong heat. I wanted to tear off my shirt and throw it down, but then the sky shut closed, and a strong thump sounded, and I was thrown a few metres. I lost my senses for a moment, but then my wife ran out and led me to the house. After that such noise came, as if rocks were falling or cannons were firing, the earth shook, and when I was on the ground, I pressed my head down, fearing rocks would smash it. When the sky opened up, hot wind raced between the houses, like from cannons, which left traces in the ground like pathways, and it damaged some crops. Later we saw that many windows were shattered, and in the barn a part of the iron lock snapped.
As he began the slow and painstaking process of lowering the tamper, one of his colleagues, Raemer Schreiber, turned away to focus on other work, expecting that the experiment would be uninteresting until several more moments had passed. But suddenly he heard a sound behind him: Slotin’s screwdriver had slipped, and the tamper had dropped fully over the core. When Schreiber turned around, he saw a flash of blue light and felt a wave of heat on his face. A week later, he wrote a report on the mishap:
The blue flash was clearly visible in the room although it (the room) was well illuminated from the windows and possibly the overhead lights. . . . The total duration of the flash could not have been more than a few tenths of a second. Slotin reacted very quickly in flipping the tamper piece off. The time was about 3:00 p.m.
A guard who was stationed in the room to keep an eye on the precious plutonium had little knowledge of what Slotin was doing. But when the core started to glow and people started yelling, he promptly ran out the door and up a nearby hill. Subsequent calculations put the total number of fission reactions at about three quadrillion—a million times smaller than the first atomic bombs, but still enough to send out a significant burst of radioactivity. This radioactivity excited the electrons in the air, which, as they slipped back into an unexcited state, emitted high-energy photons—the blue flash.
General relativity tells us that as you get closer to a mass clocks run a bit more slowly. The effect can be observed on Earth with precise clocks at different distances from the center of the Earth and is pronounced enough that you have to correct for it to get the precise timing signals from GPS satellites right.
It follows that time runs more slowly at the center of a mass like the Earth. Apparently Feynman mentioned that, over the life of the Earth, the center of the Earth would be a day or two younger than its surface. The calculation is quite easy and one might expect it assigned as an undergrad physics problem.
It turns out that when you do a back of the envelop calculation you get about a year and a half. Feynman may have made a simple mistake or perhaps he was incorrectly quoted - apparently he never wrote the result down. I was unaware of his result, but I would have probably accepted it even though I had worked it out for distances from the earth (tall buildings, mountains, orbiting satellites).
The paper paper works out the result at the level of an undergrad physics class.
The young center of the Earth
U.I. Uggerhøj,1 R.E. Mikkelsen,1 and J. Faye2
1Department of Physics and Astronomy, Aarhus University, Denmark 2Department of Media, Cognition and Communication, University of Copenhagen, Denmark (Dated: April 20, 2016)
We treat, as an illustrative example of gravitational time dilation in relativity, the observation that the center of the Earth is younger than the surface by an appreciable amount. Richard Feynman first made this insightful point and presented an estimate of the size of the effect in a talk; a transcription was later published in which the time difference is quoted as ’one or two days’. However, a back- of-the-envelope calculation shows that the result is in fact a few years. In this paper we present this estimate alongside a more elaborate analysis yielding a difference of two and a half years. The aim is to provide a fairly complete solution to the relativity of the ’aging’ of an object due to differences in the gravitational potential. This solution - accessible at the undergraduate level - can be used for educational purposes, as an example in the classroom. Finally, we also briefly discuss why exchanging ’years’ for ’days’ - which in retrospect is a quite simple, but significant, mistake - has been repeated seemingly uncritically, albeit in a few cases only. The pedagogical value of this discussion is to show students that any number or observation, no matter who brought it forward, must be critically examined.
At the turn of the nineteenth century, Aaron Burr, who would later become the third Vice-President of the United States, secured a charter and millions of dollars in financing to establish the Manhattan Company, which promised to tap clean drinking water for New York City. Instead, Burr and his associates cut costs by drawing water from a putrid pond just south of what is now Canal Street and redirected the remaining money to found a bank (now called JPMorgan Chase). The city’s contaminated water supply contributed to two major outbreaks of cholera, a disease that causes vomiting, diarrhea, and dehydration so extreme that patients can lose ten per cent of their body weight in less than a day.
The audience of THE HUXLEY FILE, then, is educated people of whatever culture (THH was translated into Chinese and Japanese, as well as into European languages Hungarian, Russian, Italian, German, French, Spanish, and Italian), especially high school and college teachers who can select and present for their students sections from THE HUXLEY FILE to enrich, liberalize, and vitalize courses in at least these fields: (1) education, (2) biology, (3) anthropology, (4) philosophy, (5) religion, (6) social studies, and (7) style. Though these categories are designed to help understand Huxley's contributions, it's important to note that he was not a strict disciplinarian–a river of text, essay or letter, could and often did flow with relevant material on all of these and other tributaries as well. Huxley's popularization adventures resulted in what he called "fugitive pieces," many of them written when he was assailed by insomnia, and most of them constituting Collected Essays ; but since he was a professional biologist, an ample supply of his Scientific Memoirs is offered, though most of those pieces would not be understood or appreciated by most of us lay people.