Alpher, Bethe, Gamow. Samuel L. Marateck. ([email protected]) New York University, New York City, US. PDF Full Text. In fact, Bethe played no part in writing the paper, but he was happy for Gamow to include his name for Gamow’s little joke. In this paper, Gamow and Alpher. Ralph Alpher had just finished his PhD on the origin of the elements, and after the publication of the famous Alpher, Bethe, Gamow paper (see my blog here.
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Last week I reposted my blog about the prediction of alphsr cosmic microwave background CMBwhich I had originally written in April This month, July, marks the 50th anniversary of the first detection of the CMB, and I will blog about that historic discovery next week. In doing my research, I alphee out that many of the things I had been been told or had read about the prediction were wrong, so here I wanted to say a little bit more about what led up to the prediction.
Many people either do not know of the s prediction of the CMB, or they attribute its prediction to George Gamow. In fact, it was his research assistants Ralph Alpher and Robert Hermann who made the prediction, but as head of the group it is often Gamow who gets the credit. Ralph Alpher had just finished his PhD on the origin of the elements, and after the publication of the famous Alpher, Bethe, Gamow paper see my blog here about thatGamow started writing a series of papers on the nature of the early Universe.
Although a man of huge intellect and inventiveness, Gamow was often sloppy on mathematical detail. The letter is dated 25 October It appeared in Nature magazine on the 13th of November Naturevolumepages — here is a link to the paper. Here is the paper in its entirety it is short! The original paper letter by Alphr and Hermann which makes the first prediction of the cosmic microwave background CMB.
It was published in Nature magazine on the 13th of November Next week, I will blog about the accidental discovery of the CMB by Penzias and Wilson, which was published 50 years ago to this month July.
Today I am going to blog about the first fact. Jupiter is, like the Sun, mainly comprised of hydrogen and helium. It was George Gamow and his co-workes Ralph Alpher and Robert Hermann who showed in the late s that the hydrogen and helium we find in the Universe was all be created in the first few minutes after the Big Bang.
The other elements beyond hydrogen and helium have all been created within stars. Because hydrogen is converted into helium in stars, the abundance of helium is very slowly getting greater in the Universe, and the abundance of hydrogen is very slowly going down. When these clouds are massive and cold enough they can collapse under their own gravity, and as they do so they fragment.
This requires a high enough pressure and density and temperature at the core of the fragment. Jupiter has all the ingredients to be a star, but what it lacks is the mass or size. It is too small to create a high enough temperature and pressure at the centre to force hydrogen to fuse into helium.
Larger than this and they are beyond something called the Hyashi limit, and will just blow themselves apart before they can settle down onto the main papfr. It was discovered in the s, from observing Jupiter in the infrared, that it was hotter than it should be given its distance from the Sun.
This is because the gravitational potential energy lost when the gas from which it formed collapsed was converted to heat, and this heat has been leaking out over since. It emits about twice the energy that it gets gajow the Sun. One papsr the outstanding problems in astrophysics in the s was how were the elements created.
In the s it was realised by Cecilia Payne-Gaposchkin in her PhD work that the Sun was mainly composed of hydrogen. Then, spectral alpjer of others stars and the gases of the interstellar medium led astrophycisits to realise that the Universe was composed mainly of hydrogen aboutwith the remainder being helium aboutand only or so being all the other elements oxygen, nitrogen, carbon etc. In the mid s Russian-American physicist George Gamow started thinking about how the elements originated, and he developed a theory with his student Ralph Alpher that they were all created in the early Universe when, he argued, it would have been hotter and denser gzmow it currently is.
In this paper, Gamow and Alpher argued that all the elements were created in the early Universe.
However, when others went through the details it was realised that the numbers did not add up, the Universe expanded and cooled too quickly for all the elements to be created in this way. Although it was possible for hydrogen and helium to be created in the first few minutes of the Universe, by the time the Universe was a few minutes old it had become too cool and the density too low to form the heavier elements beyond helium. Part of the reason for heavier elements not being built up in these first few minutes was due to something called the deuterium bottleneckwhich I will explain in a future blog.
In the s an alternative theory for the origin of the elements was put forward by Fred Hoyle and his collaborators Willy Fowler and Geoffrey and Margaret Burbidge. Hoyle was the main advocate of a theory called the Steady State Theory which he had first proposed in This was alpber competing theory to the hot big bang theory, and so of course Hoyle did not believe any elements had been formed in a hot, dense early Universe as he did not believe such a Universe ever existed.
The first page of Burbidge teal. Although it could explain the creation of elements beyond helium, it was not possible to create enough helium in stars to account for the approximately found to be present in the Universe today.
In part 2 of this blog, I will explain what our current understanding is of the origin of the elements in the proportions we observe in the Universe, and what the deuterium bottleneck is and why it is important. In this blog I described the first results from the Planck satellite, which is studying the Alpheer Microwave Background in greater detail than we have ever done before.
But, what exactly is the Cosmic Microwave Background? Where does it come from? How was it produced? In Behe Hubble published evidence that the speed with which galaxies were moving away from the Milky Way was directly related to their distance from us. Although Hubble himself never explicity stated it, this is clear evidence that the Universe is expanding. If the Universe is expanding, then of course one would expect it to have been smaller in the past.
In the s the Russian-American physicist George Gamow started thinking about what the early Universe would have been like. He worked on two related theories, the first that the elements would have been created in the early Universe. The second related to the fact that a smaller, denser Universe would also have been hotter in the past. Although alper Alpher, Bethe, Gamow paper was groundbreaking, it was wrong in some of its details.
It suggested that all the elements were created in the hot, early Universe. We now think know? Only hydrogen and helium were created in the early Universe, the other elements have all been created inside stars, something Pper Fred Hoyle worked out with co-workers in the s.
Alpher–Bethe–Gamow paper – Wikipedia
In a related paper, Alpher and Robert Herman, who was working as a post-doctoral research assistant for Gamow, calculated that the early Universe would have been a hot opaque plasma ionised gasand would thus have radiated like a black body. However, this radiation would not have been able to travel through the plasma as the photons would scatter of the free brthe.
The abstract of the paper by Alpher and Herman, gakow predicts a cosmic microwave background at a temperature of 5K 5 degrees above absolute zero. But, as the Universe expanded and cooled the bfthe would become a neutral gas, in that the electrons would combine with the nuclei to produce neutral atoms, allowing the photons to travel unimpeded.
They calculated that these photons, which would be able to thence travel unimpeded, would now be at a characteristic black-body temperature of 5K due to the expansion of the Universe. This in the microwave part of the spectrum, hence the name Cosmic Microwave Background. Our current understanding is pretty much what was derived in this paper, with a few refinements. This is when the fog of the early Universe lifted and is the earliest radiation we can see. The book can be found on the Springer website hereand on psper Amazon website here.
Create a free website or blog at WordPress. Five top facts about Jupiter — no. The list of the five alpehr.
The origin of the elements In Edwin Hubble published evidence that the speed with which galaxies were moving away from the Milky Way was directly related to their distance from us.
Origin of the Elements | thecuriousastronomer