Why Planck's Formula For Black Body Radiation Is Used To Measure The Cbr?

[exchemist]

I have no problem with any of this.

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I do have a simple question, that maybe someone can answer. 

 

If the CBR is more or less uniform, across the universe at 2.75kelvin, and it has no spikes, allowing predictions to be made ref red shift and distance.

 

How can the depth of the radiation be measured?  

 

Why apply red shift to it other than to support the Big Bang theory, and show the universe was hotter 14billion years ago? There are no spikes indicating red shift.  

 

The CBR was claimed as a relic of particle creation from the Big Bang. Why didn't Hoyle claim it as proof for continual particle creation in the universe?

I can't quite follow what you mean by the "depth" of the radiation. Can you elaborate?

 

As for red shift, the radiation profile (i.e. its intensity as a function of frequency or wavelength) is the same as would be emitted by a black body at 2.7K. Red shift comes into it if one considers the observed expansion of the universe, which we get from red shifts that can be calculated by emissions lines from atoms. Applying that presumed expansion to the CMBR, one gets the result that it would have come from a hot plasma condensing at a certain temperature, in smaller universe. Which is a clean and simple explanation for it. 

 

You are right that there are no emission lines of atoms in the CMBR itself which one can assign and show to be redshifted by a certain amount. (If there were, it would not be black body radiation.) But how would one explain black body radiation, coming equally from every point in the sky, and corresponding to a temperature less than 3 degrees above absolute zero, as due to some matter creation process? What process would that be and why would it produce this ultra-cold radiation?  How could it be "proof" of anything like that?  

Edited May 18, 2019 by exchemist

[exchemist]

Re depth, every way we look there is radiation, there is no way as far as I can see of determining if it is uniformly distributed in the direction we look. For example the anisotropy shown in the Cobe/Planck results viewed from a different galaxy might allow particular hot spots in the CBR to be pinpointed at a particular distance in the direction we are looking in space. If two satellites were separated by a large distance then a depth measurement might be attainable. As I understand it, this is not the case, so there is no way of determining depth, unless maybe a single satellite has a very large orbit, and takes shots from different view points.

 

The CBR has no spike so no red shift can be reliably associated with it, unlike galaxies. Galaxies exhibit red and blue shift, so allowing speeds to be calculated, the luminosity of the stars allow distance calculations. Applying the BB theory and then ascribing a red shift to the CBR, and claiming this as proof of the BB, strikes me as a being a little bit dodgy. 

 

There are other theories that might explain black body. Black Body radiation is not unlike theoretical Hawking Radiation from a 4 dimensional Black Hole. I think it was Popolawski that theorizes we live in a 5 dimensional universe inside a black hole, would a five dimensional black hole not also have something like Hawking radiation?  

 

Perhaps the theoretical big bang lasting fractions of a second violating the known laws of physics, might be overstretching the maths a bit, and not testable. I have an open mind on the subject. For instance would space and the CBR not look exactly the same, if localized inflationary stages, produced particles continuously for a few  billion years. We know particles can spontaneously appear out of a vacuum, is this not similar to particle creation in the Big Bang, just a bit slower. If virtual particles are separated, they become more like real particles the longer they exist. An inflation of space between a pair of virtual particles with the correct properties MIGHT produce real particles, which MIGHT give of random amounts of radiation as they become stable particles. Not unlike Hawking radiation perhaps, which will never be detectable with all the other radiation around a black hole!     

BB radiation, from all over the sky, at <3K? Come on! You're just waving your hands. You have no mechanism to propose that would give that outcome. 

 

Nobody claims the CMBR is "proof" of anything. Nothing ever is, where a scientific theory is concerned. But, given the observed expansion of the universe, as seen by the cosmological red shift, the CMBR at <3K does exactly fit the idea of a plasma universe at an earlier stage. So for now at least, that explanation of it wins. 

 

It seems to me that so-called dark matter and the placeholder known as "dark energy" are the real mysteries. If anything is going to come along and overturn current cosmology it will probably come from them.

Edited May 18, 2019 by exchemist

[Dubbelosix]

I'll be sticking up for exchemist at the moment, since there is no proof concerning CMBR, it is called an evidence. Albeit, many consider it a strong evidence, but to call it a proof is too strong a terminology.

[exchemist]

Yes they do, The CBR is claimed as proof of the Big Bang. The CBR measurements is what swung the argument to the BB away from the Steady State expanding universe.

 

Galaxies are mostly red shifted, giving concrete evidence for galaxies moving away from us, and possible expansion of space, driving the movement. Conversely by the same argument, some are blue shifted which in a few billion years time, when all the red shifted galaxies have disappeared over the visible horizon, might lead someone to believe the universe is contracting.

 

There appears to be no way separating a CBR measurement at the edge of the visible universe from a CBR measurement taken locally. The CBR measurements appear not to have a distance associated with them. For example the CBR at the edge of the visible universe could be significantly less than 2.75K whilst that measured locally is measured at 2.75K, how are the signals separated? 

 

How are measurements of the CBR made indicating what distance the measurement is made at, allowing a red shift to be ascribed to those CBR measurements at that distance. ?? 

Citation please? I will be very surprised if the word "proof" appears in any scientific description of the findings or their significance. 

 

 

It is meaningless to talk of a CMBR signal "from" anywhere. It is all around. That is the point.

[exchemist]

Big Bang can be called hand waving, it was rescued via the appended inflationary stage, of Guth and later Linde when it was realized the CBR was not as smooth as predicted by Guth. A Hot Big Bang and particle creation is theory, and not testable in the lab.

 

Particles do appear out of the vacuum slowly, and is testable in the lab. If a method of particle creation is testable it is plausible, is it not ?. 

And how does that account for black body radiation, at <3K,  all over sky?

[OceanBreeze]

This was funny! :lol:

 

We both posted a reply almost simultaneously!

 

 

It isn’t funny at all, you and Flummoxed are both wrong!

 

Exchemist is right – there is no concept of “proof” in physics, and in fact, the word does not appear anywhere in your reference.

 

Not even the part you highlighted in Red, which only states: “The results confirmed the Big Bang theory of the origin of the universe”

 

The word “confirmed” means to strengthen; in this case, it strengthens the Big Bang Theory; it does not prove it. It is still a theory!

 

And your strawman argument about NASA being nobody, which Exchemist did not imply in any way, is transparently disingenuious.

 

The object of discussion here is to exchange ideas with the hope that everyone comes out of the discussion with maybe a bit more knowledge than they had before going in.

 

Your idea seems to be that you must “win” an argument by making unfounded assertions, using bold red font, to focus attention, but almost all of what you have posted In this thread, as well as several others, is flat out wrong.

 

Try listening to what the other person is saying and reading for comprehension, rather than simply looking for arguing points that seem to support your pre-conceived notions, and you will get a lot more benefit out of this forum.

[OceanBreeze]

Ive read that before  :shocked:

 

Apparently it didn't "stick".

 

Why did you write: "The CBR is claimed as proof of the Big Bang"?

[exchemist]

Stop talking about things that you don't understand and go to learn from the primary sources of CMB or CBR relevance, instead.

Maybe you'll learn WHY hundred of millions of USD were invested on this fundamental research in the last 30 years.

 

This link is one where you can start to learn a little bit about CMB, instead of going around spreading nonsenses.

Be humble and admit that you are sustaining your assertions without any validation from primary sources. Here is one:

 

COBE - NASA Science Mission Directorate (and this is what I call a primary source)

 

https://science.nasa.gov/missions/cobe

 

COBE

 

 

 

The purpose of the Cosmic Background Explorer (COBE) mission was to take precise measurements of the diffuse radiation between

1 micrometer and 1 cm over the whole celestial sphere. The following quantities were measured: (1) the spectrum of the 3 K radiation

over the range 100 micrometers to 1 cm; (2) the anisotropy of this radiation from 3 to 10 mm; and, (3) the spectrum and angular

distribution of diffuse infrared background radiation at wavelengths from 1 to 300 micrometers.

 

Science Highlights:

• COBE revolutionized our understanding of the early cosmos.
• It precisely measured and mapped the oldest light in the universe -- the cosmic microwave background.
• The cosmic microwave background spectrum was measured with a precision of 0.005%.
• The results confirmed the Big Bang theory of the origin of the universe.
• The very precise measurements helped eliminate a great many theories about the Big Bang.
• The mission ushered cosmologists into a new era of precision measurements, paving the way for deeper exploration of the microwave background by NASA's WMAP mission and ESA's Planck mission.

 

Do you understand now? Still persisting about "Nobody claims the CMBR is "proof" of anything"?.

 

Do you dare to call NASA nobody?

 

Will you ever learn?

And where does the word proof appear, please, in your source?

 

I reiterate: there can be no proof of any theory of science. Ever. This has been part of basic philosophy of science ever since Popper made his well-known observation that a scientific theory can only be disproved. In science, all theories are provisional. The only absolute facts are the observations - and even these are on occasion called into question by other workers in the field.

Edited May 18, 2019 by exchemist

[exchemist]

The first and middle phrases are quite strong: wrong and flat out wrong, specially for a Forum Moderator.

 

And telling to me that I use "unfounded assertions" is quite insulting, specially when I provide links from academia or institutions

which are first rank sites.

 

Also, you accusse me of using "straw man" arguments but you use "ad hominem" arguments instead.

 

I know the subject of this thread, in which I'm the OP. I'm also very well formed in electromagnetism and thermodynamics,

either on the theoretical or practical side. So, I don't make unfounded assertions NEVER!

 

And the highlighting of text by different means is the way I do things. Here, there or everywhere.

 

I started by saying that I disagree with the use of the Stefan-Planck theories in cosmology, because I dissagree

that the Universe behaves as a black body. Plain and simple. Such theories were developed for perfect black

bodies and, particularly with Wien-Planck, for perfect black body cavities with molecular or hertzian oscillators

into the walls, absorpting and emitting radiation under thermal equilibrium. I stand with my original position.

 

Later, this thread drifted towards the shape and size of the universe, where is now located the CBR leftover of the BB

and how the COBE, WMAP and PLANCK missions produced data to be analyzed and, also, how this data was analyzed

afterwards here on Earth.

 

I'd like to know why do you assert that I'm blatantly wrong in what I posted here. Which are your arguments, either on the

physics side, the mathematical side or the logical side.

 

And, if you can answer me: Which is your background to discuss this subject? Did you study in deep the theory of thermal

radiation or the history that goes from Kirchoff (1859) to Planck (1900)? Because I did, and I wrote a long paper about it,

which I posted in my blog. Just the pure theory of black body radiation till 1900, Nothing more, but nothing less.

 

And this knowledge is not pre-conceived notions, as you called. It's pure and absolute science, very well stablished.

 

And, finally, regarding your understanding that "there is no proof in physics", it really blew my head off!

 

I can't believe that any person can think that way. Then, all the history of proofs behind BB theory at the PTR institute

is pure BS? I don't know who taught you that, but this is what I call something "flat out wrong".

 

And, please, don't lecture me how to behave. I'm too old and civilized to receive recomendations about my way of doing things.

There are no proven theories in physics. There can of course be mathematical theorems used in the models of physics that can be proved. But the theories themselves? No.

 

This should be obvious if you can calm down and think about it for a moment. The history of science is littered with examples of theories that seemed "true" and then along came a new class of observation that showed they were either wrong or did not work in all cases. So clearly those theories cannot have been "proved", can they? And who, today, would be so confident as to say that none of our current theories will ever be showed wrong or incomplete? If only some of them, which ones?

 

No, the essence of the scientific enterprise is that it is always work in progress and its findings are provisional, at least in principle. Because we do not know the future and what we might find one day.      

[exchemist]

https://wmap.gsfc.nasa.gov/universe/bb_tests_cmb.html

 

That is the point, it is anisotropic so how can slight fluctuations in one direction be ascribed uniform properties at the edge of the visible universe, allowing a red shift to be applied. It could be a completely different temperature in the distance masked by a hotter temperature locally. 

 

Edit CMBR was one of the nails in the coffin of Steady state theory https://en.wikipedia.org/wiki/Steady-state_model It was predicted to be originally 5K. 

 

If the CMBR is at a uniform temperature in all directions. Galaxies could be moving through space rather than space expanding.  

It is almost totally isotropic, to a first and even second order approximation.

 

Such anisotropies as exist are minuscule, of the order of 1 part in 100,000. The existence of very tiny anisotropies was predicted by the Big Bang model, since there should according to that model have been some tiny unevenness in the universe, arising from random quantum fluctuations magnified as the universe expanded. This, I gather,  is what most of the COBE work has focused on.  

[OceanBreeze]

The first and middle phrases are quite strong: wrong and flat out wrong, specially for a Forum Moderator.

 

And telling to me that I use "unfounded assertions" is quite insulting, specially when I provide links from academia or institutions

which are first rank sites.

 

Also, you accusse me of using "straw man" arguments but you use "ad hominem" arguments instead.

 

I know the subject of this thread, in which I'm the OP. I'm also very well formed in electromagnetism and thermodynamics,

either on the theoretical or practical side. So, I don't make unfounded assertions NEVER!

 

And the highlighting of text by different means is the way I do things. Here, there or everywhere.

 

I started by saying that I disagree with the use of the Stefan-Planck theories in cosmology, because I dissagree

that the Universe behaves as a black body. Plain and simple. Such theories were developed for perfect black

bodies and, particularly with Wien-Planck, for perfect black body cavities with molecular or hertzian oscillators

into the walls, absorpting and emitting radiation under thermal equilibrium. I stand with my original position.

 

Later, this thread drifted towards the shape and size of the universe, where is now located the CBR leftover of the BB

and how the COBE, WMAP and PLANCK missions produced data to be analyzed and, also, how this data was analyzed

afterwards here on Earth.

 

I'd like to know why do you assert that I'm blatantly wrong in what I posted here. Which are your arguments, either on the

physics side, the mathematical side or the logical side.

 

And, if you can answer me: Which is your background to discuss this subject? Did you study in deep the theory of thermal

radiation or the history that goes from Kirchoff (1859) to Planck (1900)? Because I did, and I wrote a long paper about it,

which I posted in my blog. Just the pure theory of black body radiation till 1900, Nothing more, but nothing less.

 

And this knowledge is not pre-conceived notions, as you called. It's pure and absolute science, very well stablished.

 

And, finally, regarding your understanding that "there is no proof in physics", it really blew my head off!

 

I can't believe that any person can think that way. Then, all the history of proofs behind BB theory at the PTR institute

is pure BS? I don't know who taught you that, but this is what I call something "flat out wrong".

 

And, please, don't lecture me how to behave. I'm too old and civilized to receive recomendations about my way of doing things.

 

 

Your posts are so Filled with unfounded assertions and misconceptions, it is difficult to know where to start.

 

Plus, you either ignore anything that you do not agree with, or become indignant, so a rational discussion with you is all but impossible.

 

You don’t seem to be able to grasp the observed fact that the universe is expanding.

 

If you want to understand how the observable universe can be some 90 billion lyrs across, when it is only 14 billion years old, and light can only travel at the velocity of c, you must take this expansion into consideration.

 

At the time of last scattering, when the CMB was emitted, the universe was only some 90 Million lyrs across. It is now over 1000 times larger primarily because of expansion, not only because of the finite speed of light!

 

Fact: There is no limit on how fast spacetime can expand, and the speed of light will always be measured locally at c.

 

A quick calculation will tell you that galaxies at the very outer reach of the observable universe are moving away from us at about 3.2c:  ( I lyr/year x 14 billion years x 3.2 = 45 billion lyrs radius, very approximately)

 

You continually seem confused about this and keep insisting that these distant galaxies cannot be in the observable universe. Well, they are because we can still see them as they were about 14 billion years ago, when they were much closer to us.

 

Of course, we cannot observe them as they are today, at the distance of 45 billion light years, but they are part of our observable universe just the same because we know they do or did exist in our universe.

 

These are the concepts that are supported by mainstream cosmology so you may want to consider trying to understand them instead of arguing against them based only on your unfounded assertions.

 

Yes, I realize you are old and set in your ways but age does not automatically confer wisdom. When you make assertions here that go against the mainstream, you can expect to be challenged, so probably best to get used to it and not take it personally.

 

That is just some good advice, not a lecture, but take it however you want.

[exchemist]

Perhaps my grammar is crap and I view evidence as proof, not a mathematical proof, but more like would be presented in a court of law, when some who do not normally wear suits get dressed up :) .

 

However I recognise I may have slipped up. Evidence is not conclusive.

 

 

 

I don't think such anisotropies can be ignored that is why Lindes inflation theory is an improvement on the ludicrous singularity of the original big bang, and the uniformity of Guths inflation theory.  

 

The CBR is likely a result of particle creation, possibly of Big Bang Nucleo synthesis which originally predicted the CBR to be in the order of 5 Kelvins, which is a lot different to 2.75K, unless the theory has changed to match the measurements. 

 

Ascribing the CBR as excellent quality evidence of the big bang Nucleo synthesis happening in a fraction of a second 14 billion years ago might be a bit dodgy. I do not see why the Big Bang Nucleo synthesis could not be viewed as happening at a much slower rate, over a much longer period of time.

 

There is no satisfactory explanation for particle creation in the big bang. Hawking radiation only applies around black holes, Quantum Loop Gravity would appear to be a dead duck in an eternally expanding universe. Particles do appear out of vacuums very slowly.  You stated that inflation between a pair of virtual particles is hand waving, why? They are separated and become more real, the longer they are separated and like Hawking radiation from virtual particles would like decay to photons, or electromagnetic radiation, at very low energy levels. 

I don't think it is right to say the CMBR is due to particle creation. As I understand it, it is due to the adiabatic cooling by expansion of the primordial plasma getting down to the temperature at which neutral atoms formed for the first time. 

[exchemist]

I am briefly back at home, and just read the link, I can not believe no one has responded. It is very interesting indeed. I am not a chemist, and can not refute or reliably agree with the link. But to my none chemical eye, it seems very plausible indeed. It also supports a half baked idea I have that there never was a hot big bang, and Hoyle was more right than wrong.

 

I wonder if H2 could be a source of some dark matter effects in apparently empty space? 

 

If theoretical Baryogenesis occurs in space at near absolute zero (from perhaps condensates), forming Hydrogen at a very slow rate. The link shows that Hydrogen atoms combining to form H2 could form the better part of the CBR. AND The big Bang never happened. :)

 

I would also suspect a very low level of the CBR would be a side effect of slow or failed baryogenesis. ie when particles don't have enough energy to become stable, resulting in radiation in the form of photons, NOT polarized radio waves.

 

Thanks for the thought provoking link. 

Since you ask, I've had a look at the Marmet article. The short answer seems to be that he is talking out of his arse.  He claims molecular hydrogen has no "optically allowed" spectrum. But that's crap. Here's a paper giving exhaustive data on its spectrum: https://www.semanticscholar.org/paper/The-molecular-spectrum-of-hydrogen-and-its-isotopes-Dieke/0b53f460c2ec8b81e75eb532a296315e04749ba7 

 

If you click the spectrum diagram on the left you will see this includes a region around 6000A, i.e. 600nm, bang in the middle of the orange part of the visible spectrum. He quotes a load of irrelevant stuff about H2 not having a dipole, as if that prevents electronic transitions! This is really lousy physics. He seems to be muddling up the need for a dipole to excite molecular vibrations and rotations with what is needed for electronic excitation, which follows a different set of selection rules altogether. 

 

Nor does he explain how molecular hydrogen, which he has been at pains to point out is so transparent, can in his view radiate like a black body. 

 

Furthermore he fails to offer a reason why everything that is not hot in the universe is at 3K. Why 3K and not 0K? The Big Bang hypothesis accounts for that.  

 

I'd never heard of this guy, but when he wrote this he seems to have been either off his head or just a very  bad physicist.

Edited June 1, 2019 by exchemist

[LaurieAG]

Many cosmologists persist claiming that correct cosmological distances must be expressed in terms of proper distances (based on GTR and

expansion theories), even when objects farther than 14 Bly are not able to be observed by telescopes, because they recede faster than light.

 

Just out of interest, has anybody examined the HUDF red shift distances to see how large the HST depth of field (DOF) was in these types of observations?

 

I can remember sometime in the past seeing a simulated 'flyby' based on these red shift distances and wondered how large the DOF actually was if it takes 8 seconds to completely pass by a single galaxy (take your pick of diameter in light years, i.e. at a simulated velocity of multiples of c).

[exchemist]

Well, even for the anti-relativist KGB at Wiki, which custodies jealously the "einstenian stablished religion science", it was hard to downgrade the late Marmet to a figure of a looney cranck. But you succeeded in just a couple of paragraphs.

 

The man had an active life as a scientist for 40 years, until he retired. It's obvious that, once being free from the "suppressive system" (he had to make a living), he enjoyed making public his dissidences. He probably learnt from others, who did similar things while being actives within stablishment, and payed it dearly.

 

By the way, as he touched a string (or a chord) within your duty to custody "accepted" chemist and physics body of knowledge, you might be kind enough to enlight us about your credentials to speak with such an absolute certainty. Probably your trajectory in research and development will make me be ashame to ask for it.

 

Note: 10,000 posts at another forum don't count as scientific publications.

 

 

 

From the same link at Wikipedia that I posted and you didn't care to read:

 

Paul Marmet; (20 May 1932 – 20 May 2005) was a Canadian physicist and professor, best known for developing, along with his mentor Larkin Kerwin, a high resolution electron selector for the study of electronic states of negative ions. This instrument, along with a mass spectrometer he developed, was widely used by scientists for electron scattering studies which led to the discovery of enhanced vibrational excitation in nitrogen, and for the study of free radicals.

 

Career

Beginning in 1967 Marmet served as director of the laboratory for Atomic and Molecular Physics at Laval University in Quebec City, Canada, serving in that role until 1982. From 1983 to 1990, Marmet was a senior researcher at the Herzberg Institute of Astrophysics of the National Research Council of Canada in Ottawa. In 1990 Marmet was an Assistant Professor of Physics at the University of Ottawa.^[1]

 

Bibliography

Paul Marmet published more than 100 original research papers, as well as a number of books, websites and animated demonstrations for the teaching of Physics.^[1]

 

Opposition to Quantum Mechanics, Relativity, and the Big Bang

In his later years Marmet was an outspoken critic of the Copenhagen Interpretation of Quantum Mechanics, the theory of relativity, and the Big Bang cosmological model. In 1993 he self-published a book entitled "Absurdities in Modern Physics".^[2] He also maintained a web site devoted to his ideas.^[3] His views have not found acceptance within the mainstream scientific community.

How about telling me what is wrong with the science in my objections to what he writes?

 

People do go crazy, you know. The guy was pretty old when he went all peculiar and resorted to self-publishing crank stuff. 

Edited June 2, 2019 by exchemist

[exchemist]

Chemistry is not something I remember much about. I assumed when two hydrogen atoms combine to form a hydrogen molecule via a covalent bond , they would give of radiation ie the reaction is exothermic and to separate them they would require energy, endothermic reaction. Since molecules like to be in their lowest energy state, H2 is stable and will require energy to separate the atoms.  

 

Simple link for them as might not know what I am waffling about.

https://opentextbc.ca/chemistry/chapter/7-2-covalent-bonding/#CNX_Chem_07_02_Morse

 

Here is another link that claims molecular H2 does not emit radio energy http://www.astronomynotes.com/ismnotes/s3.htm " Different types of atoms can combine in the coldest regions of space (around 10 K) to make molecules. The cold molecules are detected in the radio band. Most of the molecules are hydrogen molecules (H₂) and carbon monoxide (CO). Actually, molecular hydrogen does not emit radio energy but it is found with carbon monoxide, so the radio emission of CO is used to trace the H₂."

 

I am flummoxed, does molecular hydrogen in deep space emit a spectrum? :unsure: Why would it? 

 

Re the dipole, H1 has a permanent dipole, whereas H2 is a little unclear. It is even more unclear why H2 having or not having a dipole is even relevant.

 

H1 + H1 producing H2 is exothermic and will give of radiation, if that accounts for the CBR then maybe he is not a total crank. 

 

A curve fit from a Hypothetical Big Bang 40 billion years ago until now, resulting in a CBR of 2.75K might also be the work of cranks

Neither atomic nor molecular hydrogen has a permanent dipole. Such a dipole (or rather a dipole change during the motion)  is required in order to couple EM radiation to the vibrations and rotations of a molecule. Hence hydrogen, like N2 and O2, are transparent in the IR and microwave regions. 

 

But electronic transitions, which are what give rise to visible and UV (and some IR) absorption and emission, require instead a "transition dipole", formed in the process of an electron moving between orbitals (molecular orbitals in the case of a molecule, obviously). This is to do with symmetry and angular momentum requirements of the wavefunctions of the before and after states. (For example a photon is a boson with a spin of 1, so an electron can't jump between two states both with zero angular momentum. This gives rise to the "selection rules" for electronic transitions.)  So H2 can have an electronic (band) spectrum and indeed it seems it does, from the spectral data I linked to in my previous post.

 

Certainly if two H atoms bond to form H2, energy has to be given off, in order for the bond to form. If at least some of this bond energy is not carried away, the atoms will have enough energy to rebound from their encounter and split apart again. Normally collisional deactivation with a 3rd molecule, before the atoms have time to rebound, takes care of this. In space however might be relatively rare (I think there are only about a million atoms per cubic cm), so a lot of encounters of atomic hydrogen may not lead a molecule forming. I do not know if there is a radiative mechanism for the atoms to lose energy before they fly apart again. The absence of a dipole would suggest not, i.e. the molecule cannot radiate away vibrational energy in the bond that is trying to form.

 

But you raise an interesting issue: what is the usual mechanism by which molecular hydrogen forms, in deep space where molecular densities are so low?    

Edited June 2, 2019 by exchemist

[exchemist]

Gas Nebulae formed from an abundance of gas in space. Ionic bonds form easily between individual Hydrogen atoms in close proximity, this would happen in nebulae when gravitational pressure increased prior to forming stars. 

 

Baryogenesis resulting in individual Hydrogen atoms, will combine to form H2 molecules, in Nebulae if not in empty space.

 

I do not think I have seen references to H2 as a possible cause of Dark matter effects seen in "empty" space, lots of exotic things have been put forward. If H2 cant be detected directly, then the fringing of light attributed to dark matter might be H or H2. https://phys.org/news/2018-12-faint-galaxy-clusters-illuminates-dark.html

Sorry but no, ionic bonds do not form between hydrogen atoms, under any circumstances. 

 

My point in the previous post is that, from a chemical kinetics viewpoint, if two atoms approach one another and start to form a bond, something has to carry away some of the energy released when the bond forms. If this does not happen, then the 2 constituent atoms have enough energy to fly apart again.  

 

I am sure that over millions of years, enough 3-body collisions can take place to allow molecular hydrogen to be produced, very slowly. I am just intrigued at what the process is for each molecule. Because I do not think there is any way that two atoms will just combine. They have too much energy: something has to carry some of it away.  When two polyatomic molecules combine, e.g 2 methyl radical form ethane, there are more degrees of freedom within the molecule, to park some of the energy released when the new bond forms. But when 2 individual atoms bond, you need a 3rd body to do it.   

Edited June 2, 2019 by exchemist