News: International Astronomical Union has no Definition for Big Bang

IAU has no Definition for Big Bang

(c) copyright 2011 David Dilworth

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“…the [Big Bang] definition is a mess.” – Prof. P. James E. Peebles, Princeton University, Feb. 2011

News: (Carmel, California) The world’s most widely respected astrophysics organization, the International Astronomical Union (or IAU), has affirmed that it has no definition for any Big Bang model.


At the same time the world’s most cited cosmologist, Princeton’s Professor P. James E. Peebles, says that the Standard Cosmology Model’s “definition is a mess.”

Prof P.J.E. Peebles

Prof P.J.E. Peebles

Prof. P. James E. Peebles, Princeton University, recently wrote (1) —

The name Big Bang is a very poor choice because it suggests a moment of time — a bang — and maybe also a place — where the bang occurred. Neither is part of the reasonably well tested theory of the evolution of the universe from a hot dense state to what we see around us. But the name has stuck, so I have stopped boycotting it.”

As you see the definition is a mess. The connotation to me is the relativistic theory of the expansion of the universe.

Big Bang was chastised recently for its lack of a complete unambiguous definition by my paper “Ground Rules for Cosmological Physics” (

(Lack of an adequate definition is a logical fallacy called an Exclusion or Ambiguity Fallacy when the definition can have multiple meanings. “Equivocation / Ambiguity: The fallacy of failing to define one’s terms.“)

“As of 2009 we have no agreed upon unambiguous, testable definition of Big Bang or Inflation models.”

“A related serious problem with the “Big Bang” claim is that there is no . . . one central repository for its definition.”

“It would be a big improvement to Big Bang’s credibility to have one official place where its definition is kept, similar to how NIST (National Institute of Standards and Technology) is used for measurements.”

So in search of a definitive definition of Big Bang (2) and inspired by the thoughtful suggestion of San Diego State’s Andrew Young that IAU is a reasonable place to maintain such a definition, I wrote to IAU’s Cosmology Commission asking that they consider providing one. IAU confirmed that as of February 2011 they have no definition for Big Bang.

“. . . the IAU has not provided a definition of the Big Bang.”

IAU’s Cosmology Commission VP, Brian Schmidt, added his personal opinion that it might stretch the Commission’s mission more than a bit to do so. He suggested that —

“Big Bang is a broad concept under which many different ideas of the early Universe reside. It is not a physical object like a Planet, nor is it a constant of Nature”

and that

“there is no precedent for our commission defining broad theoretical concepts such as the Big Bang.”


I find IAU’s position eminently reasonable. It indicates, perhaps dramatizes, a fundamental problem Big Bang models have with basic astrophysics science; that currently Big Bang is too ambiguous to be a scientific hypothesis.

This does not necessarily mean that individual components of the standard model are inadequately defined. For example, the Spectral line Redshift-to-Distance correlation claim does adequately meet all the criteria or conditions for a valid hypothesis. However, it does mean that the overall “Big Bang” concept does not yet meet scientific muster.

An analogy I use is how getting a Driver’s License requires you to complete an application form – before you can take the driving test.

In my view, Big Bang is just like an incomplete application — until the idea is adequately defined (until the form is filled in), meeting the minimum for a scientific claim, it simply cannot claim to hold the status of a scientific hypothesis or theory.

Cart Before Horse

Cart Before Horse

To debate evidence before a scientific concept has a clear, meaningful, unambiguous definition — is the equivalent of “putting the cart before the horse.”

Burden on Inventor – Not on Skeptic

As I also try to point out in the paper — the responsibility of defining a scientific claim is on the proponent – not on the skeptics. This means the burden of defining Big Bang is on its supporters. Once a scientific hypothesis is adequately defined, then the burden of dispute is properly placed on a skeptic.

Reversing the burden to a skeptic without a complete definition is another logical fallacy called Shifting the Burden of Proof. “A fallacy that challenges opponents to disprove a claim, rather than asking the person making the claim to defend his/her own argument.

Hypothesis and Definitions Needed – Not History

A simple web search echoes the inescapable notion reached by my years of reviewing more than a hundred Cosmology books and hundreds of cosmology papers — that most Big Bang “definitions” are in reality almost exclusively a history of the idea rather than a scientific definition for a hypothesis; the Wikipedia entry is an example.

So, until a credible body or a paper provides a complete definitive definition of Big Bang — here are some resources that could help. Yet even when combined these remain incomplete as a scientific hypothesis:

1. Prof. P. James E. Peebles provides what is probably considered the best available narrative description of the science of facets of the standard model in his 1993 book “Principles of Physical Cosmology.” It provides a coherent, internally consistent description with abundant detail (and all the necessary math), but does not include a complete concise high level definition.

2. “The Standard Model” also by Prof. Peebles (1998)

3. “The Future of the Universe” by Fred Adams and Gregory Laughlin (Sky and Telescope Oct., 2000) is an excellent timeline of one of the many Big Bang models, but it is not really a definition.

4. I provide an overview (math-free) definition of the many Big Bang models here — Big Bang definition, but it is also incomplete – because I can’t find the needed answers for all the parameters – and I’ve looked hard and long.

Mistaken for Hypothesis: While some have suggested LCDM models (Lambda Cold Dark Matter models – adjustable versions of Big Bang) are complete scientific hypotheses, even if they were, those same advocates acknowledge that no LCDM model is a complete definition for Big Bang.

However, LCDM models have fundamental definition problems of their own, explained in my paper “Ground Rules for Cosmological Physics” and the article “Physical Cosmology Hypothesis Application Form.”

LCDM model problems include a failure to define “space” or even estimate the number of intergalactic photon-matter interactions per year (PMIY).

Part 2 of this article is the new (Feb 24, 2011) “Physical Cosmology Hypothesis Application Form“.

I welcome your suggestions for how to come up with a definitive definition of Big Bang.

Best wishes,
-David Dilworth

Notes and References:

1. Personal communication (Feb 2011)
2. “Definitive Definition for Big Bang” could be abbreviated to D2B2.
3. “Poof, There It Is Theory

Further reading:

The Burden of Skepticism by Carl Sagan

The Scientific Method, A helpful guide by Science Made Simple

How to Write a Science Fair Hypothesis


Learn More About the Scientific Method

Update 1 (June 2011): This article was just nominated for the “3 Quarks Daily 2011 Science Article Prize” ! (What an honor – because there are some really fascinating articles nominated.) If you would like to review the whole set of nominated articles click here :

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Update 2 (June 10, 2011): I am delighted and honored to report that this article was voted the 3rd most popular science article making it a semi-finalist in the “3 Quarks Daily Prize” contest on June 10, 2011. Only three of the 87 (fabulous) science articles received 100 or more votes. Thanks to you readers, colleagues and friends this article was one of those three.

Update 3 (June 10, 2011): Due to another article incorrectly describing and disputing this one I’m providing “Article on Big Bang’s Inadequate Definition Disputed – But Article Emerges Unscathed” to correct that other article’s errors.


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21 Responses to News: International Astronomical Union has no Definition for Big Bang

  1. Pingback: Physical Cosmology Hypothesis Application Form | Cosmology Science Blog © 2011 David Dilworth

  2. Peterson says:

    Thought provoking. But why does a theory need a hypothesis?

  3. David says:

    While ordinary conversations can use the words “hypothesis” and “theory” nonchalantly, science, particularly physics, has strict limits on the use of those terms.

    A Hypothesis is an un-ambiguous testable idea that precedes a scientific theory. Your idea must have a valid Hypothesis. Then that hypothesis must have passed multiple successful tests before it reaches the threshold of theory.

    For more detail please see —



  4. This question I think provides it’s own answer:- Why did there have to be a beginning?
    We know a mass of stars exists. We know how they form [more or less] and if we are expected to accept the notion that they are all heading away to,,,,, where, there is no proof that the whole bounded mass was once a singularity.

    Light from all stars is shining in every direction and is not focused only on our telescopic lenses. And if a star is 13.6 billion lightyears away from us its light is shining away the same distance 180 degrees from the beam shining at us.
    That simple fact shows that stars recycle their energy and mass within an infinite boundless space. As it is a continuous action there could be no end [crunch] therefore there could be no beginning.

    I may not have composed this very well for which I appologise. “Genesis Continuou” says it all.

    Thank you

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  7. Dear David and Friends,
    My entry in your competition, [If that is what it is] is due to Hilton alerting me to it. Yesterday. Please disregard my previous attempt as I’ve had time to consider what I should be saying.

    I have now read most of your paper on Big Bang without checking out the links, that is because now, at 82 years of age, I get a bit tired.. That is no disrespect for your excellent work. It’s just that age keeps creeping forward.

    The Big Bang Model in name requires some comment.
    A model, as I understand it, is a representation of something real or imaginary. The next step I suppose is Theory, which quite clearly then Big Bang is not..
    I shall settle for ‘Imaginary’ . Hooray ! Walt Disney will be turning in his grave with delight..

    First question:- Why does there have to be a beginning?

    Answer:- It looks perfectly Okay without one to me..
    So what’s wrong with Big Bang and it’s frame and structure?

    Let’s skip the singularity, it’s ignition and what caused it to . How it sorted itself out in that tiny expansion timeframe into galaxies, equipped with gravity, ability of its stars to burn and shine, and keep on expanding away out through or beyond some sort of boundary is baffling.

    Then, when it reaches boundary zero, it’s mass goes into shrinkage mode and finally reverses in a Big crunch.

    This universe containment stretches from here in at least one direction, a distance of 13.7 billion light-years. [I dare not say, in every direction, as that would place us in the middle, with the distinct proposal that just under or over my chair or left or right, forward or behind, the whole content of the universe once existed… Ouch..

    So here is a vital point to consider. If a galaxy is examined and claimed to be 13.6 billion light-years away from us, it’s light must not only be visible through our telescopic lenses but also visible everywhere else in the universe up to that same distance away from it.
    Also, since the stars shine globally it stands to reason that light shining away from them 180 degrees from our view, their light is shining into an expanse of space that is not claimed to exist as part of their total mass. It can’t be a neighbouring universe since conservation within our universe would be defunct as a law.

    So here is the universe according to “Hardy” Not Hoyle
    Every shining star is radiating its subatomic particles and therefore reducing it’s mass accordingly. So when we assess the size of a star it would have to include it’s core, plus its radiated particles beyond it minus the amount of subatomic particles that have been absorbed by what they struck on their journey. [Will someone do the equation for me – and make my day]

    The simplicity of these factors gives credence to my theory, or whatever it should be called, that the universe is boundless and infinite in size. Matter travels via the passage of light, globally from its source as well as through gravity. Stars wouldn’t die otherwise.

    David Calder Hardy

    • I think that it matters where you are if you need to identify the central location of the singularity and it’s bang from what it was to what it became.

      Now let’s suppose you where 50 billion lightyears beyond our? universe and in another one. You’re pearing though your telescope one night and WOW. you see what looks like a new star being born. You quickly inform your astro – friends what’s happening.

      By Jove, one of them says. That looks like a universe that’s shrunk down to one small star’. “But it’s getting brighter by the second” says one of them.
      “Oh God! says another – It’s another BIG BANG. ‘ HOYLE, WHAT HAVE YOU DONE?

  8. indora chaviaras says:

    always expanding my mind!

  9. Come on folks. Join in the fray. Put your best wrongs and rights forward on the Big Bang . It’s either right or wrong; and if it’s wrong, where is it wrong?

    Is it because we see a star as just a wee point of light in the sky and not realise that it’s energy is radiating over to us and past us, and just as far in every other direction. Matter’s on the move – and it’s even on the move when you switch your car head lights on..

    Am I right or am I wrong?

    Is light shining out the other side of a star 13 billion lightyears away and could it be seen by someone on a planet 26 billion lightyears away from us? YES OR NO….

    And don’t forget that the same star isn’t where it appears to be because it’s on the move as well. In a non centralised expansion scenario it could be anywhere..

    Thank you David for this offer.

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  12. David Calder Hardy’s Cosmology

    Better Big Bang or

    A more Believable Singularity
    A New Singularity Theory {If this is funny it’s also serious – If this is serious it’s also funny}

    How to Have a Singularity and get Rid of the Problems Existing with the Old ‘One and Only’ Cumbersome Singularity

    The Biggest Bang
    Somewhere away in shrunken space
    Light years away from earth
    Within a microscopic place
    A singularity gave birth
    It was a huge explosion
    The grandest sole event
    And so has Science chosen
    This blast as Heaven sent (DCH)

    Oh well, I’ve tried.

  13. Pingback: Big Bang: pues empezamos bien, y eso que ya llevamos ~13.700 millones de años con esto | Noticias de tecnología

  14. Since all stars radiate their energy globally, expansion must be in all directions. Direction meaning to to from. Globally, of course.

  15. Joseph Brown says:

    One reason why there isn’t an adequate definition for the “Big Bang’ is because there is no actual proof it occurred. It is only a man made theory, which denies the existence of an intelligent Creator. JRB 6-23-11

  16. You are quite right Joseph. However, the big question is – Why doesn’t Science move on? All the clues exist that point to an infinite boundless universe.
    We see light from a star shining from 13.7 billion light years away and in an expanding universe that’s where it was 13.7 billion years ago. It’s light 13.7 billion years ago was also shining 13.7 billion light years away into the distance . 13.7 X 3 = 41.1 billion light years from us, so there could be some other being over there seeing that same star through his telescope…


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