Welcome to The Big Blog Theory

The science of The Big Bang Theory is revealed!  (Of the sit-com that is, not the theory of the origin of the universe.)  Last season, I was discussing possible titles for this blog with the writers of the show, who had lots of  terrific ideas.  After all, that’s what writers do.   One of the lead actors passed by, overheard us,  and  gave us this title over his shoulder,  just as he was walking into a scene.

The title “The Big Bang Theory”  may originally have been coined in derision.   (Of the theory of the origin of universe that is, not the sit-com.)  Starting in the 1940’s, Fred Hoyle and other proponents of a theory they called the “Steady State Theory” of the  universe,  took the observation that  the universe  expanding as discovered by Edwin Hubble in the 1920’s, and proposed that the universe was constantly generating new matter to fill the new space.  They went further to say the new matter was generated at exactly the rate to keep the universe always looking the same at all times.

The Steady-Staters dubbed this idea  “the perfect cosmological principle”.  “Perfect” because their universe was the same at all times, compared to the more prosaic “cosmological principle”,  whose universe is merely the same in all places (homogeneity) and in all directions (isotropy).    Some readers may complain that such a cosmological principle is clearly not true.  Of course standing on Mars your immediate neighborhood would look quite different than to someone standing (briefly) in the central core of Jupiter.  However, the cosmological principle applies only to the universe only on its largest scales, distances crossing many hundreds  of galaxies.  The principle is an empirical observation,  something subject to change if observations ever dictate it.  There are even some tantalizing hints in recent data to that effect.


A view of the Universe on the largest scales ever observed. Every dot is a galaxy. Although features like walls and voids are visible, on the largest scales (hundreds of millions of light years) the universe appears homogenous and isotropic.

Their rival theory originated a couple of decades earlier, in the 1920’s.  A Belgian priest, Georges Lemaître, took  guidance from the (then) recent theory of General Relativity by Einstein and  proposed that all the matter and energy in the universe was created in a single event and the universe became less dense as it expanded.    Perhaps Lemaître, a priest,  was pleased with the creation event implicit in the model.  The Steady-Staters disagreed with the  idea that so much matter and energy could be created in a single event and Hoyle poked fun at Lemaître’s theory by giving it the moniker “The Big Bang” during a radio interview in 1949.

The Steady-State and Big-Bang models each were plausible and provided a good description of the history and evolution of the universe.   But at least one had to be wrong.  Fortunately, like all useful theories,  each made definite and distinct predictions which could be tested by observation.   It took several decades, but by now, the Steady-State idea is in conflict with a wide variety of data.  For example, the two theories predict a different number of distant galaxies, and the numbers found by astronomers agree with the Big Bang Theory and disagree with the Steady State Theory.    Moreover, the relative abundance of  elements such as deuterium, helium and lithium compared to hydrogen can be measured.  The data are explained well by the entire universe having been a nuclear reactor when it was between about 3 and 20 minutes old, a state which the Big Bang Theory implies the universe must have gone through, but never existed in the Steady State model.   The final death knell of the Steady State theory occurred in the 1960’s when a microwave radiation was observed coming from all directions in the sky.  This radiation, now known to be the oldest light in the universe is called the “Cosmic Microwave Background”.  It was produced when the early universe was hot and opaque, a period that never existed in the Steady State model and which it could not explain.

A more advanced summary of problems with the Steady State idea is given by my friend Ned Wright in his terrific cosmology tutorial.

The Steady-Staters were not crack-pots, and they were certainly not dumb. Quite the contrary, Fred Hoyle was the first to describe how heavy elements were synthesized from hydrogen and helium in stars.   Many of the observations which eventually favored the Big Bang Theory took a long time to become convincing.  For example, it took decades to unravel what fraction of lithium observed was primordial and what was generated later in cores of stars.   The initially predicted age of the universe by the Big Bang Theory made it younger than the oldest stars, a situation only fixed when the difficult to measure expansion rate was finally pinned down.

Even after most of the scientific community favored the Big Bang Theory,  Hoyle tried to keep the Steady State theory alive.  While some have ridiculed his stance, there is a healthy place in scientific discorse for a few serious-minded skeptics.  Hoyle continued to mold the Steady-State Theory to explain the data although the theory necessarily became more and more baroque.    Ever the skeptic, later in life Hoyle challenged that biological evolution could be driven by natural selection.   However, one of his basic ideas, panspermia, that the building blocks of life may have come to Earth on comets was for a time  a serious contender.   At least two views of such contrariness can be taken:  Perhaps his skepticism caused a sharpening of the mainstream arguments, overall serving science by making its arguments stronger.   Or perhaps we are left to take comfort in the adage:   Funeral by funeral science marches on.

Perhaps most importantly, had the Steady State Theory been right, the theme song to the show would have been nowhere near as interesting:

The whole universe was in a Steady State.

And nearly 14 billion years ago, nothing special happened, wait…


24 Responses to “Welcome to The Big Blog Theory”

  1. yvaine Says:

    The blog is great! I haven’t gotten totally lost in the science just yet, thank goodness. Thanks for keeping it on not-really-layman’s-but-easy-enough-to-understand-if-you-read-carefully terms.😀

    I’m curious… so which of the actors actually christened this blog? 🙂

  2. Big Bang Forum Says:

    Greetings from Germany🙂 !

    First of all, thank you so much, Dr. Saltzberg, to give the show “The Big Bang Theory” the scientific fun. This show is just phenomenal and on top, thanks to your efforts, scientifically correct.

    Unfortunately the TBBT show first aired in July 2009 here in Germany (in a dubbed version), but fortunately due to Amazon.com and the DVDs, a lot of German fans know the show in its original english version way before it was released in Germany.

    By the way, I enjoyed the DVD bonus material and it was really funny as you explained that you wrote the answer to an exam on one of the boards on the set and that your class was in the audience that day, that’s what I call geeky.😉

    And because TBBT is such a great show we instantly wanted to give the German audience a platform where fans of the show and especially geeks of all kinds can share their love for technology, science, sci-fi and everything what “The Big Bang Theory” embodies.

    So we brought the BIG BANG FORUM (http://www.big-bang-forum.de/) into being.🙂

    Even though our site is still pretty young we already get a lot of positive responses from all around the world, because of our efforts to provide english transcripts of the episodes, so that non-natives in the english language through these text documents can read what was spoken and then translate and understand it better.
    And because of this we quickly decided we need and want to make the Big Bang Forum bilingual (German and English).

    So, I don’t know if you have the time to read this here, but I really hope you do, because I would hereby officially like to award you with an honorary membership in our Big Bang Forum.🙂

    For details, please feel free to contact me at my stated email address.

    Thanks again for your great contributions to make TBBT what it is.



  3. victor Says:

    Hi Professor Saltzberg,

    Thank you for your work in the show and for having this blog (I am having a lot of fun with both).

    There was an episode about a Physics Bowl, could you comment on the last problem they were given? or perhaps add an entry about that episode?


    • Naomi Says:

      Victor – that last problem in the physics bowl is best explained by a book called “The Elegant Universe” by Brian Greene (Cornell physicist), it has that exact diagram in one of the later chapters (and doesn’t go into advanced calculus to explain what is happening).

      From memory the diagram is related to string theory – when two particles (strings) are smashed together, momentarily converted into energy (one string vibrating a certain way), and then two new particles appear (the string breaks up again into two separate and different particles [strings] from what you started with).

      But yes it would be great to see that diagram worked out for that particular question scenario.

  4. geekgroupie Says:

    WOW just WOW

  5. Traducción: “Bienvenido a The Big Blog Theory” « The Big Blog Theory en Español Says:

    […] Artículo original por David Saltzberg […]

  6. Ant Says:

    Nice site, but it would be nice to see older episodes and seasons!

  7. Bem-vindos ao The Big Blog Theory (em Português)! « The Big Blog Theory em Português Says:

    […] feita a partir de texto extraído de The Big Blog Theory, originalmente publicado em 19 de Setembro de […]

  8. Phil Says:

    Fred Hoyle had his good points and bad points, like most humans. He was one of the earliest astronomers to write popular astronomy for the public and in many ways helped plant the seeds for amateur astronomy. His observations and analysis of comets made him one of the pioneers. But unfortunately his die-hard resistance to the Big Bang Theory will always be what he’s most known for.

    Just as many very famous early 20th century scientists refused to believe the atom could be split and Thomas Jefferson refused to believe that meteorites could fall from the sky scientists are very human people who can make mistakes.

    When the Microwave Anisotropy Probe satellite was launched I suggested that it be named after Hoyle and only a few folk got the joke.

  9. Tejaswy Says:

    How about season 1 and 2?

    • David Saltzberg Says:

      Thanks. However, I am not sure there would be that much interest in it, or where/how I could post them in a way that made sense.

      • Jess Says:

        I’m sure there would be interest – there are people like me who only recently started watching the show, and are going through the previous episodes on DVD – I have only just got up to season 3. Also if you wrote about the science in earlier episodes, people could watch the DVD to remind them of that episode.

        It is a rather big undertaking, writing about two whole seasons, so perhaps you could just write about some of the episodes.

        Most blogs let you back date posts, ie set the date of the post to a past date, and it will appear in that point in your blog. Alternatively you could have a separate blog for seasons 1 & 2.

  10. JJ Says:

    Hello professor, just wanted tell you how I’ve grown to appreciate science because of your show and this supplemental blog. The wife and I are humanities majors and didn’t enjoy the few science classes we took. Now we find ourselves explaining scientific ideas to our friends. Just wanted to say thanks for expanding our horizons!

  11. Germán Says:


    Excelent blog! We´ve just discovered it after seeing your name in the credits of one of the old episodes of TBBT. One of the things that´s make us laugh the most is the accuracy of the physics jokes and replies, it´s fantastic and your work is amazing, I imagine that it´s probably a very hard work to make science hilarious for people who hasn´t studied those subjects.

    As a fan of the series, a PhD student and blogger, I´m very interested in doing a brief interview with you for our blog, would you be open to the possibility to answer a few questions for all the fans that The Big Bang Theory has in Latin America and Spain?

    Please, let me know if you are ok with this proposal. You can contact me through the data I left in this comment.

    Kind regards from Argentina!!

  12. John Wyatt Says:

    Is “a spoof of the Born-Oppenheimer approximation” explained in here anywhere? I’ve only been able to find sites that couldn’t figure out the joke.

  13. Bad Scientist Says:

    This blog is an amazing idea, I can’t believe I just discovered this by chance, being a big fan of Big Bang Theory.

    Also, I wanted to ask professor Saltzberg if there is any chance for my new blog about science to exchange links for blogroll.

    Thanks for all the work done, and keep it going!


  14. Sebastian Says:

    Hi Everybody

    Im from Germany, Hamburg.
    Frist I wanted to note, that lots of Lenards works belongs to
    chemistry on a german university.

    I have some idea for the big bang theorie.

    A Episode:

    Penny has little to no money. She walks upstairs and meets
    Sheldon is crying on his mobile phone.
    penny asks, whats wrong.
    sheldon tolds her, that there is a exhibition and Leslie
    kicked him of the physics branch.
    So he wanted his own table to collected third-source money and
    and a exhibition hostess.
    Penny catched her chance .
    She wanted to work as exhibtion hostess for sheldon.

    What do you thing, should I try to work out this plot
    and try to send to the big bang producers?
    my email: jsg2@gmx.de

  15. David Olsen Says:

    Just discovered this blog. Cool idea.

    You’re slightly incorrect. While Fred Hoyle did coin the term and he was adamantly opposed to the substance of the theory, it was not actually a term of derision. He was also a science educator and he thought the term was an adequate short-hand description of the rival theory. In this instance, he wasn’t trying to denigrate it as elucidate the idea for his audience. And apparently, he had a knack for it as no one has come up with a better term.

  16. Kevin L. Schwartz Says:

    Hi! I’m discovering this blog a few days late, it seems. Like, about 1,734 days, give or take.

    I wrote “the best science joke on the Internet” that Penny regales the gang with in “The Dead Hooker Juxtaposition.” I write all sorts of things, including lots of nerdy jokes. Said jokes are compiled here:


  17. Kevin L. Schwartz Says:

    I’m now credited at IMDb (and sundry other places around the Internet). So I don’t need any help with that, for instance.

    But I would still love to have the opportunity to write some more science jokes for the show.

    • Kevin L. Schwartz Says:

      I write them all the time. Here’s one from yesterday. I can imagine Sheldon saying this without much need to change it all that much:

      [People keep saying I’m totally obsessed with numbers. Unfair. Maybe I’m 98.7654321% obsessed with numbers.]

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