When I was a boy, world was better spot
What was so was so, what was not was not
Now, I am a man, world have changed a lot
Some things nearly so, others nearly not

There are times I almost think
I am not sure of what I absolutely know
Very often find confusion
In conclusion, I concluded long ago

In my head are many facts
That, as a student, I have studied to procure
In my head are many facts
Of which I wish I was more certain, I was sure

  • Rogers & Hammerstein: “The King and I”


As a young student, my science teacher made sure that we knew there were nine planets in our solar system.  Nowadays science says that there are only eight plus a host of ‘dwarf planets’.  Lately there has been some evidence, causing some scientists to debate the possibility, that way way way out there is a new ninth planet in our solar system.  But this is uncertain.  ‘Some things nearly so, others nearly not’ as the song says.

Don’t even get me started on the nutritional sciences.  What a few years ago was absolutely bad for your body to consume is now not so bad, maybe even good.  Every week there is a ‘discovery’ of a new wonder food that is guaranteed to help you live longer and healthier.  And in a few years we will be told that it probably doesn’t work that well.  Me, I still take extra vitamin C when I get a cold even though now the doctors tell us that really doesn’t do any good.  Some things you learn early in life are hard to get over.

Just about a century ago, a group of crackpot, radical geologists proposed that the very continents we stand on – made of solid rock! – float on an ocean of magma underneath.  And the continents actually drift – apart, together.  Roundly ridiculed by the establishment in the geological sciences, it took six or seven decades of gathering evidence and furious debate to win over the majority of their brethren.  Literally a tectonic change in our understanding of our planet.  From this we have a better understanding of volcanism, earthquakes, and the distribution of minerals and plant and animal life around the globe.

About four centuries ago, Isaac Newton discovered and mathematically described the laws of universal gravitation.  An unseen force, acting at a distance, caused an attraction between everything in the universe.  Newton proposed that this force acted proportionally to the product of the mass of the bodies and inversely proportionally to the square of the distance between them.  This theory was hailed as a great achievement; Newton was knighted and at his death buried with honors in Westminster Abbey.  To this day our children are taught about the gravitational force, the way it works, and how to predict and analyze movement with Newton’s mathematics.  As physics progressed, other forces have been discovered and added to the list:  the strong nuclear force, the electromagnetic force, the weak nuclear force; all stronger than the gravitational force.

Along comes Albert Einstein in the last century and, like so much else that we were absolutely sure of, completely blows up the subject.  According to Einstein, there is no such thing as the gravitational force.  Mass distorts or warps the space time continuum.  As object travel along their world lines in the space time continuum of our universe, the world lines themselves are curved by the warping effects of mass in the space time continuum.  So gravity, as a force, does not really exist.  Newton’s laws are useful for describing how bodies move – at less than relativistic speeds – but gravity, per se, has been removed as a physical force and is now just a general term that describes the warpage of space time.

This is not a subject that is frequently taught in high school science classes.

And let’s not even get started talking about the nature of time.  My head is already hurting. “ In my head are many facts/That, as a student, I have studied to procure/In my head are many facts/Of which I wish I was more certain”

Science, it seems to me, is an ever evolving body of knowledge and our attempt to organize and understand it.  Science is not static and unchanging.  We know more today than we did yesterday, and thank goodness for that.  Our understanding of the nature of the universe is more profound than that of scientists in former days.  Science, it seems to me, is full of discussion and debate as we try to revise our thinking to accommodate the new information constantly streaming in.

Science, it seems, is never ‘settled’.  I certainly wouldn’t believe anyone that says it is.

To finish our song:

There are times I almost think
Nobody sure of what he absolutely know
Everybody find confusion
In conclusion, he concluded long ago

And it puzzle me to learn
That tho’ a man may be in doubt of what he know
Very quickly he will fight
He’ll fight to prove that what he does not know is so

About waynehale

Wayne Hale is retired from NASA after 32 years. In his career he was the Space Shuttle Program Manager or Deputy for 5 years, a Space Shuttle Flight Director for 40 missions, and is currently a consultant and full time grandpa. He is available for speaking engagements through Special Aerospace Services.
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8 Responses to Gravity

  1. Charley S says:

    Once there were 4, earth, fire, water, and air. Now look at us!

  2. Beth says:

    Wayne, I love this post! For some it is easy to get angry when ‘what we know’ turns out not to be so, but I love that we are (or should be!) constantly learning and exploring and pushing back.

    And the song…how I feel often 🙂



  3. J says:

    And you so adeptly sidestepped the clatter about climate and mans effect on it! It would seem some of the ‘certainty’ may be rolled back a tad, when we get smarter. Love that last line: “Very quickly he will fight – He’ll fight to prove that what he does not know is so”

    Great perspective. Thank you.

  4. Roger says:

    It is worth pointing out that even great minds can be fooled. Einstein wrote a glowing foreward to a 1955 book that clearly showed there was no such thing as continental drift. Ooops. (Charles Hapgood: Earths Shifting Crust”)

  5. Lewis Van Atta says:

    Wayne, (and Mr.J), regardless of how the science seems to change, one thing remains constant: it still has to explain the observed and experimental evidence. Einstein’s gravitational theory (general relativity) explained irregularities in the orbit of Mercury that Newton’s theory could not. And Mr. J: any climate theory MUST account for the observed evidence that the planet IS warming. Like it or not, that much IS certain.

  6. jack crossfire says:

    But could we enter a period of reverse innovation like how the Romans forgot how to build canals, the Egyptians forgot how to read hyroglyphics, & the Greeks forgot how to make computers? Every time people have lost their jobs, we’ve expected the government to lower the standards required to get a job, for 90 years. Declining SAT scores tell a tale of each generation being less able to learn than the previous generation.

  7. Dave H. says:


    A true scientist knows that there is no such thing as “settled science”. Perhaps you knew of the current effort to define the kilogram, a basic unit of mass which in turn defines many other measurements. There was an article about this in today’s paper; those interested in learning about it can search in on their own…or they can choose knee-jerk reactions and argue.
    Those in the metrology field know all about “uncertanties” and the never-ending efforts to constantly redefine them. IPTS-48, IPTS-68, and IPTS-90 are necessary due to periodic redefinition of the Volt.

    Einstein was weak on thermodynamics, and for that we are all grateful and alive! One head cannot contain all wisdom, it is written. Marconi had no idea how his signals were crossing the Atlantic, did he? Just as the physics of two centuries ago seems primitive to us today so shall OUR physics seem primitive two centuries from now. This is how civilization progresses; by never accepting the status quo; by always asking “why” and “how” and using its tools to answer those questions…for today.
    As the tools improve, so does our understanding. Anyone remember when the first generation Pentium microprocessor was found to have a flaw only revealed when used for astrophysics? It forced Intel to build a better microprocessor.

    “Gravity” may someday fall into the same category as “ether”, but only after humanity has learned as much about it as we today know about radio and electromagnetism.

    I tip my hat to the cadres of dedicated scientists who roam the halls of NIST, in search of ever-fewer uncertanties. Even the Steam Tables are not sacrosanct!

    • Michael Wright says:

      “I tip my hat to the cadres of dedicated scientists who roam the halls of NIST, in search of ever-fewer uncertanties. ”

      And also spend a lot of time maintaining standards of metrology which seems very tedious (and to many really boring) and typical day has no action and adventure like NASA jobs are portrayed in the movies.

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