Science education

Is Big Bang “Just a Theory?”

An article was posted on the National Science Teachers Association’s LinkedIn group reporting the result of an AP poll which measured Americans’ “scientific literacy.” I’ll show some of the comments on that article, then I’ll write the article I posted on the big bang “theory,” which I hoped would clarify the meaning of a scientific “theory.” First the comments:

Galaxy E1405568300218 1334106“Why should we not give children the opportunity to hear all sides of a story and allow them to choose in which they believe? Scientist cannot prove evolution, they can present evidence that leads us to believe that evolution occurred.”

“I have a wonderful friend who is a Christian, but also a scientist. He has a Phd. in Environmental Studies. Is he illiterate because he does not support the THEORY of evolution, the theorized age of the earth, or the Big Bang?”

“As for the Big Bang Theory, it assumes you can arbitrarily ignore the law of conservation of energy, … You have to read everything critically to satisfy your own assumptions about what is real or not.”

“Are you serious? You think people are scientifically illiterate if they don’t believe that humans are the major cause of global warming? Or if they don’t believe that scientists really KNOW how old the earth is? Or if they don’t believe in the big bang theory?”

“O, and by the by, the Big Bang Theory is, by definition, a theory.”

“… all explanatory science is theory. Scientific laws are just theories with the most compelling evidence.”

“Science is based upon theories so why should school systems ram theories at my child as being the absolute truth?”

“Stating that questioning “The Big Bang Theory”, which is a THEORY and not a FACT, is scientific ignorance is, well…… ignorant.”

“If large percentages … don’t accept the theories, then maybe they aren’t well established scientific theories.”

“As with any theory such as the Big Bang, it is actually scientifically healthy to question its validity.”

“The fact that people question the Big Bang THEORY says nothing about their scientific intelligence. It is after all, still a THEORY.”

“Of course people question the Big Bang theory, it’s a theory!”

“Hold it right there Captain Kirk. Are you saying that The Big Bang theory is a scientific fact now?”

“”51% question the Big Bang Theory. That is why it’s called a “theory”.”

“Well for one the big bang theory isn’t exactly proven …”

– – – – – – – – – – – – – – – – – – – – – –

And here is my article on the big bang.

I read almost all the comments to Kirk Englehardt’s post concerning Americans’ scientific illiteracy. Having taught various versions of a “science literacy” course at a public university for over twenty years, I have acquired a good grasp of the nature of the illiteracy and some of its causes. Many of the comments were affirmations of the findings of the Associated Press poll, and many more regarded big bang as a theory, with the common meaning of the word. I’ll not address individual comments nor even individual misconceptions common to most comments. I’ll simply concentrate on this “theory” in the hope that my discussion elucidates the word when applied to science, in particular physics, my field.

Big bang was a PREDICTION of another “theory,” Einstein’s general theory of relativity (GTR). When he and a Russian physicist applied that theory in the early 1920s to the whole universe – assumed to be a gas, each molecule of the gas a distant galaxy – they found that this “gas” must be expanding, and when Hubble OBSERVED this expansion in the late 1920s, the prediction gained more and more acceptance. A time-reversed expansion is compression, and the general THEORY of relativity predicts that this compression continues all the way to a space-time point at a finite time in the past … and gives a mathematical equation for this time which contains parameters to be measured by observation.

Therefore, those in the group who called the big bang “just a theory,” should apply the word to GTR. Is GTR “just a theory?” Einstein wrote his GTR equation in 1916, which predicted many other phenomena beside the big bang: bending of light grazing the sun (confirmed by observation), precession of the perihelion of Mercury (confirmed by observation), gravitational lensing (confirmed by observation), collapse of a star and forming either a red giant (confirmed by observation), or a super nova (confirmed by observation), slowing down of time in gravity (confirmed by observation). The last item is crucial in the operation of GPSs. The reason that a GPS works is because GTR is right! So, quite literally, every time you use your GPS, you are testing GTR (and the special theory of relativity). YOU may call it “just a theory,” but your GPS tells you otherwise!

A scientific theory can be disproved only by OBSERVATION, not by Rupert Sheldrake writing a book on science delusion and proclaiming – without any evidence – that science, en masse, is wrong. Nature, to paraphrase Einstein, is a benevolent DICTATOR. Only nature can disprove our conception of it. No opinion, thought, belief, legislation, freedom of speech, and amendments thereof can say whether nature is right or wrong. If there is ANY legitimate observational evidence that disproves GTR, physicists will be the first to abandon it. However, science doesn’t work that way. Since any scientific theory explains certain observations done in a limited domain, we cannot simply abandon it in light of contradiction with observations done in a NEW domain. We can’t say that the Newtonian theory of gravity is wrong … because it works excellently when describing the solar (or any other star) system and it is the theory used by NASA every time it launches a satellite into orbit. However, Newtonian gravity fails when applied to extreme cases of very strong gravitational fields in which objects could move at nearly light speed. So, the person who commented that classical physics was wrong, is wrong!

Back to the big bang! After a lull of about forty years, interest in the implication of a compressed universe was revived in combination with nuclear and particle physics – which did not exist in the 1920s. Nuclear physics calculations plus the observational evidence that most of the visible universe consists of only the two lightest elements, hydrogen and helium, pointed to the existence of a background radiation in the early universe, whose present temperature was estimated to be around 10 degrees Kelvin. Quite independently and accidentally, two radio astronomers saw this radiation in 1964 and measured its temperature to be around 3 degrees Kelvin. COBE satellite, launched in 1989, refined the measurement and found the temperature to be 2.725 degrees Kelvin. On March 23, 2013 using a combination of “theories” and experiments, the age of the universe was measured to be 13.798(0.037) billion years.

So, is the big bang “just a theory?” You have the right to say so, just as you have the right to say that night is day and day is night! However, every observation since 1916 has confirmed the predictions of GTR, including big bang and the operation of GPS. The measurements are improving – not rejecting previous measurements – and each improved measurement confirms even better, the predictions of GTR. The theory is not complete because it is limited to large scale phenomena. We have not been able to apply it to small phenomena such as the very moment at which big bang occurred. There are two ways to treat this situation. One is the way one commenter treated it: the big bang violates energy conservation, so forget it! The other way is how a scientist treats it: we don’t know how big bang itself happened, although we can describe very well how the universe evolved from 10-30 second after the big bang to the present. We also know that the answer to the creation of the universe lies in the unification of gravity and quantum theory … the most challenging problem in the history of physics.

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