[The] Big Bang hypothesis … is an irrational process that cannot be described in scientific terms … [nor] challenged by an appeal to observation. ~ Fred Hoyle (1949)
We are at the cusp of becoming a truly space-faring species. Space X, a private space firm headed by Internet entrepreneur Elon Musk, made history in 2012 by winning a major NASA contrac – effectively replacing the retired shuttle program by demonstrating that his private rocket technology could cost-effectively ship people and goods into Earth orbit. Another private effort may mine nearby asteroids for critical resources. Yet another private effort may put a human colony on Mars by the early 2020s.
Even though the U.S. space program has moved away from manned missions, it is still pursuing aggressive robotic exploration programs for Mars and other stellar bodies. At the same time, nations like China are quickly trying to catch up with Western space programs.
It’s extremely exciting to contemplate the next obvious steps in our race to the stars: establishing permanent colonies on Mars, the moon, and other objects in our solar system. Eventually we’ll make it to Alpha Centauri, the nearest star system to us and – at some point in the not-too-distant future – we will probably spread out to the rest of our Galaxy.
It is not, then, premature to consider deeply what our universe looks like, where it came from, and where it’s going. This is what constitutes cosmology – the science of the largest scales of space and time.
Even as someone with no formal training in cosmology, I feel comfortable stating that the mainstream big bang cosmology (BBC) has some serious problems.
Dark matter appears to be an ad hoc addition to general relativity, our prevailing theory of gravity. Today, many decades after it was originally proposed, there is still almost zero hard evidence for dark matter, despite ongoing vigorous efforts to discover exactly what constitutes dark matter. (Dark energy, the posited force behind the accelerating expansion of the universe, is also somewhat fishy, but seems to me to have a better theoretical basis than dark matter.)
These reasons and more have impelled me to explore alternative cosmologies and reach out to the physicists I’m interviewing for this series. Part I of this series explored the ideas of Reg Cahill and his process physics. Cahill’s ideas contravene many key concepts of the big bang cosmology, most importantly the idea that the speed of light is absolute, a key postulate of Einstein’s theories of relativity. From this difference alone, a very different cosmology results.
Part II explores the quasi steady-state cosmology developed primarily by Fred Hoyle, Geoffrey Burbidge, and Jayant Narlikar, as a successor theory to the steady-state cosmology. The original steady-state cosmology, which was the primary challenger to the big bang theory during the middle part of the 20th Century, faced many difficulties with various observations in the second half of that century – prompting development of the quasi steady-state cosmology as a replacement during the 1990s. Narlikar has been integrally involved with developing both theories since the 1960s.
I enjoyed Narlikar and Burbidge’s book, Facts and Speculation in Cosmology, a lot. It’s accessible to lay readers but also presents more in-depth information challenging some of today’s widely-accepted ideas about cosmology. They even suggest that one of the fundamental concepts in modern cosmology, Hubble’s law, which relates redshift to acceleration (the more redshift observed in the spectrum of distant stars, the faster they are moving away from us), may actually be wrong.
Narlikar earned his PhD from Cambridge University under Fred Hoyle, is past president of the Cosmology Commission of the International Astronomical Union, is a senior faculty member at Cambridge and other institutions, and author of a number of textbooks in cosmology. He now lives in India. I interviewed Narlikar via email.
Is cosmology a mature science yet? It seems to me, in reading fairly widely in cosmology over the years, that a lot of theories rest on speculation. This is of course a key theme of your book, which references “speculation” in its title.
Cosmology, as widely studied today via the standard model [big bang cosmology], is not a mature scientific subject. It rests on very few direct facts and a lot of speculation. That is why I have compared it with the Pythagorean “central fire hypothesis,” which suggested (we now know wrongly) that there was a large source of heat and light – that was not the Sun – around which the Earth, Sun, and other planets orbited.
Despite the widely held view that the big bang cosmology (BBC) rests on firm observation and theory, you strongly criticize this theory in your book, Facts and Speculation in Cosmology. Could you outline your key objections the BBC?
Let us see what the observations actually are and how they are interpreted. QSSC here stands for the quasi steady-state model of cosmology, which is our (Hoyle, Narlikar, Burbidge) alternative cosmology. Here are the key observations.
The cosmic microwave background radiation spectrum is well-established through observation, but where does the radiation come from? To say that it is a relic from an epoch of redshift 1000 is a speculation based on the BBC. It cannot, therefore, be seen as testing the BBC. At best, it provides a consistency check of the BBC. An alternative cosmology like the quasi steady-state cosmology provides another viable interpretation of the radiation as relic starlight thermalized from previous expansion/contraction cycles of the universe, discussed further below.
In the period 1960-80, the redshift to magnitude (m-z) relation for galaxies indicated a decelerating universe. The only other serious cosmology in the field then, the steady-state cosmology, was rejected because it implied an accelerating universe. Post 1998-99, as soon as the supernova data showed that an accelerating universe was consistent with this new data, the BBC supporters changed gears and began to champion the accelerating universe model.
The non-baryonic [baryonic matter is what everything in our normal experience is made of] dark matter postulated in BBC is primarily intended to prop up the BBC against possible disproof involving deuterium abundance and large inhomogeneities of the cosmic microwave background radiation. It has not been detected astronomically nor have accelerators found evidence of dark matter, let alone any observation demonstrating that it constitutes 23% of total matter-energy content in the universe, which is the mainstream view. Yet the idea of dark matter is uncritically accepted to this day.
Last, the inflationary epoch [based on the idea that the very early universe expanded extremely rapidly to almost its present size in the blink of an eye] has been accepted without there being a mathematical model to explain its driving Φ (phi) function, or without its coming naturally from a fundamental particle physics theory. Inflation theory ‘works’ when the numbers in this function are put in by hand [that is, ad hoc]. This does not add credibility to the BBC.
You, your co-author, Geoffrey Burbidge, the British physicist Fred Hoyle, and others, have since the 1990s advocated the quasi steady-state cosmology (QSSC) alternative to the big bang – quasi steady-state cosmology being a modification of the steady-state cosmology that has since been abandoned due to disagreements with observation. Do you still advocate quasi steady-state cosmology? What are the key advantages of this theory over the BBC? What observational evidence would provide compelling arguments in favor of quasi steady-state cosmology rather than BBC?
I still advocate the quasi steady-state cosmology based on the following key observations. quasi steady-state cosmology gives an alternative origin of the cosmic microwave background radiation as relic starlight thermalized from previous cycles. It predicts the observed temperature as 2.7K, which BBC cannot. In the BBC, this figure is put in “by hand,” that is, rather than emerging naturally from the theory. The supernova magnitude to redshift (m-z) relation is explained by quasi steady-state cosmology without invoking an accelerating universe. Moreover, the intergalactic dust postulated for explaining this result turns out to be the same as needed for the cosmic microwave background radiation. The origin of this dust is also explained astrophysically, unlike the mysterious nonbaryonic dark matter postulated by BBC supporters!
Specifically, the quasi steady-state cosmology suggests the presence of intergalactic dust in the form of iron needles, which thermalize starlight to produce the cosmic microwave background radiation. Laboratory experiments have shown that when metallic vapours cool they condense as solid needles rather than as balls. These needles are highly effective absorbers and radiators at wavelengths around a millimeter, so their expected abundance in the universe around 10^-34 gram per cubic centimetres produces a thermalized cosmic microwave background radiation. The same dust absorbs radiation from distant supernovae, making the supernovae appear dimmer than nearby ones. Notice that the needles get formed when supernovae eject iron vapour and thus we have a perfect source of absorbers. By contrast, the BBC has no theoretical basis for the origin of nonbaryonic dark matter. In terms of observational evidence to falsify the BBC, I am looking for strong evidence of stars at least 20 billion years old. If these very old stars are found, there will be an obvious problem for BBC. Likewise, modest blueshift (less than 0.1) is expected for very faint (distant) galaxies under the quasi steady-state cosmology. These are some of the key observational possibilities to distinguish between the quasi steady-state cosmology and the BBC.
How would we identify stars 20 billion years or older? If we did, do you think many BBC advocates would be persuaded that BBC has been falsified?
On the Hertzsprung-Russell diagram, which plots stars with surface temperature on the x-axis and luminosity on the y-axis, such stars will show up on a ‘giant branch’ turning off from the main sequence (which has the Sun on it) at a height well below the normal giant branch. These stars are interpreted as less massive and are, accordingly, slow burners of hydrogen in their core. So their position on a giant branch means they have finished burning their hydrogen fuel. This allows us to estimate their age and that could be as high as 20 billion years.
BBC advocates will likely try to interpret such evidence differently, such as assuming that the sample is redder because of contamination by dust. We previously had one such very old star sample from the Hubble telescope archives but we could not rule out the interstellar reddening. So we are back to the drawing board looking for other candidates for very old stars.
On a similar note, is the BBC falsifiable even in principle? Aren’t large meta-theories like BBC fundamentally unfalsifiable and therefore not truly scientific? Isn’t this a classic case of Kuhnian paradigm formation and (possible) destruction – if enough data does eventually accrue that the BBC has been falsified?
BBC has previously been shown to be inconsistent with observations but it has survived by changing its parameters. I assume this cannot go on forever!
You discuss at the end of your book a number of red-shift anomalies, such as nearby galaxies with very contrasting redshifts – which shouldn’t happen under the BBC’s accelerating universe concept. You also discuss the possibility that we may be misunderstanding at a fundamental level what causes redshift. In other words, you assert that Hubble’s Law, which is considered fundamental to cosmology, may be wrong. This would be a huge paradigm shift for physics if it were true. Do you think explanations such as inter-stellar dust or the “tired light” hypothesis may in fact be right when it comes to explaining redshift?
I would urge the conventional observers to closely observe the important cases of anomalous redshifts. If they cannot get rid of the anomalies, then paradigm shift will have to come eventually.
How much do you think the fact that the Western world is still largely Christian, particularly in terms of cultural heritage, affects willingness to accept the BBC? Big bang cosmology is of course very different than the Biblical story of creation, but the commonality is creation itself, a start to all things. Your preferred alternative, to the contrary, suggests an eternal universe with no beginning and perhaps no end.
I think the three religions that originated in the Middle East somehow make it easier to believe in a universe that was created at some moment of time, as in the BBC. So there may be something in what you suggest. Hinduism and Buddhism, on the other hand, seem comfortable with a universe without a beginning or end. But this division of opinion is not a hard and fast one!
Another “eternal universe” model that I’ve studied a little is known as plasma cosmology and it was developed by Nobelist Hannes Alfven, Erik Lerner, and others. The basic idea is that since the large majority of the visible universe is plasma (all stars are plasma), then plasma physics should hold sway at the macro level in the same way as we can observe in labs or in stars. Accordingly, electromagnetism becomes more important at the cosmic scale than gravity. What are your views on plasma cosmology?
I have not studied it in sufficient depth to be able to answer this question. But I do not know how the cosmic microwave background radiation is formed in the plasma cosmology universe.
The “cosmological principle” (which asserts that we shouldn’t think of ourselves as special and, accordingly, the universe should look pretty much the same from where we are in the universe as anywhere else in the universe) is an assumption built into the BBC. It’s kind of a reverse Ptolemaic principle. You criticize this principle as not going far enough, in terms of not including the temporal dimension. You suggest that the “perfect cosmological principle” should be adopted, which holds that the universe looks essentially the same in different epochs. But isn’t this new principle contradicted by quasi steady-state cosmology because the universe is still considered to be expanding in quasi steady-state cosmology? Moreover, why should the universe look the same from different locations in space and time? Our common sense suggests that things are indeed asymmetrical in time and space, so why not at the cosmic scale too?
As a supporter of the original steady state cosmology (SSC) [Narlikar was one of the developers of this earlier theory, which was for some time a serious competitor to the big bang model] one is tempted to believe in the perfect cosmological principle (PCP). When we (myself, Fred Hoylem and Geoffrey Burbidge) gave up on the steady-state cosmology and generalized our model to the quasi steady-state cosmology, we realized that the perfect cosmological principle has to apply on a longer time scale. The quasi steady-state cosmology has a long-term expansion as per the perfect cosmological principle, and superposed on it are short-term oscillations of cosmological expansion and contraction. Thus the applicability of the perfect cosmological principle is on a very large scale, just as the spatial cosmological principle applies on a large spatial scale.
In January of this year, a research group led by Roger Clowes announced a discovery of the largest structure ever discovered in the universe: a cluster of about 70 quasars (“quasi stellar objects”). This cluster is about 40,000 times larger than our own Galaxy and the research team that discovered it suggests that it contradicts the cosmological principle because it shows that at the largest scale, the universe is not in fact homogeneous. Do you agree or is it premature to call the cosmological principle falsified?
One could argue that there exist larger inhomogeneities than superclusters. Since the Hubble radius of the universe is around 10 billion light years, in the Clowes example their quoted size is coming close to the above limit, thus making the cosmological principle suspect.
Thinking on longer timescales about the future of humanity, when do you see us venturing out beyond our solar system to explore our Galaxy and, eventually, other galaxies? What are the most promising technologies for this leap from little old Earth to the wider universe?
So long as the special theory of relativity is valid, even if we travelled with light speed to the centre of our Galaxy, we will take around 30,000 years to go there and an equal interval to come back. Apart from the logistics of keeping the astronauts living over such long periods, we will not get any benefit from their excursion for we would be long dead before they come back! Our best chance is SETI using radio signals.
Last, what do you see as the most pressing problem(s) in cosmology and physics today?
We need to understand the basic physics at very small scales; then we need to understand where all the matter we see in the universe came from. These are difficult questions and I do not share the enthusiasm of cosmologists and particle physicists that we are very close to the answer.