commentary Benefits of diversity Abraham Loeb Discoveries in astronomy — or, in fact, any branch of science — can only happen when people are open-minded and willing to take risks. ccording to Mark Twain, “It ain’t used it to discover the expansion of the weak, as most of the X-ray sources would what you don’t know that gets you Universe. It was surpassed in 1948 by the be flaring stars. The launch of an X-ray Ainto trouble. It’s what you know for 200 inch telescope at the Mount Palomar telescope by NASA was therefore delayed sure that just ain’t so.” This illustrates a very Observatory in California, which played a by half a decade, after which astronomers common flaw astronomers have, which is to key role in the discovery of radio galaxies discovered X-ray emission from numerous believe that they know the truth even when and quasars and in studies of the other sources, such as accreting black holes data are scarce. This fault is the trademark intergalactic medium2. Clearly, bigger and neutron stars, supernova remnants and of a data-starved science. It occasionally telescopes continued to benefit astronomy galaxy clusters. leads to major blunders by the scientific as technology improved. community causing the wrong strategic Dark matter. In the early 1970s decisions, and bringing about unnecessary Composition of the Sun. While Jerry Ostriker gave a talk at the California delays in finding the truth. Let me illustrate working on her PhD thesis in 1925, Institute of Technology describing the this phenomenon with ten examples, in Cecilia Payne-Gaposchkin (who became case — developed by him in collaboration chronological order. the first to be awarded a PhD in Astronomy with Jim Peebles and Amos Yahil — for at Harvard-Radcliffe) interpreted the solar spiral galaxies having dark matter haloes Large telescopes. In 1909, spectrum based on the Saha equation that comprise most of their mass6. Members Edward Charles Pickering, who served and concluded that the Sun’s atmosphere of the audience were contemptuous as director of the Harvard College is made mostly of hydrogen. During the of the idea and dismissed it as wild Observatory from 1877 until 1919, argued review of her dissertation, the distinguished theoretical speculation. that telescopes had reached their optimal Princeton astronomer Henry Norris Russell size of 50–70 inches and there was no convinced her to avoid the conclusion that Gravitational lensing. Around 1980, advantage to be gained from seeking larger the composition of the Sun is different from shortly after the discovery7 of the first apertures. In December 1908, in an article that of the Earth, as it contradicted the gravitational lens (QSO 0957+561 A/B), titled ‘The Future of Astronomy’, he wrote1: conventional wisdom at the time3. Ed Turner at Princeton University was advised by a highly distinguished “It is more than doubtful, however, whether a Maser and complex molecules. When astronomer not to spend much time further increase in size is a great advantage. Charlie Townes worked on his experimental working on gravitational lenses because Much more depends on other conditions, demonstration of the maser in 1954, two they would turn out to be useless especially those of climate, the kind of work to Nobel laureates, Isidor Isaac Rabi and curiosities. For a few years, lenses were be done and, more than all, the man behind Polykarp Kusch, tried to stop him by widely regarded by astronomers as the gun. The case is not unlike that of a saying4: “Look, you should stop the work unimportant and it was almost impossible battleship. Would a ship a thousand feet long you are doing. It isn’t going to work. You to get observing time or grants to always sink one of five hundred feet? It seems know it’s not going to work, we know it’s study them. as if we had nearly reached the limit of size of not going to work. You’re wasting money. telescopes, and as if we must hope for the next Just stop!” Three months later, the maser Cosmology. Around 1990, during my improvement in some other direction.” worked. Similar circumstances repeated term as a postdoctoral fellow at Princeton, when Townes was determined to discover I asked a prominent astronomer from Pickering’s blunder led to a major blow for complex molecules in space and experienced another prestigious academic institution observational astronomy on the east coast of resistance from astronomers who argued whether they would consider hiring junior the USA. On the west coast, just before that the interstellar gas density is so low and faculty in the field of theoretical cosmology. Pickering’s article was published, the ultraviolet illumination so intense that He replied: “we might contemplate this George Ellery Hale obtained first light on any surviving molecules would be too scarce possibility if we could only convince the 60 inch telescope at Mount Wilson to be detectable5. ourselves that cosmology is a science”. Two Observatory in California, which became years later, in 1992, the COBE satellite one of the most productive telescopes in X-ray astronomy. In the early 1960s a reported the detection of microwave astronomical history. Around the same panel of experts was assembled by NASA background anisotropies8. time, Hale received funding from to evaluate the merits of a proposal to John Hooker and Andrew Carnegie to launch an X-ray telescope into space (as High-redshift galaxies. Piero Madau at create a larger telescope. The 100 inch the Earth’s atmosphere blocks X-rays). the University of California, Santa Cruz, telescope was completed in 1917; The panel concluded that the scientific once told me that he had great difficulties Edwin Hubble and Milton Humason later motivation for an X-ray space telescope was publishing a paper he wrote in the 616 NATURE PHYSICS | VOL 10 | SEPTEMBER 2014 | www.nature.com/naturephysics © 2014 Macmillan Publishers Limited. All rights reserved commentary mid-1990s on intergalactic absorption and the announcement of the discovery of agencies should dedicate a fixed fraction the colours of high-redshift galaxies because 51 Peg b in 199511 and after others had of their resources (say 10–20%) to risky the referee kept arguing: “we all know that found similar examples. As it turns out, explorations. This can be regarded as there are no normal galaxies above a redshift Otto Struve had already suggested12 in affirmative action to promote a diversity of of two”. 1952 that close-in planets may exist and ideas, which is as important for the progress would be easy to find through both radial of science as the promotion of gender and Kuiper Belt objects. David Jewitt at the velocity and transit observations, but his ethnic diversity. ❐ University of California, Los Angeles, paper was completely ignored because of could not get telescope time or funding theoretical priors. Abraham Loeb is in the Department of Astronomy, for attempts to detect the conjectured Harvard University, 60 Garden Street, Cambridge, population of Kuiper Belt objects9. He used These examples and many more like Massachusetts 02138, USA. observing time and funding he received for them (starting with the ancient view that e-mail: [email protected] other projects until he finally discovered the Earth is at the centre of the Universe the first of these objects in the outer Solar and that the Sun revolves around it), References 1. Pickering, E. C. Pop. Sci. Mon. 75, 105–116 (1909); System with Jane Luu in 1992, using the demonstrate that progress in astronomy can http://go.nature.com/SfXnMR 88 inch telescope at Mauna Kea, Hawaii. be delayed by the erroneous proposition 2. http://www.astro.caltech.edu/palomar/history.html that we know the truth even without 3. Padman, R. Cecilia Payne-Gaposchkin (1900–1979) (Needham College, 2010); http://go.nature.com/QPaUjS Close-in Jupiters. The first planets ever experimental evidence. Lapses of this type 4. Hora, H. & Miley, G. in Edward Teller Lectures: Laser discovered around a main sequence star can be avoided by an honest and open- and Inertial Fusion Energy (eds Hora, H. & Miley, G.) other than the Sun had masses similar to minded approach to scientific exploration, 4 (Imperial College Press, 2005). 5. Townes, C. H. in Revealing the Molecular Universe: One Jupiter but were orders of magnitude closer which I label as having a ‘non-informative Antenna is Never Enough (eds Backer, D., Moran, J. & Turner, J.) to their host star than Jupiter is to the Sun. prior’ (known as a Jeffreys prior in Bayesian 81 (ASPC, 2006). This can be simply understood as a selection statistics). This unbiased approach, which is 6. Ostriker, J. P., Peebles, P. J. E. & Yahil, A. Astrophys. J. effect, because the reflex motion of a star common among successful crime detectives, 193, L1–L4 (1974). 7. Walsh, D., Carswell, R. F. & Weymann, R. J. Nature due to a close-in planet is much easier to gives priority to evidence over imagination, 279, 381–384 (1979). detect than the motion induced by a distant and allows nature itself to guide us to 8. Smoot, G. F. et al. Astrophys. J 396, L1–L5 (1992). planet. But because Jupiter is considerably the correct answer. Its basic premise is 9. Jewitt, D. Astronomy Beat 48, 1 (2010). 10. Latham, D. W. et al. Nature 339, 38–40 (1989). farther out from the centre of the Solar humility — the recognition that nature is 11. Mayor, M. & Queloz, D. Nature 378, 355–359 (1995). System, time allocation committees on much richer than our imagination is able 12. Struve, O. The Observatory 72, 199–200 (1952). major telescopes declined proposals to to anticipate.