Into the Impossible With Brian Keating - How Big is the Universe? It’s Debatable… An Essay By Brian Keating (#085)

Episode Date: October 27, 2020

The GREATEST Debate: How two astronomers changed the way humanity debates By April 1920, the Spanish flu had claimed 50,000,000 lives. The first World War ended only 17 months earlier. A polarizing presidential election was underway. On April 26, 1920, in Washington DC, two contestants took the stage in a debate that would alter the cosmos forever. Was this contest the 1920 presidential debate? No, this battle was literally for universal domination, not a mere skirmish between presidential contenders Warren Harding and James Cox. Only the wonkiest history buffs recall who won 1920’s presidential debates. But every astronomer knows the two scientists sparring on that April evening at the Smithsonian Museum of Natural History, taking sides in astronomy’s “Great Debate”: Heber Curtis, director of the Allegheny Observatory, versus Mt. Wilson Observatory astronomer Harlow Shapley. The Debate’s outcome could not have been more consequential; the span of the entire universe was at stake. This epic contest concerned the nature of the so-called “spiral nebulae” that had vexed astronomers since Lord Rosse first pointed his 54-foot long telescope, appropriately nicknamed ’the Leviathan’, toward the heavens in 1845. Seventy-five years later, Shapley claimed these diaphanous swirls of light were our neighbors within the Milky Way, a mere hundred or so light years away. Curtis contended that some of these smudges were galaxies in their own right, assemblies of hundreds of billions of stars. If Curtis was right, these ’nebulae’ resided at truly astronomical distances from Earth. Curtis and Shapley decorously dealt philosophical punches. No mute buttons were needed. But lacking physical evidence, the Great Debate ended in a draw. The runoff would put the aftermath of the 2000 presidential election, and its ‘hanging chads’, to shame. It took over three years until Edwin Hubble discovered a curious cosmic beacon on the outskirts of the “Great Spiral Nebula” in Andromeda. This luminary, a class of star known as a Cepheid variable, periodically waxed and waned in brightness about twice per week. Years earlier, the brilliant astronomer Henrietta Leavitt showed that the rate at which Cepheid stars pulsated could be used as a sort of “cosmic ruler”, surveying distances far beyond Earth. Applying Leavitt’s Law (as we now call it), Hubble determined the Andromeda “nebula” was incomprehensibly distant—2,540,000 light-years to be exact. The Milky Way was large, but its diameter was known to be less than 10 percent of that vast span. Andromeda was not in our galaxy, it was a galaxy, hosting 100 billion or more suns of its own. The Great Debate was settled. Shapley lost, but was humble in defeat, encouraging Hubble to widely publicize his findings. It wasn’t only the distance to the Andromeda galaxy that had grown, humanity’s perspective was forever broadened, tempered with newfound humility amidst the vastness of intergalactic space. Today, instruments like the Hubble Space Telescope, celebrating its 30th anniversary, have magnified the Great Debate’s significance, revealing that the Milky Way and Andromeda are two of as many as two trillion galaxies. What future debates will be waged in astronomy’s next century, using instruments (costing a mere fraction of modern presidential campaigns), such as the Simons Observatory, the Vera Rubin Observatory, the Xenon Dark Matter Project, and more? Will we learn that dark matter is a mysterious new particle or the effect of an unknown new force? Will we spot life on exoplanets, or discover that we truly are alone in the cosmos? Perhaps we will even find evidence that ours is not the only universe—just some of modern astronomy’s “Great Debates.” One of the most refreshing aspects of astronomy is that it is inherently apolitical. There are no Democratic comets, no Republican asteroids. Pe Learn more about your ad choices. Visit megaphone.fm/adchoices

Any sufficiently advanced technology is in distinguishing from magic. Hello, I'm Professor Brian Keating, Chancellor's Distinguished Professor of Physics at the University of California, San Diego. And this is my essay entitled Washington's Greatest Debate, How Two Astronomers Change the Way Humanity Debates Forever. By April 1920, the Spanish flu had claimed 50 million lives worldwide. The First World War had ended only 17 months earlier. a polarizing presidential debate was underway. On April 26th in Washington, D.C., two contestants took the stage in a debate that would alter the cosmos forever. Was this contest the 1920 presidential debate?

No, this battle was literally for universal domination, not a mere skirmish between presidential contenders, for the record, Warren Harding and James Cox. Only the won won won't history buffs recall who won 1920s presidential debates, But every astronomer knows the two scientists sparring on that April evening at the Smithsonian Museum of Natural History, taking sides in astronomy's great debate. They were Heber Curtis, director of the Allegheny Observatory, versus Mount Wilson Observatory Astronomer Harlow Shapley. At first, I didn't think it was real. I woke up to this blinding light, and I was transported to another place. Pluto TV!

Then I heard a voice. Come with me if you want to live. There were thousands of movies and shows, and they were all free. The truth is our scene. It's just so beautiful. On Pluto TV, free streaming of Terminator 2, Fringe Arrow, the 100 NX files may cause excitement, loss of sleep, and sudden belief in extraterrestrials. No credit cards or alien encounters necessary. Pluto TV, stream now, pay never.

The debate's outcome could not have been more consequential. The span of the entire universe was at stake. This epic contest concerned the nature of the so-called spiral nebulae. that had bexed astronomers since Lord Ross first pointed his 54-foot-long telescope, appropriately nicknamed the Leviathan, towards the heavens in 1845. 75 years later, in Washington, D.C., Shappley was claiming that these diaphanous swirls of light were our neighbors in the Milky Way, a mere hundred or so light years, to be exact. But Curtis contended that some of these smudges were galaxies in their own right,

assemblies of hundreds of billions of stars. If Curtis was right, these nebulae resided at truly astronomical distances from the earth. Curtis and Shapley decorously dealt philosophical punches. No mute buttons were necessary, but lacking physical evidence the great debate ended in a draw. The runoff would put the aftermath of the 2000 presidential election and its hanging chads to shame. It took over three years until Edwin Hubble discovered a curious beacon on the outskirts of the quote, great spiral nebula, unquote, in Andromeda, this luminary, a class of star known as a sepheid variable, periodically waxed and waned in brightness about twice per week.

Years earlier, the brilliant astronomer, Henrietta Swan Levitt, had showed that the rate in which the sephid stars pulsed could be used as a sort of cosmic ruler, surveying distances far beyond the earth. Applying Levitt's law, as we now call it, Hubble determined that Andromeda nebula was incomprehensibly distant. 2.54 million light years away to be exact. The Milky Way was known to be large, but even back then, its diameter was known to be less than 10% of that vast span. Andromeda was not in our galaxy.

It was a galaxy, hosting perhaps a hundred billion or more sons of its own. The great debate was settled. Shapley lost, but he was humble in defeat. He even encouraged Hubble to widely publicize his findings. It wasn't only the distance to the Andromeda galaxy that had grown, humanity's perspective was forever broadened, tempered, with newfound humility against the vastness of intergalactic space.

Today, instruments like the Hubble Space Telescope, currently celebrating its 30th anniversary, have only magnified the significance of the great debate, revealing that the Milky Way in Andromeda are but two of as many as possibly two trillion galaxies, each hosting hundreds of billions or maybe trillions of stars in their own right? What future debates will be waged in astronomy's next century using instruments, costing a mere fraction of today's presidential campaigns, such as the Simons Observatory, the Vera Rubin Observatory,

and the Xenon Dark Matter Project? What will they discover? Perhaps we'll learn that dark matter is a mysterious new particle, or maybe we'll learn that it is instead the result of an unknown new force. Will we spot life on exoplanets or even? even in planets within our own solar system? Or will we discover, once and for all, definitively, that we are truly alone,

the only life form in the cosmos? Perhaps we'll even find evidence that ours is not the only universe, just some of modern astronomy's current great debates. One of the refreshing aspects of astronomy is that it is inherently apolitical. There are no democratic comets, no Republican asteroids. Perhaps that's what explains the great debates comity. despite its cosmic stakes.

Great debates ennoble us, deepening our appreciation of nature's beautiful tapestry. The significance of a debate should not be judged by who won, for not all contests need to be zero-sum games. Rather, debates should be appraised by the equality of the questions we pose. Honestly, debating great mysteries, always prepared to change our mind, or even concede our opponent's point of view,

as did Shappley if new evidence surfaces. That not only makes us better scientists, it makes us better citizens as well. Besides, from the cosmic perspective, political victories are fleeting. Warren Harding's administration lasted barely two years. Sadly, he died two months before Edwin Hubble settled the great debate for good. Time will tell if today's political debates are even remembered a decade, let alone a century from now. But the universe and our perceived place within it abides forever. Or does it?

It's debatable. Any sufficiently advanced technology is indistinguishable from magic.