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Home , Bell Labs, Radio telescope

TJO Newsletter Summer 2017

THE IS HISSING AT US By Locke Patton

This story doesn’t start with a . It starts was in fact an astrophysical phenomenon coming from with an unrelenting hiss from the universe. In 1960, Bell beyond our in need of an explanation. Labs built a horn , a in Holmdel, They called theorist Robert Dicke, New Jersey. It was 20 feet long and hypersensitive to worked nearby at Princeton University. His focus radio signals, on the low-energy side of the was on the newest hot topic in at the time: the spectrum of . Scientists kept the detector cooled to Big Bang theory. Recent observations showed that only 4 degrees Kelvin above absolute zero using liquid galaxy clusters – the visible parts of our universe – were nitrogen – the equivalent of cooling your freezer down to flying away from each other. In other words, the fabric of -269 ºC. Working with the incredibly sensitive data, the universe – space itself – was expanding at an Robert Wilson and Arno Penzias discovered a accelerating rate and carrying matter along for the ride! background noise, much like the static you might have This contradicted even Einstein: the universe heard in your car radio, except this was persistent was not in fact a static steady-state universe. Instead, as and uniformly coming from all visible portions of the sky. you roll back time, all objects in the universe fly together, Furthermore, the microwave strength was 100 times becoming more compact until all energy, mass, light and more intense than what current theories had anticipated. space are compressed. It is this singularity of unimaginable mass and energy that first exploded as the Big Bang, and eventually formed the universe we see today. Big Bang theory predicted that the initial universe was an expanding plasma soup of light and particles. As the energy budget within our universe began to spread thin, stretched across expanding space, temperatures lowered rapidly. At 5,000°F, the equivalent temperature of the sun, and protons were cool

Original . Credit: Wikipedia

What could cause this excess radio signal? Could New York City be the source? Was it coming from the telescope itself because of a poor internal setup of the device? Even after the scientists kicked out a flock of The moment when free electrons and protons formed Hydrogen atoms, freeing light to travel through space pigeons from their telescope – and cleaned away their and time, reach the Bell Lab telescope and confuse leftover droppings – the noise persisted. They were Penzias and Wilson in the form of the Microwave ultimately forced to conclude that this background signal . Credit: Universe Adventures

3 TJO Newsletter Summer 2017 enough to partners. This coupling into - – the first possible baby photo of the universe. proton pairs – Hydrogen atoms – finally lifted the veil of The evidence of a uniform cosmic microwave free-moving particles that scattered light. 380,000 years background radiation definitively proved the Big Bang after the Big Bang, the universe turned from opaque to theory. Einstein corrected his equations, calling it his transparent. For the first time, light within the universe biggest blunder. The experimentalists Penzias and was free to travel across space and time, eventually Wilson had the significance of their discovery explained landing at the Horn Antenna. This light – the surface of to them by the newspaper the next morning, but last scattering – was set free. nonetheless jointly won the in 1978 for their When Penzias and Wilson called Robert Dicke at incredible experimental discovery of the CMB. Further his Princeton office, he infamously commented to his observations of the Cosmic Microwave Background have colleagues “well boys, we’ve been scooped!” The since found tiny 0.00001 K fluctuations of temperature, microwave radiation discovered by Penzias and Wilson known as anisotropies, corresponding to slight density was the first detection of the light from the transparent variations in the plasma from the moment of last universe. Because light travels at the cosmic speed limit scattering. Anisotropies laid the foundation that built of 293 million m/ from the most distant visible reaches modern-day large-scale galactic structure. To this day, of the universe, the light arriving is 14 billion years old. scientists study the CMB to probe the formation of Furthermore, as light travels, it is constrained by the structure and matter in the universe, and cosmology. expanding and cooling universe. While the light left at In the words of my favorite intergalactic 5,000°F, it reaches our detectors as the Cosmic hitchhiker, don’t panic. We are on a sometimes Microwave Background (CMB) at a uniform and cold - incomprehensible but beautiful ride within a universe 450° F, or just 2.7° Kelvin above absolute zero. When sparked by an incredibly massive Big Bang. And we can Penzias and Wilson found their microwave background thank Penzias, Wilson and Dicke for finding and noise, they had stumbled upon a 14-billion-year-old hiss explaining the initial clues that let us know. Thanks to tiny variations in a plasma of particles 14 billion years ago, we now have a hissing universe filled with galactic structure, the , Earth, and the curious creatures who call it home.

SOURCES CITED

Daniel, Lisa. You Can Still Hear the Hiss of the Big Bang. Slate: 2014. Print. Discovery of cosmic microwave background radiation. CMB light is incredibly uniform. Finding variations in Wikipedia, 2017. Print. the 2.7° K temperature is equivalent to finding a Koberlein, Brian. One Universe at a Time: What does the cosmic microwave background tell us? 2015. Print. microbe on a basket ball. But tiny 0.00001 K ripples in The Universe Adventure - Origins of the CMB. temperature of plasma depicted above on a globe are universeadventure.org, 2017. Print. responsible for large scale galactic structure seen Reich, Henry. Picture of the Big Bang (a.k.a. Oldest Light in today. Credit: Brian Koberlein the Universe). minutephysics, 2017. Video.

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