Radio Telescopes

Radio Telescopes

The great radio telescopes of the world are constructed in remote locations for the same reason Paul Gauguin sailed to Tahiti: For them to work well, they must be far from civilization. As civilian and military radio traffic has increased, radio telescopes have had to hide – sequestered in an obscure valley in Puerto Rico, say, or exiled to a vast scrub desert inn New Mexico or Kazakhstan.

As radio interference continues to grow, it makes increasing sense to build the telescopes off the Earth altogether. The scientists who work at these isolated observatories tend to be dogged and determined. Spouses abandon them, children leave home at the first opportunity, but the astronomers stick it out. Rarely do they think of themselves as dreamers. The permanent scientific staff in remote observatories tend to be the practical ones, the experimentalists, the experts who know a great deal about antenna design and data analysis, and much less about quasars or pulsars. Generally speaking, they had not longed for the stars in childhood; they had been too busy repairing the carburetor in the family car.

The word “quasar” is an acronym for “quasi-stellar radio source”. In the search for extraterrestrial intelligence, what could be done was so far ahead of what had been done (Carl Sagan and Megan Jorgensen). Image: © Elena

After receiving her doctorate, Ellie accepted an appointment as research associate at the Arecibo Observatory, a great bowl 305 meters across, fixed to the floor of a karst valley inn the foothills of northwestern Puerto Rico. With the largest radio telescope on Earth, she was eager to employ her maser detector to look at as many different astronomical objects as she could – nearby planets and stars, the center of the Galaxy, pulsars and quasars.

She also hoped to examine a few nearby stars for possible signals of intelligent origin. With her detector system it would be possible to hear the radio leakage from a planet like earth even if it was a few light-years away. And an advanced society, intending to communicate with us, would doubtless be capable of much greater power transmissions than we are.

If Arecibo, used as a radar telescope, was capable of transmitting one megawatt of power to a specific locale in space, then a civilisation only a little bit in advance of ours might, she thought, be capable of transmitting to the Earth with a telescope as large as Arecibo but with a hundred-megawatt transmitter, Arecibo should be able to detect them virtually anywhere in the Milky Way Galaxy.

When Ellie thought carefully about it, she was surprised that, in the search for extraterrestrial intelligence, what could be done was so far ahead of what had been done. The resources that had been devoted to this question were trifling, she thought. She was hard pressed to name a more important scientific problem.

Nascent Galaxies

Nascent Galaxies

Within the nascent galaxies, much smaller clouds are also experiencing gravitational collapse; interior temperatures become very high, thermonuclear reactions are thus initiated, and the first stars turn on! The hot, massive young stars evolve rapidly, profligates carelessly spending their capital of hydrogen fuel, soon ending their lives in brilliant supernova explosions, returning thermonuclear ash – helium, carbon, oxygen and heavier elements – to the interstellar gas for subsequent generations of star formation.

Supernova explosions or massive early stars produced successive overlapping shock waves in the adjacent gas, compressing the intergalactic medium and accelerating the generation of clusters of galaxies. Gravity is opportunistic, amplifying even small condensations of matter. Supernova shock waves may have contributed to accretions of matter at every scale. The epic of cosmic evolution had begun, a hierarchy in the condensation of matter from the gas of the Big Bang – clusters of galaxies, galaxies, stars, planets and, eventually, life and an intelligence able to understand a little of the elegant process responsible for its origin.

Clusters of galaxies fill the universe today. Image: Another World © by Elena

Some clusters of galaxies are insignificant, paltry collections of a few dozen galaxies. The affectionately tilted Local Group contains only two large galaxies of any size, both spirals : the Milky Way and M31. Other clusters run to immense hordes of thousands of galaxies in mutual gravitational embrace. There is some hint that the Virgo cluster contains tens of thousands of galaxies.

On the largest scale we inhabit a universe of galaxies, perhaps a hundred billion exquisite examples of cosmic architecture and decay, with order and disorder equally evident: normal spirals, turned at various angles to our earthly line of sight (face-on we see the spiral arms, edge-on, the central lanes of gas and dust and stars running through the center, connecting the spiral arms on opposite sides; stately giant elliptical galaxies containing more than a trillion stars which have grown so large because they have swallowed and merged with other galaxies; a plethora of dwarf ellipticals, the galactic midges, each containing some paltry millions of suns ; an immense variety of mysterious irregulars, indications that in the world of galaxies there are places where something has gone ominously wrong; and galaxies orbiting each other so closely that their edges are bent by the gravity of their companions and in some cases streamers of gas and stars are drawn out gravitationally, a bridge between the galaxies.

(By Carl Sagan, Cosmos)

Night Sky as Companion and Inspiration

Night Sky As Companion and Inspiration

For all the tenure of humans on Earth, the night sky had been a companion and an inspiration. The stars are comforting. They seem to demonstrate that the heavens were created for the benefit and instruction of humans. This pathetic conceit became the conventional wisdom worldwide. No culture was free of it.

Some people found in the skies an aperture to the religious sensibility and many were awestruck and humbled by the glory and scale of the cosmos. Others were stimulated to the most extravagant flights of fancy.

At the very moment that humans discovered the scale of the universe and found that their most unconstrained fancies were in fact dwarfed by the true dimensions of even the Milky Way Galaxy, they took steps that ensured that their descendants would be unable to see the stars at all.

Milky Way. The night sky is our companion and an inspiration, as the stars are comforting (Megan Jorgensen said). Milky Was Galaxy. Image: © Elena

For a million years humans had grown up with a personal daily knowledge of the vault of heaven. In the last few thousand years they began building and emigrating to the cities. In the last few decades, a major fraction of the human population had abandoned a rustic way of life. As technology developed and the cities were polluted, the nights became starless. New generations grew to maturity wholly ignorant of the sky that had transfixed their ancestors and that had stimulated the modern age of science and technology. Without even noticing, just as astronomy entered a golden age most people cut themselves off from the sky, a cosmic isolationism that ended only with the dawn of space exploration.

(By Carl Sagan, Contact)

Space Observatory

Space Observatory

The sight of the observatory growing smoothly beyond his visor returned Daniel to the problems at hand. He nudged the translation control, brought the module to a stop less than a meter from the airlock, and docked to a fitting next to the airlock entry hatch.

After some trouble disengaging himself, he tethered the module to the docking part and entered the observatory. As the airlock slowly repressurized, Daniel stared down through the mesh-covered porthole. The raft of modules – so massive and labyrinthine when viewed up close – seemed like insignificant Tinkertoys against the luminescent Earth.

After the pressure equalized, Daniel removed his helmet and pulled himself through the hatch into the observatory. Audrey floated near the apex of the conical interior and she obviously realized she had a visitor, but she kept her eye nestled against the lens of an optical telescope. Her hair, which normally gave a slicked-back appearance when restrained by a net, floated out in a nest of spikes. Her free hand twirled her glasses by the eyepiece.

Space Observatory. Night Sky, November. Illustration: Elena

Black Holes Are Nasty

Black Holes Are Nasty

Or maybe this isn’t a black hole and I’m headed toward a naked singularity. Near a singularity, casualty could be violated, effects could precede causes, time could flow backward, and you were unlikely to survive, much less remember the experience.

For a rotating black hole, Elie dredged up from her studies years before, there as not a point but a ring singularity or something still more complex to be avoided. Black holes are nasty. The gravitational tidal forces were so great that you would be stretched into a long this thread if you were so careless as to fall in. You would also be crushed laterally.

Through the gray transparent surfaces that were now the ceiling and floor, she could see a great flurry of activity. The organosilicate matrix was collapsing on itself in some places and unfolding in others; the embedded erbium dowels were spinning and tumbling. Everything inside the dodec looked quite ordinary.

A giant planet. Black Holes are the most exciting mystery in the Universe. Image: © Elena

The pentagonal panels of the dodecahedron had become transparent. Above and below she could make out the organosilicate lacework and the implanted erbium dowels, which seemed to be stirring. All three benzels had disappeared. The dodecahedron plunged, racing down a long dark tunnel just broad enough to permit its passage. There was a texture to the tunnel walls, from which Elie could sense their speed. The patterns were irregular softedged mottlings, nothing with a well-defined form. The walls were not memorable for their appearance, only for their functions.

Every now and then a forward vertex of the dodecahedron would brush the wall, and flakes of an unknown material would be scraped off. The dodec itself seemed unaffected. The faint yellow lighting was diffuse, uniform.

Back holes were either primordial – made during the origin of the universe – or produced in a later epoch by the collapse of a star more massive than the Sun. Then, the gravity would be so strong that – except for quantum effects – even light could not escape, although the gravitational field certainly would remain. Hence “black’, hence “holes”.

But the black holes didn’t collapse a star, and she couldn’t see any way in which they had captured a primordial black hole.