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Tagged with “astronomy” (34)

  1. Priyamvada Natarajan: Solving Dark Matter and Dark Energy - The Long Now

    The darkness of dark matter and dark energy

    All that we know of the universe we get from observing photons, Natarajan pointed out.

    But dark matter, which makes up 90 percent of the total mass in the universe, is called dark because it neither emits nor reflects photons—and because of our ignorance of what it is!

    It is conjectured to be made up of still-unidentified exotic collisionless particles which might weigh about six times more than an electron.

    Though some challenge whether dark matter even exists, Natarajan is persuaded that it does because of her research on “the heaviest objects in the universe“—galaxy clusters of more than 1,000 galaxies.

    First of all, the rotation of stars within galaxies does not look Keplerian—the outermost stars move far too quickly as discovered in the 1970s.

    Their rapid rate of motion only makes sense if there is a vast “halo” of dark matter enclosing each galaxy.

    And galaxy clusters have so much mass (90 percent of it dark) that their gravitation bends light, “lenses” it.

    A galaxy perfectly aligned on the far side of a galaxy cluster appears to us—via the Hubble Space Telescope—as a set of multiple arc-shaped (distorted) galaxy images.

    Studying the precise geometry of those images can reveal some of the nature of dark matter, such as that it appears to be “clumpy.”

    When the next-generation of space telescopes - the James Webb Space Telescope that comes online in 2018 and the WFIRST a few years afterward, much more will be learned.

    There are also instruments on Earth trying to detect dark-matter particles directly, so far without success.

    As for dark energy—the accelerating expansion of the universe—its shocking discovery came from two independent teams in 1998-99.

    Dark energy is now understood to constitute 72 percent of the entire contents of the universe.

    (Of the remainder, dark matter is 23 percent, and atoms—the part that we know—makes up just 4.6 percent.)

    But when the universe was just 380,000 years old (13.7 billion years ago), there was no dark energy.

    But now “the universe is expanding at a pretty fast clip.”

    Natarajan hopes to use galaxy-cluster lensing as a tool “to trace the geometry of space-time which encodes dark energy.”

    These days, she said, data is coming in from the universe faster than theory can keep up with it.

    ”We are in a golden age of cosmology.”

    —Stewart Brand


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  2. BBC Radio 4 - The Life Scientific, Chris Lintott

    Astronomer and Sky at Night TV presenter Chris Lintott tells Jim Al Khalili about his "Citizen Science" project of crowd-sourced astronomy, Galaxy Zoo, and of working with Brian May and the late Sir Patrick Moore.


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  3. .01 Neil deGrasse Tyson - “Are you wired for doubt?”: 6/25/15

    Star Talk’s Neil deGrasse Tyson on how data is revolutionizing astronomy, why he hates "balance," and why his being black often leads people to confuse him for a sportscaster.


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  4. Interview with Dr. Jill Tarter

    Dr. Jill Tarter holds the Bernard M. Oliver Chair for SETI Research at the SETI Institute in California. She has spent majority of her professional career attempting to determine whether we are alone in the universe, and among her other prior positions, she was the Project Scientist for NASA’s SETI program. In this interview, Dr. Tarter tells us about the latest in SETI research, including what we can expect the Square Kilometer Array to contribute to SETI.


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  5. Big Picture Science: Long Live Longevity

    Here’s to a long life – which, on average, is longer today than it was a century ago. How much farther can we extend that ultimate finish line? Scientists are in hot pursuit of the secret to longer life.

    The latest in aging studies and why there’s a silver lining for the silver-haired set: older people are happier. Also, what longevity means if you’re a tree. Plus, why civilizations need to stick around if we’re to make contact with E.T.

    And, how our perception of time shifts as we age, and other tricks that clocks play on the mind.


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  6. Astronomycast 145: Interstellar Travel

    In science fiction it’s easy to hop into your spaceship and blast off for other stars. But the true distances between stars, and the limits of relativity make interstellar travel almost impossible with our current technology. What would it really take to travel from star to star, exploring the galaxy?


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  7. Peter Schwartz: The Starships ARE Coming - The Long Now

    We now know, Schwartz began, that nearly all of the billions of stars in our galaxy have planets. If we can master interstellar travel, "there’s someplace to go." Our own solar system is pretty boring—-one planet is habitable, the rest are "like Antarctica without ice" or worse.

    So this last year a number of researchers and visionaries have begun formal investigation into the practicalities of getting beyond our own solar system. It is an extremely hard problem, for two primary reasons—-the enormous energy required to drive far and fast, and the vast amount of time it takes to get anywhere even at high speed.

    The energy required can be thought of in three ways. 1) Impossible—-what most scientists think. 2) Slow. 3) Faster than light (FTL). Chemical rockets won’t do at all. Nuclear fission rockets may suffice for visiting local planets, but it would take at least fusion to get to the planets of other stars. Schwartz showed Adam Crowl’s scheme for a Bussard Ramjet using interstellar ions for a fusion drive. James Benford (co-author of the book on all this, Starship Century) makes the case for sail ships powered by lasers based in our Solar System.

    As for faster-than-light, that requires "reinventing physics." Physics does keep doing that (as with the recent discovery of "dark energy"). NASA has one researcher, Harold White, investigating the potential of microscopic wormholes for superluminal travel.

    Standard-physics travel will require extremely long voyages, much longer than a human lifetime. Schwartz suggested four options. 1) Generational ships—-whole mini-societies commit to voyages that only their descendents will complete. 2) Sleep ships—-like in the movie "Avatar," travelers go into hibernation. 3) Relativistic ships—-at near the speed of light, time compresses, so that travelers may experience only 10 years while 100 years pass back on Earth. 4) Download ships—-"Suppose we learn how to copy human consciousness into some machine-like device. Such ‘iPersons’ would be able to control an avatar that could function in environments inhospitable to biological humans. They would not be limited to Earthlike planets."

    Freeman Dyson has added an important idea, that interstellar space may be full of objects—-comets and planets and other things unattached to stars. They could be used for fuel, water, even food. "Some of the objects may be alive." Dyson notes that, thanks to island-hopping, Polynesians explored the Pacific long before Europeans crossed the Atlantic. We might get to the stars by steps.

    Futurist Schwartz laid out four scenarios of the potential for star travel in the next 300 years, building on three population scenarios. By 2300 there could be 36 billion people, if religious faith drives large families. Or, vast wealth might make small families and long life so much the norm that there are only 2.3 billion people on Earth. One harsh scenario has 9 billion people using up the Earth.

    Thus his four starship scenarios… 1) "Stuck in the Mud"—-we can’t or won’t muster the ability to travel far. 2) "God’s Galaxy"—-the faithful deploy their discipline to mount interstellar missions to carry the Word to the stars; they could handle generational ships. 3) "Escape from a Dying Planet"—-to get lots of people to new worlds and new hope would probably require sleep ships. 4) "Trillionaires in Space"—-the future likes of Elon Musk, Jeff Bezos, and Richard Branson will have the means and desire to push the envelope all the way, employing relativistic and download ships or even faster-than-light travel.

    Schwartz concluded that there are apparently many paths that can get us to the stars. In other words, "Galactic civilization is almost inevitable."


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  8. Time’s Mysteries Part I: Marking Time

    Time’s a mystery, yet we’ve invented clever ways to capture it. From sundials to atomic clocks, trace the history of time-keeping. Also, discover the surprising accuracy of nature’s dating schemes - from the decay of carbon to laying down tree rings.

    Plus, why the "New York minute," stretches to hours in Rio de Janeiro: cultural differences in the perception of time.


    * Chris Turney - Geologist at the University of Exeter, UK, and the author of Bones, Rocks and Stars: The Science of When Things Happened
    * Demetrios Matsakis - Head of the U.S. Naval Observatory’s Time Service
    * Steven Jefferts - Physicist at the National Institute of Standards and Technology in Boulder, Colorado
    * Robert Levine - Psychologist at California State University in Fresno and the author of The Geography of Time
    * Norman Mohr - Owner, Mohr Clocks, Mountain View, California

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  9. Desktop Diaries: Jill Tarter

    "Someone described my office as an eight-year-old’s daydream," says astronomer Jill Tarter, who has been collecting E.T.-themed office ornaments for 30 years. Tarter was the SETI (Search for Extraterrestrial Intelligence) Institute’s first employee, and the inspiration for the character in Carl Sagan’s Contact.

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  10. Ed Lu: Anthropocene Astronomy: Thwarting Dangerous Asteroids Begins with Finding Them - The Long Now

    This talk was given at Marines’ Memorial Theater in San Francisco, California on Tuesday June 18, 02013.

    Are humans smarter than dinosaurs? We haven’t proved it yet.

    In the long now, the greatest threat to life on Earth, or (more frequently) to civilization, or (still more frequently) to cities, is asteroid impact. The technology exists to eliminate the threat permanently. It is relatively easy and relatively cheap to do. However to date, government organizations have not made this a priority. That leaves nonprofits and private funding. Considerable efficiency may be gained by going that route.

    Ed Lu is CEO and Chairman of the B612 Foundation, which, in partnership with Ball Aerospace is building an asteroid-detection system called Sentinel, aiming for launch in 2018. A three time NASA astronaut, Lu is also the co-inventor of the “gravity tractor” — one of the several techniques that can be used to nudge threatening asteroids out their collision paths with Earth.

    Asteroid threat is an attention-span problem blended with a delayed-gratification problem—-exactly the kind of thing that Long Now was set up to help with. Taking the extreme danger of asteroids seriously requires thinking at century and millennium scale. Dealing with the threat requires programs that span decades, because asteroids can only be deflected if they are found and dealt with many years before their potential impact. The reality is that the predictability of orbital mechanics makes cosmic planetary defense completely workable. Sometimes real science is more amazing than science fiction.

    On February 15th of this year, civilization got a wake-up call. A 45 meter asteroid, large enough to completely obliterate a major city, missed Earth by only 17,000 miles, and hours later a smaller rock, 17 meters in diameter, exploded in the air over Chelyabinsk, Russia, injuring 1500 people. Interest in B612’s asteroid detection mission spiked accordingly.


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