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Ethan Siegel
Works at NASA's The Space Place
Attended University of Florida College of Liberal Arts and Sciences
Lived in Bronx, New York
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Ethan Siegel

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“I hear of experiments on the ISS being conducted in Zero Gravity, and I hear that studies are done on humans in ‘Zero Gravity’. But is 'Zero Gravity’ an actual thing?”

If you want to experience zero gravity, all you need to do is go to space, turn your rocket off and feel that weightless sensation, right? Except, from up there in Earth’s orbit, the gravitational force on you is still almost as great as it is on Earth’s surface! You still accelerate down towards the center of the Earth, not quite at 9.8 m/s^2, but not by much less. There’s no place in the Universe where you can go to hide from the long-range force of gravity; its effects reach everywhere. So how, then, can we claim to truly know what it’s like in a zero-gravity environment? Because zero gravity isn’t about turning gravity off; it’s about the forces we do (and don’t) experience on our bodies.

According to Einstein, free-fall and zero gravity are actually equivalent, although that’s far from obvious. Here’s the science behind why on this week’s Ask Ethan!
No matter where you are in the Universe, you'll still have masses pulling on you. So how is 'zero gravity' possible?
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Ethan Siegel

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Did you catch me on KGW's Live @ 7 last night?

Here's your big chance, where we cover the big news about Earth's temperature, finds about merging stars and an incredible asteroid, the upcoming eclipse, and a feature of my awesome Space Kilt made by local artist Susanné Rose Maestas.

It's five minutes that you won't regret, from Portland, OR's NBC affiliate!
The space talk with Ethan Siegel
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I'm still confused by the fact that a person can simultaneously claim to support the cause of science (filtering the noise of the observer) and openly advocate "human space exploration" (amplifying that very noise of the observer)?
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Ethan Siegel

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"Yes, the science will be incredible. As Garth Illingsworth said about this telescope, "we're going to learn more in one day from James Webb Space Telescope than mankind currently knows" about the first galaxies in the Universe. Just like the "Hubble Key Project" wasn't even the greatest find that the Hubble Space Telescope made, perhaps with its unique capabilities, JWST will reveal even deeper secrets about the Universe than what we know to look for. In less than two years, we'll begin to find out. But without the team of engineers who designed, built and executed all of this to exquisite precision, we wouldn't have any of it at all."

Launching in October of 2018, the James Webb Space Telescope will revolutionize our conception of the Universe. The biggest scientific find that we know it can uncover is how the Universe came to be the way it is today. How the first stars and galaxies formed, what they looked like and how they gave rise to the Universe we see today. But none of this would be possible without the incredible team of men and women who actually designed and built the telescope. At this most recent American Astronomical Society meeting, I had the chance to sit down with Jon Arenberg, the Chief Engineer in charge of building the James Webb Space Telescope, and got the inside scoop on how it actually happened, including the greatest challenges they had to overcome.

Take an incredible journey unlike any other you've taken, and go behind the scenes into building the greatest space telescope of all!
The science will be incredible, but it's the engineering that makes it all possible.
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Ethan Siegel

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“When the clusters collide, their mutual gravity causes an incredibly energetic cosmic smash-up, heating the gas to such high temperatures they emit X-rays. Mysteriously, on the outskirts of the collision, intense radio emission can be found. The fact that these two signals are offset indicate that there's another, secondary process at work.”

When two galaxy clusters collide, there are a slew of cosmic certainties you can bet on: all the galaxies will miss one another, the intracluster gases will collide and heat up, and X-rays will be emitted. But on rare occasion, radio emission can be found, too. Which is a puzzle, since that requires electrons to gain an extra factor of 1,000,000 in energy! How can that happen? Up until recently, it was a mystery, but a new colliding cluster, Abell 3411 and 3412, has shown something incredible: gas shocks on the outskirts of the X-ray collisions appear to get a blast from nearby, active supermassive black holes, giving the electrons the needed boost and creating those energetic electrons after all!

Go get the full story in pictures, videos and no more than 200 words on today’s Mostly Mute Monday!
The X-rays are powerful and reveal the matter, but the radio emission requires energies a million times greater. How does the collision do it?
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Good column, and very good one on the "why no dark matter black holes" subject.. 
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“And so this camera has taught us a lot about how stars die. But what it’s also told us about is how and where they’re born! You see, these nebulae don’t just dissipate after a few thousand years; they often spit out entire star systems worth of gas, and trigger the formation of new stars. One of the most spectacular pictures took place deep inside the Eagle Nebula.

And when Hubble imaged the pillars at the center of it, it was one of the most amazing things ever.”

Over its more than 25 year lifetime, the Hubble Space Telescope has shown us what the Universe truly looks like. It’s done so in a myriad of ways, from planets to stars – dying and forming – to galaxies to gravity’s effects to the deepest abysses of blackness of all. Nothing in space is the same as it was before humanity knew Hubble. Yet even the camera most responsible for our iconic images, WFPC2, isn’t the end of the story. That camera was removed in 2009, and in the 8 years since, we’ve deepened our views and our understanding even further. Even before the launch of the James Webb Space Telescope, our journey into the unknown Universe continues with Hubble in a way we never could have imagined when the observatory was first launched.

Come see for yourself in far more images than you’ve ever seen at once before!
More than 25 years since its launch, it hasn't stopped amazing us.
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"At its core, science is two simultaneous things, neither one of which is valuable without the other: a full suite of knowledge and data relevant to a particular issue, and a process for testing, inquiring, refining and reproducing our best explanations for that full suite of information. Being aware of the enterprise of science means having a tremendous respect for the people devoting their lives to furthering our understanding of any aspect of the Universe in this fashion, from the instrument builders to the experiment conductors to the data analysts to the theorists working to create an overarching framework. Being aware of the enterprise of science means recognizing your own inability to be competent in all areas of science no matter how smart or qualified you are; it means recognizing the need for legitimate expertise and for valuing the conclusions thereby reached."

Are you scientifically literate? Do you even know what that means? You'll periodically see quizzes designed to assess some measure of science literacy, and they'll usually focus on a slew of general knowledge questions, inevitably decrying what a large fraction of people don't know. But is that a fair assessment of scientific literacy, or what it means to be scientifically literate? Highly doubtful. At its core, scientific literacy isn't about being able to answer questions about science correctly or to explain various phenomena, but about two things that most people generally don't think about: having an awareness for what the enterprise of science is and having an appreciation for what scientific knowledge and discoveries do for humanity.

If you think both of those things describe you, or you'd like them to, come find out what that really means and entails, and learn what it truly means to be scientifically literate.
Are you scientifically literate? Find out!
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Self assessment seems a suspiciously unscientific test of science understanding or "litteracy".
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Ethan Siegel

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“The truths of the Universe are written out there, on the Universe itself, and are accessible to us all through the process of inquiry. To allow an uncertain faith to stand in as an answer where scientific knowledge is required does us all a disservice; the illusion of knowledge — or reaching a conclusion before obtaining the evidence — is a poor substitute for what we might actually come to learn, if only we ask the right questions. Science can never prove or disprove the existence of God, but if we use our beliefs as an excuse to draw conclusions that scientifically, we’re not ready for, we run the grave risk of depriving ourselves of what we might have come to truly learn.”

If we find out that we truly are alone in the Universe, whether there’s no other life, intelligent life, or spacefaring life, there’s no doubt that makes us special. But does that make us divinely chosen? Or, even more to the point, does that mean that the Universe was designed to give rise to human beings; with us in mind as the end goal? That isn’t necessarily a question we can know the answer to, but it’s something we can approach with science. In particular, we can ask three separate questions:

1. What are, scientifically, the conditions that we need for life to arise?
2. How rare or common are these conditions elsewhere in the Universe?
3. And finally, if we don’t find life in the places and under the conditions where we expect it, can that prove the existence of God?

The questions themselves are interesting, but what science has to say about all of them might be the most interesting thing of all.
And remember, you can't assume the conclusion before you find the evidence!
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Great post Ethan, Thank you.

'The truths of the Universe are written out there'
Brings Sagan to mind - 'The answers have always been there, we just didn't know how to read them.'

The image of Michael Angelo's painting, an art expert related to me that the artist, who against social acceptance at the time dissected human bodies in search of understanding.
That explains his almost characture illustrations of the human body.

The outline God sits in very closely matches the geometry of the Human brain.
Seems he had a hidden message in his work for the church...
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Ethan Siegel

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"Our politicians may deny it. Our corporations may deny it. And even the secretary of state and the president may deny it. But denying it doesn't change reality. The Earth is warming; we are the cause; the consequences are severe and increasing; it's up to all of us to do something about it. Even with La Niña in place for 2017, global temperature levels are likely to never sink back to the 20th century average, not for a single year in the 21st century. The Earth belongs to us all, including all the humans who'll come after us. If we have any hope of taking care of it, it has to start with accepting the truth. Even if it's inconvenient."

The latest climate science results are out, and 2016 was the hottest year on record. Again. Breaking the previous record... from 2015. Which broke the previous record of 2014. In fact, of the 17 hottest years on record, 16 of them have occurred in the 21st century. The question isn't whether the Earth is warming (it is), whether it's human-caused (it is), whether burning fossil fuels is the major contributor (it is), or whether we need to do something about it (we do). The question is whether we will. And that begins with accepting the scientific truth.

It's easy to dupe you if you want to be duped, but the science doesn't lie. Come learn it, and what the arguments you're likely to encounter are. Arm yourselves. We're in for a hell of a fight.
The 2016 climate results are in. If you think the Earth isn't warming, welcome to the facts.
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I think we should, and will, reduce CO2 emissions. That will be a matter of continuing to develop better technology, not using scare tactics. Develop convenient, economical clean energy and the emission reductions take care of themselves, just like when gas lighting changed to electric.
+Martin Lewitt  I think dialing-in accurately on the end question of sensitivity is very difficult currently. Determining if the feedbacks amplify or attenuate is complex enough, but there's also an atmosphere of intimidation, IMO. When you get called a "denier" for asking valid questions that a scientist should ask, there's a problem. It needs to be investigated in an objective, dispassionate way, and I don't see that right now.
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"In the constellation of Cygnus, this binary system currently invisible to the naked eye, KIC 9832227, may brighten by the same amount. Since it's only 1,800 light years distant and in a relatively clear part of the sky, this star is not only expected to become visible to the naked eye, it's expected to become one of the five brightest stars in the entire constellation."

When you have a light curve with two different large, periodic dips in it, a binary star system is the likeliest explanation. The stars eclipse, and in the case where they're so close their envelopes touch, they're known as contact binaries. That, alone, is enough to make a system spectacular. But in the case of this system, KIC 9832227, the orbital period is speeding up, meaning they're destined to merge. When they do, we can expect to see a luminous red nova, but we might -- if we're lucky -- also uncover the explanation for one of Hubble's most amazing pictures and hitherto unsolved mysteries: the mysterious light curve and echoes of the cosmic rose, V838 Monocerotis.

Come get the full story and see what all the fuss is really about on Starts With A Bang today!
An artist's impression of an exotic binary star system. Image credit: M. Garlick/University of Warwick/ESO. When you think about our Solar System, with its lone, luminous star dominating both the mass and light of our local corner of the Milky Way, you might think that this is what 'typical' looks like. In [...]
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This very cool! Hope I have a chance to see it!
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"“When you get right down to it, this is just more elitism.”

Yes. Yes, you said it, and this is right. Elite, expert knowledge — someone armed with expert facts, expert skills, expert reasoning and the ability to draw expert conclusions — is worth more than the opinion of a non-elite person. There is no greater example of this than in science. [...] Will you, without that expertise, follow the arguments and teachings of experts and adhere to what they conclude? Can you do it? Will I see you do it here? And will I see you do it as respects all aspects of robust, well-understood science even if it’s not well-understood by you?"

There are a slew of things to follow-up on this week, from mysteriously green galaxies to exploding stars to the Big Bounce and entropy to the origin of the heaviest elements in the Universe and much more. But the biggest thought-provoker was on the topic of scientific literacy. It's not something you can measure with a test, at least, not if you want to do it right. Rather, you can only measure it with humility: how willing you are to admit that you yourself are not the expert you need to be to evaluate a scientific claim. For that, you need a real, legitimate scientist in that field.

Are you willing to go there? Find out on this edition of our comments of the week!
“Men go abroad to wonder at the heights of mountains, at the huge waves of the sea, at the long courses of the rivers, at the vast compass of the ocean, at the circular motions of the stars, and they pass by themselves without wondering.” -Saint Augustine Well, another week has gone by — the…
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Wouldn't the "early metal poor stars" be much larger than present stars, metal poor or not? Wouldn't that size cause them to be hotter?
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"As it stands today, we know the Hubble expansion rate better than we ever have, and yet our two different method of arriving at it seem to give irreconcilable values. There are a myriad of different measurements going on right now attempting to find out which camp is right, which camp is wrong, and exactly where the errors lie. If history has taught us anything, we can say for certain that two things will come of this: we're going to learn something additional and wonderful about the nature of our Universe when this gets resolved, and that this current controversy won't be the last one concerning how the Universe expands."

It seems like the simplest, most fundamental quantitative question about the expanding Universe of all: how fast is it expanding? Even though it's been more than 80 years since Hubble's most career-defining discovery, we still don't know the answer. In fact, the two main methods we have of measuring it give incompatible results. The largest-scale observations, like the cosmic microwave background and baryon acoustic oscillations, give a result that's on the low side: 67 km/s/Mpc. On the other hand, distance ladder measurements, relying on individual stars, galaxies and supernovae, give a higher result: 74 km/s/Mpc. But these are known well enough that they're inconsistent with one another.

This is a story that's been ongoing since we first learned the Universe was expanding, but the next five years should be critical in resolving this tension. Find out why!
Over 80 years since the expanding Universe was discovered, the debate still rages.
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the subtleties of expansion are quite difficult to grasp in the context of ordinary measurements of length and time. I made a video that explores this subject :

youtube.com - Dark Energy Solved


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"By the same token, the James Webb Space Telescope will teach us an incredible amount about the Universe, including further details about how stars form, what the earliest stellar populations look like, will show us gas giants and rogue planets in unprecedented detail and will tell us what made up the Universe at any given time in the past. It will show us a whole slew of things that Hubble cannot, by virtue of it reaching to much longer wavelengths of light than Hubble could ever hope to see. And with its huge, large-aperture primary mirror, it will be able to collect more light in a single day than Hubble could in a week. The most exciting things, of course, will be the unexpected: the things we'll discover that we don't even know to look for yet.

But even if you don't learn about any of the science that James Webb will bring to us, there's one thing it will deliver that everyone can enjoy: the James Webb Space Telescope will show us how the Universe grew up."

The Hubble Space Telescope, for all of its scientific findings and how it revolutionized our understanding of the Universe itself, touched us all in a way that no piece of knowledge could ever encapsulate. In perhaps the greatest find of all, Hubble answered a question that many of us have had on our minds every time we've gazed up at a night sky: what does the Universe actually look like? From its images of star-forming regions, stellar deaths, galaxies, gravitational lenses and the deep abyss of empty space, it's awed us in a way no other observatory ever has. But James Webb is poised to do us one better, and show us something Hubble never could. It will show us how the Universe went from a state with no stars, no planets, and no galaxies to the Universe we know, recognize and inhabit today.

In short, the James Webb Space Telescope will show us how the Universe grew up. Come learn exactly what that means, and see if you aren't awed by the possibility!
Launching next year, humanity's most powerful telescope of all time will reveal the answers to questions we've always dreamed of.
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I'm awed by the possibility but this bird isn't flying yet! Let's keep our collective fingers crossed that it does.
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Work
Occupation
Theoretical Astrophysicist / Writer / Educator
Employment
  • NASA's The Space Place
    Columnist, 2013 - present
  • Trap!t
    Head Editor: Science/Health, 2011 - present
  • Starts With A Bang!
    Science Writer, 2008 - present
  • Lewis & Clark College
    Visiting Assistant Professor of Physics, 2009 - 2011
  • University of Portland
    Professor/Lab Coordinator, 2008 - 2009
  • Steward Observatory/University of Arizona
    Postdoctoral Research Associate, 2007 - 2008
  • University of Wisconsin
    Faculty Assistant, 2006 - 2007
  • University of Florida
    Teaching/Research Assistant, Fellow, 2001 - 2006
  • King/Drew Medical Magnet High School
    Teacher, 2000 - 2001
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Previously
Bronx, New York - Yonkers, New York - Evanston, Illinois - Torrance, California - Gainesville, Florida - Madison, Wisconsin - Tucson, Arizona - Portland, Oregon - Houston, Texas - Rome, Italy
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Science writer, professor and theoretical astrophysicist
Introduction
Theoretical Astrophysicist, Science Writer and Communicator, expert in (some aspects of) dark matter and dark energy, physical cosmology, and sometimes professor, teacher and educator.

Creator and writer of Starts With A Bang!, the 2010 Physics Blog of the Year! Author of over 1,000 articles, featured in Esquire, the St. Petersburg Times, ESPN.com's Page 2, and many others.

Competitive beardsman and amateur acrobat / halloween-costumer extraordinaire.
Education
  • University of Florida College of Liberal Arts and Sciences
    Physics, 2001 - 2006
  • Northwestern University
    Physics, Classics, Integrated Science Program, 1996 - 2000
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Male
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Married