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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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"While our Sun may vary, flare and eject matter with some frequency, ultra-low-mass red dwarfs like Proxima Centauri do so with much higher frequencies and great luminosities (as percentages of their star’s mass) than the Sun does. But an Earth-sized world with a period of 11 days should have a very large periodic signal in luminosity around its star that should be able to be teased out with long-period luminosity data. We should be able to tease out what the flares are and the intrinsic stellar variations, and be left with a light signal for the planet’s reflected light.

And if we’re lucky enough to get a thin crescent phase in our data (not good enough for a transit, but still a good alignment), we might be able to tease out some atmospheric signals as well. This isn’t able to be done with the present data that we have, but it might be good enough to do with the present technology that we have. And based on the amount of light we do see — atmospheric information aside — we should be able to infer some combination of albedo (reflectivity) and radius based on the amount of light we receive, with some degeneracy there."

What do you hope for when it comes to Proxima b? What are we doing now, what will we do in the future, and what are we capable of doing -- with current technology -- if we so choose? This edition of our Comments of the Week is focused on Proxima b, and you won't want to miss it!
“Because practical applications are so remote, many people assume we should not be interested. But this quest to understand the world is what defines us as human beings.” -Yuri Milner It’s been another big week here at Starts With A Bang, with stories covering the Universe near and far. First off, thanks to our generous Patreon supporters, we…
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Ethan Siegel

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“You’ve heard the story before: the Universe began with the Big Bang 13.8 billion years ago, and formed atoms, stars, galaxies, and eventually planets with the right ingredients for life. Looking at distant locations in the Universe is also looking back in time, and somehow, through the power of physics and astronomy, we’ve figured out not only how the Universe began, but its age. But how do we know how old the Universe is? That what Thys Hauptfleisch wants to know for this week’s Ask Ethan:

Ethan, how was the 13.8 billion years calculated? (In English please!)”

There’s a unique relationship between everything that exists in the Universe today – the stars and galaxies, the large-scale structure, the leftover glow from the Big Bang, the expansion rate, etc. – and the amount of time that’s passed since it all began. When it comes to our Universe, there really was a day without a yesterday, but how do we know exactly how much time has passed between then and now? There are two ways: one complex and one simple. The complex way is to determine all the matter and energy components making up the Universe, to measure how the Universe has expanded over the entirety of its cosmic history, and then, in the context of the Big Bang, to deduce how old the Universe must be. The other is to understand stars, measure them, and determine how old the oldest ones are.

The complex answer is more accurate, but more importantly, they both agree with each other. Get the details on this week’s Ask Ethan!
The Big Bang occurred 13.8 billion years ago, giving rise to our Universe. But how do we know that number for its age, and might it be different?
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‫ܢܹܪܓܵܐܠ; Nergal‬‎'s profile photoCharles Miesel's profile photoMINA HOSNY's profile photoChristina K Gross's profile photo
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Where Big Bangs intersect, the jelly of spacetime forms dark matter and dark energy. CKG
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“This planet is almost definitely tidally locked to its star, meaning that the same hemisphere always faces the star and the opposite hemisphere always faces away, just like the Moon does to Earth. The star itself is active and flares frequently, meaning that catastrophic radiation impacts the Sun-facing side quite regularly, but never touches the dark side. And the “seasons” are determined by the ellipticity of its orbit, rather than its axial tilt. But there’s still so much left to learn, and we have a number of different technological avenues to explore – including potentially all of them – if we want to learn more about it.”

Now that we’ve learned the nearest star to our Sun, Proxima Centauri, has a rocky planet at the right distance for liquid water, it’s time to consider how we might learn the answers to our burning questions about it and all nearby Earth-like exoplanets. What’s the atmosphere like, and what does it consist of? What does the surface of the world look like, and what’s on it? And is there life, or intelligent life, present at all? There are three ways to conduct these searches, and they’re all complementary. We can use giant ground-based telescopes, including arrays of telescopes, for high-resolution spectroscopic images of these worlds. We can use space-based telescopes with coronagraphs or starshades to image these worlds directly over time. Or we could undertake a journey across space, and visit the system directly to obtain in situ measurements we could never get from afar.

If this doesn’t inspire you to invest in astronomy and learning more about the Universe, perhaps nothing will!
It isn't only Earth; the closest star to our Sun also has at least one rocky planet at the right distance for liquid water on its surface. How can we learn more?
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sporadic -Z's profile photoKenny Laidlaw's profile photo
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A moon around this planet is probably a more likely candidate for life. If it had a magnetic field, it would be able to survive some of the flare activity and have chance. Going behind the planet would also offer some protection but would need considerable luck to always be in the right place to be safe.

Another possibility might be a planet, or moon, further out with a higher atmospheric pressure to allow liquid water to be present. It would need to be a hot planet, so either a runaway greenhouse effect or high volcanic activity (possibly due to a parent planet's gravity, ie similar to Jupiter's moons)
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Ethan Siegel

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Want to hear me talk about the Universe LIVE on tv?

Watch KGW's The Square tonight at 7 PM PT, or catch the live stream!
KGW Live Show Stream
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I try not to miss when you are on #Live@7... The way you share information about the universe is very understandable.
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“By traveling to greater distances, an entire hemisphere of Earth could be photographed at once. Traveling to the Moon enabled the first color photo of Earth seen rising over the limb of our natural satellite… while departing under just the right lighting conditions enabled the first color photo of the fully illuminated Earth to be taken.”

Can you believe it’s been 70 years since humanity first began exploring our own planet from space? It’s the best way to view clouds, weather patterns, sea ice, deforestation and all sorts of other phenomena that change the way our planet looks over time. As camera and satellite technology has gotten better and better, we can now – from low-Earth orbit – view the entire globe at resolutions of just a few meters per pixel. Meanwhile our most distant satellites are now good enough that they can make out the size, shape and phase of the Earth, including the Moon as well, from tens of millions of miles away.

Go get the full story, and an amazing video, over on Forbes today!
The most incredible collection of images celebrates our past and present in space, and makes us look to the future.
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“[H]ow many of the stars observable from Earth still exist? Since the light from many of them has traveled hundreds, thousands, even millions of light years to get here, is it not possible that many of the stars we see in fact burned out or exploded centuries or [millennia] ago and the light (or lack thereof) simply hasn’t reached us yet?”

When we look out at the night sky, we aren’t seeing the Universe everywhere as it is exactly at this moment, but rather as it was some time ago. Because the speed of light is finite and the stars are many light years away, we’re seeing them as they were a long time ago in the past. Is it possible that some of the stars we’re seeing have already burned out, and that their light has stopped shining? To answer that, there’s some astrophysics we need to look into. How long do these stars live? How many of them can we see? And which ones are the ones that “die” on timescales that are meaningful for what we’re seeking?

The answer is, of course, “most of them,” but is that all of them? Find out on this week’s Ask Ethan!
For every light year distant, we're looking a year back in time. Of the stars we can see, how many of them are still around?
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Dmitry Volkoff's profile photoMark Ruhland's profile photoValdis Klētnieks's profile photo
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+Mark Ruhland Could the sky look vastly different in the next few centuries??? or even decades???

Very unlikely. The 3,000 or so naked-eye stars we can see are all comfortably ensconced in the Main Sequence, where they're going to be for the next few billion years. Only Betelgeuse and Eta Carina are at all likely to go kaboom in the next few thousand years.

And only the most massive stars go kaboom - so even looking at distant galaxies, the majority of stars are still there. It's only when you start pointing powerful telescopes at galaxies billions of light year away that you start having a good chance of seeing a bunch of stars that no longer exist....
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Ethan Siegel

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Our Universe has been expanding and evolving since the hot, dense, expanding state known as the Big Bang first came to be. But there was a "day without yesterday," where the Big Bang occurred at a moment in time! Was that the birth of space and time itself? Or was there a pre-existing state that came before and gave rise to the Big Bang? Come find out the evidence that's led us to our greatest conclusions about the very beginning of where everything came from!

The Big Bang wasn't the very beginning of the Universe! Come find out how we know on the latest Starts With A Bang podcast.
Ethan Siegel
Starts With A Bang #11: Was The Big Bang The Beginning Of The Universe? by Ethan Siegel
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Ethan Siegel

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“So while there may not be a danger to you, there is a huge danger to electronics, ranging from automobiles to transformers to — most frighteningly of all — the entire power grid! That’s the real danger of a solar storm: an event similar to the 1859 Carrington event could cause anywhere between an estimated $1-to-$2 trillion of property damage, mostly due to electrical fires and damage to our infrastructure.”

In 1859, the Sun surprisingly increased in brightness so significantly for just a brief while that it was noticeable from Earth during the day. Less than 24 hours later, aurorae were visible so brightly and so far south that people awoke in the middle of the night, thinking it was dawn. But in addition to the spectacular sights, there were also downsides: telegraph wires spontaneously caught on fire, causing significant amounts of damage. The physics behind it is simple and straightforward, as the charged particles emitted from a solar flare interacted with the Earth’s atmosphere, changing its magnetic field over time and inducing current in any long-length (or coiled) wires. In the 21st century, such a flare would be a trillion dollar disaster, and we have very little to defend against it in place. Thankfully, with STEREO-B back online, our best early warning system is now 100% functional again!

Go get the full story about solar storms, their human impact and how NASA’s revived satellite just might be key to avoiding catastrophe when the inevitable occurs!
A strong solar flare could knock us back into the stone age. With both STEREO-A and STEREO-B alive, we'll get the earliest warnings possible.
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Leszek Dziędziewicki's profile photoAkash Ganga's profile photoDwayne Riojas's profile photoJames Marsh's profile photo
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Propaganda! 
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“Whether this planet exists or not — and it’s important to be skeptical, as there was a planet reported around Alpha Centauri B a few years ago that went away with more data — it’s important to remember that ‘Earth-like’ is a far cry from being anything at all like the actual Earth. By these criteria, Venus or Mars would be ‘Earth-like’ too, but you wouldn’t stake your hopes of becoming an interstellar species on either of those. As great as finding a new, rocky world in the potentially habitable zone around the nearest star to the Sun would be, it’s a long way from our ultimate dream of an Earth 2.0.”

Later tonight, the European Southern Observatory is expected to make an announcement, and the smart money is on the discovery of an Earth-like planet orbiting Proxima Centauri, the nearest star to our Sun. As incredibly exciting as this news is, however, it’s important to keep in mind that “Earth-like,” to an astronomer, means something very different than what we think of as “actually like Earth.” The only information we can glean from our present observations is the planet’s mass, size and orbit around a star. This is enough to tell us some of its properties, including a few ways (like tidal locking) that are quite different from Earth, but questions about its atmosphere, surface temperature, magnetic field and much more remain unanswered.

Come learn what the discovery of a new planet around our closest star would and wouldn’t tell us!
The closest star to our own may have an Earth-like planet around it. But how Earth-like would it really be?
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+Spinning Monkey Somebody doesn't know what a spectrometer does..
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“While modern technology like the Hubble Space Telescope has revealed hundreds of these gravitational lenses, nothing comparable existed in the early 20th century. Instead, a clever substitute was concocted by astrophysicists of the time: since the positions of stars were very well-known, you could observe stars close to the Sun during the day, where the Sun’s gravity would pull on those light rays. Since Einstein’s theory and Newton’s theory gave differing predictions for how much light would be bent by that extra gravitational force – with Einstein predicting double the Newtonian amount – simply comparing observations during the day with ones taken of those same stars at night would allow you to prove whether Einstein or Newton was right.”

Next year, on August 21st, 2017, millions of Americans will delight in the first total solar eclipse to go from coast-to-coast in 99 years. The path of totality will range from Oregon to South Carolina, giving more than two minutes of the Sun being blocked by the Moon’s shadow to all along its central path. During this time, not only the Sun’s corona but also the background stars, never visible otherwise during the day, will be revealed. This isn’t merely a spectacular sight, but provides an opportunity to test Einstein’s general relativity directly: by measuring the deflection of starlight caused by the gravitational presence of the Sun! Although this was famously (and successfully) undertaken in 1919, the United States had a chance to beat the rest of the world in 1918, and almost succeeded!

Come get the story you never heard of how the last great American eclipse almost shocked the world!
On August 21, 2017, the continental USA will see its first total solar eclipse in 99 years. Here's the story you didn't know.
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Ethan has left out all of the controversial parts of the story.  Why would somebody do that?

https://plus.google.com/+ChrisReeveOnlineScientificDiscourseIsBroken/posts/gaug8MFMJqy
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"From Paul Dekous on an alternative to cosmic expansion: “Alright, so here’s the obvious opposite question by a contrarian, could it be that everything is shrinking, like for ‘normal’ matter that is cooling down, evaporating energy?”

If this were the case, we could look for time variation in certain things we believe to be physically constant, like nuclear or atomic absorption/emission lines. There was a review paper by Georg Raffelt about a decade ago where he went over these possibilities, and they are constrained out to many decimal places, even at high redshift. Since things like the size of an atom are determined by certain fundamental constants (charge of an electron, planck’s constant, speed of light, etc.) you have to vary at least one to change this. The constraints on any of them changing (in any combination you can contrive) is that they are less than 7% off from their present values from the time of the CMB’s emission (380,000 years) to the present day (13.8 billion years). On the other hand, the Universe has expanded by a factor of ~1100 since then.

So no, everything cannot be shrinking."

There were so many great comments and questions this week, that we go into in-depth explanations of IceCube, supermassive black holes, the origin of the Universe, the upcoming death of Cassini and how we measure and know the great cosmic distances, and that's not even all of it! Come get an amazing dose of bonus science on this edition of our Comments of the Week!
“Failure I can live with. Not trying is what I can’t handle!” -Sanya Richards-Ross It’s been another big week here at Starts With A Bang, with stories covering the Universe near and far. I myself was on vacation, but thanks to our generous Patreon supporters, I was able to put in the resources to get a week…
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+David Andrews Thank you! Let's hope 38 is the greatest trip around the Sun for me yet!
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“To someone on a distant star, in a distant galaxy or tens of billions of light years across the Universe, we would be the ones who appeared to be in the past. To someone 100 light years away, there would never have been signs of a nuclear bomb on Earth; we would never have invented the computer; no television broadcasts would ever have been transmitted; even amplifying vacuum tubes wouldn’t have been invented yet. To someone in a galaxy a billion light years away, our Sun would appear younger and dimmer, the Earth would have housed only single-celled life, with no discernible plants or animals, and our planets’ continents would be mostly barren, covered only in ice and dirt.”

It’s been 13.8 billion years since the Big Bang for us, and when we look out at a distant object in the Universe, we’re seeing it as it was in the past. Its age — as it appears — is determined only by how long the light took for it to travel from that object to our eyes, but to someone living there, it will also appear that the Universe is 13.8 billion years old. But it is actually possible for an observer living on another planet, star or galaxy to perceive that significantly less time has passed since the Big Bang, so long as they were moving close to the speed of light relative to the CMB. Paradoxically, if they slowed their speed, they’d find that they themselves were still very young, but living in a 13.8 billion year-old Universe.

Come and discover the quirks of moving at relativistic speeds through a general relativistic Universe!
There’s no such thing as absolute time, but after 13.8 billion years, is anything relatively different?
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Dmitry Volkoff's profile photoMIke Haubrich's profile photoFlinch Fu's profile photo
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Not what we see in the telescope images. You're even eight minutes older than the Sun you see.
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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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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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