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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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"The big issue here isn’t whether oxygen is required for complex life (it probably isn’t), but rather in what percentage of cases will life wind up producing a substantial amount of oxygen? If we found an Earth-like planet (rocky, ~Earth sized, in a star’s habitable zone) with even 0.5% of the atmospheric content as molecular oxygen, it’d be quite a stretch to produce that much without having an organic process behind it. The sign isn’t necessarily a similar atmosphere; it’s an atmosphere with any appreciable amount of oxygen in it at all. The first time we find one, it’s going to be an awfully suggestive hint of life. Other explanations will exist, but that’s as close to a “smoking gun” signature as we could ask for."

Why do we look for oxygen in exo-Earth atmospheres? What does quantum weirdness mean for spinning particles? And what does the future of book-writing hold for me? Plus much, much more on this edition of our Comments of the Week!
“Love doesn’t make the world go ’round. Love is what makes the ride worthwhile.” -Franklin P. Jones It’s been such a busy time here at Starts With A Bang that we’re a day late bringing you last week’s recap! And we’ve got to get rocking on it, because there’s so much coming up to consider as well!…
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Leszek Dziędziewicki's profile photoDrazenko Djuricic's profile photoMark Ruhland's profile photo
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+Drazenko Djuricic I see your point. Well, I'm out of ideas, then. Thanx for helping me understand a bit more. 
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Ethan Siegel

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“When we look up at night could space be black because the human species can only see so far?”

Perhaps the most fundamental difference between day and night is the difference between light and dark that our eyes perceive. While everything is illuminated during the day, the night sky is completely dark, with the sole exception of the stars, galaxies and objects reflecting sunlight back at our world. You might intuit that this is simply because we can’t gather enough light to see the most distant objects in the Universe, but even if we gather arbitrarily large amounts of light, there are still dark spaces between the galaxies, where no shining objects exist. Indeed, there’s a mathematical theorem that if the Universe were of infinite size and a uniform (even if small) density, every direction you looked would eventually end on a light source. The resolution lies in two sources: the Big Bang and the limitations of our vision’s wavelength perception. Go get the whole story on this week’s Ask Ethan!
The darkness of the night sky was a mystery for generations of humans. Here's the reason why.
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"Newton’s theory predicted, if we want to be literal about it, that starlight would not deflect at all when it passed by the Sun, since light is massless. But if you assigned light a mass based on Einstein’s E = mc^2 (or m = E/c^2), you could find that starlight should deflect by 0.87″ when it passed by the Sun’s extreme outer limit. For a contrast, though, Einstein’s theory gave twice that amount: 1.75″ of deflection.

These were small numbers, but a joint expedition by Arthur Eddington and Andrew Crommelin during the 1919 solar eclipse, were able to measure to the necessary accuracy. The deflection they came up with was 1.61″ ± 0.30″, which agreed (within the errors) with Einstein’s predictions, and not with Newton’s. Newtonian gravity was busted."

Perhaps the greatest, most successful scientific theory of the past century is Einstein’s General Relativity, our theory of gravitation that has answered every challenge to it for the past 101 years with resounding success. Yet before that, Newton’s gravity did the same thing for more than twice as long! The culprit that finally brought the universal theory of ground was incredible in its simplicity: the orbit of the planet Mercury. Observations dating from the late 1500s of the planet Mercury’s position indicated a precession of its orbit of 5600" per century, while Newtonian gravity predicted 5557" per century. That less-than-1% difference proved significant, however, and it was Einstein’s General Relativity that eventually made all the difference.
Newton's theory of gravity was so successful it went unchallenged for over 200 years, until one nagging inconsistency of less than one percent changed the Universe.
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Stuart Kerrison's profile photoakhilesh mishra's profile photoVincent Sauve's profile photo
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Einstein first came up with the same value as in Newtonian theory which is not zero. Fortunately for Einstein the first expedition failed. By the time Einstein came up with the new value the expedition succeeded at getting a result. Details are on the internet and in scholarly books. It is a shame that so much history sheds off important details in the retelling.

Also, I'm unaware that Newton thought that light would be massless.  Here is what Newton wrote as quoted on page 194 in 'Subtle is the Lord...' The Science and the Life of Albert Einstein by Abraham Pais:

Do not Bodies act upon Light at a distance, and by their action bend its Rays; and is not this action (caeteris paribus) strongest at the least distance?
-- Isaac Newton: Optics, Query 1

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“By combining X-rays from Chandra with infrared data from another orbiting NASA observatory, the Spitzer Space Telescope, plus visible light information from telescopes on the ground, something special can be done. For the first time, a three-dimensional reconstruction of a supernova remnant was created using these data taken in different types of light. Because Cassiopeia A is the result of an explosion, the stellar debris is expanding radially outwards from the explosion center. Using simple geometry and the Doppler effect, we can create a 3-D model.”

The vast majority of elements beyond hydrogen found on Earth were created inside a massive star and blown back into the interstellar medium in a catastrophic supernova explosion. In a certain way, everything you’ve ever held in your hand – including another person’s hand – is you holding a dead star. But thanks to the Chandra X-ray Observatory and more than 13 years of observations of an expanding, young supernova remnant, we’re able to construct a true 3D model of one of the galaxy’s youngest dead stars. Thanks to 3D printing, you can now literally hold a dead star in your hand.

Come meet the newest Starts With A Bang contributor, Kim Kowal Arcand, and get the full story now!
By reconstructing the various layers of a supernova explosion, NASA scientists can 3D print -- and literally hold -- the remains of a cosmic catastrophe
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Ethan Siegel

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“Viewed 11 hours (1 Saturn-day) apart, we determined the hurricane migrates across Saturn at 100 kph (60 mph). These storms have occurred every 20-30 years since first seen in 1876, as hot air rises, cools and falls. 2011’s was the largest of all, large enough to contain ten-to-twelve Earths, but may be surpassed next time.”

On Earth, category 5 hurricanes cause devastation wherever they make landfall, bringing sustained winds, rain, destruction and – in many cases – casualties. But despite how strong and massive these storms can be, they’re just peanuts compared to what happens on our Solar System’s gas giants. While Saturn’s north pole and Jupiter’s great red spot are powerful, sustained storms that are far larger than anything found on our world, a world-encircling storm on Saturn that raged for over 200 days from 2010-2011 broke all the records. At its grandest, it was large enough to contain 10-to-12 Earths.

Go get the full story – and learn when that record might be broken – on today’s Mostly Mute Monday!
In 2011, a Saturnian storm put everything else to shame. But that record might not stand for long.
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Valentine Pavlov's profile photo
 
Механизм образования большого белого овала точно такой же как и БКП на Юпитере. Разница состоит только в том, что в момент описанной мной катастрофы в 3322 г до н.э. с поверхности метатвёрдого ядра у каждой из планет произошёл кумулятивный выброс. У Сатурна он превратился в "пупок" - воронкообразный вихрь на Южном полюсе, а у Юпитера - кумулятивный выброс превратился в Большое красное Пятно - вихрь на 22˚ Южной широты. У Сатурна по всему ядру пробегает ударная сферическая волна и на противоположном конце она превращается во вторичный кумулятивный выброс. Вспомните, у звёзд и галактик только парные джеты. Механизм - везде один. Отличие только в структуре носителя (нейтроны или атомы). Этот феномен на Сатурне проявляется периодически, через промежутки в 28,5 года, когда северное полушарие Сатурна сильнее всего наклоняется к Солнцу. Это значит, как в случае с БКП Юпитера воронку вихря сносит к экватору при максимальном наклоне оси Сатурна к Солнцу. Мои мысли будут понятны после изучения моих материалов.
Моя книжка: https://yadi.sk/i/AkJV6f3BfHxh2
website http://www.moon-birthday.ru
Мой фильм: https://youtu.be/hUfn7V21CbY
Как возник Плутон: https://youtu.be/mkH7CwUqWrY
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Ethan Siegel

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How will the Universe end? Will it recollapse in on itself, ending in a Big Crunch? Will it expand forever, ending in a Big Freeze? Or will it tear itself apart, ending in a Big Rip?

With the discovery of dark energy, we finally think we know, but there's always more science to be done, more possibilities to consider, and new evidence to look for to help point the way.

Come check out the newest Starts With A Bang podcast: what is dark energy, and what is the fate of the Universe?
Ethan Siegel
Starts With A Bang #8: What is Dark Energy? by Ethan Siegel
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James Carlson's profile photo
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+Ethan Siegel​​ - Nothing shows up in the CMB but that might not mean it isn't there. It could be at a different temperature. 
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Ethan Siegel

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“The curvature of space forces some light paths to take longer to arrive than others, meaning we’re seeing the same background object at different times. Most spectacularly, we’ve gotten to see a distant supernova “replay” itself due to this lensing effect.”

One of the strangest, most novel predictions of Einstein's relativity is that mass would not only curve space, but that the curved space would act like a lens. Background light traveling past this mass would become magnified, distorted and stretched. In some cases, arc, multiple images or even perfect, 360º rings would occur. Although this gravitational lensing phenomenon was theoretically predicted shortly after it was proposed, it was only in 1937 that Fritz Zwicky realized that a galaxy cluster could cause this phenomenon. 42 years later, 1979's discovery of the Twin QSO validated this picture, and hundreds of other instances of lensing have been found since.

Come see some amazing views of the strongest gravitational show the Universe has to offer!
Einstein's gravity does more than make waves in space, it curves the spacetime fabric so strongly we can see it with our naked eyes.
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Ethan Siegel

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“When we look up at night could space be black because the human species can only see so far?”

Perhaps the most fundamental difference between day and night is the difference between light and dark that our eyes perceive. While everything is illuminated during the day, the night sky is completely dark, with the sole exception of the stars, galaxies and objects reflecting sunlight back at our world. You might intuit that this is simply because we can’t gather enough light to see the most distant objects in the Universe, but even if we gather arbitrarily large amounts of light, there are still dark spaces between the galaxies, where no shining objects exist. Indeed, there’s a mathematical theorem that if the Universe were of infinite size and a uniform (even if small) density, every direction you looked would eventually end on a light source. The resolution lies in two sources: the Big Bang and the limitations of our vision’s wavelength perception. Go get the whole story on this week’s Ask Ethan!
The darkness of the night sky was a mystery for generations of humans. Here's the reason why.
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ollie clark's profile photoVincent Sauve's profile photo
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+ollie clark

I understand it just fine. Perhaps you want this:

The typical lifetime of luminous stars is 10 billion years. To fill a static universe with starlight in thermodynamic equilibrium with stars requires that stars shine continuously for 10^23 years—many, many times longer. (See: Edward Harrison, "Another look at the Big Bang," Nature, Vol. 352, 15 August 1991, p. 574).
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“With dark energy, the subtle differences of a slightly more energetic and more rapidly expanding Universe today leads to a far future where our local group is lonely and isolated, distant galaxies disappear from view and there’s no such thing as a bound, cosmic supercluster. On the largest scales, the Universe is doomed to emptiness, and it’s extra energy intrinsic to space itself that’s to blame. Part of why it was so hard to accept is because the fate of a dark energy Universe is so different — and unpalatable — from a Universe without it. Yet science doesn’t care about your personal preferences or motivations: it cares about the Universe as it actually is. The best thing we can do is listen to the story it tells us about itself, and in a way, about ourselves, too.”

The Universe has been said to be not only stranger than we imagine, but stranger than we can imagine. After the discovery of the expanding Universe, scientists considered that there was a great cosmic race from the moment of the Big Bang between the initial expansion and the force of gravity, which works to pull everything back together. It was quite a surprise when dark energy was discovered, giving us a Universe that doesn’t slow down in its expansion over time, but rather accelerates. Yet we often overlook exactly how dark energy was such a surprise. A look back at the top differences between Universes with and without dark energy, including for the fate of the local group, our local supercluster, and the far reaches of our Universe and what we can eventually see, really highlights the magnitude of just how significantly dark energy changes everything.
It was the surprise of the century when we discovered it. How would our Universe be different without it?
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"Of course, this could simply turn out to be a statistically insignificant bump that goes away with more data; it may be nothing at all. This has already happened once before, at about three times the energy. There was hint of an extra “bump” at just over 2 TeV in both detectors, as you can see for yourself. A reanalysis of the data shows there’s no significance to this signal, and that might be what we have in the 750 GeV case, too. But the possibility that it’s real is too big to ignore, and the data will come in to tell us by the end of this year. The biggest unanswered, fundamental questions in theoretical physics will get a run for the money, and all it takes is for a bump in the data to hold up a little bit longer."

The "diphoton bump" at 750 GeV is perhaps the best active signal we have for the possibility of fundamental new particles beyond the Standard Model. While the upgraded LHC should collect enough data that we'll know by the end of the year whether it looks real or goes away, there are six different possibilities for what it could be if it pans out, including: a second Higgs, dark matter, extra dimensions, neutrino physics, a composite particle or even a surprise! But don't get too excited; a similar bump at three times that energy has already gone away, and this one might be next.
We've directly detected every particle in the Standard Model, and nothing else beyond that. Yet that's only 5% of the Universe. Here's what something new might tell us.
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David Tribe's profile photoAx Ix's profile photo
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Ax Ix
 
TBF, my understanding of the 2 TeV diboson signal is that the 13 TeV run doesn't quite have the luminosity to have increased sensitivity to the signal relative to the 8 TeV run, so it's still (AFAIK) plausible that you don't see the signal at 13 TeV but you had a hint of it at 8 TeV. For instance, as of last month people were still publishing diboson papers.

As to the 750 GeV business, it might be at the edge where noise ramps up, but that doesn't really matter: it's still greater than the noise by on order of 2 sigma, and it is still in the region where 10s of events are expected, as opposed to merely a handful. There are technical issues I guess that lead some to think it's more likely to be statistical fluke then slight signal, but if that's the case it'll go away really quickly with the 2016 data and everything's settled.
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Ethan Siegel

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"What Peter A. Milne’s study found is that there are actually two classes of type Ia supernovae: some are “bluer” and some are “redder”. The bluer type are the minority nearby, where most of them are red, but are the majority type at great cosmic distances, where fewer are red. Therefore, there’s a bit of a bias to the data. However, as Milne says:

“To be clear, this research does not suggest that there is no acceleration, just that there might be less of it.”

You will notice that earlier dark energy reports had ~72-76% of the Universe’s energy in the form of dark energy, while more recent ones have it at ~66-68%. The Universe is still accelerating, dark energy is still a cosmological constant, and it’s still dominating the energy density of the Universe. There’s just a few percent less of it than we thought!"

We can't get rid of dark energy, global warming is real, black holes have jets but probably not big electric charges, and how high we can go up the periodic table just in a supernova. All this plus lots more -- including a podcast, a video and a big talk this Friday -- on this edition of our comments of the week!
“If I can’t make it through one door, I’ll go through another door – or I’ll make a door. Something terrific will come no matter how dark the present.” -Rabindranath Tagore Time continues marching on here at Starts With A Bang, just as it does everywhere. My Patreon supporters have stepped up their game, and we’re just…
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"I would like to know what are the odds of the atoms in your body coming from something else in the past? Like a 0.0001% chance that somewhere in your body an atom used to be some part of a Pharaoh in Egypt or a King in England. Can science tell us anything about how atoms are recycled around the Earth and where the atoms in my body may have come from previously?"

Inside a typical human body, beneath the organs, cells and even molecules that define us, there are atoms: some 7 × 10^27 of them in each of us. Mostly oxygen, carbon, hydrogen and nitrogen (with less than 1% of everything else combined), this tremendous number leads to an intriguing possibility: that at any given moment in your life, some of those atoms were once inside any historical living being you choose.
While the atoms you obtain through ingesting food might be incredibly well segregated depending on where you are, the atoms from Earth’s liquids or atmosphere are very well mixed, meaning that there are hundreds of billions of atoms inside of you from King Tut, trillions from Sue the T-Rex and even an atom or two in your lungs from Caesar’s last breath.
The circle of life goes down to the atomic level, and goes back as far as we're willing to look. So how many atoms do you share with a Pharaoh?
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Christian Grenfeldt's profile photo
 
people in The area must have higher chance then people who eat few exported Egyptian fruits.
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Work
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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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