esiegel

The Last Goodbye

esiegel — Sun, 29 Oct 2017 07:43:33 +0000

The Last Goodbye

What better way to say farewell than with a slew of costume pictures from this year's (coming) Halloween?

Happy Halloween 2017!

From Ethan Siegel and Starts With A Bang.

Keep looking to the Universe.

And we'll have a lifetime of wonderful things to still explore.

Goodbye, Scienceblogs, it's been an incredible almost-decade. Hope to see you all in all our other endeavors!

esiegel Sun, 10/29/2017 - 03:43

Ask Ethan: Why Did Light Arrive 1.7 Seconds After Gravitational Waves In The Neutron Star Merger?

esiegel — Sat, 28 Oct 2017 05:18:09 +0000

Ask Ethan: Why Did Light Arrive 1.7 Seconds After Gravitational Waves In The Neutron Star Merger?

"Delay is the deadliest form of denial." -C. Northcote Parkinson

Every massless particle and wave travels at the speed of light when it moves through a vacuum. Over a distance of 130 million light years, the gamma rays and gravitational waves emitted by merging neutron stars arrived offset by a mere 1.7 seconds, an incredible result! Yet if the light was emitted at the same time as the merger, that 1.7 second delay shouldn’t be there, unless something funny is afoot.

In the final moments of merging, two neutron stars don't merely emit gravitational waves, but a catastrophic explosion that echoes across the electromagnetic spectrum. The arrival time difference between light and gravitational waves enables us to learn a lot about the Universe. Image credit: University of Warwick / Mark Garlick.

While your instinct might be to attribute an exotic cause to this, it’s important to take a look at “mundane” astrophysics first, such as the environment surrounding the neutron star merger, the mechanism that produces the gamma rays, and the thickness of the matter shell that the gamma rays need to travel through. After all, matter is transparent to gravitational waves, but it interacts with light all the time! 30 years ago, neutrinos arrived four hours before the light did in a supernova; could this 1.7 second difference be an ultra-sped-up version of the same effect?

The remnant of supernova 1987a, located in the Large Magellanic Cloud some 165,000 light years away. The fact that neutrinos arrived hours before the first light signal taught us more about the duration it takes light to propagate through the star's layers of a supernova than it did about the speed neutrinos travel at, which was indistinguishable from the speed of light. Image credit: Noel Carboni & the ESA/ESO/NASA Photoshop FITS Liberator.

There’s no doubt that the first gamma rays from this neutron star-neutron star merger arrived after the gravitational waves did. But why?

esiegel Sat, 10/28/2017 - 01:18

Categories

Physical Sciences

Five Discoveries In Fundamental Physics That Came As Total Surprises

esiegel — Fri, 27 Oct 2017 05:00:54 +0000

Five Discoveries In Fundamental Physics That Came As Total Surprises

“On what can we now place our hopes of solving the many riddles which still exist as to the origin and composition of cosmic rays?” –Victor Francis Hess

It’s often said that advanced in physics aren’t met with “eureka!” but rather with “that’s funny,” but the truth is even stranger sometimes. Rather than the scientific method of: hypothesis, method, experiment, results, conclusion, revise, repeat, etc., many times throughout history, it’s been a series of surprise observations that have often led to our greatest leaps forward. When the speed of light was discovered not to differ when you moved with or against it, it was so revolutionary it was the only Nobel Prize ever awarded for a null result.

The Michelson interferometer (top) showed a negligible shift in light patterns (bottom, solid) as compared with what was expected if Galilean relativity were true (bottom, dotted). The speed of light was the same no matter which direction the interferometer was oriented, including with, perpendicular to, or against the Earth's motion through space. Image credit: A. Michelson / Michelson & Morley.

When the gold foil experiment resulted in high-energy recoils, it surprised Rutherford so thoroughly it was the most incredible thing to ever happen to him in his life. The leftover glow from the Big Bang was discovered quite by accident; the neutrino was a crazy hypothesis that many abandoned; and the discovery of the muon, perhaps the most unexpected particle of all, literally was met with a cry of, “who ordered that?” from Nobel Laureate I.I. Rabi.

The first muon ever detected, along with other cosmic ray particles, was determined to be the same charge as the electron, but hundreds of times heavier, due to its speed and radius of curvature. Image credit: Paul Kunze, in Z. Phys. 83 (1933).

These five discoveries changed the course of physics forever, but they came as total surprises to practically everyone. Sometimes, the answer is in the place you least expect.

esiegel Fri, 10/27/2017 - 01:00

Categories

Physical Sciences

Even while the world suffers, investing in science is non-negotiable

esiegel — Thu, 26 Oct 2017 05:01:10 +0000

Even while the world suffers, investing in science is non-negotiable

“I am looking at the future with concern, but with good hope.” –Albert Schweitzer

Every so often, the argument comes up that science is expendable. That we’re simply investing too much of our resources — too much public money — into an endeavor with no short-term benefits. Meanwhile, there’s suffering of all kinds, from poverty to disease to war to natural disasters, plaguing humanity all across the country and our world. Yet even while there is suffering in the world, investing in our long-term future is indispensable. This story is nothing new.

To invest in any one thing means to not invest in something else, but both science/space exploration and humanitarian relief are worthy of the investment of human resources. Image credit: NASA and WFP / Q. Sakamaki.

Back in 1970, shortly after the first Moon landing, a nun working to alleviate poverty in Africa, Sister Mary Jucunda, wrote to NASA, and begged them to stop this frivolous waste of resources, and instead to use their funding for the benefit of humanity. The letter made it all the way to Ernst Stuhlinger, then the Associate Director of Science at NASA. Stuhlinger’s response was all at once compassionate and convincing, and helped convince Jucunda — as well as skeptics everywhere — of the value that science has to offer.

The first view with human eyes of the Earth rising over the limb of the Moon. This was perhaps the greatest moment in education / public outreach for NASA until the first moon landing, and it was the picture that Stuhlinger sent to Sister Jucunda with the above letter. Image credit: NASA / Apollo 8.

Come see the full story, and read Stuhlinger’s complete, original letter, on the non-negotiable value of science to our world!

esiegel Thu, 10/26/2017 - 01:01

Categories

Policy

Merging Neutron Stars Deliver Deathblow To Dark Matter And Dark Energy Alternatives

esiegel — Wed, 25 Oct 2017 05:00:57 +0000

Merging Neutron Stars Deliver Deathblow To Dark Matter And Dark Energy Alternatives

"Dark matter is interesting. Basically, the Universe is heavier than it should be. There's whole swathes of stuff we can't account for." -Talulah Riley

One of the most puzzling facts about the Universe is that 95% of the energy in it, in the forms of dark matter and dark energy, are completely invisible, and have never been directly detected. Perhaps, the story goes, it’s our theory of gravity that’s to blame, rather than needing new components in the Universe. While dark matter and dark energy can explain a whole slew of observations, gravity modifications do a better job of explaining galactic rotation, but require altering Einstein’s theory of gravity.

The cosmic web is driven by dark matter, with the largest-scale structure set by the expansion rate and dark energy. The small structures along the filaments form by the collapse of normal, electromagnetically-interacting matter. Image credit: Ralf Kaehler, Oliver Hahn and Tom Abel (KIPAC).

But merging neutron stars provide a unique test: electromagnetic and gravitational waves both originate from an ultra-distant source over 100 million light years away. The first signals arrive separated by mere seconds, allowing us to constrain models where gravity and light are bent (and delayed) differently by the presence of masses. While theories like Bekenstein’s TeVeS and Moffat’s Scalar-Tensor-Vector predict differing delays by years, the observed arrival time difference was just 1.7s.

The various mass sources in between NGC 4993, where the neutron star-neutron star merger occurred, and the quantified delay that they cause in light/gravitational wave travel time. Image credit: Sibel Boran, Shantanu Desai, Emre Kahya, and Richard Woodard, 'GW170817 Falsifies Dark Matter Emulators'.

With these new observations, models that attempt to do away with dark matter and dark energy are largely busted, leaving only contrived, non-local modified gravity theories behind. It’s an incredible victory for Einstein and the dark Universe.

esiegel Wed, 10/25/2017 - 01:00

Categories

Physical Sciences

Dressing Up Science: Richard Feynman And The Costume Parties Of Al Hibbs (Synopsis)

esiegel — Tue, 24 Oct 2017 05:01:42 +0000

Dressing Up Science: Richard Feynman And The Costume Parties Of Al Hibbs (Synopsis)

"I was born not knowing and have had only a little time to change that here and there." -Richard Feynman

Scientists have long had a reputation for being uptight, serious, and even killjoy personalities. But 50+ years ago, Richard Feynman was forcing everyone who felt that way to challenge their assumptions. With his brash attitude and fun-seeking personality, Feynman seemingly was most at home when he was at his most outrageous.

Feynman at the Myths and Legends Party dressed as “God.” His wife, Gweneth, is dressed as Medusa, with a rock as her date. Image credit: from Christopher Sykes, No Ordinary Genius.

With Halloween on its way, what better way to celebrate than to take a look back at Feynman’s costumed antics, often taking place at the April Fools costume parties of his friend and former student, Al Hibbs? From irreverently dressing as a Ladakhi monk, Queen Elizabeth II, or even God himself, Feynman was always game for pushing the envelope and having a good time.

Richard Feynman dressed as a Ladakhi monk, painted by Sylvia Posner. Image credit: Sylvia Posner.

Come celebrate Halloween in a unique way: with the costumes of one of the 20th century’s greatest physicists, thanks to the incredible storytelling of Paul Halpern!

esiegel Tue, 10/24/2017 - 01:01

Categories

Free Thought

Star Trek: Discovery Goes Psychic & Psychedelic in 'Lethe': Season 1, Episode 6 Review (Synopsis)

esiegel — Mon, 23 Oct 2017 06:33:55 +0000

Star Trek: Discovery Goes Psychic & Psychedelic in 'Lethe': Season 1, Episode 6 Review (Synopsis)

"To burn with desire and keep quiet about it is the greatest punishment we can bring on ourselves." -Federico García Lorca

In an episode filled with Vulcan mindmelds, Klingon treachery, a spectacular nebula, themes of racial purity, and PTSD, you’d think all the ingredients were there for a spectacular episode of Star Trek: Discovery. Instead, describing it as a hot mess would be overly generous; this episode is just a disappointment as far as just about every avenue is concerned. Except for the Captain Lorca / Admiral Cornwell scenes, there’s really nothing to like about where this goes.

While running her fingers over his scars on his back while Lorca sleeps, Cornwell suddenly finds herself with a phaser pointed in her face. She understandably doubts whether Lorca is fit to command a vessel as high-priority as Discovery. Image credit: Ben Mark Holzberg/CBS © 2017 CBS Interactive.

From a psilocybin-ed out Stamets to an increasingly annoying Lilly, to a jackass version of Sarek to a blame-assigning Burnham who can’t believe that the galaxy isn’t fair, this episode is full of weak points. For a show that’s attempting to be an action/drama, this episode is very short on both the action and the drama. The Cornwell/Lorca scenes can’t save the episode, and the science part of the science fiction never even appears.

Some rare galaxies exhibit a green glow thanks to the presence of doubly ionized oxygen. This requires UV light from stellar temperatures of 50,000 K and above. Image credit: NASA, ESA, and W. Keel (University of Alabama, Tuscaloosa), of NGC 5972.

After a promising fifth episode, Star Trek: Discovery returns to its worst impulses in Episode 6, ‘Lethe’.

esiegel Mon, 10/23/2017 - 02:33

Categories

Free Thought

Comments of the Week: Final edition?

esiegel — Sun, 22 Oct 2017 06:01:53 +0000

Comments of the Week: Final edition?

“You endure what is unbearable, and you bear it. That is all.” -Cassandra Clare

Well, the cat's out of the bag. A little over a week ago, Scienceblogs announced to us writers that they no longer had the funds to keep the site operational, and so they would be shutting down. They asked us to keep quiet about this, people didn't and now you know. As of the end of this month, there will be no new articles here on Scienceblogs, and hence, no more comments of the week or synopses, or a chance to interact here. So what can you do? Well, the top thing I'd like you to do is support me on Patreon, where I can start posting all the same content I would normally post here, and you can:

comment,
respond to one another,
post your own inquiries,
respond to one another's inquiries,
and where I can respond to comments as I choose.

It's the best option I can offer, as I'm already on Tumblr, Twitter, Facebook, and even Google+, and try to respond to as many comments in as many places as I can.

Book cover for my new book: Treknology. Image credit: Voyageur Press / Quarto Publishing Group.

Also, for those of you who want to order an autographed copy of Treknology from me, I have the first copies of the book, mailers and other shipping materials are due to arrive on Tuesday, and then I can head to the post office for pricing on shipping. Expect US copies to run about $30, Canada copies to run about $40, and elsewhere in the world to be somewhere in the $50-$60 range. (Sorry, international folks!) Or, you know, just buy it now from Amazon and don't wait! (But if you get it from a third-party seller, know that neither me nor my publisher makes any money.) If you want an unbiased opinion of the book, here is the official TrekCore review. Either way, I'll have the full and final update next week. So I'm sorry to lose this forum and this archive of articles going back nearly a decade, and especially this bizarre and unique community we've built here. But like everything in the Universe, the past is gone and we can only move forward into the future as best we can.

And now, for perhaps the final time, let's dive on into our Comments of the Week!

Image credit: Wikimedia Commons user Tomruen, viahttp://en.wikipedia.org/wiki/File:Lunar_libration_with_phase_Oct_2007_4….

From Art Glick on how the near side of the Moon never sees Earth rise or set: "If you were an observer on the Moon, the Earth would hang there eternally in the same exact location, day after day, year after year, century after century. It would never move!"

Yup. I have no disagreement with this, the mild, tiny effects of lunar libration (shown above) aside. In fact, many years ago, I wrote a piece entitled It's never night on the moon, where I talk about what you'll see from the lunar surface at various locations and under various conditions. In the end, however, I do mention the one reprieve you'd get from seeing the Earth all lit up:

Image credit: JAXA / NHK, Kaguya / Selene, of a lunar eclipse as the Earth rises over the lunar limb.

During a total lunar eclipse! Pretty beautiful, no matter how you slice it.

Perceived knowledge vs. actual knowledge. Image credit: Justin Kruger and David Dunning, 1999.

From Alan G. on the fight club of reason: "The first rule of the Dunning-Kruger Club is that it’s members aren’t ware they are in the Dunning-Kruger Club."

You know, this is not only true, but I love the (sarcastic) way that John Cleese, who happens to be friends with David Dunning, puts it.

It isn't stupidity, per se, but rather expertise in any arena. For example, you may think you know all there is to know about cars, since how complicated could they possibly be? But then when your car fails to start, can you make it start immediately? On the first try? Do you know how to diagnose the problem, and which parts to check? Do you know whether it's a fuse or the starter or a problem with the ignition switch or a dead battery? And if you don't know, could you admit to yourself that you don't know, and that you need to take it to a professional? The lack of respect for those who are experts is a symptom of a larger problem, often on display here, that people think they know more than they do, and simultaneously think that bona fide experts know less than they do. So you pick the expert opinions you can find that agree with your opinions, and use that to justify your reasoning. That's thinking like a lawyer, and that approach is fruitless in science. The Universe is what it is. It's up to us to figure it out. If you want to learn, you must be humble before the Universe. Many of you do this; the rest of you can start today if you choose. It's up to you.

The gaussian curvature in three dimensions can produce interesting two-dimensional effects. If we want our 3D space curved in a particular way, we'd need to look at it from a 4th spatial dimension. Image credit: Wikimedia Commons user Sam Derbyshire.

From Frank on the curvature of the Universe: "What if Universe is surface of a 4d sphere where 3d surface (space) curved in the 4th dimension (time)?"

Well, there is curvature in the fourth dimension, but the laws of relativity tell you how the relationship between space and time occur. There's no wiggle-room or free parameters in there. If you want the Universe to be the surface of a 4D sphere, you need an extra spatial dimension. There are many physics theories that consider exactly that scenario, and they are constrained but not ruled out.

A Universe that expands and cools today, like ours does, must have been hotter and denser in the past. Initially, the Big Bang was regarded as the singularity from which this ultimate, hot, dense state emerged. But we know better today. Image credit: NASA / GSFC.

From Steve Blackband on other Big Bangs: "I am struggling with how to think about ‘other big bangs’. There is nothing, not even space or time, then there is our big bang, the expanding universe and outside of that no space and time."

You are thinking of the Big Bang as meaning "the birth of space and time." This is no longer the definition of the Big Bang, and it was always an assumption that turned out not to be very good. Here is an article I wrote years ago (before you started reading me, I bet!) that might help clear things up.

Image credit: © 2015 Shaper Helix — II Demo, via http://www.alevelsolutions.com/pure-mathematics.

From Michael Mooney on a math lesson he's about to get: "So when there is no end to how close the repeating .999 decimal gets to 1, the convention is to call it 1. But no matter how close it gets to 1, it’s still not there yet. Like .999 % of a pie still has an ever-diminishing missing slice gap."

You know, I remember being unconvinced that 0.99999.... would equal 1, so I set out to test it out. Mathematics is a wonderfully self-consistent system, so you can do this experiment yourself. You don't need advanced math. In fact, consider this your very, very first algebra lesson. Imagine we have this repeating decimal, 0.99999...., and we're going to call that x. Okay? So we can write: x = 0.999999.... and so on. As many 9s as we can write, and then they go on forever. Now, let me ask you this: what if you had ten xs all together? In other words, multiply both side of that equation, above, by 10. What do you get? 10x = 9.999999..... and again, so on. So we have two equations: x = 0.999999.... and 10x = 9.999999.... Let's subtract the first equation from the second equation. Ready? 10x - x = 9.9999999.... - 0.99999999.... So we do the subtraction, and can you see what happens here? The left side just becomes 9x, but the right side becomes... just 9, all on its own! If 9x = 9, then x = 1. Now, I had the same question as you, once, but once I learned how to do this proof, there was no more questioning. I had proven it, just as countless others before me had, and countless others after me will. x, which we had defined as 0.99999.... is also provably equal to 1.

The USS Discovery, NCC-1031, is perhaps a very thinly-veiled reference to Star Trek's 'Section 31,' and things could get a lot darker before anyone goes back to being an explorer. Image credit: Star Trek / CBS Press Kit.

From Sinisa Lazarek on Swear Trek: "– we get a first ever “FUCK” word in Star Trek… ever. And that by a Cadet in front of officers. Not only is phrase never spoken in ST universe… but we even get more fucks with 2 other people there. Like ST script was only missing that word, and now we’ll multiply."

Yeah, Tilly swears. And then others do it, too. Honestly, I didn't even notice until someone I was watching it with pointed it out. But Tilly is pretty much the audience surrogate: an awkward superfan of everything in the show who gets to be roommates with Michael Burnham. I seriously think Burnham could blow up the entire Earth and Tilly would still be her fan. I am doing my best with this show to "chew on the meat and throw away the bones," otherwise I think, like many others, I'll wind up disappointed.

The warrior that Burnham kills is given the traditional Klingon death ritual... and then predictably used as a political tool to start a war. Image credit: Jan Thijs/CBS © 2017 CBS Interactive.

From Denier on the role of the Klingons in episode 5: "Klingons were back to being one dimensional villains who all spoke English and served their regular role to move the plot along. That, more than anything else, made this episode better."

You know, I did notice this change, and I liked it very much. Hopefully, we'll see less of the fundamentalist theocrat Klingons speaking Klingon and a lot more of... well, everything else.

Burnham, in the first two episodes alone, gets a fatal dose of radiation poisoning, activates a Klingon probe and kills its guardian, mutinies against and knocks out the Captain, and then kills the Klingon leader. Image credit: Jan Thijs, © 2017 CBS Interactive.

From Anonymous Coward on the end of Scienceblogs: "Ethan, I read both you and Orac here on ScienceBlogs and Orac has just mentioned that ScienceBlogs will soon be shutting down for good at the end of the month. There going to be another place where we can see your article summaries and make discussion like this, other than on Forbes itself?"

Unfortunately, unless you come and join my Patreon (asking at least $1 a month is a lot, I know), there's nothing else quite like what we've been doing here. I used to run startswithabang.com and would consider it again, but I simply don't have the time to run my own blog and deal with all the hacks and updates that routinely happen on top of all the things I'm creating at this time.

In the final moments of merging, two neutron stars don't merely emit gravitational waves, but a catastrophic explosion that echoes across the electromagnetic spectrum. Image credit: University of Warwick / Mark Garlick.

From Michael Tiemann on neutron star collisions: "When two neutron stars have been circling each other for 11 billion years, what is the relative velocity of their “collision” when they do collide?"

About a third the speed of light. Pretty impressive, don't you think?

Geordi's VISOR from Star Trek: TNG. Image credit: Memory Alpha.

From Gail Farley on a new Treknology that's been developed quite recently: "Thank you for educating people about technology on Coast to Coast last night and in your book. You stated last night that you were concerned about a technology that can implant memories, and effect the body, including the loss of sight. Please tell me what kind of technology that is, so that I can research it further."

In 2012, a group at Monash University build a working device to transmit optical information directly to the wearer's brain, through an implant in the visual cortex. If you want to get even deeper into the real-life science than my book does, you can read the 2016 article: Monash Vision Group’s Gennaris Cortical Implant for Vision Restoration.

We knew that when two neutron stars merge, as simulated here, they create gamma-ray burst jets, as well as other electromagnetic phenomena. But whether you produce a neutron star or a black hole, as well as how much of a UV/optical counterpart is produced, should be strongly mass-dependent. Image credit: NASA / Albert Einstein Institute / Zuse Institute Berlin / M. Koppitz and L. Rezzolla.

From Omega Centauri and Michael Kelsey on the newest LIGO/Virgo/EM discoveries: "(1) What is the estimate of the NS masses? (2) How did they come up with the age of the NS system? (3) What is the estimated rate of mergers per cube a billion light years on a side? (4) If both NS are near the minimum mass of a NS, can we get a NS rather than BH. (5) Do we expect of significant gamma-ray burst from a BH NS merger? 1) About a solar mass each. 2) Use PSR B1913+16. 3) Not as high as for BH mergers. 4) Yes. 5) Yes."

You may also really, really appreciate the information I gleaned from the theoretical end from an interview a few days ago with Chris Fryer at Los Alamos. That article, in case you missed it, is here.

The quasar QSO J0842+1835, whose path was gravitationally altered by Jupiter in 2002, allowing an indirect confirmation that the speed of gravity equals the speed of light. Image credit: Fomalont et al. (2000), ApJS 131, 95-183, via http://www.jive.nl/svlbi/vlbapls/J0842+1835.htm.

From CFT on the speed of gravity: "IF gravity traveled at the speed of light, how do you explain the actual orbits of planets around the sun?"

Not that you'll learn anything from this, but the actual answer is that, in the context of General Relativity, if gravity moved at any other speed, we wouldn't get the orbits that we see! I wrote an article on the indirect evidence (independent of any gravitational wave detections) that the speed of gravity is equal to the speed of light some time ago, and all that analysis is still valid today. Since, CFT, you're such a fan of getting info from "real" experts, you know, experts not named Ethan, maybe you'll listen to the research of the awesome GR expert Steve Carlip, who wrote up this account of the actual evidence you claim is missing?

The soft capture mechanism installed on Hubble (illustration) uses a Low Impact Docking System (LIDS) interface and associated relative navigation targets for future rendezvous, capture, and docking operations. The system’s LIDS interface is designed to be compatible with the rendezvous and docking systems to be used on the next-generation space transportation vehicle. Image credit: NASA.

From Elle H.C. on kickstarting the saving of Hubble: "Get a Kickstarter-thingy and you might get enough funding by the end of the month."

Well, let's do the math on that. The most Kickstartered-thing ever, as far as I know, is Pebble Time, which is a smartwatch company that had a couple of successful Kickstarters. They raised just slightly north of $20 million. Only three things (two of which are Pebble) have crested the $10 million mark, and there are only about a dozen more that are over $5 million. On the other hand, to boost Hubble would require approximately $500 million, if I'm ballpark-estimating appropriately. You are way better off going to an Elon Musk or a Richard Branson or Roscosmos if NASA won't do it. That sort of money just doesn't seem feasible.

This diagram shows the novel 5-mirror optical system of ESO's Extremely Large Telescope (ELT). Before reaching the science instruments the light is first reflected from the telescope's giant concave 39-metre segmented primary mirror (M1), it then bounces off two further 4-metre-class mirrors, one convex (M2) and one concave (M3). The final two mirrors (M4 and M5) form a built-in adaptive optics system to allow extremely sharp images to be formed at the final focal plane. Image credit: ESO.

From lyle on the oversimplified joke-science that is IFLS: "Further if this article is correct : http://www.iflscience.com/space/telescopes-ground-may-be-cheaper-hubble-shows-why-they-are-not-enough/ “When E-ELT observations start in 2024, the state-of-the-art correction for atmospheric distortion will allow it to provide images 16 times sharper than those taken by Hubble."

This is the big problem you get when you get your science from not only non-scientists, but non-journalists. They are, over at IFLS, basically news readers and re-writers, and they rarely know (or care) enough to put it in context. I've written, recently, about the ELT at length, and it's true that it will have 16 times the resolution of Hubble at certain wavelengths and for certain classes of observations in the cases where atmospheric distortion can be 100% removed, which is never. The scientific fact is there are a whole slew of observations, including UV observations and IR observations, that Hubble can make that no ground-based observatory can. Hubble's lack of atmospheric distortion is incredible, and something no ground-based observatory, even with the best AO there is, can match. In summary, F IFLS, and please don't ever expect anything beyond superficial, partially correct information from them.

The possibility of having artificial gravity is tantalizing, but it is predicated on the existence of negative gravitational mass. Antimatter may be that mass, but we don't yet know, experimentally. Image credit: Rolf Landua / CERN.

From Omega Centauri on the problem of artificial gravity: "Even if anti-matter produces anti-grav, you would need a heck of a lot of it to get 1G. How much mass is needed to create 1G (depends on density, at the average density of about 5 the mass of the earth is needed. Denser matter, and you could get by with less. But, its a huge amount no matter how you do it, and presumably it is also inertial mass, which kind of makes spacecraft difficult to accelerate."

All true. But I will say that I am much more excited about a problem that it is physically possible to solve than one that isn't, and antigravitating antimatter would enable that transformation when it comes to artificial gravity. Now, who has the stable white dwarf matter to build your spaceship out of... and the anti-white-dwarf antimatter, too?

Captain Gabriel Lorca aboard the bridge of the Discovery, during a simulated combat mission with the Klingons. Image credit: Jan Thijs/CBS © 2017 CBS Interactive.

From Douglas Robertson on artificial gravity vs. life support: "What I find funny about fictional artificial gravity is when they are experiencing an emergency. All life support is shut down, but they still have gravity."

Must be a passive system, then. See, not so hard to explain!

Neutron stars, when they merge, can exhibit gravitational wave and electromagnetic signals simultaneously, unlike black holes. But the details of the merger are quite puzzling, as the theoretical models don't quite match what we've observed. Image credit: Dana Berry / Skyworks Digital, Inc.

And finally, from Adam on the origin of gamma rays from the NS-NS merger: "Could the omnidirectional gamma ray bursts be coming from the ejecta themselves? It seems like the process of going from a lump of neutronium to all those heavy elements is a lot like the fission reaction of an atomic bomb – just one the with the mass of 30 to 40 Jupiters."

I doubt it. The ejecta occur on the timescale of hundreds of milliseconds, but the gamma ray burst occurred 1.7 seconds after the gravitational wave signal arrived, so I don't think that's a dealbreaker but I also don't think that lines up. Moreover, the ejecta come mostly from wind interactions in a disk surrounding the neutron stars, so I also don't think that's as likely a source as the ultra-high energies released in the star-star collision. I think it's likely where the surfaces collide that produces such a high-energy, transient burst, but as with all things science, it's going to take some additional evidence to know for certain! Thanks for a great everything, everyone, and we'll have one final just-for-you article next weekend. See you then!

esiegel Sun, 10/22/2017 - 02:01

Categories

Free Thought

Ask Ethan: How sure are we that the Universe is 13.8 billion years old?

esiegel — Sat, 21 Oct 2017 05:00:18 +0000

Ask Ethan: How sure are we that the Universe is 13.8 billion years old?

“Normal science, the activity in which most scientists inevitably spend almost all their time, is predicated on the assumption that the scientific community knows what the world is like.” -Thomas S. Kuhn

For all of human history, the biggest questions have fascinated us. Where did the Universe come from? How old is it? And what is its ultimate fate? Once relegated to the realm of theologians, poets, and philosophers, science has brought us closer than ever to the answers. But scientific revolutions have occurred before, in many cases significantly changing the answers to these and other inquiries. How certain are we that this won’t happen again?

The Sun, the Earth, and the history of life on our world all have a consistent age today, but back in the late 1800s, the evidence for the age of the Earth suggested it was significantly older than the Sun. Image credit: NASA, ESA, and ISS Expedition 37.

When it comes to the question of the age of the Universe, presently estimated at 13.8 billion years, there are many uncertainties that could come into play. Dark energy could evolve over time, fundamental constants might not be constant, or today’s fundamental particles might be broken up into smaller components. Additionally, we could have flaws in the expansion rate or composition of our Universe, or even alter General Relativity.

The four possible fates of our Universe into the future; the last one appears to be the Universe we live in, dominated by dark energy. What's in the Universe, along with the laws of physics, determines not only how the Universe evolves, but how old it is. Image credit: E. Siegel / Beyond The Galaxy.

But it really looks like 13.8 billion years is safe, to within perhaps 2% at most. How can we be so confident?

esiegel Sat, 10/21/2017 - 01:00

Categories

Physical Sciences

Seeing One Example Of Merging Neutron Stars Raises Five Incredible Questions

esiegel — Fri, 20 Oct 2017 05:27:54 +0000

Seeing One Example Of Merging Neutron Stars Raises Five Incredible Questions

"O. Hahn and F. Strassmann have discovered a new type of nuclear reaction, the splitting into two smaller nuclei of the nuclei of uranium and thorium under neutron bombardment. Thus they demonstrated the production of nuclei of barium, lanthanum, strontium, yttrium, and, more recently, of xenon and caesium. It can be shown by simple considerations that this type of nuclear reaction may be described in an essentially classical way like the fission of a liquid drop, and that the fission products must fly apart with kinetic energies of the order of hundred million electron-volts each." -Lise Meitner

Now that we've observed merging neutron stars for the first time, in many different wavelengths of light as well as in gravitational waves, we've got a whole new world of data to work with. We've independently confirmed that gravitational waves are real and that we can, in fact, pinpoint their locations on the sky. We've demonstrated that merging neutron stars create short gamma ray bursts, and shown that the origin of the majority of elements heavier than the first row of transition metals comes primarily from neutron star-neutron star mergers.

This color-coded periodic table groups elements by how they were produced in the universe. Hydrogen and helium originated in the Big Bang. Heavier elements up to iron are generally forged in the cores of massive stars. The electromagnetic radiation captured from GW170817 now confirms that elements heavier than iron are synthesized in large amounts the aftermath of neutron star collisions. Image credit: Jennifer Johnson / SDSS.

But the new discovery raises a ton of questions, too. Seeing this event has presented theorists with a number of new challenges, ranging from the event rate being some ten times as great as expected to much more matter being ejected than we'd thought. And what was it that was left behind? Was it a neutron star? A black hole? Or an exotic object that's in its own class?

We knew that when two neutron stars merge, as simulated here, they create gamma-ray burst jets, as well as other electromagnetic phenomena. But whether you produce a neutron star or a black hole, as well as how much of a UV/optical counterpart is produced, should be strongly mass-dependent. Image credit: NASA / Albert Einstein Institute / Zuse Institute Berlin / M. Koppitz and L. Rezzolla.

There are some great advances that the future will hold for gravitational wave and neutron star astronomy, but it's up to theorists to explain why these objects behave as they do.

esiegel Fri, 10/20/2017 - 01:27

Categories

Physical Sciences