“Sometimes I even now feel like a stranger in my country. But I knew there would be problems because I had seen the world… Freedom is good, but it is not easy.” -Katarina Witt
Yes, as always, as another week goes by at Starts With A Bang! there have been a huge number of great stories we’ve covered. In addition, we’ve now recorded sixteen Starts With A Bang Podcast episodes thanks to your Patreon support, and if you’re local to the Pacific Northwest, we have some fun events coming up, including a public talk at 7:30 at OMSI on February 20th on the controversy over the expanding Universe, a Guest of Honor appearance at NorWesCon in April, and I’ll be at Brooks Winery in the path of the eclipse for the big event in August! That said, let’s take a look back on this past week of incredible science stories:
- What is Spacetime? (for Ask Ethan),
- Watch: Four gas giants in orbit around another star for the first time (for Mostly Mute Monday),
- How thinking like a scientist can improve your daily life,
- Pan-STARRS solves the biggest problem facing every astronomer,
- Heisenberg’s astrophysics prediction finally confirmed after 80 years, and
- The strangest moon in the Solar System.
There’s so much to get to let’s not delay, and instead dive right into our comments of the week!
The ‘institute of noetic sciences’, or IONS, is a good example of counterfactual information. Image credit: screenshot from http://noetic.org/.
From CFT on redefining words: “Facts are easy, you just remember them. Determining if they are actually true or not is another matter altogether.”
No. A fact is not “something that you’re told/taught that you remember and regurgitate.” That might be how you get your facts, but being told or taught something doesn’t make the thing you’re told factual. The veracity of the thing being told determines its factualness. And so many of us want a quick and easy answer that we can agree with that we often choose non-factual information (or incomplete facts, or counterfactuals) to confirm our own preconceptions. If you think “oh, I’ll just remember this fact” when you encounter some information, you’re not fact-finding at all.
Heat-trapping emissions (greenhouse gases) far outweigh the effects of other drivers acting on Earth’s climate. Source: Hansen et al. 2005, Figure adapted by Union of Concerned Scientists.
From dean on climate science: “The evidence for climate change is overwhelming, as studies and data continue to show, but the communication of that fact has been poorly done – hence the anti-science folks claiming Mann’s analysis has never been supported, or is flawed, or the asinine “sample size of 1” argument the very desperate deniers use.”
From a scientific point of view, the communication has been very well done! It’s been straightforward, accurate (where about 5-10% of claims are overblown and 5-10% are far too mild, with 80-90% right in the mainstream), representative of scientific thought and publicly available. But the disinformation campaign has been extremely successful among a large segment of the population. I do think it’s as simple as that. Add in political bias/polarization, ideology, tribalism and money equaling speech, and that gives us our situation today.
Warming rate of the Earth, as of 2011, and how it changes depending on which start year you choose. Image credit: tamino of http://ift.tt/sVyg4V.
From Denier on those lying climate scientists: “This same sample size limitation affects many aspects of Climate Science which is why Climate Science is so reliant on computer models. Those simulated planets are not yet perfect. They make predictions, but those predictions have sizable error bars because the Scientists know they’re not perfect. The deviation between projection and reality is a common soft target, and Ethan has written in defense of the predictions many times summing it up as ‘you just have to be honest about the error bars’.
Climate Scientists are not honest about the error bars.”
That there are uncertainties — quantified accurately in the literature and in the models (i.e., your dishonesty claim is false) — does not mean the consensus predictions are unreliable. That we have to rely on simulations to understand the climate does not mean the simulations are unscientific or unreliable. This is the difference between science and politics, where in the latter case you make your story full of convincing-sounding points that don’t reflect the scientific truth. For example, here’s what Drew Shindell said about the (false) claim that maybe human’s aren’t the main contributor to Earth’s warming, which is still being debated, publicly, by large swaths of the country:
Of all the natural drivers, and everything we know that works on long time scales that has ever affected climate in the past, all those things have been ruled out. Beyond a reasonable doubt, it has to be human activities.
So if you want me to call out people when they tout incorrect, misleading or just wrong information on all sides — and to correct my own mistakes when I make them — which I have a long record of doing, you should be consistent and do the same. For the people “on your own side” and for yourself. If you’re TL;DR-ing, yes, there are uncertainties, no there’s no dishonesty about it, and no, the uncertainty about the models’ predictive power doesn’t change the conclusion about what’s real, what its cause is, or what the future holds if we do nothing.
The fabric of the Universe, spacetime, is a tricky concept to understand. But we’re up to the challenge. Image credit: Pixabay user JohnsonMartin.
From John Duffield on whether space or spacetime is curved: “the article says “curved space” when it ought to say curved spacetime. The space around the Earth is not curved, instead it’s inhomogeneous, and when you plot the inhomogeneity, your plot is curved.”
Hi John, long time no see. Or rather, long time without hearing you talk about the difference between space and spacetime, which you are sometimes correct about and sometimes not. In this case, you’re not.
Both space and spacetime can be curved, both mathematically and physically, as in General Relativity. Jonah Miller has an excellent post about geodesics, spacetime’s curvature and how that manifests gravitationally. Yes, spacetime is curved; yes, space is inhomogeneous around Earth. But also, the space around Earth is curved as well, which is why light rays are deflected by masses in this Universe. The article could have said curved spacetime and would also have been correct, but curved space is absolutely right. If you don’t believe me, do the 3+1 decomposition yourself in a weak gravitational field (or Schwarzschild space, if you prefer) and see for yourself!
Four gas giants orbiting the star HR 8799. Image credit: Jason Wang / Christian Marois.
From CFT on failed stars and binary systems: “I remember at one time Carl Sagan said that gas giants were failed stars…and that many solar systems were binary. Are binary star systems then both ‘cooler’ stars since both stars are basically hydrogen? Or is there evidence of a mixed binary system where one can be hot, the other cool?”
The temperature of a star, to an excellent approximation, is determined by its mass. How successful (or unsuccessful) you are at becoming a star determines what your mass is. You can have mismatched binaries where one is cool and one is hot, you can have equally successful binaries of nearly the same mass, or you can have the situation we do here: where Jupiter is the closest thing to a failed star we have, but it still needed about 70-80 times its mass if it wanted to become a star. There are a lot of “chances” in the Universe, and nature exhibits a wide diversity of systems that it delivers to us.
Image credit: Amy S. Lo et al. (2010), from the Starshade Technology Development Astro2010 Technology Development White Paper.
From PJ on being amazed by what we can see: “Friggin amazing what we are able to see at the present. The near future will be even more spectacular; given higher resolution means.”
This direct imaging technique is incredible, but it relies on a coronagraph, which blocks the light from the parent star but creates a diffraction pattern around it that makes only the largest, most well-separated planets directly visible. The next advance is to create a starshade in space that can fly at an extraordinarily large distance from a space telescope, upping the contrast from about 10^6 to 10^10, making planets 10,000 times as faint visible. Earth-like planets in the habitable zones of stars, here we come! Coming, NASA-funding and prioritization dependent, to either the 2030s or, potentially, WFIRST in the 2020s if we get lucky!
The XKCD version of Free Speech. Image credit: xkcd/Randall Munro, from https://xkcd.com/1357/.
From Denier on free speech: “One of the most contentious speakers on the college circuit right now is Milo Yiannopoulos. For those unfamiliar, Milo is a conservative, white gay male who exclusively dates black guys. His lectures are often anti-Feminist, anti-Safe Space, anti-Identity Politics, and religiously bigoted against followers of Islam.
Milo is not Fascist. He’s not a Nazi. He’s not Alt-Right. He’s not racist. Milo is not a White Nationalist.
https://www.youtube.com/watch?v=ywmd8kR-AmI
Wherever Milo Yiannopoulos speaks, protesters come out in force to try and shut down his lectures. They carry signs and chant various accusations of Fascism along with all of the above. These charges are directed not only at Milo but at anyone going to see Milo.”
The last time you brought up free speech issues and the first amendment (no idea why it’s being brought up here, but whatever), I cautioned you against strawmanning my position and encouraged you to steelman me instead, or at least take what I say at face value. But we’re back to strawmanning, I see.
You are welcome to tell me what you think Milo is or isn’t, but I am not so old that I don’t remember being the ages of 10-13. Where kids first became mean, violent and cruel to one another not to sate their own personal needs (money, candy, the thrill of violence, etc.), but to gain social status instead. I don’t care why Milo does what he does or says what he says; what I see is someone who’s a minority in one way (he’s gay) bully and beat down people — in a public forum — who are minorities in ways he is not. Who are not part of his in-group. He bullies trans people. He bullies muslims. He bullies women. He bullies poor people. And he does it knowing full well that this is his ticket to (partial) acceptance and (loud) adulation within his in-group. Which includes all of the people in the “Milo is not…” groups you list above.
I disagree with Milo in almost everything he’s ever said. I support not inviting him to your campus. I support protesting his appearance. You know, exercising your right to free speech. But I don’t condone the violence in the protests against him. I condemn the actions of the black bloc protesters, as do most people across the political and ideological spectrum. I also don’t conflate “liberals” or “progressives” with a violent minority, just as I don’t conflate “muslims” with the radical islamic terrorists or “actual Nazis like Steve Bannon” with everyone who voted for Donald Trump. I hope you can stop conflating an article that contends, “scientists should adhere to this simple code of ethics in their scientific pursuits and their presentation of science to the public” with a loss of your first amendment rights to act as a private citizen.
But I think your real point comes a few comments later: “The idea Ethan keeps coming back to lately is how to oppress society.”
Society is doing a great job of oppressing a large number of its members. That is an injustice that I see that I believe needs to be righted. So let me ask you what you see as positive ways forward on that front, since elevating those marginalized but valuable voices equals oppression to you. How do we ensure that racial profiling stops? How do we protect the rights of women to control their own bodies: specifically for contraception and access to abortion services? How do we protect rape victims from being further victimized by the legal process? I am starting to think that you and I have very different views on what a “right” is, and that may be the root of where we differ on oppression as well. There is room to argue about that, I suppose, but I think it goes back to something that Donald Trump said in his inauguration speech.
“הִנֵּה מַה-טּוֹב, וּמַה-נָּעִים– שֶׁבֶת אַחִים גַּם-יָחַד.”
Do you recognize that? It’s Psalm 133, my favorite of all the Psalms. (Trump read a translation of it at the inauguration.) Literally, it means “how good and how blessed it is when brothers can live together as one.” I think if you interpret brothers as “people like me” or “my actual brothers” or “the people on my side but not the ones not on my side,” you miss the meaning of “together as one.” We are all children of planet Earth, and I want to see a better planet and a better future for us all. For. Us. All. That is what I’m working to build.
Pan-STARRS1 Observatory atop Haleakala Maui at sunset. Image credit: Rob Ratkowski.
From Wow on collecting every photon: “But not even the best black coating can capture every photon.
Not that every one is required.”
There is a difference between collecting and utilizing. It’s worth remembering that telescopes have not increased all that much in size over the past 100 years. The telescope that Hubble used to discover the expanding Universe — the 100 inch (2.5m) Hooker telescope — is larger than the Hubble Space Telescope’s primary mirror. It was commissioned in 1917. One twice the diameter (the Hale telescope) was commissioned in 1948, and today’s record holders are about twice that diameter still. But the big improvements are in CCDs and cameras. Instead of collecting between 0.1% and 1% of the light, which is what old photographic plates did, we can now use the technique of photomultiplication — where photons strike a surface and an electron gets kicked or excited, creating a cascade and an unmistakable electric current — to efficiently use about 20% of the incident light.
But there is still noise, and that makes the signal hard to pull out of the noise. Once you know where and how something exists, you can go back and clearly pull out a marginally statistically significant signal that would have been ambiguous previously. After the 2011/2012 discovery of the Higgs, they were able to go back to 1988 Fermilab data and identify the first Higgs event; going back through telescope data is a similar process. As time progresses, materials science improves and gets applied to camera technology, we hope to come ever closer to the 100% goal. But noise will always be present.
Light coming from the surface of a neutron star can be polarized by the strong magnetic field it passes through, thanks to the phenomenon of vacuum birefringence. Detectors here on Earth can measure the effective rotation of the polarized light. Image credit: ESO/L. Calçada.
From Anonymous Coward (and echoed by Sinisa Lazarek) on the weird vacuum birefringence effect: “By the way, does the very powerful magnetic field actually change the polarization of the light from the neutron star? As the abstract indicates the emission of light from the neutron star is thermal and thus it should be emitting light at all wavelengths and polarizations. Does the magnetic field actually change the polarization of the light as it leaves the star, or does it have an effective polarization-dependent refractive index, the way a birefringent crystal like calcite does? The article seems to indicate the former, but I’m not sure this is true.”
There is another, older effect which we see all the time: Faraday rotation, which explains how magnetic fields in a medium cause the polarization of light to rotate in a particular fashion. You can measure galactic magnetic fields this way by looking up, away from the galaxy, then moving down, down, down, into the galactic plane, and then out again, and looking at how the polarization of light changes. But this only happens in a dielectric medium, and tells you the combined properties of the magnetic field and of the free (ionized) electron content, which are primarily responsible for the Faraday rotation itself.
But this effect, of vacuum birefringence, is non-classical and purely quantum in nature. It is a much more subtle effect that is similar, but occurs in empty space itself. Yes, the magnetic field actually changes the polarization of light, and it is wavelength dependent. Were these X-rays instead of visible light, the polarization would be ~100% instead of ~15%. It’s an incredible confirmation of this quantum prediction.
The two-toned Iapetus is the strangest known moon in all the Solar System. Image credit: NASA / JPL-Caltech / Space Science Institute / Cassini.
And finally, from Sinisa Lazarek on Iapetus: “The first thought that came to mind when I saw the first image is: Rolling stone gathers no moss”
That’s actually quite a profound thought, and speaks to the point that Iapetus is tidally locked. If Earth orbited Saturn at the distance of Iapetus, it would be locked, too. This is very meaningful when you consider potentially habitable planets orbiting M-class stars; they’re all locked as well. The timescale to locking is very short for these worlds: 10^5 to 10^7 years, while our Solar System is billions of years old. If Iapetus weren’t locked, it would be more uniformly covered in Phoebe’s soot, except for at the poles. As it stands, you can conclude quite clearly that this planet isn’t rolling, and it’s a demonstration of the incredible power of tides.
Thanks for a great and thoughtful week, and looking forward to the next one!
from ScienceBlogs http://ift.tt/2lcvbr1
“Sometimes I even now feel like a stranger in my country. But I knew there would be problems because I had seen the world… Freedom is good, but it is not easy.” -Katarina Witt
Yes, as always, as another week goes by at Starts With A Bang! there have been a huge number of great stories we’ve covered. In addition, we’ve now recorded sixteen Starts With A Bang Podcast episodes thanks to your Patreon support, and if you’re local to the Pacific Northwest, we have some fun events coming up, including a public talk at 7:30 at OMSI on February 20th on the controversy over the expanding Universe, a Guest of Honor appearance at NorWesCon in April, and I’ll be at Brooks Winery in the path of the eclipse for the big event in August! That said, let’s take a look back on this past week of incredible science stories:
- What is Spacetime? (for Ask Ethan),
- Watch: Four gas giants in orbit around another star for the first time (for Mostly Mute Monday),
- How thinking like a scientist can improve your daily life,
- Pan-STARRS solves the biggest problem facing every astronomer,
- Heisenberg’s astrophysics prediction finally confirmed after 80 years, and
- The strangest moon in the Solar System.
There’s so much to get to let’s not delay, and instead dive right into our comments of the week!
The ‘institute of noetic sciences’, or IONS, is a good example of counterfactual information. Image credit: screenshot from http://noetic.org/.
From CFT on redefining words: “Facts are easy, you just remember them. Determining if they are actually true or not is another matter altogether.”
No. A fact is not “something that you’re told/taught that you remember and regurgitate.” That might be how you get your facts, but being told or taught something doesn’t make the thing you’re told factual. The veracity of the thing being told determines its factualness. And so many of us want a quick and easy answer that we can agree with that we often choose non-factual information (or incomplete facts, or counterfactuals) to confirm our own preconceptions. If you think “oh, I’ll just remember this fact” when you encounter some information, you’re not fact-finding at all.
Heat-trapping emissions (greenhouse gases) far outweigh the effects of other drivers acting on Earth’s climate. Source: Hansen et al. 2005, Figure adapted by Union of Concerned Scientists.
From dean on climate science: “The evidence for climate change is overwhelming, as studies and data continue to show, but the communication of that fact has been poorly done – hence the anti-science folks claiming Mann’s analysis has never been supported, or is flawed, or the asinine “sample size of 1” argument the very desperate deniers use.”
From a scientific point of view, the communication has been very well done! It’s been straightforward, accurate (where about 5-10% of claims are overblown and 5-10% are far too mild, with 80-90% right in the mainstream), representative of scientific thought and publicly available. But the disinformation campaign has been extremely successful among a large segment of the population. I do think it’s as simple as that. Add in political bias/polarization, ideology, tribalism and money equaling speech, and that gives us our situation today.
Warming rate of the Earth, as of 2011, and how it changes depending on which start year you choose. Image credit: tamino of http://ift.tt/sVyg4V.
From Denier on those lying climate scientists: “This same sample size limitation affects many aspects of Climate Science which is why Climate Science is so reliant on computer models. Those simulated planets are not yet perfect. They make predictions, but those predictions have sizable error bars because the Scientists know they’re not perfect. The deviation between projection and reality is a common soft target, and Ethan has written in defense of the predictions many times summing it up as ‘you just have to be honest about the error bars’.
Climate Scientists are not honest about the error bars.”
That there are uncertainties — quantified accurately in the literature and in the models (i.e., your dishonesty claim is false) — does not mean the consensus predictions are unreliable. That we have to rely on simulations to understand the climate does not mean the simulations are unscientific or unreliable. This is the difference between science and politics, where in the latter case you make your story full of convincing-sounding points that don’t reflect the scientific truth. For example, here’s what Drew Shindell said about the (false) claim that maybe human’s aren’t the main contributor to Earth’s warming, which is still being debated, publicly, by large swaths of the country:
Of all the natural drivers, and everything we know that works on long time scales that has ever affected climate in the past, all those things have been ruled out. Beyond a reasonable doubt, it has to be human activities.
So if you want me to call out people when they tout incorrect, misleading or just wrong information on all sides — and to correct my own mistakes when I make them — which I have a long record of doing, you should be consistent and do the same. For the people “on your own side” and for yourself. If you’re TL;DR-ing, yes, there are uncertainties, no there’s no dishonesty about it, and no, the uncertainty about the models’ predictive power doesn’t change the conclusion about what’s real, what its cause is, or what the future holds if we do nothing.
The fabric of the Universe, spacetime, is a tricky concept to understand. But we’re up to the challenge. Image credit: Pixabay user JohnsonMartin.
From John Duffield on whether space or spacetime is curved: “the article says “curved space” when it ought to say curved spacetime. The space around the Earth is not curved, instead it’s inhomogeneous, and when you plot the inhomogeneity, your plot is curved.”
Hi John, long time no see. Or rather, long time without hearing you talk about the difference between space and spacetime, which you are sometimes correct about and sometimes not. In this case, you’re not.
Both space and spacetime can be curved, both mathematically and physically, as in General Relativity. Jonah Miller has an excellent post about geodesics, spacetime’s curvature and how that manifests gravitationally. Yes, spacetime is curved; yes, space is inhomogeneous around Earth. But also, the space around Earth is curved as well, which is why light rays are deflected by masses in this Universe. The article could have said curved spacetime and would also have been correct, but curved space is absolutely right. If you don’t believe me, do the 3+1 decomposition yourself in a weak gravitational field (or Schwarzschild space, if you prefer) and see for yourself!
Four gas giants orbiting the star HR 8799. Image credit: Jason Wang / Christian Marois.
From CFT on failed stars and binary systems: “I remember at one time Carl Sagan said that gas giants were failed stars…and that many solar systems were binary. Are binary star systems then both ‘cooler’ stars since both stars are basically hydrogen? Or is there evidence of a mixed binary system where one can be hot, the other cool?”
The temperature of a star, to an excellent approximation, is determined by its mass. How successful (or unsuccessful) you are at becoming a star determines what your mass is. You can have mismatched binaries where one is cool and one is hot, you can have equally successful binaries of nearly the same mass, or you can have the situation we do here: where Jupiter is the closest thing to a failed star we have, but it still needed about 70-80 times its mass if it wanted to become a star. There are a lot of “chances” in the Universe, and nature exhibits a wide diversity of systems that it delivers to us.
Image credit: Amy S. Lo et al. (2010), from the Starshade Technology Development Astro2010 Technology Development White Paper.
From PJ on being amazed by what we can see: “Friggin amazing what we are able to see at the present. The near future will be even more spectacular; given higher resolution means.”
This direct imaging technique is incredible, but it relies on a coronagraph, which blocks the light from the parent star but creates a diffraction pattern around it that makes only the largest, most well-separated planets directly visible. The next advance is to create a starshade in space that can fly at an extraordinarily large distance from a space telescope, upping the contrast from about 10^6 to 10^10, making planets 10,000 times as faint visible. Earth-like planets in the habitable zones of stars, here we come! Coming, NASA-funding and prioritization dependent, to either the 2030s or, potentially, WFIRST in the 2020s if we get lucky!
The XKCD version of Free Speech. Image credit: xkcd/Randall Munro, from https://xkcd.com/1357/.
From Denier on free speech: “One of the most contentious speakers on the college circuit right now is Milo Yiannopoulos. For those unfamiliar, Milo is a conservative, white gay male who exclusively dates black guys. His lectures are often anti-Feminist, anti-Safe Space, anti-Identity Politics, and religiously bigoted against followers of Islam.
Milo is not Fascist. He’s not a Nazi. He’s not Alt-Right. He’s not racist. Milo is not a White Nationalist.
https://www.youtube.com/watch?v=ywmd8kR-AmI
Wherever Milo Yiannopoulos speaks, protesters come out in force to try and shut down his lectures. They carry signs and chant various accusations of Fascism along with all of the above. These charges are directed not only at Milo but at anyone going to see Milo.”
The last time you brought up free speech issues and the first amendment (no idea why it’s being brought up here, but whatever), I cautioned you against strawmanning my position and encouraged you to steelman me instead, or at least take what I say at face value. But we’re back to strawmanning, I see.
You are welcome to tell me what you think Milo is or isn’t, but I am not so old that I don’t remember being the ages of 10-13. Where kids first became mean, violent and cruel to one another not to sate their own personal needs (money, candy, the thrill of violence, etc.), but to gain social status instead. I don’t care why Milo does what he does or says what he says; what I see is someone who’s a minority in one way (he’s gay) bully and beat down people — in a public forum — who are minorities in ways he is not. Who are not part of his in-group. He bullies trans people. He bullies muslims. He bullies women. He bullies poor people. And he does it knowing full well that this is his ticket to (partial) acceptance and (loud) adulation within his in-group. Which includes all of the people in the “Milo is not…” groups you list above.
I disagree with Milo in almost everything he’s ever said. I support not inviting him to your campus. I support protesting his appearance. You know, exercising your right to free speech. But I don’t condone the violence in the protests against him. I condemn the actions of the black bloc protesters, as do most people across the political and ideological spectrum. I also don’t conflate “liberals” or “progressives” with a violent minority, just as I don’t conflate “muslims” with the radical islamic terrorists or “actual Nazis like Steve Bannon” with everyone who voted for Donald Trump. I hope you can stop conflating an article that contends, “scientists should adhere to this simple code of ethics in their scientific pursuits and their presentation of science to the public” with a loss of your first amendment rights to act as a private citizen.
But I think your real point comes a few comments later: “The idea Ethan keeps coming back to lately is how to oppress society.”
Society is doing a great job of oppressing a large number of its members. That is an injustice that I see that I believe needs to be righted. So let me ask you what you see as positive ways forward on that front, since elevating those marginalized but valuable voices equals oppression to you. How do we ensure that racial profiling stops? How do we protect the rights of women to control their own bodies: specifically for contraception and access to abortion services? How do we protect rape victims from being further victimized by the legal process? I am starting to think that you and I have very different views on what a “right” is, and that may be the root of where we differ on oppression as well. There is room to argue about that, I suppose, but I think it goes back to something that Donald Trump said in his inauguration speech.
“הִנֵּה מַה-טּוֹב, וּמַה-נָּעִים– שֶׁבֶת אַחִים גַּם-יָחַד.”
Do you recognize that? It’s Psalm 133, my favorite of all the Psalms. (Trump read a translation of it at the inauguration.) Literally, it means “how good and how blessed it is when brothers can live together as one.” I think if you interpret brothers as “people like me” or “my actual brothers” or “the people on my side but not the ones not on my side,” you miss the meaning of “together as one.” We are all children of planet Earth, and I want to see a better planet and a better future for us all. For. Us. All. That is what I’m working to build.
Pan-STARRS1 Observatory atop Haleakala Maui at sunset. Image credit: Rob Ratkowski.
From Wow on collecting every photon: “But not even the best black coating can capture every photon.
Not that every one is required.”
There is a difference between collecting and utilizing. It’s worth remembering that telescopes have not increased all that much in size over the past 100 years. The telescope that Hubble used to discover the expanding Universe — the 100 inch (2.5m) Hooker telescope — is larger than the Hubble Space Telescope’s primary mirror. It was commissioned in 1917. One twice the diameter (the Hale telescope) was commissioned in 1948, and today’s record holders are about twice that diameter still. But the big improvements are in CCDs and cameras. Instead of collecting between 0.1% and 1% of the light, which is what old photographic plates did, we can now use the technique of photomultiplication — where photons strike a surface and an electron gets kicked or excited, creating a cascade and an unmistakable electric current — to efficiently use about 20% of the incident light.
But there is still noise, and that makes the signal hard to pull out of the noise. Once you know where and how something exists, you can go back and clearly pull out a marginally statistically significant signal that would have been ambiguous previously. After the 2011/2012 discovery of the Higgs, they were able to go back to 1988 Fermilab data and identify the first Higgs event; going back through telescope data is a similar process. As time progresses, materials science improves and gets applied to camera technology, we hope to come ever closer to the 100% goal. But noise will always be present.
Light coming from the surface of a neutron star can be polarized by the strong magnetic field it passes through, thanks to the phenomenon of vacuum birefringence. Detectors here on Earth can measure the effective rotation of the polarized light. Image credit: ESO/L. Calçada.
From Anonymous Coward (and echoed by Sinisa Lazarek) on the weird vacuum birefringence effect: “By the way, does the very powerful magnetic field actually change the polarization of the light from the neutron star? As the abstract indicates the emission of light from the neutron star is thermal and thus it should be emitting light at all wavelengths and polarizations. Does the magnetic field actually change the polarization of the light as it leaves the star, or does it have an effective polarization-dependent refractive index, the way a birefringent crystal like calcite does? The article seems to indicate the former, but I’m not sure this is true.”
There is another, older effect which we see all the time: Faraday rotation, which explains how magnetic fields in a medium cause the polarization of light to rotate in a particular fashion. You can measure galactic magnetic fields this way by looking up, away from the galaxy, then moving down, down, down, into the galactic plane, and then out again, and looking at how the polarization of light changes. But this only happens in a dielectric medium, and tells you the combined properties of the magnetic field and of the free (ionized) electron content, which are primarily responsible for the Faraday rotation itself.
But this effect, of vacuum birefringence, is non-classical and purely quantum in nature. It is a much more subtle effect that is similar, but occurs in empty space itself. Yes, the magnetic field actually changes the polarization of light, and it is wavelength dependent. Were these X-rays instead of visible light, the polarization would be ~100% instead of ~15%. It’s an incredible confirmation of this quantum prediction.
The two-toned Iapetus is the strangest known moon in all the Solar System. Image credit: NASA / JPL-Caltech / Space Science Institute / Cassini.
And finally, from Sinisa Lazarek on Iapetus: “The first thought that came to mind when I saw the first image is: Rolling stone gathers no moss”
That’s actually quite a profound thought, and speaks to the point that Iapetus is tidally locked. If Earth orbited Saturn at the distance of Iapetus, it would be locked, too. This is very meaningful when you consider potentially habitable planets orbiting M-class stars; they’re all locked as well. The timescale to locking is very short for these worlds: 10^5 to 10^7 years, while our Solar System is billions of years old. If Iapetus weren’t locked, it would be more uniformly covered in Phoebe’s soot, except for at the poles. As it stands, you can conclude quite clearly that this planet isn’t rolling, and it’s a demonstration of the incredible power of tides.
Thanks for a great and thoughtful week, and looking forward to the next one!
from ScienceBlogs http://ift.tt/2lcvbr1
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