Moon, Mars, Saturn morning of March 1

In the predawn sky tomorrow – March 1, 2016 – you can use the moon to find the planets Mars and Saturn, plus the constellation Scorpius’ brightest star Antares.

There is a surefire way to distinguish the two planets before sunrise on the first day of March. The lit side of the waning moon points toward Saturn and the dark side in the direction of Mars.

Note the difference in color between these two worlds. Saturn appears golden whereas Mars exhibits a ruddy hue. If you have difficulty discerning color with the eye alone, try your luck with binoculars, if you have them.

Like Mars, the star Antares looks reddish. In fact, the name Antares means like Ares in the respect that Mars and its namesake star appear similar in color. Yet, planets tend to shine with a steadier light than do the twinkling stars.

So put this maxim to the test. See if Antares’ sparkling betrays it as a star.

Use the moon to find the planets Mars and Saturn, and the star Antares in late February and early March. Mars will eventually catch up with Saturn, to stage a conjunction of these two words on August 25, 2016. The green line depicts the ecliptic – the sun’s pathin front of the constellations of the Zodiac.

If you live south of the equator, or in the Southern Hemisphere, be mindful that the moon, Mars, Saturn and Antares will be shining quite high in your predawn/dawn sky. Stars sparkle less when high overhead than when closer to the horizon, so Antares may not shimmer to the degree that it does at more northerly latitudes.

No matter where you reside worldwide, however, let the moon be your guide to the planets Mars and Saturn, plus the red supergiant star Antares, on the morning of March 1.

from EarthSky http://ift.tt/1KX1Zjw

In the predawn sky tomorrow – March 1, 2016 – you can use the moon to find the planets Mars and Saturn, plus the constellation Scorpius’ brightest star Antares.

There is a surefire way to distinguish the two planets before sunrise on the first day of March. The lit side of the waning moon points toward Saturn and the dark side in the direction of Mars.

Note the difference in color between these two worlds. Saturn appears golden whereas Mars exhibits a ruddy hue. If you have difficulty discerning color with the eye alone, try your luck with binoculars, if you have them.

Like Mars, the star Antares looks reddish. In fact, the name Antares means like Ares in the respect that Mars and its namesake star appear similar in color. Yet, planets tend to shine with a steadier light than do the twinkling stars.

So put this maxim to the test. See if Antares’ sparkling betrays it as a star.

Use the moon to find the planets Mars and Saturn, and the star Antares in late February and early March. Mars will eventually catch up with Saturn, to stage a conjunction of these two words on August 25, 2016. The green line depicts the ecliptic – the sun’s pathin front of the constellations of the Zodiac.

If you live south of the equator, or in the Southern Hemisphere, be mindful that the moon, Mars, Saturn and Antares will be shining quite high in your predawn/dawn sky. Stars sparkle less when high overhead than when closer to the horizon, so Antares may not shimmer to the degree that it does at more northerly latitudes.

No matter where you reside worldwide, however, let the moon be your guide to the planets Mars and Saturn, plus the red supergiant star Antares, on the morning of March 1.

from EarthSky http://ift.tt/1KX1Zjw

Dodo redemption [Life Lines]

Image of dodo bird skeleton and model By BazzaDaRambler – Oxford University Museum of Natural History … dodo – dead apparently.Uploaded by FunkMonk, CC BY 2.0, http://ift.tt/1na2jzM

 

Using computed tomography (CT) scans of an intact skull, researchers have discovered that extinct dodo birds (Raphus cucullatus), despite having a rather silly name, were actually pretty smart. Well, as smart as a pigeon at least, and pigeons are pretty smart. Dodos likely also had a good sense of smell based on measurements of the olfactory portion of the skull. This sense probably came in handy when hunting for food as these were flightless birds.

Researcher Eugenia Gold of Stony Brook University commented in Live Science that the brain was an appropriate size for their body, neither too large or small. In fact, the ratio of the brain to body size was similar to a modern day pigeon.

Source:

Live Science

from ScienceBlogs http://ift.tt/1KWGfUQ

Image of dodo bird skeleton and model By BazzaDaRambler – Oxford University Museum of Natural History … dodo – dead apparently.Uploaded by FunkMonk, CC BY 2.0, http://ift.tt/1na2jzM

 

Using computed tomography (CT) scans of an intact skull, researchers have discovered that extinct dodo birds (Raphus cucullatus), despite having a rather silly name, were actually pretty smart. Well, as smart as a pigeon at least, and pigeons are pretty smart. Dodos likely also had a good sense of smell based on measurements of the olfactory portion of the skull. This sense probably came in handy when hunting for food as these were flightless birds.

Researcher Eugenia Gold of Stony Brook University commented in Live Science that the brain was an appropriate size for their body, neither too large or small. In fact, the ratio of the brain to body size was similar to a modern day pigeon.

Source:

Live Science

from ScienceBlogs http://ift.tt/1KWGfUQ

Exercise grows bigger fish [Life Lines]

Image of gilthead sea bream By Roberto Pillon – http://ift.tt/1Rec4VO, CC BY 3.0, http://ift.tt/21uxPeI

A new study published in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology explored the effects of exercise on growth and hormone regulation in gilthead sea bream (Sparus aurata). The main hormones that regulate growth are, perhaps not surprisingly, growth hormone and insulin-like growth factor. Researchers discovered young gilthead seam bream that underwent sustained moderate exercise for 5 weeks gained more weight than fish that were not exercised. The exercised fish also had higher levels of the hormone insulin-like growth factor in their blood along with higher levels of a hormone associated with increased protein synthesis in their muscles (i.e. the production of new muscle cells). This is interesting as plasma levels of growth hormone actually decreased with exercise.

Aside from understanding the effects of exercise on the growth and development of fish, this research has important implications for developing or improving the sustainability of aquaculture.

Source:

EJ Vélez, S Azizi, A Millán-Cubillo, J Fernández-Borràs, J Blasco, SJ Chan, JA Calduch-Giner, J Pérez-Sánchez, I Navarro, E Capilla, J Gutiérrez. Effects of sustained exercise on GH-IGFs axis in gilthead sea bream (Sparus aurata). American Journal of Physiology – Regulatory, Integrative and Comparative Physiology. 310(4): R313-R322, 2016. DOI: 10.1152/ajpregu.00230.2015

from ScienceBlogs http://ift.tt/1RecaNd

Image of gilthead sea bream By Roberto Pillon – http://ift.tt/1Rec4VO, CC BY 3.0, http://ift.tt/21uxPeI

A new study published in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology explored the effects of exercise on growth and hormone regulation in gilthead sea bream (Sparus aurata). The main hormones that regulate growth are, perhaps not surprisingly, growth hormone and insulin-like growth factor. Researchers discovered young gilthead seam bream that underwent sustained moderate exercise for 5 weeks gained more weight than fish that were not exercised. The exercised fish also had higher levels of the hormone insulin-like growth factor in their blood along with higher levels of a hormone associated with increased protein synthesis in their muscles (i.e. the production of new muscle cells). This is interesting as plasma levels of growth hormone actually decreased with exercise.

Aside from understanding the effects of exercise on the growth and development of fish, this research has important implications for developing or improving the sustainability of aquaculture.

Source:

EJ Vélez, S Azizi, A Millán-Cubillo, J Fernández-Borràs, J Blasco, SJ Chan, JA Calduch-Giner, J Pérez-Sánchez, I Navarro, E Capilla, J Gutiérrez. Effects of sustained exercise on GH-IGFs axis in gilthead sea bream (Sparus aurata). American Journal of Physiology – Regulatory, Integrative and Comparative Physiology. 310(4): R313-R322, 2016. DOI: 10.1152/ajpregu.00230.2015

from ScienceBlogs http://ift.tt/1RecaNd

Comments of the Week #100: From wave-particle duality to leap day [Starts With A Bang]

“A great accomplishment shouldn’t be the end of the road, just the starting point for the next leap forward.” -Harvey Mackay

Tomorrow is such a big, rare day that it only comes once every four years (or 4.1237 years, for a little greater precision), yet practically every day offers something new and wonderful here at Starts With A Bang. If you missed anything over the past week, here’s what we’ve taken a peek at:

• Do gravitational waves exhibit wave-particle duality? (for Ask Ethan),
• Astronomers push the limits of Hubble (for Mostly Mute Monday),
• Sorry, but lasers aren’t taking you to Mars in three days,
• How long has the Universe been accelerating?,
• LIGO’s black holes probably did not come from one star, and
• The physics of Leap Day.

We’ve got some fun bonuses, too, like our fifth podcast — on gravitational waves and LIGO — is now online and available for streaming and downloading.

In even more exciting news, tomorrow is leap day, with all the exciting physics associated with that, Wednesday I’ll be live-blogging a public lecture on The Dark Side Of The Universe by Katie Freese,
and then as March goes on, I’ll have an exclusive interview with the Principal Investigator of LIGO, Dave Reitze (so drop me your questions here!), I’ll be giving public talks in Portland, OR and in Memphis, TN at MidSouthCon, and then we have some even bigger events coming up in the spring! But there’s no reason to dawdle any further; there’s some great science to dive into right now on this edition of our Comments Of The Week!

Image credit: NASA.

From Denier on the difference between real and virtual gravitons: “If I am understanding correctly, there is a gravitational pull between any two massive bodies and that gravitational pull is facilitated through VIRTUAL gravitons. The radiation of VIRTUAL gravitons does not consume any energy or mass from either of the massive bodies and so the gravitational field could theoretically persist until the end of time. […] However in the merger of black holes some energy is turned into REAL graviton particles and those should exhibit the particle-wave duality just as REAL photons do. A gravitational wave is to a gravitational field what a burst of light is to a magnetic field. Am I understanding this correctly?”

This is both correct and important, and it applies to all real-and-virtual particles. In quantum field theory, we have the full standard model of elementary particles, and we expect extra particles beyond this as well, including the (spin-2, massless) graviton, which is a boson that mediates the force of gravity, and whatever dark matter is, because it’s not a particle in the standard model.

Image credit: E. Siegel, from his new book, Beyond The Galaxy.

Whenever you have two particles exert a force on one another, that can be modeled as an exchange of virtual particles. Virtual particles are a calculational tool, nothing more, to help us understand how particles interact in quantum field theories. Two masses attract because of an exchange of virtual gravitons; two charged particles attract or repel because of an exchange of virtual photons; a charm quark decays into a down quark and a charged antilepton/neutrino pair because of a virtual W- boson. In none of these instances is there any “real” graviton, photon or W- boson to be detected; they’re calculational tools only.

An artist’s impression of two stars orbiting each other and progressing (from left to right) to merger with resulting gravitational waves. This is the suspected origin of short-period gamma ray bursts. Image credit: NASA/CXC/GSFC/T.Strohmayer.

But in the case of gravitational wave emission, there are real gravitons at play here, just as you can make real photons or real bosons of any other type. The only thing I’d change about your analogy is that I’d say “electromagnetic” field instead of magnetic field; in the case of gravity, the gravitational field plays the role of both electric and magnetic components!

Image credit: LIGO Collaboration.

From Johan on whether we’re fooling ourselves or not with the LIGO results: “Not a scientist and not doubting the LIGO result but how can you be sure that the result i correct unlike the infamous BICEP for example?”

The major ways in which this is different than the BICEP2 results are:

• BICEP2 relied on a foreground subtraction from inferred Planck data that they did not have; LIGO has no such systematic there.
• There are two independent LIGO detectors running simultaneously; they both detected the same signal.
• There are many confounding factors that can cause EM polarization, which BICEP2 observed. For LIGO, there are gravitational waves, and there’s sabotage.

Unless this was an incredible act of sabotage from someone on the inside (and it would have to be from someone on the inside), this is real.

Image credit: ESO/M. Hayes, of a region of the GOODS field imaged by both Hubble and multiple instruments aboard the ESO’s Very Large Telescope.

From Sinisa Lazarek on the GOODS field: “[As respects the last image] you say it’s hubble with EST, yet the source on wiki as well as ESA’s website ( http://ift.tt/21C51xu ) don’t mention HST anywhere in contributing to that photo.”

So above is the image in question, with the caption I used on Forbes. Here is the pure-Hubble component of the GOODS-South field. Before you take a look, make note of the features in the upper-left of the VLT image, above, and now look for those same galaxies — the interacting, nearby pair and the ring-like large spiral nearby — at the lower left-center of the Hubble image below.

Image credit: NASA, ESA, R. Windhorst, S. Cohen, M. Mechtley, and M. Rutkowski (Arizona State University, Tempe), R. O’Connell (University of Virginia), P. McCarthy (Carnegie Observatories), N. Hathi (University of California, Riverside), R. Ryan (University of California, Davis), H. Yan (Ohio State University), and A. Koekemoer (Space Telescope Science Institute).

As you can see, there isn’t 100% overlap, but there is data from both HST and VLT that covers this region of space. So your sources are correct, your assessment of the image is correct, but I think I can say I’m correct, too. Multiple telescopes working together: how beautiful!

Image credit: the DEEP-laser sail concept, via http://ift.tt/1O5y5UR, Copyright © 2016 UCSB Experimental Cosmology Group.

From eric on the deceleration problem: “The obvious solution to the lack of deceleration problem – IF we were seriously intending to use this technology repetitively, for example to set up a Mars-Earth system – would be to use chemical rockets to propel a remote controlled laser facility to Mars or some other destination spot, and then operate the two-laser system in the classic ‘accelerate halfway/flip/decelerate rest of the way’ mode.”

I very much wish that this was a viable solution. Perhaps it is for setting up a short-time-period, relatively short-distance journey, like from Earth to Mars. But how will you get and assemble an array of lasers (and how will you power them?) to either the outer Solar System or to somewhere in interstellar space? You’re essentially talking about doubling the cost of your project for every single destination you want to add. Which I’m not sure is the obvious solution… obviously expensive, perhaps, especially considering we need a ~100 km^2 array of lasers around Earth just for the launch!

Your solution is possible, for sure. But is it plausible? Especially given how difficult it is to maintain the orientation of a sail when you’re firing energy into it, my inclination is to wait and see. Technically possible is a long way from feasible.

Image credit: NASA, Goddard Space Flight Center, of an illustration of the expanding Universe.

From Omega Centauri on detecting the acceleration of the Universe: “I’m betting that if we had been around at half the present age of the universe we would have been able to deduce that while the expansion rate is yet accelerating, simple extrapolation of the expansion rate would indicate it soon will be, and our best fit theories would have told us the story. And with the younger denser universe, with more active star formation, and more very massive stars because the metalicity hadn’t built up as much, we would have had many more observable events with which to deduce the past expansion rate, so we shoulda been able to do OK.”

The hard part about detecting something that’s a sub-dominant effect, particularly if it’s never been a dominant effect, is that you have no motivation to go looking for it when you consider it and don’t see it right away. Take a look at this graph, for example.

Image credit: Quantum Stories, retrieved via http://ift.tt/1e6imWM.

These are the components of energy — radiation, matter and dark energy — that we know to be important in the evolution and history of our Universe. At one time, each of these were dominant: radiation during the first ~10,000 years or so, matter during the next ~9 billion years, and dark energy in all the time since. What if we lived at a redshift of 3, or even of 10, where dark energy was only 3% (or 0.1%) of the Universe’s energy density? Would we have seen it? Would we be able to? When — at what level of non-detection — would we have given up? At what level of precision would we have had to measure to detect it, and how confident could we be of something that’s only just beginning to affect the Universe we observe? Consider this from another point of view.

Image credit: E. Siegel.

How confident are we that we don’t have another, sub-dominant component to our Universe’s energy density that simply hasn’t shown up yet? How do we know there isn’t a darker energy component with w = -4/3 or w = -5/3 or something else more negative than w = -1 that will eventually take over from our currently-understood dark energy?

The answer is that we don’t know, and until (or unless) we find evidence at a certain significance level that something else must be present, we probably won’t look very hard for it.

Image credit: NASA / CXC / M. Weiss.

From SelfAwarePatterns on the black-hole-in-a-single-star theory: “My assumption with the two-black-holes-in-one-star theory was that the star was in the process of complete collapse, causing the GRB, but that, due to its extremely high rotation speed, it had an intermediate stage where two black holes formed in a dumbell configuration, which then proceeded to merge causing the gravitational waves.”

The big problem with that theory, if you want to go that route, is that you need a single star that’s so massive you get a hypernova explosion: a single star that’s over the threshold of about ~130 solar masses or so. You’d need something at least that big in order to get two ~30 solar mass black holes inside, and honestly, you’re probably talking about something much more massive even than that. Now, in this scenario, you get such a rise in temperature that you start producing electron-positron pairs spontaneously out of the radiation inside, which drops the pressure and causes the implosion, resulting in a hypernova and a large, central black hole. You add severe angular momentum to the mix all you want, but either you’re getting:

• all the mass collapsing down into a black hole, or
• a catastrophic explosion that should be easily visible to us with follow-up observations that search for supernovae.

So either we wouldn’t have seen gamma rays (the first option) or we would’ve seen something with follow-up supernova searches.

Image credit: Image credit: NASA, ESA and G. Bacon (STScI), of a binary black hole. Loeb’s idea is that these binary black holes could exist inside a single star.

Those searches turned up nothing. What’s perhaps possible — and this is interesting — is that the Fermi satellite saw absolutely nothing of note, and that it was just a spurious “barely-there” non-detection of absolutely nothing. The fact that ESA’s INTEGRAL observatory didn’t see anything either supports this. Hopefully (and probably) we’ll have more events like this in the near future to look at, and we’ll learn whether gamma rays are produced with black hole-black hole mergers routinely, rarely, or not at all, and this will help shed some light on what actually is going on here!

So thanks for a great week, and remember to take a chance tomorrow.

Image credit: 30 Rock / NBC Studios.

As Leap Day William says, “Remember, real life is for March!”

from ScienceBlogs http://ift.tt/1TggPVa

“A great accomplishment shouldn’t be the end of the road, just the starting point for the next leap forward.” -Harvey Mackay

Tomorrow is such a big, rare day that it only comes once every four years (or 4.1237 years, for a little greater precision), yet practically every day offers something new and wonderful here at Starts With A Bang. If you missed anything over the past week, here’s what we’ve taken a peek at:

• Do gravitational waves exhibit wave-particle duality? (for Ask Ethan),
• Astronomers push the limits of Hubble (for Mostly Mute Monday),
• Sorry, but lasers aren’t taking you to Mars in three days,
• How long has the Universe been accelerating?,
• LIGO’s black holes probably did not come from one star, and
• The physics of Leap Day.

We’ve got some fun bonuses, too, like our fifth podcast — on gravitational waves and LIGO — is now online and available for streaming and downloading.

In even more exciting news, tomorrow is leap day, with all the exciting physics associated with that, Wednesday I’ll be live-blogging a public lecture on The Dark Side Of The Universe by Katie Freese,
and then as March goes on, I’ll have an exclusive interview with the Principal Investigator of LIGO, Dave Reitze (so drop me your questions here!), I’ll be giving public talks in Portland, OR and in Memphis, TN at MidSouthCon, and then we have some even bigger events coming up in the spring! But there’s no reason to dawdle any further; there’s some great science to dive into right now on this edition of our Comments Of The Week!

Image credit: NASA.

From Denier on the difference between real and virtual gravitons: “If I am understanding correctly, there is a gravitational pull between any two massive bodies and that gravitational pull is facilitated through VIRTUAL gravitons. The radiation of VIRTUAL gravitons does not consume any energy or mass from either of the massive bodies and so the gravitational field could theoretically persist until the end of time. […] However in the merger of black holes some energy is turned into REAL graviton particles and those should exhibit the particle-wave duality just as REAL photons do. A gravitational wave is to a gravitational field what a burst of light is to a magnetic field. Am I understanding this correctly?”

This is both correct and important, and it applies to all real-and-virtual particles. In quantum field theory, we have the full standard model of elementary particles, and we expect extra particles beyond this as well, including the (spin-2, massless) graviton, which is a boson that mediates the force of gravity, and whatever dark matter is, because it’s not a particle in the standard model.

Image credit: E. Siegel, from his new book, Beyond The Galaxy.

Whenever you have two particles exert a force on one another, that can be modeled as an exchange of virtual particles. Virtual particles are a calculational tool, nothing more, to help us understand how particles interact in quantum field theories. Two masses attract because of an exchange of virtual gravitons; two charged particles attract or repel because of an exchange of virtual photons; a charm quark decays into a down quark and a charged antilepton/neutrino pair because of a virtual W- boson. In none of these instances is there any “real” graviton, photon or W- boson to be detected; they’re calculational tools only.

An artist’s impression of two stars orbiting each other and progressing (from left to right) to merger with resulting gravitational waves. This is the suspected origin of short-period gamma ray bursts. Image credit: NASA/CXC/GSFC/T.Strohmayer.

But in the case of gravitational wave emission, there are real gravitons at play here, just as you can make real photons or real bosons of any other type. The only thing I’d change about your analogy is that I’d say “electromagnetic” field instead of magnetic field; in the case of gravity, the gravitational field plays the role of both electric and magnetic components!

Image credit: LIGO Collaboration.

From Johan on whether we’re fooling ourselves or not with the LIGO results: “Not a scientist and not doubting the LIGO result but how can you be sure that the result i correct unlike the infamous BICEP for example?”

The major ways in which this is different than the BICEP2 results are:

• BICEP2 relied on a foreground subtraction from inferred Planck data that they did not have; LIGO has no such systematic there.
• There are two independent LIGO detectors running simultaneously; they both detected the same signal.
• There are many confounding factors that can cause EM polarization, which BICEP2 observed. For LIGO, there are gravitational waves, and there’s sabotage.

Unless this was an incredible act of sabotage from someone on the inside (and it would have to be from someone on the inside), this is real.

Image credit: ESO/M. Hayes, of a region of the GOODS field imaged by both Hubble and multiple instruments aboard the ESO’s Very Large Telescope.

From Sinisa Lazarek on the GOODS field: “[As respects the last image] you say it’s hubble with EST, yet the source on wiki as well as ESA’s website ( http://ift.tt/21C51xu ) don’t mention HST anywhere in contributing to that photo.”

So above is the image in question, with the caption I used on Forbes. Here is the pure-Hubble component of the GOODS-South field. Before you take a look, make note of the features in the upper-left of the VLT image, above, and now look for those same galaxies — the interacting, nearby pair and the ring-like large spiral nearby — at the lower left-center of the Hubble image below.

Image credit: NASA, ESA, R. Windhorst, S. Cohen, M. Mechtley, and M. Rutkowski (Arizona State University, Tempe), R. O’Connell (University of Virginia), P. McCarthy (Carnegie Observatories), N. Hathi (University of California, Riverside), R. Ryan (University of California, Davis), H. Yan (Ohio State University), and A. Koekemoer (Space Telescope Science Institute).

As you can see, there isn’t 100% overlap, but there is data from both HST and VLT that covers this region of space. So your sources are correct, your assessment of the image is correct, but I think I can say I’m correct, too. Multiple telescopes working together: how beautiful!

Image credit: the DEEP-laser sail concept, via http://ift.tt/1O5y5UR, Copyright © 2016 UCSB Experimental Cosmology Group.

From eric on the deceleration problem: “The obvious solution to the lack of deceleration problem – IF we were seriously intending to use this technology repetitively, for example to set up a Mars-Earth system – would be to use chemical rockets to propel a remote controlled laser facility to Mars or some other destination spot, and then operate the two-laser system in the classic ‘accelerate halfway/flip/decelerate rest of the way’ mode.”

I very much wish that this was a viable solution. Perhaps it is for setting up a short-time-period, relatively short-distance journey, like from Earth to Mars. But how will you get and assemble an array of lasers (and how will you power them?) to either the outer Solar System or to somewhere in interstellar space? You’re essentially talking about doubling the cost of your project for every single destination you want to add. Which I’m not sure is the obvious solution… obviously expensive, perhaps, especially considering we need a ~100 km^2 array of lasers around Earth just for the launch!

Your solution is possible, for sure. But is it plausible? Especially given how difficult it is to maintain the orientation of a sail when you’re firing energy into it, my inclination is to wait and see. Technically possible is a long way from feasible.

Image credit: NASA, Goddard Space Flight Center, of an illustration of the expanding Universe.

From Omega Centauri on detecting the acceleration of the Universe: “I’m betting that if we had been around at half the present age of the universe we would have been able to deduce that while the expansion rate is yet accelerating, simple extrapolation of the expansion rate would indicate it soon will be, and our best fit theories would have told us the story. And with the younger denser universe, with more active star formation, and more very massive stars because the metalicity hadn’t built up as much, we would have had many more observable events with which to deduce the past expansion rate, so we shoulda been able to do OK.”

The hard part about detecting something that’s a sub-dominant effect, particularly if it’s never been a dominant effect, is that you have no motivation to go looking for it when you consider it and don’t see it right away. Take a look at this graph, for example.

Image credit: Quantum Stories, retrieved via http://ift.tt/1e6imWM.

These are the components of energy — radiation, matter and dark energy — that we know to be important in the evolution and history of our Universe. At one time, each of these were dominant: radiation during the first ~10,000 years or so, matter during the next ~9 billion years, and dark energy in all the time since. What if we lived at a redshift of 3, or even of 10, where dark energy was only 3% (or 0.1%) of the Universe’s energy density? Would we have seen it? Would we be able to? When — at what level of non-detection — would we have given up? At what level of precision would we have had to measure to detect it, and how confident could we be of something that’s only just beginning to affect the Universe we observe? Consider this from another point of view.

Image credit: E. Siegel.

How confident are we that we don’t have another, sub-dominant component to our Universe’s energy density that simply hasn’t shown up yet? How do we know there isn’t a darker energy component with w = -4/3 or w = -5/3 or something else more negative than w = -1 that will eventually take over from our currently-understood dark energy?

The answer is that we don’t know, and until (or unless) we find evidence at a certain significance level that something else must be present, we probably won’t look very hard for it.

Image credit: NASA / CXC / M. Weiss.

From SelfAwarePatterns on the black-hole-in-a-single-star theory: “My assumption with the two-black-holes-in-one-star theory was that the star was in the process of complete collapse, causing the GRB, but that, due to its extremely high rotation speed, it had an intermediate stage where two black holes formed in a dumbell configuration, which then proceeded to merge causing the gravitational waves.”

The big problem with that theory, if you want to go that route, is that you need a single star that’s so massive you get a hypernova explosion: a single star that’s over the threshold of about ~130 solar masses or so. You’d need something at least that big in order to get two ~30 solar mass black holes inside, and honestly, you’re probably talking about something much more massive even than that. Now, in this scenario, you get such a rise in temperature that you start producing electron-positron pairs spontaneously out of the radiation inside, which drops the pressure and causes the implosion, resulting in a hypernova and a large, central black hole. You add severe angular momentum to the mix all you want, but either you’re getting:

• all the mass collapsing down into a black hole, or
• a catastrophic explosion that should be easily visible to us with follow-up observations that search for supernovae.

So either we wouldn’t have seen gamma rays (the first option) or we would’ve seen something with follow-up supernova searches.

Image credit: Image credit: NASA, ESA and G. Bacon (STScI), of a binary black hole. Loeb’s idea is that these binary black holes could exist inside a single star.

Those searches turned up nothing. What’s perhaps possible — and this is interesting — is that the Fermi satellite saw absolutely nothing of note, and that it was just a spurious “barely-there” non-detection of absolutely nothing. The fact that ESA’s INTEGRAL observatory didn’t see anything either supports this. Hopefully (and probably) we’ll have more events like this in the near future to look at, and we’ll learn whether gamma rays are produced with black hole-black hole mergers routinely, rarely, or not at all, and this will help shed some light on what actually is going on here!

So thanks for a great week, and remember to take a chance tomorrow.

Image credit: 30 Rock / NBC Studios.

As Leap Day William says, “Remember, real life is for March!”

from ScienceBlogs http://ift.tt/1TggPVa

DNA: it’s in your blood [Discovering Biology in a Digital World]

Did you know small fragments of DNA are circulating in your blood stream?

These short pieces of DNA are left behind after cells self-destruct. This self-destruction, or apoptosis, is a normal process. In the case of fetal development, certain cells in our hands die, leaving behind individual fingers. Immune system cells leave traces of DNA behind after they’ve tackled invading microbes. DNA can also appear in the blood when people have cancer.

I had the good fortune, last Monday, to hear Matthew Snyder describe this cell-free DNA in a fascinating talk and learn why DNA in the blood can be a useful thing. It turns out that cell free DNA is a potentially useful tool for evaluating fetal health, guiding cancer treatment, and monitoring organ transplants.

According to Snyder, the use of cell free DNA for diagnosing trisomy 21, is one of the fastest growing molecular tests in the history of medicine.  Some of the rapid adoption of this test is driven by pregnant women who request it.

People are interested in the prospect of using cell free DNA for other kinds of tests as well. It could be used as a biomarker to indicate the presence of cancer, or perhaps other kinds of disease.

Snyder’s research involves sequencing this cell free DNA and trying to figure out where it came from. You might think that the DNA in one person would be pretty much the same from one cell to another. And with a few exceptions, like B and T cells, that’s the case. But the DNA fragments that float around in our blood aren’t random. We can only find DNA fragments in our blood because they were hidden from hungry nucleases during the self-destruction process. Normally, those enzymes would have chopped that DNA into tiny bits.

Cell free DNA exists because the proteins that transcribe DNA and the histone proteins that package it into nucleosomes also protect DNA from being digested.

Proteins protecting DNA from digestion.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The really interesting thing, in terms of cell free DNA, is that nucleosomes and transcription factors sit on different regions of DNA in different cells.  Since different bits of DNA get protected in different cells, we can sequence the cell free bits of DNA figure out where it came from.  That information can tell us about a type of cancer or help us evaluate the health of multiple cell types.

This structure has been colored by charge. The negatively charged DNA (red) is wrapped about the positively charged histone proteins. Blue represents a positive charge.

 

 

 

 

 

 

 

 

 

 

 

 

 

Reference:

Snyder MW, Kircher M, Hill AJ, Daza RM, Shendure J. Cell-free DNA Comprises an In Vivo Nucleosome Footprint that Informs Its Tissues-Of-Origin. Cell. 2016 Jan 14;164(1-2):57-68. doi: 10.1016/j.cell.2015.11.050.

from ScienceBlogs http://ift.tt/1TLq7YN

Did you know small fragments of DNA are circulating in your blood stream?

These short pieces of DNA are left behind after cells self-destruct. This self-destruction, or apoptosis, is a normal process. In the case of fetal development, certain cells in our hands die, leaving behind individual fingers. Immune system cells leave traces of DNA behind after they’ve tackled invading microbes. DNA can also appear in the blood when people have cancer.

I had the good fortune, last Monday, to hear Matthew Snyder describe this cell-free DNA in a fascinating talk and learn why DNA in the blood can be a useful thing. It turns out that cell free DNA is a potentially useful tool for evaluating fetal health, guiding cancer treatment, and monitoring organ transplants.

According to Snyder, the use of cell free DNA for diagnosing trisomy 21, is one of the fastest growing molecular tests in the history of medicine.  Some of the rapid adoption of this test is driven by pregnant women who request it.

People are interested in the prospect of using cell free DNA for other kinds of tests as well. It could be used as a biomarker to indicate the presence of cancer, or perhaps other kinds of disease.

Snyder’s research involves sequencing this cell free DNA and trying to figure out where it came from. You might think that the DNA in one person would be pretty much the same from one cell to another. And with a few exceptions, like B and T cells, that’s the case. But the DNA fragments that float around in our blood aren’t random. We can only find DNA fragments in our blood because they were hidden from hungry nucleases during the self-destruction process. Normally, those enzymes would have chopped that DNA into tiny bits.

Cell free DNA exists because the proteins that transcribe DNA and the histone proteins that package it into nucleosomes also protect DNA from being digested.

Proteins protecting DNA from digestion.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The really interesting thing, in terms of cell free DNA, is that nucleosomes and transcription factors sit on different regions of DNA in different cells.  Since different bits of DNA get protected in different cells, we can sequence the cell free bits of DNA figure out where it came from.  That information can tell us about a type of cancer or help us evaluate the health of multiple cell types.

This structure has been colored by charge. The negatively charged DNA (red) is wrapped about the positively charged histone proteins. Blue represents a positive charge.

 

 

 

 

 

 

 

 

 

 

 

 

 

Reference:

Snyder MW, Kircher M, Hill AJ, Daza RM, Shendure J. Cell-free DNA Comprises an In Vivo Nucleosome Footprint that Informs Its Tissues-Of-Origin. Cell. 2016 Jan 14;164(1-2):57-68. doi: 10.1016/j.cell.2015.11.050.

from ScienceBlogs http://ift.tt/1TLq7YN

How embarrassing for Velikovsky [Stoat]

Before laying into Hansen’s latest, I feel a need to re-establish my taking-the-piss-out-of-the-wackos credentials. And here is a perfect opportunity:

Even Sou struggles to cover this; I think we need Inferno. Or RS. Amusingly, not one of the comments at WUWT so far has dared to mention the V-word.

from ScienceBlogs http://ift.tt/1n8C8JL

Before laying into Hansen’s latest, I feel a need to re-establish my taking-the-piss-out-of-the-wackos credentials. And here is a perfect opportunity:

Even Sou struggles to cover this; I think we need Inferno. Or RS. Amusingly, not one of the comments at WUWT so far has dared to mention the V-word.

from ScienceBlogs http://ift.tt/1n8C8JL

Whom Should I Vote For: Clinton or Sanders? [Greg Laden's Blog]

You may be asking yourself the same question, especially if, like me, you vote on Tuesday, March 1st.

For some of us, a related question is which of the two is likely to win the nomination.

If one of the two is highly likely to win the nomination, then it may be smart to vote for that candidate in order to add to the momentum effect and, frankly, to end the internecine fighting and eating of young within the party sooner. If, however, one of the two is only somewhat likely to win the nomination, and your preference is for the one slightly more likely to lose, then you better vote for the projected loser so they become the winner!

National polls of who is ahead have been unreliable, and also, relying on those polls obviates the democratic process, so they should be considered but not used to drive one’s choice. However, a number of primaries have already happened, so there is some information from those contests to help estimate what might happen in the future. On the other hand, there have been only a few primaries so far. Making a choice based wholly or in part on who is likely to win is better left until after Super Tuesday, when there will be more data. But, circling back to the original question, that does not help those of us voting in two days, does it?

Let’s look at the primaries so far.

Overall, Sanders has done better than polls might have suggested weeks before the primaries started. This tell us that his insurgency is valid and should be paid attention to.

There has been a lot of talk about which candidate is electable vs. not, and about theoretical match-ups with Trump or other GOP candidates. If you look at ALL the match-ups, instead one cherry picked match-up the supporter of one or the other candidate might pick, both candidates do OK against the GOP. Also, such early theoretical match-ups are probably very unreliable. So, best to ignore them.

Iowa told us that the two candidates are roughly matched.

New Hampshire confirmed that the two candidates are roughly matched, given that Sanders has a partial “favorite son” effect going in the Granite State.

Nevada confirmed, again, that the two candidates are roughly matched, because the difference wasn’t great between the two.

So far, given those three races, in combination with exit polls, we can surmise that among White voters, the two candidates are roughly matched, but with Sanders doing better with younger voters, and Clinton doing better with older voters.

The good news for Sanders about younger voters is that he is bringing people into the process, which means more voters, and that is good. The bad news is two part: 1) Younger voters are unreliable. They were supposed to elect Kerry, but never showed up, for example; and 2) Some (a small number, I hope) of Sanders’ younger voters claim that they will abandon the race, or the Democrats, if their candidate does not win, write in Sanders, vote for Trump, or some other idiotic thing. So, if Clinton ends up being the nominee, thanks Bernie, but really, no thanks.

Then came South Carolina. Before South Carolina, we knew that there were two likely outcomes down the road starting with this first southern state. One is that expectations surrounding Clinton’s campaign would be confirmed, and she would do about 70-30 among African American voters, which in the end would give her a likely win in the primary. The other possibility is that Sanders would close this ethnic gap, which, given his support among men and white voters, could allow him to win the primary.

What happened in South Carolina is that Clinton did way better than even those optimistic predictions suggested. This is not good for Sanders.

Some have claimed that South Carolina was an aberration. But, that claim is being made only by Sanders supporters, and only after the fact. Also, the claim is largely bogus because it suggests that somehow Democratic and especially African American Democratic voters are somehow conservative southern yahoos, and that is why they voted so heavily in favor of Clinton. But really, there is no reason to suggest that Democratic African American voters aren’t reasonably well represented by South Carolina.

In addition to that, polling for other southern states conforms pretty closely to expectations based on the actual results for South Carolina.

I developed an ethnic-based model for the Democratic primary (see this for an earlier version). The idea of the model is simple. Most of the variation we will ultimately observe among the states in voting patterns for the two candidates will be explained by the ethnic mix in each state. This is certainly an oversimplification, but has a good chance of working given that before breaking out voters by ethnicity, we are subsetting them by party affiliation. So this is not how White, Black and Hispanic people will vote across the states, but rather, how White, Black and Hispanic Democrats will vote across the state. I’m pretty confident that this is a useful model.

My model has two versions (chosen by me, there could be many other versions), one giving Sanders’ strategy a nod by having him do 10% better among white voters, but only 60-40 among non-white voters. The Clinton-favored strategy gives Clinton 50-50 among white voters, and a strong advantage among African American voters, based on South Carolina’s results and polling, of 86-14%. Clinton also has a small advantage among Hispanic voters (based mainly on polls) with a 57:43% mix.

These are the numbers I’ve settled on today, after South Carolina. But, I will adjust these numbers after Super Tuesday, and at that point, I’ll have some real confidence in the model. But, at the moment, the model seems to be potentially useful, and I’ll be happy to tell you why.

First, let us dispose of some of the circular logic. Given both polls and South Carolina’s results, the model, based partly on South Carolina, predicts South Carolina pretty well using the Clinton-favored version (not the Sanders-favored version), with a predicted cf. actual outcome of 34:19% cf 39:14% This is obviously not an independent prediction, but rather a calibration. The Sanders-favored model predicts an even outcome of 27:26%.

The following table shows the likely results for the Clinton-favored and Sanders-favored model in each state having a primary on Tuesday.

The two columns on the right are estimates from polling where available. This is highly variable in quality and should be used cautiously. I highlighted the Clinton- or Sanders-favored model that most closely matches the polling. The matches are generally very close. This strongly suggests that the Clinton-favored version of the model essentially works, even given the limited information, and simplicity of the model.

Please note that in both the Clinton- and Sanders-favored model, Clinton wins the day on Tuesday, but only barely for the Sanders-favored model (note that territories are not considered here).

I applied the same model over the entire primary season (states only) to produce two graphs, shown below.

The Clinton-favored model has Clinton pulling ahead in uncommitted delegate (I ignore Super Delegates, who are not committed) on Tuesday, then widens her lead over time, winning handily. The Sanders-favored model projects a horserace, where the two candidates are ridiculously close for the entire election.

So, who am I going to voter for?

I like both candidates. The current model suggests I should vote for Clinton because she is going to pull ahead, and it is better to vote for the likely winner, since I like them both, so that person gets more momentum (a tiny fraction of momentum, given one vote, but still…). On the other hand, a Sanders insurgency would be revolutionary and change the world in interesting ways, and for that to happen, Sanders needs as many votes on Tuesday as possible.

It is quite possible, then, that I’ll vote for Sanders, then work hard for Hillary if Super Tuesday confirms the Clinton favored model. That is how I am leaning now, having made that decision while typing the first few words of this very paragraph.

Or I could change my mind.

Either way, I want to see people stop being so mean to the candidate they are not supporting. That is only going to hurt, and be a regretful decision, if your candidate is not the chosen one. Also, you are annoying the heck out of everyone else. So just stop, OK?

from ScienceBlogs http://ift.tt/1n8C64w

You may be asking yourself the same question, especially if, like me, you vote on Tuesday, March 1st.

For some of us, a related question is which of the two is likely to win the nomination.

If one of the two is highly likely to win the nomination, then it may be smart to vote for that candidate in order to add to the momentum effect and, frankly, to end the internecine fighting and eating of young within the party sooner. If, however, one of the two is only somewhat likely to win the nomination, and your preference is for the one slightly more likely to lose, then you better vote for the projected loser so they become the winner!

National polls of who is ahead have been unreliable, and also, relying on those polls obviates the democratic process, so they should be considered but not used to drive one’s choice. However, a number of primaries have already happened, so there is some information from those contests to help estimate what might happen in the future. On the other hand, there have been only a few primaries so far. Making a choice based wholly or in part on who is likely to win is better left until after Super Tuesday, when there will be more data. But, circling back to the original question, that does not help those of us voting in two days, does it?

Let’s look at the primaries so far.

Overall, Sanders has done better than polls might have suggested weeks before the primaries started. This tell us that his insurgency is valid and should be paid attention to.

There has been a lot of talk about which candidate is electable vs. not, and about theoretical match-ups with Trump or other GOP candidates. If you look at ALL the match-ups, instead one cherry picked match-up the supporter of one or the other candidate might pick, both candidates do OK against the GOP. Also, such early theoretical match-ups are probably very unreliable. So, best to ignore them.

Iowa told us that the two candidates are roughly matched.

New Hampshire confirmed that the two candidates are roughly matched, given that Sanders has a partial “favorite son” effect going in the Granite State.

Nevada confirmed, again, that the two candidates are roughly matched, because the difference wasn’t great between the two.

So far, given those three races, in combination with exit polls, we can surmise that among White voters, the two candidates are roughly matched, but with Sanders doing better with younger voters, and Clinton doing better with older voters.

The good news for Sanders about younger voters is that he is bringing people into the process, which means more voters, and that is good. The bad news is two part: 1) Younger voters are unreliable. They were supposed to elect Kerry, but never showed up, for example; and 2) Some (a small number, I hope) of Sanders’ younger voters claim that they will abandon the race, or the Democrats, if their candidate does not win, write in Sanders, vote for Trump, or some other idiotic thing. So, if Clinton ends up being the nominee, thanks Bernie, but really, no thanks.

Then came South Carolina. Before South Carolina, we knew that there were two likely outcomes down the road starting with this first southern state. One is that expectations surrounding Clinton’s campaign would be confirmed, and she would do about 70-30 among African American voters, which in the end would give her a likely win in the primary. The other possibility is that Sanders would close this ethnic gap, which, given his support among men and white voters, could allow him to win the primary.

What happened in South Carolina is that Clinton did way better than even those optimistic predictions suggested. This is not good for Sanders.

Some have claimed that South Carolina was an aberration. But, that claim is being made only by Sanders supporters, and only after the fact. Also, the claim is largely bogus because it suggests that somehow Democratic and especially African American Democratic voters are somehow conservative southern yahoos, and that is why they voted so heavily in favor of Clinton. But really, there is no reason to suggest that Democratic African American voters aren’t reasonably well represented by South Carolina.

In addition to that, polling for other southern states conforms pretty closely to expectations based on the actual results for South Carolina.

I developed an ethnic-based model for the Democratic primary (see this for an earlier version). The idea of the model is simple. Most of the variation we will ultimately observe among the states in voting patterns for the two candidates will be explained by the ethnic mix in each state. This is certainly an oversimplification, but has a good chance of working given that before breaking out voters by ethnicity, we are subsetting them by party affiliation. So this is not how White, Black and Hispanic people will vote across the states, but rather, how White, Black and Hispanic Democrats will vote across the state. I’m pretty confident that this is a useful model.

My model has two versions (chosen by me, there could be many other versions), one giving Sanders’ strategy a nod by having him do 10% better among white voters, but only 60-40 among non-white voters. The Clinton-favored strategy gives Clinton 50-50 among white voters, and a strong advantage among African American voters, based on South Carolina’s results and polling, of 86-14%. Clinton also has a small advantage among Hispanic voters (based mainly on polls) with a 57:43% mix.

These are the numbers I’ve settled on today, after South Carolina. But, I will adjust these numbers after Super Tuesday, and at that point, I’ll have some real confidence in the model. But, at the moment, the model seems to be potentially useful, and I’ll be happy to tell you why.

First, let us dispose of some of the circular logic. Given both polls and South Carolina’s results, the model, based partly on South Carolina, predicts South Carolina pretty well using the Clinton-favored version (not the Sanders-favored version), with a predicted cf. actual outcome of 34:19% cf 39:14% This is obviously not an independent prediction, but rather a calibration. The Sanders-favored model predicts an even outcome of 27:26%.

The following table shows the likely results for the Clinton-favored and Sanders-favored model in each state having a primary on Tuesday.

The two columns on the right are estimates from polling where available. This is highly variable in quality and should be used cautiously. I highlighted the Clinton- or Sanders-favored model that most closely matches the polling. The matches are generally very close. This strongly suggests that the Clinton-favored version of the model essentially works, even given the limited information, and simplicity of the model.

Please note that in both the Clinton- and Sanders-favored model, Clinton wins the day on Tuesday, but only barely for the Sanders-favored model (note that territories are not considered here).

I applied the same model over the entire primary season (states only) to produce two graphs, shown below.

The Clinton-favored model has Clinton pulling ahead in uncommitted delegate (I ignore Super Delegates, who are not committed) on Tuesday, then widens her lead over time, winning handily. The Sanders-favored model projects a horserace, where the two candidates are ridiculously close for the entire election.

So, who am I going to voter for?

I like both candidates. The current model suggests I should vote for Clinton because she is going to pull ahead, and it is better to vote for the likely winner, since I like them both, so that person gets more momentum (a tiny fraction of momentum, given one vote, but still…). On the other hand, a Sanders insurgency would be revolutionary and change the world in interesting ways, and for that to happen, Sanders needs as many votes on Tuesday as possible.

It is quite possible, then, that I’ll vote for Sanders, then work hard for Hillary if Super Tuesday confirms the Clinton favored model. That is how I am leaning now, having made that decision while typing the first few words of this very paragraph.

Or I could change my mind.

Either way, I want to see people stop being so mean to the candidate they are not supporting. That is only going to hurt, and be a regretful decision, if your candidate is not the chosen one. Also, you are annoying the heck out of everyone else. So just stop, OK?

from ScienceBlogs http://ift.tt/1n8C64w