from ScienceBlogs http://ift.tt/1rnnAc0
Did human limbs evolve from shark gills?
Skeleton of an embryonic bamboo shark, viewed from the underside. Gill arch appendages extend from each side of the head. Directly below them are a pair of fins. Image via Andrew Gillis.
In 1878, German anatomist Karl Gegenbaur suggested that paired human limbs – like our hands and feet – evolved from the paired fins of fish, and, before that, from fishes’ gills. But there was no fossil evidence to verify his theory.
New genetic research indicates that Gegenbaur may have been on the right track. A paper published in April, 2016, in the journal Development reports that the Sonic Hedgehog gene – already known to be essential for embryo development in mammals, such as humans, including the formation of limbs – is also responsible for developing appendages called branchial rays in skate embryos.
Skin flaps that protect the gills of cartilaginous fish – sharks, skates, rays – are supported by arch-like cartilage structures. Protruding from these cartilage arches are the branchial rays.
Dr. Andrew Gillis, at the University of Cambridge and also affiliated with the Marine Biological Laboratory, was lead researcher in this study. He said in a statement:
Gegenbaur looked at the way that these branchial rays connect to the gill arches and noticed that it looks very similar to the way that the fin and limb skeleton articulates with the shoulder.
The Sonic Hedgehog gene, named by a researcher at Harvard Medical School after the Sonic the Hedgehog video game series by Sega, directs the development of paired limbs in mammals. What’s been discovered here is that this same gene also directs the branchial rays, which support the gills of sharks, rays and skates.
The gene’s role in embryonic development of mammals – as well as in sharks, rays and skates that appeared much earlier in the fossil record – suggests that limbs evolved from gill arch appendages.
However, another possibility is that the Sonic Hedgehog gene happens to occur in two very different types of animals and is used for different purposes. Gillis said:
The fact that the Sonic Hedgehog gene performs the same two functions in the development of gill arches and branchial rays in skate embryos as it does in the development of limbs in mammal embryos may help explain how Gegenbaur arrived at his controversial theory on the origin of fins and limbs.
Skeletel preparation of a skate, in the late stage of embryonic development. Image via Andrew Gillis.
Gillis explained that the Sonic Hedgehog gene establishes the axis of a limb early in the development of mammal embryos and continues to guide growth until the limb is fully formed. He said:
In a hand, for instance, Sonic Hedgehog tells the limb which side will be the thumb and which side will be the pinky finger.
Gillis and his team discovered that the Sonic Hedgehog gene functioned similarly in skate embryo branchial ray growth and mammal embryo limb development. They interrupted the gene’s functions at different development phases in skate embryos. When the Sonic Hedgehog gene was inhibited during early growth phases, branchial rays grew from the wrong side of the skate’s gill arches. When it was done at later growth phases, branchial rays developed correctly but were fewer than usual.
In this image of a skate embryo, dark purple strips running down the length of each gill arch show sections developed by the Sonic Hedgehog gene. Image via Andrew Gillis.
Gillis remarked in his statement:
Taken to the extreme, these experiments could be interpreted as evidence that limbs share a genetic program with gill arches because fins and limbs evolved by transformation of a gill arch in an ancestral vertebrate, as proposed by Gegenbaur.
However, it could also be that these structures evolved separately, but re-used the same pre-existing genetic program. Without fossil evidence this remains a bit of a mystery–there is a gap in the fossil record between species with no fins and then suddenly species with paired fins.
So we can’t really be sure yet how paired appendages evolved.
Either way this is a fascinating discovery, because it provides evidence for a fundamental evolutionary link between branchial rays and limbs. While paleontologists look for fossils to try to reconstruct the evolutionary history of anatomy, we are effectively trying to reconstruct the evolutionary history of genetic programs that control the development of anatomy.
What we are learning is that many novel features may not have arisen suddenly from scratch, but rather by tweaking and re-using a relatively small number of ancient developmental programs.
The video below shows the embryonic development of a little skate (Leucoraja erinacea):
Bottom line: The Sonic Hedgehog gene drives embryonic development of mammal limbs and shark gills. Could our limbs have evolved from gills?
from EarthSky http://ift.tt/249igus
Skeleton of an embryonic bamboo shark, viewed from the underside. Gill arch appendages extend from each side of the head. Directly below them are a pair of fins. Image via Andrew Gillis.
In 1878, German anatomist Karl Gegenbaur suggested that paired human limbs – like our hands and feet – evolved from the paired fins of fish, and, before that, from fishes’ gills. But there was no fossil evidence to verify his theory.
New genetic research indicates that Gegenbaur may have been on the right track. A paper published in April, 2016, in the journal Development reports that the Sonic Hedgehog gene – already known to be essential for embryo development in mammals, such as humans, including the formation of limbs – is also responsible for developing appendages called branchial rays in skate embryos.
Skin flaps that protect the gills of cartilaginous fish – sharks, skates, rays – are supported by arch-like cartilage structures. Protruding from these cartilage arches are the branchial rays.
Dr. Andrew Gillis, at the University of Cambridge and also affiliated with the Marine Biological Laboratory, was lead researcher in this study. He said in a statement:
Gegenbaur looked at the way that these branchial rays connect to the gill arches and noticed that it looks very similar to the way that the fin and limb skeleton articulates with the shoulder.
The Sonic Hedgehog gene, named by a researcher at Harvard Medical School after the Sonic the Hedgehog video game series by Sega, directs the development of paired limbs in mammals. What’s been discovered here is that this same gene also directs the branchial rays, which support the gills of sharks, rays and skates.
The gene’s role in embryonic development of mammals – as well as in sharks, rays and skates that appeared much earlier in the fossil record – suggests that limbs evolved from gill arch appendages.
However, another possibility is that the Sonic Hedgehog gene happens to occur in two very different types of animals and is used for different purposes. Gillis said:
The fact that the Sonic Hedgehog gene performs the same two functions in the development of gill arches and branchial rays in skate embryos as it does in the development of limbs in mammal embryos may help explain how Gegenbaur arrived at his controversial theory on the origin of fins and limbs.
Skeletel preparation of a skate, in the late stage of embryonic development. Image via Andrew Gillis.
Gillis explained that the Sonic Hedgehog gene establishes the axis of a limb early in the development of mammal embryos and continues to guide growth until the limb is fully formed. He said:
In a hand, for instance, Sonic Hedgehog tells the limb which side will be the thumb and which side will be the pinky finger.
Gillis and his team discovered that the Sonic Hedgehog gene functioned similarly in skate embryo branchial ray growth and mammal embryo limb development. They interrupted the gene’s functions at different development phases in skate embryos. When the Sonic Hedgehog gene was inhibited during early growth phases, branchial rays grew from the wrong side of the skate’s gill arches. When it was done at later growth phases, branchial rays developed correctly but were fewer than usual.
In this image of a skate embryo, dark purple strips running down the length of each gill arch show sections developed by the Sonic Hedgehog gene. Image via Andrew Gillis.
Gillis remarked in his statement:
Taken to the extreme, these experiments could be interpreted as evidence that limbs share a genetic program with gill arches because fins and limbs evolved by transformation of a gill arch in an ancestral vertebrate, as proposed by Gegenbaur.
However, it could also be that these structures evolved separately, but re-used the same pre-existing genetic program. Without fossil evidence this remains a bit of a mystery–there is a gap in the fossil record between species with no fins and then suddenly species with paired fins.
So we can’t really be sure yet how paired appendages evolved.
Either way this is a fascinating discovery, because it provides evidence for a fundamental evolutionary link between branchial rays and limbs. While paleontologists look for fossils to try to reconstruct the evolutionary history of anatomy, we are effectively trying to reconstruct the evolutionary history of genetic programs that control the development of anatomy.
What we are learning is that many novel features may not have arisen suddenly from scratch, but rather by tweaking and re-using a relatively small number of ancient developmental programs.
The video below shows the embryonic development of a little skate (Leucoraja erinacea):
Bottom line: The Sonic Hedgehog gene drives embryonic development of mammal limbs and shark gills. Could our limbs have evolved from gills?
from EarthSky http://ift.tt/249igus
The hilarity continues: Jake Crosby echoes Brian Hooker’s claims that “The Man” has gotten to the “CDC whistleblower” [Respectful Insolence]
Three days ago, I noted a disturbance in the antivaccine Force.
Last night, I noticed that that disturbance continues.
The first time around, it was Brian Hooker, a biochemical engineer turned incompetent antivaccine “epidemiologist” completed the circle of clueless conspiracy mongering, who was at the center of the disturbance. His conspira-woo tapped into the Dark Side of the Force by taking a conspiracy theory that the antivaccine movement has been flogging for nearly two years now (as hard as it is to believe, it started in August 2014!), a conspiracy known as the “CDC whistleblower” and bringing it full circle as a means of preparing the people who have believed it for what appears to be an imminent disappointment coming down the pike. He did that by claiming that “The Man” had gotten to the CDC whistleblower, who, if you believe Hooker, is on the verge of basically recanting his claims about vaccines by publishing a reanalysis of the dataset whose original analysis had created him in the first place.
I’ll back up a minute, for the benefit of newbies to this blog. I’ve explained who and what the CDC whistleblower is and how the story of William W. Thompson (the CDC scientist whose indiscretions led him to become known as the “CDC whistleblower”) became so popular in the antivaccine cranksophere many times, most recently here. The reason that the CDC whistleblower myth has resonated so strongly among members of the antivaccine movement is obvious. Taken at face value, saga seems to provide evidence to support to what I like to call the central conspiracy theory of the antivaccine movement, namely that the CDC “knows” that vaccines cause autism, has evidence proving it, but has been covering up that evidence to protect…well, it’s never clear exactly who is being “protected,” but always pharmaceutical companies seem to be involved in some way.
This myth came to be as a result of Thompson having reached out to Brian Hooker, apparently to bitch and moan about his job, how he was not appreciated, and how his colleagues and coauthors on one specific study didn’t listen to his demands that an obviously spurious result suggesting a link between vaccines and autism in African American boys be included in an epidemiological study examining MMR vaccination as a risk factor for autism. Unfortunately, for Thompson, Hooker betrayed him by secretly recording their phone calls together and letting antivaccine guru Andrew Wakefield know he had a live one. Meanwhile, with Thompson’s guidance, Hooker “reanalyzed” the dataset (incompetently) and “found” in the unadjusted data the correlation he as looking for.
In any case, Thompson lawyered up and hasn’t been heard from, publicly at least, since September 2014. For the antivaccine movement, this has been a very good thing indeed, having the salutary effect of letting antivaccinationists attribute to Thompson any viewpoint they wish to impose on him. Certainly, they’ve done just that, using Thompson to claim falsely that the CDC has been “covering up” the link between the MMR vaccine in African-American boys, using that claim to sucker the Nation of Islam into protesting at the CDC with them last fall. For nearly two years, antivaccinationists have milked the CDC whistleblower story for all it’s worth. Fortunately, outside the antivaccine whackosphere, the story hasn’t resonated very much because it’s so obviously a conspiracy theory to most journalists (with the exception of Ben Swann, of course). Then, when all the documents that Thompson had given to Rep. Bill Posey (R-FL) that supposedly revealed the coverup were released by Matt Carey, it turned out there was no there there; the documents showed no evidence of a conspiracy to cover up data anywhere to be found.
Then, for some reason, three days ago Brian Hooker pivoted from praising Thompson and using him as “proof” that the CDC has been covering up “smoking gun” evidence of a link between vaccines and autism to seemingly launching a pre-emptive attack on him for being a turncoat. In essence, Hooker claimed that that ”The Man” had gotten to Thompson. Not long after I discussed that development, Brian Hooker issued a press release:
Very recently, Mr. Richard Morgan, Esq., Dr. Thompson’s whistle blower attorney, stated that Dr. Thompson will be publishing a paper in May, 2016, where he will assert that the MMR vaccine is not linked to autism in African American males. Instead Dr. Thompson will state that socioeconomic factors alone in the African American community account for the original MMR-African American male “effect” (the effect that he is on record as stating the CDC purposefully hid). I have not been given access to Dr. Thompson’s reanalysis and therefore cannot comment regarding the forthcoming paper at this time. However, I am suspect of any analysis coming from the CDC due to the historic nature of the agency’s scientific misconduct and conflicts of interest specifically around any link between vaccines and autism.
I laughed out loud—seriously, I did—when I read this paragraph. If there is a single paragraph that distills the antivaccine mindset into about 130 words, it’s the paragraph above, specifically the part about how, even though Hooker has not been given access to Thompson’s reanalysis (if such an a reanalysis is even forthcoming) he is suspect of any analysis coming from the CDC. This is, of course, a stunning turnaround from Hooker’s conversations with Thompson that Hooker surreptitiously recorded, in which the two chatted back and forth like old buddies. Obviously, to Hooker, Thompson’s “recantation” can’t be due to his having decided that maybe he had perseverated too long on a spurious result and, to ease his mind, did the reanalysis and found no correlation between the MMR vaccine and autism in African-American mailes. It must be because nefarious forces in the CDC “got” to him.
As amusing as Hooker’s flailing was, he’s got nothing on his young Padawan, Jake Crosby, who seems to have become disillusioned with both Andrew Wakefield and Brian Hooker (although certainly less so about Brian Hooker), but has not become any less antivaccine than he ever was back in his Age of Autism days. You remember Crosby, don’t you? I used to take it easy on him because back in the day I felt it unseemly to beat up too much on an autistic teenager and hoped that he might someday find his way out of the antivaccine quackhole that he had found himself in. For instance, when he wrote about his silly conspiracy theory about ScienceBlogs, I largely shrugged, referred to him as a “crazy mixed up kid,” and offered him some fatherly advice, given that I am indeed old enough to be his father. Even when he lied about me, claiming I had an undisclosed conflict of interest in my research into the drug riluzole. It was a lie that led to an attempt by antivaccinationists to get me fired and, six years later, was regurgitated by Mike Adams (and, to be fair, others) in his recent torrent of abuse aimed at me. These days, Crosby is old enough that he no longer rates any consideration when he attacks me or spews antivaccine misinformation; so I treat him basically the same way I treat most hard core antivaccinationists.
Six years after Crosby’s broadside against me, I think I’ve found my best revenge, and it comes from being able to laugh heartily at Crosby himself. Basically, Crosby’s written one of the silliest, dumbest things I’ve ever read on the Internet. It’s a demand, a hilarious demand:
For the phenomenon that Offit described to occur, one would expect to see a diminished odds of vaccination for those ages among black autistic children compared to vaccination after age three, not an increased risk. In fact, that was probably why the race effect was yanked from the paper and thrown in the garbage in the first place. A comment under Offit’s article seeking to point that out was removed from the thread, even though it was part of an ongoing conversation with a CDC-tied attorney.
But worst of all, this claim will not be confined to Offit’s review. It will also be made in a published “reanalysis” of the CDC’s study due to be published next month, authored by none other than the very coauthor of the original study who raised the alarm in the first place: “whistleblower” William Thompson. According to his initial contact Dr. Brian Hooker, Thompson has been “handled.” He is expected to publish his “reanalysis” with a researcher named Michael Blank – who had advised the MMR vaccine maker GlaxoSmithKline. Among the promises Thompson has been allegedly bribed with are a huge bonus and his own autism research foundation. Not surprisingly, having a scientist claim that vaccination was caused by autism diagnoses likely made after vaccination instead of admitting that vaccines cause autism comes with a steep price. It’s just too bad that that price will also be the unnecessary harm to countless more children. To add insult to injury, Offit will apparently write a commentary accompanying this awful work.
Please write and call Dr. Thompson at the following numbers and email address and tell him to withdraw his “reanalysis” and that he will face ethical complaints against him due to the ridiculous nature of his claims.
And:
Also contact the journal publishing his paper as well and tell them withdraw his paper and that they too will face ethics complaints for publishing it. Here is the email for the Proceedings of the National Academy of Sciences, where the “reanalysis” will likely be published. You should let the journal know that it too will face an ethical complaint for publishing Thompson’s analysis and should withdraw it from press: pnas@nas.edu, Phone: 202-334-2679.
Yes, you read that right. Crosby is demanding the retraction of a paper that hasn’t even been published yet, a paper that might not even exist. Even more hilariously, he is demanding that retraction of a journal where the paper (if it even exists) might or might not be scheduled to be published. This is, without a doubt, one of the most risible things I’ve ever seen, and I fully expect that Crosby’s “demand” will be roundly ignored; that is, if anyone who has any actual knowledge of what the hell he’s talking about actually sees Crosby’s ranting, which is unlikely. One has to wonder how someone could go through a graduate program in epidemiology and not manage to understand a bit about how academic journals and academic publishing work. I laughed at Crosby. Hard.
My amusement aside I must confess that I don’t quite know what is going on here. The best guess that I can come up with is that Brian Hooker has been in contact with someone who claims to know that Thompson is the co-author on some sort of “reanalysis” of the data used for the 2004 paper that concluded that the MMR vaccine is not correlated with an increased risk of autism or autism spectrum disorders. How he got that information, who knows? Is Hooker’s information correct? Again, who knows? Will the article be published in PNAS? Again, who knows? I tend to doubt it. It used to be pretty much impossible to be published in PNAS if you don’t have a member of the National Academy of Sciences either as a co-author or a sponsor of your article. It’s true that, in response to complaints about how NAS members used to use PNAS as a dumping ground for results they couldn’t publish elsewhere and would sponsor questionable papers written by their buddies, the rules have changed to tighten up peer review such that it is no longer the preferred method to have an NAS member-contributed track. (At least, that’s what the website says; I don’t really believe it.) Even so, it’s still still pretty difficult to be published in PNAS. What member of the National Academy of Sciences would sponsor such a paper, anyway?
In any case, I do rather suspect that something is coming in May, some bit of news that antivaccinationists won’t like, be it a statement from Thompson or a paper in which Thompson and co-authors conclude there is no link between the MMR vaccine and autism. I can hardly wait, because I just love the taste of antivaccinationist tears of unfathomable sadness:
from ScienceBlogs http://ift.tt/1rEK9t4
Three days ago, I noted a disturbance in the antivaccine Force.
Last night, I noticed that that disturbance continues.
The first time around, it was Brian Hooker, a biochemical engineer turned incompetent antivaccine “epidemiologist” completed the circle of clueless conspiracy mongering, who was at the center of the disturbance. His conspira-woo tapped into the Dark Side of the Force by taking a conspiracy theory that the antivaccine movement has been flogging for nearly two years now (as hard as it is to believe, it started in August 2014!), a conspiracy known as the “CDC whistleblower” and bringing it full circle as a means of preparing the people who have believed it for what appears to be an imminent disappointment coming down the pike. He did that by claiming that “The Man” had gotten to the CDC whistleblower, who, if you believe Hooker, is on the verge of basically recanting his claims about vaccines by publishing a reanalysis of the dataset whose original analysis had created him in the first place.
I’ll back up a minute, for the benefit of newbies to this blog. I’ve explained who and what the CDC whistleblower is and how the story of William W. Thompson (the CDC scientist whose indiscretions led him to become known as the “CDC whistleblower”) became so popular in the antivaccine cranksophere many times, most recently here. The reason that the CDC whistleblower myth has resonated so strongly among members of the antivaccine movement is obvious. Taken at face value, saga seems to provide evidence to support to what I like to call the central conspiracy theory of the antivaccine movement, namely that the CDC “knows” that vaccines cause autism, has evidence proving it, but has been covering up that evidence to protect…well, it’s never clear exactly who is being “protected,” but always pharmaceutical companies seem to be involved in some way.
This myth came to be as a result of Thompson having reached out to Brian Hooker, apparently to bitch and moan about his job, how he was not appreciated, and how his colleagues and coauthors on one specific study didn’t listen to his demands that an obviously spurious result suggesting a link between vaccines and autism in African American boys be included in an epidemiological study examining MMR vaccination as a risk factor for autism. Unfortunately, for Thompson, Hooker betrayed him by secretly recording their phone calls together and letting antivaccine guru Andrew Wakefield know he had a live one. Meanwhile, with Thompson’s guidance, Hooker “reanalyzed” the dataset (incompetently) and “found” in the unadjusted data the correlation he as looking for.
In any case, Thompson lawyered up and hasn’t been heard from, publicly at least, since September 2014. For the antivaccine movement, this has been a very good thing indeed, having the salutary effect of letting antivaccinationists attribute to Thompson any viewpoint they wish to impose on him. Certainly, they’ve done just that, using Thompson to claim falsely that the CDC has been “covering up” the link between the MMR vaccine in African-American boys, using that claim to sucker the Nation of Islam into protesting at the CDC with them last fall. For nearly two years, antivaccinationists have milked the CDC whistleblower story for all it’s worth. Fortunately, outside the antivaccine whackosphere, the story hasn’t resonated very much because it’s so obviously a conspiracy theory to most journalists (with the exception of Ben Swann, of course). Then, when all the documents that Thompson had given to Rep. Bill Posey (R-FL) that supposedly revealed the coverup were released by Matt Carey, it turned out there was no there there; the documents showed no evidence of a conspiracy to cover up data anywhere to be found.
Then, for some reason, three days ago Brian Hooker pivoted from praising Thompson and using him as “proof” that the CDC has been covering up “smoking gun” evidence of a link between vaccines and autism to seemingly launching a pre-emptive attack on him for being a turncoat. In essence, Hooker claimed that that ”The Man” had gotten to Thompson. Not long after I discussed that development, Brian Hooker issued a press release:
Very recently, Mr. Richard Morgan, Esq., Dr. Thompson’s whistle blower attorney, stated that Dr. Thompson will be publishing a paper in May, 2016, where he will assert that the MMR vaccine is not linked to autism in African American males. Instead Dr. Thompson will state that socioeconomic factors alone in the African American community account for the original MMR-African American male “effect” (the effect that he is on record as stating the CDC purposefully hid). I have not been given access to Dr. Thompson’s reanalysis and therefore cannot comment regarding the forthcoming paper at this time. However, I am suspect of any analysis coming from the CDC due to the historic nature of the agency’s scientific misconduct and conflicts of interest specifically around any link between vaccines and autism.
I laughed out loud—seriously, I did—when I read this paragraph. If there is a single paragraph that distills the antivaccine mindset into about 130 words, it’s the paragraph above, specifically the part about how, even though Hooker has not been given access to Thompson’s reanalysis (if such an a reanalysis is even forthcoming) he is suspect of any analysis coming from the CDC. This is, of course, a stunning turnaround from Hooker’s conversations with Thompson that Hooker surreptitiously recorded, in which the two chatted back and forth like old buddies. Obviously, to Hooker, Thompson’s “recantation” can’t be due to his having decided that maybe he had perseverated too long on a spurious result and, to ease his mind, did the reanalysis and found no correlation between the MMR vaccine and autism in African-American mailes. It must be because nefarious forces in the CDC “got” to him.
As amusing as Hooker’s flailing was, he’s got nothing on his young Padawan, Jake Crosby, who seems to have become disillusioned with both Andrew Wakefield and Brian Hooker (although certainly less so about Brian Hooker), but has not become any less antivaccine than he ever was back in his Age of Autism days. You remember Crosby, don’t you? I used to take it easy on him because back in the day I felt it unseemly to beat up too much on an autistic teenager and hoped that he might someday find his way out of the antivaccine quackhole that he had found himself in. For instance, when he wrote about his silly conspiracy theory about ScienceBlogs, I largely shrugged, referred to him as a “crazy mixed up kid,” and offered him some fatherly advice, given that I am indeed old enough to be his father. Even when he lied about me, claiming I had an undisclosed conflict of interest in my research into the drug riluzole. It was a lie that led to an attempt by antivaccinationists to get me fired and, six years later, was regurgitated by Mike Adams (and, to be fair, others) in his recent torrent of abuse aimed at me. These days, Crosby is old enough that he no longer rates any consideration when he attacks me or spews antivaccine misinformation; so I treat him basically the same way I treat most hard core antivaccinationists.
Six years after Crosby’s broadside against me, I think I’ve found my best revenge, and it comes from being able to laugh heartily at Crosby himself. Basically, Crosby’s written one of the silliest, dumbest things I’ve ever read on the Internet. It’s a demand, a hilarious demand:
For the phenomenon that Offit described to occur, one would expect to see a diminished odds of vaccination for those ages among black autistic children compared to vaccination after age three, not an increased risk. In fact, that was probably why the race effect was yanked from the paper and thrown in the garbage in the first place. A comment under Offit’s article seeking to point that out was removed from the thread, even though it was part of an ongoing conversation with a CDC-tied attorney.
But worst of all, this claim will not be confined to Offit’s review. It will also be made in a published “reanalysis” of the CDC’s study due to be published next month, authored by none other than the very coauthor of the original study who raised the alarm in the first place: “whistleblower” William Thompson. According to his initial contact Dr. Brian Hooker, Thompson has been “handled.” He is expected to publish his “reanalysis” with a researcher named Michael Blank – who had advised the MMR vaccine maker GlaxoSmithKline. Among the promises Thompson has been allegedly bribed with are a huge bonus and his own autism research foundation. Not surprisingly, having a scientist claim that vaccination was caused by autism diagnoses likely made after vaccination instead of admitting that vaccines cause autism comes with a steep price. It’s just too bad that that price will also be the unnecessary harm to countless more children. To add insult to injury, Offit will apparently write a commentary accompanying this awful work.
Please write and call Dr. Thompson at the following numbers and email address and tell him to withdraw his “reanalysis” and that he will face ethical complaints against him due to the ridiculous nature of his claims.
And:
Also contact the journal publishing his paper as well and tell them withdraw his paper and that they too will face ethics complaints for publishing it. Here is the email for the Proceedings of the National Academy of Sciences, where the “reanalysis” will likely be published. You should let the journal know that it too will face an ethical complaint for publishing Thompson’s analysis and should withdraw it from press: pnas@nas.edu, Phone: 202-334-2679.
Yes, you read that right. Crosby is demanding the retraction of a paper that hasn’t even been published yet, a paper that might not even exist. Even more hilariously, he is demanding that retraction of a journal where the paper (if it even exists) might or might not be scheduled to be published. This is, without a doubt, one of the most risible things I’ve ever seen, and I fully expect that Crosby’s “demand” will be roundly ignored; that is, if anyone who has any actual knowledge of what the hell he’s talking about actually sees Crosby’s ranting, which is unlikely. One has to wonder how someone could go through a graduate program in epidemiology and not manage to understand a bit about how academic journals and academic publishing work. I laughed at Crosby. Hard.
My amusement aside I must confess that I don’t quite know what is going on here. The best guess that I can come up with is that Brian Hooker has been in contact with someone who claims to know that Thompson is the co-author on some sort of “reanalysis” of the data used for the 2004 paper that concluded that the MMR vaccine is not correlated with an increased risk of autism or autism spectrum disorders. How he got that information, who knows? Is Hooker’s information correct? Again, who knows? Will the article be published in PNAS? Again, who knows? I tend to doubt it. It used to be pretty much impossible to be published in PNAS if you don’t have a member of the National Academy of Sciences either as a co-author or a sponsor of your article. It’s true that, in response to complaints about how NAS members used to use PNAS as a dumping ground for results they couldn’t publish elsewhere and would sponsor questionable papers written by their buddies, the rules have changed to tighten up peer review such that it is no longer the preferred method to have an NAS member-contributed track. (At least, that’s what the website says; I don’t really believe it.) Even so, it’s still still pretty difficult to be published in PNAS. What member of the National Academy of Sciences would sponsor such a paper, anyway?
In any case, I do rather suspect that something is coming in May, some bit of news that antivaccinationists won’t like, be it a statement from Thompson or a paper in which Thompson and co-authors conclude there is no link between the MMR vaccine and autism. I can hardly wait, because I just love the taste of antivaccinationist tears of unfathomable sadness:
from ScienceBlogs http://ift.tt/1rEK9t4
Breakthrough Starshot aims for Alpha Centauri
The dream of traveling to the stars is alive and well. Artist’s concept via BreakthroughInitiatives.org.
Earlier this month, Russian high-tech billionaire Yuri Milner and others announced Breakthrough Starshot, a plan to spend $100 million to take a next step forward toward star travel in our time. They’ll use the funds to begin proof-of-concept studies for a 100-million-mile-per-hour flyby mission to the next-nearest star system, Alpha Centauri, located about 4 light-years or 25 trillion miles (40 trillion km) away. They will be seeking confirmation that it’s possible to use a 100-gigawatt light beam to propel approximately 1,000 ultra-lightweight nanocraft to 20 percent of light speed. If it’s shown to be possible, this fleet of nanostarships could reach Alpha Centauri within about 20 years of launch.
Due to the finite travel speed of light (including radio waves), we would then wait 4 more years to hear back from any nanocraft that successfully swept through the Alpha Centauri system.
This plan to launch our human ships into the vastness of space is being led by the same organization that – in July, 2015 – announced an unprecedented $100 million new effort in the Search for Extraterrestrial Intelligence (SETI). At its website, Breakthrough Initiatives describes itself as:
… a program of scientific and technological exploration, probing the big questions of life in the universe: Are we alone? Are there habitable worlds in our galactic neighborhood? Can we make the great leap to the stars? And can we think and act together – as one world in the cosmos?
Pete Worden, a former director of NASA AMES Research Center, will lead Breakthrough Starshot, advised by a committee of stellar scientists and engineers. The board consists of Yuri Milner, physicist Stephen Hawking and Facebook’s Mark Zuckerberg. Ann Druyan, Freeman Dyson, Mae Jemison and Avi Loeb also participated in the announcement at at One World Observatory in New York City on April 12, 2016.
Yuri Milner is a major funder of Breakthrough Initiatives. He was an early investor in Facebook and Twitter and has funded other large endeavors, for example, the largest award in the world in the field of Biomedicine and Life Sciences, called the Breakthrough Prize. Image via Rusnanotekh.com
Scientists believe there are 3 stars in the Alpha Centauri system, although Proxima Centauri – at .2 lightyears away from the other two, and the actual closest star to our sun – may not be physically bound. Illustration by Ian Morrison, via manyworlds.space
Although there’s only one planet known so far in the Alpha Centauri system, orbiting Alpha Centauri B, you can bet that – if we were aiming to send nanocraft there – astronomers would turn their attention to seeking more planets in this nearby star system.
Why haven’t we visited the Alpha Centauri system already? It’s because 25 trillion miles is a long, long way from here. Using existing technology, our fastest current spacecraft would require some 30,000 years to get there, said Breakthrough Starshot.
But all existing spacecraft are huge and clunky in contrast to the gram-scale nanostarships – dubbed StarChips – being proposed here. Breakthrough Starshot hopes to establish whether tiny, light ships, on sails pushed by a light beam, could fly a thousand times faster than the fastest spacecraft built up to now.
What I love about the Starshot concept is that it’s truly visionary, leaps and bounds beyond what’s been proposed so far for star travel, and yet still grounded in current, cutting-edge science and technology. Starshot envisions launching a mothership carrying the 1,000 tiny spacecraft to a high-altitude orbit. Each craft is a gram-scale wafer, carrying cameras, photon thrusters, power supply, navigation and communication equipment, and “constituting a fully functional space probe,” says the Starshot team.
Mission controllers would deploy the nanocraft – send them on their way – one by one. A ground-based laser array called a light beamer would be used to focus light on the sails of the ships, to accelerate individual craft to the target speed “within minutes.”
First photo of Earth from space, October 24, 1946, via White Sands Missile Range/Applied Physics Laboratory. Read more. The first images via nanocraft of the Alpha Centauri system would be rudimentary, perhaps like this first image of Earth?
The plan is to stick four cameras (two-megapixels each) on a chip that will allow for some elementary imaging. The data would be transmitted back to Earth using a retractable meter-long antenna, or perhaps even using the lightsail to facilitate laser-based communications that could focus a signal back towards Earth.
Breakthrough Starshot said in its recent statement that its plan:
… brings the Silicon Valley approach to space travel, capitalizing on exponential advances in certain areas of technology since the beginning of the 21st century.
For example, the lightsails would be made possible by advances in nanotechnology that are producing increasingly thin and light-weight metamaterials, which, Breakthrough Star said:
… promise to enable the fabrication of meter-scale sails no more than a few hundred atoms thick and at gram-scale mass.
The video below shows an animation of the proposed light beamer, a phased array of lasers for powering the lightsails and also for receiving information back from the nanocraft.
The research and engineering phase for Breakthrough Starshot is expected to last “a number of years.” Philip Lubin, a scientific advisor to the project, told Popular Science on April 27 that, in the initial phase:
… we will build a prototype laser array in the 10- to 100-kilowatt class, gram-scale ‘star-chips’ with imaging and other sensors and a laser communication system, and prototype sails, as well as explore the many technical challenges to building a full system.
Following that, development of the ultimate mission to Alpha Centauri would require a budget comparable to the largest current scientific experiments. Project leader Pete Worden mentioned a figure of “about $10 billion.” The full-scale effort would involve:
Building a ground-based kilometer-scale light beamer at high altitude in dry conditions.
Generating and storing a few gigawatt hours of energy per launch.
Launching a ‘mothership’ carrying thousands of nanocrafts to a high-altitude orbit.
Taking advantage of adaptive optics technology in real time to compensate for atmospheric effects.
Focusing the light beam on the lightsail to accelerate individual nanocrafts to the target speed within minutes.
Accounting for interstellar dust collisions en route to the target.
Capturing images of a planet, and other scientific data, and transmitting them back to Earth using a compact on-board laser communications system.
Using the same light beamer that launched the nanocrafts to receive data from them over 4 years later.
Breakthrough Starshot also plans to establish a research grant program, to make available other funding to support relevant scientific and engineering research and development. Yuri Milner, founder of the Breakthrough Initiatives, said:
The human story is one of great leaps. Just 55 years ago … Yuri Gagarin became the first human in space. Today, we are preparing for the next great leap, to the stars.
Stephen Hawking said:
Earth is a wonderful place, but it might not last forever. Sooner or later, we must look to the stars. Breakthrough Starshot is a very exciting first step on that journey.
Pete Worden said:
We take inspiration from Vostok, Voyager, Apollo and the other great missions. It’s time to open the era of interstellar flight, but we need to keep our feet on the ground to achieve this.
Bottom line: Breakthrough Starshot – part of the Breakthrough Initiatives – announced a plan in April, 2016, to send gram-scale nanostarship on a mission to Alpha Centauri, the next-nearest star system. The plan includes a travel time to this star system of only 20 Earth-years. An investment of $100 million has been committed for proof-of-concept studies in the coming years.
from EarthSky http://ift.tt/1WuKrxI
The dream of traveling to the stars is alive and well. Artist’s concept via BreakthroughInitiatives.org.
Earlier this month, Russian high-tech billionaire Yuri Milner and others announced Breakthrough Starshot, a plan to spend $100 million to take a next step forward toward star travel in our time. They’ll use the funds to begin proof-of-concept studies for a 100-million-mile-per-hour flyby mission to the next-nearest star system, Alpha Centauri, located about 4 light-years or 25 trillion miles (40 trillion km) away. They will be seeking confirmation that it’s possible to use a 100-gigawatt light beam to propel approximately 1,000 ultra-lightweight nanocraft to 20 percent of light speed. If it’s shown to be possible, this fleet of nanostarships could reach Alpha Centauri within about 20 years of launch.
Due to the finite travel speed of light (including radio waves), we would then wait 4 more years to hear back from any nanocraft that successfully swept through the Alpha Centauri system.
This plan to launch our human ships into the vastness of space is being led by the same organization that – in July, 2015 – announced an unprecedented $100 million new effort in the Search for Extraterrestrial Intelligence (SETI). At its website, Breakthrough Initiatives describes itself as:
… a program of scientific and technological exploration, probing the big questions of life in the universe: Are we alone? Are there habitable worlds in our galactic neighborhood? Can we make the great leap to the stars? And can we think and act together – as one world in the cosmos?
Pete Worden, a former director of NASA AMES Research Center, will lead Breakthrough Starshot, advised by a committee of stellar scientists and engineers. The board consists of Yuri Milner, physicist Stephen Hawking and Facebook’s Mark Zuckerberg. Ann Druyan, Freeman Dyson, Mae Jemison and Avi Loeb also participated in the announcement at at One World Observatory in New York City on April 12, 2016.
Yuri Milner is a major funder of Breakthrough Initiatives. He was an early investor in Facebook and Twitter and has funded other large endeavors, for example, the largest award in the world in the field of Biomedicine and Life Sciences, called the Breakthrough Prize. Image via Rusnanotekh.com
Scientists believe there are 3 stars in the Alpha Centauri system, although Proxima Centauri – at .2 lightyears away from the other two, and the actual closest star to our sun – may not be physically bound. Illustration by Ian Morrison, via manyworlds.space
Although there’s only one planet known so far in the Alpha Centauri system, orbiting Alpha Centauri B, you can bet that – if we were aiming to send nanocraft there – astronomers would turn their attention to seeking more planets in this nearby star system.
Why haven’t we visited the Alpha Centauri system already? It’s because 25 trillion miles is a long, long way from here. Using existing technology, our fastest current spacecraft would require some 30,000 years to get there, said Breakthrough Starshot.
But all existing spacecraft are huge and clunky in contrast to the gram-scale nanostarships – dubbed StarChips – being proposed here. Breakthrough Starshot hopes to establish whether tiny, light ships, on sails pushed by a light beam, could fly a thousand times faster than the fastest spacecraft built up to now.
What I love about the Starshot concept is that it’s truly visionary, leaps and bounds beyond what’s been proposed so far for star travel, and yet still grounded in current, cutting-edge science and technology. Starshot envisions launching a mothership carrying the 1,000 tiny spacecraft to a high-altitude orbit. Each craft is a gram-scale wafer, carrying cameras, photon thrusters, power supply, navigation and communication equipment, and “constituting a fully functional space probe,” says the Starshot team.
Mission controllers would deploy the nanocraft – send them on their way – one by one. A ground-based laser array called a light beamer would be used to focus light on the sails of the ships, to accelerate individual craft to the target speed “within minutes.”
First photo of Earth from space, October 24, 1946, via White Sands Missile Range/Applied Physics Laboratory. Read more. The first images via nanocraft of the Alpha Centauri system would be rudimentary, perhaps like this first image of Earth?
The plan is to stick four cameras (two-megapixels each) on a chip that will allow for some elementary imaging. The data would be transmitted back to Earth using a retractable meter-long antenna, or perhaps even using the lightsail to facilitate laser-based communications that could focus a signal back towards Earth.
Breakthrough Starshot said in its recent statement that its plan:
… brings the Silicon Valley approach to space travel, capitalizing on exponential advances in certain areas of technology since the beginning of the 21st century.
For example, the lightsails would be made possible by advances in nanotechnology that are producing increasingly thin and light-weight metamaterials, which, Breakthrough Star said:
… promise to enable the fabrication of meter-scale sails no more than a few hundred atoms thick and at gram-scale mass.
The video below shows an animation of the proposed light beamer, a phased array of lasers for powering the lightsails and also for receiving information back from the nanocraft.
The research and engineering phase for Breakthrough Starshot is expected to last “a number of years.” Philip Lubin, a scientific advisor to the project, told Popular Science on April 27 that, in the initial phase:
… we will build a prototype laser array in the 10- to 100-kilowatt class, gram-scale ‘star-chips’ with imaging and other sensors and a laser communication system, and prototype sails, as well as explore the many technical challenges to building a full system.
Following that, development of the ultimate mission to Alpha Centauri would require a budget comparable to the largest current scientific experiments. Project leader Pete Worden mentioned a figure of “about $10 billion.” The full-scale effort would involve:
Building a ground-based kilometer-scale light beamer at high altitude in dry conditions.
Generating and storing a few gigawatt hours of energy per launch.
Launching a ‘mothership’ carrying thousands of nanocrafts to a high-altitude orbit.
Taking advantage of adaptive optics technology in real time to compensate for atmospheric effects.
Focusing the light beam on the lightsail to accelerate individual nanocrafts to the target speed within minutes.
Accounting for interstellar dust collisions en route to the target.
Capturing images of a planet, and other scientific data, and transmitting them back to Earth using a compact on-board laser communications system.
Using the same light beamer that launched the nanocrafts to receive data from them over 4 years later.
Breakthrough Starshot also plans to establish a research grant program, to make available other funding to support relevant scientific and engineering research and development. Yuri Milner, founder of the Breakthrough Initiatives, said:
The human story is one of great leaps. Just 55 years ago … Yuri Gagarin became the first human in space. Today, we are preparing for the next great leap, to the stars.
Stephen Hawking said:
Earth is a wonderful place, but it might not last forever. Sooner or later, we must look to the stars. Breakthrough Starshot is a very exciting first step on that journey.
Pete Worden said:
We take inspiration from Vostok, Voyager, Apollo and the other great missions. It’s time to open the era of interstellar flight, but we need to keep our feet on the ground to achieve this.
Bottom line: Breakthrough Starshot – part of the Breakthrough Initiatives – announced a plan in April, 2016, to send gram-scale nanostarship on a mission to Alpha Centauri, the next-nearest star system. The plan includes a travel time to this star system of only 20 Earth-years. An investment of $100 million has been committed for proof-of-concept studies in the coming years.
from EarthSky http://ift.tt/1WuKrxI
How long would it take to get to Alpha Centauri?
The Alpha Centauri system. It’s at least a double system, maybe a triple system, but we see it with the eye as just one star. In this image – via MSX/IPAC/NASA – you can almost make out the double nature of Alpha Centauri.
Outer space is big. Really, really, really big. And that’s why NASA has no plans at present to send a spacecraft to any of the 2,000 and more known planets beyond our solar system. Meanwhile, NASA isn’t the only game in town anymore, and another organization has announced an investment in proof-of-concept studies for a plan to reach Alpha Centauri within 20 years. Alpha Centauri is the nearest star system to our sun at 4.3 light-years away. That’s about 25 trillion miles (40 trillion km) away from Earth – nearly 300,000 times the distance from the Earth to the sun. How might we travel to Alpha Centauri, the next-nearest star? And how long would it take to get there? Follow the links below to learn more.
Why won’t a conventional rocket work?
The Voyagers’ paths out of the solar system via Wikimedia Commons. Click here to expand image
Why won’t a conventional rocket work? Consider the Space Shuttles, which traveled only a few hundred kilometers into space. If Earth were the size of a sand grain, this would be about the width of a hair in contrast to a 10-kilometer distance to Alpha Centauri. You’d need about 10,000 shuttle main engines in sequence just to build up a decent speed (say, 1/100th light speed).
The Space Shuttles weren’t starships. At a maximum speed of about 17,600 mph (about 28,300 kph), it would have taken a Space Shuttle about 165,000 years to reach Alpha Centauri.
How about the Voyager spacecraft? These two unmanned space probes – Voyager 1 and Voyager 2 – were launched in 1977. They’re now heading out of our solar system. The Voyagers aren’t aimed toward Alpha Centauri, but if they were, they’d take tens of thousands of years to get there. Eventually, the Voyagers will pass other stars. In about 40,000 years, Voyager 1 will drift within 1.6 light-years (9.3 trillion miles) of AC+79 3888, a star in the constellation of Camelopardalis. In some 296,000 years, Voyager 2 will pass 4.3 light-years from Sirius, the brightest star in the sky. Hmm, 4.3 light-years. That’s the distance between us and Alpha Centauri.
What about the New Horizons spacecraft, the first spacecraft ever to visit Pluto and its moons. NASA’s New Horizons spacecraft travels at 36,373 miles per hour (58,536 km/h). Launched from Earth in mid-January, 2006, it reached Pluto in mid-July, 2015 … nine-and-a-half years later. If New Horizons were aimed toward the Alpha Centauri system, which it isn’t, it would take this spacecraft about 78,000 years to get there.
What a spaceship with warp drive might look like. Credit: Mark Rademaker/Mike Okuda/Harold White/NASA.
Illustration via the Anderson Institute.
Warp drive? So conventional rockets would take tens to hundreds of thousands of years to travel to Alpha Centauri. But what if we could travel faster than light? Sound impossible? A couple of years ago, Dr. Harold “Sonny” White – who leads NASA’s Advanced Propulsion Team at Johnson Space Center – claimed to have made a discovery which made plausible the idea of faster-than-light travel, via a concept known as the Alcubierre warp drive.
This concept is based on ideas put forward by Mexican physicist Miguel Alcubierre in 1994. He suggested that faster-than-light travel might be achieved by distorting spacetime, as shown in the illustration above.
Harold “Sonny” White has been working to investigate these ideas further, and, in June of 2014, he unveiled images of what a faster-than-light ship might look like. Artist Mark Rademaker based these designs on White’s theoretical ideas. He said creating them took more than 1,600 hours, and they are very cool. See the 2014 faster-than-light spacecraft designs on this Flickr page.
The video below presents Harold White’s talk at the SpaceVision 2013 Space Conference in November, 2013 in Phoenix. He talks about the concepts and progress in warp-drive development over recent decades.
Is it faster-than-light travel possible, via the Alcubierre warp drive? As with conventional propulsion systems, the problem is energy. In this case, it’s the type of energy the warp drive would need. Daily Kos reported:
In order to form the warp field/bubble, a region of space-time with negative energy density (i.e. repulsing space-time) is necessary. Scientific models predict exotic matter with a negative energy may exist, but it has never been observed. All forms of matter and light have a positive energy density, and create an attractive gravitational field.
So faster-than-light travel via the Alcubierre warp drive is highly speculative, to say the least.
With current technologies, it’s not possible.
However, if it could be accomplished, it would reduce the travel time to Alpha Centauri from thousands of years to just days.
Want technical details on the Alcubierre warp drive? Read this article on Daily Kos.
Artist’s concept via Breakthrough Starshot.
Breakthrough Starshot. In April, 2016, the Breakthrough Initiatives – led by Russian billionaire Yuri Milner – announced a $100 million investment in proof-of concept studies for an all-new way to get to the stars.
Well, not all new, exactly. The Breakthrough Starshot project relies on technologies that are being tested now, and also on some new technologies that have been around only a few years. But it does put these technologies together in a way that’s entirely new, and extremely visionary.
They Breakthrough Starshot team has some heavy hitters, including physicist Stephen Hawking and Facebook’s Mark Zuckerberg. It proposes to use the $100 million to learn whether it’s possible to use a 100-gigawatt light beam and light sails to propel some 1,000 ultra-lightweight nanocraft to 20 percent of light speed. If it’s shown to be possible, such a mission could (hypothetically) reach Alpha Centauri within about 20 years of its launch.
There are a lot of appealing things about this project. Although the idea for the nanostarships is extremely innovative, for example, the use of light sails is currently in the process of being tested by another organization, the Planetary Society, with a publicly funded project called LightSail. The first LightSail orbital test, in 2015, tested the spacecraft’s solar sail deployment mechanism, but did not fly high enough for the push from solar sailing to overcome Earth’s atmospheric drag.
The second LightSail test mission is planned for 2016. Read more about the Planetary Society’s LightSail.
There’s so much to say about Breakthrough Starshot that I’ve written another article about it, which you can find here.
Let me just add here that the concept is exciting, and I’m as anxious as you are to follow it in the years ahead!
Illustration via FutureHumanEvolution.com
Bottom line: At 4.3 light-years away, the Alpha Centauri system is the nearest star system to our Earth and sun, but getting there would be extremely difficult.
Breakthrough Starshot aims for Alpha Centauri
Read more about the Alpha Centauri system
from EarthSky http://ift.tt/10retol
The Alpha Centauri system. It’s at least a double system, maybe a triple system, but we see it with the eye as just one star. In this image – via MSX/IPAC/NASA – you can almost make out the double nature of Alpha Centauri.
Outer space is big. Really, really, really big. And that’s why NASA has no plans at present to send a spacecraft to any of the 2,000 and more known planets beyond our solar system. Meanwhile, NASA isn’t the only game in town anymore, and another organization has announced an investment in proof-of-concept studies for a plan to reach Alpha Centauri within 20 years. Alpha Centauri is the nearest star system to our sun at 4.3 light-years away. That’s about 25 trillion miles (40 trillion km) away from Earth – nearly 300,000 times the distance from the Earth to the sun. How might we travel to Alpha Centauri, the next-nearest star? And how long would it take to get there? Follow the links below to learn more.
Why won’t a conventional rocket work?
The Voyagers’ paths out of the solar system via Wikimedia Commons. Click here to expand image
Why won’t a conventional rocket work? Consider the Space Shuttles, which traveled only a few hundred kilometers into space. If Earth were the size of a sand grain, this would be about the width of a hair in contrast to a 10-kilometer distance to Alpha Centauri. You’d need about 10,000 shuttle main engines in sequence just to build up a decent speed (say, 1/100th light speed).
The Space Shuttles weren’t starships. At a maximum speed of about 17,600 mph (about 28,300 kph), it would have taken a Space Shuttle about 165,000 years to reach Alpha Centauri.
How about the Voyager spacecraft? These two unmanned space probes – Voyager 1 and Voyager 2 – were launched in 1977. They’re now heading out of our solar system. The Voyagers aren’t aimed toward Alpha Centauri, but if they were, they’d take tens of thousands of years to get there. Eventually, the Voyagers will pass other stars. In about 40,000 years, Voyager 1 will drift within 1.6 light-years (9.3 trillion miles) of AC+79 3888, a star in the constellation of Camelopardalis. In some 296,000 years, Voyager 2 will pass 4.3 light-years from Sirius, the brightest star in the sky. Hmm, 4.3 light-years. That’s the distance between us and Alpha Centauri.
What about the New Horizons spacecraft, the first spacecraft ever to visit Pluto and its moons. NASA’s New Horizons spacecraft travels at 36,373 miles per hour (58,536 km/h). Launched from Earth in mid-January, 2006, it reached Pluto in mid-July, 2015 … nine-and-a-half years later. If New Horizons were aimed toward the Alpha Centauri system, which it isn’t, it would take this spacecraft about 78,000 years to get there.
What a spaceship with warp drive might look like. Credit: Mark Rademaker/Mike Okuda/Harold White/NASA.
Illustration via the Anderson Institute.
Warp drive? So conventional rockets would take tens to hundreds of thousands of years to travel to Alpha Centauri. But what if we could travel faster than light? Sound impossible? A couple of years ago, Dr. Harold “Sonny” White – who leads NASA’s Advanced Propulsion Team at Johnson Space Center – claimed to have made a discovery which made plausible the idea of faster-than-light travel, via a concept known as the Alcubierre warp drive.
This concept is based on ideas put forward by Mexican physicist Miguel Alcubierre in 1994. He suggested that faster-than-light travel might be achieved by distorting spacetime, as shown in the illustration above.
Harold “Sonny” White has been working to investigate these ideas further, and, in June of 2014, he unveiled images of what a faster-than-light ship might look like. Artist Mark Rademaker based these designs on White’s theoretical ideas. He said creating them took more than 1,600 hours, and they are very cool. See the 2014 faster-than-light spacecraft designs on this Flickr page.
The video below presents Harold White’s talk at the SpaceVision 2013 Space Conference in November, 2013 in Phoenix. He talks about the concepts and progress in warp-drive development over recent decades.
Is it faster-than-light travel possible, via the Alcubierre warp drive? As with conventional propulsion systems, the problem is energy. In this case, it’s the type of energy the warp drive would need. Daily Kos reported:
In order to form the warp field/bubble, a region of space-time with negative energy density (i.e. repulsing space-time) is necessary. Scientific models predict exotic matter with a negative energy may exist, but it has never been observed. All forms of matter and light have a positive energy density, and create an attractive gravitational field.
So faster-than-light travel via the Alcubierre warp drive is highly speculative, to say the least.
With current technologies, it’s not possible.
However, if it could be accomplished, it would reduce the travel time to Alpha Centauri from thousands of years to just days.
Want technical details on the Alcubierre warp drive? Read this article on Daily Kos.
Artist’s concept via Breakthrough Starshot.
Breakthrough Starshot. In April, 2016, the Breakthrough Initiatives – led by Russian billionaire Yuri Milner – announced a $100 million investment in proof-of concept studies for an all-new way to get to the stars.
Well, not all new, exactly. The Breakthrough Starshot project relies on technologies that are being tested now, and also on some new technologies that have been around only a few years. But it does put these technologies together in a way that’s entirely new, and extremely visionary.
They Breakthrough Starshot team has some heavy hitters, including physicist Stephen Hawking and Facebook’s Mark Zuckerberg. It proposes to use the $100 million to learn whether it’s possible to use a 100-gigawatt light beam and light sails to propel some 1,000 ultra-lightweight nanocraft to 20 percent of light speed. If it’s shown to be possible, such a mission could (hypothetically) reach Alpha Centauri within about 20 years of its launch.
There are a lot of appealing things about this project. Although the idea for the nanostarships is extremely innovative, for example, the use of light sails is currently in the process of being tested by another organization, the Planetary Society, with a publicly funded project called LightSail. The first LightSail orbital test, in 2015, tested the spacecraft’s solar sail deployment mechanism, but did not fly high enough for the push from solar sailing to overcome Earth’s atmospheric drag.
The second LightSail test mission is planned for 2016. Read more about the Planetary Society’s LightSail.
There’s so much to say about Breakthrough Starshot that I’ve written another article about it, which you can find here.
Let me just add here that the concept is exciting, and I’m as anxious as you are to follow it in the years ahead!
Illustration via FutureHumanEvolution.com
Bottom line: At 4.3 light-years away, the Alpha Centauri system is the nearest star system to our Earth and sun, but getting there would be extremely difficult.
Breakthrough Starshot aims for Alpha Centauri
Read more about the Alpha Centauri system
from EarthSky http://ift.tt/10retol
Last quarter moon rises around midnight
Tonight – April 29, 2016 – the moon won’t rise over your eastern horizon until late, likely after midnight. Given clear skies, you should easily see the moon in the morning sky, even after sunrise, on April 30. The moon will be at or near its half-lit last quarter phase, when the moon’s disk appears half-illuminated in sunlight and half-immersed in its own shadow. It’ll look like the image at the top of this post, which is by Lilliana Mendez of North Bergen, New Jersey.
In the larger view, of course, the moon is always half-illuminated. Now we’re seeing half the moon’s day side, and half its night side.
The terminator – shadow line dividing the lunar day and night – shows you line of sunset on the waning moon. It’s along the terminator that you have your best views of the lunar terrain through binoculars or the telescope.
You might think the half-illuminated quarter moon should be about half as bright as the full moon. But that’s not the case. The last quarter moon is about 1/12th as bright as a full moon. Astronomers say the moon’s rough, sphere-shaped surface accounts for the surprising difference in the amount of moonlight cast by the quarter moon versus the full moon.
Meanwhile – and this might surprise you – the first quarter moon is slightly brighter than the last quarter moon. It shines at about 1/11th a full moon’s brightness (in contrast to 1/12th).
The last quarter moon is also called the third quarter moon. Contrast the illuminated sides of the first quarter and third quarter moons to see that the greater area of dark maria covers the third quarter moon. The dark maria make the third quarter moon slightly fainter than the first quarter moon. Image via NASA/Bill Dunford.
The last quarter moon is slightly less bright than the first quarter moon. That’s because illuminated side of the last quarter moon is more covered over by maria – low lying plains of hardened volcanic basalt.
The dark maria reflect sunlight less effectively than do the lighter-colored lunar highlands.
Bottom line: Watch for the moon at or near its last quarter phase. It’ll likely rise after midnight on the morning of April 30, 2016.
from EarthSky http://ift.tt/1NoR0Af
Tonight – April 29, 2016 – the moon won’t rise over your eastern horizon until late, likely after midnight. Given clear skies, you should easily see the moon in the morning sky, even after sunrise, on April 30. The moon will be at or near its half-lit last quarter phase, when the moon’s disk appears half-illuminated in sunlight and half-immersed in its own shadow. It’ll look like the image at the top of this post, which is by Lilliana Mendez of North Bergen, New Jersey.
In the larger view, of course, the moon is always half-illuminated. Now we’re seeing half the moon’s day side, and half its night side.
The terminator – shadow line dividing the lunar day and night – shows you line of sunset on the waning moon. It’s along the terminator that you have your best views of the lunar terrain through binoculars or the telescope.
You might think the half-illuminated quarter moon should be about half as bright as the full moon. But that’s not the case. The last quarter moon is about 1/12th as bright as a full moon. Astronomers say the moon’s rough, sphere-shaped surface accounts for the surprising difference in the amount of moonlight cast by the quarter moon versus the full moon.
Meanwhile – and this might surprise you – the first quarter moon is slightly brighter than the last quarter moon. It shines at about 1/11th a full moon’s brightness (in contrast to 1/12th).
The last quarter moon is also called the third quarter moon. Contrast the illuminated sides of the first quarter and third quarter moons to see that the greater area of dark maria covers the third quarter moon. The dark maria make the third quarter moon slightly fainter than the first quarter moon. Image via NASA/Bill Dunford.
The last quarter moon is slightly less bright than the first quarter moon. That’s because illuminated side of the last quarter moon is more covered over by maria – low lying plains of hardened volcanic basalt.
The dark maria reflect sunlight less effectively than do the lighter-colored lunar highlands.
Bottom line: Watch for the moon at or near its last quarter phase. It’ll likely rise after midnight on the morning of April 30, 2016.
from EarthSky http://ift.tt/1NoR0Af
Why does gravity move at the speed of light? (Synopsis) [Starts With A Bang]
“The fact that gravitational damping is measured at all is a strong indication that the propagation speed of gravity is not infinite. If the calculational framework of general relativity is accepted, the damping can be used to calculate the speed, and the actual measurement confirms that the speed of gravity is equal to the speed of light to within 1%.” -Steve Carlip
According to General Relativity, the speed of gravity must be equal to the speed of light. Since gravitational radiation is massless, it therefore must propagate at c, or the speed of light in a vacuum. But given that the Earth orbits the Sun, if it were attracted to the Sun’s position some 8 minutes ago instead of its present position, the planetary orbits would disagree with what we observe!
Image credit: David Champion, Max Planck Institute for Radio Astronomy.
What, then, is the resolution to this? It turns out that in relativity itself, what we experience as gravitation is also dependent on both speed and changes in the gravitational field, both of which play a role. From observations of binary pulsars, a gravitationally lensed quasar and, most recently, direct gravitational waves themselves, we can constrain the speed of gravity to be very close to the speed of light, with remarkable precision.
The quasar QSO J0842+1835, whose path was gravitationally altered by Jupiter in 2002, allowing an indirect confirmation that the speed of gravity equals the speed of light. Image credit: Fomalont et al. (2000), ApJS 131, 95-183, via http://ift.tt/1TznnM5.
Come get the full story, only over on Forbes!
from ScienceBlogs http://ift.tt/1WVXeK7
“The fact that gravitational damping is measured at all is a strong indication that the propagation speed of gravity is not infinite. If the calculational framework of general relativity is accepted, the damping can be used to calculate the speed, and the actual measurement confirms that the speed of gravity is equal to the speed of light to within 1%.” -Steve Carlip
According to General Relativity, the speed of gravity must be equal to the speed of light. Since gravitational radiation is massless, it therefore must propagate at c, or the speed of light in a vacuum. But given that the Earth orbits the Sun, if it were attracted to the Sun’s position some 8 minutes ago instead of its present position, the planetary orbits would disagree with what we observe!
Image credit: David Champion, Max Planck Institute for Radio Astronomy.
What, then, is the resolution to this? It turns out that in relativity itself, what we experience as gravitation is also dependent on both speed and changes in the gravitational field, both of which play a role. From observations of binary pulsars, a gravitationally lensed quasar and, most recently, direct gravitational waves themselves, we can constrain the speed of gravity to be very close to the speed of light, with remarkable precision.
The quasar QSO J0842+1835, whose path was gravitationally altered by Jupiter in 2002, allowing an indirect confirmation that the speed of gravity equals the speed of light. Image credit: Fomalont et al. (2000), ApJS 131, 95-183, via http://ift.tt/1TznnM5.
Come get the full story, only over on Forbes!
from ScienceBlogs http://ift.tt/1WVXeK7
Inscription à :
Articles (Atom)