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Article: Gravitational waves: talk to a scientist behind the discovery watch

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    (Original post by Student403)
    My first question is why did you let Caltech reject me? :cry2:

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    seriously though this is great news! I can't wait for the 22nd!
    Glad you're able to join the discussion on the 22nd! Can't help about Caltech, however....
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    (Original post by Martin Hendry)
    Glad you're able to join the discussion on the 22nd! Can't help about Caltech, however....
    Just a jest! So happy to have an expert on TSR
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    (Original post by EnglishMuon)
    Do you believe there is a significant difference (advantage/disadvantage) between studying maths rather than physics for an undergraduate degree if you would like to study these 'applied' fields later on? To me maths courses seem to fit my thinking style more but maybe physics is more directly applicable to a research job? Any thoughts would be appreciated!
    An interesting question. I don't think there's a straightforward answer: it'll depend on the individual, and on the strengths and merits of the specific degree programme. In my case I studied maths, physics and astronomy for two years, just to keep my options as open as possible, and then pursued maths and astronomy after that. My decision was mainly driven by the fact that I wanted to pursue a PhD in theoretical cosmology after I graduated and I felt that doing more maths courses would help with that. However, I have benefitted a great deal from the physics courses I did too; certainly I think doing pure maths, and getting little or no opportunity to carry out experimental / observational work, could be a bit limiting when it comes to postgraduate options in many areas of physics.
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    (Original post by Student403)
    Do you wish school students (GCSE/A Level) showed more interest in modern research and scientific discoveries? And do you think involvement would inspire a lot more young scientists?

    If so, what would be your ideal plan to get students involved and interested? Perhaps an addition to our current specification asking us to write some kind of report based on contemporary research or affairs in the scientific world?

    Thank you for your time
    The short answer is "yes": I think it's great to let students see that physics isn't just about topics that were worked out hundreds of years ago, by historical figures like Isaac Newton or Galileo, but is a field that's constantly changing and evolving as we discover new things about the universe and devise new applications that help us to improve the world around us.

    Your idea about a report seems a good one to me. My knowledge of the GCSE and A level syllabus is quite limited, as most Scottish Schools teach the Higher and Advanced Higher physics syllabus. I was involved in the redesign of the Higher and Advanced Higher physics courses recently, as part of the Scottish "Curriculum for Excellence" that's been introduced in schools, and the higher includes a new module (designed to involve about 20 hours of learning) entitled "Researching Physics" in which students are encouraged to find out about a cutting-edge topic in current physics research. There are also small sections on cosmology, astrophysics, particle physics, relativity and quantum physics as part of the overall higher and advanced higher syllabus. So far students seem to be responding very positively to this new material...
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    (Original post by Martin Hendry)
    An interesting question. I don't think there's a straightforward answer: it'll depend on the individual, and on the strengths and merits of the specific degree programme. In my case I studied maths, physics and astronomy for two years, just to keep my options as open as possible, and then pursued maths and astronomy after that. My decision was mainly driven by the fact that I wanted to pursue a PhD in theoretical cosmology after I graduated and I felt that doing more maths courses would help with that. However, I have benefitted a great deal from the physics courses I did too; certainly I think doing pure maths, and getting little or no opportunity to carry out experimental / observational work, could be a bit limiting when it comes to postgraduate options in many areas of physics.
    Thanks very much for the reply! Its nice to know that you focused on the maths side at points (although Im sure all your work is pretty maths focused anyway), this is definitely the root I would like to go Also, I've seen a fair few questions asking about the other 'real life' applications of this discovery, but are there any specific mathematical techniques/ theory developments that have come from this?
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    (Original post by Martin Hendry)
    The short answer is "yes": I think it's great to let students see that physics isn't just about topics that were worked out hundreds of years ago, by historical figures like Isaac Newton or Galileo, but is a field that's constantly changing and evolving as we discover new things about the universe and devise new applications that help us to improve the world around us.

    Your idea about a report seems a good one to me. My knowledge of the GCSE and A level syllabus is quite limited, as most Scottish Schools teach the Higher and Advanced Higher physics syllabus. I was involved in the redesign of the Higher and Advanced Higher physics courses recently, as part of the Scottish "Curriculum for Excellence" that's been introduced in schools, and the higher includes a new module (designed to involve about 20 hours of learning) entitled "Researching Physics" in which students are encouraged to find out about a cutting-edge topic in current physics research. There are also small sections on cosmology, astrophysics, particle physics, relativity and quantum physics as part of the overall higher and advanced higher syllabus. So far students seem to be responding very positively to this new material...
    Thank you so much for this That's very interesting to know!

    The reason I ask is that without a doubt, the consensus among many of my friends' schools and mine is that those small topics you mentioned are some of, if not the most popular. I really hope the English/Welsh exam boards adopt the idea of Researching Physics!
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    (Original post by C-rated)
    We can harness light energy, so is it possible to use gravitational waves as a source of energy?
    Really good question! Part of the reason why it's so hard to detect gravitational waves is also the reason why I'd say the answer to your question is probably no - at least for the foreseeable future.

    Gravitational waves can be thought of as ripples in spacetime - the result of a violent event like the collision of black holes shaking spacetime. We often use the analogy of a stretched sheet of rubber, like a trampoline, wobbling as you drop something heavy on to it. But in terms of this analogy, spacetime is really, really stiff! In other words you have to drop something incredibly heavy, and accelerate it at speeds close to the speed of light, to shake spacetime by a measurable amount. All of that means that to *harness* the energy produced when you shake spacetime is also extremely difficult, so we can't imagine at the moment any practical mechanism by which we could use gravitational waves to do work for us - i.e. as a viable source of energy.

    In physics it's a bit dangerous to say "never", however, and perhaps in a few centuries we'll have found a way to manipulate - and generate - gravitational waves. For the moment we'll just have to make do with being able to detect them...
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    (Original post by EnglishMuon)
    Thanks very much for the reply! Its nice to know that you focused on the maths side at points (although Im sure all your work is pretty maths focused anyway), this is definitely the root I would like to go Also, I've seen a fair few questions asking about the other 'real life' applications of this discovery, but are there any specific mathematical techniques/ theory developments that have come from this?
    Over the past decade there's been some very significant developments in the numerical simulation of black hole mergers - basically solving Einstein's equations for general relativity in the case of a very strong, and rapidly changing gravitational field. Those breakthroughs allowed us to model in detail the gravitational wave emission expected from such an event, and helped us to be able to interpret the measurements made by the LIGO detectors.

    There's also been a great deal of progress in data analysis methods relevant to studying gravitational wave sources - although much of that literature, known as Bayesian inference, has been developed more widely, and not just for studying gravitational wave sources. These Bayesian methods have very wide application beyond the physical sciences, and can be used to study huge datasets in, for example, the medical and biosciences.
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    (Original post by Martin Hendry)
    Over the past decade there's been some very significant developments in the numerical simulation of black hole mergers - basically solving Einstein's equations for general relativity in the case of a very strong, and rapidly changing gravitational field. Those breakthroughs allowed us to model in detail the gravitational wave emission expected from such an event, and helped us to be able to interpret the measurements made by the LIGO detectors.

    There's also been a great deal of progress in data analysis methods relevant to studying gravitational wave sources - although much of that literature, known as Bayesian inference, has been developed more widely, and not just for studying gravitational wave sources. These Bayesian methods have very wide application beyond the physical sciences, and can be used to study huge datasets in, for example, the medical and biosciences.
    Wow, Interesting!. Would you mind if I quote you for a piece of physics homework on general relativity? Thanks again, I appreciate the insight
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    (Original post by FrankES)
    Any other way we could use gravitational waves in everyday life?

    How often do you think gravitational waves could be detected?


    Is there any way to relate those gravitational waves with the movement of the celestial bodies that created them?

    Thanks, Mr. Hendry!

    As I've said in answer to another related question, we don't know if it will ever be possible to harness gravitational waves as a source of energy here on Earth, but the amount of energy released in the form of gravitational waves by an event like the merger of two black holes is really enormous so the potential if we *could* harness those energies is pretty mind-blowing. In the 2014 movie "Interstellar" (that was exec produced by Caltech physicist Kip Thorne, who was one of the speakers on the platform at our Feb news conference announcing the LIGO results) the director Christopher explores some of the possible consequences of being able to harness and manipulate gravitational fields. It's hard to know if what's explored in that movie could ever make the transition from science fiction to real science, but at least now by being able to study gravitational waves we might get some clues that could start us along that road....

    As to how often we will detect gravitational waves, our first detection announcement was based on our analysis of only about one month of data from our first science run. That run finished in January 2016 and we're still busy analysing the rest of the data, so watch this space (or should that be watch this spacetime?!) for updates on the results of that analysis coming soon...

    In the longer term, we will be upgrading the LIGO detectors to make them even more sensitive before they begin their second full science run later in 2016, so we expect many, many more detections of gravitational waves coming in the future.

    And for the event that we have reported already - GW150914 - we have estimated that a black hole merger like it happens somewhere in the universe every *15 minutes* - even though most of them are too far away or too faint for us to detect. Still, this means that the universe is awash with gravitational waves!

    And about your third question, generally we expect that we'll be able to relate the gravitational wave signals that we detect to the distance, direction on the sky, and motions of the objects that produced them. For GW150914, for example, we were able to work out that the signal was produced by a black hole merger where the two black holes were orbiting each other at more than half the speed of light when they merged. In the future we hope also to be able to associate the gravitational wave events that we observe with light emitted from the same sources. For other sorts of events, like for example the merger of two neutron stars, that accompanying light could also be very bright - producing something that we call a gamma ray burst.
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    (Original post by Life_peer)
    Greetings Prof. Hendry,

    following the recent experimental confirmation of gravitational waves (congratulations!), I've been wondering if it's theoretically possible—given our current knowledge—to alter the curvature of the space-time and by extension gravity without the usual means based on Newton's law of universal gravitation (e.g. centrifugal force or a massive object), i.e. using some form of energy.

    Note that the local effect that I have in mind would be as small as a single person or even smaller, so we could jump higher or explore planets much more massive than Earth, or effortlessly lift a bloody grand piano that needs to be moved through the window for a hefty price (I'm sure you can imagine the great potential of altering the space-time besides FTL travel).

    Thank you and good luck with your future endeavours!
    That's an intriguing question! I guess it's important to begin by saying that Newton's law - while a very useful approximation to describe gravity, particularly in a "weak" gravitational field like that of planet Earth - is superceded by Einstein's picture of gravity from General Relativity, and we find that Einstein's theory seems to provide an excellent description of the black hole merger event that we saw. So another way to phrase your question is whether it might be possible in the future to *generate* gravitational waves artificially, rather than simply measure them from naturally occurring phenomena.

    In a sense the answer is an emphatic "yes": even shaking your fist in the air technically does generate gravitational waves, but the problem is that these are fantastically weak, because your fist doesn't weigh the same as a star and you can't move it back and forth close to the speed of light! It's only such motions that can generate the sorts of gravitational wave amplitudes that we could hope to detect (and even then it took us a century to develop sensitive enough instruments to do it...)

    So for the moment we can't envisage being able to manipulate gravity in the way you describe - although (as I was saying in answer to another question) in the 2014 movie "Interstellar" exactly this sort of manipulation of gravitational fields is a major element of the plot, giving rise to wormholes that allow FTL travel and allowing the creation of vast colonies in outer space. Could that sort of science fiction ever make the transition to real science? I honestly don't know, but I certainly hope so - and perhaps being able to study gravitational waves will offer us some important clues.
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    (Original post by Aria Enoshima)
    What do you think is next to discover or look into (either you, or scientists in general)?
    Thanks for your question! Well for me there's lots more gravitational wave astronomy to do. Our first detection is equivalent for gravitational waves to Galileo taking his first look through an optical telescope 400 years ago - and look at what we've learned since then....

    For science more generally, there are so many things we *don't* know about how our universe works it's hard to narrow it down. Even just in astronomy, there are lots of fascinating unanswered questions that we might hope to answer soon: "what is dark matter and dark energy?" and "is there life elsewhere in the universe?" are probably my top two!
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    (Original post by EnglishMuon)
    Wow, Interesting!. Would you mind if I quote you for a piece of physics homework on general relativity? Thanks again, I appreciate the insight
    No problems, by all means do so!
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    (Original post by Martin Hendry)
    That's an intriguing question! I guess it's important to begin by saying that Newton's law - while a very useful approximation to describe gravity, particularly in a "weak" gravitational field like that of planet Earth - is superceded by Einstein's picture of gravity from General Relativity, and we find that Einstein's theory seems to provide an excellent description of the black hole merger event that we saw. So another way to phrase your question is whether it might be possible in the future to *generate* gravitational waves artificially, rather than simply measure them from naturally occurring phenomena.

    In a sense the answer is an emphatic "yes": even shaking your fist in the air technically does generate gravitational waves, but the problem is that these are fantastically weak, because your fist doesn't weigh the same as a star and you can't move it back and forth close to the speed of light! It's only such motions that can generate the sorts of gravitational wave amplitudes that we could hope to detect (and even then it took us a century to develop sensitive enough instruments to do it...)

    So for the moment we can't envisage being able to manipulate gravity in the way you describe - although (as I was saying in answer to another question) in the 2014 movie "Interstellar" exactly this sort of manipulation of gravitational fields is a major element of the plot, giving rise to wormholes that allow FTL travel and allowing the creation of vast colonies in outer space. Could that sort of science fiction ever make the transition to real science? I honestly don't know, but I certainly hope so - and perhaps being able to study gravitational waves will offer us some important clues.
    Many thanks for your answer, sir! I hope we'll both still be around to witness it.
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    What do you (personally) think the discovery of gravitational waves promises for us in the near future?
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    (Original post by Nuclear Ghost)
    What do you (personally) think the discovery of gravitational waves promises for us in the near future?
    Good question. Let me adapt the answer I gave to an earlier, similar, question.

    Partly I'm inclined to answer by saying "we don't know", since perhaps the most exciting prospect about opening up an entirely new way to look at the Universe is the strong possibility that we'll discover objects out there in the cosmos that we didn't even know existed before. However, even if we just restrict ourselves to phenomena that we already know about, but could use gravitational waves to study them more deeply, the possibilities are very exciting too.

    Firstly there's black holes themselves. The first direct detection of gravitational waves that we reported in February was a triple first, because it was also the first direct evidence that black holes exist, and the first evidence that they can exist in binary pairs. We had lots of circumstantial evidence for black holes before, and most scientists were convinced that they did exist, but now we can hope to study them in a lot more detail - exploring how and where they form, how massive they can be and whether or not their properties can be adequately described by Einstein's theory of general relativity. (The early signs, from this first event, are that they can be).

    Secondly there are neutron stars, the compact remnants of massive stars that have undergone a supernova explosion. We expect to be able to detect gravitational waves from the mergers of pairs of neutron stars, which we believe can give rise to a known phenomenon called a gamma ray burst - which emits an incredibly burst of high energy electromagnetic radiation (i.e. gamma ray light) to accompany the merger. Observing these events in gravitational waves too should help us to better understand the gamma ray bursts, and may offer ways in which we can use the GRBs to estimate how fast the universe is expanding - something we can do using "traditional" astronomy methods but it will be very interesting to be able to do it using gravitational wave observations too.

    Then there's the supernova explosions themselves. It's possible that gravitational waves are emitted during these explosions, and if we could detect those it would give us useful insights into how the explosions occur and what is the internal structure of neutron stars - a bit like seismologists can study the interior structure of the Earth from analysing the pattern of seismic waves in an earthquake.

    These are just some of the ways in which our understanding of some of the most violent events in the cosmos could be improved by the observation of gravitational waves.

    So in the near future we expect to be publishing within a few months (hopefully) the results from the remainder of our first science run. Then over the summer months the LIGO detectors will be upgraded further and the second science run will begin later in 2016. We expect that the Advanced Virgo detector in Italy will join that science run too - which should help significantly with determining the sky position of any sources that we detect, since observing them with a network of three detectors allows us to triangulate the position much better. A bit further down the line we'll have the prospect of two further detectors joining the network within a few years: first the KAGRA detector in Japan, which is currently under construction (and achieved a significant technological milestone in the past few days) and then early next decade the recently approved LIGO India detector. So there's lots to look forward to in our new field.
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    Congratulations on the discovery by you and the rest of the LIGO team, and thank you for doing this Q&A on TSR :woo: I have a broader question for you if that's okay, based on some discussions that have been going on on site recently:

    How important do you think philosophy has been in the development of science, and do you think philosophy still has any relevance for science today?
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    ChaoticButterfly lustawny

    I think you guys will be interested in this
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    What did you find where the big differences between undergrad, PhD and being a researcher? Any advice for aspiring researchers?
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    (Original post by Puddles the Monkey)
    Congratulations on the discovery by you and the rest of the LIGO team, and thank you for doing this Q&A on TSR :woo: I have a broader question for you if that's okay, based on some discussions that have been going on on site recently:

    How important do you think philosophy has been in the development of science, and do you think philosophy still has any relevance for science today?
    Hi there. Wow, thanks for a great question! I think that philosophy has been very important for the development of science - at least in the areas I've worked in - as I think it can play a crucial role in helping us to identify and refine the sorts of questions we can ask from the data we gather.

    There have been some controversies around this question in recent years - e.g. when Stephen Hawking weighed in on the question, and appeared to conclude that philosophers hadn't kept up well enough with the latest developments in physics in order to contribute to answering the big questions about why we are here etc. but I don't think I would go so far as Hawking does

    http://www.telegraph.co.uk/technolog...y-is-dead.html
 
 
 
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