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the strange world of the self-described ‘open-minded’ – part three, Apollo

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In 2009, a poll held by the United Kingdom’s Engineering & Technology magazine found that 25% of those surveyed did not believe that men landed on the Moon. Another poll gives that 25% of 18- to 25-year-olds surveyed were unsure that the landings happened. There are subcultures worldwide which advocate the belief that the Moon landings were faked. By 1977 the Hare Krishna magazine Back to Godhead called the landings a hoax, claiming that, since the Sun is 93,000,000 miles away, and “according to Hindu mythology the Moon is 800,000 miles farther away than that”, the Moon would be nearly 94,000,000 miles away; to travel that span in 91 hours would require a speed of more than a million miles per hour, “a patently impossible feat even by the scientists’ calculations.”

From ‘Moon landing conspiracy theories’ , Wikipedia

Time magazine cover, December 1968

Haha just for the record the Sun is nearly 400 times further from us than the Moon, but who’s counting? So now to the Apollo moon missions, and because I don’t want this exploration to extend to a fourth part, I’ll be necessarily but reluctantly brief. They began in 1961 and ended in 1975, and they included manned and unmanned space flights (none of them were womanned).

But… just one more general point. While we may treat it as inevitable that many people prefer to believe in hoaxes and gazillion-dollar deceptions, rather than accept facts that are as soundly evidence-based as their own odd existences, it seems to me a horrible offence in this case (as in many others), both to human ingenuity and to the enormous cost in terms, not only of labour spent but of lives lost. So we need to fight this offensive behaviour, and point people to the evidence, and not let them get away with their ignorance.

The Apollo program was conceived in 1960 during Eisenhower’s Presidency, well before Kennedy’s famous mission statement. It was given impetus by Soviet successes in space. It involved the largest commitment of financial and other resources in peacetime history. The first years of research, development and testing involved a number of launch vehicles, command modules and lunar modules, as well as four possible ‘mission modes’. The first of these modes was ‘direct ascent’, in which the spacecraft would be launched and operated as a single unit. Finally, after much analysis, debate and lobbying, the mode known as Lunar Orbit Rendezvous (LOR) was adopted. The early phases of the program were dogged by technical problems, developmental delays, personal clashes and political issues, including the Cuban missile crisis. Kennedy’s principal science advisor, Jerome Weisner, was solidly opposed to manned missions.

I can’t give a simple one-by-one account of the missions, as the early unmanned missions weren’t simply named Apollo 1, 2 etc. They were associated strongly with the Saturn launch vehicles, and the Apollo numbering system we now recognise was only established in April 1967. The Apollo 4 mission, for example, is also known as AS-501, and was the first unmanned test flight of the Saturn 5 launcher (later used for the Apollo 11 launch). Three Apollo/Saturn unmanned missions took place in 1966 using the Saturn 1B launch vehicle.

The manned missions had the most tragic of beginnings, as is well known. On January 27 1967 the three designated astronauts for the AS-204 spaceflight, which they themselves had renamed Apollo 1 to commemorate the first manned flight of the program, were asphyxiated when a fire broke out during a rehearsal test. No further attempt at a manned mission was made until October of 1968. In fact, the whole program was grounded after the accident for ‘review and redesign’ with an overall tightening of hazardous procedures. In early 1968, the Lunar Module was given its first unmanned flight (Apollo 5). The flight was delayed a number of times due to problems and inexperience in constructing such a module. The test run wasn’t entirely successful, but successful enough to clear the module for future manned flights. The following, final unmanned mission, Apollo 6, suffered numerous failures, but went largely unnoticed due to the assassination of Martin Luther King on the day of the launch. However, its problems helped NASA to apply fixes which improved the safety of all subsequent missions.

And so we get to the first successful manned mission, Apollo 7. Its aim was to test the Apollo CSM (Command & Service Module) in low Earth orbit, and it put American astronauts in space for the first time in almost two years. It was also the first of the three-man missions and the first to be broadcasted from within the spaceship. Things went very well in technical terms, a relief to the crew, who were only given this opportunity due to the deaths of the Apollo 1 astronauts. There were some minor tensions between the astronauts and ground staff, due to illness and some of the onboard conditions. They spent 11 days in orbit and space food, though on the improve, was far from ideal.

Apollo 8, launched only two months later in December, was a real breakthrough, a truly bold venture, as described in Earthrise, an excellent documentary of the mission made in 2005 (the astronauts were the first to witness Earthrise from the Moon). The aim, clearly, was to create a high-profile event designed to capture the world’s attention, and to eclipse the Soviets. As the documentary points out, the Soviets had stolen the limelight in the space race – ‘the first satellite, the first man in orbit, the first long duration flight, the first dual capsule flights, the first woman in space, the first space walk’. Not to mention the first landing of a human-built craft on the Moon itself.

One of the world’s most famous photos, Earthrise, taken by astronaut William Anders on Christmas Eve, 1968

The original aim of the mission was to test the complete spacecraft, including the lunar module, in Earth orbit, but when the lunar module was declared unready, a radical change of plan was devised, involving an orbit of the Moon without the lunar module. Apollo 8 orbited the Moon ten times at close quarters (110 kms above the surface) over a period of 20 hours. During the orbit they made a Christmas Eve telecast, the most watched program ever, up to that time. Do yourself a favour and watch the doco. The commentary of the astronaut’s wives are memorable, and put the moon hoaxers’ offensiveness in sharp relief.
By comparison to Apollo 8 the Apollo 9 mission (March ’69) was a modest affair, if that’s not too insulting. This time the complete spacecraft for a Moon landing was tested in low Earth orbit, and everything went off well, though space walking proved problematic, as it often had before for both American and Soviet astronauts, due to space sickness and other problems. With Apollo 10 (May ’69) the mission returned to the Moon in a full dress rehearsal of the Apollo 11 landing. The mission created some interesting records, including the fastest speed ever reached by a manned vehicle (39,900 kms/hour during the return flight from the Moon) and the greatest distance from home ever travelled by humans (due to the Moon’s elliptical orbit, and the fact that the USA was on the ‘far side of the Earth’ when the astronauts were on the far side of the Moon).

I’ll pass by the celebrated Apollo 11 mission, which I can hardly add anything to, and turn to the missions I know less – that’s to say almost nothing – about.

Apollo 12, launched in November 1969, was a highly successful mission, in spite of some hairy moments due to lightning strikes at launch. It was, inter alia, a successful exercise in precision targeting, as it landed a brief walk away from the Surveyor 3 probe, sent to the Moon two and a half years earlier. Parts of the probe were taken back to Earth.

The Apollo 13 mission has, for better or worse, come to be the second most famous of all the Apollo missions. It was the only aborted mission of those intended to land on the Moon. An oxygen tank exploded just over two days after launch in April 1970, and just before entry into the Moon’s gravitational sphere. This directly affected the Service Module, and it was decided to abort the landing. There were some well-documented hairy moments and heroics, but the crew managed to return safely. Mea culpa, I’ve not yet seen the movie!

Apollo 14, launched at the end of January 1971, also had its glitches but landed successfully. The astronauts collected quite a horde of moon rocks and did the longest moonwalk ever recorded. Alan Shepard, the mission commander, added his Moon visit to the accolade of being the first American in space ten years earlier. At 47, he’s the oldest man to have stepped on the Moon. The Apollo 15 mission was the first of the three ‘J missions’, involving a longer stay on the Moon. With each mission there were improvements in instrumentation and capability. The most well-known of these was the Lunar Roving Vehicle, first used on Apollo 15, but that mission also deployed a gamma-ray spectrometer, a mass spectrometer and a laser altimeter to study the Moon’s surface in detail from the command module. Apollo 16 was another successful mission, in which the geology of the Moon’s surface was the major focus. Almost 100kgs of rock were collected, and it was the first mission to visit the ‘lunar highlands’. The final mission, Apollo 17, was also the longest Moon stay, longest moonwalks in total, largest samples, and longest lunar orbit. And so the adventure ended, with high hopes for the future.

I’ve given an incredibly skimpy account, and I’ve mentioned very few names, but there’s a ton of material out there, particularly on the NASA site of course, and documentaries aplenty, many of them a powerful and stirring reminder of those heady days. Some 400,000 technicians, engineers, administrators and other service personnel worked on the Apollo missions, many of them working long hours, experiencing many frustrations, anxieties, and of course thrills. I have to say, as an internationalist by conviction, I’m happy to see that space exploration has become more of a collaborative affair in recent decades, and may that collaboration continue, defying the insularity and mindless nationalism we’ve been experiencing recently.

a beautiful image of the International Space Station, my favourite symbol of global cooperation

Finally, to the moon hoaxers and ‘skeptics’. What I noticed on researching this – I mean it really was obvious – was that in the comments to the various docos I watched on youtube, they had nothing to say about the science and seemed totally lacking in curiosity. It was all just parroted, and ‘arrogant’ denialism. The science buffs, on the other hand, were full of dizzy geekspeak on technical fixes, data analysis and potential for other missions, e.g. to Mars. In any case I’ve thoroughly enjoyed this little trip into the Apollo missions and the space race, in which I’ve learned a lot more than I’ve presented here.

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Written by stewart henderson

March 19, 2017 at 4:42 pm

the strange world of the self-described ‘open-minded’ – part one

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my copy - a stimulating and fun read, great fodder for closed-minded types, come moi

my copy – a stimulating and fun read, great fodder for closed-minded types, comme moi

I’ve just had my first ever conversation with someone who at least appears to be sceptical of the Apollo 11 moon landing of 1969 – and, I can only suppose, the five subsequent successful moon landings. Altogether, twelve men walked on the moon between 20 July 1969 and December 10 1972, when the crew members of Apollo 17 left the moon’s surface. Or so the story goes.

This conversation began when I said that perhaps the most exciting world event I’ve experienced was that first moon landing, watching Neil Armstrong possibly muffing the lines about one small step for a man, and marvelling that it could be televised. I was asked how I knew that it really happened. How could I be so sure?

Of course I had no immediate answer. Like any normal person, I have no immediate, or easy, answer to a billion questions that might be put to me. We take most things on trust, otherwise it would be a very very painstaking existence. I didn’t mention that, only a few months before, I’d read Phil Plait’s excellent book Bad Astronomy, subtitled Misconceptions and misuses revealed, from astrology to the moon landing ‘hoax’. Plait is a professional astronomer who maintains the Bad Astronomy blog and he’s much better equipped to handle issues astronomical than I am, but I suppose I could’ve made a fair fist of countering this person’s doubts if I hadn’t been so flabbergasted. As I said, I’d never actually met someone who doubted these events before. In any case I don’t think the person was in any mood to listen to me.

Only one reason for these doubts was offered. How could the lunar module have taken off from the moon’s surface? Of course I couldn’t answer, never having been an aeronautical engineer employed by NASA, or even a lay person nerdy enough to be up on such matters, but I did say that the moon’s minimal gravity would presumably make a take-off less problematic than, say, a rocket launch from Mother Earth, and this was readily agreed to. I should also add that the difficulties, whatever they might be, of relaunching the relatively lightweight lunar modules – don’t forget there were six of them – didn’t feature in Plait’s list of problems identified by moon landing skeptics which lead them to believe that the whole Apollo adventure was a grand hoax.

So, no further evidence was proffered in support of the hoax thesis. And let’s be quite clear, the claim, or suggestion, that the six moon landings didn’t occur, must of necessity be a suggestion that there was a grand hoax, a conspiracy to defraud the general public, one involving tens of thousands of individuals, all of whom have apparently maintained this fraud over the past 50 years. A fraud perpetrated by whom, exactly?

My conversation with my adversary was cut short by a third person, thankfully, but after the third person’s departure I was asked this question, or something like it: Are you prepared to be open-minded enough to entertain the possibility that the moon landing didn’t happen, or are you completely closed-minded on the issue?

Another way of putting this would be: Why aren’t you as open-minded as I am?

So it’s this question that I need to reflect on.

I’ve been reading science magazines on an almost daily basis for the past thirty-five years. Why?

But it didn’t start with science. When I was kid, I loved to read my parents’ encyclopaedias. I would mostly read history, learning all about the English kings and queens and the battles and intrigues, etc, but basically I would stop at any article that took my fancy – Louis Pasteur, Marie Curie, Isaac Newton as well as Hitler, Ivan the Terrible and Cardinal Richelieu. Again, why? I suppose it was curiosity. I wanted to know about stuff. And I don’t think it was a desire to show off my knowledge, or not entirely. I didn’t have anyone to show off to – though I’m sure I wished that I had. In any case, this hunger to find things out, to learn about my world – it can hardly be associated with closed-mindedness.

The point is, it’s not science that’s interesting, it’s the world. And the big questions. The question – How did I come to be who and where I am?  – quickly becomes – How did life itself come to be? – and that extends out to – How did matter come to be? The big bang doesn’t seem to explain it adequately, but that doesn’t lead me to imagine that scientists are trying to trick us. I understand, from a lifetime of reading, that the big bang theory is mathematically sound and rigorous, and I also know that I’m far from alone in doubting that the big bang explains life, the universe and everything. Astrophysicists, like other scientists, are a curious and sceptical lot and no ‘ultimate explanation’ is likely to satisfy them. The excitement of science is that it always raises more questions than answers, it’s the gift that keeps on giving, and we have human ingenuity to thank for that, as we’re the creators of science, the most amazing tool we’ve ever developed.

But let me return to open-mindedness and closed-mindedness. During the conversation described above, it was suggested that the USA simply didn’t have the technology to land people on the moon in the sixties. So, ok, I forgot this one: two reasons put forward – 1, the USA didn’t have the technological nous; 2, the modules couldn’t take off from the moon (later acknowledged to be not so much of an issue). I pretty well knew this first reason to be false. Of course I’ve read, over the years, about the Apollo missions, the rivalry with the USSR, the hero-worship of Yuri Gagarin and so forth. I’ve also absorbed, in my reading, much about spaceflight and scientific and technological development over the years. Of course, I’ve forgotten most of it, and that’s normal, because that’s how our brains work – something I’ve also read a lot about! Even the most brilliant scientists are unlikely to be knowledgeable outside their own often narrow fields, because neurons that fire together wire together, and it’s really hands-on work that gets those neurons firing.

But here’s an interesting point. I have in front of me the latest issue of Cosmos magazine, issue 75. I haven’t read it yet, but I will do. On my shelves are the previous 74 issues, each of which I’ve read, from cover to cover. I’ve also read more than a hundred issues of the excellent British mag, New Scientist. The first science mag I ever read was the monthly Scientific American, which I consumed with great eagerness for several years in the eighties, and I still buy their special issues sometimes. Again, the details of most of this reading are long forgotten, though of course I learned a great deal about scientific methods and the scientific mind-set. The interesting point, though, is this. In none of these magazines, and in none of the books, blogs and podcasts I’ve consumed in about forty years of interest in matters scientific, have I ever read the claim, put forward seriously, that the moon landings were faked. Never. I’m not counting of course, books like Bad Astronomy and podcasts like the magnificent Skeptics’ Guide to the Universe, in which such claims are comprehensively debunked.

The SGU podcast - a great source for exciting science developments, criticism of science reporting, and debunking of pseudo-science

The SGU podcast – a great source for exciting science developments, criticism of science reporting, and debunking of pseudo-science

Scientists are a skeptical and largely independent lot, no doubt about it, and I’ve stated many times that scepticism and curiosity are the twin pillars of all scientific enquiry. So the idea that scientists could be persuaded, or cowed into participating in a conspiracy (at whose instigation?) to hoodwink the public about these landings is – well let’s just call it mildly implausible.

But of course, it could explain the US government’s massive deficit. That’s it! All those billions spent on hush money to astronauts, engineers, technicians (or were they all just actors?), not to mention nosey reporters, science writers and assorted geeks – thank god fatty Frump is here to make America great again and lift the lid on this sordid scenario, like the great crusader against fake news that he is.

But for now let’s leave the conspiracy aspect of this matter aside, and return to the question of whether these moon landings could ever have occurred in the late sixties and early seventies. I have to say, when it was put to me, during this conversation, that the technology of the time wasn’t up to putting people on the moon, my immediate mental response was to turn this statement into a question. Was the technology of the time up to it? And this question then turns into a research project. In other words, let’s find out, let’s do the research. Yay! That way, we’ll learn lots of interesting things about aeronautics and rocket fuel and gravitational constraints and astronaut training etc, etc – only to forget most of it after a few years. Yet, with all due respect, I’m quite sure my ‘adversary’ in this matter would never consider engaging in such a research project. She would prefer to remain ‘open-minded’. And if you believe that the whole Apollo project was faked, why not believe that all that’s been written about it before and since has been faked too? Why believe that the Russians managed to get an astronaut into orbit in the early sixties? Why believe that the whole Sputnik enterprise was anything but complete fakery? Why believe anything that any scientist ever says? Such radical ‘skepticism’ eliminates the need to do any research on anything.

But I’m not so open-minded as that, so in my dogmatic and doctrinaire fashion I will do some – very limited – research on that very exciting early period in the history of space exploration. I’ll report on it next time.

Written by stewart henderson

February 25, 2017 at 12:34 pm

So why exactly is the sky blue? SfD tries to investigate

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Canto: Well, Karl Kruszelnicki is one of our best science popularisers as you know, and therefore a hero of ours, but I have to say his explanation of the blueness of our daily sky in his book 50 Shades of Grey  left me scratching my head…

Jacinta: Not dumbed-down enough for you? Do you think we could form a Science for Dummies collaboration to do a better job?

Canto: Well that would really be the blind leading the blind, but at least we’d inch closer to understanding if we put everything in our own words… and that’s what I’m always telling my students to do.

Jacinta: So let’s get down to it. The day-sky is blue (or appears blue to we humans?) because…?

Canto: Well the very brief explanation given by Dr Karl is that it’s about Rayleigh scattering. Named for a J W Strutt, aka Lord Rayleigh, who first worked it out.

Jacinta: So let’s just call it scattering. What’s scattering?

Canto: Or we might call it light scattering. Our atmosphere is full of particles, which interfere with the light coming to us from the sun. Now while these particles are all more or less invisible to the naked eye, they vary greatly in size, and they’re also set at quite large distances from each other, relative to their size. The idea, broadly, is that light hits us from the sun, and that’s white light, which as we know from prisms and rainbows is made up of different wavelengths of light, which we see, in the spectrum that’s visible to us, as Roy G Biv, red orange yellow green blue indigo violet, though there’s more of some wavelengths or colours than others. Red light, because it has a longer wavelength than blue towards the other end of the spectrum, tends to come straight through from the sun without hitting too many of those atmospheric particles, whereas blue light hits a lot more particles and bounces off, often at right angles, and kind of spreads throughout the sky, and that’s what we mean by scattering. The blue light, or photons, bounce around the sky from particle to particle before hitting us in the eye so to speak, and so we see blue light everywhere up there. Now, do you find that a convincing explanation?

Jacinta: Well, partly, though it raises a lot of questions.

Canto: Excellent. That’s science for you.

Jacinta: You say there are lots of particles in the sky. Does the size of the particle matter? I mean, I would assume that the light, or the photons, would be more likely to hit large particles than small ones, but that would depend on just how many large particles there are compared to small ones. Surely our atmosphere is full of molecular nitrogen and oxygen, mostly, and they’d be vastly more numerous than large dust particles. Does size matter? And you say that blue light, or blue photons, tend to hit these particles because of their shorter wavelengths. I don’t quite get that. Why would something with a longer wavelength be more likely to miss? I think of, say, long arrows and short arrows. I see no reason why a longer arrow would tend to miss the target particles – not that they’re aiming for them – while shorter arrows hit and bounce off. And what makes them bounce off anyway?

Canto: OMG what a smart kid you are. And I think I can add more to those questions, such as why do we see different wavelengths of light as colours anyway, and why do we talk sometimes of waves and sometimes of particles called photons? But let’s start with the question of whether size matters. All I can say here is that it certainly does, but a fuller explanation would be beyond my capabilities. For a start, the particles hit by light are not only variable by size but by shape, and so potentially infinite in variability. Selected geometries of particles – for example spherical ones – can yield solutions as to light scattering based on the equations of Maxwell, but that doesn’t help much with random dust and ice particles. Rayleigh scattering deals with particles much smaller than the light’s wavelength but many particles are larger than the wavelength, and don’t forget light is a bunch of different wavelengths, striking a bunch of different sized and shaped particles.

Jacinta: Sounds horribly complex, and yet we get this clear blue sky. Are you ready to give up now?

Canto: Just about, but let me tackle this bouncing off thing. Of course this happens all the time, it’s called reflection. You see your reflection in the mirror because mirrors are designed as highly reflective surfaces.

Jacinta: Highly bounced-off. So what would a highly unreflective surface look like?

Canto: Well that would be something that lets all the light through without reflection or distortion, like the best pane of glass or pair of specs. You see the sky as blue because all these particles are absorbing and reflecting light at particular wavelengths. That’s how you see all colours. As to why things happen this way, OMG I’m getting a headache. The psychologist Thalma Lobel highlights the complexity of it all this way:

A physicist would tell you that colour has to do with the wavelength and frequency of the beams of light reflecting and scattering off a surface. An ophthalmologist would tell you that colour has to do with the anatomy of the perceiving eye and brain, that colour does not exist without a cornea for light to enter and colour-sensitive retinal cones for the light-waves to stimulate. A neurologist might tell you that colour is the electro-chemical result of nervous impulses processed in the occipital lobe in the rear of the brain and translated into optical information…

Jacinta: And none of these perspectives would contradict the others, it would all fit into the coherence theory of truth…

Canto: Not truth so much as explanation, which approaches truth maybe but never gets there, but the above quote gives a glimpse of how complex this matter of light and colour really is…

Jacinta: And just on the physics, I’ve looked at a few explanations online, and they don’t satisfy me.

Canto: Okay, I’m going to end with another quote, which I’m hoping may give you a little more satisfaction. This is from Live Science.

The blueness of the sky is the result of a particular type of scattering called Rayleigh scattering, which refers to the selective scattering of light off of particles that are no bigger than one-tenth the wavelength of the light.

Importantly, Rayleigh scattering is heavily dependent on the wavelength of light, with lower wavelength light being scattered most. In the lower atmosphere, tiny oxygen and nitrogen molecules scatter short-wavelength light, such as blue and violet light, to a far greater degree than long-wavelength light, such as red and yellow. In fact, the scattering of 400-nanometer light (violet) is 9.4 times greater than the scattering of 700-nm light (red).

Though the atmospheric particles scatter violet more than blue (450-nm light), the sky appears blue, because our eyes are more sensitive to blue light and because some of the violet light is absorbed in the upper atmosphere.

Jacinta: Yeah so that partially answers some of my questions… ‘selective scattering’, there’s something that needs unpacking for a start…

Canto: Well, keep asking questions, smart ones as well as dumb ones…

Jacinta: Hey, there are no dumb questions. Especially from me. Remember this is supposed to be science for dummies, not science by dummies

Canto: Okay then. So maybe we should quit now, before we’re found out…

References:

‘Why is the sky blue?’, from 50 shades of grey matter, Karl Kruszelnicki, pp15-19

‘Blue skies smiling at me: why the sky is blue’, from Bad astronomy, Philip Plait, pp39-47

http://www.livescience.com/32511-why-is-the-sky-blue.html

http://spaceplace.nasa.gov/blue-sky/en/

https://en.wikipedia.org/wiki/Light_scattering_by_particles

Written by stewart henderson

December 15, 2016 at 4:35 am

Proxima b

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Quote of the day/week/month/post:

Better to have questions you can’t answer than answers you can’t question – Max Tegmark (and many others)

proxima_system

Jacinta: So while astrophysicists argue over the likelihood of life elsewhere in our tiny but massive universe, some are focusing on our nearest star neighbour. Some wobbling of the red dwarf known as Proxima Centauri has revealed, upon lengthy observation, that it has a closely orbiting planet, which considering the relative coolness of the star – way too dim to be seen with the naked eye – and the proximity of its satellite, is very much in the habitable zone. While it’s too early to say so much for the naysayers, the discovery of a planet in the Goldilocks zone of our nearest star in a galaxy of billions of possibilities must surely raise hopes and expectations of life abundant.

Canto: This closest possible exoplanet was only discovered in August this year, so we’re desperate to find out more about it. Being in the habzone is one thing, habitability is another. Obvious questions we have no current way of answering are: does it have an atmosphere? Any possibility of water? Is it tidally locked? And of course we’d love to know if we could launch some sort of robotic mission to our nearest star neighbour. Meanwhile is there any other way of gleaning more info from this tantalising object?

Jacinta: It’s not likely to be habitable though. Solar winds are estimated to be some 2000 times those experienced on Earth, though we can’t be too sure. Researchers are trying to work out the size of the planet…

Canto: How do they know about those solar winds?

Jacinta: Oooh, that’s a horribly good question. It’s due to the closeness of the orbit, where you would expect the solar winds to be much stronger, as they are in our solar system. It’s believed that Mercury’s magnetic field, which should be stronger than it’s been measured to be because of its heavy metallic core, is dampened massively by our solar wind. So basically they would’ve inferred Proxima Centauri’s wind by our own. As to how they came up with the figure of 2000 times that experienced on Earth, I’ve no idea, but strong solar winds make it hard to maintain an atmosphere, which is vital for life. You’ve also talked about tidal locking, which is a feature of close orbits, such as the Moon’s orbit of the Earth. So you’ll have a permanently hot day side and a permanently cool night side, and this can be problematic for the creation of an atmosphere, according to modelling.

Canto: Now, all of this sounds very negative, but basing exo-planetary activity on what’s been the case, as far as we can work it out, in our solar system, has been really problematic hasn’t it?

Jacinta: Definitely, that’s why we need to go beyond modelling, if we can, and collect some real data. So we’re looking to the James Webb Space Telescope (JWST), the very exciting successor to Hubble to be launched around November 2018, to garner more info, which it’ll be perfectly equipped to do.

Canto: If by some near-miraculous combination of circs there is an atmosphere on Proxima b, or a reasonable quantity of liquid water, that would help distribute the heat around the planet. With no atmosphere, the difference between day side and night side would be stark.

Jacinta: Exactly, and that’s what the JWST should be able to detect, as the best way to detect the atmosphere is to measure the planet’s infrared heat signature. If the JWST finds a decisive and fixed difference between the planet’s day and night sides, it’s a safe bet that no atmosphere is present. The JWST will be equipped to measure this IR signature on both sides of the planet, and if it doesn’t find that stark difference, that’ll be when we can start speculating about an atmosphere and its constituents.

Canto: Though of course they’ve already started with the speculation. But really, whatever they find – and I don’t expect that everything will line up for life – the fact that we’ve found an exoplanet well worth investigating on the nearest star outside our solar system, with billions of stars yet to be homed in on, one by one – doesn’t that say something to those who argue for the Fermi paradox – where are they? Okay, Fermi and Hart were talking about intelligent life, and that may well be orders of magnitude more difficult to develop than life itself, but I’m sure that Fermi would be unsettled in his skepticism, if he was alive today, by the vast numbers of exoplanets, in other words possibilities for life, we’re discovering now, with so many to come in the near future.

Jacinta: Yes, bliss in this time it is to be alive, but to be young, that would be very heaven!

 

 

References:

Cosmos issue 71, pp9-10

http://www.gizmodo.com.au/2016/08/how-well-get-our-first-big-clue-about-life-on-proxima-b/

en.wikipedia.org/wiki/Proxima_Centauri_b

 

 

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Written by stewart henderson

December 4, 2016 at 9:38 pm

How on earth? A chat about origins.

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one impression of our proto-sun and solar nebula

one impression of our proto-sun and solar nebula

Jacinta: I’d like to know how we got in this position.

Canto: What position?

Jacinta: Here, on Earth.

Canto: We?

Jacinta: Humans.

Canto: That’s a very long story, which I suspect nobody’s really qualified to tell. But maybe we can report on the best speculations. First, in order to understand how we got here we have to understand how the Earth got here.

Jacinta: And so on, infinitely regressing. So let’s just start with the Earth.

Canto: Needless to say we don’t know all the details and there are doubtless competing theories, and new data is being regularly uncovered, but it obviously has to do with how our entire solar system was formed.

Jacinta: I’ve heard that all the heavy metals like iron and whatnot are forged within stars, like when they go supernova, but our star hasn’t done that, all it seems to produce is light, yet Earth is full of heavy elements. I really don’t get it.

Canto: I recall reading years ago a theory that the Earth was formed from an accretion of planetesimals, little planets…

Jacinta: Planettes?

Canto: Yes, but how those little things came into being themselves I’m not sure.

Jacinta: Well we have lots of rocky bits and bobs called asteroids floating about in the solar system…

Canto: Yes, but not randomly. there’s a whole big asteroid belt between Jupiter and Mars, where they’re coralled, sort of.

Jacinta: But comets are different, they seem to have their individual eccentric orbits.

Canto: I suppose the point is that they also have heavy elements, and how were those elements formed?

Jacinta: Heat and pressure, I’m guessing, so things must’ve been hugely different in earlier times.

Canto: Well, this BBC site gives us some of the latest speculations. They reckon that the Earth probably formed from planetesimals, so that’s still the best hypothesis it seems, though it’s very light on details:

The Earth is thought to have been formed about 4.6 billion years ago by collisions in the giant disc-shaped cloud of material that also formed the Sun. Gravity slowly gathered this gas and dust together into clumps that became asteroids and small early planets called planetesimals.

Jacinta: Yes, that’s extremely vague. How do they know there was a disc-shaped cloud here? How can they investigate that far back?

Canto: Well don’t forget that looking out over huge distances means looking back in time.

Jacinta: Yes but a huge distance away isn’t here. Is it?

Canto: Well it might be here then.

Jacinta: Effing Einstein. But they’re also searching for extra data on the past, like checking out meteorites, which might contain material older than anything on Earth. Can they reliably date material that’s say, 5 billion years old? The Earth’s only about 4.5 billion years old, right?

Canto: I think 4.6 billion, give or take a few minutes. About a third of the age of the universe. And here’s the thing, we’ve dated all the meteorites and asteroids we can get to and they’re all round the same age, within a narrow range of a few hundred million years. So our date for the beginnings of the solar system is the oldest date for these floating and landing rocks, which is also our date for the Earth, about 4.6 billion.

Jacinta: So is our dating system completely accurate, and what by the way are carbonaceous chondrites?

Canto: Well, yes, radioactive decay provides a very accurate clock, and these meteorites have radioactive material in them, just as the core of our planet does. All the evidence so far suggests that things happened very quickly, in terms of accretion and formation of planets, once all this heavy and radioactive material was created. Carbonaceous chondrites are a type of meteorite. They’re amongst the oldest meteorites but relatively rare – they make up less than 5% of our meteorites. I mean the ones that land here. Why do you ask?

Jacinta: I’ve heard about them as being somehow important for research, and maybe dating?

Canto: Well there are different types of C chondrites as they’re called, and some of them, most interesting to us of course, are rich in organic compounds and water. This fact apparently shows that they haven’t been subjected to high temperatures, unlike for example the early Earth. But let me return to that BBC quote above. The theory goes that a supernova explosion, or maybe more than one, created all the heavy elements we have now – iron, carbon, silver, gold, uranium and all the rest, heat and pressure as you say, and these elements swirled around but were gravitationally attracted to a centre, which evolved into our sun. This was the spinning disc-shaped cloud mentioned above, known as the solar nebula.

Jacinta: Would you call that a theory, or a hypothesis, or wild desperate speculation?

Canto: I’d call it ‘the best we can do at the present moment’. But be patient, it’s a great time to be young in astronomy today. What we need is data, data, data, and we’re just starting to collect more data than we can rightly deal with on planets within and especially outside our solar system. Kepler’s just the beginning, girlie.

Jacinta: Je suis tout à fait d’accord, boyo. I think many of the astrophysicists are looking forward to having their cherished models swept aside by all the new telescopes and spectroscopes and what else and the data they spew back to Earth.

Canto: Uhh, well anyway let’s get back to our ‘best scenario for the moment’ scenario. So you have all this matter spinning around and the force of gravity causes accretion. It’s a messy scenario actually because everything’s moving at different velocities and angular momentums if that’s a thing, upwards, forwards, sideways down, and sometimes there’s accretion, sometimes fragmentation, but overall the movement is towards coalescence due to gravity. Particles grow to the size of monuments and then different sized planetesimals, fewer and bigger and farther between. And the smaller, gaseous elements are swept out by the solar wind into the great beyond, where they accrete into gas giants.

Jacinta: Right, but isn’t the data from Kepler and elsewhere already starting to play havoc with this scenario? Gas giants within spitting distance of their suns and the like?

Canto: Well, you need liquid to spit, but maybe you have a point, but I think it’s wise not to be too distracted by exoplanets and their systems at this stage. I think we need to find an internally coherent and consistent account of our own system.

Jacinta: What about the Juno probe, will that help?

Canto: Well I’m sure it will help us learn more about gas giants, but let’s just focus on the Earth now.

Jacinta: Okay, stay focussed.

Canto: These larger planetesimals became bigger gravitational attractors, each accumulating matter until we had four rocky planets in different, sufficiently distant orbits around their sun.

Jacinta: Oh yes, and what about the moons? Why didn’t they coalesce as neatly as all the other minor rocky bits?

Canto: Mmmm, well there’s nothing neat about all this, but mmmm…

Jacinta: How many moons are there?

Canto: For the inner planets? Only three, ours and two for Mars. So the question is, how come some of those rocks, or at least three, didn’t get stuck to the bigger rocks i.e. planets, via gravity, but instead started circling those planets, also due to gravity.

Jacinta: Yes, which might be the same question as why do the planets orbit around this massive gravitational attractor, the sun, instead of getting sucked into it, like what happens with those supermassive supersucking black holes?

Canto: Well first let me talk about our moon, because the most currently accepted theory about how our moon came into existence might surprise you.

Jacinta: It was a lot closer to the Earth at the beginning, wasn’t it? So it’s slowly spiralling away from us?

schematic of tial forces affecting moon's orbit and earth's rotation

schematic of tidal forces affecting moon’s orbit and earth’s rotation

Canto: Yes. Tidal forces. The moon’s tidally locked to the Earth, it’s the same face she shows us always, but let’s keep on track, it was formed in the very early days, when things were still very chaotic. A pretty large planetesimal, or planetoid, slammed into Earth, which was somewhat smaller then, and it stuck to it and coalesced with it – the Earth was pretty-well molten in those days – and a lot of debris was thrown out into space, but this debris didn’t quite escape Earth’s gravitational field, instead it coalesced to form our moon. This theory was first put forward a few decades ago, after moon rocks brought back from the Apollo missions were found to be younger than the oldest Earth rocks, and composed of much the same stuff, which came as a great surprise. But now the theory is well accepted, as it accounts for a number of other factors in the relationship between the two bodies.

the hypothesised Thea impact, which enlarged the Earth and created the Moon

the hypothesised Thea impact, which enlarged the Earth and created the Moon

Jacinta: Okay, so is that it on how the Earth was formed?

Canto: Well, yes, but the bigger question is your original one – how did we get here. And that means we have to look at how life got started here. Because we’re only up to about 4.5 billion years ago – with the moon being formed about 50 million years after the Earth. And at that point the Earth was like a sea of hot magma, hot from all the collisions on the surface, and hot from the radiation bursting out from its core. Hardly great conditions for life.

Jacinta: Well there might’ve been life, but not as we know it boyo.

Canto: I’m skeptical, but we’ll talk about that next time.

Some sources:

on the relation between moon and earth

formation of the moon

the solar nebula theory and its problems

 

 

Written by stewart henderson

July 19, 2016 at 8:45 am

exoplanets – an introduction of sorts

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future_habitable_exoplanets

Jacinta: So do you think we’ve hauled ourselves out of ignorance sufficiently to have a halfway stimulating discussion on exoplanets?

Canto: I think we should try, since it’s one of the most exciting and rapidly developing fields of inquiry at the moment.

Jacinta: And that’s saying something, what with microbiomes, homo naledi, nanobots and quantum biology…

Canto: Yes, enough to keep us chatting semi-ignorantly to the end of days. But let’s try to enlighten each other on exoplanets…

Jacinta: Extra solar planets, planets orbiting other stars, the first of which was discovered just over 20 years ago, and now, thanks largely to the Kepler Space Observatory, we’ve discovered thousands, and future missions, using TESS and the James Webb telescope, will uncover megatonnes more.

Canto: Yes, and you know, about the Kepler scope, l was blown away – this might be veering off topic a bit, but I was blown away in researching this by the fact that Kepler orbits the sun. I mean, I knew it was a space telescope, but I just assumed it was in orbit around earth, probably at a great distance to avoid interference from our atmosphere, but that we can position satellites in orbit around the sun, that really sort of stunned me, more I think than the exoplanet discoveries. Am I being naive?

Jacinta: No, not at all. Well, yes and no. Everything is stunning if you haven’t followed the incremental steps along the knowledge pathway. I mean, if you think, hey the sun’s a way away, and it’s really big and dangerous, best not go there, or something like that, you might be shocked, but think about it, we’ve been sending satellites around the earth for a long time now, and we know how to do it because we know about earth’s gravitational field and can calculate precisely how to harness it for satellite navigation. We’ve currently got a couple of thousand human-made satellites orbiting the earth and trying more or less successfully to avoid colliding with each other. So the sun also has a gravitational field and we’ve known the mathematics of gravitational fields since Newton. It’s the same formula for a star, a planet or whatever, all you need to know is its mass and its radius. And look at all the natural objects orbiting the sun without a problem. Can’t be that hard.

Canto: Okay… so how do we know the mass of the sun? Okay, forget it, let’s get back to exoplanets. What’s the big fuss here? Why are we so dead keen on exploring exoplanets?

Jacinta: Well the most obvious reason for the fuss is SETI, the search for extra-terrestrial intelligence, but to me it’s just satisfying a general curiosity, or you might say a many-faceted curiosity. And it’s all about us mostly. For example, is the solar system that we inhabit typical? We’ve mostly thought it was but we didn’t have anything to compare it with, but now we’re discovering all sorts of weird and wonderful planetary systems, and star systems, with gas giants like Jupiter orbiting incredibly close to their stars – it’s completely overturned our understanding of how planets exist and are formed, and that’s fantastically exciting.

Canto: So you say we discovered the first exoplanet about 20 years ago, and now we know about thousands – that’s a pretty huge expansion of our knowledge, so how come things have changed so fast? You’ve mentioned new technologies, new space probes, why have they suddenly become so successful?

Jacinta: Well I suppose it’s been a convergence of developments, but let’s go back to that first discovery, back in 1992. Two planets, the first ever discovered, were found orbiting a pulsar – a rapidly rotating neutron star. First discovery, first surprise. Pulsars with planets orbiting them, who would’ve thought? Pulsars are the remnants of supernovae – how could planets have survived that? But that first discovery was largely a consequence of our ability to measure, and the fact that pulsars pulse with extreme regularity. Any anomaly in the pulsing would be cause for further investigation, and that’s how the planets were found, and later independently confirmed. Now this was big news, in a field that was already becoming alert to the possibility of exoplanets, so you could say it opened the floodgates.

Canto: Really? But they didn’t discover any more for two or three years.

Jacinta: Well, okay it opened the gates but it didn’t start the flood, that really happened with the second discovery, the first discovery of a planet orbiting a main-sequence star like ours.

Canto: Main sequence? Please explain?

Jacinta: Well these are stars in a stable state, a state of balance or equilibrium, fusioning hydrogen – basically stars not too different from our own, within much the same range in terms of mass and luminosity. So 51 pegasus b was the first planet to be discovered by the radial velocity method, and radial velocity means the speed at which a star is moving towards or away from us. We can measure this, and whether the star is accelerating or decelerating in its movement, by means of the Doppler effect – waves bunch up when the object emitting them is moving towards us, they spread out when the object is receding from us, and the degree of the bunching or the spreading is a measure of their speed and whether it’s accelerating or decelerating. Now we can measure this with extreme accuracy using spectrometers, and that includes any perturbations in the star’s movement caused by orbiting bodies. That’s how 51 pegasus b was discovered.

Canto: So… how long have we had these spectrometers? Were they first developed in the nineties, or to the level of accuracy that they could detect these perturbations?

Jacinta: Well I don’t have a precise answer to that apart from the general observation that spectroscopes are getting better, and more carefully targeted for specific purposes. The French ELODIE spectrograph, for example, which was used to find 51 pegasus b, was first deployed in 1993 specifically for exoplanet searching, and since then it’s been replaced by another improved instrument, but of the same type. So it’s a kind of non-vicious circle, research leads to new technology which leads to new research and so on.

doppler1

Canto: So – we’ve gotten very good at measuring perturbations in a star’s regular movements…

Jacinta: Regular perturbations.

Canto: And we know somehow that these are caused by planets orbiting around them? How do we know this?

Jacinta: Well we will know from the size of the perturbation and its regularity that it’s an orbiting body, and we know it’s not a star because it’s not emitting any light (though it may be a low-mass star whose light isn’t easily separated from its parent star). We also know – we knew from the results that it was a massive planet orbiting very close to its star – a hot Jupiter as they  call it. And that was another surprise, but we’ve developed different techniques for discovering these things and we often use them to back each other up, to confirm or disconfirm previous findings. The ELODIE observation of 51 pegasus b was confirmed within a week of its announcement by another instrument, the Hamilton spectrograph in California. So there’s a lot of confirmation going on to weed out false positives.

Canto: So radial velocity is one technique, and obviously a very successful one as it got everyone excited about exoplanets, but what others are there, and which are the most successful and promising?

Jacinta: Well the radial velocity method was initially the most successful as you say, and hundreds of exoplanets have been discovered that way, but this method actually led to a kind of bias in the findings, because it was only able to detect perturbations above a certain level, so it was best for finding large planets close to their stars. But of course that was good too because we had never imagined that large gassy planets could exist so close to their stars. It’s opened up the whole field of planet formation. Then again, if the main aim is to find earth-like planets, this method is less effective than other methods. So let’s move on to the Kepler project. Kepler was launched in 2009, and since then you could say it has blitzed the field in terms of exoplanet detection. It uses transit photometry, which means that it measures the dimming of the light from a star when an orbiting planet passes between it and the Kepler detector.

Canto: So I get the idea of transit, as in the transit of venus, which we can see pretty clearly, but it’s amazing that we can detect transiting planets attached to stars so many light years away.

Jacinta: Well this is how we’ve expanded our world, from the infinitesimally small to the unfathomably large, from multiple billions of years to femtoseconds and beyond, through continuously refining technology, but let’s get back to Kepler. It orbits around the sun, and has collected data from around 145,000 main sequence stars in a fixed field of view – stars that are generally around the same distance from that dirty big black hole at the centre of our galaxy as our sun is.

Canto: Is that significant – that we’re focusing on stars in that range?

Jacinta: Apparently so, at least according to the Rare Earth Hypothesis, which puts all sorts of unimaginative limits on the likelihood of earth-like planets, IMHO, but no matter, it’s still a vast selection of stars, and we’ve reaped a grand harvest of planets from them – some 3000-odd, with over 1000 confirmed.

Canto: So… promising earth-like planets?

Jacinta: Yes, but I must point out that earth-like planets are difficult to detect. You see, Kepler was a kind of experiment, and we’ve learned from it, so that our next project will be much improved. For various reasons due to the photometric precision of the instrument, and inaccurate estimates of the variability of the stars in the field of view, we found that we needed to observe more transits to be sure we’d detected something. In other words we needed a longer mission than we’d planned for. And of course, Kepler has suffered serious technical problems, especially the failure of two reaction wheels, which have affected our ability to repoint the instrument. Having said that, we’ve been more than happy with its success.

Canto: Okay I just want to talk about these exoplanets. Can you summarise the most interesting discoveries?

Jacinta: Well, Kepler has certainly corrected the view we might’ve gotten from the earlier radial velocity method that large Jupiter-like planets are more common than smaller ones. We’ve had a number of reports from the Kepler group over the years, and over time they’ve adjusted downwards the average mass of the planets detected. And yes, they’ve discovered a number of planets in the ‘habzone’ as they call it. But that’s not all – only this year NASA confirmed the existence of five rocky planets, smaller than earth, orbiting a star that’s over 11 billion years old. I’m just trying to give you an idea of the explosion of findings, whether or not these planets contain life. And we’ve only just begun our hunt, and the refinement of instruments. It’s surely a great time to study astrophysics. It’s not just SETI, it’s about the incredible diversity of star systems, and working out where we fit into all this diversity.

ExoplanetDiscoveries-Histogram-20140226

Canto: Okay, I can see this an appropriately massive subject. Maybe we can revisit it from time to time?

Jacinta: Absolutely.

Some very useful sites:

http://www.planetary.org/explore/space-topics/exoplanets/

http://www.smithsonianmag.com/science-nature/how-do-astronomers-actually-find-exoplanets-180950105/?no-ist

https://en.wikipedia.org/wiki/Kepler_(spacecraft)

 

Written by stewart henderson

October 30, 2015 at 10:05 pm

why are our days getting longer?

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TIDESLOW

I’ve just finished reading a book by the Welsh biologist and science communicator Steve Jones entitled Coral; a pessimist in paradise, which covers a helluva lot of ground and makes me feel inadequate as most science writers do, but one of the many things he has taught me about – something I didn’t know that I didn’t know – is that the days are getting longer, in an inexorable process of rotational slowing. This fact, and the reasons behind it, were further confirmed for me today in an episode of an elegant little podcast out of the University of Houston, called The engines of our ingenuity. I just happened to be browsing through the science and scepticism podcasts on my TV, and I sampled a few curiously titled ones…

Let me backtrack a bit. I’m very very poor (from an affluent western perspective of course) but I received a HD TV from my neighbour recently as part of a complicated deal, and now I can watch free-to-air channels I didn’t have access to before, and what’s more I’ve managed to buy a device which I’m sure many people out there know all about, called an Apple TV, which is so cheap that even I can afford it without too much suffering (what’s a few days without food? it’ll probably extend my lifespan). So now I can explore an almost endless variety of podcasts, vodcasts and classic film noir movies on youtube. That reminds me, one of the podcasts I’ve listened to, the Brain Science Podcast, was all about brain fitness – at least the episode I tuned into was – and inter alia the interviewee informed us that just about the worst thing for the brain was sitting around all day watching TV – Apple or no Apple, presumably…

Anyway I listened to this informative and also charmingly poetic three-minute episode of The engines of our ingenuity, entitled ‘How far the moon?’, narrated and presumably written by Dr John Lienhard. So I’ll share the info, if not the poetry, here.

Our earth spins at a pretty well constant rate because of the forces that set it in motion in the first place and because of Newton’s first law of motion which, put simply, states that an object will stay in the same state (resting or in motion) unless an external force acts on it. A ball spinning in the air will slow down because of air friction, but the earth is spinning in a vacuum, essentially – there’s nothing to slow it down.

Well, not quite. The earth is slowing down, and all in accordance with Newtonian physics. And it’s all due to the moon. Each day is about a twelfth of a second longer than it was when the Egyptians built the pyramids. Doesn’t sound that much, but 4000 years is a mere blip in geological and cosmological time. The moon drags at the earth gravitationally, creating high tides and low tides at a regular rate, and slowing our rate of rotation. But our earth has a much greater influence on the moon than vice versa, the moon having only an eightieth of earth’s mass. This gravitational effect slowed down the moon’s spin until it was in synch with the earth, and locked into the earth’s movement like a dancer being swung around by its partner. And so the moon faces us always. The slowing down of the earth due to the moon’s influence had the effect of loosening the embrace – the moon is slowly moving away from us. Just as a spinning dancer or skater extends her arms out to slow down or pulls her limbs in to speed up.  The moon moves away from us so that our combined rotational inertia remains constant. The distance between earth and moon, and the speed at which the moon moves away from us, is being measured thanks to an instrument, placed on the moon by Apollo astronauts, which reflects laser beams from earth. Through measuring the time taken for the beam to return, we know that the moon is moving away from us at a little under 4 cms a year. Back in the dim distant past, days lasted only 12 hours, and the moon was half of today’s distance from us. This has affected the shape of the earth, which is gradually becoming more spherical. The earth’s diameter is at its greatest at the equator and at its smallest at the poles, because of centrifugal forces operating against the force of gravity…

Okay, let me get clearer on this, with the help of this source, among others. Isaac Newton accepted the mathematics and the accuracy of Kepler’s laws of planetary motion, but the great unanswered question was why planets – and moons – traced out these orbits. Newton’s own first law stated that an object will continue in its trajectory (that is, in a straight line) or in its resting state, unless some external force acted upon it to speed it up or slow it down. This state is called a state of inertia. Clearly planets and moons were being acted upon by some force, which could only be exerted by the object being orbited. This force might be called a centripetal force, though that doesn’t explain it in this case. If you swing a stone around on the end of a string, you apply a force to the stone to keep it going, but the string, and your hand holding the string, exerts a force on the string to keep it ‘in orbit’. Its motion will be circular, providing you keep your hand still, because the length of the string is constant. But there’s nothing obvious attaching the moon to the earth. Newton pondered this for some time, until one day the apple dropped.

I’m thinking that, if the moon is moving away from us, its orbit can’t be entirely circular, it must be spiralling outwards, ever so slightly. In any case, the moon pulls the earth out of shape, and that is due to a centrifugal force that balances the centripetal force exerted by the earth on the moon. The moon is moving away due to a reduction in both these forces, and a slowing of the earth’s rotation, and hence of the moon’s orbit.

But sadly, it gets more complicated than that! This is the Newtonian explanation of how these forces operate, but it doesn’t really answer the why question. I’m not going to go deeply into that here – as if I could – but I’ll end with a quote from an astronomer’s explanation, not so much about the earth’s slowing, but about the moon’s behaviour, in terms of Newtonian and then Einsteinian physics:

First case: – Why does the Moon orbit the Earth? It just does. And you can understand how it does by analyzing the forces on the Moon caused by its orbit and finding the forces pushing in and out are equal.

Second case: – Why does the Moon orbit the Earth? Because the Earth distorts spacetime in the vicinity of the Moon, and causes it to orbit the Earth the way it does and the balance of forces to come out the way it does.

So why do massive objects distort space-time? Apparently they just do?

Written by stewart henderson

September 28, 2013 at 8:25 am