Once again, Wikipedia needs your help . If you’ve ever used this fabulous resource (it’s a free, online encyclopedia covering everything you could possibly think of!) then consider making a donation and supporting their work - I know I use them almost daily!
An Inquiring Mind recently posted about the infamous Monty Hall problem. You might have heard of it - there are three doors: behind two are goats and behind one is a car. After you choose a door, the host opens a different door to reveal a goat (he knows what’s behind each door.) Should you then switch, or stay the same? It’s a very famous problem and although being very simple, both in statement and solution, it’s incredibly hard to come to terms with and has been studied by a lot of people. From my own personal experience, quite a few times I’ve mentioned that I do physics and maths and someone’s said to me: “Really? Hey, there’s this problem I heard recently. Imagine you had three doors, and behind two of them are goats…”
Tha answer is you should always switch, as it will double your chances of winning! If you find it counterintuitive, you’re not alone! What’s so amazing about this problem is that no-one believes it straight out - controversy and arguments always ensue, and even some mathematicians refused to believe it after a reporter published a column on it:
One [response] was from Robert Sachs, a professor of mathematics at George Mason University in Fairfax, Va. who said “As a professional mathematician, I’m very concerned with the general public’s lack of mathematical skills. Please help by confessing your error and, in the future, being more careful.”
However a week later and Dr. Sachs wrote her another letter telling her that “after removing my foot from my mouth I’m now eating humble pie. I vowed as penance to answer all the people who wrote to castigate me. It’s been an intense professional embarrassment.”
The key difficulty is that probability is often counter-intuitive. In particular, probabilities can be skewed by extra knowledge, which in this case comes from The websites I’ve linked above (paritcularly Wikipedia) explain it better than I can, but this one passage I found very useful:
It may be easier for the reader to appreciate the result by considering a hundred doors instead of just three. In this case there are 99 doors with goats behind them and 1 door with a prize. The contestant picks a door; 99 out of 100 times the contestant will pick a door with a goat. Monty then opens 98 of the other doors revealing 98 goats and offers the contestant the chance to switch to the other unopened door. On 99 out of 100 occasions the door the contestant can switch to will contain the prize as 99 out of 100 times the contestant first picked a door with a goat. At this point a rational contestant should always switch.
Personally, I love problems like this - they really bring to light the most important concepts in mathematics, and (as illustrated some of the responses that reporter received!) can really capture the attention of both mathematicians and the general public. Anything that gets people discussing mathematics has got to be good! If you do decide to tell your family and friends about it, though, you better be ready for some heated discussion and try and mater a really good explanation - because they’re going to fight it! Have fun!
For those of you who just joined us, I live in Australia and if there’s one thing we’ve got a lot of, it’s sunshine (yes, even more than kangaroos!) Therefore, it really makes sense for us to be looking towards solar energy to supply our electricity. Here at UQ, we have groups working on new, innovative innovative solar cells, made out of plastic or even melanin, the skin pigment. Hopefully, these will have higher efficiencies than existing technology, making solar energy more cost effective.
But that’s not the only option. Australia is planning to build a giant one-kilometre high Solar Tower that will generate as much power as a small nuclear reactor, but completely renewable and with no waste. A bit like the Parkes Observatory, it will be in the middle of a sheep paddock, and will become the tallest building in the world. It works by heating air in the base which rises, reaching speeds of 50km/hr and turning a turbine. Solar cells store energy during the day so the tower can run 24 hours.
Particularly after seeing the talks on global warming at the recent AIP Congress, I’m amazed (and more than a little scared) at how little governments around the world are doing to explore new energy technologies. It’s great to see Australia taking steps forward, even if the government has so far only offered “support” with no dollars. Apparently, the company involved also has a deal with China, so with any luck these towers will prove to be at least a partial solution to the world’s energy needs. Also, by becoming the tallest building in the world and hopefully a bit of a landmark (or something!) it might promote this and other renewable technologies to other governments and businesses. And, imagine if we could do a Giant Drop off one of those!
As a follow up to my previous post on autistic savants, I mentioned in that article that savants can often perform incredible calendar feats. My mum, a psychologist, used to work with a boy who could, given any date, tell you what day of the week it was. He explained it with a combination of intuition and mathematics (”I knew that mum’s birthday was on a Wednesday last year, and so 8 years before that it would have been a Monday, so September 20th must have been a Friday.” (I completely made up those days…))
I got interested in this, and found that there are a number of ways to do it mathematically while only having to memorise a few simple numbers. Lewis Caroll (of Alice in Wonderland fame) worked out one method, which is what I use - it’s very algorithmic, and can be done for any date (I use a slight variation, which I might post at a later date). There’s also the Doomsday method, which notes that 4/4, 6/6, 8/8, 10/10, 12/12, 7/11, 11/7, 9/5 and 5/9 always fall on the same day each year (bizarre, isn’t it?!) Lots of variations can be found through Google (if you search for the right thing!) I never really practised much, but in my prime I could tell you the day for any date in the 1900’s in about 10-15 seconds, using Lewis Caroll’s method. Not bad, but not quite up to the level of a savant. Have a go, and see how quickly you can do it!
It makes me wonder what connection a savant’s abilities has with “intuition”, where you can predict an answer without consciously being aware of the process you used to obtain it. This can be very valuable in physics, as well as many other areas of life, as it helps to focus your research direction and give some idea of where you should be aiming for. Could we learn to make even intuition more quantitative, or is that a contradiction of terms?
Feeling bored? Have a go of this simple quiz, and show everyone how smart you are. Important note: You have limited time to complete each question, so keep moving! I’ve seen ones like this before, but I have to say - it’s very clever. Good practise for everyone needing to improve their lateral thinking abilities! It also stresses how one should read the question first, and not to make unjustified assumptions…good advice for anyone studying physics!
I won’t tell you how well I did, or otherwise…
Slashdot is reporting on a fascinating article in the Guardian about an autistic savant who is able to explain his unique abilities. Autism is any of a spectrum of disorders - the symptoms and their degrees can vary greatly from person to person. One unusual component is that some people with autism, while having below-average abilities in some areas, have incredible mental abilities in others, such as mathematics, music or art. From the article:
Autistic savants have displayed a wide range of talents, from reciting all nine volumes of Grove’s Dictionary Of Music to measuring exact distances with the naked eye. The blind American savant Leslie Lemke played Tchaikovsky’s Piano Concerto No1, after he heard it for the first time, and he never had so much as a piano lesson. And the British savant Stephen Wiltshire was able to draw a highly accurate map of the London skyline from memory after a single helicopter trip over the city.
The man in the article, Daniel Tammet, can speak 7 languages, including one he designed himself, and perform calculations faster than a calculator. What’s of interest to researchers is that most savants are unable to explain exactly how they’re able to perform their calculations so quickly. Tammet, however, explains that he sees numbers as shapes, sounds and textures, and when he multiplies two numbers, their shapes merge and change into a new shape - which is the answer! I guess the hope is that by studying his techniques, we might learn ways to improve our own thinking, or even better understand how the brain functions.
Great story on Wired about a litterbug who finally gets their come-uppance:
Sweet Justice
A San Francisco man learned the hard way that littering — especially burning objects — is not a good idea. Jonathan Fish was driving across the Bay Bridge on Thursday when he tossed his cigarette out the window. But the cigarette blew back into his $30,000 Ford Expedition, igniting the back seat and filling the SUV with smoke. Fish pulled over and leaped from the flaming vehicle, which kept rolling and crashed into a guardrail. “It was in flames by the time he got out,” said CHP Officer Shawn Chase. “He had some of his hair singed on the back of his head. (The car) burned down to the frame.” Fish likely faces a misdemeanor charge for littering, which carries a fine of up to $1,000.I really don’t like smoking, but if people are going to do it then it jolly well better not affect anyone else - either through passive smoking or having to put up with cigarette butts everywhere. And this guy was driving a gas-guzzling SUV, so it’s hard to feel too much sympathy for him. That said, though, I hope he had insurance!
I’ve had two examples recently where basic maths has come in rather handy, and strangely (or not) both were to do with Telstra, which is the Australian telecommunications company and generally all-round not-such-nice guys. The first, and somewhat mundane, example is a new search service - ring the operator, ask for what you need and they find it and connect it for you. The advertised rates are “20 cent connection fee, plus four cents per second with the operator”. Now, at first glance this seems quite reasonable - until you perform some simple multiplication and realise that it’s 20 cents plus $2.40 a minute! That’s comparable with “psychic hotline” rates - for a search service?!
The next was almost straight out of a high school exam. I rang Telstra to see if there was a cheaper plan for my new home phone, and the woman I spoke to said “Wellllll, there is a plan that’s $9 cheaper a month, but the calls are 30c instead of 20c. So if you make more than a call a day, you’re better to stay on your current plan.” Hang on! I jotted down two simultaneous equations, and when I worked out how many calls I’d have to make for the expensive plan to be worthwhile it was about 90, or 3 calls a day! I posed this to my “customer service assistant”, and she proceeded to argue it with me! Now, while she might not be able to do maths on the fly, she represents Telstra and is selling these plans - surely one could expect her to know the difference between the two and when to offer which?! Even when I finally wen thtrough the maths with her (10c extra a call, I’d need ninety calls to add up to $9) she refused to believe me (though I admit, maths over the phone is tough!), and insisted if I made one call a day I’d be better off paying them lots more money. Hmmm. In the end I gave up arguing with her, and said “Put. Me. On. The. Cheaper. Plan.” and she finally agreed. But what a lot of effort!
A final example, which doesn’t apply to me but is still of issue, is broadband suppliers like Telstra which offer “cheap” broadband, say $30/month for 200mb of download. At first glance this seems like a good deal, until you realise that 200mb is probably enough to check your email and read the news, and not much else - certainly not their streaming video and music downloads that they advertise so boldly! And so here’s the catch - they charge, say, 5c per megabyte for your extra downloads - that’s $50/gigabyte! Originally, they could do this indefinitely and charge the careless user (i.e., parents with kids) hundreds of dollars, but the Australian telecommunications regulator stepped in and put a stop to that. Now, it’s capped at say $70, after which they drop your speed back to early dialup speeds. On broadband, it’s ridiculously easy to download that much, and you’d be much better off going to a $50 plan straight up with a cheaper supplier, but this time they want you on the cheaper plan!
So the point of all this is that I’ve been studying maths for years and I’m good at thinking on my feet so was able to argue for the best deal for me. But what about your average person who really didn’t like simultaneous equations? Telstra, and so many other businesses, are relying on your ignorance to support their business model. And it’s not just maths - think about people selling magnetic therapy pillows (no scientific evidence anywhere from anyone for anything to do with magnetic healing) or the various get-rich-quick pyramid schemes, or even just trying to get a realistic picture of the pros and cons of genetically modified foods. And I think this is why it’s so important for people to be aware of science (and maths) - you don’t have to be able to do research, but just be able to sift the wheat from the chaff. Hey, it might even save you money!
Apparently, dogs are getting addicted to cane toad poison - they lick the toad to get just enough of the poison to make them high, then “they get a smile on their face and look like they are going to wander off into the sunset.” So next time Rover is looking awfully happy about himself it might not just be that the little rat stole your dinner off the table…
At the University of Queensland, where I’m a PhD student, with Jenny Riesz I run the Physics Demo Troupe, a group of performers who do physics shows and workshops for schools, community groups and the general public. Made up mainly of undergraduate students, we train to perform shows that not only teach important physics, but do so in a fun and entertaining fashion - if you’ve ever been to a children’s pantomime, there’s a little of that in our shows 
To date, we’ve been to several dozen schools and seen thousands of students, but have also performed for more interesting groups, like a sales conference for Hastings Deering - a machine and tractor company! We talked about the physics of optical fibres, lasers, mechanics and forces - the physics which underpins much of what they sell.
It’s immense fun, and I’ve personally learned a lot of really cool physics from playing with these demos (and did I mention it’s fun?). Playing with liquid nitrogen, channeling a million volts of lightening through your body…what more could you want from life? If you’d like to know more, you should check out our brand new website, which is at http://www.demotroupe.org. You can see some of the demos that we perform, and there are lots of photos of us in action (including some bad ones of yours truly torturing a balloon animal…) And quick plug, if you’re in Queensland (Australia!) and you’d like us to perform for your school or other function, just drop me a line! We guarantee it’ll be a blast!
For the longest time, I have wondered why you get a “whirlpool” effect when you stir a cup of tea, coffee or whatever you enjoy best. You know - you get it moving with a spoon, and when you take the spoon out, the surface of the water is tilted in towards the centre. As it slows down, the angle of tilt gets narrower until finally your drink is flat and calm again. Though I’ve never sat down and really worked on it, I’ve thought about it several times and never come to a satisfactory conclusion - until I read this site, and their cool “Water Spinner” demo.
The basic idea is that if the whole drink is spinning at the same rate (say, two revolutions per second) then the outside of the coffee must be moving faster than the inside (at the edge of the cup, the drink must travel a much longer distance than the stuff right near the centre, in the time of one full revolution.) But to spin, you need a centripetal force - the force which holds you in the circle and prevents you from flying away. For example, if you’re spinning a ball on the end of a rope, the rope provides the force to keep the ball in the circle. If the rope breaks, the ball flies away.
In the case of the coffee cup, the force comes from gravity and the tilt of the water - the greater the tilt, the stronger the force pulling the coffee into the centre (technically, we’re talking about the horizontal component of the bouyancy force.)
It’s quite easy to show, then, that the surface of the coffee must form a parabola - and would be a good excercise for a first year physics student!
I, for one, feel like a part of me has been completed, and I’ll think I’ll celebrate by booking a couple of tickets to The Producers which is a musical coming to Brisbane in a few weeks!
I’m still on the topic of wayout theories. This time, it’s an article by Wired on immortality, specifically the claims by a famous inventor Ray Kurzweil that humans will be immortal in 20 years through the use of nanotechnology, genetic engineering and a strict health regime. Already, every day he “ingests 250 supplements, eight to 10 glasses of alkaline water and 10 cups of green tea. He also periodically tracks 40 to 50 fitness indicators.” All this, to keep him alive long enough to reach the next technological revolution. He’s not a biologist or anything, so it’s all just opinion, and some people think he’s a quack. But, even if not in 20 years, I could easily believe that technology will advance our lifespans, if not to the point of immortality.
But is this something we want to do? Kurz says “Death is a tragedy, a process of suffering that rids the world of its most tested, experienced members - people whose contributions to science and the arts could only multiply with agelessness.” But if your boss will never retire, what chance to you have of promotion to the top job? What would happen to the stock market? The oldest and richest would never pass on their money and assets, Bill Gates will always, for better or worse, rule Microsoft, and do you want the same politicians running year after year? On the one hand, with all that time we may make huge leaps in technology, art, music. But on the other, new talent might have trouble fitting into an already crowded market - would innovation be stifled?
And none of this takes into account the huge strain an ever increasing population would put on our planet. Colonisation of other worlds would have to become a reality very quickly, or extreme birth control would be needed, with just enough to balance accidental deaths. And who decides who gets to have children?
As the article says,
Immortality would leave little standing in current society, in which the inevitability of death is foundational to everything from religion to retirement planning. The planet’s natural resources would be greatly stressed, and the social order shaken.
So, I leave you with two Questions of Scruples - feel free to comment with your answer and thoughts! First, by a completely random accident, tomorrow you discover a drug that would render a person immortal, never to age, never to get sick. It would be extremely cheap and easy to mass produce. You think it highly unlikely that anyone would stumble across this drug again. Do you distribute the drug, or do you pretend it never happened? Or something else?
Second, a genie appears to you tomorrow and offers you immortality, never to age (you can choose what age you want to remain at), never to get sick or hurt, and unable to die, even if you wanted to. You are the only person to be offered this deal. Would you accept? What if it was for only 1000 years? 200 years? What if you could choose when you wanted to die?
Technology is always advancing, and no matter how much like science fiction something might sound, you never know what’s around the corner…
Well, speaking of controversial theories and trying to identify cranks, Slashdot had a post about seeing into the future using random number generators, an accidental byproduct of another experiment. Called the Global Consciousness Project, it involves a large number (60+) of random number generators at different locations around the world which are monitored for any unusual activity (i.e., producing numbers which don’t look random.) The claim is that when a major global event happens, such as September 11 or the recent tsunami, they see strange behaviour from the generators. Their theory to explain this is everyone in the world is connected in a “global consciousness”, and when we all feel strongly enough about something our energies affect the generators. What’s more, they claim that in several instances (such as September 11 and the tsunami) they saw strange behaviour up to 24 hours beforehand - which effectively means that they’re predicting the future.
So, the question you have to ask yourself is, do you believe it? Supposedly, earlier studies showed that even individuals concentrating hard enough could modify the results, demonstrating some sort of psychic powers - but just how significant was this? Did they concentrate for an hour and then see a blip in the graph for two seconds? Remember, we are talking about random numbers. You expect that sooner or later they’ll do something strange.
The correlations between machines in different locations is harder to explain, but even that might be related to sunspots, seismic activity, or who knows what other external effects that might affect their machines. And most importantly, they don’t claim to be able to predict anything - only in hindsight can they say that a peak in strange activity corresponded to a warning about the tsunami. This is basically the problem with any predictions (e.g., Nostradamus): it’s always easy in hindsight to find things that match up. After all, there’s always something going on in the world - Iraq is in constant conflict, famous people die, there are mudslides, earthquakes or even elections.
Take for example their supposed 24 hour ahead prediction of the tsunami. If the activity had come 24 hours later, they could have claimed it was a direct response to the tsunami. 48 hours later, it would have been the emotional response of the world as they heard the news. 24 hours earlier, and it could have been an even better warning. A month later, and it could have reflected the grief people felt at remembering the disaster. And further on, well, it might have corresponded to the recent elections in Iraq, right? See the problem?
Now, I’m not saying that this work is wrong - it’s hosted at Princeton, and apparently includes a number of respected researchers worldwide. I would love nothing more than proof that there really is something special going on out there. And so, to my original question: Are they cranks, or revolutionaries? I leave you with a quote from physicist and Nobel prize winner Niels Bohr (also (wrongly) attributed to Yogi Berra, a baseball player): “Predictions are hard to make; especially of the future.”
When I was at the AIP congress last week, there were a number of advertising booths around, selling the finest mirrors that money can buy, ultra stable lasers, and books such as the Journal of a Really Small Area of Physics that no-one currently reads. Most of it was completely irrelevant to me - after all, I’m a theoretician and I’m happy with my pen, paper, laptop and latest edition of Maple. One booth, however, caught my eye - awash with signs like “A public viewpoint on science”, “One particle, one force” (I kept thinking “One force to rule them all,” etc) and, alarm bells ringing in my head, “Why the Scwarzschild metric is wrong” (the part of general relativity which describes black holes). Uh oh.
Yep, you guessed it - turns out this guy is a crank, someone who payed to have a stall where he could tell his theories to the scientific community. The catch is, his theories were either naive, nonsensical or just downright weird, and it was clear why no journal had yet published his work. I honestly have to say I felt sorry for him - he was a nice enough guy, if somewhat pushy - because everyone there knew he was an crank, and either just pacified him when they spoke to him, or tried to argue with him to no avail. (My friend B also has some thoughts on him.)
But it made me start to think - how do you decide whether someone is a crank? My thoughts, and examples of cranks, fringe dwellers and revolutionaries follow…
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I’ve always been passionate about astronomy - I had a small telescope when I was young (e.g., 6 or 7) which got upgraded one Christmas to a fun Tasco telescope. My absolute favourite moment was the first time I saw the rings of Saturn, out on my driveway with my torch and red cellophane (to protect my night vision) and a printout from Skyglobe, a home planetarium program, so I knew exactly where to look. Admittedly, it didn’t look quite like this, but I could make out a small, slightly elongated globe with two holes on either side for the gap between the planet and the rings. Very cool!
I happened to come across a few neat astronomy links in the last few days. First up are some awesome 360 degree panoramas of the moon, taken by astronauts on the Apollo missions. It really is incredible being able to look around as if you were standing there on the moon, while listening to Neil Armstrong as he takes his first step. There’s a kind of uncanny atmosphere to the pictures (actually, there’s not atmosphere at all! Boom boom!) where things don’t look quite right. The best example of this I’ve seen is a movie taken by Apollo 16 - check out the boulder in the background, that looks about 3 or 4 metres (that’s 12 foot for the Americans) high, then watch the movie until they walk over to it about 3/4 of the way through. Without atmosphere, distant objects aren’t blurred or obscured by the air, which is one way that we can estimate their distance and hence their actual size. On the moon, distant objects look the same as close ones, and we sometimes can’t tell whether we’re looking at a nearby boulder or a far away mountain! (Thanks to Phil Plait for this info.)
Another neat program I’ve come across is Celestia, a free open-source space exploration program that lets you travel pretty much anywhere in the known universe. You can sit in orbit around Jupiter, you can watch Hubble swing around Earth, or you can do what I did and start from Andromeda with a beautiful view of theMilky Way and fly at superluminal speeds back to our Sun. I made a short movie just to give you an idea - but it’s much better in the real program! You can see what the sky would have been like in Galileo’s time, or what you great*100 grandchiildren will see in the future. It’s available for Mac, Windows, Linux or pretty much anything, actually! Cool, hey?
If you’re feeling a little more terrestrial, then you might just want to see what the sky looks like tonight from your house. For Windows users, dial up Skyglobe for a shareware, fully functional and pretty much all you need planetarium program. For the Mac or Linux guys, try Kstars which seems to do everything I need as well. (Mac users wil need an X11 windows environment, and get Kstars through Fink/FinkCommander. Hope that means something to you - leave a comment if you want some links!)
So, go out tonight - have a look for your favourite planet, maybe check out the Pleides or marvel at the billions of stars that stretch out to form the hazy band of our galaxy.
I totally meant to post about this last week, but completely forgot - however, if anyone’s in Brisbane and wants to come to a lecture tonight, Helen Quinn, the AIP (Australia Institute of Physics) Women in Physics Lecturer 2005 is giving a talk at the University of Queensland campus on “The Mystery of the Missing Anti-Matter”. She’s going to be talking about why there is (apparently) no anti-matter in our universe, and what could have caused this imbalance. She’s a very good speaker - I saw her at the AIP Congress last week, although I do have to say that her talk there was disappointingly complex and over my head. I felt, though, that if I’d had a PhD in particle physics it would have been an awesome talk! This talk I think will be aimed at a much more general level, and I’m hoping it will be interesting even if you don’t know much particle physics.
Read on for the details…
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I just got my first paper accepted for publication! It’s on my work on modelling molecules in nature which interact with light (called chromophores.) Examples are the chlorophyll that plants (and some bacteria!) use to collect light for photosynthesis and retinal which is the molecule that detects light in our eyes. What’s really interesting about these systems is that quantum mechanics plays a vital role in both cases, making things fast and efficient. I don’t know whether this seems strange to you or not, but it’s certainly impressive that evolution was able to use quantum on such a large scale and to such good purpose!
The paper will be published in Journal of Physics: Condensed Matter, or, if you’re keen, there’s an earlier “preprint” version on line - it lacks all the polish and some information of the later article, but still has the important stuff. (This is a very common practice in physics, where you post a first (but good) draft of your paper online to be freely available for anyone to look at. Then, when you’ve got some feedback, you revise it, edit it, and submit it to a journal. I might write more about this
Suffice to say, I’m a very happy physicist today. Actually, this is technically my second paper (I was an author on a paper published by my partner last year) but this is the first paper from “my” PhD work, and my first “first author” paper (where I’m listed first on the author list, usually meaning that I’m the one that physically wrote the work.) And speaking of work, time to get started for the day!
Well, the curtain is falling on the Hubble Space Telescope. NASA officially announced last year that the telescope, nearing the end of its 15 year planned lifetime, would have any further repairs done on it which might extend its lifetime. The issues cited were not so much cost (although the $1billion price tag might have had something to do with ity) as the risk to the astronauts on a crewed repair mission. The possibility of a robot repair mission was bandied about, as was creating a new, improved Hubble clone which could be be built and launched for the same cost as repair. But NASA has nowannounced that Hubble will be taken out of orbit by a robotic mission, probably some time next year. It’s disappointing to see it go, and many scientists feel that it could still have made valuable contributions, but I guess it’s lived a full life, and it’s time to move on.
This is either really cool or really scary depending on how you look at it. Although I missed the stories in December, astronomers were very concerned about an asteroid they thought had a 1 in 40 chance of hitting Earth in 2029. Although that was low, it was high enough to create some concern - the asteroid was large enough to cause local devastation, but not big enough to wipe out the planet (phew!) Fortunately, further observations were able to more accurately measure the asteroids position and velocity, and the very accurate models which we have were able to show that it in fact wouldn’t hit. Instead, it’s going to be a very close flyby, with the asteroid passing inside the orbit of some of our satellites satellites and close enough to be visible to the naked eye. Woah!
The asteroid is apparently about 320m wide, and will pass within 36000km of the centre of Earth (or 25994km above the surface!) That’s scarily close in astronomical terms, but still far away for practical purposes. So don’t worry! Sleep easy tonight! No asteroids have our name on them yet - but astronomers will keep looking.
For some reason, I was thinking yesterday about the gravitational slingshot effect, which is used when you send a rocket to a far away planet, say Pluto. At typical speeds obtained from leaving Earth, the ship would take far too long to reach its destination. Instead, you send the ship for a detour past a large planet like Jupiter. The gravity from Jupiter accelerates the ship, and flings it off a high speed on a new, carefully calculated, orbit designed to hit Pluto - like a giant slingshot.
This is all well and good, but then I started thinking a little more - why should the ship get extra speed from the planet? Sure, it’ll speed up on the way in, but then it’ll slow down on the way out. Like rolling a ball down a small hill to try and get it up a big hill on the other side - it will speed up at the bottom, but ultimately get no higher than it started. Hmmm.
So, I turned to my trusty friend the Wikipedia and all was revealed - the planet is moving! Relative to the planet, the ship gets no extra speed - just as you’d expect. But because Jupiter is whizzing around the sun at high speed, our rocket gets dragged along by the planet’s gravity and picks up some of that speed.
It’s a bit like moving a magnet past a metal ball quick enough that the ball doesn’t stick, but still gets pulled along a bit by the magnet. Even once the magnet has gone, the ball keeps moving. Of course, this analogy isn’t really right either, but I tried one about a moving hill and it really didn’t work Feel free to contribute yourself if you like!
So the upshot of all this is my faith in space science is restored!
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