Check out Zooniverse - https://www.zooniverse.org/ - there's a lot of projects that are helped by citizen science. A nice platform where human powered processing can contribute. I don't think there's the kind of review etc you're asking for, but it does have a very nice interface for building your own project, contributing to others etc.
A single shot device like a railgun cannot launch something into orbit. You need a second impulse to alter the trajectory to achieve orbit. The reason is that orbits close - they're ellipses (or circles). So with a single shot device you either launch something to infinity, or you have it crash back into the planet as its orbit intersects the point of origin.
What you'd need in this scenario is either something to collect the sample already in low orbit, or a container with a thruster of some sort to force the trajectory into orbit. Either case increases the difficulty considerably.
The wake behind a ball is NOT like the tail of a comet - the tail of a comet points (approximately*) away from the sun, not opposite to the direction of motion.
Comet tails are not caused by some kind of drag - the comet moves in a vacuum in (almost**) geodesic motion around the host star.
* Yes, there are actually two tails, dust and gas, directly not exactly away from the sun. The point is really that comet tails do not follow comets around the sun.
Drag racing is normally quite a good intro topic for 1D kinematics - you can do constant acceleration, look at the real relations between velocity, acceleration and position etc. It's nice because you can push the students to understand when equations are and are not valid, and what they can actually work out with limited information.
I agree - that's why I said throughout that my estimate was conservative. Assuming constant acceleration gives the slowest possible 0-60, hence the max time from these figures is 3.25 seconds.
Interestingly if you look through the pictures in TFA you see that the speed has just about topped out at the 1/8 mile mark. If you run the numbers there, you get an acceleration around the 10.5 m/s^2 mark, which indeed gives about 2.5s for the 0-60 time.
And yes, clearly the car is not designed with cornering in mind.
I would hope one of the requirements to be a "street-legal" car is that it can turn, at the very least...
If we make a horrendous assumption of constant acceleration we can get a maximum on it's 0-60 time:
s=1/2 at^2, t=9.87s, s=400m gives a=8.21 m/s^2
60mph = 60*1600/3600 m/s= 26.67 m/s
t60 = 26.67/8.21 = 3.25 seconds.
So we can conservatively conclude this vehicle does 0-60 in under 3.25 seconds.
Someone with better knowledge of the acceleration/velocity curves of cars can probably correct me on this, but I'm assuming that acceleration reduces with velocity rather than increases, due to wind resistance etc. If this is right 3.25 should be considered a maximum - if the acceleration reduces above 60mph, say, then the car must accelerate to this velocity in even less time to get a quarter mile in 9.87s.
From the data given we can only conclude that its top speed is somewhat higher than 400m/9.87s = about 40m/s or 90mph, but of course that would assume instant acceleration to 90, in all likelihood its top speed is far higher.
The system is an interferometer - basically two lasers set up in a large L shape with mirrors (massive simplification). When the lengths of the arms are the same, the beams cancel, when they differ a signal is recorded.
Now, the differences in length due to a gravitational wave is tiny, and the problem that kept LIGO from their detection is that there are huge numbers of sources of vibrations around the same frequencies as expected from gravitational waves that have far larger amplitudes. Thermal vibrations, for example, are a killer for experiments like this.
The waves themselves have almost exactly the waveforms that were predicted - the template fits from simulations match amazingly well in terms of amplitudes, frequencies and their evolution. What stopped experiments like this from making the observation was simply a lack of technical skill to make a precise enough instrument. Following the development of LIGO over the last decade, this is precisely what everyone working on the project said - once the noise curve is reduced to form Advanced LIOG (recent upgrade) the noise would be sufficiently small than an integrated signal against a template would be clearly visible, and now it is.
Think about when the light at the edge of your calculation was emitted, and where that place is now. The definition of the observable universe goes roughly as follows:
Consider a photon emitted from a point at the big bang (really CMB, but we can substitute with a small change) that gets to us today. How far away is an object that was at rest (with respect to the homogeneous cosmological spatial slice) at that position now?
It isn't as simple as multiplying up these numbers, as the Hubble parameter changes over time. What you really want to do is track the world-line of an imaginary stationary object from which the light was emitted, and that of ourselves, integrating the Hubble rate given by Friedmann's equation given our best guesses at the types of matter/radiation dominating evolution. That's where the 28Gpc (about 90 billion light years) figure comes from.
The point that emitted the photon is now no-longer observable to us, and never will be again if the current models are correct - it's exited our past light cone, as does more and more of the spatial slice every instant. So there's no contradiction between the point moving away from us 'faster than light' and it having it in our observable universe. One is a calculation done about two spatially separated points at a fixed time, the other is understanding the content of our past light cone.
The Hubble constant which is talked about here is the rate of change of the scale factor, divided by the scale factor (H = 1/a da/dt or d/dt (log a). You can think about it as the velocity of log(a) if you like. The matter contribution means that the universe is expanding.
The cosmological constant contributes to the acceleration of expansion (dH/dt ~ (rho+P) ) where rho is the energy density, and P the pressure. For a pure cosmological constant, rho=P and so this is zero. Follow the calculus through and you see that this gives a positive second derivative in a - the universe is accelerating.
The point is that Hubble rate and cosmological constant are related, but separate ideas, and give non-degenerate contributions to observations - we can differentiate between the two. So a different Hubble observation would not, of itself, explain the cosmological constant problem.
It's a pleasure. I'm lucky enough to work on my passion, and to be able to talk about stuff like this with the people who work on it.
A side note - both Jesper and Johannes are very open and easy to talk to - I'm sure if they're not overwhelmed they'll respond to questions from the public about their ideas.
TL:DR - yes, it's a bit out there, but no more so than any other of the big attempts.
I've talked with Jesper and Johannes at length whilst I was a PhD student - their ideas are based on applying the techniques of loop quantum gravity to non-commutative geometry. To give a brief summary of each:
LQG regards the basic variables of geometry to be holonomies and fluxes - a holonomy is the transport of a vector around a small loop, coming back to the start to find the vector isn't pointing the same way (think about carrying an arrow around the a triangle from north pole to equator). This measures the curvature of the underlying manifold. The fluxes are like field lines in electromagnetism. It is these variables that are quantized (discretized) on a spin-network in LQG.
Non-commutative geometry is the idea that geometrical operators care about the order in which they are applied - area(A) length(B) != length(B) area(A) (very loosely). Non-commutativity is at the heart of quantum mechanics, and is the root of Heisenberg's Uncertainty Principle.
What they're hoping to do is build on the work of Connes and Chamseddine who have shown that the spectral action (special type of object in a non-commutative geometry, coming from application to the standard model) naturally reproduces the Einstein-Hilbert action (Basis of General Relatvity) in certain conditions. They hope that by applying LQG techniques here they'll get a full quantum theory of everything.
It's a long shot, of course, but all such things are - non commutative geometry is a strange beast, and no-one has shown that LQG is the right way to quantize gravity (though they have had some theoretical success in cosmology and black holes). It's a personal aesthetic as to whether you think this is more or less plausible than extra dimensions, or symmetries, or some altogether new principle. It's not something I choose to spend my time on as I don't think it's the right way to go (I don't like non-commutativity, and LQG involves fundamental discreteness in a way that I think doesn't work) but I would say it's as good an idea as any other on the market and deserves to be explored.
I just got a fairly substantial grant for a project from an external agency. However, as things stand, on this project I will not be the PI (primary investigator ) - that will be our head of dept. So why do I call it my grant? Because I wrote the proposal, handled all interactions with the funding agency, wrote the budget and arranged everything. My boss simply signed on a dotted line and shook a few hands. A symptom of the endless cycle of postdocs is that you don't have a permanent post until you're quite far on in your career. Therefore your own institution won't let you be the PI. The way around it is that you get a figurehead to be in charge, but you really end up running things.
This has its advantages and disadvantages. The big advantage is that you tend to have a fairly heavy hitter politically to back you up. He (and it's so often He that it's an insult to my female colleagues to pretend that they are equally represented) should have your back in exchange for drawing a fraction of his salary from your grant. The disadvantages are that you aren't officially PI for the sake of your CV - when you apply for jobs you are asked "Wasn't that X's grant?" when you talk about it - an it doesn't count as much for you. Likewise, they pay is miniscule. One of the things you learn writing a budget is just how much more a senior academic makes than a postdoc. It's depressing both how large the ratio is, and how relatively low the higher figure actually is.
Of course the whole process is a vicious cycle: You can't be PI, so you don't have PI positions on grants on your CV, so you have a hard time getting a permanent job, and so you can't be a PI... You just spend three of four months working on a proposal, sacrifice your dignity to the gods of the funding agency, ask someone else to take 90% of the credit, and prepare for hard work. On the plus side, you might just get paid enough to live and do what you love.
It was something that stuck in my mind from an explanation from a colleague, (Ph.D in film studies) so I'm not sure of a good citation. The best I can find with a quick Google is an appeal to QI (http://www.comedy.co.uk/guide/tv/qi/episodes/8/12/)
The reason that this became a widespread thing is that it was typically used in physical comedy in the early cinema era. Banana skins actually were substituted for horse dung, which is slippery to step in, and this was a much more common occurrence back before cars became ubiquitous. It was considered unseemly to show someone slipping in horse droppings, and would be stopped by the overzealous censors (not to mention offend the sensibilities of the time). The discarded banana skin took on the role as an inoffensive placeholder.
Well, there are a few things that would have to happen for them to compare clocks, and a key thing you're overlooking in your analysis:
1) For circular motion, the two ships would not have constant velocity in their _own_ reference frames - they're both accelerating towards the center (I'm assuming a flat space-time here for simplicity, but in GR things don't change much). Acceleration causes time dilation too!
2) For the ships to come together, they would have to maneouver. This will require further accelerations. Its during these that the other ship's clock will always appear to be moving faster.
What you've really got here is a reworking of the classical twin paradox - if one twin goes to Alpha Centauri (AC) and back, and the other stays on Earth, from _each_ perspective, the other one moves away then comes back. Yet the one who went to AC and back comes back younger - why? Well, what you're missing is that _at_ AC you have to slow down and then accelerate back towards Earth. This is the missing segment of the space-time picture, as the surfaces of simultaneity change during this acceleration.
The answer is that it's not much more difficult, but a lot more time consuming (gleaned from going to talks on the subject, not my area of expertise).
There are two basic ways that these planets are observed: They make the stars they orbit wobble (the basic 2 body problem - each body orbits the center of mass of the pair) and they dim the light from the star when they pass in front (like an eclipse).
The time problem comes from the fact that orbits are longer for objects more distant from the star. If we make the simplification that the orbit of the planet is basically circular, the time period for an orbit increases as radius^(3/2). (Insert semi-major axis for radius for non-circular). The standard is about three events separated by equal times to count as an observation - you have to wait to see an event at least twice to know the time period and so infer the radius of orbit, and once again to remove some flukes. Hence you're having to wait a long time looking at a star to see this happen.
Now, on top of that you've got the possibility that there's more than one planet, that the earth-like planet isn't the dominant mass, etc etc. This can all be cleverly dealt with (multiple wobbles, multiple eclipses) but it adds time to the confirmation process.
To give an example: Suppose you were somewhere near Proxima Centauri, and making the relevant observation looking for Earth. It would take at least three years to detect Earth, even if your telescope was amazing. Dynamics of the system would pick up the effect of Jupiter on the sun first, for the wobble detection (you wouldn't get much eclipse given the angle between the plane of the solar system and the position of PC) and it might take quite some analysis to pick up Earth at all given the effects of all the other planets.
Anyway, I'm sure some astro people can give a much better version of all this. Suffice to say that we aren't looking for Earth like planets at Earth like radii yet, but I imagine over the next ten to twenty years there will be a lot of poor graduate students analyzing data desperately looking for Gallifrey.
I can't do you a car analogy, but here's the very basic idea (massively watered down, physics friends - I know, I know, but let's try to keep this simple enough):
Consider a ball rolling on a set of hills and valleys. For our purposes, let's make it simple and 2-dimensional, but you can generalize quite easily. A 'vacuum' for this system equates to being at the bottom of a valley, as this is a point of lowest energy, and things tend to roll down and end up in the bottoms of valleys. The shape of the hill (called a potential which relates strongly to potential energy you might recall from high-school/college intro physics) determines the physical properties of the particle like its mass.
However, the valley you're at the bottom of might not be the lowest point overall in the system, it might just be a local minimum. This is what we call a 'false vacuum' in particle physics: A point in the system which looks to all intents and purposes to be a minimum in a small locale. However there could be a lower point.
Now, when you're just dealing with classical systems (like a ball rolling on a hill) this is all well and good. However in a quantum theory the wavefunction describing the particle can happily have non-zero values anywhere and (again very roughly speaking) this means that you can 'tunnel' from one minimum to another with some probability - breaking your false vacuum and moving you to another one. This tends to be in a downward motion - you go to a vacuum lower than the one you're in. This means that the mass of the particle will appear to change, and so all the physics you observe will be completely different.
These effects can related to all kinds of cool physics - the ones often talked in about popular-ish media are inflation/cosmological constant type things - if there is some energy associated with a particle being in a certain state, this can look a lot like a cosmological constant and produce and accelerating universe. However, if this isn't the global minimum there is a probability at all times that the tunneling effect mentioned above can happen, turning off the acceleration.
Anyway, hope that helps. Sorry I couldn't give you a car analogy, but here's an effort at one:
You (the particle) get a Mustang for your 17th birthday (lucky you!) and all your friends are jealous. You then start to think that since all the cars you see around you are worse than yours that you have the best car ever, and act accordingly. However, there is a chance that one day you'll catch glimpse of something sublime - an E-type. And your world view will change - there's a better car out there! Yours is only a false "best car ever", and now you have to act according to your new knowledge, which changes your behavior. Eventually you save up and buy yourself an E-type, moving to the 'true vacuum' / best car ever, and all your interactions with your friends are now based on this new car.
As others have suggested, co-op games are certainly the way to make things interesting and fun, especially when there's going to be an obvious skill imbalance. Also try to pick things with a very shallow learning curve - if she hasn't played games before, just getting the coordination with a controller or mouse can be frustrating enough.
Games that have a low punishment for failure are going to be key when someone is first starting. This isn't quite the same as a shallow curve, but you want a game that is forgiving of your errors whilst you learn to play. Similarly something that isn't high pressure is probably good for early games. Left 4 dead, despite its excellence, probably isn't the best way to get into things (but will make an incredible game later if she gets into it!)
There are a couple of games I've found that can be really great fun in this way, and depending on/her/ tastes, you should find something:
First there's Trine (and its sequel). You can pick this up quite cheaply, and it's a lovely fairytale of a game, beautifully drawn, gently but excellently narrated. It's a 1-3 player co-op platformer/puzzler (I played it with my partner who loved it) and having more people massively increases the fun. It also doesn't do the usual gendered thing with games of having "chick-armor" or "all people are male" - the female character (one of the three players) is very nicely done. Set on an easy mode it's simple to learn, works excellently with controllers and doesn't require too much coordination for a newcomer. If you pick your timing right, you can get it for about five dollars on Steam.
Another great coop game is Civilization V. I know it's not the most hardcore in terms of strategy of the series, (and I'm presuming as a gamer you know the series) but its very easy to learn and playing as a team, either hot-seat or with two computers, is very satisfying. A more experienced player can provide cover the learner in terms of military protection etc, or just set the game on sufficiently easy mode whilst she learns the basics. In coop mode you can learn a section of the game at a time whilst your partner takes care of the rest, so she can focus on military strategy and world domination whilst you build the empire to fund it, or she can learn to manage cities to produce culture and science whilst you cover her borders. The turn based nature of the game makes it easy for teaching someone how to play, and it offers a ton of depth and replayability.
On the RPG front, Torchlight is marvelous, with its sequel being a great 2-player game. It's diablo-esque, but maintains the joys of D2. It can get a bit hectic on occasion, which is very frustrating, but with a co-op game again you can cover her.
On the FPS/strategy, Orcs Must Die (2) is a nice one, but does suffer horrendously from a couple of things - it has a nice learning curve, but can get overwhelming fast which leads to frustration. Also it has tongue-in-cheek cliched characters which at first will look rather like the female is supposed to be the stuff of adolescent fantasy. It's not as bad as many out there, but let's just say that her armor is less than optimal in some regions.
Hopefully that should be something to get you going. Ignore the people who say "Don't do it" - of course you should try out new hobbies together, and you may find an excellent way to have fun together. My partner and I game together often, and sometimes at long distance is a great way to spend time "together" when you're apart.
Slashdot Mirror
Check out Zooniverse - https://www.zooniverse.org/ - there's a lot of projects that are helped by citizen science. A nice platform where human powered processing can contribute. I don't think there's the kind of review etc you're asking for, but it does have a very nice interface for building your own project, contributing to others etc.
A single shot device like a railgun cannot launch something into orbit. You need a second impulse to alter the trajectory to achieve orbit. The reason is that orbits close - they're ellipses (or circles). So with a single shot device you either launch something to infinity, or you have it crash back into the planet as its orbit intersects the point of origin.
What you'd need in this scenario is either something to collect the sample already in low orbit, or a container with a thruster of some sort to force the trajectory into orbit. Either case increases the difficulty considerably.
No. Von Braun learnt from Ley and Oberth, and did a PhD in physics specializing in rocketry at Friedrich-Wilhelm University.
"Self-taught rocket scientist..."
This is gonna be good.
Is a "farther" a distant dad?
The wake behind a ball is NOT like the tail of a comet - the tail of a comet points (approximately*) away from the sun, not opposite to the direction of motion.
Comet tails are not caused by some kind of drag - the comet moves in a vacuum in (almost**) geodesic motion around the host star.
* Yes, there are actually two tails, dust and gas, directly not exactly away from the sun. The point is really that comet tails do not follow comets around the sun.
** M_comet/M_sun is normally pretty small, etc.
Physics 101 baby ;-)
Drag racing is normally quite a good intro topic for 1D kinematics - you can do constant acceleration, look at the real relations between velocity, acceleration and position etc. It's nice because you can push the students to understand when equations are and are not valid, and what they can actually work out with limited information.
I agree - that's why I said throughout that my estimate was conservative. Assuming constant acceleration gives the slowest possible 0-60, hence the max time from these figures is 3.25 seconds.
Interestingly if you look through the pictures in TFA you see that the speed has just about topped out at the 1/8 mile mark. If you run the numbers there, you get an acceleration around the 10.5 m/s^2 mark, which indeed gives about 2.5s for the 0-60 time.
And yes, clearly the car is not designed with cornering in mind.
I would hope one of the requirements to be a "street-legal" car is that it can turn, at the very least...
If we make a horrendous assumption of constant acceleration we can get a maximum on it's 0-60 time:
s=1/2 at^2, t=9.87s, s=400m gives a=8.21 m/s^2
60mph = 60*1600/3600 m/s= 26.67 m/s
t60 = 26.67/8.21 = 3.25 seconds.
So we can conservatively conclude this vehicle does 0-60 in under 3.25 seconds.
Someone with better knowledge of the acceleration/velocity curves of cars can probably correct me on this, but I'm assuming that acceleration reduces with velocity rather than increases, due to wind resistance etc. If this is right 3.25 should be considered a maximum - if the acceleration reduces above 60mph, say, then the car must accelerate to this velocity in even less time to get a quarter mile in 9.87s.
From the data given we can only conclude that its top speed is somewhat higher than 400m/9.87s = about 40m/s or 90mph, but of course that would assume instant acceleration to 90, in all likelihood its top speed is far higher.
Noise. All kinds of noise.
The system is an interferometer - basically two lasers set up in a large L shape with mirrors (massive simplification). When the lengths of the arms are the same, the beams cancel, when they differ a signal is recorded.
Now, the differences in length due to a gravitational wave is tiny, and the problem that kept LIGO from their detection is that there are huge numbers of sources of vibrations around the same frequencies as expected from gravitational waves that have far larger amplitudes. Thermal vibrations, for example, are a killer for experiments like this.
The waves themselves have almost exactly the waveforms that were predicted - the template fits from simulations match amazingly well in terms of amplitudes, frequencies and their evolution. What stopped experiments like this from making the observation was simply a lack of technical skill to make a precise enough instrument. Following the development of LIGO over the last decade, this is precisely what everyone working on the project said - once the noise curve is reduced to form Advanced LIOG (recent upgrade) the noise would be sufficiently small than an integrated signal against a template would be clearly visible, and now it is.
Think about when the light at the edge of your calculation was emitted, and where that place is now. The definition of the observable universe goes roughly as follows:
Consider a photon emitted from a point at the big bang (really CMB, but we can substitute with a small change) that gets to us today. How far away is an object that was at rest (with respect to the homogeneous cosmological spatial slice) at that position now?
It isn't as simple as multiplying up these numbers, as the Hubble parameter changes over time. What you really want to do is track the world-line of an imaginary stationary object from which the light was emitted, and that of ourselves, integrating the Hubble rate given by Friedmann's equation given our best guesses at the types of matter/radiation dominating evolution. That's where the 28Gpc (about 90 billion light years) figure comes from.
The point that emitted the photon is now no-longer observable to us, and never will be again if the current models are correct - it's exited our past light cone, as does more and more of the spatial slice every instant. So there's no contradiction between the point moving away from us 'faster than light' and it having it in our observable universe. One is a calculation done about two spatially separated points at a fixed time, the other is understanding the content of our past light cone.
Hope that helps!
The Hubble constant which is talked about here is the rate of change of the scale factor, divided by the scale factor (H = 1/a da/dt or d/dt (log a). You can think about it as the velocity of log(a) if you like. The matter contribution means that the universe is expanding.
The cosmological constant contributes to the acceleration of expansion (dH/dt ~ (rho+P) ) where rho is the energy density, and P the pressure. For a pure cosmological constant, rho=P and so this is zero. Follow the calculus through and you see that this gives a positive second derivative in a - the universe is accelerating.
The point is that Hubble rate and cosmological constant are related, but separate ideas, and give non-degenerate contributions to observations - we can differentiate between the two. So a different Hubble observation would not, of itself, explain the cosmological constant problem.
It's a pleasure. I'm lucky enough to work on my passion, and to be able to talk about stuff like this with the people who work on it.
A side note - both Jesper and Johannes are very open and easy to talk to - I'm sure if they're not overwhelmed they'll respond to questions from the public about their ideas.
TL:DR - yes, it's a bit out there, but no more so than any other of the big attempts.
I've talked with Jesper and Johannes at length whilst I was a PhD student - their ideas are based on applying the techniques of loop quantum gravity to non-commutative geometry. To give a brief summary of each:
LQG regards the basic variables of geometry to be holonomies and fluxes - a holonomy is the transport of a vector around a small loop, coming back to the start to find the vector isn't pointing the same way (think about carrying an arrow around the a triangle from north pole to equator). This measures the curvature of the underlying manifold. The fluxes are like field lines in electromagnetism. It is these variables that are quantized (discretized) on a spin-network in LQG.
Non-commutative geometry is the idea that geometrical operators care about the order in which they are applied - area(A) length(B) != length(B) area(A) (very loosely). Non-commutativity is at the heart of quantum mechanics, and is the root of Heisenberg's Uncertainty Principle.
What they're hoping to do is build on the work of Connes and Chamseddine who have shown that the spectral action (special type of object in a non-commutative geometry, coming from application to the standard model) naturally reproduces the Einstein-Hilbert action (Basis of General Relatvity) in certain conditions. They hope that by applying LQG techniques here they'll get a full quantum theory of everything.
It's a long shot, of course, but all such things are - non commutative geometry is a strange beast, and no-one has shown that LQG is the right way to quantize gravity (though they have had some theoretical success in cosmology and black holes). It's a personal aesthetic as to whether you think this is more or less plausible than extra dimensions, or symmetries, or some altogether new principle. It's not something I choose to spend my time on as I don't think it's the right way to go (I don't like non-commutativity, and LQG involves fundamental discreteness in a way that I think doesn't work) but I would say it's as good an idea as any other on the market and deserves to be explored.
I just got a fairly substantial grant for a project from an external agency. However, as things stand, on this project I will not be the PI (primary investigator ) - that will be our head of dept. So why do I call it my grant? Because I wrote the proposal, handled all interactions with the funding agency, wrote the budget and arranged everything. My boss simply signed on a dotted line and shook a few hands. A symptom of the endless cycle of postdocs is that you don't have a permanent post until you're quite far on in your career. Therefore your own institution won't let you be the PI. The way around it is that you get a figurehead to be in charge, but you really end up running things.
This has its advantages and disadvantages. The big advantage is that you tend to have a fairly heavy hitter politically to back you up. He (and it's so often He that it's an insult to my female colleagues to pretend that they are equally represented) should have your back in exchange for drawing a fraction of his salary from your grant. The disadvantages are that you aren't officially PI for the sake of your CV - when you apply for jobs you are asked "Wasn't that X's grant?" when you talk about it - an it doesn't count as much for you. Likewise, they pay is miniscule. One of the things you learn writing a budget is just how much more a senior academic makes than a postdoc. It's depressing both how large the ratio is, and how relatively low the higher figure actually is.
Of course the whole process is a vicious cycle: You can't be PI, so you don't have PI positions on grants on your CV, so you have a hard time getting a permanent job, and so you can't be a PI... You just spend three of four months working on a proposal, sacrifice your dignity to the gods of the funding agency, ask someone else to take 90% of the credit, and prepare for hard work. On the plus side, you might just get paid enough to live and do what you love.
It was something that stuck in my mind from an explanation from a colleague, (Ph.D in film studies) so I'm not sure of a good citation. The best I can find with a quick Google is an appeal to QI (http://www.comedy.co.uk/guide/tv/qi/episodes/8/12/)
Well, it was the fashion of the time. Now gimme five bees for a quarter.
The reason that this became a widespread thing is that it was typically used in physical comedy in the early cinema era. Banana skins actually were substituted for horse dung, which is slippery to step in, and this was a much more common occurrence back before cars became ubiquitous. It was considered unseemly to show someone slipping in horse droppings, and would be stopped by the overzealous censors (not to mention offend the sensibilities of the time). The discarded banana skin took on the role as an inoffensive placeholder.
Well, there are a few things that would have to happen for them to compare clocks, and a key thing you're overlooking in your analysis:
1) For circular motion, the two ships would not have constant velocity in their _own_ reference frames - they're both accelerating towards the center (I'm assuming a flat space-time here for simplicity, but in GR things don't change much). Acceleration causes time dilation too!
2) For the ships to come together, they would have to maneouver. This will require further accelerations. Its during these that the other ship's clock will always appear to be moving faster.
What you've really got here is a reworking of the classical twin paradox - if one twin goes to Alpha Centauri (AC) and back, and the other stays on Earth, from _each_ perspective, the other one moves away then comes back. Yet the one who went to AC and back comes back younger - why? Well, what you're missing is that _at_ AC you have to slow down and then accelerate back towards Earth. This is the missing segment of the space-time picture, as the surfaces of simultaneity change during this acceleration.
I hope that clarifies things a bit.
We're in the EU, we're not dead. Are you confused, perhaps about the Euro?
That's no planet...
A big part of the problem is that there are few negative results in scientific literature. Ever found a paper with a clear negative outcome? I didn't.
Perhaps you should publish this finding.
The answer is that it's not much more difficult, but a lot more time consuming (gleaned from going to talks on the subject, not my area of expertise).
There are two basic ways that these planets are observed: They make the stars they orbit wobble (the basic 2 body problem - each body orbits the center of mass of the pair) and they dim the light from the star when they pass in front (like an eclipse).
The time problem comes from the fact that orbits are longer for objects more distant from the star. If we make the simplification that the orbit of the planet is basically circular, the time period for an orbit increases as radius^(3/2). (Insert semi-major axis for radius for non-circular). The standard is about three events separated by equal times to count as an observation - you have to wait to see an event at least twice to know the time period and so infer the radius of orbit, and once again to remove some flukes. Hence you're having to wait a long time looking at a star to see this happen.
Now, on top of that you've got the possibility that there's more than one planet, that the earth-like planet isn't the dominant mass, etc etc. This can all be cleverly dealt with (multiple wobbles, multiple eclipses) but it adds time to the confirmation process.
To give an example: Suppose you were somewhere near Proxima Centauri, and making the relevant observation looking for Earth. It would take at least three years to detect Earth, even if your telescope was amazing. Dynamics of the system would pick up the effect of Jupiter on the sun first, for the wobble detection (you wouldn't get much eclipse given the angle between the plane of the solar system and the position of PC) and it might take quite some analysis to pick up Earth at all given the effects of all the other planets.
Anyway, I'm sure some astro people can give a much better version of all this. Suffice to say that we aren't looking for Earth like planets at Earth like radii yet, but I imagine over the next ten to twenty years there will be a lot of poor graduate students analyzing data desperately looking for Gallifrey.
I can't do you a car analogy, but here's the very basic idea (massively watered down, physics friends - I know, I know, but let's try to keep this simple enough):
Consider a ball rolling on a set of hills and valleys. For our purposes, let's make it simple and 2-dimensional, but you can generalize quite easily. A 'vacuum' for this system equates to being at the bottom of a valley, as this is a point of lowest energy, and things tend to roll down and end up in the bottoms of valleys. The shape of the hill (called a potential which relates strongly to potential energy you might recall from high-school/college intro physics) determines the physical properties of the particle like its mass.
However, the valley you're at the bottom of might not be the lowest point overall in the system, it might just be a local minimum. This is what we call a 'false vacuum' in particle physics: A point in the system which looks to all intents and purposes to be a minimum in a small locale. However there could be a lower point.
Now, when you're just dealing with classical systems (like a ball rolling on a hill) this is all well and good. However in a quantum theory the wavefunction describing the particle can happily have non-zero values anywhere and (again very roughly speaking) this means that you can 'tunnel' from one minimum to another with some probability - breaking your false vacuum and moving you to another one. This tends to be in a downward motion - you go to a vacuum lower than the one you're in. This means that the mass of the particle will appear to change, and so all the physics you observe will be completely different.
These effects can related to all kinds of cool physics - the ones often talked in about popular-ish media are inflation/cosmological constant type things - if there is some energy associated with a particle being in a certain state, this can look a lot like a cosmological constant and produce and accelerating universe. However, if this isn't the global minimum there is a probability at all times that the tunneling effect mentioned above can happen, turning off the acceleration.
Anyway, hope that helps. Sorry I couldn't give you a car analogy, but here's an effort at one:
You (the particle) get a Mustang for your 17th birthday (lucky you!) and all your friends are jealous. You then start to think that since all the cars you see around you are worse than yours that you have the best car ever, and act accordingly. However, there is a chance that one day you'll catch glimpse of something sublime - an E-type. And your world view will change - there's a better car out there! Yours is only a false "best car ever", and now you have to act according to your new knowledge, which changes your behavior. Eventually you save up and buy yourself an E-type, moving to the 'true vacuum' / best car ever, and all your interactions with your friends are now based on this new car.
OK, that was godawful. But I tried.
As others have suggested, co-op games are certainly the way to make things interesting and fun, especially when there's going to be an obvious skill imbalance. Also try to pick things with a very shallow learning curve - if she hasn't played games before, just getting the coordination with a controller or mouse can be frustrating enough.
Games that have a low punishment for failure are going to be key when someone is first starting. This isn't quite the same as a shallow curve, but you want a game that is forgiving of your errors whilst you learn to play. Similarly something that isn't high pressure is probably good for early games. Left 4 dead, despite its excellence, probably isn't the best way to get into things (but will make an incredible game later if she gets into it!)
There are a couple of games I've found that can be really great fun in this way, and depending on /her/ tastes, you should find something:
First there's Trine (and its sequel). You can pick this up quite cheaply, and it's a lovely fairytale of a game, beautifully drawn, gently but excellently narrated. It's a 1-3 player co-op platformer/puzzler (I played it with my partner who loved it) and having more people massively increases the fun. It also doesn't do the usual gendered thing with games of having "chick-armor" or "all people are male" - the female character (one of the three players) is very nicely done. Set on an easy mode it's simple to learn, works excellently with controllers and doesn't require too much coordination for a newcomer. If you pick your timing right, you can get it for about five dollars on Steam.
Another great coop game is Civilization V. I know it's not the most hardcore in terms of strategy of the series, (and I'm presuming as a gamer you know the series) but its very easy to learn and playing as a team, either hot-seat or with two computers, is very satisfying. A more experienced player can provide cover the learner in terms of military protection etc, or just set the game on sufficiently easy mode whilst she learns the basics. In coop mode you can learn a section of the game at a time whilst your partner takes care of the rest, so she can focus on military strategy and world domination whilst you build the empire to fund it, or she can learn to manage cities to produce culture and science whilst you cover her borders. The turn based nature of the game makes it easy for teaching someone how to play, and it offers a ton of depth and replayability.
On the RPG front, Torchlight is marvelous, with its sequel being a great 2-player game. It's diablo-esque, but maintains the joys of D2. It can get a bit hectic on occasion, which is very frustrating, but with a co-op game again you can cover her.
On the FPS/strategy, Orcs Must Die (2) is a nice one, but does suffer horrendously from a couple of things - it has a nice learning curve, but can get overwhelming fast which leads to frustration. Also it has tongue-in-cheek cliched characters which at first will look rather like the female is supposed to be the stuff of adolescent fantasy. It's not as bad as many out there, but let's just say that her armor is less than optimal in some regions.
Hopefully that should be something to get you going. Ignore the people who say "Don't do it" - of course you should try out new hobbies together, and you may find an excellent way to have fun together. My partner and I game together often, and sometimes at long distance is a great way to spend time "together" when you're apart.