Did you guys know you can see more than half of a neutron star due to gravitational lensing? Each checker in this picture represents 30 degrees by 30 degrees (from Wikipedia).
[img]http://upload.wikimedia.org/wikipedia/commons/thumb/a/a3/Neutronstar_2Rs.svg/800px-Neutronstar_2Rs.svg.png[/img]
that shape is confusing as hell
[QUOTE=Goodthief;39696865]that shape is confusing as hell[/QUOTE]
It's still a sphere. That shape represents what you would see. More than half of the light would reach you from gravitational lensing.
[QUOTE=agentalexandre;39690584]I can't find the Mathematics thread and this can be applied to physics in any case so I guess I'll ask here.
I have a second order autonomous system : dx/dt = f1(x,y) = 2xy , dy/dt = f2(x,y) = x^2 + y^2. I have been asked to find the nullclines and give a qualitative sketch of the phase diagram. I understand that nullclines are when f1(x,y) and f2(x,y) are equal to 0 - in this case the x-nullcline is the x axis and y axis , the y-nullcline is simply the point (0,0). This implies that the fixed points of the system is just the point (0,0) (intersection of nullclines). What I don't understand know is how I go about drawing the phase diagram. Anyone here know what I should be doing? Cheers.
Edit: found the maths chat, will post there as well, thread order on GD is all over the place.[/QUOTE]
Are the nullclines the same as separatrices (curves intersecting the fixed points)? If so, you just draw the curve by drawing f1=const and f2=const, e.g. x^2 + y^2 = const is a circle/ellipse.
First quantum midterm tomorrow morning. Wish me luck. Or wish that measurements of observables return values in my favor, or whatever.
I will do science to it.
[QUOTE=Falubii;39697523]It's still a sphere. That shape represents what you would see. More than half of the light would reach you from gravitational lensing.[/QUOTE]
So how much of the light is that? Is there a diagram of a map of earth next to a lensed map of earth or something?
i just took an electromagnetism midterm and i definitely did really well
Quantum mechanics tells us that anything can happen at any time for no reason. Also, eat plenty of oatmeal, and animals never had a war: who's the [I]real[/I] animals?
[editline]26th February 2013[/editline]
pretty sure dirac proved that
-don't watch Futurama/was dumb-
what
that's a professor farnsworth quote precisely none of that is true
[editline]26th February 2013[/editline]
except that you should eat plenty of oatmeal
What's the probability that you will nail the test?
[QUOTE=Krinkels;39716018]So how much of the light is that? Is there a diagram of a map of earth next to a lensed map of earth or something?[/QUOTE]
looking at that diagram ~~~1.125-ish (maybe) (possibly) (9 columns instead of 8 anyway)
[editline]26th February 2013[/editline]
it would obviously depend on how much a thing was lenses
According to the online gradebook, I got 28/30 on a quantum mechanics homework I never handed in. Good job, me.
[QUOTE=JohnnyMo1;39729001]According to the online gradebook, I got 28/30 on a quantum mechanics homework I never handed in. Good job, me.[/QUOTE]
It must have spontaneously materialized on the professor's desk.
Just built a small coil out of 22g tinned copper wire.
Threw a small round permanent magnet through it; it induced a current.
Now, to power it! >:D
Hey guys, I sorted through some old paper and found 2 old interlayers and since they always amazed me I thought I'd share it with you guys.
They made me truly understand for the first time how all of the universe can expand at the same time and everything basically drifts away from everything.
[IMG]http://i.imgur.com/3yiyKKS.gif[/IMG]
Basically it's 2 layers, one is an enlarged version of the other. YOu superimpose them so the red, green and blue cross are at the same point and so depending on where you're "standing" or "viewing", everything drifts away from a certain, and only ONE center.
In Mathematics this is called the Contraction Principle and it's an inherent part of consistent R^n dimensional vector spaces such as ours :)
You could also say: Every Cauchy-Concatenation in R^3 converges.
Cheers.
Oh yeah, I was a little lazy with the aligning but it works nevertheless.
Can anyone give an intuitive explanation for Snell's Law?
I suggest you grab a glass of water and stick a spoon into it and look at it from the side.Remember glass and water are both optically tighter than air.
[QUOTE=Killuah;39746055]I suggest you grab a glass of water and stick a spoon into it and look at it from the side.Remember glass and water are both optically tighter than air.[/QUOTE]
That doesn't do anything for me. I understand that it works, I want to know why.
Well technically I'd have to answer you that it's a derivative of the Fresnell Equations which in turn use energy conservation as a basic principle.
[editline]28th February 2013[/editline]
But maybe in laymans terms you could imagine a cube of glass. Now the light hits the cube on one surface and has one way or the other to cross it. It either stays it's projected path or changes its direction.
And in the "denser" medium it tries to have a path as short as possible.
[IMG]http://i.imgur.com/sXlfGe5.png[/IMG]
A question, is there any limit on how large you can make a nuclear/hydrogen bomb?
edit:
Like, could you build a bomb so huge that detonating it would blast Earth apart?
Critical Mass I suppose? There is a point where you have to create several smaller ones to explode all together.
Or you put in some kind of moderator but then you have to make it really really spacious with growing explosive potential and I guess there is a point where it's just not feasible anymore.
For the hydrogen bomb I suggest you take a nice little walk outside, not on a rainy day, and as soon as your nose tickles you take a look at the sun and then a second look and then you think.
[QUOTE=Killuah;39747970]Critical Mass I suppose? There is a point where you have to create several smaller ones to explode all together.
Or you put in some kind of moderator but then you have to make it really really spacious with growing explosive potential and I guess there is a point where it's just not feasible anymore.
[B]
For the hydrogen bomb I suggest you take a nice little walk outside, not on a rainy day, and as soon as your nose tickles you take a look at the sun and then a second look and then you think[/B].[/QUOTE]
Fuck, you got me good.
It's quite a funny thought isn't it?
[QUOTE=Swebonny;39747871]A question, is there any limit on how large you can make a nuclear/hydrogen bomb?
edit:
Like, could you build a bomb so huge that detonating it would blast Earth apart?[/QUOTE]
well the earth's gravitational binding energy is ~2.24 x 10^32 J, a bit more than 1 week of the Sun's total energy output
A 100 megaton H-Bomb releases ~4.184 x 10^17 J, so you'd need 5.353 x 10^14 100 megaton H-Bombs
One kg has a theoretical maximum yield of 6 kilotons, so 1kg can release up to 2.5104 x 10^13 J
This means you will need 8.92 x 10^18 kg of H-Bomb (not including non-exploding stuff). This is more than the amount of fissile/fuseble enriched material on the earth ever.
My experimental/report experience in the past 3 years:
-see how everyone manually does repetitive stuff (even postgrads o_O, they say 'they don't like programming')
-write Matlab script
-lean back
It's one of my favourite parts of "doing" physics, just making stuff like this. Have some graph porn.
[IMG]http://dl.dropbox.com/u/17216535/screengrab_20130228174744.png[/IMG]
It basically removes the bias from data (except for a user-selected interval where you don't want to ruin the actual data, there it just interpolates linearly from start to endpoint) and integrates it. Usually there's no "Interpolation" line, that's more of a control thing to see if it interpolates the data correctly (i.e. too much detail, too little, stuff like that)
It's an EPR graph of coffee (that peak basically indicates the presence of free radicals, coffee (or other dry "unwashable" foods) is often irradiated to kill microorganisms). Everyone else just clicks like 1530195425 times in Origin to do the same thing (okay for 2-5 datasets, but we need to do about 200-300).
I always do this stuff with Origin(not the EA one you doofuses)
[editline]28th February 2013[/editline]
But I gotta learn Matlab now for new courses
Origin has some cool stuff too but I'm not sure if it's good at batch-processing. I actually barely know anything about it, but I've seen it produce some neat graphs.
I don't get why Matlab gets so much hate, once you get past the syntax (which is great in comparison to stuff like Bash or Python, IMHO) it can save you tons of time.
It's very powerful when you want to fit graphs to data and it's almost no scripting, it's more like Excel with data analysis tools.
Sorry, you need to Log In to post a reply to this thread.