• Physics Discussion
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[QUOTE=Falubii;39961981]How do you get a string theorist off your porch? [sp]Pay him for the pizza.[/sp][/QUOTE] I don't know if it's this way anymore but it used to be string theorists were all physics departments wanted to hire [editline]18th March 2013[/editline] We only have two on staff here but a bunch more are being hired for next fall
I was just asking one of my professors which theorists in the department are willing to give undergrads research projects and the professor who was in the class giving an overview of his research just came over and asked what I was interested in and said he could give me a theory project if I wanted. :D Today is a good day.
So you're a junior, right? What university?
Goddamnit why did they have to split our 12 credit bachelor's thesis into two smaller ones of 6? It's pointless, I want ONE subject where I can lose myself in. Now I have to juggle these two and meet with two professors all the time. That's two posters and two 15 page texts too. Fuck you, council/department who did this. I wonder if this was proposed by students or not (because we do have yearly evaluation talks about the course itself)
[QUOTE=Falubii;39986898]So you're a junior, right? What university?[/QUOTE] A senior. A SUPER-SENIOR in fact, in my fifth year. Virginia Tech.
I start at University of Illinois Physics in the fall. I'm told they have one of the better programs in the country.
I like physics, it's neat.
[QUOTE=JohnnyMo1;39962503]I don't know if it's this way anymore but it used to be string theorists were all physics departments wanted to hire [editline]18th March 2013[/editline] We only have two on staff here but a bunch more are being hired for next fall[/QUOTE] Interesting - I was told string theory/quantum gravity had no job prospects at all by a guy who does it :P I wanted to do it but I'm kinda thinking of not staying in physics given how insane the competition is!
[QUOTE=Cooty;39998266]Interesting - I was told string theory/quantum gravity had no job prospects at all by a guy who does it :P I wanted to do it but I'm kinda thinking of not staying in physics given how insane the competition is![/QUOTE] Well the job prospect is "work at a university."
The main reason neutron radiation is so bad for biological organisms is because neutron radiation very readily interacts with hydrogen (which, number-wise, is probably the most abundant kind of atom in our body), and the reason that was explained to me for the high number of reactions between neutrons and protons is that neutrons are almost the same mass as protons, and the nucleus of a hydrogen atom is just that - a proton - and when collisions occur between the two it's like billiard balls. Momentum is shared quite equally so hydrogen atoms get launched around the place (which eventually slows the neutrons down to thermal energies at which point they can irradiate us). We might have gone through the specifics in last years nuclear physics course, although I honest can't remember (perhaps we'll cover it in the more advanced nuclear physics course this year), but I was wondering earlier at work - how can neutrons 'collide' with protons? I mean what we call 'colliding' is actually just electromagnetic repulsion between electron clouds in atoms that make up some body (for example billiard balls). Neutrons don't have electron clouds. They are made up from quarks though which are individually charged so I could almost see some kind of dipole like formations occurring, but I don't know if such a concept is even reasonable or sensible on the length scales we're talking about. The only thing that I could really imagine happening would be that the strong nuclear force is reeling fast neutrons into the nuclei of atoms (hydrogen in this case) and the addition of nuclear energy is so much greater than the stable configuration that the neutron and the proton almost immediately separate again so you don't really see any proper irradiation going on (or at least not much that you could probably measure very reasonable).
I've been really interested in nuclear reactions lately and have been reading [i]The Making of the Atomic Bomb[/i] by Richard Rhodes. It's a really long book; I'm on page 400 and they haven't even said the words Manhattan Project yet.
Can anyone help me with this grade 11 physics question? A 1.2 x 10^4-kg truck is travelling south at 22 m/s. a)What net force is required to bring the truck to a stop in 330m? b) What is the cause of this net force?
a) 1. Find the acceleration required to stop the truck in that distance: V(f)^2 = V(i)^2 + 2 * a * x (0)^2 = (22 m/s)^2 + 2 * a * (330 m) a = -7.33 m/s^2 2. Calculate force required to cause this truck to accelerate at that value: F = m * a F = (12000kg) * (-7.33 m/s^2) F = -8800 N (with respect to the truck; can also be written as 8800 N due north) b) The cause of this force is most likely friction between the tires and the road. The truck could also be mowing down a constant wave of pedestrians.
[QUOTE=Shirky;40016858]b) What is the cause of this net force?[/QUOTE] Many tiny ants wearing harnesses.
Let's play a game where we compile all the different answers he could give. b) Really strong gust of wind. Rocket engine mounted on the front of the truck.
b) Radiation pressure from nearby supernova
[QUOTE=JohnnyMo1;40000346]Well the job prospect is "work at a university."[/QUOTE] I'm aware of that - what the prof I talked to said was that there are no places going for it. He could have been wrong or have outdated knowledge, obviously, but he's kinda a big deal in the area, so I'd imagine he'd know.
[url]http://en.wikipedia.org/wiki/EmDrive[/url] If this works, it would revolutionise science and spacetravel. At least it's a start by having it tested at a university unlike the cold fusion fraud a few years back. Anyone able to get their head around the claimed physics? [editline]28th March 2013[/editline] A supposed paper from China backing it: [url]http://www.emdrive.com/yang-juan-paper-2012.pdf[/url]
Not until there's decent peer-review [editline]27th March 2013[/editline] And considering it's under heavy criticism by a doctor of relativistic electrodynamics, I'm willing to bet it doesn't pan out. [editline]27th March 2013[/editline] [QUOTE=Cooty;40055548]I'm aware of that - what the prof I talked to said was that there are no places going for it. He could have been wrong or have outdated knowledge, obviously, but he's kinda a big deal in the area, so I'd imagine he'd know.[/QUOTE] Like I said, the string theorist here that I talked to said several more string theorists are being hired here for the fall.
[QUOTE=JohnnyMo1;40057987]Not until there's decent peer-review [editline]27th March 2013[/editline] And considering it's under heavy criticism by a doctor of relativistic electrodynamics, I'm willing to bet it doesn't pan out. [/QUOTE] Probably, but it would be incredibly cool if it does
Why is Kelvin a base unit when it's really just the motion of particles? Are the base units named so because of convenience?
[QUOTE=Falubii;40078836]Why is Kelvin a base unit when it's really just the motion of particles? Are the base units named so because of convenience?[/QUOTE] Well degrees Celsius was the unit of temperature that became properly integrated into physics and chemistry, but when all of those nasty divide by zero issues and nonsensical answers to equations when negative temperatures were used became apparent the whole scale got shifted down so that everything made sense. You'd have to redefine a lot of shit to have a modified Fahrenheit scale (or some other scale) take the place of the Kelvin scale (and why on Earth would you ever even want such a thing)?
[QUOTE=Falubii;40078836]Why is Kelvin a base unit when it's really just the motion of particles? Are the base units named so because of convenience?[/QUOTE] Temperature isn't mean velocity of a group of particles, it's mean energy. Taking the average velocity of a mass of particles would statistically go to 0, and taking the average speed is meaningless because that doesn't necessarily represent the temperature. For example, radioactive particles release photons that cause an addition in heat, changing temperature.
[QUOTE=Disseminate;40082296]Temperature isn't mean velocity of a group of particles, it's mean energy. Taking the average velocity of a mass of particles would statistically go to 0, and taking the average speed is meaningless because that doesn't necessarily represent the temperature. For example, radioactive particles release photons that cause an addition in heat, changing temperature.[/QUOTE] Okay, then why is an average of energy a base unit? Energy is a derived unit.
Is Knot Theory an actual scientific theory of physics?
[QUOTE=sltungle;40080685]Well degrees Celsius was the unit of temperature that became properly integrated into physics and chemistry, but when all of those nasty divide by zero issues and nonsensical answers to equations when negative temperatures were used became apparent the whole scale got shifted down so that everything made sense. You'd have to redefine a lot of shit to have a modified Fahrenheit scale (or some other scale) take the place of the Kelvin scale (and why on Earth would you ever even want such a thing)?[/QUOTE] Not what I was asking, but thank you for replying. Damn you Nikita.
[QUOTE=Falubii;40085090]Okay, then why is an average of energy a base unit? Energy is a derived unit.[/QUOTE] Beats me.
[QUOTE=Nikita;40085107]Is Knot Theory an actual scientific theory of physics?[/QUOTE] Physics? No. Not that I know of. It's subdiscipline of topology.
[QUOTE=JohnnyMo1;40085767]Physics? No. Not that I know of. It's subdiscipline of topology.[/QUOTE] This [url]http://www.nytimes.com/1989/02/21/science/mathematicians-link-knot-theory-to-physics.html[/url] And also this: [url]http://www.ams.org/meetings/lectures/kauffman-lect.pdf[/url] Are they just starting out so it isn't yet applied to physics well?
[QUOTE=Nikita;40085895]Are they just starting out so it isn't yet applied to physics well?[/QUOTE] "Just starting out." That first article is almost 25 years old. :v: But as far as I know, it's still not very prevalent in physics. It's just a mathematical discipline.
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