Ask a physicist

[cookyy2k]

After the "Wow! information!" thread the other day I realised a number of escapist members have an interest in physics (mainly astrophysics).

So this got me thinking, I'm a PhD student researching galactic dynamics and need to learn to put ideas across that are fairly complex in a accesible way. So I thought it'd be a good idea to see if any of you guys have any questions, anything from Newton's law to the most cutting edge quantum mechanics.

I'm not claiming to know everything here, chances are I'll have to do some research outside of my norm to answer them but it's worth it.

So the deal is; you ask me a question about something you've wondered or are interested in in the physical sciences and I'll do my best to answer them in an accessible way without spining it like the media always do when covering these topics. I'll get experience in putting these things across accessibly and you guys will get the answers to your questions, and also hopefully this will convince atleast someone that they want to go into science since their really isn't enough of us.

Feel free to ask any physics related questions you want, if I answer too simplistically or too advanced call me out on it and I'll try again. If you want you can message the question instead or ask follow ups by message. However you ask I will do my best to get you an accesible answer as fast as possible.

EDIT: A lot of people have been asking about string theory, unfortunately I just don't know enough on the topic to give a decent, acurate summary and the demands on my time from research make it damn near impossible for me to devote enough time to learning it. I'm sorry guys but on this I'm not really any use since I don't want to give some inaccurate piece of "I thinks".

 

[DonMartin]

Im a little afraid that way too many of the Escapists consider themselves genious physicists/mathematicians or the like to present someone who actually knows a thing or two with a question.. Just a hunch that this is going to happen.

Sorry, I have very little knowledge of physics outside the basics, but it's not really my favourite subject either. Dont get me wrong, I enjoy learning new things, no matter what they are. It's just that I have nothing to ask.

Nice idea though, this thread.

 

[SckizoBoy]

So the deal is; you ask me a question about something you've wondered or are interested in in the physical sciences and I'll do my best to answer them in an accessible way without spining it like the media always do when covering these topics.

... Does that include organic chemistry?!

In that case, something that's been bothering me for the last month: how in hell am I supposed to get a methyl substitution on the alkyne-terminal proton of propargyl-acetate?

In all fairness, I've just been too lazy to look up the literature (got other synthetic problems making my academic-head ache...).

Physics-wise, could you explain d-brane dynamics (to someone who does have some grasp of string theory)?

 

[quetzal231]

....I might have a question... Give me a minute.

Alright, I did this schoolwork for my English class about string theory.
After alot of researching, I find myself very confused.
So, could you explain the general M-theory?
And I know that this is not astrophysics, and that theoretical particlephysics may not be your area, but still, if you can answer I would be grateful.

I am also having trouble grasping the open-string and the closed-string theories.

//Me

 

[Feste the Jester]

How does centrifugal force work?

 

[Smooth Operator]

Alright, I got one, what exactly is dark matter, and howmuch of it is there really in our galaxy?

 

[Lukeje]

So the deal is; you ask me a question about something you've wondered or are interested in in the physical sciences and I'll do my best to answer them in an accessible way without spining it like the media always do when covering these topics.

... Does that include organic chemistry?!

In that case, something that's been bothering me for the last month: how in hell am I supposed to get a methyl substitution on the alkyne-terminal proton of propargyl-acetate?

In all fairness, I've just been too lazy to look up the literature (got other synthetic problems making my academic-head ache...).

Can you not form a 5/6-membered ring? If you could do that then the substitution would be fairly simple. Otherwise it's probably just some sort of Zn/Pt/Pd-catalysed substitution (that's soft enough that it doesn't interact with the ester--or alternatively picked cleverly enough that interaction with the ester leads to regiospecifity).

 

[artanis_neravar]

How does centrifugal force work?

It doesn't it is just a (flawed) perspective of the first law of motion

EDIT: centrifugal force is like when a car turns and you fell like you are being push against the door, in reality you are attempting to continue in your original path and when the car turned the door stopped you from continuing along that path

 

[Rockchimp69]

snip

This is probably one that could be answered elsewhere but it's always nicer to ask an actual person.
How does the Higgs Boson fit into the standard model of.. whatever theory it's part of? Does it make quarks and other matter or is another part of an atom or what?
Sorry about the lack of clarity

 

[cookyy2k]

How does centrifugal force work?

Centrifugal force is a "ficticious force" that comes from a non-inertial farme (a non-inertial farme being one which is not traveling in a streight line. It is the force for example which tryes to push you to the outside of a corner in a car, this is due to everything wanting to carry on in a streight line but having a force applied to make it turn.

Alright, I got one, what exactly is dark matter, and howmuch of it is there really in our galaxy?

This is almost precisely my research area! No one really knows what it is, there are several particle candidates however none have ever been detected. Dark matter is a theoretical substance that neither emits or scatters photons (light) but interracts with luminous matter (the stuff you see) through gravity. It has been introduced to make up for a large amount of missing mass in the Galaxy.

We measure and plot something called the rotation curve for galaxies, this is the rotational velocity of the star vs. its radius from the centre, now what is observed is hugely different to what is predicted. This was rectified by adding a "dark halo", a vary large, massive sphere of dark matter with the Galaxy in the centre. For comparrison the Dark halo is about 20 times as massive as what we see and has a radius around 20 times that of the Galaxy. However the density profile is not known well atall.

Other than that much is unknown since we have no way of directly observing it, just its effects on stuff we can observe.

To the string theory guys thanks for the questions I'm going to need just a little more time.

 

[SckizoBoy]

Can you not form a 5/6-membered ring? If you could do that then the substitution would be fairly simple. Otherwise it's probably just some sort of Zn/Pt/Pd-catalysed substitution (that's soft enough that it doesn't interact with the ester--or alternatively picked cleverly enough that interaction with the ester leads to regiospecifity).

Around an alkyne core?! Talk about ring-strain (even if 6-membered). Currently, the only thing I have in mind is using TBDS to protect the carbonyl, then assaulting it with a base to take off the terminal proton. My supervisor will probably come up with something a little more elegant than that.

How does centrifugal force work?

'Centrifugal' is actually a misnomer. The term in physics is 'centripetal'. Google that and read away, since it's quite a simple concept, IIRC (outward force created by rotation of a satellite around a central apex, connected by either gravity or a physical bond, which is the basis of self-straightening that makes space elevators easier to build than one might think, conceptually at least... I think). (disclaimer: SckizoBoy is not a physicist - in Phill Jupitus' voice, for one reason or another.)

 

[Lukeje]

Can you not form a 5/6-membered ring? If you could do that then the substitution would be fairly simple. Otherwise it's probably just some sort of Zn/Pt/Pd-catalysed substitution (that's soft enough that it doesn't interact with the ester--or alternatively picked cleverly enough that interaction with the ester leads to regiospecifity).

Around an alkyne core?! Talk about ring-strain (even if 6-membered). Currently, the only thing I have in mind is using TBDS to protect the carbonyl, then assaulting it with a base to take off the terminal proton. My supervisor will probably come up with something a little more elegant than that.

'Twould be an alkene. An alkane if you reduce it. I'm pretty sure you could do it with some nifty Zn chemistry...

 

[cookyy2k]

snip

This is probably one that could be answered elsewhere but it's always nicer to ask an actual person.
How does the Higgs Boson fit into the standard model of.. whatever theory it's part of? Does it make quarks and other matter or is another part of an atom or what?
Sorry about the lack of clarity

Bosons are a group of particles that causes forces in the standard model. Their is 4 forces in the standard model and every other force is just one of these. There are; Gravity (attraction between masses), Strong nuclear (responcible for keeping nucleii in one piece), weak nuclear (responcible for radioactivity) and Electromagnetic (magnets, light etc.).

These forces have been "married" in various ways (with the exception of gravity which just wont behave) and one particular combination is the electroweak interraction, this is the elctromagnetic and weak forces both being the same thing. This only holds true at energies above 100GeV (around 10[sup]15[/sup]k in temperature for example)

Now in everyday life (below those energies) the two forces differ grately. EM makes use of the photon with the weak making use of the W and Z bosons. The problem we come across here however is that the photon has zero mass but the W and Z bosons have relatively large masses so calling the two the same isn't possible. The higgs boson is a particle that tfits theoretically to explain why the W and Z boson should have mass now instead of remaining as photons when the energy is below 100Gev.

How does centrifugal force work?

'Centrifugal' is actually a misnomer. The term in physics is 'centripetal'.

Centrifugal and centripetal forces are not the same thing. Centrifugal is the force outwards when an object travels a curved trajectory, centripetal is the force inwards to make the object follow a curved trajectory.

EDIT: fixed quote

 

[Skuffyshootster]

Where do you see the scientific world in 50 years?

 

[SckizoBoy]

Around an alkyne core?! Talk about ring-strain (even if 6-membered). Currently, the only thing I have in mind is using TBDS to protect the carbonyl, then assaulting it with a base to take off the terminal proton. My supervisor will probably come up with something a little more elegant than that.

'Twould be an alkene. An alkane if you reduce it. I'm pretty sure you could do it with some nifty Zn chemistry...

... Oooh, now I get you. Nice idea, I'll have to look into that, though recovering the triple-bond is going to be difficult (yield might be rather poxy) and conditions are going to have to be monitored closely, don't want those electrons going anywhere... Anyway, don't think regiospecificity would be much of a problem.

Still, thanks for the suggestion, and the workup would be a hell of a lot easier than with silylating agents.

 

[mikey7339]

I'm confused as to how Hawking Radiation works.

I will admit this is laziness on my part as I have not researched into it. But I do not understand how a black hole can emit energy and eventually evaporate. Once matter crosses the event horizon of a black hole it can not escape. Since matter is a form of energy, shouldn't it be impossible for black holes to emit energy?

EDIT: Also, how do virtual particles exist without violating the law of conservation of energy?

 

[cookyy2k]

Where do you see the scientific world in 50 years?

Good question. unfortunaetly at the moment things without direct application (astrophysics, relativity etc.) are not getting the funding, only things which have a direct end product, graphene research is ridicuously well funded in the UK atleast this year but astro funding is not forthcoming. Is the way resession works I suppose, people want a product to sell at the end of the research but I think it's stunting us a little. I doubt we'll be seeing many of the hoped for sci-fi advances since they're unknowns, funding is easiest to get with a solid, proven concept (much like in the games world) so massive advances in certain areas are being hamstringed by the fact you have to put in a "safe" research proposal in order to get funding but then your "safe research" doesn't produce anything groundbreaking. This is becoming a bigger problem than in the AAA industry as their are much fewer funding opportunities and a well done reseach project can cost several times more so in a nut shell I don't think it's going to be anywhere near what we have achieved in 50 year period before when research could be done on a shoe string and funding was readily avaliable. That's the situation in the EU and from what I've heard US. Australia is the only place really funding this stuff but the job market is saturated because of it.

 

[GiglameshSoulEater]

Which idea of universe 'creation' i.e how it started, do you favor?
And isn't the big bang theory just on how it expanded 'n stuff after creation, not creation itself?

...

I haven't done advanced physics.