Ask a physicist
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That's always been my fallback, there's usually a pretty specific catalyst for anything you want to do.Lukeje said:
I sincerely hope you continue your education by any possible means. When you get to a university, you will find that knowledge goes so deep and so wide that you'll wonder how to manage. Pick a field you like and focus on it. I had to join the navy out of high school to get money for school, but I hope you don't have to do the same. The good part is that I'm on my way to a PhD, and I'm a better person for it.nerd51075 said:
Shoot me if this is stupid but:
Is it possible to trap light in a sphere which has it's inside completely coated in mirrors?
My reasoning is that as light has a speed there will always be some light left in there when the lid is closed at any time, bouncing around and not reacting with anything.
I have no idea how you would measure whether there is light in there, but is it still there?
Is it possible to trap light in a sphere which has it's inside completely coated in mirrors?
My reasoning is that as light has a speed there will always be some light left in there when the lid is closed at any time, bouncing around and not reacting with anything.
I have no idea how you would measure whether there is light in there, but is it still there?
What big breakthrough can you see, with the right funding and research see happening in the near (or moderately far) future?
Schrodinger's photon?Joey Wonton said:
Anyway. I am currently doing an undergrad Ba Science and I really fucking loved biomechanics, I specifically liked fluid dynamics and the various applications of aerofoils. We only covered Newtonian physics, Bernoulli's Principal, Collisions, Friction and basic forces (linear and angular) but I want more.
Can you please explain to me (with consideration of my rudimentary knowledge of physics) how stunt planes can fly upside down. I am assuming it's to do with the angle of incidence if the aerofoil but I can't find any mention of this in my text books.
What kind of observations would provide evidence for or against string theory, and when are we likely going to be able to have the equipment and methods to actually be able to make them?
I'm not 100% on what he now supports but in a brief history of time he states his dislike for his own theory of the big bang.IvoryTowerGamer said:
Yep, I can't see a reason why not, conservation of momentum isn't violated aslong as you recognise that the frame changes when you entre/leave the protal pair.Bajinga said:
Time does indeed slow down as you speed up, an observer at rest would see your clock moving slower than theirs as you would see theirs moving faster.DasDestroyer said:
This all happens because the speed of light in a vacuum must be the same for all observers. For example if you throw a ball at 5km/h relative to the ground whils stood still then throw the ball at the same speed from a car moving at 5km/h in the same dircetion you throw it the ball will travel at 10km/h according to an observer stood at the side of the road.
However in the case of light if the car is stationary and you turn on the lights the light will travel at 300,000km/s way from the car, however if you're drving 5km/h and turn on the lights the light must travel away from the car at 300,000km/s however to an observer at rest at the side of the road the light MUST also travel at 300,000km/s. Thus either time or distance has to be adjusted to make them agree, depending on who's perspective you look from either time must slow down or the lengh must become smaller. These are called time dilation and length contraction respecively and are the same effect observed from two different frames.
Infact if you look into relitivity electricity and magnetism are the same thing just observed from different frames.
As for travelling back in time their are a few issues in relitivity. At the speed of light you must experience time stop (to keep the speed of light agreed upon) so it never reverses, Relitivity says you can't go faster than light so that's out and a lesser known part of relativity is that causality MUST always exist, the effect can never come before the cause from any reference frame.
Good, it's a wonderfully deep rabbit hole and seriously scientists are always needed. The summer after I graduated I got 3 job and 5 PhD offers, quite a descision to make which to go for but atleast it's not unemployment.nerd51075 said:
I'm afraid I don't really know so much about string theory to be that much use on making sence of the research (Sorry everyone who've asked but I've tried)Quaxar said:
However on the quantum tunneling the source is: http://srv2.fis.puc.cl/~mbanados/Cursos/TopicosRelatividadAvanzada/Hawking.pdf
It first mentions it on page 4 but this is a long paper with lots of great reasonings.
What is the correct verb to describe causing torque on an object? You exert a force, but you _____ a torque?
Whilst yes, you could create a close approximation to this set up it's only really any use as a thought experiment since no mirror is 100% efficient at reflecting light so the mirrors would absorb some of the light over time. As for the light still being in their well as already stated it's like the shrodinger's cat argument but with a photon.Joey Wonton said:
Silicon atoms have 4 electrons avaliable to form covalent bonds (valence electrons) and so can make a lattice with 4 bonded neighbours. If you take a sheet of pure silicon and stick an atom with a different number of valenvce electrons in their instead of one of the silicons you can produce charges. For example if you stick an atom with 5 valence electrons if will bond in the lattice with 1 electron left over producing an overall negative charge (an N doped semiconductor). If you stick an aton with only 3 valence electrons however you'll be one electron short and produce an electon "hole" which is taken as a positive charge with the same mass as an electron, this is a P doped semiconductor. Both the elctrons and holes can move through the lattice.Redingold said:
If you bring a P semiconductor into contact with an N semiconductor to for a junction (a join between the two material) the holes and electrons that can will cancell near the junction, this is called the "depleted region" which is neutral. If you put a negative potential on the P side all that will happen is the elctrons and holes will combine to increase the depleated region and no current will flow through the junction. If you put a negative on the N side however it will force the electrons across the junction making the junction conduct. This is the behaviour of a diode. All semiconductor devises are made out of P and N doped semiconductors being brought together in junctions.
Careful choosing of how many donor atoms (the added atoms) and how thick a silicon wafer to use allows control over the depleted region size and so the operating potential of the device.
Electrons are particles known as fermions, fermions have a spin of 1/2 (spin is a quantum propety of the particle). As such an electron can have an up or a down spin (1/2 or -1/2). Since spin can be flipped and measured very quickly it was proposed you could have +1/2 spin as a 1 and -1/2 as a 0 in a computer system.rotkiv said:
This would produce a very fast computer with very high data densities, the issue however is that the electrons can't be decoupled from eachother meaning that you flip one and it's neighbours feel a force from this, if this force causes a neighbour to flip you now have a wrong bit and worse still it can cause it's neighbour to feel a force and so on. Data corruption very quickly becomes an issue and this is the main area of research today, stopping this from happening.
Well their is a joke in physics "fusion is 40 years away and always will be"... ok not that funny but it says it all, many physisists have said I'll have this working in xx years then when they can't someone else will make a similar claim and so on. Fusion power has had 40 years said about it twice about 20 years apart so that's the origin of the joke.JochemDude said:
As for what I think will be happening, well graphene is a very exciting material. it's one atom thick but has a breaking strength 200 times that of steel, is is VERY light weight, it is virtually see through, it has the lowest resistance like for like of any material at room temperature, It can be cut in different ways to make it behave electronically like a metal or a semiconductor, graphene transistors have been produced and can handle 10Ghz even at 127 degrees c and these were 240nm gates where the new i processors use 45nm gates (smaller is faster)! And most importantly it's being massively funded because of these applications. IBM is the main funder however many companies are after the patents and I think we could see graphene RAM and processors very quickly after someone works out a cheap way of producing it.
It is indeed angle of incidence between the wind and the wing, if you stick your hand out the car window on the motorway you will notice it can be forced up or down depending on how you position your hand incident to the wing. Now your hand is a terrible wind shape however it can still produce lift, this is all down to how the wind interracts.StBishop said:
Again really sorry on this but I really don't know enough about string theory to be making much sense from the papers. Having a quick look I think the most achievable would be proving that gravity is anomanously large at small scales, however how or when this will be possible I'm not that well up on these theories.falconsgyre said:
I can't seem to find a completely straight answer on this.
Is quantum uncertainty really random or is it simply unpredictable like a duality of nature, similar to how we can't know both location and speed (wave-particle duality).
Basically I want to know if it's merely unpredictable or truly random.
Is quantum uncertainty really random or is it simply unpredictable like a duality of nature, similar to how we can't know both location and speed (wave-particle duality).
Basically I want to know if it's merely unpredictable or truly random.
Well heisenberg uncertanty is dx*dp > hbar/2 where dx is error in possition, dp is error in momentum. Meaning if you know with absolute certanty where something is you cannot know anything about it's momentum.NightlyNews said:
This is because x and p don't commute. For example if y and z are any real number then y and z commute: [y,z]=yz-zy=0 this means if you write them anyways round its the same. This cannot be said of x and p, [x,p]=xp-px=ihbar...
Heisenberg's reasoning was to use a thought experiment. He reasoned that if you used a microscope to obseve an electron by shooting a photon at it you get two problems;
1) If you use a high energy photon (short wavelength) then you could get very accurate position information from the electron however this photon transferes an unknown momentum to the electron, if you use a low energy photon it wont give much momentum to the elctron so you can easily measure it, however because of the large wavelength you'd only get a very fuzzy information on it's possition.
2) If you use a large apperture microscope you would get good positional information but poor momentum information and a small apperture would give the other way around.
This in summary is the errors in quantum mechanics will always be a trade off as knowing one thing entiresly prevents knowlage of the other. If you measure one precisely then the other presisely you loose all infromation on the first measurement.
An interresting result of another uncertanty (dEdt>h, where de is error in energy and dt is error in time) allows the creation or destruction of energy on short time scales, allowing the production, from nothing of a mass known as a virtual particle aslong as it is very short lived and it's energy is destroyed with it.
EDIT: sorry didn't really answer the question...
This uncertanty is intrinsic to quantum mechanics, the problem is you change the wavefunction by measuring it, this leads to "wavefunction collapse" and so you loose all previous knolage about the particle.
Didn't see your edit there, well this question is answered above so I edited in your quote so that the question got answered for you.mikey7339 said:
Well fusion technologies ae getting closer and closer to this. A tokamak has been built that can run at break-evern (that is produces as much energy as it uses) and it seems that the bigger they are the more efficient they are. To that end the EU are building an evern bigger one to see if they can actually have more energy than is needed to run the thing. I think it's the tocamak type reactor that will be the first viable source as this is the only way they've broke even and is getting a lot more investment due to this. If they get it working and can learn things from it to apply to other cheaper methods then any current method has the potential to be the future of fusion.tsb247 said:
So I think we'll be far more likely to see tokamak type reactors in our lifetimes than any other. The problems again are it's very expencive to construct these things so unless you have proven ideas and theories you wont get funded. Just like the analogy to the AAA games market earlier in the thread, things don't get made that arn't going down proven paths but that really limits the growth of the industry/research.