Theoretcial Physics

CosmicCrusader

Ok, well basically I'm a Leaving Cert student studying Physics for my exams next year. I love physics, but I especially love the stuff that's not on our course, mainly the theoretical stuff such as time travel, superstring theory, the Higgs Boson, exotic energy and particles and all that stuff. So I just thought this would be a fun thread for others with a passion for 'The Physics of the Unknown' to share their info and theories.



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adam500

The school curriculum is all about the basics of physics and famous physicists , which is important of course but what makes physics really exciting is all the fascinating theories that you have mentioned and which i think should be thought and discussed in school as it would most likely get more students interested in the filed of theoretical physics.

"CosmicCrusaider" have you come across Dr.Michio Kaku , he is basically the one who put the fun into theoretical physics

eamo12

Let me know if you ever get your head round the uncertainty principle - I certainly can't... "God don't play dice"

CosmicCrusader

adam500 wrote: »

The school curriculum is all about the basics of physics and famous physicists , which is important of course but what makes physics really exciting is all the fascinating theories that you have mentioned and which i think should be thought and discussed in school as it would most likely get more students interested in the filed of theoretical physics.

"CosmicCrusaider" have you come across Dr.Michio Kaku , he is basically the one who put the fun into theoretical physics

I agree with you 100%! As you've said, It's important to know the basics like gravity, acceleration, force and momentum, but I think it would be better to stop constantly boring the students when I'm sure that if you explained to even the most physics phobic person that theoretically time travel is possible then I'm sure you'd spark some kind of interest.

CosmicCrusader

eamo12 wrote: »

Let me know if you ever get your head round the uncertainty principle - I certainly can't... "God don't play dice"

I've actually been looking at that recently. It concern wave particle duality! Basically particles such as electrons and photons function both as particles AND waves. However, the uncertainty principle means that you cannot accurately measure them as both at the same time. For example, if i try to find the position of the particle then I cannot accurately find a speed for the wave. But, if i try find the speed of it as a wave then I cannot find an accurate position as a particle. It's very complicated and kind of hard to believe, but it makes sense I think.
I love these kind of theories because they boggle your mind and show you that the universe is such a complex and difficult thing to uderstand that I don't think our human minds will ever be capable of fully comprehending it! It's fun trying though.

CosmicCrusader

adam500 wrote: »

The school curriculum is all about the basics of physics and famous physicists , which is important of course but what makes physics really exciting is all the fascinating theories that you have mentioned and which i think should be thought and discussed in school as it would most likely get more students interested in the filed of theoretical physics.

"CosmicCrusaider" have you come across Dr.Michio Kaku , he is basically the one who put the fun into theoretical physics

I forgot to write in my last message to you that yes, I have come across him. I'm reading one of his books at the moment and he appears all the time on one of my favourite documentaries, The Universe

Podge_irl

If you have any interest in being a theoretical physicist than I can't stress enough the importance of maths. While it's interesting to have philosophical discussions about the likes of string theory and to give a "hand-wavey" description of them, they are ultimately very mathematical theories and require a large background in that field.

If you have any questions about string theory feel free to let them fly and I'll do my best to answer.

thecornflake

Podge_irl wrote: »

If you have any interest in being a theoretical physicist than I can't stress enough the importance of maths. While it's interesting to have philosophical discussions about the likes of string theory and to give a "hand-wavey" description of them, they are ultimately very mathematical theories and require a large background in that field.

If you have any questions about string theory feel free to let them fly and I'll do my best to answer.

Good advice.

Theoretical physics courses are ~2/3 maths and ~1/3 physics. It certainly is interesting but it is crucial to get familiar with the maths as has been said above ,that is where it all happens.

CosmicCrusader

Podge_irl wrote: »

If you have any interest in being a theoretical physicist than I can't stress enough the importance of maths. While it's interesting to have philosophical discussions about the likes of string theory and to give a "hand-wavey" description of them, they are ultimately very mathematical theories and require a large background in that field.

If you have any questions about string theory feel free to let them fly and I'll do my best to answer.

I'm considering theoretical physics or astrophysics as a possible career. The maths isn't really a problem for, I'm doing higher level maths and the lowest score I've gotten so far is a B1. I love maths!

sponsoredwalk

I bought the leaving cert physics book a year ago because I was too afraid to chance working on a college level text until I had the basics down but the thing is a total let down.

Isn't it totally algebra based, with absolutely no explanation for the equations of constant motion, half a paragraph on vectors, no good explanation of what a Joule is, etc...?

I gave up the book in disgust & was so happy I never did it in the L.C.

My advice is to get good at calculus, buy Young & Freedman University Physics and couple it with these video lectures.
It's better to learn physics critically and have the ability to rederive equations from first principles
rather than just accepting the equations they throw at you
& memorizing a sheet of plain nonsense,
(or worse, having it handed to you on the day!).

It might take longer and involve more effort but it's worth it

That said, it's probably not an option so I'll just pass on my condolences

If you want some pop sci books on the topic I've read a lot, here are the recommendations;

Euclids Window (Mlodinow)
Relativity (Einstein)
Parallel Universes (Kaku)
Black Hole War (Susskind)
God's Equation (Aczel)
Entanglement (Aczel)

Oh, and these if you want a semi-technical intro to college physics using rudimentary calculus that is free to watch online (I these videos to pieces!).
Actually, I think I've just given you an exciting summer with these videos :pac:

raah!

I agree! Alot of what was most difficult in first year physics for me was escaping from the useless conventions and simplifications built into my brain from the leaving cert. I sometimes still catch myself assuming a certain force is constant, or that things only depend on one variable or stupid things like that.

myfatherrsson

Theoretical Physics is the SH!T!!!

Ps. Dont by the University Physics book, you get it for free in first year in TCD

WalterMitty

did feynman write any textbooks?

Professor_Fink

eamo12 wrote: »

Let me know if you ever get your head round the uncertainty principle - I certainly can't... "God don't play dice"

It's actually not terribly complicated, but it's hard to explain if you don't know anything about the mathematics of quantum mechanics. Do you know much about vectors? If so, one way to think of it is that every quantum state can be represented as a vector, while every property you can measure (called an observable) corresponds to a basis on the vector space. When we measure something, we get one of the basis states from the basis associates with that observable with probability equal to the projection of the original vector along that particular basis state. If I measure two different observables, then order matters. You make a measurement of one observable, projecting onto one of those basis states and then measure the other projecting from this first basis state onto the second basis state. If I change the order then there is no reason to expect the result would be the same. This is the uncertainty principle. It is simply that the two different bases are potentially incompatible but complete descriptions of the same state. If the two bases are close then uncertainty is low, and if they are badly misaligned then the uncertainty is high. This uncertainty can be quantified mathematically by the commutation relation between the two operators [A,B] = AB-BA.

Professor_Fink

WalterMitty wrote: »

did feynman write any textbooks?

Yes, "The Feynman Lectures" which are an excellent introduction to theoretical physics.

Michael Collins

Professor_Fink wrote: »

Spoken like someone who didn't make the cut.

I guess it's not like quantum mechanics is useful for anything.... Oh wait, that's right, it basically underlies all major technological developments of the last 50 years.

Did you miss the "the" in his message Frink?

Nice explaination of the uncertainty principle there.

It can also be explained as a consequence of the Fourier Transform. The more bunched up f(x) is, the more spread out its transform F(x) is, and vice versa. Now since the momentum and position wave functions are Fourier Transform pairs: the more certain you are about the position (i.e. the more bunched up the position wavefunction is) the less you know its Fourier Transform, the momentum wavefunction - as this will be more spread out.

It's the same with time and frequency. The more bunched up a note on a tin whistle is (i.e. the less time it is played for), the more spread out its frequencies will be. Now take this to the extreme and imagine a tone played on an instrument from t = -infinity to t=+infinity, this will have one peak in frequency i.e. a pure tone, but it's very spread out in time - in fact it never starts or stops!

Similarly in QM, if you know a particle is free - i.e you have no idea where it is, you can tell its momentum exactly.

Professor_Fink

Michael Collins wrote: »

Did you miss the "the" in his message Frink?

Yes, yes I did. I'll go hang my head in shame.

Professor_Fink

Michael Collins wrote: »

It can also be explained as a consequence of the Fourier Transform.

Well, not in general. The Fourier transform happens to relate the position and momentum of a free particle, but this is not always true. If I choose a different pair of observables this relation does not necessarily hold, or if the system is not simply a free particle.

Michael Collins

Professor_Fink wrote: »

Well, not in general. The Fourier transform happens to relate the position and momentum of a free particle, but this is not always true. If I choose a different pair of observables this relation does not necessarily hold, or if the system is not simply a free particle.

Yeh fair enough, I will freely admit my level knowledge of real (i.e. mathematical) quantum mechanics is very low. When you say free particle, can it not also be applied to a 'particle in a box' type problem, bounded by potentials say?

myfatherrsson

Professor_Fink wrote: »

Yes, yes I did. I'll go hang my head in shame.

damn right.