TSR Physics Society

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Reply 740

rbnphlp

mountainmetman

Better than owt else on t'telly that night.

arsenal V porto seemed much interesting :p:

..Iam yet to watch the whole thing Ill comment in a bit

Reply 741

trm90

rbnphlp

Did anyone watch this ?what did you guys think?

Too wishy washy and pop sciency for me. I am becoming increasingly skeptical of cosmology as an experimental science and now I just feel like it's similar to string theory - just a bunch of physicists fabricating weird theories so that it satisfies their equations. The dark flow bit was interesting but otherwise, a little disappointed in it!

Reply 742

mountainmetman

trm90

I know what you mean!
Having said that, once the allowances for expansion have been made, the predictions that hte standard model produces are good to a surprisingly high degree, it's more like Newtonian gravity than Strings. The predictions are good enough for most uses, its just when you get to the edges that things go a bit screwy.
When it comes down to it, we're scientists, so if the evidence massively supports something we have to accept it (to a degree - or to get a degree - anyway) and any replacement hypothesis is going to need one hell of a good amount of evidence.

By the way, the variable speed of light bit I mention was that from Maxwell we get c in a vacuum is 1/sqrt(permeability of free space x permittivity of free space) and if we can tweak either of these we can change the value of c. Whether or not saturating the vacuum with HUGE amounts of energy (a la Big Bang levels) would produce such an effect isn't something I can test in a weather office.

Reply 743

rbnphlp

I think they mentioned in this in the documentary but why does multiple universes need to exist?

Reply 744

rbnphlp

Wonders of the solar system[1/5]
Wonders of the solar system[2/5]
Wonders of the solar System[3/5]

Reply 745

defuzion

do protons decay? ive heard mixed views

Reply 746

boromir9111

defuzion

do protons decay? ive heard mixed views

http://en.wikipedia.org/wiki/Proton_decay

"In the Standard Model, protons, a type of baryon, are theoretically stable because baryon number is conserved. Therefore protons will not decay into other particles on their own, because they are the lightest (and therefore least energetic) baryon."

Reply 747

Choccy94

I heard that protons can decay to make beta positive radiation.

*Shrugs* I'm not sure.

Reply 748

trm90

I just had a special relativity exam. It sucked! Definitely not taking a relativity module again.

I have a quesiton though - can someone tell me if special and general relativity are actually that related? Like, say I took a General Rel. & Black Holes module... is that going to incorporate some aspects of special rel into it?

Reply 749

Stef90

trm90

They are related, as in special relativity only works for inertial frame of references. From what I've head/seen G.R. is very mathematical/challenging so if you didn't enjoy the simpler case, then yeah I wouldn't recommend it :p:

Reply 750

suneilr

The main difference between SR and GR is the metric used. SR uses the Minkowski metric which is basically a flat space-time. GR uses a more general metric which includes a curved spacetime.

Reply 751

boromir9111

suneilr

The main difference between SR and GR is the metric used. SR uses the Minkowski metric which is basically a flat space-time. GR uses a more general metric which includes a curved spacetime.

I'm just studied up to A2 physics......planning to study maths at uni this September. How would you go about explaining General relativity and special relativity to me? :smile:

Reply 752

trm90

Stef90

Right - I think I'll avoid it then. It sucks cause mathematically rigorous physics is my favourite kind, but I'll live...

One more question. Has anyone here done a lot of stuff on galaxies? I'm debating whether or not to take a module on Galaxies and the Universe next year. So far I know that the rest of the astro modules (like Stellar Evolution or Jovian Planets) aren't very mathematical at all, but I figure galaxies might be (plus, they're cool) - I know for a fact that typical final year modules on galactic dynamics are mathematical, so yeah I'll be studying them at some point anyway. I know the obvious answer should be 'do modules on stuff you actually like' but unfortunately I'm rubbish at memorising things and am much better off with the mathsy modules!

Reply 753

suneilr

trm90

Right - I think I'll avoid it then. It sucks cause mathematically rigorous physics is my favourite kind, but I'll live...

If you like mathematical rigour, then you should definitely do GR! Which bits of SR did you not like?

Reply 754

trm90

suneilr

If you like mathematical rigour, then you should definitely do GR! Which bits of SR did you not like?

Well as a subject I really like SR, but when it came to applying equations I struggled I guess? Which was so frustrating, because I'd read over the theory, have absolutely no problem deriving the equations and then blanked when I had to do even the simplest of calculations. I didn't study it hard enough probably, but I always feel like I genuinely don't understand cos I can't even use the equations :frown:

That's why I was hoping GR would be slightly different and perhaps less... wordy? The maths behind it looks awesome and I think I'd be okay on that front, but I dunno. Is it harder or easier than you expected?

Reply 755

suneilr

trm90

Well I'm not studying it until next year, but on our syllabus it's pretty much mainly maths. Its mainly about differential geometry and looking at the Einstein Field Equations.

Reply 756

trm90

suneilr

Well I'm not studying it until next year, but on our syllabus it's pretty much mainly maths. Its mainly about differential geometry and looking at the Einstein Field Equations.

Sounds good. I forget that GR is normally saved for the postgrad level modules. Thought it was a third year option at Imperial as my sister told me she did it whilst she was there, but I think she meant just relativity. So unless I do my MSc in physics (which only Imperial seems to offer!? :s-smilie:

) I probably won't get a chance to try it - oh well...

I should probably worry about doing quantum, atoms, solids etc in my second year first though :p:

...

Reply 757

suneilr

trm90

) I probably won't get a chance to try it - oh well...

I should probably worry about doing quantum, atoms, solids etc in my second year first though :p:

...

I think Cam teach GR in third year, not sure about other places. There is quite a bit of background maths to learn first, such as tensor notation, etc, so I think its normally saved for later years.

An MSc is normally specialised in a particular field, but Imperial offers a geral physics MSc for people who want to study physics to a higher level without specialising quite so much.

Yeah definitely concentrate on your second year options :p:

Reply 758

ocelotrevs

Right, I saw this on the BBC website, but I'm sure it's not correct.

A bullet fired horizontally from a gun, and a second bullet dropped by hand from the same height as the gun, will both hit the ground at the same time. The forward motion of an object has no effect on the pull of gravity.

Can anyone prove it?

Reply 759

Stef90

Well assuming the bullet was fired perfectly straight, both bullets have the same vertical acceleration, same vertical initial speed (i.e. 0) and same distance to travel. Hence they will travel the vertical distance in the same time. Then again if we took into account the curvature of the Earth, the times probably won't be the same.