Recent content by SteveDC

Applying GR should give the same conclusion though shouldn't it? If photons have passive mass and therefore have active mass they are able to curve space.

As I understand a photon has zero rest mass (as far as we can tell) but it does have a passive gravitational mass in order for it to be able to respond to gravity. But I've been shown that passive gravitational mass should be equal to active gravitational mass, and if this is true and photons...

I'm learning about beta decay and as I understand in beta decay we get: neutron → proton + electron And since all these have spin 1/2 we have that the conservation of angular momentum is not conserved. The neutrino with spin 1/2 is proposed to also exist in the process to solve this so that...

Has the expansion of the Universe caused less clustering? If the expanding Universe is causing volume of space to increase, to me it would make sense that clustering would be impacted as a result of this.

Hi, I'm doing a project on galaxy clustering and in a lot of papers where they list the cosmological parameters they've used, they list σ8 and ns. Can anyone quickly tell me what these parameters are referring to? Thanks

Great, thanks. And cheers for the tip, the holes method is much quicker!

I have the solution for this problem but don't understand it. 1. Homework Statement Use Hund's rules to calculate the ground state of erbium with electron configuration [Xe]4f126s2 Homework Equations Hunds Rules: 1. Maximise S (within Pauli) 2. Maximise L (within Pauli) 3. Min J (for...

Hi, ignoring Dark Matter, I was wondering on average what portion of a galaxies mass is stars and what portion is gas. I am guessing it fluctuates with redshift so for arguments sake let's say we are only talking about galaxies at z~0.5 Thanks Steve

Currently reading Peter Coles, Cosmology a very short introduction. There is a bit I don't understand. In a section discussing Friedmann Models, and how going on the cosmological principle density of the universe is the same in every place, and therefore space must be warped in the same way at...

Interesting - THanks again.

Ah I see, thanks. Is this what leads to the Quantum treatment of statistical mechanics? Since I'm assuming the particles are in fact indistinguishable based on QM and the classical approach of assuming they're distinguishable would lead to an overcounting of microstates, which in turn affects...

Okay, if then the system has large number 'N' of particles, does a point in phase space correspond to the coordinates and momenta of a single particle in that system and a microstate is a 'superposition' (not sure if that's the right word!) of all the points in phase space for that particular...

Currently learning about Statistical Mechanics and just wanted to check my understanding. Am I right in saying that a point in phase space is just a specific microstate of the system?

The context given is in the decay of Na22 nuclide and I just don't understand how the positron created could ever collide with an electron without annihilation occurring.

Some notes that I have for a lab module I am doing at University, its just a folder of pre lab notes not like a published source or anything