Thanks to all for your insights, it is much appreciated! @Hornbein - yes that's how I interpreted it and that makes sense to set the CC to a non-zero value to prevent the universe collapsing for an eternal static universe. This is what almost all the sources say. Some said that he didn't like an...
Hi, I've recently developed an interest for the history of the development of cosmology and find it very interesting. The key events I have been reading up on are:
1915 - Einstein's theory of General Relativity was published.
1923 - Hubble discovered a Cepheid variable in the Andromeda...
Thanks I think I can visualise it now. So it’s because they collide exactly edge on with no friction. I guess if ball B collided with some of its radius within ball A’s radius it would impart a force perpendicular to the centre line into A? Is that right? Thanks
Yeh I’m still struggling to visualise it. Ball B changes direction by moving through an angle of 90 degrees yet ball doesn’t changes it angle at all.
If the velocity is at an angle of 30 degrees will there not be a component normal to the line imparted on ball A?
Ah sorry I wasn’t clear. The only way to answer this question is if ball A recoils along the centre line. How do we know it doesn’t have any vertical component after the collision (vertical in terms of the plane of the surface).
Hi,
Here is the problem
What is required to answer this question is two assumptions. Firstly, the component of the momentum normal to the centre line is the same before and after. Therefore, secondly, A must recoil entirely in the horizontal plane. This is the only way to answer this question...
@davenn thank you for taking the time to write such a detailed response!
So it is bad to think of meteoroids having high speeds from the conversion of GPE to KE within Earth’s gravitational field? Their high speeds are from their orbital speeds around the Sun and the direction they strike the...
Ah yes of course it is in eV. Are the only EM radiations that interact with band gap theory just visible and UV then? IR by lattice vibrational excitations and high energy through scattering and ionisation?
I have been looking for an answer as to why lead attenuated gamma so well. It was...
Where did @MeadowZ detailed answer go?
Does anyone know any detailed information about how high energy EM radiation interacts with lead glass that is used to block EM radiation like gamma whilst still being transparent to optical light.
I can only find this article in terms of band...
Hi,
I wanted some clarification on the mechanism for how EM radiation interacts with standard glass, namely IR, visible and high energy (UV and X-ray).
Looking online most sources seem to say the band gap is around 10eV. Since visible light is about 1-3eV visible light will be transmitted.
IR...
Hi,
I was watching a documentary on car crashes and how designs are continually being optimised to keep passengers safe. They were saying how many ‘g’s’ certain crashes were based on crumple zones, seatbelt stretch etc. I was interested to do some number crunching to see how big the...
This is the one from the 2008 Canada meteorite:
https://www.sciencedaily.com/releases/2008/11/081125141602.htm
They quote:
“Hildebrand estimates that hundreds of meteorites larger than 50 grams could have landed since the rock was large and its entry velocity was lower than average. The...
Thanks! Could there be a situation then where an asteroid heads directly towards Earth’s orbital motion then you could get impact speeds greater than 30km/s?
Is it a coincidence that all the impacts I’ve looked at are all pretty much 20km/s impact speed?
Hi,
I’m interested to understand some of the mechanics involved in meteorites that originate from the asteroid belt. I have researched several including the Barringer and the one in Northern Canada in 2008 that was caught on multiple CCTV cameras. They all have very similar velocities before...