Recent content by chris1969

Thanks ever so much everyone. Can I check my logic/arithmetic please? 1) Energy density of CMB is 4.005 * 10^-14 (Joules per cube metre) 2) Radius of Earth is about 6,371 km 3) Surface area of Earth is about 1.28 * 10^14 metres squared 4) Speed of light is 300,000 m/s Multiplying (1) * (3) *...

Hello everyone I've a question about the cosmic microwave background which my nephew asked me a couple of days ago. How much energy hits the Earth each year from the CMB? I'm assuming here that it is measurable in this way, but apologies if not. Thanks in advance for your help. Chris

Many thanks both. I think I'm getting there, but I have a follow-up question if that is ok. Ned Wright's tutorial re-produces Hubble's 1929 plot of velocity against distance : does this refer to velocity as a layperson would conventionally understand it, or the distance expansion rate. When we...

Hello everyone I've starting to learn about Hubble's law and I have a very simple question. How are the velocities to distant objects calculated from a redshift? I understand the basic principle, that faster objects have longer wavelengths, but I'm not sure about the formula which links the...

Hello everyone I've a question about the "time of the last scattering". My understanding is that this took place about 380,000 years after the big bang, and occurred when the universe cooled sufficiently to allow protons and electrons to form neutral hydrogens atoms. As a result, light was...

Many thanks for this, the rope analogy is very helpful. I've got another couple of questions. Firstly, am I right in thinking that the increase in velocity with distance is because the rope (ie space) is being stretched? My second question is why we were able to identify the acceleration...

Hello everyone I hope you don't mind me asking a real silly question about the original evidence for dark energy. I've been reading about how Type 1a supernovae provided the initial evidence that the expansion of the universe was accelerating. They are able to do this because they are...