Let there be light!

Welcome back, Spherical Cow Moonions! This week unfortunately marks the final episode of Spherical Cow. Thank you so much for supporting our podcast - we hope you have enjoyed the episodes! In this episode we are finishing off our discussion about the history of the universe. We will be talking about the Epoch of Reionization, how scientists actually learn about this era and saying goodbye! Please see an amendment to our discussion below: 1:35 - Sorry I slipped up here! I meant to say that when high energy radiation was emitted by the first starts and, then later, by quasars, the neutral hydrogen was broken apart into positive nuclei and electrons not positive nuclei and ions (the positive nuclei are the ions)! To view our sources please see our website - https://www.podpage.com/spherical-cow/ N.B. Parts of this episode were recorded virtually so the audio quality might be different to normal.

Welcome back, Spherical Cow Moonions! This week we are continuing our journey through the history of the universe and discussing Cosmic Dawn. We will be talking about what Cosmic Dawn is, the properties and formation of the first stars and why they are so interesting! Please see some additions/amendments to our discussion below: 04:45 - To explain this a little further, ATLAS is one of the four detectors located around the Large Hadron Collider ring at CERN. Two protons beams, travelling in opposite directions, collide inside the ATLAS detector. Before this collision, the momentum in a direction perpendicular to the proton beams is 0. Therefore, after the collision, the momentum in a direction perpendicular to the proton beams must also be 0 since momentum is always conserved in collisions. So, if ATLAS detects any particles travelling in a direction perpendicular to the original proton beams there must be other invisible particles (possibly dark matter) travelling in a different direction so that overall the momentum in a direction perpendicular to the original proton beams adds up to 0. 12:32 - Just to clarify, these Population II stars are not just found in the Milky Way but all over the universe! They are often found in 'globular clusters' (spherical groups of stars found within many galaxies). The age of these stars is similar to the age of the Milky Way so Population II stars were formed around 13.6 billion years ago. To view our sources please see our website - https://www.podpage.com/spherical-cow/ N.B. This episode was recorded virtually so the audio quality might be different to normal.

Welcome back, Spherical Cow Moonions! This week we are continuing our discussion about the history of the universe and once again talking about 380,000 years after the Big Bang. We will be discussing the formation of sound waves in the early universe and how studying the imprint of these acoustic oscillations of the Cosmic Microwave Background map can tell us lots of fascinating information about our universe! Please see some additions/amendments to our discussion below: 13:42 - Sorry! I meant to say that you can do some calculations and see if they agree with your observations (i.e your measurements of the size of the ‘spots’ on the cosmic microwave background map). https://www.esa.int/ESA_Multimedia/Images/2013/03/Planck_Power_Spectrum - This is a link to the CMB Power Spectrum graph we discussed in our episode - the measurements were taken by the Planck Satellite To view our sources please see our website - https://www.podpage.com/spherical-cow/ N.B. This episode was recorded virtually so the audio quality might be different to normal and we are sorry about the noisy background in some places!

Welcome back, Spherical Cow Moonions! This week we are discussing the surface of last scattering and cosmic microwave background radiation (CMBR). We will be talking about what CMBR is, how it was discovered and how measurements of CMBR agree with observations of our universe. To view our sources please see our website - https://www.podpage.com/spherical-cow/ N.B. This episode was recorded virtually so the audio quality might be different to normal.

Welcome back, Spherical Cow Moonions! This week we are continuing our journey through the history of the universe and discussing the beginnings of matter! We will be talking about the quark-gluon plasma era and big bang nucleosynthesis. To view our sources please see our website - https://www.podpage.com/spherical-cow/ N.B. This episode was recorded virtually so the audio quality might be different to normal.

Welcome back, Spherical Cow Moonions! This week we are continuing our journey through the history of the universe and discussing inflation and reheating. We will be talking about what inflation is, what are the motivations behind inflationary theory and what happened to the universe immediately after inflation. Please see some additions/amendments to our discussion below: 3.30 - I misspoke here! The fluctuations are actually at a level of one part in 100,000 so they are even tinier than I suggested (but still very important which we will discuss next episode). 5.55 - I have found some contradictory values to how close the density of the universe was to the critical density in the early universe- some websites say it departed from the value by one part in 10^62 whilst others say the density right after the big bang must have been equal to the critical density to 50 decimal places! The main idea is that the initial density of the universe would have been incredibly fine-tuned to the critical density which is why physicists question how the density came so close to this 'special value'. Inflation suggests one solution to this 'fine-tuning' problem. 09.30 - According to inflation, because our whole observable universe was once a tiny part of the early universe, this tiny part was small enough for light to be able to propagate from one side to other, allowing the small section to reach the same temperature. You can say that this region is 'causally connected'. 11.45 - Once again I meant to say the the fluctuations are at a level of one part in 100,000 not 10,000! To view our sources please see our website - https://www.podpage.com/spherical-cow/

Welcome back, Spherical Cow Moonions! This week we are venturing all the way back to the birth of the universe! We will be discussing the big bang, the Planck epoch and the GUT era. To view our sources please see our website - https://www.podpage.com/spherical-cow/ N.B We are sorry about the noisy background!

Welcome back, Spherical Cow Moonions! This week we will be discussing dark energy! We will be exploring the evidence for dark energy, how scientists determined the expansion of the universe is accelerating and what dark energy might be. Please see an addition to our discussion below: 3:22 - To expand on this further, if the universe is closed (has positive curvature) and the shape of space is spherical, this would mean that initially parallel beams of light would converge (like how, when you follow two lines which are parallel at the equator on a globe, they meet up at the north pole). If the universe is flat (has zero curvature) and the shape of space is flat, then parallel beams of light would remain parallel. Finally, if the universe is open (has negative curvature) and the shape of space is hyperbolic (like a saddle) then initially parallel beams of light would diverge (spread apart). To view our sources please see our website - https://www.podpage.com/spherical-cow/ N.B. Parts of this episode were recorded virtually so the audio quality might be different to normal.

Welcome back, Spherical Cow Moonions! This week, we are talking about Dark Matter! We will be discussing why the notion of dark matter was first introduced, what evidence there is for the existence of dark matter and what dark matter could be. Please see an addition to our discussion below: 21:58 - After looking into this more, we are still not sure if we were talking about the same neutrino! If you would like to learn more about neutrinos, please see our podpage for some links to resources. To view our sources please see our website - https://www.podpage.com/spherical-cow/ N.B. Parts of this episode were recorded virtually so the audio quality might be different to normal.

Welcome back, Spherical Cow Moonions! This episode is all about the exciting Particle Physics News from CERN and Fermilab which came out around March-April time. We will be discussing the results published by both organisations and what they mean for the future of physics! If you stay to the end you will also hear an interesting link between muons and special relativity! Please see some additions/amendments to our discussion below: 2:00 - The charm quark is similar to the up quark because of its +2/3 electric charge and the strange quark is like the the down quark because of its -1/3 electric charge. 17:13 - Just to clarify this analogy further, hold the pen vertically in front of you with the tip pointing up. Imagine an axis running through the pen from the tip to the bottom and spin the pen around this axis by holding it straight with one hand and twisting the bottom of the pen with the other. Now, still twisting the pen in this manner, hold the bottom of the pen still and trace out a horizontal circle in the air. By twisting the pen as before but also rotating the tip, the spin axis is now precessing or wobbling. This is analogous to the precession of the muon's spin. 17:52 - If you would like a link to a video which demonstrates how a spinning top wobbles, please go to our podpage. To view our sources please see our website - https://www.podpage.com/spherical-cow/