- AskScience AMA Series: I'm Dr. John Troyer, Director of the Centre for Death and Society at the University of Bath and I'm here to talk about death, dying, dead bodies, grief & bereavement, and the future of human mortality. Ask Me Anything!
- How far can we travel away from Earth?
- How active a radioisotope source do you need to get clearly visible (to the naked eye) light from a scintillator?
- How do individual pixels come together together to form images?
- Gamma ray bursts can travel faster than light in a jet medium?
- If someone receives a donated organ, can that organ be donated again when they pass?
- How do some Modified Release medication have lower dosage requirements as compared to the instant release medication?
- Do other animals understand and comprehend photos/videos?
- Does the volume of water on earth fluctuate from day to day?
- Can you make supersonic incompressible flow?
- Why are some galaxies names things like "Andromeda" and "Sombrero" while others are referred to as "NGC 3923" and "M82"?
- Is there an inherent physical reason why Earth's seasons occur over the same period of time as its year?
- Do male bees know they will die after mating?
- Why do we need spinors?
- Do sugared soft drinks contain emulsifiers to keep the sugar in solution?
| Posted: 27 Sep 2019 04:00 AM PDT Hello Reddit, my name is Dr John Troyer and I am the Director of the Centre for Death and Society at the University of Bath. I co-founded the Death Reference Desk website (@DeathRef), the Future Cemetery Project (@FutureCemetery) and I'm a frequent commentator for the BBC on things death and dying. My upcoming book is Technologies of the Human Corpse (published by the MIT Press in 2020). I'll be online from 5-6pm (GMT+1; 12-1pm ET) on Friday 27th September to answer your questions as part of FUTURES - European Researchers' Night 2019. [link] [comments]  |
| How far can we travel away from Earth? Posted: 26 Sep 2019 07:03 PM PDT I'm taking a Cosmology class right now, and I recently watched this kurzgesagt video about our absolute boundary in the universe. So far in class we've mostly just been going over the expansion of the universe, so I tried to justify the assertion in this video to myself: we cannot travel outside of our local group. The Hubble constant at the current time is 70 kilometers per second per megaparsec. I set up an equation where the change in distance, dx, is equal to the hubble constant times the distance times the change in time, dt. Solving the differential equation, you get that the final distance is equal to about 1.03 times the initial distance over the course of 500 million years. Something about 3 mpc away (the diameter of the local group) would not even increase in distance by a megaparsec. At half the speed of light, you could travel about 77 mpc in this time. This is ~25 times the diameter of the local group. I know that the Hubble parameter changes in time, but my textbook seemed to suggest that it would not change in any meaningful way over the course of 500 myr. Even if it increased by two orders of magnitude (I tried this by just having it start at two orders of magnitude higher), the distance is still well within travel distance. Where is Kurzgesagt getting this from, then? I feel like I'm missing something entirely or that I'm wrong about the evolution of the Hubble parameter in time. [link] [comments]  |
| Posted: 27 Sep 2019 02:11 AM PDT |
| How do individual pixels come together together to form images? Posted: 26 Sep 2019 08:13 PM PDT |
| Gamma ray bursts can travel faster than light in a jet medium? Posted: 26 Sep 2019 12:38 PM PDT https://www.sciencedaily.com/releases/2019/09/190924152835.htm That article is way over my head, can someone explain? [link] [comments]  |
| If someone receives a donated organ, can that organ be donated again when they pass? Posted: 26 Sep 2019 12:27 PM PDT |
| Posted: 27 Sep 2019 02:14 AM PDT First of all - is there a difference between Extended Release, Substained Release & Modified Release? Second - the question in the title But this is not true for all medication. For e.g. Gliclazide Modified Release is prescribed at a much lower dose than the instant release one https://www.ncbi.nlm.nih.gov/pubmed/12076188
How come lesser dosage of the modified release gives same efficacy as the instant release? Also seen this with other meds like Indapamide, Zolpidem etc. [link] [comments]  |
| Do other animals understand and comprehend photos/videos? Posted: 26 Sep 2019 12:50 PM PDT |
| Does the volume of water on earth fluctuate from day to day? Posted: 26 Sep 2019 12:30 PM PDT |
| Can you make supersonic incompressible flow? Posted: 26 Sep 2019 11:51 AM PDT It seems like just increasing pressure in a reservoir and having a small outlet would be sufficient to cause supersonic incompressible flow. (Say the flow is water). This would work through the Bernoulli equation and area*velocity=constant which hold for incompressible flow. [link] [comments]  |
| Posted: 26 Sep 2019 08:40 AM PDT |
| Posted: 26 Sep 2019 08:41 AM PDT |
| Do male bees know they will die after mating? Posted: 26 Sep 2019 04:14 AM PDT |
| Posted: 26 Sep 2019 05:19 AM PDT I understand that there is some important connection between spin and the groups SU(2) and SO(3). It's often pointed out that SU(2) double covers SO(3), and that the Pauli matrices form a basis for the Lie algebra su(2) (up to a factor of i). But I'm having trouble understanding the connection. As I understand, SU(2) is the symmetry group of spinors (as diagrams like this one point out - you need a double-covering of SO(3) in order to cover all spinor-space symmetries). This is why this group is so important in the theory of spin. A question that just occurred to me is why the Pauli matrices happen to form a representation of the Lie algebra su(2); does the algebra of observables of a system always have to be some representation of the system's symmetry group Lie algebra? But we can put that question to one side. I'm especially confused because the theory of spin in quantum mechanics is usually presented as (a generalised version of) the theory of orbital angular momentum. The commutation relations between spin observables are derived in terms of the canonical commutation relations of linear position and momentum. So then, could someone connect this intro QM exposition of spin to the groups SU(2) and SO(3)? I'm also vaguely aware of Clifford algebra representations of spin. As far as I can tell spin states are represented by rotors which happen to double-cover SO(3). But that just kicks the can down the road: why should rotors represent angular momentum? Apologies if this question is poorly formed or seems scattered - that's because it is. It's hard to form the question exactly because I don't fully understand its subject matter yet. So any answer, even partial, would be greatly appreciated. [link] [comments]  |
| Do sugared soft drinks contain emulsifiers to keep the sugar in solution? Posted: 26 Sep 2019 06:22 AM PDT I heard this random factoid as part of a larger argument against "big food", that soft drinks are supersaturated with sugar so they must also contain an emulsifier, lest the sugar form crystals. I know citrus flavored sodas, e.g. Mtn Dew, Sun Drop, Squirt, contain an emulsifier to keep the citrus oil-based flavors from seperating but I was suspicious of the sugar emulsifiers claim. EDIT TO ADD If soft drinks don't contain such a product, is there even a foodsafe additive that would allow more sugar to be dissolved in water? [link] [comments]  |
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