- Proxima Centauri, the closest star to the Sun is 4.85 billion years old, the Sun is 4.6 billion years old. If the sun will die in around 5 billion years, Proxima Centauri would be already dead by then or close to it?
- Can gravity set up concentration gradients in a solution?
- How are nuclear arms/weapons safely created and stored to prevent accidents related to arming and detonations?
- Why is equipartition of energy expected in the modes of a resonant cavity? And why this should model a solid radiator?
- If trees get 95% of their mass from Carbon do Fruits and vegetables also mostly carbon?
- Why are microplastics bad, and why should I care about them?
- When smartphone batteries lose some of their capacity over the years, do they take the same time to charge?
- Alpha particles are released from nuclei because of how stable they are. Fe has the highest binding energy per nucleon, so why aren't Fe nuclei emitted radioactively?
- Was earth ever completely covered in trees?
- Are plastic jerrycans for diesel formulated differently than plastic jerrycans for gasoline?
- Do all observers agree on the velocity of the Hubble flow at a given position?
- Do bears look forward to hibernating?
- Why do lasers have such low wall plug efficiency?
- Are audiobooks ‘cheating’? Do we get same benefits as reading?
- Are there seasons along the equator?
- Does hormonal birth control stop implantation of fertilized eggs? What about the copper IUD?
- As permafrost melts, revealing ice age animals, is the bacteria in their bodies a danger to humans?
- What does respiratory depression mean, exactly?
- Can Plants Self-Sustain Indefinitely?
| Posted: 28 Oct 2019 04:24 PM PDT |
| Can gravity set up concentration gradients in a solution? Posted: 29 Oct 2019 08:17 AM PDT If we take a perfectly mixed salt solution and leave it at rest indefinitely so the only mixing process is molecular diffusion, will the solution remain perfectly mixed or will the force of gravity set up a (small) vertical concentration gradient? [link] [comments]  |
| Posted: 28 Oct 2019 09:28 AM PDT How do we know that nuclear arms in storage silos/warehouses are 'safe' in storage? Is there a near-zero% chance for them to accidentally go off? Thinking of every aspect of humanity and how, somewhere along the lines of bureaucracy, there's a human being slacking/messing up - doesn't that also apply for nuclear development of weapons? While citizens can do nothing to help or prevent; are nuclear bombs and arms just 'safe' with their creation/storage methods to disallow accidents that could annihilate the world many times over? [link] [comments]  |
| Posted: 28 Oct 2019 06:57 PM PDT I think the answer for this may be straightforward, but I don't see anywhere that explains this from the scratch: A large resonant cavity with a small hole is used to approximate an ideal black body. I understand the conditions for the modes inside the cavity. But there are two points that aren't clear to me: 1) I don't understand why it was considered that the energy should be equipartitioned between those modes. Because I don't see a reason why they couldn't be independent. At least not if it was ideally reflecting body inside. In that case, just like in ideal vibrating stings, there could be no exchange of energy between the modes and the spectrum of the light inside it would be just like the spectrum of the light entering it. I think the story has to do with the body not being perfectly reflecting and being in equilibrium with the modes inside the cavity. But even then: Why couldn't it just stay in equilibrium with the modes that has already being formed by the light that entered the cavity? Is the equipartition being mediated by the material portion of the cavity? 2) Why exactly does particular solution serves as a model for entirely solid radiators? Does this EM field modes exist inside opaque materials? [link] [comments]  |
| If trees get 95% of their mass from Carbon do Fruits and vegetables also mostly carbon? Posted: 28 Oct 2019 02:28 PM PDT A video from Veritasium recently stated trees get most of their mass from carbon. So do Fruits, vegetables, seeds, leaves also get most of their mass from carbon? I'm sure it's more water than the stalks/trunks. [link] [comments]  |
| Why are microplastics bad, and why should I care about them? Posted: 28 Oct 2019 05:41 PM PDT |
| Posted: 28 Oct 2019 12:10 PM PDT |
| Posted: 28 Oct 2019 03:15 PM PDT That is to say, He's binding energy per nucleon is much higher than other similarly sized nuclei, making it low energy and thus energetically favorable to release alpha particles. Further, they can quantum tunnel, making it possible for their release. Why can't Fe, the most stable nucleus on a per-nucleon basis, be emitted in a manner similar to alpha decay? Is it just unlikely because it has an enormous coulomb barrier? Binding energy per nucleon curve: http://clay6.com/mpaimg/p2.jpg [link] [comments]  |
| Was earth ever completely covered in trees? Posted: 28 Oct 2019 02:29 PM PDT The kid I babysit was wondering if the earth was once covered in forests; I just want to get the right answer for him. :) thanks! [link] [comments]  |
| Are plastic jerrycans for diesel formulated differently than plastic jerrycans for gasoline? Posted: 28 Oct 2019 10:43 AM PDT |
| Do all observers agree on the velocity of the Hubble flow at a given position? Posted: 28 Oct 2019 05:58 PM PDT I understand that the Milky Way is moving something like 600 km/s relative to the local Hubble flow. I suppose this means there must be some velocity at our position and time that is at rest relative to the Hubble flow. My question is: will observers moving near the speed of light agree and will distant observers agree? More broadly: for a given position and instant, is there a velocity that is at rest relative to the Hubble flow that all observers and frames and reference can agree on? [link] [comments]  |
| Do bears look forward to hibernating? Posted: 28 Oct 2019 08:42 AM PDT |
| Why do lasers have such low wall plug efficiency? Posted: 28 Oct 2019 08:54 AM PDT It seems that laser efficiency can range from a few percent to ~60%, but most seem to be on the lower end of the spectrum. Where do these large inefficiencies come from, and how are lasers made more efficient? [link] [comments]  |
| Are audiobooks ‘cheating’? Do we get same benefits as reading? Posted: 28 Oct 2019 09:19 AM PDT I always feel bad listening to an audiobook because I was taught that it was 'cheating' and that reading was far better in terms of learning vocabulary, retaining information and general learning. Is this true? [link] [comments]  |
| Are there seasons along the equator? Posted: 28 Oct 2019 03:40 PM PDT Or does the weather remain overall consistent from month to month every year? [link] [comments]  |
| Does hormonal birth control stop implantation of fertilized eggs? What about the copper IUD? Posted: 28 Oct 2019 11:47 AM PDT I've heard an argument that birth control is "bad" (I understand this is a value judgment, not a scientific assessment) because it can prevent the implantation of a fertilized egg. However, upon researching this claim, I can't seem to find conclusive evidence one way or the other. Some people seem to think it could happen, some people think it doesn't, and others think it needs to be researched more. A relatively recent NYT article says that hormonal birth control does not seem to prevent implantation but that a copper IUD does. Is there any update on this research? Or more scientific papers I could read about it? Thanks! [link] [comments]  |
| As permafrost melts, revealing ice age animals, is the bacteria in their bodies a danger to humans? Posted: 28 Oct 2019 07:54 AM PDT Or would water molecules (if any) that froze inside them destroy the genetic material making them inert? If it could be a danger, how dangerous? [link] [comments]  |
| What does respiratory depression mean, exactly? Posted: 28 Oct 2019 08:26 AM PDT I know that opioids reduce the sensitivity to CO2 in the medulla oblongata. But does respiratory depression mean that you just cannot breathe or that you ‚forget' to breathe while you're unconscious or sleeping? Because the phrenic nerve itself is not affected by opioid agonists, I think. Or am I not getting something? Thank you [link] [comments]  |
| Can Plants Self-Sustain Indefinitely? Posted: 28 Oct 2019 08:03 AM PDT I've seen a thing about a guy having a plant in a sealed vase for more than 40 years and he hasn't watered it in 40 years because it creates a self-sustaining ecosystem. Does this mean that, theoretically, in perfect conditions a plant could survive for an indefinite period of time? [link] [comments]  |
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