Can there be an orbit around a black hole in which the apoapsis is above the photon sphere, but the periapsis is below the event horizon?

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• Can there be an orbit around a black hole in which the apoapsis is above the photon sphere, but the periapsis is below the event horizon?
• Is the Unit Circle and the Complex Plane related at all?
• What causes viruses to take different structures? As an example Ebola is a string like structure, where as the flu is spherical.
• Would it be possible to create a cutter out of air by funneling huge amounts of wind through a tiny opening?
• If the planet was shaped like a donut, how would gravity work in the middle?
• Why do we have two sets of teeth in our lifetime?
• How exactly were the first forged iron tools/weapons made without iron tools like hammers, anvils, tongs, etc.?
• Did scientists in the 19th century really think that the sun and other stars reflected light from another source?
• If the universe is constantly expanding, then are we and all the other planets also expanding?
• Recent advances in Navier-Stokes equations?
• Would it be possible to make elements such as iron and copper in particle accelerators/colliders?
• Why is it that you cannot feel the inside of your body, yet when you drink a hot or cold drink you can feel it rush through you?
• Why do we laugh when we get tickled?
• Why does leaving Earth require an "escape velocity" rather than an "escape force"? What happens that requires the rocket to be moving at a certain speed for a successful launch?
• Can nuclear power still be achievable without uranium?
• Travel Between Earth and Sun-Earth Lagrange Points 4 and 5: energy requirements?
• Are reptilian brains significantly different to mammals'? Can reptilians learn, or feel emotions?
• Why can some animals, like snakes, eat only once and not need to again for months whilst animals like humans need to feed multiple times a day?
• We say that the Universe is expanding. But what would be the difference in saying that we are actually compressing? Wouldn't that explain a lot of things that expansion does not?
• Why don't you sneeze while sleeping?
• Are sound waves affected by friction?
• When a woman is pregnant, does the baby have a sense of direction? (For example, does the baby feel if the mother were to be lying down sideways as opposed to standing up straight)

Can there be an orbit around a black hole in which the apoapsis is above the photon sphere, but the periapsis is below the event horizon? Posted: 27 Oct 2017 09:16 AM PDT submitted by /u/Weltaum [link] [comments]

Is the Unit Circle and the Complex Plane related at all? Posted: 28 Oct 2017 06:55 AM PDT When learning trigonometry, the idea of the unit circle was the main mechanism to describe the effects of angles and the sine and cosine functions. Now that I'm learning about Q.M. and Euler's formula, etc, it's pretty evident that the imaginary plane and trigonometric functions are intertwined. How did these two sort of distinct ways to look at trigonometric functions (I.e the unit circle vs complex plane) come to be? Did one come from the other, or are they related? Is there a reason euler's formula and complex relations baren't taught in tandem with trigonometry? Thanks in advance! submitted by /u/throwaway3141598 [link] [comments]

What causes viruses to take different structures? As an example Ebola is a string like structure, where as the flu is spherical. Posted: 27 Oct 2017 06:34 PM PDT And does the structure change the effects, like symptoms, transmission,etc. submitted by /u/z00b_ [link] [comments]

Would it be possible to create a cutter out of air by funneling huge amounts of wind through a tiny opening? Posted: 27 Oct 2017 05:50 PM PDT Illustration of what I'm thinking about submitted by /u/andreasdagen [link] [comments]

If the planet was shaped like a donut, how would gravity work in the middle? Posted: 28 Oct 2017 06:12 AM PDT submitted by /u/Shanendipitous [link] [comments]

Why do we have two sets of teeth in our lifetime? Posted: 27 Oct 2017 03:53 PM PDT submitted by /u/SpikyMilk [link] [comments]

How exactly were the first forged iron tools/weapons made without iron tools like hammers, anvils, tongs, etc.? Posted: 27 Oct 2017 08:07 PM PDT This question is inspired by the recent primitive technology video showing the building of a natural draft furnace: https://www.youtube.com/watch?v=u7wAJTGl2gc It got me thinking on a quandary: you need iron tools to make iron tools (and by this I mean, you need a very good and strong iron hammer to hammer away impurities in molten/hot iron and to shape it you need tongs and an anvil to hammer against. so how did the first people to break this chicken and egg problem do it? Did they use stone tools? thanks! submitted by /u/lingben [link] [comments]

Did scientists in the 19th century really think that the sun and other stars reflected light from another source? Posted: 28 Oct 2017 06:53 AM PDT In Thomas Dick's Celestial Scenery (1838 - 1848 editions) he states in the introduction, referring to stars: Do they shine with borrowed light, or with their own native lustre? and later in his 1869 edition of The Christian Philosopher he says The immense distance at which the nearest stars are known to be pplaced proves that they are bodies of a prodigious size, not inferior to our own sun, and that they shine not by reflected rays, but by their own native light. suggesting that at some point between 1848 and 1869 the idea that the sun and other stars might be reflecting light was shown to be incorrect. Was this something that scientists in the 1800's thought might be how the sun generated its light or was this an aberration of christian scientists like T. Dick? submitted by /u/hasbrochem [link] [comments]

If the universe is constantly expanding, then are we and all the other planets also expanding? Posted: 27 Oct 2017 05:21 PM PDT Similar to putting a drawing on a balloon and blowing it up in size? submitted by /u/keptsecret1 [link] [comments]

Recent advances in Navier-Stokes equations? Posted: 27 Oct 2017 04:20 PM PDT Hi all, I'm just wondering if anyone knew of any current research that's looking into exact solutions to the full Navier-Stokes equations? Also, has any progress been made on solving the full NS equations at all? I know about reducing them to something solvable by considering the Reynolds number, but apart from numerically, it's my understanding that we haven't solved them yet. submitted by /u/KieranMontgomery [link] [comments]

Would it be possible to make elements such as iron and copper in particle accelerators/colliders? Posted: 27 Oct 2017 06:47 PM PDT And how much of these elements would you be able to create? submitted by /u/BHjr132 [link] [comments]

Why is it that you cannot feel the inside of your body, yet when you drink a hot or cold drink you can feel it rush through you? Posted: 27 Oct 2017 06:18 PM PDT submitted by /u/BagelsOverBread [link] [comments]

Why do we laugh when we get tickled? Posted: 27 Oct 2017 04:28 PM PDT submitted by /u/direvoid [link] [comments]

Why does leaving Earth require an "escape velocity" rather than an "escape force"? What happens that requires the rocket to be moving at a certain speed for a successful launch? Posted: 28 Oct 2017 12:48 AM PDT submitted by /u/MigBird [link] [comments]

Can nuclear power still be achievable without uranium? Posted: 27 Oct 2017 02:10 PM PDT I'm sorry if this is a bad question but I've recently been looking into nuclear power energy and it seems very efficient but the problem is that uranium isn't the safest element of them all. From what I've read, the reason uranium is used is that it's the easiest element to undergo nuclear fission (the splitting of atoms). My question is can we use another element that, like uranium is easy to undergo nuclear fission but unlike uranium is fairly safe (meaning a potential nuclear meltdown that won't spread radiation)? If so, why haven't we tried it? submitted by /u/Execute-Order-66 [link] [comments]

Travel Between Earth and Sun-Earth Lagrange Points 4 and 5: energy requirements? Posted: 27 Oct 2017 11:28 PM PDT From Wikipedia: Earth trojan The orbits of any Earth trojans could make them less energetically costly to reach than the Moon, even though they will be hundreds of times more distant. Can somebody confirm for me whether or not this line from Wikipedia is correct? Also, what would be the most energy-efficient way for a spacecraft to travel from Earth to either of those two locations? If I remember correctly, there have been some spacecraft sent on heliocentric orbits, but I am not sure if any have gone specifically to Sun-Earth L4/L5. submitted by /u/DDRussian [link] [comments]

Are reptilian brains significantly different to mammals'? Can reptilians learn, or feel emotions? Posted: 27 Oct 2017 05:14 PM PDT submitted by /u/jupalipa [link] [comments]

Why can some animals, like snakes, eat only once and not need to again for months whilst animals like humans need to feed multiple times a day? Posted: 27 Oct 2017 01:14 PM PDT submitted by /u/Velteau [link] [comments]

We say that the Universe is expanding. But what would be the difference in saying that we are actually compressing? Wouldn't that explain a lot of things that expansion does not? Posted: 27 Oct 2017 09:03 PM PDT I mean, it's a question of relation, isn't it? To me as a layman who loves space and science, it is obvious that somehow, in ways I do not understand or pretend to be able to express, whatever "we" are, fell into a black hole, and that the thing we are experiencing as expansion is in fact our polar perception of things shrinking as we close in on the event horizon. Wouldn't this explain, well, everything? It would explain heat death pretty neatly, wouldn't it? submitted by /u/tjackpundarn [link] [comments]

Why don't you sneeze while sleeping? Posted: 27 Oct 2017 01:30 PM PDT submitted by /u/blakemorris02 [link] [comments]

Are sound waves affected by friction? Posted: 27 Oct 2017 10:12 AM PDT Will a sound that is amplified over a smooth frictionless surface travel further than the same sound traveling over a "rough" surface? submitted by /u/The-Jolly-Roger [link] [comments]

When a woman is pregnant, does the baby have a sense of direction? (For example, does the baby feel if the mother were to be lying down sideways as opposed to standing up straight) Posted: 27 Oct 2017 06:08 AM PDT I was having a conversation last night with my wife (who is 4 and half months pregnant) about baby movements in the stomach. I know that the baby can feel some of her movements and can definitely tell when she's moving around or not. But I was wondering if the baby can feel any sense of direction in the womb (if my wife was upside down vs. standing up straight, would the baby notice a difference?) submitted by /u/nayan742 [link] [comments]

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