What is the limit to space propulsion systems? why cant a spacecraft continuously accelerate to reach enormous speeds? |
- What is the limit to space propulsion systems? why cant a spacecraft continuously accelerate to reach enormous speeds?
- Would a field that reduces your inertia violate any important laws of physics?
- There's a massive ball of water floating in space. How big does it need to be before its core becomes solid under its own pressure?
- What exactly is radiation?
- How can the auto-focus feature on my cellphone's camera tell when a shot is in focus or not in focus?
- What exactly are polynomials used for?
- (Physics and Chemistry) In density functional theory, the KS formulation derivation usually involves a Lagrange multiplier portion, what is the purpose of this step?
- How are the rotational speeds of planets determined?
- Virtual particles annihilation, where are the photons?
- Can you identify the source of a radio transmission using trigonometry and the location of two known radio receivers? From novel 'All the Light you Cannot See'.
- If you hold a spring compressed for long enough, will it eventually hold that shape (ex. not uncompress when the force is removed)? If so, what has happened at a molecular level?
- What is the reason for so few chemicals are liquid at room temperature?
- Does a sub-atomic particle travelling in its own field produce a _wake_ in that field? Or is that too simplistic?
- I made a very acidic PBS solution, how?
- Where does our atmospheric oxygen come from?
- What would happen if 2 persons have the same public key for encryption? How is it prevented?
- How can non-ionizing radiation affect matter like the receptors in my eye or chlorophyll?
- If Earth's gravity suddenly desappeared, would my body feel the gravitational pull from the Sun?
| Posted: 07 Jun 2016 12:40 PM PDT the way i understand it, you cant really slow down in space. So i'm wondering why its unfeasible to design a craft that can continuously accelerate (possibly using solar power) throughout its entire journey. If this is possible, shouldn't it be fairly easy to send a spacecraft to other solar systems? [link] [comments]  |
| Would a field that reduces your inertia violate any important laws of physics? Posted: 07 Jun 2016 10:35 AM PDT I was thinking about some sort of energy field that reduces the inertia of a body or area. I was wondering if this would violate any laws of physics. Specifically it wouldn't change gravity, so you couldn't violate the conservation of energy by building an overbalanced wheel. The part I have questions about is conserving kinetic energy. It would also have to speed you up and slow you down as you turned it on and off to conserve kinetic energy. But does this fly in the face of relativity? Since as far as I know, you have different amounts of kinetic energy depending on the location of the observer, right? You wouldn't be able to exceed lightspeed as that would either require a field that reduced your inertia to 0, or still require infinite energy. So I suppose my question is would a field that reduced your inertia conserve kinetic energy if you sped up and slowed down as it increased and decreased in strength, or would that still break conservation of energy? [link] [comments]  |
| Posted: 08 Jun 2016 03:31 AM PDT So under the assumption that - given enough pressure - liquid water can be compressed into a solid, lets imagine we have a massive ball of water floating in space. How big would that ball of water have to be before its core turned to ice due to the pressure of the rest of the water from every direction around it? I'm guessing the temperature of the water will have a big effect on the answer. So we'll say the entire body of water is somehow kept at a steady temperature of 25'C (by all means use a different temperature - i'm just plucking an arbitrary example as a starting point). [link] [comments]  |
| Posted: 08 Jun 2016 12:29 AM PDT
i have soo many questions. I want to become a physicist and have no clue to radiation. So wanted to start somewhere. [link] [comments]  |
| Posted: 07 Jun 2016 05:09 PM PDT It will sometimes take a moment and cycle through various focus levels, but it will very often settle on a good focus level. I can touch the screen to tell it where I want it to focus, and it will in most cases manage to do this. I don't understand how the computer can tell what is in focus and what is not in focus. [link] [comments]  |
| What exactly are polynomials used for? Posted: 07 Jun 2016 05:59 AM PDT So I have been learning about polynomials in school for the past couple of weeks (graphing them) and our teacher told us that we won't need to actually use them later in life. So what exactly are they used for? [link] [comments]  |
| Posted: 07 Jun 2016 04:50 PM PDT So I can follow the Hohenberg Kohn Theorems E = E[n(r)] and E0[n(r)] = min <H> over n(r) In a lot of derivations of the Kohn Sham equations, I see some steps involving the Lagrange multiplier method, but since we do not know how to write <T> explicitly as a functional of the density, it doesnt work out. This is done for both an electron non-interacting and interacting systems to show that they have the same form. The related SE equations are the KS equations.
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| How are the rotational speeds of planets determined? Posted: 07 Jun 2016 03:13 PM PDT I've heard about how it can take some planets longer to rotate once than complete their orbit, but how was this figured out? [link] [comments]  |
| Virtual particles annihilation, where are the photons? Posted: 07 Jun 2016 04:39 PM PDT I keep reading about pairs of particles and their anti particle being created then annihilating each other soon, so that the conservation of mass and energy is preserved. But, won't such annihilation also give off photons? For example, an electron and positron will give a photon. So, why isn't empty space very bright? [link] [comments]  |
| Posted: 07 Jun 2016 07:44 PM PDT In Anthony Doerr's 'All the Light you Cannot See' the main character calculates the location of radio broadcasts using trigonometry. The character using two radio receivers is able to track the location of transmissions of illegal radio activity of members of the French resistance in german occupied france during WW2. The characters then proceed calculate with trigonometry the location of the radio transmission zero in on the source and eliminate the radio operators. Is this pure fiction or is something like this possible. [link] [comments]  |
| Posted: 07 Jun 2016 02:54 PM PDT |
| What is the reason for so few chemicals are liquid at room temperature? Posted: 07 Jun 2016 02:08 PM PDT Most liquids we see are water based. What is the reason there are so few non water based liquids? because there are lots of solids and lots of gasses but few liquids? Is it because the range that chemicals are liquid is smaller than the range for them to be gas/solid and so whatever the temperature we would only find a few liquids? if so why is the range for liquid so small? Is it because most things are liquid at a certain temperature range and we just happen the be at a temperature that is anomalous? if so why are most things liquid at whatever temperature is the normal liquid temp? edit: eugh this title. [link] [comments]  |
| Posted: 07 Jun 2016 02:35 PM PDT |
| I made a very acidic PBS solution, how? Posted: 07 Jun 2016 06:27 AM PDT I do small dumb work for a lab and I had to make 1L of 20x PBS solution. The "recipe" I used was 4g of KCl, 4g of KH2PO4, 160g of NaCl and 43.2g of Na2HPO4, in mq water. The PH turned out to be 3.5! A collegue gave me "another recipe", which turned out to be the exact same thing, same masses and compounds, but with Na2HPO4 - 7H2O instead of just Na2HPO4. I made that solution and the PH was 6.80, so totally normal according to my collegues. Now, I thought hey, the issue must have been that I put way too much Na2HPO4 since it wasnt the hydrated mass, but apprently Na2HPO4 is "slightly basic", so the Ph should've been too basic, not too acidic... Right? Am I fundamentally not understanding acids and bases, or did the issue have to come from something else, like using the wrong compound? Thanks a lot [link] [comments]  |
| Where does our atmospheric oxygen come from? Posted: 07 Jun 2016 01:21 PM PDT Chemistry major here. I'm currently doing a literature study on manganese for a boring-ish group project I've been assigned, and my focus is on the biochemical properties of manganese. Now, there's also a small presentation to be given about the project. During a practice talk with our supervising professor, I mentioned that virtually all atmospheric oxygen is produced by the (manganese-containing) Photosystem II enzyme complex, which is present in plants, bacteria and archaea. The professor totally shot me down on this statement and said that I shouldn't include such populistic remarks in my bit. However, he refused to tell me why my remark was incorrect. So, in short: if the Photosystem II enzyme complex isn't responsible for most of our atmospheric oxygen, what other things are out there? [link] [comments]  |
| What would happen if 2 persons have the same public key for encryption? How is it prevented? Posted: 07 Jun 2016 03:09 PM PDT What would happen if 2 persons have the same public key for encryption, assuming same algorithm? How is that case prevented? Is it feasible to collect and build tables of known keys? I know these questions are rather general, but right now I am not sure where and how to be more specific. [link] [comments]  |
| How can non-ionizing radiation affect matter like the receptors in my eye or chlorophyll? Posted: 07 Jun 2016 07:00 AM PDT Whenever I have the discussion about if EM radiation from phones can be damaging I use the argument that the energy of the photons is to low to affect our cells, it can only be converted to heat. I know that blue light has enough energy to free electrons form a metal surface, but not green or red. How can we perceive these colors when the energy is so low? And is there a possibility that EM radiation can bring changes to our cells? [link] [comments]  |
| If Earth's gravity suddenly desappeared, would my body feel the gravitational pull from the Sun? Posted: 07 Jun 2016 02:57 PM PDT |
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