Physics

I was trying to get a lower roundtrip delta-V for lunar missions by flying directly to the lunar surface rather than going first into lunar orbit then descending, the "direct descent" mode. Here's a list of delta-V's of the Earth/Moon system: Delta-V budget. Earth–Moon space. http://en.wikipedia.org/wiki/Delta-v_budget#Earth.E2.80.93Moon_space If you add up the delta-V's from LEO to LLO, 4,040 m/s, then to the lunar surface, 1,870 m/s, then back to LEO, 2,740 m/s, you get 8,650 m/s, with aerobraking on the return. I wanted to reduce the 4,040 m/s + 1,870 m/s = 5,910 m/s for the trip to the Moon. The idea was to do a trans lunar injection at 3,150 m/s…

Hi guys, new here but i promise I'm not trolling. Something weird just happened to me and I'm only looking for answers. About 30 minutes ago, I was heading out to my garden to mow the lawns. We have a slide door which is secured by a cylinder lock, where the screw enters from bottom up. When I unlocked it, the screw fell out so I had to pick it up. (we if carpet floor if that's any help.) Anyway, I saw it drop and land so I bent down to pick it up. As I was going down, I was looking at the weather outside. However, when I had my eyes back on the ground, I could no find the screw at all. Instinctively, I checked the T.V table beside it, as most things that have been droppe…

Dear all, I am a design student, studying in South Africa and need help on a current project. I am designing a barbecue that doubles as a small fireplace. the idea is that once the fire is out the fireplace can be taken indoors to warm the house. So far my design can be simply put as 2 metal cylinders one inside the other - now I want to fill the gap with a material that has a high heat retention. the idea being that when the fire is burning (cooking food) the heat will be absorbed by this material, then once the fire is out the material will start to radiate the heat. I have had a few suggestions from my lecturers including, sand, brick, stone, salt (NaCl) a…

Was pondering gravity as it relates to orbit... Since, most orbits are circular in nature (or better, elliptical), wouldn't it follow that somehow the ratio pi is inherent in the force of gravity. I've seen pi present in the equations for general relativity and the cosmological constant, and was hoping to get some insight on the significance of the number as it relates to the structure of the universe. The cosmological constant: Einstein's field equation of general relativity: A circular rotational motion and spherical structure seems to be a pattern from the atom to the star to the galaxy... Can anyone here tie this all a little tighter for me?

I was reading about how rainbows are formed in Richard Dawkins' book "The Magic of Reality," and basically it was described as such: light passes through the upper part of the outside of the drop of water (that is in the air) and then reflects off the interior of the back of the drop and then exits the lower part of the drop. My question is, why does the light seem to react differently to different parts of the water drop? In other words, why does the light pass through (rather than reflect off of) the upper part of the outside of the drop? Why does the light reflect off the inside of the back of the drop (rather than pass through the drop, in the same way that it ent…

Ok, so I know why your arms move you forward in swimming. You are pulling the water back which pushes you forward a lot because there is a lot of resistance, and then you are moving your arm forward in the air which offers little resistance to push you back. So the amount you push back in the water is greater than the amount the air pushes you back when you move your arm forward. But what about the legs? There are two things I am confused about: 1)How does moving your legs vertically propel you forward at all? I don't know how a downward kick can move you forward. If I were to kick the ground right now, it would not move me forward. 2) If kicking your legs do…

These are some of the research reached by some researchers in the strongest universities in Egypt, three threads very magnificence in the science of thermodynamics, which is well organized PDF compressed in a single link obtained from Professor Universities of Ain ​​Shams University Abstract The science of thermodynamics is concerned with understanding the properties of inanimate matter in so far as they are determined by changes in temperature. The Second Law asserts that in irreversible processes there is a uni-directional increase in thermodynamic entropy, a measure of the degree of uncertainty in the thermal energy state of a randomly chosen partic…

Hey, i'm no expert in science so I don't know what category light comes under. But here is a question I asked on Yahoo Answers but i'm not getting a reply, plus there answers aren't always trustworthy. I need a LED torch that will show drugs + blood. Currently I have one which shows the security markings on UK driving licenses which according to Wiki is: 230-365 nm: UV-ID, label tracking, barcodes For some reason this does not show the markings on UK notes, like it should do, i'm guessing money needs a different wavelength? Now according to the same wiki page to see blood + drugs you need the following wavelength: 200-400 nm: Forensic analysis, dr…

Ok this is probably a rudimentary question so here goes... At work I have a machine that uses dime sized metal disks to plug holes that reduce/increase the amount of suction ... more holes open = more suction less holes open = less suction. the only way to remove these disks is to use a magnet ... but then I have to remove them from the magnet and store them until I need to use them again. Its a total pain to try and pick the disks off by hand. Is there a way to to rig a switch that I can press or flip that will allow the disks to fall of by themselves but then be able to flip the switch as to be able to pick them up again. demagnetize / magnetize ?? if there …

When a dicussion about Time begins, it usually derails into philosophical blah blah after a post or 2. I'd like to refrain from the philosophical tentation, and try to concentrate on what we really know about Time from a scientific point of vue only. For example: 1. we know that motion requires time: nothing can move from one spatial coordinate to another in zero time, it would be a transgression of the Speed Of Light. 2. we know that the rate of time is related to gravity: where gravity is stronger Time flows slower. 3. we know that time has a "direction", commonly called the arrow the time. 4. we know that time is related to causality, and causality…

This is my first post on this and i am not a qualified scientist but i came up with this theory about how time works which pretty much says that time doesn't exist. so here it goes... thins of it like a simple calculator, for the calculator there is no time, theories or explanations, there are just equations the calculator works out. Now, this calculator works these equations out at a certain speed can be seen as a part of time but if 'time' is seen as things happening in certain speeds and our feeling of time passing by is an illusion that is made by our body doing different things all the time such as breathing, cells reproducing, heart beating and so on. What i am…

Hi there. There is a question which I cant really decide what the answer is. "Does the perfect vacuum have volume ? My answer is: maybe yes. Vacuum is a part of empty space but it is not anything, although vacuum is actually empty space. If we say that vacuum is nothing then it equals to say that 0 is not a number. In this universe where we live there is no such thing as "anything/nothing". Even if the empty space is something, because its empy space if we interpret with the help of syntax (which almost doesnt have anything common with the topic) - the predicate is "is", what does it do ? It is. Who is the subject ? The vacuum, the empty space. It is, it exists. …

physics-chemistry quiz Waxy substance ,resonating to natural ultra vailot radiation , Made from ethylene and benzaladhyead together under high Pressure ?

When I set my multimeter to the DCV 200mV setting and then move the probes around through the air, I get fluctuating readings. It is only when one or both of the probes are in motion. I'm sure there is a perfectly simple explanation but, pray tell, what is it?

I like the famous sci-fi novel of H.G.Wells 'The Time Machine'. The movie infact is a depiction of the novel itself. The inventor has built a time machine which i read somewhere worked on light, prism optics, electrical energy which worked out for the principles underlying of fourth dimensional portals time traversing. There is also rumour that H.G.Wells himself knew about the invention of british scientists of 1700 a.d. and back then was tested and destroyed. The inventor time traveller is said to travel in the past as well as the future by the time machine. He traverses to 700 - 800 a.d., also into the modern future and into the future earth as well. He finds in the pas…

Can anything but death exist outside of life? First man found the molecule, then the atom, and then finally the subatomic particle… each time believing we had finally reached the end of the line. Today we have looked even further into the microscope, unearthing what the most modern science now calls elementary particles, many believing once again that further substructure likely will not be discovered. Yet again as we speak, theorists unite and new theories have arisen, that would focus us even further into mankind’s great microscope. What if life is the same? What if biologists, like physicists, cannot yet see the end of the line from where they stand? What if th…

...he didn't double check his theory. Watch this documentary: According to this video, maybe his book is different, this theory is wrong. The POINT of this video is to show that it began from nothing and they talk about that there is no time for a god to create something...but WHEN? Only when it's a BLACKHOLE!!! So this video suggests that it all began with a blackhole then....but where does the blackhole come from then? There are other flaws, but anyway, you don't need a PhD to realize these errors...

owadays, people have found some more incredible rules and things like founding the Boson! but have we found the last one rule of the hole universe (if it have)? I really want to know it because i belive that everything have its own reason even the space and time. I have some research for this from specific project, as philosophy said that the existing of everything depend on the conflict like space and time but i still can't find out the final rule for all things. I very hope to get the answer on forum and thank you for reading

No, SSTO is not a four-letter word though it is sometimes treated that way by those in the industry. I've been arguing that SSTO's are actually easy because how to achieve them is perfectly obvious: use the most weight optimized stages and most Isp efficient engines at the same time, i.e., optimize both components of the rocket equation. But I've recently found it's even easier than that! It turns out you don't even need the engines to be of particularly high efficiency. SpaceX is moving rapidly towards testing its Grasshopper scaled-down version of a reusable VTVL Falcon 9 first stage: Reusable rocket prototype almost ready for first liftoff. B…

Hi All, I’ve often heard that an electromagnet pulse can be used to knock out power supplies and wondered if I could ask a few questions to the people on the forum who know about that subject? Is it possible? Can you direct the pulse and limit its effect and distance of influence? What types of power supplies would it affect? I’m sorry for any terribly bad mistakes in my thinking or questions and for having to use such layman terms. Thanks

Im recently studying Boltzmann Constant for Landauer's principle. I wondered is there a volume for that? What's the units they use(cm or m) when we derive the Boltzmann constant? I've been looking through the internet but I found nothing. Any Help? Thanks

I read that the Higgs boson is its own anti-particle. What does that mean? Also, are there any other particles that are their own anti-particles?

hi everybody. 1) i read that the diameter of the observable universe is about 93 billion light years. But the age of it is 14.3 billion light years. how could the universe expand itself at a speed larger than the speed of light? is it possible that the universe started not by one singe big bang, but by several sepparated big bangs that banged together in a chain reaction, distanced from eachother, like wwII sea mines? 2) at quantic level, our laws i know dont apply, but is there a field of physics dealing with the laws that apply at the macromacrocosmos? i would imagine that if at a very small level laws change, so should they at a very large scale... tha…

I'm just a little kid with no scientific background whatsoever, so don't be too harsh (A). For me, the spacial dimensions are up-down and left-right. I wouldn't call the third one depth dimension though, but a so called spacetime dimension (forward dimension or even a gravity dimension would be good too which is explained later). We all live in the spacetime dimension while we exist in space and time (duh!). Existing in space means having some kind of a forward motion. You can't have a backwards motion. 'Moving backwards' is still a forward motion in space. Existing in time means that you just are. In the present of your reality. I think we all understand what existin…

I have one layman question Is gravity the geometry of space itself? If it's right then I don't understand how gravity can be the fundamental force and geometry of space itself simultaneously A force that spreads out with particles, creates waves, and geometry of the universe which curves space. thank you