Physics

Can anyone tell me the velocity of a neutrino please? I couldn't find it anywhere...

Is it true that if it's raining and you're moving towards shelter from the rain that it is better to walk to the shelter than to run if you want to become less wet from the rain?

I'd like some help in understanding how Rabi's resonance method works. The figure bellow is the apparatus used. Molecules (or other particles) originate from source and travel through magnetic field of magnet A, then through collimator, and then are deflected by B magnet to detector. In the region of C magnet, a static field Ho exists and an additional rotating field H1, which precesses around H0. From what I understand, in a static magnetic field, nuclear magnetic moment vector will precess around the field vector with Larmor frequency. The angle between the magnetic moment and field vector remains constant, right? But what happens when the rotating field H1 i…

Hello. This is my first post. I am nobody with an average intelligence. I have a very basic understating of time. I want to know if this makes sense. I think time is the movement of things. I am not an expert in physics so by 'things' I mean any fundamental particles. On neutron stars, the gravity is very high. This strong gravity pulls things down, so things move slowly than, say, on the Earth. Thus, time on neutron stars becomes slow. Time on an Earth-orbiting space station goes a little bit faster, because the gravity is a little bit lower than on the surface of the Earth. Time before the Big Bang did not exist, because there were no things before the Big Bang. Whe…

What is the resistance of a capacitor? From the data of experiement, I was convinced that the resistance tends to zero. Is this the truth? There's a part of empty space between two parallel plates. Isn't the resistance very large as it seems it's hard for electrons to pass through these spaces. How do you reconcile the two facts?

I am not questionning invariance of C. There are too many concepts here where none is synonym of the other. Frame dependent, relative, constant, absolute etc. IMHO something can be alltogether invariant and relative. As an analogy: When you stand upright at sea level, you horizon is at approximatively 11km away. The distance to horizon is relative, because it comes from you, you are at the centre of vision. The distance is also constant, if you walk to your horizon, the distance will not diminish. I know it is simply an analogy, distance is not velocity, but it is an example where something relative is also constant.

The Rosetta Mission is in a really exciting stage as it's due to land on the comet. With theories already being rewritten due to the strange rocky pictures of the comet. The exploration will offer more data which should challenge the conventional theories out there already. What are your hopes for the mission?

ajb, separate to EllyDlights thoughts, I would be interested to know, did you have a particular example in mind with your above comment?

I accidentally noticed this several days ago, as I was playing with a transparent plastic bottle in the bath tub. I'm not fully sure why it happens, so I thought it would be interesting enough to ask: Consider you have a thin transparent plastic bottle, like a coca-cola recipient. If it's empty and you are looking through it in the air, it does not noticeably refract any light. But if you fill it with water and look through it again, you see everything deformed through the bottle. This is probably not surprising, since water is much more dense than air... but the reverse also applies: If you submerge the bottle underwater while it's filled with air, it will distort wh…

Hi. When a turning wheel comes to rest, there is an apparent tiny backing of the motion. Is it apparent or real ? As in a turntable, a ceiling fan, or any horizontal turning mass when comes to a stop, gives the impression of reversing.

And how does it work Here is what I am referring to http://en.wikipedia.org/wiki/Electromagnetic_pulse it doesn't talk about devices which utilize electromagnetic pulse but I think I saw in a movie where it was used to disable alot of electronic devices. does that have any truth to it in reality?

Under extremely high temperatures (over ~3.000K) the electrons and protons dissociate, resulting in plasma. But for hydrogen nuclear fusion to happen we need much higher temperatures than this (order of 107 K). How does this process get "inverted"? I mean... If in temperatures higher than 3.000K the protons and electrons dissociate, how is possible that in much higher temperatures they "re-associate"? How are atoms formed during nuclear fusion? Besides, in the beginning of universe expansion, we had the required temperature to fusion.. Why it didn't happen then?

Does solar power work better or worse on the moon?

Hi, all I would like to have understanding for the above notation please. The Lagrangian density is expressed for acoustic waves in four d notation. Further how to differentiate this Lagrangian for Lagrangian equation. I am very confused with indices mix up.

If a jet is flying 600 miles per hour in the same direction the earth is rotating, and the earth is rotating 1,000 miles per hour, how does that jet get to its destination when it is flying 400 miles per hour slower than the earth is rotating? How do I answer this? What do I tell them?

Hello all I'm new here . After browsing some quite intriguing posts my question seems appropriate here. A purely hypothetical question ,although one that may lead to others In short is it possible to reduce particle density within a a certain area of the earth's atmosphere. The purpose of which is to reduce atmospheric weight toward a rocket/projectile directly opposing it.Namely for the purpose of drastically reducing fuel costs. Although you can clearly see other applications. Forgive me if I am assuming or misunderstanding things ; My area of specialisation is electronic engineering. The most obvious way to tackle this I believe is to ionise said area then u…

Here's one that has been bugging me for a while now: In my tiny country (that nice little swamp at the end of the river Rhine) the winter months are crap. Usually above zero degrees (Celcius) and wet. The air humidity is generally at 90% or so. Why does wet air feel so cold? In fact, it feels less cold when it is -1 degrees, because the air is generally a lot dryer... is it me or is that tiny fraction of water really responsible for a major difference in heat transfer? At 5 degrees the vapor pressure of water is about 10 mbar, so the volume (or molar) fraction of water in air is <1%. How can it have an effect that I can really feel? The Cp value o…

Hi. Is there a formula that can calculate the resultant temperature of water when two different amounts with different temperatures are mixed? e.g. 100ml @ 20°C added to 50ml @ 60°C = 150ml @ ??? °C Joe

If i put my toothbrush under a UV light to kill bacteria is it safe to put into my mouth?

Hello, me and a friend are participating with our school's science club as a team and will be taking on an event that focuses on the topic of time. It will involve an exam covering topics pertaining to time and the presentation of an accurate homemade timekeeping device. Here is the event description and here is a sample exam. Note that there are certain restrictions/regulations on the device which are outlined in the event description. Namely, The timekeeping device may not use electricity or chemical reactions. The device cannot exceed 80cm. Any posts sharing pertinent knowledge/understanding would be much appreciated, that is, for the exam, and the homemade tim…

Hey, just had a question for the physics community. Are natural nuclear reactors possible? would it be possible for a natural uranium-235 deposit to be introduced to a neutron emission somehow, and it to begin a fission reaction?

(Mods, if I haven't posted this in the right place, please move it!) I'm terrible at physics, so I'm hoping to get some help from this forum. I have a fibreglass cast on my right arm, courtesy of a stupid skateboarding accident. I have devised a method for aerating the cast, which can become a bit stinky. My method involves a vacuum cleaner and an improvised nozzle, consisting of foam rubber pipe insulation with a gauge of 1/2". It works well - the seal is relatively airtight against the cast itself, and I can feel it sucking air through the fibreglass. However, I'd like to improve it further. Assuming the above gauge (1/2"), a variable length (currently 5…

Hello everyone Consider a convex surface, a light ray being emitted from point O, being refracted by the surface in point P. The light ray forms an angle alpha with the line OC, C being the centrum of the convex object. PC forms an angle beta with OC and is the normal in P, the point in which the light ray is being refracted, Q is the intersection of OC and the convex surface, OP forms an angle theta 1 with the normal, the refracted light ray forms an angle theta 2 with the normal, intersecting OC in I, the point in which the image will be projected. Gamma is the angle formed by PI and OC. My syllabus states: If alpha is small enough, beta, gamma, theta 1 and…

I have known a number of physicists who have had an interest in playing musical instruments and, of course, it is well known that Albert Einstein played the violin. In the UK, there are several universities which offer degrees in Physics and Music. For example: The university of Cardiff: http://courses.cardiff.ac.uk/undergraduate/detail/fw33.html The university of Edinburgh: http://www.ph.ed.ac.uk/studying/undergraduate/our-degrees/physics-and-music The Royal College of Music with Imperial College: http://www.rcm.ac.uk/courses/undergraduate/bschonsinphysicsandmusicperformance/ What is the connection between the two subjects? I don't think it is simp…

My apologies for so many questions, The Earth spins, and I have heard the spin is slowing down. Is this true?