Ask a physicist
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Sorry I completely misread.Redingold said:
Electrons belong to a group of particles called fermions due to the fact they have spin 1/2. All fermions obay pauly exclusion, this is that no 2 electrons in a system can exist in the same quantum state. It is the reason that their are shells instead of all electrons getting as close to the +ve nucleus as possible. Their are 4 quantum numbers when it comes to electrons in an orbit; n(shell number), l(subshell), m(orbit), s(spin). So for n=1 (the innermost shell) you can only have 2 electrons: n=1, l=0, m=0, s=1/2 and n=1, l=0, m=0, s=-1/2. Resistance is caused by electrons scattering off the lattice in a material and causing a rise of temperature in the material.
Now in the case of superconductivity the electrons pair up into cooper's pairs which have spin 0 and so pauly exclusion no longer applies. Due to quantum mechanical effects the cooper pairs require a minimum amount of energy to excite them, if this energy is greater than the thermal energy (kT where k is boltzman's constant and T is temperature) the electron pairs will not be scattered by the lattice, thus having 0 resistance.
This means a current travveling in a superconducting coil does not dissipate. Another, commonly demonstrated property is the levitation of magnets, this is due to in lorentz's law a magnet producing a current in a coil will be repelled by the magnetic field the current in the coil produces. In the case of a superconductor the magnetic repulsion equals the force the magnet produces on the superconductor, so if you approach a superconducting surface with a north pole the surface acts like a north pole and same with the south pole so it always keeps the magnet repelled away from it.
Yes because the co-ordinate for time is ct which is a distance, so by definition of the above without having to add relitivistic corrections in things move through time at c.Chamale said:
Again yes, it's 4 rector will be the same magnitude but it will have been shifted away from the ct axis to provide velocity in space not time.
A common mistake, Kinetic energy can nolonger be stated as simply e=.5mv[sup]2[/sup], this only works in classical mechanics. Also E=mc[sup]2[/sup] doesn't tell you the whole thing, this would say photons have zero energy since m=0 but we know this isn't the case. The real expression is E[sup]2[/sup]=sqrt{(mc[sup]2[/sup])[sup]2[/sup]+(pc)[sup]2[/sup]} this reduces to the famous E=mc[sup]2[/sup] when the particle has no momentum.
To observers on Earth the ship takes 101 years to get to the star but the crew's clock only advances 14.24 years. When the ship returns (assuming same speed and no turn around deceleration) On Earth 202 years have passes on the crew's clock 28.48 years have passed.
However their is a problem in this, hence its name the "twin paradox";
To the crew the ship takes 101 years to get there and they'd see Earth's clock advance only 14.24 years and same with the return leg. This is a problem with special relativity that is later solved by general relitivity.
They would have to adjust the information stream as if the people on earth sent 1bit/sup the pulse, the crew would get it at .14bit/s, this is due to not only time dilation but the fact that when a bit arrives the ship has moved away a non-trivial amount before the next one arrives stretching out the bit duration and rate. The last possible send time would be after 1 year (Earth time) since the data would take 100 years to get to the star but it only takes the crew 101 to get there by Earth's clocks.
Nah, I was actually calling theists quite silly for just pulling this out at every blank. And yeah we don't know, yet.creationis apostate said:
Not heard one yet.henritje said:
Their are 2 equally good ways I can answer this depending which heory you use to approach it so here goes;TiredGiant said:
1) Quantum mechanics - Every electron possesses a property called spin, now this in effect makes the electron into a tiny magnet due to the motion of a charge. In a magnetic material their exists many small regions called magnetic domains, in the case where electrons have randomly oriented spins the domains are one electron in size, as you increase the ordering by magnetising the material the spins begin to allign. When this happens the domains begin to merge making larger and larger magnetic regions until eventually the entire material is one domain. At this point the material is as magnetised as possible, the saturation magnetisation. The domain size changes to keep the magnetostatic energy within the material at a minimum.
2)Relativity - If you picture a coil of wire wound around a iron rod with a current flowing trough it this is an electromagnet. If you send an electron along the length of the rod at almost c outside the coil it will experience a deflecting force equal to F=q(E+(vxB)) where q is the charge on the electron, E is the electric field, v is the velocity of the electron and B is the magnetic field.
If you use the rest frame of the coil and look at the force on the electron it would be F=q(0+(vxB)) since outside a stationary coil their is no electric field, so F=q(vxB), the force is entirely due to the magnetic field.
If you use the electron's rest frame the force is now; F=q(E+(0xB)) since the velocity of the electron is 0 in it's own rest frame by definition, however due to length contraction the coil now appears as a point charge, which does have an exterior electronic field. So the force on the elctron is now F=qE therefore the force is entirely due to the electric field.
It can be shown by using real numbers and slogging through the maths that the forces are exactly equal in dircetion and magnitude, meaning that both electronic and magnetic fields are the same thing, just viewed from differing frames.
Well, for a start luckyly religion does not have the power it once did, I don't forsee going jail or having my work banned if I come up with a formation theory for spiral galaxies like the astronomers of old and the whole Earth goes around the sun thing.Trezu said:
And to be honest I haven't once thought how any of my research would agree or conflict with religion but I'm betting their would be those extreemists who declare me a heratic for it. I just think of the God answer as a cop out, no need to ever try and discover anything if you just say oh it's because God says so or whatever. Why should spiral galaxies have these amazing spirals that come from the centre and in which all the stars exist with big gaps of nothing inbetween? Well my answer for this certainly wont be God did it I can tell you that.
What is being a postgrad like?
I'm applying to do a research Masters and my professor is questioning my understanding of the effort involved and whether or not I have the motivation to go through with it.
So if you could break down what being a science postgrad is like I'd appreciate it.
I'm applying to do a research Masters and my professor is questioning my understanding of the effort involved and whether or not I have the motivation to go through with it.
So if you could break down what being a science postgrad is like I'd appreciate it.
Well, basically, no. What happens is, as you travel closer to the speed of light, relative (the universe's) time continues on, but your time is different. A sixteen hour trip for you at the speed of light appears to take two seconds to those of us still on Earth. (That is an example from the movie Contact, and vetted by my Astronomy teacher.) The closer to the speed of light you travel, the slower the universe appears to move around you.DasDestroyer said:
Also, Time travel is impossible according to the laws of physics, as we know them.
And here I was, unsure if my decision to go for an Astro-physics or some other type of Astronomy based Doctorate was a good idea. I can't wait to have that title... Thanks for the spark that will keep my drive going.cookyy2k said:
I've been building some planets lately (stupidly I started in my basement, I have no idea how I'm going to get them out when I'm done) and I've been wondering about gravity and water displacement.
If you had a terrestrial planet with higher gravity would boats have an easier time floating (because the water would be denser at sea level) or would floating be more difficult (as gravity would be pulling them down with more force).
If you had a terrestrial planet with higher gravity would boats have an easier time floating (because the water would be denser at sea level) or would floating be more difficult (as gravity would be pulling them down with more force).
It's ridiculous right now. Antimatter is not an energy "source", as it is not naturally occurring in any usable quantities. Rather, it is a (potentially) powerful energy store; since it's annihilation with matter is 100% efficient, a matter-antimatter explosion has by definition the highest possible energy yield of any material by mass. As of right now, antimatter takes much, MUCH more energy to create than it releases when annihilated, and cannot be stored in any significant quantities, nor in any insignificant quantities for any significant length of time. By the second law of thermodynamics, it will always take more energy to create antimatter than that amount of antimatter will release via annihilation.Nimcha said:Would you please tell people that an 'anti-matter bomb' is completely ridiculous? People don't seem to believe me when I say it.
Also, have you been to CERN?
But if, through major technological advances, a fairly efficient means of creating antimatter and an effective (and portable) means of storing it are developed, an antimatter bomb would be an ideal weapon, with well over 100x the energy yield of a similarly massed thermonuclear bomb (and, incidentally, none of the fallout).
By the way, if this is about Angels & Demons, don't worry. Seriously. Dan Brown doesn't know a single goddamn thing about anything, except apparently how to write multiple best-selling novels.
Not sure if this is a stupid question to ask but what are "dimensions" exactly? And what I mean is like when people says "3D" or talk about a fourth dimension.
CAPTCHA: Purpose forsin, well captcha if you say so, I mean God would have died for nothing if we had not sinned.
CAPTCHA: Purpose forsin, well captcha if you say so, I mean God would have died for nothing if we had not sinned.
Well what you've gleamed from the article and said above is right so I'd guess it's a decent one.j-e-f-f-e-r-s said:
The act of entangling two particles is fairly complex. For example electrons are spin 1/2 particles (spin is a quantum property) if you could decay a spin 0 particle into 2 electrons they'd be entangled, since they came from a spin 0 particle they'd always have to sum to spin 0. So one would be spin 1/2 the other spin -1/2. Now if you flipped the first to spin -1/2 the other would have to instantly flip its spin to 1/2. The interesting part is this can violate relativity. the two electrons could be seperated by miles but the information from one to the other to "flip" its spin is instantaneous, thus the information has travelled faster than the speed of light.
Quantum entanglement may well be responcible for the universe properties, we don't really know. Something had to cause density fluctuations in order for structure like galaxies and stars to form so maybe. What is known if you can't say what one electron in an electron gas (a cloud of electrons and nothing else is called an electron gas) is doing without taking into account the state of all the other electrons in that gas. So this may be true of every particle in the universe, and a reason why quantum mechanics is only a good approximation not a true solution.
Well I hope that helped, it's certainly an interesting field and I've done quite a bit of quantum mechanics thought this is not exhaustive and I'm no expert.
In this case it would be equivalent. The weight of the boat is more so it would need to displace a volume of water equal to that incresed weight to float, the water would be denser by the same amount so it would need to displace as much as it does on Earth.Hungry Donner said:
It's hard, expect 60-70 hour weeks not your standard 40 like in a job. Expect frustrating problems and dead ends that last weeks. On the plus side it's an increadible feeling when you get something you've been working on for weeks or coming up with something and knowing you're the only person living or dead to know this, it's a strange feeling. So in summary, very hard work and you have to push yourself every inch of the way but it's amazingly rewarding.NeuroticDogDad said:
It's not completly ridiculous atall, not overly possible under today's technology since we can't make much (8g so far have been made) but it's certainly a possibility that hopefully they'll never be able to make...Nimcha said:Would you please tell people that an 'anti-matter bomb' is completely ridiculous? People don't seem to believe me when I say it.
Also, have you been to CERN?
I haven't managed to go CERN no, but it's on my list of things to do.
dimensions are degrees of freedom, for example a particle can move in x, y, z or t aswell as some others. It's had to pictue having extras but it's neccessary to make the maths work. It's awkward writing 4D matacies but luckily computers can sort that for me.Aglaid said:
I would question the non of the fallout thing since yes while their is no radioactive waste left over annihalation turns the mass of the objects completly into gamma radiation at an extreem rate (E=mc[sup]2[/sup] and all). So the shear amount of radiation will be beyond current comprehension and that is bound to cause havoc with elecments in rocks and trees etc and make them radioactive leading to indirect fallout answell as a highly irradiated area.llafnwod said:
Not really. I was talking about a bomb within an order of magnitude or two of the power of a current fusion warhead. The sorts of processes you're describing take place in high-energy laboratories, extremely high mass stars, and supernovae. Yes, there will be a huge burst of gamma radiation at the moment of the explosion, but that's not really fallout and a bomb of that magnitude is not going to cause much past temporary ionization.cookyy2k said:
So what do you think of the possibility of a multiverse, with our universe being the result of a collision between multiple universes? (note that astrophysics, and physics in general is just a hobby of mine, and I don't really pay a hole lot of attention to it.)cookyy2k said:
It does seem to be one of those cases of stretching the theory a little too much. A human brain works on electrical impulses, this is not something that can be entangeld. I our brains used spintronic impulses (using the spin of the elctron not the charge to transfere information) then I could see the logic to it. I could see how electrons and other particles could be entangled between different brains however I can't see how that would mean one person could effect the other. Our bodies don't care what spin an electron has, if it did an MRI would probably be fatal.j-e-f-f-e-r-s said:
Light is both at once, it's a hard concept but in quantum mechanics it's a property called wave-particle duality. electrons and protons are also both at the same time.
The observation changing the result thing is one of the problems with Quantum mechanics. For example any particle (lets use the electron again) can be thought of as a wave, this wave is called the wave function, the probability of finding the electron in a certain point in space is equal to the wavefunction at that point squared. From the wave function properties such as momentum can be calculated. However this method requires the wave function to be smootly varying in time, that is it never "jumps" around from time to time. So if you measure the exact possition of the electron the wave function will jump to it having zero probability everywhere other than where it is, and 1 at it's possition. The wave function has just "jumped" they call this the wavefunction collapse. Now you know the position however in doing so you've collapsed the wavefunction and so the momentum you measured earlier using that wavefunction is now wrong, you cannot know it. If you let the electron go again and use it's wavefunction to find its momentum you've now lost it's possition information because it's a wave function probability again.