[QUOTE=zzzz;39594306]i'm not sure, it sounded like you were trying to refute my point or something, but i guess you weren't since you said that the universe older than 300,000 years after the big bang could not be observed, but this was [b]380,000[/b] years after the big bang[/QUOTE]
You're off by a factor of 1000.
whoops, 380,000,000. sorry i can't math
[QUOTE=Zeke129;39589271]So the distance alone would make it slower and slower but wouldn't time dilation mean it was slower from the very start as well?[/QUOTE]
As mentioned, the relativistic Doppler effect would shift the light frequencies so they for one would not see your movie in the correct colors. Also, this information will travel at c regardless of frame! This is a law derivable from the idea that physics laws are the same in all frames from the Lorentz transformations. What will happen is that you will broadcast the movie and they will not see it until the light reaches them, but after that it is a constant stream of information - there is no reason for it to be played in slow motion!
[editline]15th February 2013[/editline]
[QUOTE=JgcxCub;39589748]How does exactly zero resistance with superconductors work? How does it interface with ohm's law?[/QUOTE]
1) Ohm's law is plain wrong. It is a special case of an integral for the power through a conductor that works for ordinary metals.
2) Superconductivity I don't know much about (I just did a project on the topological insulator, which is sort of related but not really) but basically the zero resistance is the result of some weird quantum effects due to spin on the surface, I believe.
[QUOTE=JgcxCub;39589748]How does exactly zero resistance with superconductors work? How does it interface with ohm's law?[/QUOTE]
It doesn't interface with it; low temperature superconductors have their electrons "pair up" into Cooper pairs which tend towards being in the same ground state, if memory serves. High temperature (YBCO, etc.) ones no-one's quite sure of, yet, as far as I'm aware.
[QUOTE=Cooty;39596216]As mentioned, the relativistic Doppler effect would shift the light frequencies so they for one would not see your movie in the correct colors. Also, this information will travel at c regardless of frame! This is a law derivable from the idea that physics laws are the same in all frames from the Lorentz transformations. What will happen is that you will broadcast the movie and they will not see it until the light reaches them, but after that it is a constant stream of information - there is no reason for it to be played in slow motion![/QUOTE]
Wouldn't the broadcasting equipment operate more slowly due to time dilation? It's moving near light speed as well.
I've had a bit of a retard moment, does anybody know what the name for a program that can translate this emission spectra into an actual output with wavelengths?
[img]http://dl.dropbox.com/u/888382/oliver_mercury.bmp[/img]
I know that was the worst possible way of describing it, but I managed to get a set of excel results using a program that did just this, but I can't remember for the life of me what the name of the program was.
If it's any help, it was to generate a calibration equation graph for a spectrometer using a mercury light source.
[QUOTE=Falubii;39597633]Wouldn't the broadcasting equipment operate more slowly due to time dilation? It's moving near light speed as well.[/QUOTE]
this is what I'm thinking, too.
even though the photons from the screen are going to travel at c, the physical mechanisms that refresh the TV screen are going to be slowed from the earth's frame of reference, so the video should appear to play more slowly
that's my crap half baked guess anyway
^ that
otherwise you could make the argument that time dilation wouldn't happen at all, since there's little distinction between seeing photons being reflected off a person and seeing photons coming from a film. If the film doesn't appear to be in slow motion, there's no reason the person would.
So:
if the trip is 2 hours for me I'll be watching the movie over the entire length of the trip. If that amount of time is 2 months (or something) on Earth they'd be seeing the movie stretched out over that entire length of time
Otherwise Earth would be seeing the movie before I do, right
[QUOTE=Zeke129;39605144]So:
if the trip is 2 hours for me I'll be watching the movie over the entire length of the trip. If that amount of time is 2 months (or something) on Earth they'd be seeing the movie stretched out over that entire length of time
Otherwise Earth would be seeing the movie before I do, right[/QUOTE]
Exactly, it would look like a really stupid slide show.
Can anyone here explain to me how the equation for the displacement of a particle undergoing simple harmonic motion is x=x0cos(wt)
where,
x0=the amplitude of the cos curve
and w = omega
I just don't understand how someone once looked at the path of an oscillating ball on a graph and wrote down the equation x=x0cos(wt)
[QUOTE=Yahnich;39608264]the forces acting upon a spring ared F = -kx giving m*x'' = -kx this is an ordinary differential equation, solve and you eventually get that. (easiest solution is to take x = e^qT with q being a constant and T the variable)
also e^ix = cosx + isinx will help you with this[/QUOTE]
but how does someone know that they have to use the equation x=x0cos(wt) to solve the differential equation? When I first did the differential equation my teacher just said something like "and the equation for the displacement of the ball is x=x0cos(wt)" I want to know why it is that as in, why you multiply by x0 and why it's cos(wt) not cos(t)
Using the standard approach of x = exp(qt), it falls out of the equations thanks to de Moivre's theorem. [url=http://i.imgur.com/W552a4p.png]I've attached how I'd prove it on this link[/url]; if you want to do it yourself, don't look.
[QUOTE=Greenandred;39609064]Using the standard approach of x = exp(qt), it falls out of the equations thanks to de Moivre's theorem. [url=http://i.imgur.com/W552a4p.png]I've attached how I'd prove it on this link[/url]; if you want to do it yourself, don't look.[/QUOTE]
I see now why I couldn't figure it out on my own, I haven't been taught imaginary numbers yet (and quite a lot of other things on there). Thanks for the proof though, it clears up a lot.
Kind of physics related, thought I'd share. Gamma spectra from my 30x70 Nal detector, shielded of course. First one is uranium, I am bad at making graphs.
[url=http://postimage.org/image/as6pjjxc9/full/][img]http://s4.postimage.org/lrrwv5nrh/Data_1.png[/img][/url]
[url=http://postimage.org/image/g1x7o1u27/full/][img]http://s11.postimage.org/dxcumysfn/spectrum1.png[/img][/url]
[url=http://postimage.org/image/d94040tpr/full/][img]http://s11.postimage.org/dymsgdu9f/Data_1.png[/img][/url]
I have some japanese samples I am testing, maybe I'll post if there's anything interesting. On a 1x1 inch detector only uranium is found.
Cool!! Where did you get the detector?
We were also playing around with Cesium-137 in a lab, I think I got graphable data as well.
[QUOTE=Swebonny;39627739]Cool!! Where did you get the detector?
We were also playing around with Cesium-137 in a lab, I think I got graphable data as well.[/QUOTE]
Well, the PMT etc was in an already built unit, I just added a 30x70mm Nal crystal that I got on ebay. $160, and it has similar if not better resolution than expensive 1.5 inch units.
My system uses a gamma spectacular, which is an awesome little device. It's a MCA with amplifier, HV source, etc all in one. It also can run GM probes.
Great place to buy sources is spectrum techniques. I want to get one of those Na-22 sources.. decays by emitting a positron with a decent half-life. Now that's interesting.. I want to try it in a cloud chamber.
Expensive though, my Cs-137 source was ~$100 and is 10 uCi. But you need it for calibration, so no cheating. I suppose you could use Uranium, but you can get nice accuracy with its clear 32 kev x-ray peak.
You know the activity of the lab source? I imagine it's not too strong but they can have stronger sources than exempt quantities.
Ha that's funny. I have to do an oral presentation on Tuesday on experiments in gamma ray spectroscopy my lab partner and I did in over the course of a week. Our sources were Na22, Cs137 (the spectra being identical to the one fox 09 posted), Co60.
[QUOTE=Goodthief;39608475]but how does someone know that they have to use the equation x=x0cos(wt) to solve the differential equation? When I first did the differential equation my teacher just said something like "and the equation for the displacement of the ball is x=x0cos(wt)" I want to know why it is that as in, why you multiply by x0 and why it's cos(wt) not cos(t)[/QUOTE]
You can use the reduction of order method on the equation if you like, allowing you to make it integrable. But usually we solve DEs either by an educated guess (as in this case) or, if we haven't a clue, a polynomial series which we hope gives something nice.
[editline]18th February 2013[/editline]
[QUOTE=Turnips5;39603662]this is what I'm thinking, too.
even though the photons from the screen are going to travel at c, the physical mechanisms that refresh the TV screen are going to be slowed from the earth's frame of reference, so the video should appear to play more slowly
that's my crap half baked guess anyway[/QUOTE]
The answer is I'm not sure about that. Electronics operate roughly at the speed of light, though not quite - current travels through the EM fields rather than by electrons bumping through materials as they teach you in school. Given there's a slight difference between info transfer and c, the time lag in the circuit producing an image should certainly appear larger to Earth, but whether that's really appreciable is another question altogether. However, remember that simultaneity is always violated in relativity if something travels at v<c; it's perfectly possible for somebody to observe something before we do in the moving frame!
Here's an interesting piece of information: consider the length contraction and time dilation effects for something travelling AT the speed of light. How far does it travel in its own frame of reference, and in what time?
[QUOTE=fox '09;39627933]
You know the activity of the lab source? I imagine it's not too strong but they can have stronger sources than exempt quantities.[/QUOTE]
You may have seen me post this image before:
But we had this lead castle for safety reasons.
[IMG]http://i.imgur.com/twLlYEA.jpg?1[/IMG]
Anyone here going to or is studying civil engineering? I'm going onto civil and structural engineering. Can't wait to build sewers. Man the physics behind moving your shit from A to B intrigues me greatly.
[QUOTE=Swebonny;39630366]You may have seen me post this image before:
But we had this lead castle for safety reasons.
[IMG]http://i.imgur.com/twLlYEA.jpg?1[/IMG][/QUOTE]
Jesus? Those blocks aren't all lead, are they? They'd weigh a goddamn ton.
All lead. The block with the red handle is like 5-6 kg.
[editline]18th February 2013[/editline]
It could have been more I remember it beeing awfully heavy.
Just curious, but I was figuring out what would happen if the antipope and pope (from the Medieval era when the schism was going on) happened to meet each other in Late Medieval Rome.
I assumed they both weighed 80kg, and there was 100% efficiency when they were converted into energy. (Which came to around 1.44 x 10^19 joules)
I also think it would create a explosion roughly equivalent to 3.4 gigatons of TNT.
What sort of things would I expect afterwards? (Assuming it's the year 1370).
[url]http://en.wikipedia.org/wiki/1883_eruption_of_Krakatoa[/url] times 15?
Uh, well the utter destruction of Rome and a significant amount of the surrounding countryside. (if it was a nuclear blast, the fireball would be something like 15km in radius)
[QUOTE=Swebonny;39630366]You may have seen me post this image before:
But we had this lead castle for safety reasons.
[IMG]http://i.imgur.com/twLlYEA.jpg?1[/IMG][/QUOTE]
Here we don't call them castles but pigs.
[editline]18th February 2013[/editline]
[QUOTE=JohnnyMo1;39632285]Jesus? Those blocks aren't all lead, are they? They'd weigh a goddamn ton.[/QUOTE]
The safety part in our lab manual says
"Remember the Lead Bricks are a minimum of 30 to 50 pounds each. If it is knocked off the bench and falls onto someones foot it will smash it to pieces."
What will get smashed to pieces...? :v:
Definitely looks like it's referring to the foot, and I am not surprised.
Just imagining that is painful.
[QUOTE=JohnnyMo1;39632861]Uh, well the utter destruction of Rome and a significant amount of the surrounding countryside. (if it was a nuclear blast, the fireball would be something like 15km in radius)[/QUOTE]
Just imagine a 30km diameter fireball.
Nukes are terrifying.
[QUOTE=booster;39637035]Just imagine a 30km diameter fireball.
Nukes are terrifying.[/QUOTE]
You'll find this to be useful
[url]http://nuclearsecrecy.com/nukemap/[/url]
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