[Tycho?]

So while we are talking about light, could someone please clearify black body radiation for me. Am I wrong to assume it is electromagnetic radiation? As I see it if you heat up iron hot enough you see it glow red because the EM is now a little more intense and has a higher freequency therefore we see it glow red as opposed to it just being invisible I.R.

If this is true when is something too cold to be a black body radiation emitter?

And if nothing is too cold then is everything a source of light? Would this conclusion also mean that colour would have to exist because nothing could be in absolute darkness void of any kind of light if everything emits it?

 

Thanks for clarifying the E field B field question. I do see how I was getting mixed up there.

Black body radiation is EM radiation. Even very very cold things emit it, you'd have to be at absolute zero to not emit it (which isn't going to happen). Yes, all matter is a source of EM radiation.

Not sure what you mean with colour though. Colour would have to exist? Well it exists now. But yeah, you'd always have some radiation incident on you. Even if you made a box that was totally empty of air and totally dark, the walls of the box would still be emitting radiation (probably IR) inside the box. This is one reason why getting close to absolute zero is so darned tricky, because everything is emitting radiation to one extent or another.

Also, much more precise corrections are made by scientists, financial institutions, and other orginizations that need to keep very precise time. In 2005 (and many times before that) a leap second was added to the clocks, in order to make sure everything agrees.

But velocity does result in redshift.

Also you had better provide a link, there isn't a lot to comment on here without more information.

I've never understood why this question was important at all. It seems like we have free will. My will is to eat the yogurt covered raisins sitting next to me; I then do so. If I were destined to do this, I am certainly not aware of it, nor is anybody else. This would only matter if time travel to the past were possible, in which case you could actually test to see if it was deterministic or not.

Uh, no, it doesn't rule out atoms. Atoms themselves are made up of several different particles, they are not considered to be point particles.

He said near the speed of light.

"Physicist" is not the sort of job you will find online. You'll probably find work through your graduate school, and it will very likely be working for a university somewhere. There is not a lot of private or government interest in astronomy, doesn't really make much money. There is some of course, most would be academic research though.

So, lets move this to Speculations, or somewhere else thats not here.

Yes, the outside moves more quickly. I dont see what is wrong with this.

Ok I get that imaginary numbers are important but I'm still not sure how they are used. Like when my math teacher explained it she said that you cant take the square root of a negative number so i was made up to represent this. I just fail to see how this makes the equation any more solvable. You still can't have the square root of a negative and just because you put an i down doesn't change this.

Look it up on wikipedia. Imaginary numbers are immensly useful in physics. They can hugely simplify almost anything to do with waves (which is a huge chunk of physics right there), they are pretty much required for circuit stuff in electrical engineering. I dont have any personal examples beyond this, but I'm sure there are a ton. Hugely useful.

well I was considering testing this but it seems my electroscope got lost in the move (either that or it`s still in a box somewhere) so I`ll have to make one it would seem.

 

I wonder if this can be stored in a Capacitor of some sort though, if it was a low electron count per second, a cap should accumulate this charge over time quite nicely I sumise?

Would it though? I thought (not like I'm sure at all) that both plates of the cap had to be part of the circuit when being charged. Little more than a guess on my part though.

I think you would probably need a large amount of radioactive stuff to produce the effects anything like a Van de graff generator, that is getting a charge in a reasonable amount of time. This is just a guess of course, I'm sure you'd be able to calculate the actual number of electrons you'd be getting.

Also you have to make sure that you'll be quite safe with regards to radiation. A metal shell will stop beta rays just fine, same with alpha. But if you get something that eventually decays to something producing gamma rays you'll be in trouble.

Just from checking wikipedia, I see that radium decays into radon, which is a radioactive gas and is quite toxic.

So while yes this would probably work, but it may not be worth the health hazards.

It's the Mandlebrot, Julia, Nova, Barnsley, Newton etc... type fractals, they are verry much related to numbers which have real and imaginary parts. This is verry evident even when just using fractal art software like Ultrafractal not just when delving into the maths.

Ok, I still fail to see how thats the most important use of imaginary numbers. It looks more like the least important use.

What do imaginary numbers have to do with fractals?

As for the example of things crashing into eachother, no, nothing travels faster than light, including compression waves. If a planet crashed into a moon or something, people on the opposite side would feel the smash later than those right under it.

Here is the classic example: You have a long, rigid metal bar. This bar is a light year long, lets say. You nudge one end of the bar. Does the other end of the bar thats a light year away move instantaneously? No, it does not. The minimum time it would take is equal to the speed of light. In this example it means that the other end of the bar would not move for at least a year, since this is how long it would take for light to travel the distance. And its impossible to have anything that is totally uncompressable.

All of the relevations about the nature of time that I see online always bug me. Its all just a bunch of hand waving, half explained examples, bad analogies and false conclusions. And at the end its always concluded that time does not exist. And then you look at a clock. And you realize that wait, time does exist, and this thing I just read explained nothing at all.

It would have to be very, very dense. And as has been mentioned, it would be perposterously heavy, far far far too heavy to be useful.

Well thanks for the advice everyone, I've gone for the TI-89 since they are so popular both here and another forum where I posted the same question.

Could you use the centrifugal force generated by a spinning section of a ship to create a gravityesque force? Then have people spend as much time in that area as possible?

Yes, this has been a staple of sci-fi for decades. Such a thing would be expensive and difficult, but its guarunteed that it will be done sooner or later.

I almost thought so. I mostly mentioned it because you were saying "that lasts me for years" and I thought a graphics calculator won´t help you much for giving a talk on a conference or stuff like that. I don´t know how important that "lasts for years" is for you and I also don´t want to be the one responsible for your choice (all advice is given without any warranty!) but one thing you shoul possibly keep in mind is the following: Of those who give recomendations for a graphical calculator here, how far beyond 2nd year of physics do you think they are?

 

EDIT:For the sake of fairness I should explicitely say that I´ve never used a graphical calc, so I don´t know what I might be missing - I certainly never missed anything.

Haha, I dont plan on giving talks anytime soon. I'll always own a computer anyway, desktop or laptop depending on the situation.

But even now, I still use my basic calculator when I'm sitting infront of my computer doing homework. There is something nice about holding it in my hands. Plus most of the equations I deal with are faster to punch into a calculator than a keyboard.

I'm not keen on a laptop. For one I already have a desktop computer, and while I like to use it for math stuff, its actually suprisingly difficult to find useful software. While a graphing calculator comes with all the software I'd need, and I can take it to my labs. So yes, all opinions apprecated, but laptop isn't going to happen.

I'm in second year physics, and I feel the time has come to get a graphing calculator, so I'm going to ask for one for christmas. I have prior experience with the classic TI-83 plus, so by default I would lean towards this one because I know the interface.

But, there are also TI-84s, 85s, 86s and 89s that are all of the same basic design, but more advanced (and more expensive). There is also the 83 silver edition. So do any of you have experiences with these calculators? What would you recomend for a second year physics student, who wants a calculator that will last me years? Whats the best bang for the buck?

Any opinions appreciated.

Look up dark matter and dark energy and e=mc^2.

http://www.wikipedia.com

But surely an object would have more mass in a 4d Universe for any given volume, as it has an extra direction to extend in...?

I dont think you are visualizing this properly. Or maybe its beacuse you are trying to visualize it.

Why in the world would you think that?