Science literature

][cEMAN**

OK I was wondering what types of magazines or journals you all read when you wanted to get some insight into science....

Reason i'm asking - I used to buy on a regualar basis a magazine called 'FOCUS'. Now it was more a pop reference to the science world. It gave more interesting facts and what would be considered APPEALING to Joe public.

Are there any other magazines available to buy at your local newsagent for such a thing or should I stick with this one? Or do any of you know if this is a trash magazine and not worth what's it's printing - ie. not true in facts.

Bob the Unlucky Octopus

Scientific American, Science Magazine, the BMJ, New England Journal of Medicine(amongst other medical journals), Petrochemica(a nice insight into the chemistry of aggregate alloys).

Those are the main ones, it has to be said. Scientific American is probably the closest thing to Joe Public in that list- but a more aware than average Joe that is

Occy

][cEMAN**

You know what I say to that....
OI!!! JOURNAL!!! NYOOOOOOOOOOOOOOOOOOOOOOOOOOO!!!

Nah I h8 reading through long lists of "In 19blahblah blah blah blah blah blah"

Look i'm not interested in a history lesson. I like facts I like to know what the 'a' in a+b=c.

I mean knowing when things were disconvered etc and the social background of the find won't help me in my expansion of knowledge in the hope that having a value for 'a' and 'b' will help me find 'c' and create a world discovery.

Knowing E=mc^2 lead me to understand that light must have mass and to correct my physics teacher who told us it is purely energy!!

We can only move on the knowledge we have. If we all add a little into the pot then a great stew of inspiration can occur.

I want to take a spoonful from that stew.....

bonkey

Originally posted by ][cEMAN**
You know what I say to that....

Knowing E=mc^2 lead me to understand that light must have mass and to correct my physics teacher who told us it is purely energy!!

Err, I dont think so.

E=mc^2 gives you the energy of a particular amount of mass. However, it doesnt imply that all energy *must* be mass. Mass is a form of energy, there are others.

According to current models, nothing with mass can travel at the speed of light. If light itself had mass, then it couldnt travel at the speed it does, or anything with mass could potentially reach the speed of light,

Both of these options contradict current models.

Put in a simpler explanation...a dolphin is a porpoise, but not all porpoises are dolphins. In the same vein, mass is an expression of energy, but it is not the case that all energy is "massive".

jc

][cEMAN**

Then explain why light refracts off the different layers of the out hemisphere and ozone to change colour or slow down and become visable in the colour spectrum.

If E=mc^2 is a constant rule then E is proportionate to mass therefore can not exist without it. If though you say that light can travel at the speed of light only as it has no mass then this formala is incorrect. And if this formula is incorrect in any way then it means that it IS possible for mass to travel at the speed of light dependant on the mass.....

All mass in the universe has energy - it has some potential. Even if perfectly still in space it's gravitational attraction to even the furthest other mass in the universe is energy potential. The fact that it is not alone in the universe means that it HAS to have energy. Though Energy must ALSO have mass otherwise what is this energy? where did it come from? energy can not jsut be created it has to be transformed or passed....can only be done through mass.

Bob the Unlucky Octopus

Originally posted by ][cEMAN**
Then explain why light refracts off the different layers of the out hemisphere and ozone to change colour or slow down and become visable in the colour spectrum.

A couple of corrections- light refraction has to do with light behaving somewhat (but not completely) like a particle, and losing some of its energy as it traverses a bi-layered density. In other words, it has a lot more to do with length distortion properties as one approaches c than it does with any mass that light might have (which it doesn't).

All mass in the universe has energy - it has some potential. Even if perfectly still in space it's gravitational attraction to even the furthest other mass in the universe is energy potential. The fact that it is not alone in the universe means that it HAS to have energy.

It is more correct to say mass is a form of energy. Energy is not exclusively related to mass...quantum energy is very much a recognized form of energy, but it has no mass. A gravitational field has no mass...neither does a magnetic field- yet these are both forms of energy. The same is true of electron energy levels- the photons that bump electrons up and down energy levels in the electron shell are effectively mass-less. And since photons are certainly one of the means by which light travels, then it is a form of energy that has no mass. E=mc^2 merely represents the relationship of mass with energy, the manner in which is arranged is somewhat misleading perhaps. Maybe if we looked at it like this: m= E/c^2 , we begin to appreciate that this is in fact, a one-way street. For entities without mass, that equation does not apply, simply because it's the relationship of mass to energy such as is dependent on one's velocity.

Hope that cleared a few things up

Occy

bonkey

Originally posted by ][cEMAN**
Then explain why light refracts off the different layers of the out hemisphere and ozone to change colour or slow down and become visable in the colour spectrum.

In simplest terms...because light, as energy, can interact with other things....which are also energy.

Remember, energy sits "at the bottom" of the descriptions. It is about as simple as things can get

Pretty much everything can be expressed as energy, this does not meant that energy must be everything....or any one thing in particular.

Though Energy must ALSO have mass otherwise what is this energy? where did it come from? energy can not jsut be created it has to be transformed or passed....can only be done through mass.

No. "energy" is the base. mass is a form of energy, as are all the other types of energy, such as electromagnetic force, etc.

The whole thing about an atomic bomb works because a tiny amount of mass if *converted* into a massive amount of energy. This could not hold true if energy had mass.

The law of conservation of energy states that energy cannot be created or destroyed, only converted from one form to another. Mass can be destroyed - it can be converted to energy. Light can be destroyed - it can interact with other things to be converted into heat, mass, and so on.

Energy cannot be destroyed - it is the "base definition".

If you're a programmer, consider energy as the base class, with mass as a derived class. Light is another derived class - a different expression of energy. There is no requirement for light to have mass - there is a requirement for both light and mass to be forms of energy. The requirement does not hold the other way round...energy does not *have* to be massive, nor does any "derived" energy other than mass itself.

jc

][cEMAN**

OK then Occy i'm curious - what causes a grvitaional field? Is it not 2 masses interacting from a distance?

What causes a magnetic field - when you have a wire wrapped around a rod does it have a magnetic field before you pass electricity through it?

As for light being pure energy....why then is it affected by gravity? Gravity affects mass does it not? Or are we dealing with such star trek terms as gravitons etc (i'm not making fun i'm asking a serious question).

Energy as you put it as light eminates from the sun - but why does it move in a straight line? Why not just sit there in space and not go anywhere near earth? Isn't it more that the outter crust of the sun is so hot that it gives mass enough energy to escape the immense gravity field and the travel in a certain direction?

I mean I thought we were working off the basic rules that every action causes an equal and oposite reaction whereas something in space will only move if forced to move. Now gravity would be one reason, but you compare earth's gravitational puling power to the sun and I doubt that's the reason.

As for light can be DESTROYED and energy can be DESTROYED - it's NOT destroyed....as you say yourself it's converted. You can't destroy or creat energy.

If a pen falls off a table and hits the floor energy is NOT destroyed. It started with potential energy from it's height (or rather distance from the earth - gravity) and as it falls some of that energy is converted to mild heat due to air friction (not that we could tell from our senses) some to sound (so quiet you don;t hear it) and then when it hits - mainly noise but again some small amount of heat.

When the noise travels it doesn't dissappear - sound cannot travel in a vacuum as it is dependant on contraction and expansion of particles - through open spaces it would be air. So it converts from sound to heat within particles which heats up the air though again not detectable by our senses.

Sorry am I going off on a tangent again?

nesf

Right, forget your secondary school definition of gravity for a sec, and use the general relativity version, i.e. it bends space time, now since light follows a route in spcaetime it is also effected where the spacetime is effected. The gravity doesn't directly effect light, it effects the medium (in a sense) through which light travels.

Light moves due to electro-magentic forces. The whole maxwell's equations etc et al. Tbh, you'll have to read up on this yourself, I don't feel like trying to explain it.

Occy might know a good site or two, I can't think of one at the mo.

Gargoyle

Originally posted by ][cEMAN**
OK then Occy i'm curious - what causes a grvitaional field? Is it not 2 masses interacting from a distance?

Not really. Its very difficult to explain, but to try and put it into non-mathematical terms, think of it this way. We now know that, relativistically speaking, masses cause a curvature of space-time, again, not an easy thing to explain. An analogy might be like two birds setting off from the equator in different directions , but going south. Eventually, at the pole, those birds will begin converge. They might interpret that as a force, and in gravity's case, it may even be simply explained mathematically (albeit only in a 2 particle system), but the more correct way to see it is as the curvature of the Earth is actualyl bringing the birds together. Hope that makes some sense.

What causes a magnetic field - when you have a wire wrapped around a rod does it have a magnetic field before you pass electricity through it?

no, magnetism is caused by moving electrons.

As for light being pure energy....why then is it affected by gravity?
Gravity affects mass does it not? Or are we dealing with such star trek terms as gravitons etc (i'm not making fun i'm asking a serious question).

Think of the massive gravitational well bending the space in close proximity to it. This is a relativistic effect and not easily explained without the math, but that's the best I can do.

Energy as you put it as light eminates from the sun - but why does it move in a straight line? Why not just sit there in space and not go anywhere near earth? Isn't it more that the outter crust of the sun is so hot that it gives mass enough energy to escape the immense gravity field and the travel in a certain direction?

The fusion rxn inside the sun is constantly producing energy. Thermodynamically speaking, areas of higher energy will generally tend to diffuse to areas of lower energy. The primary form of energy that can propogate away from the sun in a vacuum comes in the form of electromagnetic waves, ie. light, uv, ir.

I mean I thought we were working off the basic rules that every action causes an equal and oposite reaction whereas something in space will only move if forced to move. Now gravity would be one reason, but you compare earth's gravitational puling power to the sun and I doubt that's the reason.

no comment

As for light can be DESTROYED and energy can be DESTROYED - it's NOT destroyed....as you say yourself it's converted. You can't destroy or create energy.

Bravo except for the last part, you can create energy from mass unless you consider the mass's rest energy to be a form of potential energy, of course not an assumption generally made in the classical sense. Its almost a matter of semantics, but most say you can create energy from mass and that it is the whole basis of the atomic age...

If a pen falls off a table and hits the floor energy is NOT destroyed. It started with potential energy from it's height (or rather distance from the earth - gravity) and as it falls some of that energy is converted to mild heat due to air friction (not that we could tell from our senses) some to sound (so quiet you don;t hear it) and then when it hits - mainly noise but again some small amount of heat.

True

When the noise travels it doesn't dissappear - sound cannot travel in a vacuum as it is dependant on contraction and expansion of particles - through open spaces it would be air.

More like propogating a wave through a group of particles rather than contracting and expanding individual particles, but close enough.

So it converts from sound to heat within particles which heats up the air though again not detectable by our senses.

yep

Sorry am I going off on a tangent again?

Not really. Did you take any physics in your undergrad degree? I'd say you have more of a grasp of it than most people do. It helped me to read Stephen Hawking's book, A Brief History of Time, even though I did an undergraduate degree in Physics.

There are probably very few people in the world who truely understand relativity, and I am certainly not among them, but I hope I was able to shed a little light on your questions.

bonkey

Originally posted by ][cEMAN**
As for light being pure energy....why then is it affected by gravity? Gravity affects mass does it not? Or are we dealing with such star trek terms as gravitons etc (i'm not making fun i'm asking a serious question).

Actually, gravitons are far more than a "star trek term". They play a key role in may new emerging theories, such as superstring theory.

As for why light is affected by gravity...

Out current understanding says that mass "distorts" dimensions in space-time. In less dimensions, the classic example is placing a weight on a rubber sheet. light travels in a straight line, but just as a ball bearing launched across the rubber sheet can get its trajectory moved by the presence of a large weight on the sheet sufficiently close to the ball, a large gravitational force will apparenty deflect the path of light in space-time as well.

Now, getting back to the original erquest for reading material :

Hawking "Brief History" is actually not a bad read, but I prefer his "black holes and baby universes" book. Another good read (which I'm currently on) is The Elegant Universe by Brian Greene, which deals mostly with Superstring theory, but which does a really good "background" for a few chapters on the fundamentals of special relativity and quantum theory.

jc

Gargoyle

I find string theory to be an incredibly difficult concept to understand. Dimensions wrapped inside tiny strings thinner than the deBroglie wavelength of an electron in a TEM? I don't know about that one.

Seems like a little bit of mathematical hocus pocus rather than a likely reality. But, if the strings are that small and really do exist, there's (conveniently) no way to detect them...

But, you never know.

][cEMAN**

Thanks for the book references - i'll have to take a look at those. I've been meaning to get some theory text to look through. These books might be a good read as well.

As for my knowledge of physics.....well no I didn't do it as undergrad I did maths but never finished it because 1. It didn't meet the filed of work I wanted 2. In the tutorials I seemed to know more than the people running the course (not a good sign) and 3. Because when I failed 1 "Pure" maths modul in first year, though it was only a 3rd year prerequisit they changed my course from a masters degree in maths to maths and computers joint because it gave them more money.

You'll probably not be surprised to know I got an N on my A-level physics. Though I think that might be down to a paper that was unmarked. Reason I think this is that I was still rated as a definate C grade by my teacher though I did everything to act stupid in class (just to piss him off) and I had thought it was the best exam I had ever sat on physics - all 3 papers.

But then maybe i'm using more imagination rather than reason and logic.

nesf

Persoanlly I have to admit, not liking Hawking's Books, I found them too angled towards non-physicists. I prefer Michio Kaku's work, or at the moment I'm reading "The Cosmic Anthropic Principle" by John Wheeler and another guy whose name I've forgotten.


As for string theory... well it's very complex. I don't even have a half decent understanding of the main concepts involved. I do understand some of the maths and some of the areas involved. Knot theory for instance is a very interesting topic within maths. But that aside, the concpet of a world sheet rather than a world line, is possibly the most basic concept within string theory.


Tbh it's the natural order of physics to resolve itself into very simplistic models, based on relatively simple concpets. In this case the vibrating string, which is easy enough for a 2nd level student to fully comprehend, can be used to explain the creation of the universe.

You've got to like that kind of simplicity at such an advanced level of physics