studiot

Flat does not refer to thickness (nor length nor breadth, nor width.) It refers to the way distance is measured between one point and nearby points.

Several members have told you useful things that anyone genuinely interested in Physics would wish to know or, if they did already know, then simply say a friendly 'yes I have come across that' or wording to that effect. You either ignore these things that are said to you in good faith or argue with them. Is that a good strategy?

You have already been told that 'u' is not a word in any English dictionary.

That is exactly what I did say. From what I can see you do understand reasonably good English, you just aren't prepared to use it. Don't you think that is rude to other members here?

Since you can't seem to read either your own writing or mine let me try again I have underlined the part of my post where I told you just exactly where that incomplete bro lies.

No, it is you who is wrong. The photon does not have dual nature. The photon is a particle. But light has dual nature since aspects of the behaviour of light are consistent with wave theory and with not particulate theory. By the same token, some aspects of light are only consistent with particulate theory. And we call those particles that observe this behaviour, photons. I am disappointed that when I pointed out the only maths equation you have quoted so far (in your opening post) is incomplete and you are completely silent on that subject.

Good research silvestru. +1 Too many people argue against Einstein, 'quoting' what he did not say. ovi issac You seem to think that the popular phrase energy and mass (or matter) are equivalent mean they can be interchanged at will. That is not the case. In fact the popular equation E = mc2 is only part of the full relativistic equation. Have you studied the maths of relativity?

It is up to you to make yourself clear.

Well you seem to be mixing up mass and energy in any old way. Relativistic mass is not the same sort of property as ordinary mass. And I still don't see a question if , as you say, your question is not Where does the energy come from?

Please rephrase this, it is quite garbled English.

Is this your actual question that you would like answered? Think about the answer to this question. I throw a ball into the air. Where does the energy for the ball to acend come from? The answer is the same as the answer to your question. From whatever causes the motion. In the case of a photon it starts off life with a fixed energy and can never change this.

Schools in England (Scottish, Irish schools start a little earlier) have just restarted so this child will be in her first couple of weeks of secondary school. And yes an 11 year old could easily have started this year, that's nothing new. I started at 11, it depends upon your birthmonth. However in my day we only did 'general science' in the first one or two years (can't remember which now) and very little practical at that. There was not enough time on the timetable to separate the sciences. I had a choice of German or Chemistry when the reduction towards GCE came. But I return to the point about supervision. This child has had now many Chemistry lessons? A couple, three at most. And she was asked to pour out a chemical that is listed as a potential hazard to health in the safety regs. As I recall glass rods were taught for this process and a swift surf shows this is still the case. Had this been done in this case? A word for John, My apologies I'm still trying to get the hang of the new quote system here - it fights back and doesn't always behave as one might like or expect - and something obviously went badly wrong as the wrong quote was included in my reply to you. No wonder you were a bit confused about it.

MacSwell is correct, 'flatness' is a local property of the manifol;d under GR. SR is flat anyway at all scales. I am defining 'flatness' as synonymous with zero curvature. That is it is a point function with a value at every point of the manifold. However it should also be noted that there is more than one curvature (direction or degree of freedom) for a 3D manifold. Since we do not know the shape of the manifold we cannot say for certain that the answer to the OP is yes or no. This is because the value of the curvature at some points in some manifolds can be zero for example saddle points in 3D. If our universe has such points then the answer is yes something could be truly flat. If it does not then no. Edit Another thought. Since (the disposition of) matter is responsible for the curvature and matter is always moving about in our universe I can conceive of a situation where the local curvature reverses and thus passes through zero at some point or interval in time.

Deacon, a good solution, but don't you think it a tad explicit for homework help?

I have also answered this. It is not I but the regulations you posted that specifiy the gloves. Yes, as you said, it was the interpretation of an old and very well repected University Chemistry department, no doubt assisted by a very able legal department, The department of Chemistry at the University of Leeds. There are you satisfied now?

Yes, I did. And you are right, they do tell you that gloves should be suitable. That's why I posted them. Why did you post something that doesn't say that gloves must be suitable? Do I have to answer things twice? I do take your point about the eye protectors, but it may well be the case in that lab, as in all school and college labs these days, that eye protection is mandatory at all times so not specifically included in any instructions specific to one experiment. So the eye protectors may have been there as a general precaution. Wouldn't it just be so much easier if post numbering was reintroduced?

Presumably you also have something to hang the device from or stand it on or tie it to? A good way to start would be to make a list of exactly all the things the device must do (and not do) in sequence as the egg is dropped into or onto it. Then you can talk about each one of these separately to make them happen.

Gosh John, did you not read the regs you posted? Gloves are classed as personal protective equipment, so perhaps you should ask your granny about the suitability of her gloves. Did you read the instructions I posted Specifically it does not say that. The COSHH assement specifically says you should dispose of the acid in a fume cupboard. Although As to the use it says "add 10 drops of the acid with a pipette. It does not say "pour out the acid from a bottle into a test tube." We still don't know why the girl was doing this or, in truth, a good deal more about the circumstances. I am more concerned about the circumstances that lead to the incident, than the incident itself which could have been more serious, and points to insufficient supervision IMHO. The girl may also have more sensitive skin than you do, or did at her age. When the students come to use a large volume (stil only 50 ml) of the acid they not a small test tube. I do take your point about the eye protectors, but it may well be the case in that lab, as in all school and college labs these days, that eye protection is mandatory at all times so not specifically included in any instructions specific to one experiment. So the eye protectors may have been there as a general precaution.

Indeed yes. Here are the relevant UK regulations Control of substances hazardous to health or COSHH regulations. https://www.chem.leeds.ac.uk/fileadmin/user_upload/yr12_practicals/Y12_Inorganic_2016_Final_version.pdf

Looks like she had a lucky escape. Has anyone put some cream (eg Nivea) on it?

Did your daughter scratch at the site of the splash? Not a good idea as that would rub the acid in. You didn't say if the teachers immediately washed tha acid off? Or did someone just wipe it off and then leave it? 1M is not that strong for a near adult, but what was an 11 year old doing with it and what was the supervision? By way of contrast car battery acid is 4M to 6 M and would definitely burn straight away. Here is a company Health and Safety document which regards 1M as "corrosive to skin" http://www.onboces.org/safety/msds/S/Scholar Chemical/Sulfuric_Acid_1.0M_740.00.pdf

Get hold of this book http://press.princeton.edu/titles/8861.html It exactly fits your bill. BTW Sears and Zemansky have various books that are streets ahead of the Resnick & Halliday, even as edited by Young and Freedman.

Your are too suspicious. I am trying to work through the physics of something with you so that that you can see for yourself what the facts are. It is fundamental to wave theory that a point source produces a spherical wave that spreads out in all directions. So a point source on the surface of the Sun (Point P in my fig1) creates an expanding spherical wavefront as I have shown dashed in Fig1. This has an average radius of 150 million kilometres by the time that front reaches Earth. The source at P does not have a choice in this, nor does it have collimators or focusing devices. But yes there are many such sources on the surface of the Sun and they are not coherently phased, like a laser. (Thank the Lord Huygens) or we would not be here if they were. I said that as a result of that distance that wavefront is effectively a plane wave so the (very simple) maths of this is shown in fig2. The deviation of a circular curve from a straight line is given by the formula (distance along the straight line squared) divided by (twice the circle radius) With the figures shown this works out at about one tenth of a millimetre over the linear distance of the radius of the Earth. So think how much straighter the wavefront must be over the size of a carbon dioxide molecule, whose bond lenght is 1.16 x 10-7 millimetres long. This is why we can say that in another model - that of geometrical optics which treats light as a series of 'rays', that the rays from the Sun are parallel. I mentioned bond length of carbon dioxide which is important because this determines the frequencies for the four fundamental modes of vibration of the molecule. The plan is to fully understand how a straight radio aerial works and see if we can use this to understand how the stretching modes of the carbon dioxide bonds comes to be in the IR and microwave bands and not other bands of the EM spectrum. But first we must look at your thoughts on how a radio aerial actually works. This is not far off the truth but just need a couple of amendments. I have underlined the relevant bits. Firstly and most importantly. Forget resonance - the word will get you into trouble when we consider charge separation in the carbon dioxide molecule. It has a specific and quite different meaning for chemists and bonding. The radio waves induce current in any conductor of any length. Resonance is not required. The issue is what happens to those currents when they have been induced. We shall see that conductor length then becomes vitally important. I prefer the phrase charge separation, rather than current because that is what happens in both the radio aerial and the carbon dioxide molecule. The effects are potential driven, not current driven. Finally we spoke about reflection, absorbtion and transmission. What about refraction and diffraction of waves? I think we are doing well and making real progress

I agree with iNow - to quote the old phrase "There's none so blind as those that won't see and none so deaf as those that won't listen."

Surely if he admits it doesn't have to then you can challenge him as deceitful. Ask why did he use something he knew to be false as a challenge, instead of offering proper evidence or reasoning.