Strange

I guess the negative points are not for "wondering" but for rejecting answer based on science and making up your own based on .... well, nothing beyond personal preference. I thought the temperature had always been the same. There is no such thing as "pure energy" but never mind. But, yes, the matter could all turn into radiation - we have no way of knowing. But that doesn't make much difference. It still contributes to the mass of the black hole in the same way (remember, mass and energy are equivalent). And it still has no path away from the centre of the black hole. Because there is (as far as we know, currently) no way for the black hole t explode as you suggest. One way of seeing the difference is that the singularity in the Big Bang model is in the past while the singularity in a black hole is in the future of any mass (or energy) inside the event horizon (because space-time becomes so curved that the radial dimension is swapped with the time dimension). [Not that there is any reason to think that singularities exist in either case.] Galaxies were formed much, much later than any Big Bang event [and there is no evidence for such an event anyway]. Simulations of how the matter in the early universe cooled and formed large scale structures show that galaxies are formed by the gravitational collapse of matter, not by explosions. LIGO has detected 5 (I think) black hole collisions so far. [Note that the gold and other heavy elements were created from the matter (and energy) already resent. It is not being created "from nothing".]

I tried to explain why it doesn't matter. Sorry if I wasn't clear. Let me try again. Let's take an example. Say we do some experiments to confirm some basic aspect of physics, for example Newton's F=ma (force = mass times acceleration). So we set up our lab bench with instruments that measure the force applied to a variety of object and measure the resulting speed (and how it changes with time). We also have a precision scale to measure the mass of each object. We can do hundreds (with automation, maybe millions) of such experiments and plot the results. Taking into account errors in our measurements we will find the numbers all match Newton's equation. Does this tell us that mass is "real" and that Newton's law says something about "reality"? No. Does it disprove (or prove) that we are in a simulation? No. Does it disprove solipsism (that all these experiments and results take place purely in our own mind)? No. All it tells us is that if we do those experiments and make those measurements, we will get those results. That could be because we are part of a simulation set up to produce those results. It could be because our mind has dreamt up the lab bench, the instruments, the concept of mass and Newton's law. It doesn't matter what the nature of reality is, or whether it even exists. As long as we continue to make measurements and get consistent results, we can "do science". We may not be studying the "real world"; we may only be studying a figment of our mind; we may only be probing an alien simulation. It makes no different to that science does. As we can only ever probe "reality" by using our sense, we can't know what reality "is" beyond what our senses tell us. But if you have a way of knowing things without relying on our senses, then (instead of having a little tantrum) explain what that is. That implies you know the difference between a simulated world and a real world. But how would you now that? If we are in a sim, that is all we know and so that is our reality. You ca't step outside the sim and see what reality looks like to compare it to what we experience. We experience one thing. It may be a sim or it may be reality. Without something else to compare it to, you can't tell which. [Full disclosure. I am a naive realist. We are obviously not in a sim. That is a stupid idea. What we perceive is what the world is really like (more or less). There is nothing else beyond the physical world that we see around us.] You asked a question of philosophy in the Philosophy section of the forum. You got appropriate answers, not scientific ones.

"inconsistent"

The diaphragm makes no difference to that. None of the image will be blocked.

Is this "too theoretical" because it is not for a specific lens: How about this description of a specific Canon lens: http://www.exclusivearchitecture.com/?p=853 This is the source of one of the images I posted earlier so I assume it is somehow "too theoretical" (whatever that means - I assume it is just an excuse to drag the thread out and ask increasingly stupid questions until either you or the moderators get bored). You might be able to buy broken lenses cheaply. Then you could take them apart to find out where the diaphragm is. Or just go to a camera shop and look at the lens. You can often see the diaphragm near the front of the lens:

Actually, I haven't mentioned depth of field. That is more complicated to understand. You are right. And that is also the position of the diaphragm.

Except the question doesn't make sense. What do you mean by "(last) focal point". For an object that is in focus, the focal point (more realistically, focal plane) is on the film. Of course you do. Bless.

If my answer "make sense" what else are you looking for? You have a habit of not asking what your really want to know. Are you looking for the details of how a camera lens with multiple elements works: what each element is there for, etc? Like a more detailed version of this: This one shows the position of the diaphragm

The image is formed by rays passing through all parts of the lens. From each point of the scene, rays will pass through each bit of the lens and arrive at the same point of the film (assuming the image is focussed!) So, if some of the lens is covered, the mage is still formed in the same way, but just with fewer rays (less light). The field of view is determined solely by the focal length and the size of the film (or sensor, nowadays). Here is a simple diagram. Person being photographed on the left, lens in the middle, film on the right. Dotted lines are some example rays from the object to the film. To avoid confusing things, I have just shown how the rays from one point get from the person to the lens. There will, of course, be rays from every point to the corresponding position on the film. Lets add a diaphragm: You can see that some of the paths for the light are block but that doesn't change where light comes from. Just the amount. I assume this a complete waste of time though. As you don't seem to understand the first thing about how light, lenses or sight works in the first place. The diaphragm is normally placed as close to the lens as possible. In fact, because real lenses are complex compound lenses, the diaphragm is usually inside between the components of the lens.

How does a question beginning with "if", and therefore presumably completely hypothetical, count as "good general knowledge"? Even if there were any basis for your bizarro speculations, I can't imagine who would be interested. Ditto sources/references for the assertions they are based on.

I suspect Dalo doesn't believe in the wave theory of light (and presumably nothing else science says) and thinks that by asking "difficult" questions he will make us realise it is a house of cards. The trouble is, people who think that science is that fragile don't realise that it is actually a complex self-supporting structure rather than a pencil balanced on its point. Just before or after that colon, I suspect.

Why? Do you have any rational or mathematical argument against it? Or just an argument from ignorance: "I don't understand it so it must be wrong". I'll take that as a no.

What do you mean "presupposes"? Are you suggesting that light is not a wave phenomenon? Is that the point? I didn't realise. I thought it was just your inability to understand what a wave was and how a diffraction grating worked. But, of course it is legitimate. It is just simple schoolboy geometry. Good.

The only thing it has in common is the use of interference. It is a lot simpler and it is a direct measurement of the wavelength: the distance you move the mirror to go from one peak of constructive interference to the next is a wavelength (well, half).

Here is one: http://www.planet-science.com/categories/over-11s/physics-is-fun!/2012/01/measure-the-speed-of-light-using-chocolate.aspx (I have never tried this; I don't have a microwave oven.) Another (much more accurate) method is to use an interferometer: http://physical-optics.blogspot.co.uk/2011/06/michelsons-interferometer.html

And from that measurement, one can calculate the wavelength. (There are ways of directly measuring the wavelength as well.)

Not sure what the point of that post was but ... in that diagram, the wavelength is the distance between the blue lines, not the red arrows.

I knew ... uh, should have known ... that. I guess the hot water example can be described in terms of the increased kinetic energy of the molecules but the net momentum is, again, zero so all observers will agree on the energy increase.

Indeed. Optimism can drive people to work out solutions to difficult problems, but it isn't a replacement for action (as some Brexiters seem to think).

Ah, I see. You mean solitons?

I did wonder about the rotational aspect when I made my comment. So are you saying that an object can rotate fast enough to turn into a black hole? This seems reasonable (I am reminded of another thread where it was pointed out that the time dilation of an object in a centrifuge could be described equivalently as either a gravitational effect or in terms of [rotational]speed.)

Rather like all the Brexit campaigners in the UK who, when the complexities and costs of Brexit are raised, just tell people not to be so negative. "It will all be great". Well, maybe it will be but that doesn't mean we don't have to solve all the problems first.

By "solitary waves" do you mean a single cycle of the waveform? But if it has a wavelength and a speed, then there must be an associated frequency. (Although, at the risk of causing more confusion, this will obviously a wide range of frequencies if the waveform is truncated to a single cycle.)

I wonder if the difference between the colour temperature of the screen and the ambient lighting is significant. I have also turned on the "night mode" (or whatever it is called) on laptop and phone. Not because I had noticed any problems sleeping but just because I found the increasingly blue light (as the ambient light got warmer) quite jarring by itself. Your eye has to focus at different distances for different wavelengths so I wonder if that could be a cause of discomfort.

The distance between the interference fringes is not wavelength. Although it can be used to calculate wavelength as described earlier. What objection?