[alancalverd]

So I'll ask now. You aren't allowed to measure any temperatures, because that would exclude potential energy. 

I know how to calculate all sorts of things that involve energy and energy transfer, but I can only sort-of-directly measure the energy of a photon.

[Bored chemist]

The problem is you forgot that chemistry happens.
How to measure energy?
Ask the experts
https://energysavingtrust.org.uk/advice/guide-to-smart-meters

Well maybe not quite "experts"...
:-)

[alancalverd]

Smart meters measure power and integrate it to give you an inflated idea of energy input. They don't measure energy.

I did indeed have a chemical power integrator some years ago but it wasn't particularly accurate. Quite handy and a lot of fun as a low-power run-time integrator with a moving color band.

 

[Bored chemist]

to give you an inflated idea

In what way?
I  accept that the supply company rips you off, but that's different.

[hamdani yusuf (OP)]

Here are some videos about negative temperature.

This video shows what makes laser different than other sources of light.

[Bored chemist]

This video shows what makes laser different than other sources of light.

We already know.
Why post the vid?

[hamdani yusuf (OP)]

This video shows what makes laser different than other sources of light.

We already know.
Why post the vid?

It contradicts your statement.

[alancalverd]

The source may well be different, but a photon is a photon.

I've just watched that last video. If that is the quality of  modern physics teaching, the next generation is doomed to a life of ignorance and superstition.

[hamdani yusuf (OP)]

The most distinctive feature of laser over the other light sources is coherence. So it is possible to superpose many of them without producing destructive interference.
It can not be done if the source is incoherent.  That's why focusing sunlight can't get higher temperature than surface of the sun.

[hamdani yusuf (OP)]

The source may well be different, but a photon is a photon.

And it's just a mathematical model.  No one has isolated it, AFAIK.

[alancalverd]

I have equipment that counts them individually.

[hamdani yusuf (OP)]

I have equipment that counts them individually.

How do you know that it does indeed count a single photon, not less nor more, and not counting something else?

[Bored chemist]

AFAIK.

That is the essence of the problem with many of your posts.
You just don't K very F because you fail to learn.

This video shows what makes laser different than other sources of light.

We already know.
Why post the vid?

It contradicts your statement.

Not as far as I can tell.
Which bit is troubling you?

[Bored chemist]

The most distinctive feature of laser over the other light sources is coherence.

I take it you didn't understand this.

You can't really make holograms without coherent radiation. (Ok, technically, you can but it's doing things the hard way)
And yet, Gabor invented and demonstrated holography without using a laser.
https://en.wikipedia.org/wiki/Dennis_Gabor

[alancalverd]

I have equipment that counts them individually.

How do you know that it does indeed count a single photon, not less nor more, and not counting something else?

Something to do with quantum mechanics, I guess. And the fact that the counting stops when I switch off the source.

[hamdani yusuf (OP)]

AFAIK.

That is the essence of the problem with many of your posts.
You just don't K very F because you fail to learn.

This video shows what makes laser different than other sources of light.

We already know.
Why post the vid?

It contradicts your statement.

Not as far as I can tell.
Which bit is troubling you?

why focusing sunlight can't get higher temperature than surface of the sun.

Why focusing laser can?

[hamdani yusuf (OP)]

The most distinctive feature of laser over the other light sources is coherence.

I take it you didn't understand this.

You can't really make holograms without coherent radiation. (Ok, technically, you can but it's doing things the hard way)
And yet, Gabor invented and demonstrated holography without using a laser.
https://en.wikipedia.org/wiki/Dennis_Gabor

Do you understand the difference between hard and impossible?

[hamdani yusuf (OP)]

I have equipment that counts them individually.

How do you know that it does indeed count a single photon, not less nor more, and not counting something else?

Something to do with quantum mechanics, I guess. And the fact that the counting stops when I switch off the source.

Does temperature of the detector affect the counter?

[Bored chemist]

AFAIK.

That is the essence of the problem with many of your posts.
You just don't K very F because you fail to learn.

This video shows what makes laser different than other sources of light.

We already know.
Why post the vid?

It contradicts your statement.

Not as far as I can tell.
Which bit is troubling you?

why focusing sunlight can't get higher temperature than surface of the sun.

Why focusing laser can?

I didn't say anything about the temperature you can get by focussing a laser or the sun.
How did you come to the conclusion that the video contradicts what I said?

[Bored chemist]

Do you understand the difference between hard and impossible?

es,  in this case "difficult" means constructing a hologram by computing the array of light and dark patches you need to form a hologram and then somehow "panting" them onto something.
on the other hand, "impossible" is making a hologram in the "normal" way - i.e. using an interference pattern to make that pattern.

Why is it that, whenever you don't understand something, you assume that it's me who doesn't understand?

It's impossible to make "conventional" holograms without coherent light.
Gabor did it without a laser.
Therefore it is possible to get coherent light without a laser.

Therefore the wiki article isn't quite accurate.