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### What is the maximum possible temperature of a 1mx1mx1m cube that is the focal point of an array of mirror reflected, concentrated beams of sunlight? [duplicate]

If we assume an array of 1m x 1m mirrors reflecting sunlight in an Alabama field to a common point, what would be the maximum possible temperature that could be reached? How many mirrors in this ...
20k views

### Is it possible to start fire using moonlight?

You can start fire by focusing the sunlight using the magnifying glass. I searched the web whether you can do the same using moonlight. And found this and this - the first two in Google search ...
223 views

### Laser beam focus

Why isn't it possible to focus a laser beam to an infinitely small point in space? I am familiar with the shape of a gaussian beam, but why can't my $w_0$ be equal to zero?
1k views

### Conservation of energy when focusing black body radiation on another black body

This question about whether or not it is possible to focus black-body radiation to make something hotter than the radiation's source was answered mostly negative: the second law of thermodynamics and/...
2k views

### Is Randall Munroe's "what-if" xkcd correct that magnified moonlight can't get things hotter than the moon? [duplicate]

Note: I am NOT asking if moonlight can be used to start a fire. I am asking whether these particular arguments in support of the claim that it cannot are correct. i.e. I'm looking for an answer that ...
1k views

### Can you use sun light to heat an objects surface to hotter than the surface of the Sun? [closed]

I was reading this question: Concentrating Sunlight to initiate fusion reaction and some of the comments, as well as an answer, suggest that thermodynamics second law prevents what I ask in the title. ...
2k views

### Temperature increase from focusing light using a lens. (Equations required)

Could someone please quote and explain the Equations required that I would need to calculate the temperature increase of an object with a lens focussing the light from a celestial body. Therefore ...
103 views

### Lens-Mirror systems and conservation of specific intensity

This came out of a discussion I started yesterday and a related discussion I found. I'll recap the problem quickly: Consider two blackbodies, with surface areas $A_1$ and $A_2$ and temperatures $T_1$ ...
11k views

### Highest temperature possible to achieve using magnifying glass and sunlight [duplicate]

Temperature of the surface of the sun is about 5750K. Can you heat an object to more than 6000K using magnifying glass and sunlight? According to second law heat cannot be transferred from colder to ...
92 views

### Simple thermodynamic proof that light from a source cannot be focused to heat an object above the source's temperature

I was thinking about the question in the title. I found the following thread, and some of the answers are making my head spin! Is it possible to focus the radiation from a black body to make ...
147 views

### Solar Power Fusion

Would it be possible through a clever arrangement of solar dishes, lenses and mirrors etc, to create fusion at the focal point? Imagine you arrange your solar dishes, lenses and mirrors in such a way,...