# Thermal equilibrium

1. Dec 28, 2014

### nmsurobert

So you take some boiling water and drop a metal cube into it and the cube will reach the temp of the water. Or you leave some hot water out on a desk and the water will eventually become room temperature, right?

Then why, in the summer time, does the inside of the car get way hotter than the temperature outside of it?

2. Dec 29, 2014

### gianeshwar

One reason to get hotter on sunny day is that the Sunlight of lower wavelength gets trapped in and then due to the fact that now higher wavelength EM Waves cannot go out and hence temperature inside gets higher(greenhouse effect).

3. Dec 29, 2014

### nmsurobert

Oh ok. It must be something beyond my current physics knowledge then because that explanation didn't help much haha not insulting you just saying I'm not at that level.

4. Dec 29, 2014

### Staff: Mentor

Sunlight shines in through the glass, heating the seats and the dashboard and whatever else it shines on. These then heat the air next to them, and the inside of the car gets warmer. It's no different than running the car's heater to warm up the air in the car - as long as the heater is going, the interior will be warmer than the outside.

The same thing happens to anything you leave out in the sunlight - the sun warms it, then it warms the air it is touching. You just notice it much more with the car because the closed windows keep the air trapped inside the car so the heat can build up.

5. Dec 29, 2014

### nmsurobert

But why doesn't the car stop heating once it's at the same temperature as the outside. That's what I'm hung up on.
I didn't think to compare it to the green house effect. I'll do some reading on it to make sense of it now that I know that.

6. Dec 29, 2014

### gianeshwar

Glass does not allow the inner heat(infrared EM radiation of longer wavelength) to pass and hence internal energy of inside increases.
I think it may also be in conformity with adiabatic process.
Why we are able to survive on the earth is also due to the effect of greenhouse as the atmosphere keeps heat trapped.
Now if your question is why glass does that, it needs to be enquired.