What can spectra tell us about temperature?

1. source 1 shows the emission spectrum of Earth. This is a spectrum of the thermal radiation emitted by Earth because it has a temperature.

   Note: Use the wavelength stretch slider to bring the spectrum into view.

2. Under source 2, use the Select thermal model dropdown menu to find the temperature with a spectrum that provides the best match to the Earth's emission spectrum.

Note: The y-values of these model spectra are not plotted on the same scale—they have been modified so they can all be plotted in the range of the tool. The key is to compare the overall shape of the curves, and most importantly, where the peaks are.

1. What temperature thermal spectrum best matches the spectrum for Earth's emission?
2. Convert the temperature you identified in Question 1 from Kelvins to Celsius. (This will give you a better intuitive sense of what this temperature represents.)

   (Temperature in Celsius = Temperature in Kelvins - 273)

3. What type of light does Earth emit?
4. Given that Earth does not emit its own visible light, how are we able to see Earth from space?

   Hint: Recall that the key behaviors of light include emission, reflection, absorption, and transmission.