Tufts OpenCourseware
Author: Fulcrum Institute Development Team


What about radiation?

You’ve all probably heard that there are three modes of heat transfer – convection, conduction, and radiation.

In convection, energy is transferred by the motion of the particles (i.e. atoms and molecules) in the material.

In the case of conduction, energy is largely transferred by atoms jiggling about their equilibrium positions – heating one end of a bar causes the atoms near that end to jiggle more violently, and disturb the neighboring atoms. In this way the energy moves through the material.

But thermal energy can also be transferred without any material to transport it by a process called radiation. For example, the sun’s energy reaches the Earth even though, to all intents and purposes, there's nothing between our planet and the sun. Life on the planet depends on the energy that reaches us from the sun - How does that energy get from the sun to here?

This Week's Plan

The question this week is – Is there energy transfer without matter? To address this question, you'll use your senses (your hand) and probes to find evidence of energy gain and loss as indicated by temperature change. The challenge is to sort out the contribution of radiation to both heating and cooling when it's acting together with conduction and convection.

You'll devote much of your time this week to analyzing and discussing data. You'll use your own first hand experiences to inform your analysis of data collected by yourself and by others as you look for evidence of energy transfer by radiation.


  • Find evidence that heat can be transferred in the absence of matter
  • Understand that every object (with a temperature above absolute zero, i.e. -273° C) transfers energy by radiation
  • Understand that there can be thermal equilibrium between the absorption of energy and the emission of energy even in the absence of matter

What you need from your kit

  • Temperature probe
  • Clear 100 watt light bulb
  • Clamp light (to move hot objects)
  • 2 stainless steel clips
  • Silicon-tipped tong
  • Support stand with 3/8 in. rod
  • Thermometer clamp for rod
  • Small tabletop fan (optional)

Session Resources