How does radiation pass through a vacuum?

Question

I understand the difference between conduction, convection and radiation, and I understand the equations of radiation, but what I just don't undersand is how an object can be heated up by radiation when there is nothing physical moving from the heat source to the object.

If Einstein showed that energy is equivalent to mass, then when the object heats up, it gains energy, therefore the radiated source must have transmitted it through the vacuum. So what travelled through space, mass or energy, or both?

Answer 1

Radio waves, radar, lasers, visible light, infrared and ultraviolet light, microwaves, X-rays and gamma rays, all travel as mass-less tiny packets of energy (photons) at the speed of light. They can all easily pass through a perfect vacuum (as could a bullet!). In fact photons interact with the electrons orbiting atoms and molecules and can be absorbed kicking the electrons into higher more energetic orbits or entirely out of the atoms during ionization. When electrons return to their normal (rest) orbits in one or more steps they give up their excess energy in the form of fresh photons. When a substance absorbs the energy of photons it will heat up and when the photons are released again the substance will cool. When you hold up your palm to the sun, you can feel the warmth of the billions of photons that strike your hand which will quickly cool in the shade as it gives up more (infrared) photons than it receives.

The light that reaches your eye from a distant star is merely composed of photons of different wavelengths (colors) that have traveled through the near-perfect vacuum of space perhaps for years at the speed of light without interacting with any electrons. In fact, clouds of gas in space could prevent the light from reaching you.

Answer 2

It's a photon that travels through space - you really need quantum mechanics to understand the energy carried although you can get an understanding from the use of Maxwell's equations.

The energy of a photon is carried in the associated electric and magnetic fields. A photon has no mass (otherwise it would not travel at c) so it's just the energy that is transmitted. The two fields interact with an electron and the energy is transferred.

Let me know if you need a deeper explaination.

Answer 3

the energy is in the electric and magnetic fields that comprise the radiation

Answer 4

This wikipedia entry might help you understand.

Answer 5

radiatons are electro magnetic waves. they do not require medium to travel.