I wanted to know how radiation moves in vacuum of space and why it doesn't need any medium ? ( Like sunlight reaching a planet )

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    $\begingroup$ I'm not sure this question has an answer. Science has observed that electromagnetic radiation (including visible light) can travel through a vacuum, and we can use this observation to make predictions. In cases like this one, science doesn't really ask "why", since it would be like asking why do electrons and light display the wave-particle duality, why is matter made up of atoms, why is the nucleus of an atom made up of protons and neutrons, etc. $\endgroup$
    – user21
    May 19, 2020 at 15:43
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    $\begingroup$ See the following question on the Physics Stack Exchange: physics.stackexchange.com/q/19670 $\endgroup$
    – user24157
    May 19, 2020 at 16:31
  • $\begingroup$ Why should it? Photons only travel in a vacuum. They alternate between photons and something else when traveling through a physical medium. $\endgroup$ May 20, 2020 at 14:13
  • $\begingroup$ Your question will be likely closed here, but you've got your answer already. Next time try physics.stackexchange.com with pure physics problems. $\endgroup$
    – peterh
    May 21, 2020 at 1:21
  • $\begingroup$ I'm surprised people seem to be voting to close this based on it being Earth science. This is not a question about Earth science. It may not be on-topic here though. $\endgroup$
    – user24157
    May 21, 2020 at 9:33

2 Answers 2


Electric and magnetic fields can and do exist in a vacuum. Electromagnetic waves are just fluctuations in electric and magnetic fields. In a vacuum (meaning no charges or currents, which do require the presence of matter), then the solutions to Maxwell's equations are electromagnetic waves.


It's an interesting question which can get you quickly into deep physics.

The simple way to view it is the light being made up of photons, which can be viewed and act as particles. Then, when the photon interacts with another particle, phenomena occurs which make them look like oscillating - so from the wave domain - like interference for example. But this doesn't mean that before this interaction, while traveling through the empty space, there had to be some medium oscillating. Conversely, protons, electrons and others which we regularly look at as just particles also show wave behavior when interacting, which makes us a bit more comfortable about consistency in the building blocks of the universe.

The more complicated way to view it is to go further and find out how the photon or light wave "works" in more detail. There is one given answer that they are oscillations in the electric and magnetic fields. But then there's the question of what are the electric and magnetic fields and how do they go from point A to point B through nothing at all? And it quickly gets into quantum field theory and even the nature of spacetime.

I would say that it's safe to pack these quantum field mechanisms into the abstract notion of photon as particle, at least for a person which is not a theoretical physicist. Then theoretical physicists go into the quantum field bits, but these are themselves an abstraction over something else, it goes on and on.


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