High School What Medium Does Light Travel Through in Space?

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Light does not require a medium to travel, contradicting the assumption that it needs one. The distinction between space and vacuum is clarified, with empty space being classified as a vacuum. Interstellar and intergalactic spaces are nearly empty but contain some matter. The lack of evidence for a medium was pivotal in the development of relativity theory. Understanding these concepts is essential for grasping the nature of light and space.
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What is the difference between space and vacuum?
Since light waves require a medium to travel, then what is the medium in space?
 
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rekha1804 said:
Since light waves require a medium to travel,
They don't. Discovering that there's no evidence of a medium was a large part of the work that led to relativity theory.
 
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rekha1804 said:
What is the difference between space and vacuum?
Empty space is a vacuum. Interstellar and intergalactic space are almost empty, but not quite.
 
rekha1804 said:
Since light waves require a medium to travel
This is a faulty assumption and you would do well to get rid of it.
 
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Thread 'Luminous Fast Blue Optical Transients (LFBOTs)'

UC Berkely, December 16, 2025 https://news.berkeley.edu/2025/12/16/whats-powering-these-mysterious-bright-blue-cosmic-flashes-astronomers-find-a-clue/ AT 2024wpp, a luminous fast blue optical transient, or LFBOT, is the bright blue spot at the upper right edge of its host galaxy, which is 1.1 billion light-years from Earth in (or near) a galaxy far, far away. Such objects are very bright (obiously) and very energetic. The article indicates that AT 2024wpp had a peak luminosity of 2-4 x...
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