# Does the speed of light and its velocity depend on the frame of reference?

### Asked by abhishek_nayak98 | 20th May, 2014, 11:06: PM

Expert Answer:

### Speed of light is a universal constant. It does not change from one frame to another.
However, when one measures the speed of light from another reference frame it might appear different depending on the speed of the frame itself.
This does not mean that the speed of light has decreased or increased, it only means that the speed of light is measured differently in that frame of reference.
This seems like a paradoxial statement, however the fact is that speed of light does not change.
When an observer approaches the speed of light and if it observes a spacecraft (travelling at the speed of light), then what he will see is that the spacecraft moves slowly and its lenght has been contracted. These are the consequences when he does not measure the speed of light as it is in vacuum or free space.
Also speed of light changes only when there is a change in the medium like water, glass, etc. However in a particular medium in any frame of reference, the speed remains the same.

### Answered by Romal Bhansali | 27th May, 2014, 10:57: AM

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