Understanding the Speed of Light: A Thought Experiment

In summary, the conversation discusses the speed of light and its independence from the frame of reference. The speed of light is an axiom in special relativity and is experimentally verified to have a fixed value, c, in any equivalent frames. This leads to some interesting effects such as time dilation for objects moving at near lightspeed. The conversation also touches on the topic of mathematical knowledge needed to understand these concepts.
  • #1
bil.a
2
0
I'm still really confused about the speed of light. I'm kinda new at this so bear with me. Does the speed of light depend on the frame of reference it is in? For example let's say you have a ball moving at 10m/s in a car moving at 20m/s. This would mean that from the Earth's frame of reference the ball is moving 30m/s.

But what if you had a car moving half the speed of light. And a man in the car fired a light gun traveling at the maximum speed of light. What would the speed of the light from the gun be from the Earth's frame of reference.

Wouldn't it be 1.5 the speed of light? Why or why not is this not possible?
 
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  • #2
Welcome to PF.

bil.a said:
Does the speed of light depend on the frame of reference it is in?

It doesn't. Actually, that is one of the axioms that the whole of special relativity follows from, and it is experimentally verified to great accuracy. That is, in two "equivalent" frames (moving with constant velocity with respect to the other) the speed of light always has some fixed value, c.

Now, when you perform your thought experiment, all kinds of weird stuff follows (like, when you use the light gun in your moving car to construct a clock, it will tick slower to a spectator along the track).
 
  • #3
hmmm so does this mean that the light fired from the gun will move have a slower time interval once it reaches maximum speed observed from the earth?
 
  • #4
bil.a said:
hmmm so does this mean that the light fired from the gun will move have a slower time interval once it reaches maximum speed observed from the earth?
Not usre what you mean by a "slower time interval," but a person traveling at enar lightspeed will age more slowly, yes.
 
  • #5
Also note it doesn't reach its maximum speed. It just always travels at that speed, light is not something that needs to be or even can be "accelerated from rest".

May I ask how your mathematical knowledge is? E.g. what is your level of algebra? Because I have a document that allows you to figure out some of the weirdnesses, starting from basic postulates for yourself. I'm not sure where you are from, but in American terms end-of-high school (~ 16 - 18 years of age) math definitely suffices (as long as you can substitute and simplify fractions, and use a function prescription to sketch a graph and derive basic properties from it.).
 

Related to Understanding the Speed of Light: A Thought Experiment

1. What is a "cool thought experiment"?

A "cool thought experiment" is a hypothetical scenario or problem that is designed to challenge one's thinking and explore different ideas and possibilities. It often involves imagining a scenario that is not possible in reality, but can help us understand complex concepts or theories.

2. Why are thought experiments important in science?

Thought experiments are important in science because they allow scientists to explore new ideas and theories without the constraints of physical limitations. They also help scientists to better understand complex concepts and theories by challenging their thinking and forcing them to consider different possibilities.

3. Can a thought experiment be proven or disproven?

No, a thought experiment cannot be proven or disproven. It is simply a mental exercise and does not involve any physical experimentation or data collection. However, the results of a thought experiment can lead to further scientific research and experimentation.

4. Are thought experiments only used in theoretical sciences?

No, thought experiments are used in many different fields of science, including theoretical and experimental sciences. They can be used to explore and test ideas in fields such as physics, biology, psychology, and more.

5. How can thought experiments benefit society?

Thought experiments can benefit society by helping us to better understand complex concepts and theories, leading to advancements in science and technology. They can also inspire creativity and critical thinking, and can be used to explore ethical and moral dilemmas that may arise from scientific advancements.

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