Photons and Relativity: A Question of Speed and Time

In summary, according to the answer you provided, the faster runner will reach the light source first.
  • #1
admd1
3
0
Hello, I'm sorry to ask a question that has probably been asked many times before, but I currently have limited time, and am very anxious to find an answer. Anyways, here goes:


Hypothetically: If two people start running from point A, one running at 10000 km/s, and the other running at .99c. Two seconds after they begin, a light source is shined in their direction. (Lets say that the area on which they were running was all perfectly flatland and stretched on for billions of miles.) Will the photons emitted from the light source reach them both at the same time? Or will they reach the slower runner first?



I know that this is a pretty simple question, and I'm pretty sure that I know the answer, but I heard someone talking about this, and what they were saying was opposite to what I'd believed.

Any help is greatly appreciated.
 
Physics news on Phys.org
  • #2
admd1 said:
Hello, I'm sorry to ask a question that has probably been asked many times before, but I currently have limited time, and am very anxious to find an answer. Anyways, here goes:


Hypothetically: If two people start running from point A, one running at 10000 km/s, and the other running at .99c.
The speeds are relative to A, presumably?
admd1 said:
Two seconds after they begin, a light source is shined in their direction. (Lets say that the area on which they were running was all perfectly flatland and stretched on for billions of miles.) Will the photons emitted from the light source reach them both at the same time? Or will they reach the slower runner first?
When you say a light source is shined in their direction, do you mean it's shined from the position of A, two seconds after they left A as measured by a clock at rest with respect to A? If so, the light will reach the runner whose speed is lower relative to A first.
 
  • #3
That's exactly what I meant. Thanks for the confirmation.
 
  • #4
admd, you can only learn so much from someone who agrees with you. Go find the person whom you antisocially overheard saying the opposite, ask them to explain why, tell them the explanation for your version in return, and you should both have a higher understanding by the time you reach agreement.

By the way, by "hypothetically" I presume you mean "according to my homework problem"?
 
Last edited:
  • #5
By Hypothetically, I meant "suppose that." That as of now, no one can run anywhere near 10000km/h, let alone .9c. I'm in the midst of reading Brian Greene's The Elegant Universe, and what my philosophy teacher mentioned in class when trying to explain self-evident truths differed from what I thought I knew was true.


Should your response lead me to presume that you think it's possible for one to run at these speeds? =)
Also, it's a matter of opinion, but I don't think that paying attention in class should be labeled as "antisocial."


You're right though, I probably should bring it up with him to double check.
 
Last edited:

What is special relativity?

Special relativity is a theory developed by Albert Einstein in 1905 that explains the relationship between space and time, and how they are affected by the speed of an observer. It also introduces the concept of the speed of light being the same for all observers, regardless of their relative motion.

How does special relativity explain the behavior of light?

Special relativity states that the speed of light is the same for all observers, regardless of their relative motion. This means that no matter how fast an observer is moving, they will always measure the speed of light to be approximately 299,792,458 meters per second.

How is time affected by special relativity?

Special relativity introduces the concept of time dilation, which states that time is relative and can appear to pass at different rates for different observers. This is due to the fact that time is affected by the speed of an observer and their relative motion to other objects.

What is the significance of the equation E=mc² in special relativity?

This famous equation, developed by Einstein, describes the relationship between energy (E), mass (m), and the speed of light (c). It shows that mass and energy are interchangeable and are both forms of the same fundamental entity.

Can special relativity be applied to everyday life?

Yes, special relativity has been proven to be accurate and is used in various technologies, such as GPS systems, particle accelerators, and nuclear power plants. It also helps us understand the behavior of objects at high speeds and in extreme conditions, such as in outer space.

Similar threads

  • Special and General Relativity
Replies
3
Views
449
  • Special and General Relativity
Replies
29
Views
1K
  • Special and General Relativity
Replies
11
Views
942
  • Special and General Relativity
Replies
33
Views
2K
  • Special and General Relativity
Replies
15
Views
1K
  • Special and General Relativity
Replies
20
Views
747
Replies
32
Views
852
  • Special and General Relativity
Replies
12
Views
1K
  • Special and General Relativity
2
Replies
41
Views
3K
  • Special and General Relativity
Replies
21
Views
522
Back
Top