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moatasim23
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Are approching speed and relative speed different quantities in all circumstances or only for photon?
Do you mean closing speed? (The rate at which two things approach each other as measured in some third frame.)moatasim23 said:Are approching speed
As you know, Einstein disagreed with that. But nowadays it has become popular to mean with "relative speed" the same as what commonly is meant with "speed" - the speed of an entity relative to a reference system. Those who use such a definition for "relative speed" then must use such expressions as "approaching" or "closing" speed for the speed of one entity relative to another one, as measured with a reference system in which both are moving. That is generic, for all entities and not only for photons.moatasim23 said:Are approching speed and relative speed different quantities in all circumstances or only for photon?
Doc Al said:Do you mean closing speed? (The rate at which two things approach each other as measured in some third frame.)
If that's what you mean then, yes, closing speed and relative speed are different in general, not just for photons.
The relative speed of A according to B (or vice versa) is (v + 2v)/(1+v*2v/c^2) where v<c and the closing speed is 3v.moatasim23 said:If we consider a car A moving with speed v towards another car B traveling with speed 2v towards A.What is the relative speed and what is the closing rate?
Yes, the so-called "closing speed" is the incorrect answer when you simply add the two speeds together without doing the division part of the correct formula. It doesn't represent anything real. It's not the speed of anything, just two numbers added together and given a name so that we can talk about how wrong it is.yuiop said:The relative speed of A according to B (or vice versa) is (v + 2v)/(1+v*2v/c^2) where v<c and the closing speed is 3v.moatasim23 said:If we consider a car A moving with speed v towards another car B traveling with speed 2v towards A.What is the relative speed and what is the closing rate?
It does have one practical application. If the distance between the two objects is d, then the time to collision is d/(closing speed) but as you correctly point out it is not the speed of any single tangible object and is not a violation of SR or an example of superluminal speed.ghwellsjr said:Yes, the so-called "closing speed" is the incorrect answer when you simply add the two speeds together without doing the division part of the correct formula. It doesn't represent anything real. It's not the speed of anything, just two numbers added together ...
Special relativity effectively applies for all these cases (see my earlier reply). The technical term for measurements "when the observer is actually one out of the two" objects that are in relative motion, is that object's "rest frame".m4r35n357 said:If I'm paraphrasing correctly, effectively special relativity only "applies" when the observer is actually one out of the two. Is there a technical term for that?
Approaching speed is the speed at which an object, in this case a photon, is moving towards an observer. It is often used to describe the speed of light in relation to an observer's perspective.
Yes, approaching speed is different for photons compared to other objects because photons travel at the speed of light, which is the fastest speed possible in the universe. This means that no matter how fast an observer is moving, the speed of light will always appear the same to them.
The approaching speed of photons is measured using the speed of light, which is approximately 299,792,458 meters per second. This speed is constant in a vacuum and can be measured using various methods, such as the time it takes for light to travel a certain distance or the frequency of light waves.
No, the approaching speed of photons cannot be faster than the speed of light. According to the theory of relativity, the speed of light is the fastest speed possible in the universe and cannot be exceeded. This means that even if an observer is moving at the speed of light, the approaching speed of photons will still be the same.
The approaching speed of photons does not affect time and space in the same way as other objects. This is because as an object approaches the speed of light, time dilation occurs, meaning time appears to slow down for that object. Additionally, the length of an object also appears to contract in the direction of motion. These effects are a result of the fundamental principles of relativity and are only applicable when an object is approaching the speed of light.