Faster than Light... Superluminal Group Velocity

In summary, the conversation discusses the possibility of superluminal group velocities exceeding the speed of light and how this would be evaluated in mainstream physics. It is mentioned that previous experiments have been done in anomalous mediums, but that no part of the wave actually moves faster than the speed of light. The discussion also brings up a ten-year-old thread on the topic and concludes that the concept of faster-than-light travel is a myth. The thread is then closed.
  • #1
ThunderLight
27
2
If general relativity in the formal sense constrains all velocities to the speed of light as a maximum, how would superluminal group velocities exceeding speeds of light (at their superpositions) be evaluated in mainstream physics? Would this be a case of General Relativity and Physics principles Violation?

An example is a paper reporting superluminal group velocities measured:
http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.88.073901
 
Science news on Phys.org
  • #2
This is an awfully old news. This, and the NEC experiment from way back (https://www.physicsforums.com/threa...n-the-speed-of-light.98696/page-2#post-819155) that has been discussed extensively on PF, are NOT breaking SR and GR. These are done in anomalous medium, and ... pay attention to this... no part of the wave moves faster than c!. This is why it is crucial to understand how we detect a wave, i.e. what part of the wave would have to reach us before we say we detect it.

Zz.
 
  • #3
The question has been answered and there is no need to repeat a ten year old thread, which could as well be read instead.
FLT is a myth: debunked.

This thread is closed.
 

1. What is faster than light, superluminal group velocity?

Faster than light, superluminal group velocity refers to the phenomenon in which the group velocity of a wave exceeds the speed of light in a vacuum. This is different from individual particles traveling faster than light, which is prohibited by Einstein's theory of relativity. Superluminal group velocity is still a topic of debate and ongoing research in the scientific community.

2. How is superluminal group velocity possible?

Superluminal group velocity is possible due to the unique properties of quantum mechanics. In some cases, the wave packets of particles can overlap and interfere with each other in such a way that the group velocity appears to exceed the speed of light. However, this does not violate the laws of physics as the individual particles are still moving at or below the speed of light.

3. What are some real-world examples of superluminal group velocity?

One example of superluminal group velocity is the phenomenon of quantum tunneling, where a particle can seemingly pass through a potential barrier that it does not have enough energy to overcome. Another example is the faster-than-light propagation of light pulses in certain materials, such as in the case of anomalous dispersion. However, these examples do not involve individual particles exceeding the speed of light.

4. How does superluminal group velocity affect our understanding of the universe?

Superluminal group velocity challenges our current understanding of the laws of physics and the limits of what is possible in the universe. It also raises questions about the nature of space and time and the role of quantum mechanics in explaining fundamental physical phenomena.

5. Is superluminal group velocity a reality or just a theoretical concept?

Superluminal group velocity has been observed and studied in various experiments, but it is still a topic of debate and ongoing research. While it is a phenomenon that occurs in certain circumstances, it is not yet fully understood and remains a theoretical concept in other cases. Scientists continue to study and explore the implications of superluminal group velocity in order to gain a better understanding of the universe.

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