# Doubly Special Relativity: What Is It and Why Does It Matter?

• Zefram
In summary, this theory introduces a new observer-independent scale, namely that of energy. Other accounts say that it is length, mass, or momentum, but these differences are just a consequence of the use of natural units. If the observed energy and momentum are no longer considered to be linear, but would be different in each frames of reference, this would mean that two bodies of different mass, observed to be traveling side by side in one observer's frame would be observed differently on a second frame, that is one body would travel faster than the other...the philosophical consequences of such a theory would be tremendous.
Zefram
What are the basic ideas behind this? What problems does it solve? What's "doubly special" about it? My knowledge of regular special relativity is pretty layman, with some of the easier (algrabraic) math mixed in.

So can anyone explain this easily? Is it cutting edge "wave of the future" stuff?

All I know about it is that a new observer-independent scale is introduced, namely that of energy. Other accounts say it is length, mass, or momentum, but these differences are just a consequence of the use of natural units, I think.

Here is a short article on the subject:
http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v418/n6893/full/418034a_r.html

Here are two articles written by the original theorist, Giovani Amelino-Camelia:
http://xxx.lanl.gov/PS_cache/gr-qc/pdf/0207/0207049.pdf
http://xxx.lanl.gov/PS_cache/gr-qc/pdf/0210/0210063.pdf

David had a really great post on this in PF v2.0, and he wrote an article for Nature magazine, I believe. When he comes back, you should bug him about it.

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Newscientist, actually?
Any specific questions? I'll post a very basic PP article soon on it.

Nothing really specific, FZ, I'm just wondering what it's all about and how it differs from regular special relativity.

Originally posted by Tom
All I know about it is that a new observer-independent scale is introduced, namely that of energy. Other accounts say it is length, mass, or momentum, but these differences are just a consequence of the use of natural units, I think.

This would be a revolutionary theory, it seems. If the observed energy and momentum are no longer considered to be linear, but would
be different in each frames of refference, this would mean that two bodies of different mass, observed to be traveling side by side in one observer's frame would be observed differently on a second frame, that is one body would travel faster than the other...the philosophical consequenses of such a theory would be tremendous; a theory of multy universes would arise from this.

mich

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Here is another 'variation on the theme', what about the relativity of the measuring unit system? If measurements are relative, then why not also the measuring units?

Absurd? Weird?

Suppose we would use metrics/measuring units, in which the expansion of space would be a constant (measuring units 'grows' with the expansion of space). What kind of physics would we then get?

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## 1. What is Doubly Special Relativity?

Doubly Special Relativity (DSR) is a theory that combines the principles of Special Relativity and Quantum Mechanics. It suggests that the speed of light is not the fastest speed in the universe, and that there may be a maximum speed limit for all particles and objects.

## 2. How is DSR different from Special Relativity?

In Special Relativity, the speed of light is considered to be the same for all observers, regardless of their relative motion. However, in DSR, the speed of light is dependent on the energy of the observer, and can vary for different observers.

## 3. What evidence supports DSR?

Currently, there is no direct evidence that supports DSR. However, some of the predictions made by DSR, such as the existence of a maximum speed limit, have been observed in experiments, providing indirect support for the theory.

## 4. Why does DSR matter?

DSR is important because it provides a possible solution to the conflict between Special Relativity and Quantum Mechanics. It also has implications for our understanding of the nature of space and time, and could potentially lead to a better understanding of the universe.

## 5. Is DSR widely accepted by the scientific community?

DSR is a relatively new theory, and its acceptance among the scientific community is still a topic of debate. While some scientists find the theory intriguing and are actively researching it, others remain skeptical and believe that more evidence is needed to fully support it.

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