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# Relativity/Cosmologic constant

Question
Einstein in his general relativity introduced a cosmological constant (of which I regretted saying he had made ​​a mistake).
I read that a guideline value of this cosmologic constant is 2x10^(-35)s^(-2) or 2x10^(-52)m^(-2).

Question : I thought that a repulsive force was expressed in erg or newton or similar, but i do not understead why is expressed in second or meter

The cosmological constant can be expressed in many different ways, each with its own units and even as a dimensionless ratio.  The basic idea is a level of energy density, but different authors use different ways of expressing it, including as a ratio of energy densities, would be dimensionless.

Rather than going into these complexities, which are not important except to authors using their own particular taste in writing, I suggest that you ignore the specific values and units and concentrate on the broad idea of the density of energy in space affecting the behavior of the universe.

Do not think of the effect on the universe as a force.  Think of the energy density as a variable that influences the force.  For example, in Newtonian gravity theory, you can deduce the gravitational force on the surface of a planet from it a mass and its radius. Likewise in Einstein's general relativity you can deduce the bending of light passing near a star from the star's mass and radius. You do not need to use the concept of force to predict the path of a light beam.

This is a deep subject, not particularly reducible to elementary ideas of physics, such as force. To get to the bottom of it requires years of study.

Relativity

Volunteer

#### Uncle Ben

##### Expertise

I can answer questions regarding Einstein's Theory of Relativity, particularly in Special Relativity. I will not answer homework questions or mathematical problems that require special symbols.

##### Experience

I have taught physics at the college level, undergraduate and graduate, for many years including Special Relativity. I have taught at Johns Hopkins, Case-Western, and MIT. I have also served as a staff member of the Commission on College Physics, which was supported by the National Science Foundation to recommend improvements in the curriculum of college physics departments in the US. I am also the author of a textbook titled Vector Calculus, which was used at MIT in the teaching of electromagnetic theory and relativity. My research interests were mainly in solid state physics, especially the properties of metals at low temperatures. I am listed in the publication known as American Men of Science.

Publications
I have dozens of papers published in the Physical Review and in the American Journal of Physics.

Education/Credentials
I hold a Ph.D. degree in physics from the Johns Hopkins University.

Past/Present Clients
Johns Hopkins University, Case-Western Reserve University, Massachusetts Institute of Technology, Empire State College, Georgetown University, Commission on College Physics, and UNESCO.