### Relativity and the Quantum / Elementary Tour part 4: Loop quantum gravity

From the point of view of Einstein´s theory, it comes as no surprise that all attempts to treat gravity simply like one more quantum force (on par with electromagnetism and the nuclear forces) have failed. According to Einstein, gravity is not a force – it ...

### Relativity and the Quantum / Elementary Tour part 3: The need for quantum gravity

So far in the pages of Elementary Einstein, we have encountered two examples in which the limits of general relativity were reached. Both cases involved space-time-singularities. The first example lurked in the interior of a black hole. As briefly described ...

### Cosmology / Elementary Tour: Conclusion

In the context of Einstein's general theory of relativity, one can formulate cosmological models, called big bang models. They give a reliable picture for the past 14 billion years of the evolution of our universe, which can be tested by comparing predictions ...

### Cosmology / Elementary Tour part 5: Dark matter and dark energy

While the predictive power of the big bang models is impressive, they also show us what we don't know about the universe. Not only about the distant past, as detailed on the previous page, but also about the present universe: If you look around, all material ...

### Cosmology / Elementary Tour part 3: The early universe

An expanding universe, with the distances between galaxy increasing all the time, must have been much more dense, and the galaxies much closer together, in the past. The details follow from Einstein's equations which connect the way expansions runs its course ...

### Black Holes & Co. / Elementary tour: Conclusion

In the physics of neutron stars and black holes, we clearly see the central role of general relativity in modern astrophysics. Relativistic physics is necessary to fully understand the most energetic phenomena in the universe - from supernova explosions of ...

### Gravitational waves / Elementary Tour: Conclusion

Gravitational waves promise a glimpse into regions of our cosmos that are inaccessible to regular astronomical observation. In the past, whenever astronomers have opened a new window to the universe (for example, at the beginning of radio astronomy or X-ray ...

### General relativity / Elementary Tour: Conclusion

The aim of this chapter was to give the reader a basic idea of what general relativity is all about. Einstein's theory of gravity led physicists to a variety of new models and phenomena. The most important examples - gravitational waves, black holes, the ...