Once seen as Einstein’s biggest mistake, the cosmological constant (Λ) is now one of the most important aspects in explaining the universe’s accelerating expansion.
To explain how it all started we first need to understand that Albert Einstein believed that we live in a stable universe in which Big Bang practically never existed, so therefore the scientist was put face to face with a problem: if our universe was stable and gravity was the only fenomen that occurred than that means that the whole universe is most probably going to collapse later or sooner. Consequently, Einstein added a new term in his theory to counterbalance the gravity, an element of rejection called “ anti-gravity”. To me the funny thing is the reason he attached this new term to his theory and well… the truth is that the scientist simply wanted to make the equation look correct, in reality he was not aware of any force of this kind.
His decision was soon enough questioned by many scientists. Let’s look at his new theory this way: if a force in contrast to our well known gravity really existed than as well as uncontrolled gravity could make the whole universe collapse than this so called “anti-gravity force” could do as well.
To avoid this catastrophic outcome Einstein made the decision to accept his mistake and to ignore the second term. Basically, the cosmological constant was not forgotten, it was kept in the equations of relativity but its value was simply set to 0.
Things changed in 1990 when two groups of astronomers started to map supernovas from different distant galaxies. Slowly, as more and more distant supernovas were discovered, a pattern stood out: their brightness was decreasing simultaneously with their distance. This pattern started to suggest that the expansion of the universe was not slowing down, as previously thought, but was actually accelerating.
The most unexpected thing was that the results of the supernovas matched Einstein’s equations but only if a negative term was included. So therefore, the cosmological constant received a bigger value: 0,7.
The new obtained results showed that a new force in contrast to the gravity was needed. A mistery to this day is that this force is supposed to be way less powerful, even though there is no motive to why this force could not take a bigger value. Its value is roughly similar to gravity, but it operates in a way that leads to the accelerated expansion of the universe, rather than the contraction predicted by gravity alone.
And that’s how this new force received the name of “dark energy”.
In conclusion, what Einstein initially saw as a mistake turned out to be something that actually revolutionized all the knowledge that scientists owned at that time about our beautiful universe.
Bibliography
Book: “50 ideas you really need to know-physics”-written by Joanne Baker \
Comments