How Modern Science Determines the Existence of Dark Matter and Dark Energy

So, we are on the verge of profound discoveries. It won't be long before we know enough about these mysterious dark substances to devise a method of recognition. That is, if it hasn't happened already.

Our understanding is shaped not just by what we see and measure, but also by what we do not see and measure. This is perhaps the most puzzling aspect for us. In a universe wrapped in darkness, we should be thankful for the light that we do observe. However, this darkness is where the truth lies.

Imagine a scenario where you see a large ball on one pan of a scale, and nothing on the other side. Surprisingly, the scale remains in perfect balance. How do you explain this? Is the scale stuck? No, it's not. Is the internal mechanism broken? No, everything seems fine. Could the ball have an insignificant weight? No, it's surprisingly heavy.

By discarding these common hypotheses one by one, we are led to a conclusion: an undetectable and physical something is balancing the scale. This is how modern science approaches the understanding of dark matter and dark energy. Moving forward, attributing properties to this unobservable something aligns with the observations, validating its existence.

Now, let's delve into the scientific proofs and evidence that have led us to recognize and acknowledge the presence of dark matter and dark energy.

Direct Evidence Through Gravitational Effects

Scientists directly observe dark matter and dark energy through their gravitational effect. The electromagnetic effects remain undetectable. Despite this, the direct observation of their effects, combined with extensive evidence, suggests that dark matter and dark energy play a vital role in the universe's dynamics.

In 1922, Einstein derived the Friedmann acceleration equation using his general theory of relativity, which described the universe's expansion. This equation includes a term for dark energy (Λ), representing a repulsive force counteracting gravity. The model also includes ρ, the total matter density, which includes both regular and dark matter, and a p term for pressure, which is not significant for the current universe.

The Lambda Cold Dark Model (ΛCDM) explains the expansion of the universe and the details of the acoustic power spectrum of temperature fluctuations in the Cosmic Microwave Background (CMB) radiation measured by the Planck spacecraft. This model played a key role in the 2011 Nobel Prize awarded to Riess, Perlmutter, and Schmitt for their discovery that the universe's expansion is accelerating due to dark energy.

Visualizing Dark Energy and Dark Matter

Consider the graph illustrating the data from galaxy clusters, supernovae, and the CMB. The graph plots dark energy on the vertical axis and total matter on the horizontal axis. The results show that dark energy constitutes 70% of the total energy in the universe, while matter accounts for the remaining 30%. Additionally, the universe is flat, implying that space does not bend or curve at large scales.

The Role of Dark Matter: A Mystery with Answers

No one knows precisely what dark matter consists of, but it formed early in the universe's history. It does not interact with light but interacts with normal visible matter and itself through gravity. Dark matter plays a critical role in galaxy formation and growth, as it was first identified by Vera Rubin, who found that galaxies rotated much faster than expected given the visible matter alone.

The plot from Wikipedia showing the speed of rotation of M 33 (based only on visible matter and actual rotation speed) vividly demonstrates the presence of dark matter. Ultimately, based on the data, dark matter constitutes over 80% of the total matter, contributing 25% to the 30% of energy in the universe related to matter. In addition, dark matter makes the universe flat.

Current Research to Directly Detect Dark Matter

Currently, there are ongoing experiments aimed at directly detecting dark matter beyond its gravitational effects. While the general theory supports the existence of dark matter and dark energy, none of these experiments have achieved success thus far. As such, the truth about these mysterious substances remains hidden, leading to continued research and theories.

The intriguing story of the ΛCDM model, along with its history, is illustrated in an amusing article from Case Western University, which explains the intricate processes involved in formulating the model. Furthermore, additional details can be found in a related Quora question answered by Viktor Toth.

This journey of understanding dark matter and dark energy is a testament to human curiosity and scientific progress. Though the answers are not yet fully uncovered, the pursuit of knowledge continues, and we eagerly await the next breakthrough.

In conclusion, while we may not have all the answers yet, the evidence strongly supports the existence of dark matter and dark energy. These mysterious substances are integral to our understanding of the universe's dynamics and continue to shape scientific investigations and theories.

References

Case Western University: [Link] Quora: [Link]