How has scientific understanding about the composition of the universe changed over time

Question

The percentage of unknown material has grown In scientists estimates since the 1970s
The percentage of dark matter has shrunk in scientists estimates since the 1980s
The percentage of ordinary matter has grown in scientist estimates
The percentage of dark energy has shrunk in scientist estimates

Answer 1

Scientific understanding of the composition of the universe has evolved significantly over the past several decades, leading to changes in estimates of various components like dark matter, dark energy, and ordinary matter. Here's how each statement aligns with the prevailing scientific consensus:

1. The percentage of unknown material has grown in scientists' estimates since the 1970s: This is somewhat accurate. As measurements of the universe improved, particularly with discoveries related to dark energy and dark matter, the understanding of "unknown" components of the universe expanded. This includes the acknowledgment of large fractions of the universe that could not be accounted for by ordinary matter.

2. The percentage of dark matter has shrunk in scientists' estimates since the 1980s: This statement is generally not true. While the precise estimate of dark matter's contribution has been refined, the proportion of dark matter has remained significant and has not shrunk. For instance, current estimates suggest that dark matter constitutes around 27% of the universe, which aligns with earlier estimates rather than a decrease.

3. The percentage of ordinary matter has grown in scientists' estimates: This statement is also misleading. The percentage of ordinary (baryonic) matter has remained relatively stable in estimates, usually around 5%. Instead, scientists have come to realize that ordinary matter accounts for a smaller fraction of the universe than previously thought, particularly since dark energy and dark matter were introduced into the cosmological model.

4. The percentage of dark energy has shrunk in scientists' estimates: This statement is not accurate. Understanding and evidence for dark energy, which is believed to make up about 68% of the universe, has increased since it was first proposed in the late 1990s following observations of distant supernovae. There have been refinements in how its properties are understood, but its estimated contribution has remained substantial and even strengthened in cosmological models.

In summary, since the 1970s, scientific understanding has evolved to identify a greater fraction of the universe as dark energy and dark matter, while ordinary matter accounts for a relatively stable and minor fraction. The recognition of the universe's complex composition has led to an ongoing re-evaluation of its components rather than a simple increase or decrease in their percentages over time.