Copernicus was the first to banish the idea that we are the ‘center’ of the universe by presenting his heliocentric theory. And, over the centuries, science has shown that the idea of the ‘center’ of the universe seems like a human construct and that it does not exist in the cosmos. But what scientists are sure of is that the galaxies are moving away from each other, that is, that the universe is expanding.
And if it’s expanding, where did the galaxies start to drift away? What was the starting point for the gigantic cosmic explosion of the Big Bang, which gave rise to all matter and energy? Thinking about this is, for scientists, somewhat useless, since the universe could be infinite. It is like imagining a balloon inflating, with many points on its surface moving further and further away from each other: There is no single place from which the universe is expanding , but all galaxies are moving away from all the others.
Now, if the galaxies are moving away from each other, how fast do they do so? A study published in the Astrophysical Journal has concluded that the speed of the expansion of the universe can be different depending on how far you look back in time. An idea that could suggest that new physical models are necessary to analyze this complex concept of the cosmos.
What idea do scientists have of the speed at which the universe is expanding? There are two measurements, and both are considered quite accurate. But, when the data is compared, there is a significant ‘gap’ that scientists cannot bridge. Therefore, the conclusions of the new research may provide new clues about how we should make these measurements, or even involve the creation of completely renewed cosmological models, such as a ‘new Physics’.
The Hubble constant
Hubble’s Law is the observation that galaxies more distant from each other are moving away at a faster rate. This means that the galaxies closest to each other are moving away at a relatively slow rate in comparison.
The relationship between the speed and distance of a galaxy is established by the Hubble constant, which is approximately 80 kilometers per second per Mega Parsec (a unit of length in astronomy; 1 megaparsec (Mpc) equals about 3.26 million light years).
This rate of expansion of the universe, with nearby galaxies receding more slowly than distant galaxies , is what one expects for a cosmos that is uniformly expanding with dark energy (an invisible force that causes the expansion of the universe to accelerate) and dark matter. (an unknown and invisible form of matter that is five times more common than normal matter).
But the Hubble constant has been questioned over the decades: its accuracy is still up for debate; and the desire to achieve maximum accuracy in it is what led to the discovery of dark energy, (and later inspired the construction of the Hubble telescope).
The great contradiction that scientists find is that the Hubble constant is not entirely accurate, since, as we said, two measurements are known (both are considered very reliable) on the speed at which the universe is expanding that does not fit together.
- On the one hand, we have very precise measurements of the Cosmic Microwave Background (the Big Bang glow) from the Planck mission, which has measured the Hubble Constant at about 67.4 km / s / Mpc.
- On the other hand, we have measurements of pulsating stars in local galaxies, also extremely precise, which have measured the Hubble constant at 73.4 km / s / Mpc.
So why is this difference in predictions, if they both appear to be extremely accurate? The current cosmological model may, in fact, be wrong.
Still, no one has come up with another convincing model that can explain this and, at the same time, fit in with all other observations in the cosmos. Is it then a new Physics, which we still do not know?
Another simpler explanation is that perhaps there are unknown unknowns in the data that could have been overlooked.
However, if the current cosmological model is wrong and it is true that a new physics is required to explain these new measurements, the result would be a spectacular change in the image we currently have of the cosmos.
