Oct 12, 2024 05:12 PM
https://theconversation.com/dark-energy-...ime-238247
EXCERPTS: . . . From 1999 to 2004, the cosmological community came together to agree that the universe was 5% normal (baryonic) matter, 25% dark matter (unknown, invisible matter), and 70% “dark energy” (an expansive force) – essentially a cosmological constant, which was first postulated by Einstein. The discovery that the universe was dominated by this constant energy shocked everyone, especially as Einstein had called the cosmological constant his “biggest blunder”.
Today, cosmologists still agree this is the most likely make-up of our universe. But observational cosmologists like me have refined our measurements of these cosmic variables significantly – reducing the errors on these quantities.
The latest numbers from the Dark Energy Survey (DES) indicate that 31.5% of the universe is matter (a combination of dark and normal), with the remainder being dark energy assuming a cosmological constant. The error on this measurement is just 3%.
Knowing these numbers to higher precision will hopefully help cosmologists understand why the universe is like this. Why would we expect to have 70% of the universe today as “dark” (can’t be seen via electromagnetic radiation) and not associated with “matter” like everything else in the universe?
The origin of this dark energy remains the biggest challenge to physics, even after 20 years of intense study.
[...] The next few years will be fun for cosmologists, with new data and results [...] Combining these datasets should prove beyond doubt if dark energy varies with cosmic time.
If it does, it implies there is less dark energy now than in the past. This could be caused by many things but, interestingly, it could signify the end of a present, accelerated phase of the expansion of the universe.
It also implies that dark energy is probably not a cosmological constant thought to be due to the background energy associated with empty space. According to quantum mechanics, empty space isn’t really empty, with particles popping in and out of existence creating something we call “vacuum energy”. Ironically, predictions of this vacuum energy do not agree with our cosmological observations by many orders of magnitude.
So, if we did discover that dark energy varies over time, it might explain why observations are at odds with quantum mechanics, which is an extremely well-tested theory. This would suggest the assumption in the standard model of cosmology, that dark energy is constant, needs a rethink. Such a realisation may help solve other mysteries about the universe – or pose new ones... (MORE - missing details)
EXCERPTS: . . . From 1999 to 2004, the cosmological community came together to agree that the universe was 5% normal (baryonic) matter, 25% dark matter (unknown, invisible matter), and 70% “dark energy” (an expansive force) – essentially a cosmological constant, which was first postulated by Einstein. The discovery that the universe was dominated by this constant energy shocked everyone, especially as Einstein had called the cosmological constant his “biggest blunder”.
Today, cosmologists still agree this is the most likely make-up of our universe. But observational cosmologists like me have refined our measurements of these cosmic variables significantly – reducing the errors on these quantities.
The latest numbers from the Dark Energy Survey (DES) indicate that 31.5% of the universe is matter (a combination of dark and normal), with the remainder being dark energy assuming a cosmological constant. The error on this measurement is just 3%.
Knowing these numbers to higher precision will hopefully help cosmologists understand why the universe is like this. Why would we expect to have 70% of the universe today as “dark” (can’t be seen via electromagnetic radiation) and not associated with “matter” like everything else in the universe?
The origin of this dark energy remains the biggest challenge to physics, even after 20 years of intense study.
[...] The next few years will be fun for cosmologists, with new data and results [...] Combining these datasets should prove beyond doubt if dark energy varies with cosmic time.
If it does, it implies there is less dark energy now than in the past. This could be caused by many things but, interestingly, it could signify the end of a present, accelerated phase of the expansion of the universe.
It also implies that dark energy is probably not a cosmological constant thought to be due to the background energy associated with empty space. According to quantum mechanics, empty space isn’t really empty, with particles popping in and out of existence creating something we call “vacuum energy”. Ironically, predictions of this vacuum energy do not agree with our cosmological observations by many orders of magnitude.
So, if we did discover that dark energy varies over time, it might explain why observations are at odds with quantum mechanics, which is an extremely well-tested theory. This would suggest the assumption in the standard model of cosmology, that dark energy is constant, needs a rethink. Such a realisation may help solve other mysteries about the universe – or pose new ones... (MORE - missing details)