Ranku said:I am reading conflicting interpretation of the Hubble constant in the exponentially expanding accelerating universe. Some say the Hubble constant is continuing to decrease; while others say Hubble constant is now unchanging and has become truly a constant.
Which is correct?
sylas said:In a pure exponential expansion, driven only by a cosmological constant, the Hubble constant remains constant.
In an accelerating expansion with some contribution from matter and some from a cosmological constant (such as our universe appears to be) the Hubble constant will continue to decrease, approaching in the limit a certain minimum value, just as the influence of the cosmological constant becomes more an more dominant over the contribution from matter.
You may be reading about these two different cases. Not all accelerating expansion is a pure exponential expansion.
Cheers -- sylas
Exponential expansion refers to the rapid and continuous increase in the size and scale of the universe. This expansion is driven by dark energy and is believed to have started during the Big Bang.
The Hubble constant is a measure of the rate at which the universe is currently expanding. Exponential expansion and the Hubble constant are closely related as the Hubble constant is used to calculate the expansion rate of the universe over time.
The Hubble constant is a crucial parameter in understanding the evolution and fate of the universe. It helps us determine the age and size of the universe and provides insights into the nature of dark energy.
The Hubble constant is measured through various techniques, including the observation of distant supernovae, the cosmic microwave background radiation, and the study of gravitational lensing. These measurements are then used to calculate the rate of expansion of the universe.
The Hubble constant is a key component in modern cosmology and helps us understand the fundamental properties and behavior of the universe. It allows us to study the past, present, and future of the universe and provides evidence for the existence of dark energy and the possibility of a multiverse.