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Olivia Grace
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Do we know what the critical density of the universe is? I always thought we did know, but apparently (according to friend) we don't...
Olivia Grace said:Do we know what the critical density of the universe is? I always thought we did know, but apparently (according to friend) we don't...
Olivia Grace said:Thanks very much, that's really helpful!
One thing,
"the usual figure for the Hubble parameter, at present, is 71 km/second per Mpc which is a bit messy "
How did you boil this down to the 1/13.8 billion years? I'm having trouble converting the units to SI ones...
Your help is muchly appreciated!
marcus said:the inverted Hubble parameter is One Mpc/ (71 km/s)
so that is 3.0857 x 10^18 km/(71 km/s) and kilometers cancel so it's ( (3.0857 x 10^19 )/71) seconds
Critical density refers to the amount of matter and energy in the universe that is needed to determine its ultimate fate. It is the threshold between an expanding universe that will continue to expand forever and a contracting universe that will eventually collapse.
Critical density is calculated by taking the average density of matter and energy in the universe and comparing it to a value known as the critical density value. This value is determined by the Hubble constant and the gravitational constant.
The current estimate for critical density is around 9.9 x 10^-27 kg/m^3. This is equivalent to about 6 protons per cubic meter. However, this value is constantly being refined and updated as new data and observations are made.
Critical density is important in cosmology because it helps us understand the overall structure and fate of the universe. It can also provide insights into the nature of dark matter and dark energy, which make up a large portion of the universe's density.
No, the exact value of critical density is still unknown. It is a constantly evolving concept that is based on current theories and observations. As our understanding of the universe improves, the estimate for critical density may change.