There is no such thing. The "speed" depends on how far apart the points are.sjordannc said:the speed at which points in space were moving apart from one another
The problem with this is that Hubble's law says that the recession speed is proportional to distance. So we can tell you the Hubble parameter back then, or we can tell you the recession speed of points a specific distance apart, but there is no single recession velocity. Not then and not now.sjordannc said:I'm looking for the speed at which points in space were moving apart from one another
The Cosmic Microwave Background (CMB) is the residual thermal radiation from the Big Bang, which occurred approximately 13.8 billion years ago. It is a faint glow of light that fills the universe and can be observed in every direction, providing a snapshot of the universe when it was just 380,000 years old.
At the time the CMB was emitted, the universe was expanding rapidly, but not at a constant speed. The expansion rate is characterized by the Hubble parameter, which was much higher at that time compared to its current value. The exact rate is difficult to pinpoint, but it is estimated to be around 100,000 km/s/Mpc.
The current expansion rate of the universe, known as the Hubble constant, is approximately 70 km/s/Mpc. This is significantly slower than the expansion rate at the time of the CMB, which was around 100,000 km/s/Mpc. This difference reflects the deceleration and subsequent acceleration phases the universe has undergone.
The high expansion speed at the time of the CMB is due to the conditions of the early universe, which was much hotter and denser than it is today. The immense energy from the Big Bang caused a rapid expansion, which has been slowing down over time due to gravitational forces, until the more recent acceleration driven by dark energy.
Scientists measure the expansion speed of the universe at the time of the CMB by studying the detailed properties of the CMB radiation, such as its temperature fluctuations and polarization patterns. These observations are compared with theoretical models of the universe's evolution, allowing scientists to estimate the Hubble parameter at different epochs in cosmic history.