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Question

Explain what we mean when we say that Hubble’s constant is between 20 and 24 kilometers per second per million light-years.

Answer 1

Simple answer: for every million light years between two objects, the distance between them increases by 20 to 24 kilometers per second.

Answer 2

Not sure where you got your figures, but the Hubble Constant is more like 0.7 kilometers/second. What the Hubble Constant using 0.7 kilometers/second means is that for every 0.7 km/sec increase in speed two galaxies are separating from each other the distance between them increases by 3,261,688 light years.

For example galaxy 'A' is receding from galaxy 'B' at 5.3 km/sec. That means that they're currently 250-million light years apart.

Answer 3

I'd say it means that for every million light years that the Hubble is away from the earth, there will be an "error" rate every 24 km of surveyed area or data transmission. This could mean that the further away is the hubble, the more wider the error rate in receiving will be.. This could be interpreted as a poorer quality image of space, remeber 24km in space terms is not so great, but if the hubble is 1000 light years away from the receiver station on Earth, then the margin of error in received data is 24,000 km.. this could mean the difference in filming the fine detail of a planets surface, to receiving a very poor quality picture.

An anology might be having a picture made of pixels 24km width, which would allow some detail to be interpreted, compared with 24,000 km apart, where entire ecosystems would be interpreted as one homogenous blob, allowing minimal valuable data to be received.

Answer 4

The Hubble constant is a measure of how fast an object is receding in the universe based on it's distance. Right now it's
around 71 km/s/Mpc. That means for every million parsecs of separation between two objects, there is a velocity difference of 71 km/s. Here's a write up --

http://en.wikipedia.org/wiki/Hubble's_law