Old space information, relevant conclusions?

AI Thread Summary
The discussion centers on the implications of observing ancient light from space and its relation to the universe's expansion. It questions how we can confirm ongoing expansion if the information we receive is from the distant past, suggesting that a recent halt in expansion would go unnoticed. However, it is noted that as distance decreases, the information becomes more current, allowing for a better understanding of expansion dynamics. The Hubble constant is mentioned as a consistent measure over time, reinforcing the likelihood of continued expansion. Overall, while a sudden halt in expansion is theoretically possible, it is considered highly unlikely based on current evidence.
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If the information we see in space is very old, and the universe "seems" to be expanding, how can we know that it is still expanding?
 
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If it had stopped anytime in the recent past we probably wouldn't know about it. We just have no reason to believe it would suddenly stop doing what it's been doing for 13 billion years. Kind of like gravity. We don't know if gravity is going to turn off tomorrow, but we have absolutely no reason to even consider that it might.
 
Yes, but, the information becomes less ancient as distance decreases. The expansion rate of the universe is deduced as a function of time. The Hubble constant scales smoothly across the history of the universe. That does not prove expansion did not suddenly halt a handful of millions of years ago, but, is viewed as highly unlikely.
 

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