- #1
GuyBarry
- 25
- 1
Hello - I'm posting this here because of a discussion I got into on another forum following the recent death of Stephen Hawking. I should stress that I am by no stretch of the imagination a physicist (though I did do modules on special relativity and quantum mechanics as part of my maths degree 30 years ago, most of which I've forgotten).
I'd like to know this. We're told that the speed of light is a fundamental constant of nature. We're told that the universe is about 13.8 billion years old. We're told that, as a consequence, it is physically impossible to observe any signal further away from us than light can travel in 13.8 billion years (which turns out not to be 13.8 billion light-years as I always thought, but 46.5 billion light-years, because the universe has expanded since the signal was emitted). All of this I accept.
We also have no reliable way of estimating the size of the universe, as I understand it. It may be orders of magnitude larger than the observable universe, or even infinite.
So how do we know that the speed of light is constant throughout the universe? If the observable universe is in reality a tiny - maybe infinitesimal - region within the greater universe, then it's entirely possible that c = 299,792,458 m/s may in reality be a localized value within that region. And because it's impossible to observe any signal from beyond that region, it's impossible to collect any data that would provide evidence otherwise.
This has been puzzling me a great deal, so I'd appreciate any enlightenment on the issue.
I'd like to know this. We're told that the speed of light is a fundamental constant of nature. We're told that the universe is about 13.8 billion years old. We're told that, as a consequence, it is physically impossible to observe any signal further away from us than light can travel in 13.8 billion years (which turns out not to be 13.8 billion light-years as I always thought, but 46.5 billion light-years, because the universe has expanded since the signal was emitted). All of this I accept.
We also have no reliable way of estimating the size of the universe, as I understand it. It may be orders of magnitude larger than the observable universe, or even infinite.
So how do we know that the speed of light is constant throughout the universe? If the observable universe is in reality a tiny - maybe infinitesimal - region within the greater universe, then it's entirely possible that c = 299,792,458 m/s may in reality be a localized value within that region. And because it's impossible to observe any signal from beyond that region, it's impossible to collect any data that would provide evidence otherwise.
This has been puzzling me a great deal, so I'd appreciate any enlightenment on the issue.