By Guest Space Cadet
Let me attempt to blow your mind: “Now” travels at the speed of light.
When the light turns green, I don't concern myself with the fact that the light actually turned green a nanosecond earlier than I saw it. As far as the distances we're used to, “now” might just as well be universal.
On interstellar distances, you might expect that the lag start mattering. Except it really doesn't. Maybe Sirius isn't there anymore. Maybe it went supernova five years ago, and the shockwave is riding towards us as you read, and it will hit us in another three years. There's no way we'd know. We look up and see the old faithful Sirius sitting right where it's always been. And we can measure its gravitational influence on us and neighboring stars. There is no knowing it's actually gone, and that's because it actually isn't. To someone in the neighborhood of Sirius, the star is no more, but, to us, it still exist. “Existence” travels at the speed of light.
If the sun was spirited away by a species of prankster kardashev 3 aliens, it would keep “being there” for 8 minutes as far as we'd be concerned.
And those 10 billion light years away stars we see through our telescopes, they are there. Because we can see them.
- Julien Boyer
via .ORGWorld News
By Ann O'Maly
Artwork: Gaia is making the definitive map of our Milky Way Galaxy
Europe’s Gaia space telescope has been used to clock the expansion rate of the Universe and - once again - it has produced some head-scratching.
The reason? The speed is faster than what one would expect from measurements of the cosmos shortly after the Big Bang.
Some other telescopes have found this same problem, too.
But Gaia’s contribution is particularly significant because the precision of its observations is unprecedented.
“It certainly ups the ante,” says Adam Riess from the Space Telescope Science Institute (STScI) and the Johns Hopkins University, both in Baltimore, Maryland, US.
The inability to lock down a value for the expansion rate has far-reaching consequences - not least in how we gauge the cosmic timescale.
If the Gaia speedometer is correct, it would mean having to reduce the estimated 13.88-billion-year age of the Universe by perhaps a few hundred million years.
Read more: http://www.bbc.co.uk/news/science-environment-37438458
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