Category: Lemaître

This Is How Distant Galaxies Recede Away From Us At Faster-Than-Light Speeds

“All the galaxies in the Universe beyond a certain distance appear to recede from us at speeds faster than light. Even if we emitted a photon today, at the speed of light, it will never reach any galaxies beyond that specific distance. It means any events that occur today in those galaxies will not ever be observable by us. However, it’s not because the galaxies themselves move faster than light, but rather because the fabric of space itself is expanding.

In the 7 minutes it took you to read this article, the Universe has expanded sufficiently so that another 15,000,000 stars have crossed that critical distance threshold, becoming forever unreachable. They only appear to move faster than light if we insist on a purely special relativistic explanation of redshift, a foolish path to take in an era where general relativity is well-confirmed. But it leads to an even more uncomfortable conclusion: of the 2 trillion galaxies contained within our observable Universe, only 3% of them are presently reachable, even at the speed of light.

If we care to explore the maximum amount of Universe possible, we cannot afford to delay. With each passing moment, another chance for encountering intelligent life forever slips beyond our grasp.”

If you look at a galaxy, chances are you’ll see that it appears to be receding away from us, as its light is redshifted. The more distant you look, the greater the redshift, and hence, the faster the implied recession speed. But this interpretation runs into problems very quickly: by the time you’re looking at galaxies more than 13-to-15 billion light-years away, they start to appear as though they’re receding faster than the speed of light!

Impossible, you say? Sure, if you only consider special relativity. If you insist on general relativity, it all falls into place. Here’s how.

Who Really Discovered The Expanding Universe?

“Recently, what was known for generations as “Hubble’s Law” has now been renamed the Hubble-Lemaître law. But the point shouldn’t be to give credit to individuals who’ve been dead for generations, but rather for everyone to understand how we know the rules that govern the Universe, and what they are. I, for one, would be just as happy to drop all the names from all the physical laws out there, and simply to refer to them as what they are: the redshift-distance relation. It wasn’t the work of just one or two people that led to this breakthrough in discovering the expanding Universe, but of all the scientists I named here and many others as well. At the end of the day, it’s our fundamental knowledge of how the Universe works that matters, and that’s the ultimate legacy of scientific research. Everything else is just a testament to the all-too-human foible of vainly grasping at glory.”

In science, we have a tendency to name theories, laws, equations, or discoveries after the individual who made the greatest contribution towards its development. For generations, we credited Edwin Hubble for discovering the expanding Universe, as his contributions in the 1920s were absolutely tremendous. However, history has not only revealed that Georges

Lemaître

discovered the very law we had named after Hubble two years prior, but that many other people made essential contributions to that realization. The expanding Universe didn’t come about solely because of Hubble’s discoveries, and perhaps we can do better than crediting just a single person.

Here are a slew of advances that led to and supported the expanding Universe, showing that history and science relies on contributions far richer than that of a lone, genius scientist.