Well never be able to make the jump to lightspeed

We can see objects that have accelerated beyond our current Hubble volume because the light we see today was emitted when they were within it. To understand this, consider that as the Universe gets older, distant light has more time to reach our detectors here on Earth. Now for the next bombshell: The Hubble volume is not the same thing as the observable Universe. It is the space in between us and those galaxies that is rapidly proliferating and stretching exponentially. To an observer within one of those galaxies, nothing violates special relativity at all. But the galaxies themselves aren't breaking any cosmic speed limits.

Yes, galaxies outside of our Hubble sphere are receding from us faster than the speed of light. Spacetime is not expanding with respect to anything outside of itself, so the the speed of light as a limit on its velocity doesn't apply. In this theory, there is no inertial reference frame. General relativity, however, describes the fabric of spacetime itself. A photon always travels away from the observer at 300,000,000 meters per second, and he or she will never catch up.

Whether an observer is sitting still on a park bench on planet Earth or zooming past Neptune in a futuristic high-velocity rocketship, the speed of light is always the same. According to this theory, the speed of light is the same when compared in all inertial reference frames. Special relativity requires what is called an 'inertial reference frame' вЂ“ more simply, a backdrop. The answer has to do with the difference between special relativity and general relativity. This light is stretched, or redshifted, as spaceВ expands in between. Bottom: Detectors catch the lightВ that isВ emitted by a central star. Two sources of redshift: Doppler and cosmological expansion modeled after Koupelis & Kuhn. It was first calculated in 1929, when Edwin Hubble discovered that faraway galaxies appeared to be moving away from us at a rate that was proportional to the redshift of their light. Here on Earth, we define the Hubble volume by measuring something called the Hubble parameter (H0), a value that relates the apparent recession speed of distant objects to their redshift. The physics of that boundary rely, in part, on a chunk of surrounding spacetime called the Hubble volume. Because our cosmos is expanding, the light from some objects is simply too far away for us ever to see. Redshifted light allows us to see objects like galaxies as they existed in the distant past but we cannot see all events that occurred in our Universe during its history. The light from these distant objects has been traveling for so long that, when we finally see it, we are seeing the objects as they were billions of years ago.

This is why cosmologists speak of redshift as a function of distance in both space and time. Once the photons reach us, their wavelengths have been redshifted in accordance with the distance they have traveled. As photons emitted by a star or galaxy propagate across the Universe, the stretching of space causes them to lose energy. We see evidence of this expansion in the light from distant objects. Since that time, our Universe has continued to expand, but at a much slower pace. Seeking the true nadir of vacuum energy, over a minute fraction of a moment, the Universe is thought to have ballooned by a factor of 1050. But around 10-36 seconds after the Big Bang, inflationary cosmologists believe that the cosmos found itself resting instead at a 'false vacuum energy' вЂ“ a low-point that wasn't really a low-point. Like everything else in physics, our Universe strives to exist in the lowest possible energy state possible. But how can this be? If light's velocity marks a cosmic speed limit, how can there possibly be regions of spacetime whose photons are forever out of our reach? And even if there are, how do we know that they exist at all?

Well never be able to make the jump to lightspeed