In “Beyond the Observable Universe [4K]”, the speaker discusses the limitations of our current view of the universe due to its finite age and the travel time of light. They explain that what we observe to be the edge of our observable universe is not necessarily its actual edge, as most scientists believe that beyond what we can see lies more space. The video goes on to discuss the cosmic microwave background, which marks the boundary of our observable universe and allows us to measure the properties of space. The speaker discusses the cosmological principle, which suggests that beyond the cosmic horizon, we would find more of the same, such as galaxy clusters and voids. The video also delves into the idea of a multiverse or parallel universes, and the possibility of time travel within the observable universe.
- (00:00:00) In this section of the video, the speaker discusses the limitations of our view of the universe due to its finite age and the travel time of light reaching Earth. They explain that what we observe to be the edge of our observable universe is not the actual edge of the universe, and most scientists agree that more space lies hidden beyond what we are able to see. The speaker goes on to describe the cosmic microwave background, which marks the edge of our observable universe and allows us to gauge the properties of the space that may lie beyond. They also discuss the cosmological principle and how it suggests that lying beyond the cosmic horizon, we would find more of the same, including galaxy clusters and voids, branching for more than 100 billion light years.
- (00:05:000) In this section, the speaker discusses the concept of the universe beyond the observable horizon. The majority of what we expect to find beyond the cosmic horizon are Andromeda galaxy and giant elliptical galaxies like Messiah 87. However, the question of what lies beyond is relatively straightforward. The bigger and harder to answer question is how much is out there, but answering that question requires understanding the shape of the universe at large. In reality, many great minds and machines have found it impossible to describe what would happen to space at a universality boundary or how such a boundary would manifest in the first place. The universe is believed to curve at some large extent if it is not infinite, like the surface area of Earth. The curvature of space is tied to the energy density of space, and if we could detect such geometry from within the frame of our observable universe, we could make reasonable estimates about the global shape, size, and eventual fate of the cosmos. According to Einstein, a universe dominated by the gravity of its Cosmic Web would have a positive curvature with an Omega value greater than one, representing a high density of gravity-inducing matter and dark matter.
- (00:10:00) In this section of the video, the speaker discusses the possibility of a period of runaway contraction in the universe triggered by an expansionary force, which would eventually crush the cosmic web and return it to a hot and dense high-energy state reminiscent of its earliest moments. However, thanks to the Hubble telescope, scientists have found that the universe is not on a path to a big crunch anytime soon, as its expansion appears to have accelerated with time. This implies that the universe is not dominated by gravity on the largest of scales and must instead be powered by an anti-gravity-like pressure, which is attributed to the repulsive vacuum energy of space. Scientists refer to this as dark energy, which smooths out and inverts space-time, causing gravity to curve less in a negatively curved universe with a density parameter less than one. The video went on to explain how a universe dominated by gravity cannot speed up its expansion, and this led to the realization that cosmic acceleration implies that the universe is not dominated by gravity on the largest of scales. At a critical density, gravity and dark energy are perfectly balanced, resulting in no significant global curvature and a flat geometry. This theory of a flat universe is supported by evidence of the nearly uniform distribution of matter throughout the observable universe and the cosmic microwave background radiation, which are key markers of the early universe. These discoveries have helped scientists to map and understand the geometry of space, with two main methods for measuring curvature: by summing up the total energy densities in the universe by observing its various large-scale properties or by observing the bending of light from distant objects in the universe.
- (00:15:00) In this section of the video, the speaker discusses the discovery of the cosmic microwave background radiation (CMB), which is believed to be a “screenshot” of the early universe. The CMB is strikingly smooth and appears to be similar from all directions, with only minor localized fluctuations. These fluctuations may be caused by density gradients that arose in the early universe’s plasma, or by another possible explanation. However, by measuring the angular sizes and distances between the hot spots, scientists have been able to use the phenomenon of lensing to determine the universe’s curvature. The Boomerang probe was the first to make detailed maps of the CMB, and later measurements by the Wilkinson microwave and isotropy probe and Planck satellite have reaffirmed that the universe is largely flat and critically dense. However, a slight curvature or positive or negative curvature cannot be confirmed, and the flatness problem remains a mystery about why the universe is so perfectly balanced.
- (00:20:00) In this section of the video, the speaker discusses the possibility that the universe may not be infinite, but rather may have a finite volume with limiting factors on scales larger than 60 degrees. The Planck satellites have confirmed that the level of variability in the CMB’s power spectrum starts to flatten out significantly, indicating a cutoff in wave strength on scales larger than our observable universe. This suggests that an infinite cosmos is statistically improbable, and that the universe’s apparent flatness may have an alternative underlying cause. The speaker mentions the possibility of a multi-connected topology, like a toroidal universe, as a potential explanation for the universe’s flatness and positivity.
- (00:25:00) In this section, the concept of a toroidal shape is explained in the context of our universe. In a toroidal universe, the space would appear no different from a flat sheet, but if the sheet is tilted in one direction, it would cause a pop-out effect like a game of Pac-man. The expectation is that repeating sequences of photons reflected in the background radiation should be identified in CMB data sets, but this has not been observed. If the Taurus is larger than our observable universe or if it is not comparably smaller, it may fit reasonably well with the observed properties of our universe. The flow of time can also factor in to create a hyper Taurus within the toroidal shape, with the apparent expansion of our universe simply space-time following the Taurus’s geometry. The final solution to the flatness problem is that our universe is curved, either positively or negatively, but on a scale too large for us to gauge from within our observable field.
- (00:30:00) In this section of the video, the speaker discusses the size and age of the universe and how it has managed to grow to its current state in only 13.8 billion years. The speaker explains that if the universe is negatively curved, it may be even larger due to its extreme runaway expansion. The speaker also discusses the challenges of fitting the classical description of the Big Bang Theory with the current observations of the universe, such as its lack of defects and its smoothness. To address these challenges, cosmologists have developed the theory of cosmic inflation, which explains the universe’s size, smoothness, and apparent lack of curvature. Cosmic inflation was developed in the late 1970s by MIT physicist Alan Guth as a solution to the magnetic monopole problem, and it is based on the idea that a runaway expansion of the universe was catalyzed by quantum decay. The result of this expansion was a resizing of the universe by a factor of at least 26, enlarging the small primordial cosmos.
- (00:35:00) In this section of the video titled “Beyond the Observable Universe [4K]”, the scales of space are discussed. The universe is estimated to be larger than the relative travel distance of light at the end of cosmic inflation, which was 10^-31 seconds after time zero. This event is believed to have contributed to the creation of the cosmic microwave background radiation, hot plasma, and possibly even genetic fabric of galaxies, stars, and planets. Additionally, it may have released primordial gravitational waves, which can still be felt today. The popular explanation for cosmic inflation is that it was driven by an anti-gravity field exerting negative pressure, which is the same type of field used to describe Dark Energy today. However, more research needs to be conducted to link these fields and understand their natural instinct to accelerate their growth. Dr. Adam Reese, a discoverer of dark energy, suggests that this phenomenon may occur from time to time.