This is a blog on the subject of Astronomy and Astrophysics past, present, and future. Here we will discuss, explain, and learn about this beautiful subject.
The First Direct Evidence for an Inflationary Model of the Universe
How can we see into the infancy of the Universe? The truth is, we can’t. The Universe burst into life well before free-traveling light even existed. We will never ‘see’ the young Universe… or will we?
Though we can’t look directly at its birth, there are strong theoretical predictions for how the dynamics of the universe in the first second of its life would affect signals that we can detect. Later signals, such as the Cosmic Microwave Background.
Cosmologists of the BICEP2 collaboration released results earlier today of their observations of the Cosmic Microwave Background. They have found the first direct evidence that the early Universe underwent a period of rapid, exponential expansion; an ‘inflation’. In particular, they have detected the signature of gravitational radiation from the early universe, amplified by inflation, imprinted on the CMB. The particulars can be seen in the diagram above (from sky & telescope) and in the article here:
This is crazy awesome stuff. More on it later.
Our Place in the Universe: A Sense of Scale
Do you think that the sun is far away? Most people would… but consider this:
There are 100 billion stars in our galaxy alone, and there are 100 billion galaxies in the observable universe (and that’s just the area of the universe from which light has had time to reach us from, it could be BIGGER than that).
The distance from one side of our galaxy to the other is 10 billion times the distance from the Earth to the Sun, and the distance from our galaxy to our closest neighboring galaxy is 165 billion times the distance from the Earth to the Sun.
And, finally, the diameter of the observable universe is 1 million billion times the distance from the Earth to the Sun.
We exist on a scale that unfathomably tiny compared to the large-scale universe. Our comprehension of the cosmos is equivalent to beings that exist on protons comprehending the physics of our everyday lives. I feel so lucky to even begin to understand the large-scale universe in which we live. We are tiny. But we are special.
The distance from the Earth to the Sun is 150 million kilometers.
Finding Beauty in Math and Physics
Einstein’s initial proof of time dilation (above) is, in my opinion, one of the most strikingly beautiful insights that has arisen from any branch of human thought. I wouldn’t normally post something so long, but I believe it is worth it for anyone willing to go through this proof and understand it.
Using a simple thought experiment and less than two pages of middle school level mathematics, Einstein proved something incredible: time is not absolute. Time passes differently for everyone. It passes differently in every corner of the Universe. With simple geometry he was able to show that possibly the most fundamental human assumption, the constancy of time, is false.
Time Dilation, as its called, forms the basis for Einstein’s theory of Special Relativity, which he published in his famous 1905 paper ‘On the Electrodynamics of Moving Bodies’. Special Relativity considered the relative nature of time, and led Einstein to consider the relative nature of Gravity, which resulted in his publication of General Relativity 10 years later. General Relativity has completely revolutionized our views of large scale physics and modern theoretical astronomy, and that’s an understatement. It’s importance to our modern day understanding of the Universe is challenged only by that of Quantum Mechanics, and it all started with this simple, 2 page thought experiment. That’s inspiring. That’s important. That’s beautiful. That’s worth understanding.
WHAT IS LIGHT?
One of the great underlying questions that has remained throughout the evolution of physics, the true nature of light is still not completely known to us. I view light as energy in its truest form, manifesting itself when a physical system or interaction, operating under the conservation of energy, requires it to.
We’ve all heard that light behaves as both a particle and a wave. Here is a brief and qualitative discussion of both formulations.
The wave theory of light is derived from classic electrodynamics, and hinges on the work done by physicists such as Michael Faraday and James Clerk Maxwell. The basic theory states that light results from a coupled disturbance of the electromagnetic field. What this means is that, since a changing electric field induces a magnetic field and a changing magnetic field in turn induces an electric field, any single disturbance can result in a chain reaction: an energy-carrying wave that can travel crazy distances and carry energy into or out of systems. This wave, through strong theoretical and experimental proof, was found to be what we perceive as light.
The experimental observation that called for a reworking of the theory of light in the early twentieth century was performed by Albert Michelson and Edward Morley in 1887. Just as sound waves must have a substance to propagate through (the atmosphere on Earth, for example) it was predicted that, in order for light to propagate through the Universe, the Universe must be filled with some mysterious medium, or ether. Using refined interferometry and the movement of the Earth around the sun, Michelson and Morley were able to prove that such an ether does not exist.
How can light exist as a wave if there is nothing to wave through? This, along with observations that showed energy being absorbed and emitted by systems in discrete units, led physicists such as Max Planck and Albert Einstein to suggest that light exists not as a wave, but rather as a particle, with each particle carrying a discrete amount of energy through the Universe.
Remarkably, both of these theories are correct at the same time. The wave theory of light is solidly derived from a sound physical basis and explains a number of phenomena observed throughout the Universe and in the lab. Likewise, the particle theory of light explains phenomena such as the photoelectric effect and fits in nicely with modern physics.
For me, the easiest way to reconcile this contradiction is to look toward the future. We know that something can’t be both a particle and a wave, and yet we’ve found something that is. Both particle and wave formulations are our attempts to understand the dynamics of light, and they are obviously lacking. The true nature of light must transcend both of these formulations. It will be elegant and beautiful, it will be complex and powerful. Physics still has unanswered questions.
from Spacecraft Films
The human brain is a remarkably efficient engine of visual processing. Even short 1-second shots can reveal an incredible amount of information, and recall one of the most extraordinary voyages of exploration in human history. Presented here is the first manned mission to the Moon, July 1969, in 100 one-second increments. Take a minute and a half and enjoy the voyage once again.
It’s now been 40 years since man has set foot on the moon. I’m secretly depressed about it.
First proposed by theoretical physicist and mathematician Freeman Dyson in 1960 (who was inspired by a sci-fi novel), Dyson spheres are hypothetical structures that would be indicative of the existence of a technologically advanced, intelligent, extraterrestrial civilization.
The idea is that, as an intelligent civilization grows, so will its demand for power. Eventually, its energy demands will be too great for its home planet to handle, and as a solution, the civilization in question could essentially encircle its parent star with huge solar panels that would orbit their sun.
Dyson’s original proposition was along the lines of “a loose collection or swarm of objects traveling on independent orbits around the star.” Many of the best models of Dyson spheres are different arrangements of orbiting satellites. One of the most problematic models is an actual solid sphere. This theoretical sphere would have to be made of an incredibly strong material in order to keep it from collapsing and imploding under the star’s gravity. But once you have a material that is strong enough to withstand the star’s gravity, due to the shell theorem (as proven by Newton), the sphere would have no net gravitational interaction with the star and would eventually drift and collide with it.
If Dyson spheres did exist, they would make great targets for SETI, the Search for Extraterrestrial Life. One would only have to look for a gravitational well where a star should be, e.g. where planets are orbiting, but one would only be able to observe infrared light that radiates through the backside of the orbiting solar panels. Voilà, you’ve found a highly advanced, intelligent extraterrestrial civilization! Congratulations.