Light cone 光锥
A light cone is the path that a flash of light, emanating from a single event (localized to a single point in space and a single moment in time) and traveling in all directions, would take through spacetime.
The lightcone is a fancy name for the area contained within the two 45-degree lines that are so important in protecting causality. - from "Why E=MC2 and Why Should We Care?"
See "Minkowski diagram"

Causality
Causality is another seemingly obvious concept whose application will have profound consequences. It is simply the requirement that cause and effect are so important that their order cannot be reversed.

String theory 弦理论
String theory is a developing theory in particle physics that attempts to reconcile quantum mechanics and general relativity. It is a contender for the theory of everything (TOE), a manner of describing the known fundamental forces and matter in a mathematically complete system. The theory has yet to make testable experimental predictions, leading some to claim that it cannot be considered a part of science.
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M-theory
In theoretical physics, M-theory is an extension of string theory in which 11 dimensions are identified.


Dark Energy
In physical cosmology, astronomy and celestial mechanics, dark energy is a 【hypothetical】 form of energy that permeates all of space and tends to increase the rate of expansion of the universe.Dark energy is the most accepted theory to explain recent observations and experiments that the universe appears to be expanding at an accelerating rate. In the standard model of cosmology, dark energy currently accounts for 73% of the total mass-energy of the universe.


Cosmic microwave background radiation (CMB)
In cosmology, cosmic microwave background (CMB) radiation (also CMBR, CBR, MBR, and relic radiation) is thermal radiation filling the universe almost uniformly.
With a traditional optical telescope, the space between stars and galaxies (the background) is completely dark. But a sufficiently sensitive radio telescope shows a faint background glow, almost exactly the same in all directions, that is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the radio spectrum. The CMB's serendipitous discovery in 1964 by American radio astronomers Arno Penzias and Robert Wilson was the culmination of work initiated in the 1940s, and earned them the 1978 Nobel Prize.
Cosmic background radiation is well explained as radiation left over from an early stage in the development of the universe, and its discovery is considered a landmark test of the Big Bang model of the universe. When the universe was young, before the formation of stars and planets, it was smaller, much hotter, and filled with a uniform glow from its white-hot fog of hydrogen plasma. As the universe expanded, both the plasma and the radiation filling it grew cooler. When the universe cooled enough, stable atoms could form. These atoms could no longer absorb the thermal radiation, and the universe became transparent instead of being an opaque fog. The photons that existed at that time have been propagating ever since, though growing fainter and less energetic, since exactly the same photons fill a larger and larger universe. This is the source for the alternate term relic radiation.
Precise measurements of cosmic background radiation are critical to cosmology, since any proposed model of the universe must explain this radiation. The CMBR has a thermal black body spectrum at a temperature of 2.725 K, thus the spectrum peaks in the microwave range frequency of 160.2 GHz, corresponding to a 1.9 mm wavelength. This holds if you measure the intensity per unit frequency, as in Planck's law. If instead you measure it per unit wavelength, using Wien's law, the peak will be at 1.06 mm corresponding to a frequency of 283 GHz.
The glow is highly uniform in all directions, but shows a very specific pattern equal to that expected if a fairly uniformly distributed hot gas is expanded to the current size of the universe. In particular, the spatial power spectrum (how much difference is observed versus how far apart the regions are on the sky) contains small anisotropies, or irregularities, which vary with the size of the region examined. They have been measured in detail, and match what would be expected if small thermal variations, generated by quantum fluctuations of matter in a very tiny space, had expanded to the size of the observable universe we see today. This is still a very active field of study, with scientists seeking both better data (for example, the Planck spacecraft) and better interpretations of the initial conditions of expansion.
Although many different processes might produce the general form of a black body spectrum, no model other than the Big Bang has yet explained the fluctuations. As a result, most cosmologists consider the Big Bang model of the universe to be the best explanation for the CMBR.
你的电视机接收的电波中有1%直接来自宇宙大爆炸。宇宙起源于像火球一样的大爆炸。按照定义，这个火球挤满了宇宙。时至今日，大爆炸仍在我们周围，但由于宇宙137亿年的扩张，大爆炸已经冷却下来，现在其残余形式并非可见光，而是微波，与电视机经常接收到的一样。

Quantum Mechanics 量子力学
electron, anti-electron
matter, anti-matter
Heisenberg uncertainty principle
virtual particle(vacuum fluctuations of vacuum energy)
Vacuum < virtual particles (electrons and anti-electrons appear out of "nothing" and disappear again)
Quantum field theory
The Dirac equation

Relations between Dark Energy an Quantum Mechanics 将微观世界和宏观世界联系起来
Something from Nothing
Could dark energy show a link between the physics of the very small and the physics of the large?
Energy is supposed to have a source — either matter or radiation. The notion here is that space, even when devoid of all matter and radiation, has a residual energy. That "energy of space," when considered on a cosmic scale, leads to a force that increases the expansion of the universe.
Perhaps dark energy results from weird behavior on scales smaller than atoms. The physics of the very small, called quantum mechanics, allows energy and matter to appear out of nothingness, although only for the tiniest instant. The constant brief appearance and disappearance of matter could be giving energy to otherwise empty space.
It could be that dark energy creates a new, fundamental force in the universe, something that only starts to show an effect when the universe reaches a certain size. Scientific theories allow for the possibility of such forces. The force might even be temporary, causing the universe to accelerate for some billions of years before it weakens and essentially disappears.
Or perhaps the answer lies within another long-standing unsolved problem, how to reconcile the physics of the large with the physics of the very small. Einstein's theory of gravity, called general relativity, can explain everything from the movements of planets to the physics of black holes, but it simply doesn't seem to apply on the scale of the particles that make up atoms. To predict how particles will behave, we need the theory of quantum mechanics. Quantum mechanics explains the way particles function, but it simply doesn't apply on any scale larger than an atom. The elusive solution for combining the two theories might yield a natural explanation for dark energy.


Our universe is just the quantum world inflated many, many times.

记得很小的时候看过一部科幻小说，主人公是一位发疯的研究量子力学的科学家，那时完全没看懂里面提到的乱七八糟的的理论，现在终于明白了点他为什么会发疯了
Nothing has really shaped everything. 这个道理确实会让人发轰

Why are we made of matters? Where are all these left-behind anti-matters from the Big Bang?
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The problem with anti-matter
Related Stories Science ups the 'anti' on matter
The problem with anti-matter, put simply, is that it doesn't hang about. As soon as an anti-matter particle comes into contact with a particle of matter, both annihilate in a burst of energy.
How then do we explain the existence of so much matter? Everywhere we look in the universe (and as far back in time as we can go by looking out across the lightyears of deep space), we see only matter.
The earth around us, the stars and galaxies, are all made almost exclusively of matter.
The existence of anti-matter was first suggested by the theoretical physicist Paul Dirac in the 1930s.
Working on a theory to combine quantum mechanics with Einstein's special relativity, he realised his equations predicted a corresponding anti-particle for every particle in existence - identical in every respect, but with an opposite electrical charge. So for every proton there is an anti-proton, and for every electron there is an anti-electron, or positron.
That is fine in theory, but it presents a problem: If our current understanding of the laws of physics tells us that as much matter as anti-matter must have been created in the Big Bang, then where has all the anti-matter gone?
One theory is that there must have been some minute discrepancy in the amount of matter and anti-matter created. When all the annihilations between matter and anti-matter particles had occurred (an event that took less than a second) what was left was all the matter that we see around us.
But is that right? Scientists working on the Alpha project at Cern are trying to find out by isolating and studying particles of anti-hydrogen.
Writing in the journal Nature Physics last November, the team announced that they had succeeded in creating anti-hydrogen particles in a series of overlapping magnetic fields.
At the time they managed to trap 38 anti-atoms for just 172 milliseconds. Now, by leaving their trap running, the same team report (again in Nature Physics) that they have managed to hold on to 19 antihydrogen atoms for 1,000 seconds.
"The question is really very simple," according to the lead author of the report Professor Jeffrey Hangst from Aarhus University.
"Do matter and antimatter obey the same laws of physics? The Big Bang theory says there should have been equal amounts of matter and anti-matter at the beginning of the universe, but nature somehow took a left turn and chose matter, and we don't know why".
The length of time antimatter atoms hang around is important because it gives scientists the opportunity to study them in greater detail.
"A thousand seconds is more than enough time to perform measurements on a confined anti-atom" says co-author professor Joel Fajans from the University of California, Berkeley.
"It's enough time for the anti-atoms to interact with laser beams or microwaves. It's even enough time to go for coffee."
Working between cups of coffee, the team will now try to tease out the minute discrepancies between hydrogen and antihydrogen atoms that could account for the preponderance of matter over anti-matter in the universe.

New clue to anti-matter mystery 12 June 2010
A US-based physics experiment has found a clue as to why the world around us is composed of normal matter and not its shadowy opposite: anti-matter.
Anti-matter is rare today; it can be produced in "atom smashers", in nuclear reactions or by cosmic rays.
But physicists think the Big Bang should have produced equal amounts of matter and its opposite.
New results from the DZero experiment at Fermilab in Illinois provide a clue to what happened to all the anti-matter.
Many of us felt goose bumps when we saw the result”
This is regarded by many researchers as one of the biggest mysteries in cosmology.
The data even offer hints of new physics beyond what can be explained by current theories.
For each basic particle of matter, there exists an anti-particle with the same mass but the opposite electric charge.
For example, the negatively charged electron has a positively charged anti-particle called the positron.
But when a particle and its anti-particle collide, they are "annihilated" in a flash of energy, yielding new particles and anti-particles.
Similar processes occurring at the beginning of the Universe should have left us with equal amounts of matter and anti-matter.
Researchers working on the DZero experiment observed collisions of protons and anti-protons in Fermilab's Tevatron particle accelerator.
They found that these collisions produced pairs of matter particles slightly more often than they yielded anti-matter particles.
The results show a 1% difference in the production of pairs of muon (matter) particles and pairs of anti-muons (anti-matter particles) in these high-energy collisions.
"Many of us felt goose bumps when we saw the result," said Stefan Soldner-Rembold, one of the spokespeople for DZero.
"We knew we were seeing something beyond what we have seen before and beyond what current theories can explain."
Dr Guennadi Borissov, from Lancaster University in the UK, who is co-leader of the project, said: "This beautiful result provides important input to understanding the matter dominance in the Universe.
"The DZero experiment is still collecting data and so, as long as funding for our work continues, we can expect to make even more precise measurements of this effect in the future."
The dominance of matter in the Universe is possible only if there are differences in the behaviour of particles and anti-particles.
Physicists had already seen such differences - known as called "CP violation".
But these known differences are much too small to explain why the Universe appears to prefer matter over anti-matter.
Indeed, these previous observations were fully consistent with the current theory, known as the Standard Model. This is the framework drawn up in the 1970s to explain the interactions of sub-atomic particles.
Researchers say the new findings, submitted for publication in the journal Physical Review D, show much more significant "asymmetry" of matter and anti-matter - beyond what can be explained by the Standard Model.
If the results are confirmed by other experiments, such as the Collider Detector (CDF) at Fermilab, the effect seen by the DZero team could move researchers along in their efforts to understand the dominance of matter in today's Universe.
The data presage results expected from another experiment, called LHCb, which is based at the Large Hadron Collider near Geneva.
LHCb was specifically designed to shed light on this central question in particle physics.
Commenting on the latest findings, Dr Tara Shears, a particle physicist at the University of Liverpool who works on LHCb and CDF, said: "It's not yet at the stage of a discovery or an explanation, but it is a very tantalising hint of what might be."
Dr Shears, who is not a member of the DZero team, added: "It certainly means that LHCb will be eager to look for the same effect, to confirm whether it exists and if it does, to make a more precise measurement."


Unlocking the mysteries of anti-matter 15 June 2011
We're back to the question of the preponderance of matter over anti-matter this morning.
Scientists working on the giant T2K particle detector in Japan believe they have made a breakthrough which could help to explain why the universe is made of matter, not anti-matter, and it's all to do with neutrino oscillations.
Neutrinos are fundamental particles of matter spat out when the nuclei of atoms fuse into heavier elements in stars like our sun.
They're hard to study because they only interact very weakly with other particles, but it turns out that there are three types, or flavours, of neutrino - and that they can spontaneously transform from one flavour into another: a process known as neutrino oscillation.
To date scientists have only seen two types of oscillation, but now researchers working at the massive T2K particle detector beneath Japan believe they have succeeded in observing the third, muon-electron neutrino oscillation.
The experiment has involved directing a beam of neutrinos 185 miles through the earth's crust from the J-PARC accelerator at Tokai on one side of Japan, to the giant Super-KamioKande underground detector on the other - a massive (40 metre by 40 metre) canister filled with 50,000 tons of ultra-pure water surrounded by photosensitive rods and buried in the ground.
The experiment ran from January 2010 to March this year - when operations were interrupted by the Fukushima quake. During that time, however, the researchers observed 121 oscillations including 6 muon-electron neutrino oscillations.
The significance of the discovery is that it opens up the mathematical possibility that neutrinos may have fundamentally different properties from their anti-neutrino counterparts: that they are not just simple mirror-image opposites of each other.
That raises the prospect of explaining the difference between matter and anti-matter, and ultimately solving the question of why the universe around us appears to be made almost exclusively of matter.