i’m continually impressed and enlightened by the Quality of Questions and Answers that i come across on “askscience”
Hydrogen is converted to helium (and then to heavier elements) by the process of nuclear fusion, not spontaneous decay. A helium atom is dramatically more massive than a hydrogen atom (about four times as massive, since it has 2 protons & 2 neutrons instead of just 1 proton), so hydrogen can’t just decay into helium. Helium-4 is also a very stable nucleus which does not decay. Two of the main kinds of radioactive decay are known as alpha decay and beta decay. Alpha decay is when an atomic nucleus ejects a Helium-4 nucleus. An example is Uranium-235 into Thorium-231. Beta decay is when a neutron in the nucleus decays into a proton and an electron, ejecting the electron. In general, decay is a process which tends to create lighter nuclei, rather than heavier ones.
When the universe was a few minutes old, it was hot and dense enough that the hydrogen could be fused into helium, but the universe was rapidly becoming less dense due to expansion and there wasn’t enough time for the helium to fuse into anything heavier, except for an extremely scant amount of lithium and maybe some beryllium. After that, it was a boring few hundred million years until the first stars were born. Stars derive their energy from converting hydrogen to helium, and helium into heavier elements, up through iron. Past the iron-nickel peak in thenuclear binding energy curve , you can’t extract energy from fusion. However, some such elements are nevertheless formed during the lifetime of stars, due to the slow neutron capture process . In supernovae, elements are quickly converted to heavier and heavier elements through the r-process .
Entropy isn’t necessarily going to turn the universe into a homogeneous blur. Entropy isn’t a force or anything, it’s purely a statistical mechanics quantity. The Second Law of Thermodynamics comes entirely from a mathematical argument that it is more likely for a system to land in a higher-entropy state than in a lower-energy state. To determine what actual processes are going on in the universe, you need to use general relativity & quantum mechanics to understand the processes that drive the evolution of the universe. It’s thought that black holes will eventually decay (on staggeringly long timescales) due to Hawking radiation , though this hasn’t been experimentally verified. To really understand the future entropy state of the universe, we’d need to have an actual understanding of dark energy and how to characterize its entropy. But in general it’s necessary that the final entropy state of the universe will be higher than the entropy of the early universe.
What exactly is a quantum dot?
A significant improvement on existing LCD or LED methods, the technology works by shining blue light through nanocrystals of varying size from two to ten nanometres, which absorb light of one wavelength and emit light of another, very specific wavelength. Each dot emits a different colour depending on its size. A film of quantum dots of a size suitable to produce red and green light is added in front of the screen’s backlight. Generating light via the quantum dots narrows the wavelength of the red and green light produced, meaning less light is caught by the LCD filter. This means better colour rendition and brighter colours.
So the use of quantum dots extends the capability of ultra high-definition displays, allowing the delivery of higher dynamic range media to the public in the future. As a bonus, quantum dots are significantly cheaper than other competing high-quality display technologies, such as OLED, organic light-emitting diodes, which were heralded as the next big thing at previous CES shows, but whose star is already waning.
At the moment quantum dots are being used only combined with other types of backlights, but it’s possible to engineer a method of using them without. In any case, for 2015 and the foreseeable future, the world’s best video and image reproduction for high-definition content will be delivered with quantum dots.