LightningInAJar said:
LightningInAJar said:
LightningInAJar said:
Yes, you are special.LightningInAJar said:
Where are you getting this from? A reference would help.LightningInAJar said:
Borek said:
What Borek said, above. Look where iron is:LightningInAJar said:
I've always been bothered by diagrams like that one because the binding energy is actually negative; the curve should really be shown inverted, with iron at the bottom, not the top.DaveC426913 said:
You probably don't like the fact that current flow is opposite the electron flow too.PeterDonis said:
Well, Benjamin Franklin said so, right?Vanadium 50 said:You probably don't like the fact that current flow is opposite the electron flow too.
It is unfortunate that you "know" this, since it isn't true. In our solar system alone, life started less than a billion years after the solar system formed. There were galaxies that formed MUCH earlier --- they started forming roughly 12.5 billion years ago and there's no reason to believe that life was not possible as early in the existence of those galaxies as it has proven to be in our solar system. That would put the possibility of life starting at somewhere around 2 billion years into the life of the universe, or in other words, life has been possible for over 80% of the life of the universe.LightningInAJar said:
Wasn't the universe entirely too hot for quite a while after the big bang?phinds said:
Yes, that's WHY it took the 2 billion years I estimated. First the universe had to cool down enough for matter to form from the plasma. This took about 400,000 years and then the first Galaxies had to form (another, very approximate, billion years) and then life could have arisen (another 1 billion).LightningInAJar said:
So you're saying life was possible between about 2 billion years after big bang and the 11.8 billion years after? Are there predictions of when there won't be enough energy left in the universe for life to be possible?phinds said:
Yes, that is exactly what I said.LightningInAJar said:
Not that I'm aware of other than that it will be orders of magnitude beyond the current age of the universe.LightningInAJar said:
As I understand it, the more complex the element, more energy is required to create it. And some elements may only be created in stars of certain size.LightningInAJar said:
Not quite. The point is that elements above iron can be created by fusion, but the process absorbs energy rather than releasing it. So heavier metals do get created in very small quantities in stars, but only in large quantities once the star runs out of lower mass elements and is no longer able to generate energy by fusion, so collapses and then explodes.Aldarion said:
It's not that simple. Any stable atom will have less energy than its constituent particles would if they were isolated and not bound together. So from that point of view, creating, say, a He-4 nucleus from two free protons and two free neutrons, or even from two deuterium nuclei, emits energy. That is why nuclear fusion is an energy source, for example in the Sun. And further fusion reactions can in turn emit more energy as they create larger nuclei, up to iron (Fe-56). After that point, fusion reactions no longer emit energy; they require energy. (Fission reactions, where larger nuclei break up into smaller ones, can, OTOH, emit energy when they start with nuclei heavier than iron. That's why, for example, uranium and plutonium can be used to make reactors and bombs.)Aldarion said:
This is because fusion reactions beyond hydrogen-to-helium require progressively more extreme conditions to happen, which require larger stars in order for their cores to meet those conditions.Aldarion said:
And the reason for this is, as noted above, that iron (Fe-56) is the last point at which fusion reactions emit energy.Aldarion said:
For elements heavier than iron, yes, this is basically correct.Aldarion said:
One of the great mysteries in cosmology is why the Universe appears to be dominated by matter rather than antimatter. According to the laws of physics, the Big Bang should have produced equal amounts of both. However, observations show that matter is far more prevalent. This asymmetry is an active area of research, and phenomena like CP violation (where the laws of physics change slightly when particles are replaced by their antiparticles and left and right are swapped) might offer some clues.
Dark matter is a form of matter that does not emit, absorb, or reflect light, making it invisible and detectable only through its gravitational effects. It constitutes about 27% of the Universe's mass-energy content. While it is not "preferred" in a conventional sense, it is essential for explaining the structure and behavior of galaxies and clusters. Its exact nature remains one of the biggest questions in modern physics.
This question is closely related to the matter-antimatter asymmetry problem. The Universe's preference for matter over antimatter is not well understood, but it is thought to be a result of processes that occurred in the early Universe. These processes might involve slight differences in the behavior of particles and antiparticles, leading to the observed imbalance. This is still an open question in cosmology and particle physics.
The laws of physics as we currently understand them do not explicitly prefer one type of matter over another. However, the interactions and forces described by these laws can lead to the formation of certain structures and types of matter under specific conditions. For example, the strong nuclear force binds quarks together to form protons and neutrons, which are the building blocks of atoms, leading to the matter we observe in the Universe.
Baryonic matter, which makes up the atoms and molecules that form stars, planets, and living organisms, constitutes only about 5% of the Universe's mass-energy content. While it is the type of matter we are most familiar with, it is not necessarily more important than other forms like dark matter and dark energy. Each type of matter plays a crucial role in the structure and evolution of the Universe. Dark matter, for instance, is essential for the formation of galaxies, while dark energy drives the accelerated expansion of the Universe.