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:
This question addresses the observed imbalance between matter and antimatter in the universe. According to the Big Bang theory, the universe should have created equal amounts of matter and antimatter. However, we observe a predominance of matter. The reason for this asymmetry is believed to be due to CP violation, which refers to a discrepancy in the laws of physics that govern matter and antimatter. This slight violation might have led to the excess of matter over antimatter after the Big Bang.
The laws of physics do not show a preference for specific particles, but rather, they dictate how particles behave and interact under different conditions. However, the universe does exhibit a more observable presence of certain particles, like protons, neutrons, and electrons, which make up ordinary matter. This is not due to a preferential treatment by the laws of the universe but rather the result of the conditions and processes that occurred in the early universe.
The four fundamental forces – gravity, electromagnetism, the weak nuclear force, and the strong nuclear force – play crucial roles in the formation and stability of matter. For example, the electromagnetic force governs the interactions between charged particles, while the strong force is responsible for holding the nuclei of atoms together. Without these forces, matter as we know it would not exist, indicating that the properties and interactions of matter are deeply influenced by these fundamental forces.
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 on visible matter, radiation, and the large-scale structure of the universe. It is significant because it comprises about 27% of the universe's mass-energy content, influencing the formation and structure of galaxies. Understanding dark matter is crucial for our comprehension of the universe's composition and evolution.
Current scientific evidence supports the idea that the laws of physics are universal and consistent across the entire universe. This uniformity is a fundamental assumption underlying many cosmological theories and models. Observations across vast distances and different conditions have so far reinforced this assumption, with no significant deviations detected in how the laws of physics apply in various parts of the cosmos.