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Cake day: September 14th, 2023

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  • What does it mean when light hits something? Is light “hitting” the air around you? If so how can you see at all?

    For light to measurably change when it interacts with a particle or group of particles, there has to be a separation of electrical charges. The light also has to be close to the energy of an available energy state transition. There’s lots of diffferent types, but remember electron orbitals? Most visible light interactions involve electrons jumping to higher energy orbitals or falling to lower energy orbitals. There are only very specific interactions that are possible with specific wavelengths of light. Fortunately, visible light spans a wide range of wavelengths that interact very strongly with the forms of matter that surround us.

    There are lots of things that won’t interact with light at all. Nuetrons and neutrinos don’t have a charge separation and don’t interact with light at all. You could shine very strong lasers through a cloud of neutrinos, and as far as the beam path would indicate, it would be identical to vacuum. They have to be studied by how they interact with other matter that does interact with light. It may sound counterintuitive, but single free charges like a bare hydrogen nucleus or free electron also don’t absorb or emit photons. It is only when charges can interact with eachother that we get light interactions.

    So nothing measurable happens when light propagates through a volume where dark matter is. There is no mechanism by which the two can interact, except gravitational lensing.



  • The supply side of power generation is coordinated by a bid system. So the cheapest sources are activated first. As demand goes up increasingly expensive forms of power generation are turned on.

    For daily and seasonal variation, this is fine. The amount of time that really expensive generation is active is only a small portion and the base rate can stay low. However, if you add a bunch of baseload without adding equivalent generation, your utility will be stuck buying at the top end of the capacity market auction. The datacenter will have negotiated a discounted rate though because constant demand is good for the utility in the long run. That leaves everyone else paying a big rate increase.

    Source: none given, but the capacity auction is a real thing, and the predicted behaviour of such a system can be reasoned.






  • Market cap is average sale price times the total number of outstanding shares. So with normal trade volumes the market cap swings can far exceed the value of the trades.

    Say a company has 10,000,000 outstanding shares and trades at an average price of $100, the market cap would be $1 billion. Let’s also arbitrarily assume that stock has been trading at $100 for a very long time and almost everyone has a cost basis of $100/share. Now a bad news story comes out and 10,000 shares are sold at $90 dollars. The transacted value would be $900,000 dollars and the new market cap would be $900 million. That’s a $100million drop in market cap, but only a $100,000 realized loss for shareholders. Market cap is precisely as volatile as share price and is only useful as a shorthand for nominal value, but should not be used as a measure of total value.

    Purchases and Sales are double entry and by definition have to be balanced. 1 billion in sales is always matched to 1 billion in purchases. Unless shares are being created or destroyed.