1. What is the value of surplus value? There are problems with every question. This is equivalent to talking about the labor of surplus labor.
2. Can surplus labor create human labor? Exchange value (value) is a form of human labor. (Marx gave a definition of value in "Critique of Political Economy": "Value is the undifferentiated human labor condensed in commodities"). You can say that surplus labor condenses into value and becomes value, but you cannot say that surplus labor creates value. However, it can be said that labor creates value, and workers or specific people create value, but it cannot be said that "labor creates value" or "surplus labor creates value." Labor cannot create value within the scope of the value definition of the labor theory of value. This is equivalent to saying that "labor creates human labor."
And what is surplus value? If it takes a worker one hour to produce a piece of cake for a capitalist, the capitalist only pays for half an hour of labor in exchange for one hour of labor. Then the remaining half hour is the surplus value. For the capitalist here, it is just a matter of converting the surplus value into profit.
3. What is capital? To put it most simply, capital is the part exchanged with workers and wages. Even "constant capital" is the part that capitalists in another industry exchange for wages. "Capital" here represents a social dominance relationship, not "means of production", let alone machines. In reality, according to statistics, land accounts for 65% of the total capital in the United States. The value of land increases with the so-called appreciation of GDP, that is, more money is spent to buy land, which means more labor time is spent in exchange. The remaining 40% are mostly real patents, trademarks, etc., and what really accounts for 3% to less than 3% of the capital value is machinery. And is capital a machine? The remaining value will eventually form capital, and the existing machine inventory is from the last 20 years or so, and all the historical value has been depreciated. If capital is a machine, China's labor force can produce all the machines in the world within a year if it knows the technology, but its value (so-called GDP) cannot exceed that of the United States. Another country is knocked back to the Stone Age. As long as the technical population is still there, it can return to its original material and cultural level in a few decades and produce all the machines in history. But in reality, no developing country can surpass the GDP of developed countries in just a few decades. The value itself and capital represent a social dominance relationship and do not represent specific wealth, production capacity and technology.
I would also like to point out that some of the previous answers are problematic.
Value (exchange value) is labor itself, not the result of labor. Of course, labor has duality. First, labor itself serves as exchange value, which is its first level. The second level is that labor may also produce use value.
But labor is not the only source of "use value" (usefulness), just as "Das Kapital" affirmatively states that "labor is the father of wealth, and land is the mother of wealth." Marx believed that nature and human labor are both the source of "usefulness" (use value), and human labor is just a manifestation of natural force.
But "labor itself is indeed the only source of value (exchange value)." For example: 1 ton of heterogeneous cow dung and 1 pound of beef may have the same value. You cannot say that a person who eats 1 pound of beef every day eats 1 ton of cow dung instead of 1 pound of beef. The "usefulness" of beef here is different from the "usefulness" of cow dung. The two are heterogeneous. It can be seen that "value" (exchange value) is not "usefulness" at all, but labor. The value (exchange value) of 1 ton of cow dung is the same as that of 1 pound of beef because they contain the same things, which is the same "amount of labor", which is expressed as socially necessary labor time in conventional social relations. , that is, the time for wage payment according to the daily, weekly, monthly, etc. determined in the contract.
In Marxist economics and classical economics, value and capital represent a social dominance relationship and do not represent specific wealth, technology, or production capacity. It was Adam who first pointed out that it represented a social dominance relationship. Smith, "like the invisible hand" describes the equilibrium of a social dominance order, which cannot be confused with the Walrasian equilibrium of optimal allocation of resources - the equilibrium of productivity and individual choice. The "invisible hand" describes the same thing as Marx's "law of value" and "average profit rate".
If you think that value represents a kind of specific wealth, this is exactly the commodity (money) fetishism criticized in Capital.