We tend to view ourselves and the complex cells that build us as a distinct branch of the tree of life from the compact, seemingly featureless cells of bacteria and archaea. But we've found that our genome is actually a hybrid, a mish-mash of genes from bacteria and archaea, along with some that have evolved in our own lineage.

Scientists gradually settled on a simple explanation for this: the first complex cells were the product of a fusion between archaeal cells and bacteria, with the bacteria ultimately evolving into the mitochondria, a chemical-power-generating structure that still retains a bit of its own genome. Over time, many of the other bacterial genes were transferred to the nucleus of what was becoming what we now call a eukaryote, intermingling with the archaeal genes there.

But a new study has taken a careful look at some of the genes shared by all eukaryotes and comes to the conclusion that the reality is a little more complicated and that there were several waves of gene transfers from bacteria. The big picture of a merger between bacteria and archaea is still right, but it was only part of a picture where gene transfers among species were commonplace.

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The scientific community has a plan for achieving fusion power. It involves getting a better understanding of how to control fusion in a tokamak-style reactor using the currently under construction ITER reactor, and then using that knowledge to build DEMO-style plants. But ITER isn't even expected to see hot plasmas until the middle of the 2030s, by which point solar panels will be so cheap that we'll probably all be getting them free in our cereal boxes.

Commonwealth Fusion is a startup that's basically asking "what if we did that, but now?" Its ITER equivalent, a tokamak called SPARC, is over 70 percent complete and is planned to be operating as soon as next year. The company already has a site and customers for the power-generating follow-on, called ARC. Both of those projects are predicated on using high-temperature superconductors to generate an extremely powerful magnetic field that will allow the company to build a smaller reactor, and thus get things done faster.

Years of running plasmas through tokamaks has given us confidence that the basics of these plans are sound. But there are lots of potential devils in the details (otherwise there'd be little need for experimental reactors). So Commonwealth's scientists, in collaboration with the academic community, have recently released five peer-reviewed papers that detail its plans for ARC: what our best models tell us now, and what we'll still need to learn from SPARC to finalize the design of a production fusion plant.

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Just over a year ago, the Trump Administration issued an executive order meant to accelerate the development of nuclear power in the US. While an entire startup ecosystem has developed around the use of different—and typically smaller—reactor designs, only one of them has been fully licensed so far, and there are no plans to actually build any instances of that design.

The executive order directed the Department of Energy to have three different reactor designs reach criticality in a bit over a year. On Thursday, a startup called Antares announced that a test reactor it had placed at the Idaho National Laboratory had reached criticality, making it the first new design to cross this threshold. Criticality means that the nuclear reactions inside the hardware had become self sustaining; it does not mean the reactor had started to generate power.

Antares is one of a number of companies that is basing its design on a new fuel system called TRISO that takes some of the complexity and safety out of the reactor design and places them in the fuel design. The fuel design is based on tiny pellets with a uranium oxide core. The pellets are surrounded by several layers of carbon that can moderate the energy of both the neutrons and lighter nuclei that are released by fission reactions. All of that is encased in a hard ceramic shell that's designed to withstand the highest temperatures that can be produced by the encased uranium.

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On Thursday, President Donald Trump announced his administration's latest attempt to prop up the US coal industry during an incoherent press event that randomly oscillated between energy issues and Trump's fixation with building and renovating monuments in DC. The energy portion of the events was also frequently disconnected from reality.

"Today we're taking historic action to bring down the price of energy and the cost of living for all Americans with the power of clean, beautiful coal," said Trump, apparently unaware that coal is one of the most expensive means of generating electricity in the US.

With wind and solar power getting cheaper, coal has become the second-most expensive way of producing electricity, trailing only the cost of building a new nuclear plant. As a result, no new coal plants have been completed in over a decade, and coal has gone from powering over half the electrical grid to producing only about 15 percent of the nation's electricity. That's before the indirect costs of coal use are considered. It produces the most greenhouse gas emissions per unit of energy, releases dangerous particulates and chemicals into the atmosphere, and leaves behind ash that has high levels of toxic metals.

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