Dark matter, modified gravity or both?; In a NASA run simulation, international space agencies couldn't stop an asteroid from crashing into Europe; Decades in the making, space tourism is making its way onto the launch pad; Microsoft is set to reinvigorate their Windows Store application; and IEEE Spectrum's weekly selection of awesome robot videos

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Dark Matter: The Situation Has Changed - This link has a YouTube embed and video transcript with Sabine Hossenfelder discussing the phenomenon of dark matter. Hossenfelder begins by distinguishing between dark energy and dark matter. Dark energy, she says, is what makes the universe expand faster. In contrast, dark matter is what makes galaxies spin faster. She elaborates on this by saying that the observed speed of rotation for star clusters and galaxies is faster than can be explained by gravity that emanates from the known matter. Therefore, in the 1930s, Fritz Zwicky conjectured that an unobserved form of matter, dark matter, must exist. Hossenfelder notes that early in her career as a particle physicist, she didn't think the problem was very interesting. She simply thought that someone would discover the dark matter particles and win a Nobel prize and that would be the end of it. As time has gone on, however, the observations have changed her thoughts on the matter. If dark matter is made up of particles, then new observations are becoming harder to explain, not easier. So the question she's asking now is whether dark matter is even comprised of particles. She runs through a list of "problems" for the idea of dark matter as a particle, and says that an alternative explanation may be modified gravity. Unfortunately, however, moodified gravity doesn't solve some other problems that are - in fact - solved by dark matter. Many physicists look at this as a pair of competing hypotheses, but Hossenfelder suggests that maybe the two theories should be combined with a phase transition between particles and fields, and the right question to ask is which idea to apply in various contexts.

Here is her conclusion:
But more importantly, if you look at the mathematics, modified gravity and particle dark matter are actually very similar. Dark matter adds new particles, and modified gravity adds new fields. But because of quantum mechanics, fields are particles and particles are fields, so it’s the same thing really. The difference is the behavior of these fields or particles. It’s the behavior that changes from the scales of galaxies to clusters to filaments and the early universe. So what we need is a kind of phase transition that explains why and under which circumstances the behavior of these additional fields, or particles, changes, so that we need two different sets of equations.

And once you look at it this way, it’s obvious why we have not made progress on the question what dark matter is for such a long time. There’re just the wrong people working on it. It’s not a problem you can solve with particle physics and general relativity. It a problem for condensed matter physics. That’s the physics of gases, fluids, and solids and so on. So, the conclusion that I have arrived at is that the distinction between dark matter and modified gravity is a false dichotomy. The answer isn’t either – or, it’s both. The question is just how to combine them.

Here is the video:
Click through for the transcript.

In a NASA simulation of an asteroid impact, scientists concluded they couldn't stop a space rock from decimating Europe - International space agencies participated in a simulation where they learned the location and trajectory of an incoming asteroid and tried to react in time to avoid a catastrophic impact. Unfortunately, in this simulation, they were unable to prevent the asteroid from crashing down on Europe. The simulation was led by NASA and it involved a simulated asteroid that was identified at 35 million miles from Earth, iwth a potential strike in six months time. These international experts learned more about the asteroid's location and movement daily and tried, unsuccessfully, to cooperate to stop the collision. The collaboration began on April 19, 2020 and the simulated impact happened on October 20. The researchers concluded that six months is not enough lead time to stop an incoming asteroid with existing technologies. NASA continues to experiment with new ways to dodge a hypothetical asteroid in the future, with leading candidates being to detonate an explosive on an asteroid's surface or ram a spaceship into the asteroid, either of which could, conceivably, change the rock's trajectory enough to bypass the planet. Another option might be to use lasers to heat and vaporize the rock before it crashes into the planet.

Space tourism – 20 years in the making – is finally ready for launch - In this article by the US Air Force professor and space policy analyst, Wendy Whitman Cobb, the author discusses current events that are leading to an imminent takeoff of the space tourism industry. She notes that there have already been examples of space tourism by the ultra-wealthy, such as the 2001 trip of Dennis Tito, as well as trips by seven other people. With SpaceX and Blue Origin now emerging in the industry, however, the number of trips by space tourists is set to double, just in the next twelve months. She also notes that trips into Earth orbit are very expensive, because of the amount of fuel that must be burned, but companies like Blue Origin and Virgin Galactic can take people into sub-orbital space at a much lower cost. It is possible for tourists to experience weightlessness, even on these short, sub-orbital trips. For the space tourist who wants the full-orbit experience, SpaceX - founded in 2001 - is currently the only option. Prices for SpaceX to shuttle a tourist to and from the International Space Station are around $55 million dollars, and sub-orpital trips cost somewhere around $200,000 to $250,000. These prices may seem expensive, but Tito's trip in 2001 cost $20 million, which could have purchased 80-100 flights from Virgin Galactic or Blue Origin.

Microsoft is building a new app store for Windows 10 in major revitalization effort - The authors argue that the current incarnation of the Windows Store app suffers from problems with usability and aesthetics, and as a result it has not been very successful during the last few years. In contrast, they say that the new version will be updated monthly and it will come with some important policy changes. In particular big changes that are expected include allowing developers to upload unpackaged windows applications (EXE files); allow them to host software on their own content delivery networks (CDNs); and allow them to make use of 3^rd party commerce platforms. In summary, Microsoft is hoping to reinvigorate the Windows Store application by making it a more open platform. -h/t OS news

Video Friday: Good Robots for Bad Knees - For this week, the IEEE Spectrum weekly selection of awesome robot videos contains the following:
- A wearable robotic orthosis from Roam Robotics
- NASA's Ingenuity's third flight
- Here is a $3,000 Robot in action, climbing a ladder, picking up objects, and navigating an office space. Tongue in cheek (I think), IEEE Spectrum says, "This right here, the future of remote work."
- Automated COVID testing from ARM Institute (with some music that is reminiscient of the SWAT theme
- and more
Here is an experiment to see how people like being hit by drones (described here):

And here is a drone having a really bad day:

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