> An observer in that frame finds the CMB to be equally hot in every direction. We do not, so we infer that the Sun is moving at about 370 km/s (1/800 the speed of light) with respect to the CMB rest frame.

If it isn't that way for us, how do we know it should be that way?

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Full rotation of galaxy in 200 million years according to this article

https://phys.org/news/2015-02-milky-rotate.amp

Toward the orange patch in this figure, which is where the CMB is hottest. That's a Mollweide projection of the whole sky, where the Milky Way disk is the noisy horizontal red line. The galactic center is in the middle. Our orbital velocity is toward some point on the left side.

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There is pressure for it to not kill hosts before they are able to infect others though.

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>Viruses don't want to kill the host,

This isn't really true. Viruses mutate to spread faster. Covid never killed a meaningful number of hosts as it is (from the perspective of spreading), and even the ones that did die can spread it for weeks before they go. This isn't a desease where you get it and die immediately and never was. Covid doesn't really care if you die or clear the virus after 14 days. Either way it's been passed on.

There really isn't any pressure for it to get less dangerous.

You might have misheard or been misinformed -- the impact of the extended galactic mass distribution (including dark matter) is that the orbital velocity remains approximately uniform over a wide range of radii (see again figure 16 of this review article). The orbital period does not.

Orbital periods are only uniform near the very centers of some galaxies (not ours, and mostly dwarf galaxies). That's actually a challenge to the standard dark matter picture (the core-cusp problem) because it requires that the system's density be uniform in the relevant region, which is not what dark matter simulations predict. But there are lots of proposed solutions to this.

Now for a technology to harness potential energy relative to the CMB. A cosmic regeneration brake, so to speak.

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Yes, it's true.

The outer stars are moving too rapidly to stay in orbit, and under normal calculations they should be thrown out of the galaxy. Additional gravitational forces must be keeping them in orbit at those faster speeds, and that's where the theory of dark matter comes in.

For example, Venus is moving at 78K mph, while Saturn is moving at 22K mph (because it is much farther away from the sun). If Saturn were moving at the same speed as Venus, it would be thrown farther out from its current orbit.

Wouldn’t that mean all viruses should eventually mutate into harmless but fast spreading illnesses? Or is that something specific of coronaviruses?

I have not seen strong evidence of a meaningful effect size when it comes to long term adverse outcomes in mild cases when limiting my search to robust, high quality studies, so given that this is a science sub, I’d love to see your citations. In my experience reading papers related to long Covid, the following applies:

• findings are often limited to a cohort of older or hospitalized patients

• when findings are generalized to mild cases, this is done by conducting a (voluntary) survey, almost always with abysmal response rates. It’s not viable to measure hazard ratios when 25% of your sample responded to your survey, since response bias has the potential to modulate those HRs by up to 4x.

• findings are nebulous or poorly defined, for example “any Covid symptom after 28 days” is often considered LC, which groups someone who has a lingering cough at 29 days in the same group as someone who has debilitating fatigue 3 months down the line. This lack of granularity limits the ability to draw conclusions about what “nasty things” are happening.

To date, I have yet to find a study which combines the following:

• uses health database data to avoid the bias inherent in voluntary responses

• performs subgroup analyses by age and pre-existing health, as well as clinical severity of the case

• adequately captures severity and duration of LC in the analysis.

Thus, the question “how much more likely is a healthy 30 year old to have lifestyle-limiting fatigue 6 months after mild Covid” remains unanswered.

The closest parallels I have found are studies which example very specific neuropsychiatric outcomes, such as this paper: https://www.thelancet.com/journals/lanpsy/article/PIIS2215-0366(22)00260-7/fulltext

If you’re scientifically inclined it’s a fantastic read. It breaks down the neurological outcome trajectories for COVID patients compared to a matched control group with another URI by age and other factors.

If anything, what the study tells me is that we under-estimate the risks of regular old URIs that aren’t Covid.

Case in point, for the “adults” group, which excludes older adults and children, the total cumulative risk after 2 years was 29.2% after Covid, and 29.1% after another URI.

That difference is not statistically significant.

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> Hang on, if all motion is relative, why can't I pick an object moving in the direction I would like to travel at 99% of the speed of light, the travel at the speed of light relative to that, thereby traveling at 199% speed of light relative to my starting location.

See relativistic velocity addition

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I thought it could be just for a moment, or a few seconds, like a camera flash, but is the large energy consumption because you'd need a long exposure, and thus, you'd need to run the laser for a super long time, to get an image?

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Also, the fact that COVID jumped species is a blaring example of a disease mutating for the worse..

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The speed of light is the same for every reference frame, and no object with mass can ever go at or above that speed. If you stood on an rocket going at 99% the speed of light relative to the earth and threw a rock at 10% the speed of light relative to you, that rock wouldn’t be moving at 109% the speed of light relative to earth. Instead, the Lorentz equations tell us the rock would move at about 99.2% of the speed of light relative to earth.

Talking about the “fabric of space” isn’t really an accurate way to describe the universe because it implies that there is some sort of universal background that everything takes place against. In reality, it’s more like every single object in the universe has its own “fabric” of space that it sees, and two different objects might completely disagree about what the fabric looks like, and both could be correct. It’s very confusing and not helpful for these scenarios (relativistic speeds).

Tl;dr: very high speeds are not intuitive and don’t work the way you might think. Just remember that nothing can ever go faster than the speed of light in any reference frame, and there’s no known way to “cheat” this. There also is no “absolute” speed: everything is relative to something else, whether it’s the earth or the sun or the CMB or whatever

> the Sun is moving at about 370 km/s (1/800 the speed of light) with respect to the CMB rest frame

In what direction is the Sun moving at that speed, relative to the CMB?