General Science Thread

You know that prize Chinese turnip who thought playing with CRISPR on humans was a grand idea? Sentenced to three years behind bars for being an unethical prat.

Yup. Even China's government thinks the guy's nuts.

Should've gone for a tougher sentence, in my view. Much tougher. <_<

Edited by Euodiachloris on Dec 30th 2019 at 4:21:03 PM

Better article, context.

Note though that we were apparently wrong about the particular genetic change reducing people's life expectancy.

Those kids need following for decades before any fallout can be properly evaluated.

And, even then... any of their grandkids will need checking up on. Mucking about with the germ line can take a while to properly show up. Any dog breeder can tell you that for free.

I have to be "that person" here and observe that someone was going to do this eventually, no matter how strict the regulations were. Obviously it's unethical and should be punished, but there is no putting the fundamental science back in the box.

Edited by Fighteer on Dec 30th 2019 at 4:06:06 AM

Phys.org: New evidence shows that the key assumption made in the discovery of dark energy is in error

Oh, dear. The information in this report is way over my head from a purely technical perspective, but I'll try to summarize.

Since the 1990s, a huge debate in cosmology and physics has occurred over the existence of "dark energy", an unseen, anti-gravity-like force that is causing the outward expansion of the universe to accelerate over time, rather than decelerate due to its own gravity as one would expect.

"New observations and analysis made by a team of astronomers at Yonsei University (Seoul, South Korea), together with their collaborators at Lyon University and KASI" suggest that the primary evidence that has been used to support the theory of dark energy, type 1A supernovae, may be inaccurate.

What I glean from the article is that estimates of the red-shift of these supernovae, deemed "standard candles" because their brightness is uniform and thus their apparent luminosity can give us precise distance calculations, don't take into account the relative age of the stellar populations in which they reside.

Correcting for this data eliminates dark energy entirely.

Again, this is very technical, but more recent studies of these supernovae, compared with studies of the cosmic microwave background (CMB), have disagreed as to the rate of cosmic expansion, giving rise to the hypothesis that the universe is not only expanding, but that the expansion rate itself is getting faster over time. If the supernovae data are being interpreted incorrectly, it might reconcile this difference.

I should stress that this is just one paper, but there's bound to be a ton of new inquiry sparked by it.

Edited by Fighteer on Jan 6th 2020 at 4:55:46 AM

so time for a Big Crunch in theories?

No. Observations of the geometric flatness of the universe have detected no curvature to within the margin of error of the instruments. Ergo, our universe is probably infinite and its expansion will slow to zero at an infinite time in the future. Concerns about a "Big Rip" are almost certainly wrong, but a Big Crunch is equally unlikely.

Edited by Fighteer on Jan 6th 2020 at 4:56:07 AM

It never ceases to amaze me how much hay the press can make with preprints that aren't even formally published. Sorry, my dislike of "science by press release" is showing.

Anyhow, the paper argues that the luminosity of a supernova is dependent on the star's age. And since light from distant heavily redshifted supernovae by default takes a long time to come here, the supernovae took place a long time ago on stars that didn't become old during the time from Big Bang to supernova, introducing a correlation between luminosity and redshift that can be mistaken for dark energy.

I did mention that, right? Anyway, I didn't get this from the mainstream press, but from someone I like tweeting a science journal. So there's plenty of room for it to be dissected and pored over by the academic community. Still, it would be amazing if such a fundamental and revolutionary concept as dark energy got overturned because of what amounts to a math error.

Edit: If it turns out our universe is perfectly geometrically flat with no dark energy, that's going to spawn a whole new wave of hypothesizing about the role of the Anthropic Principle. Of course, recent work has potentially ruled out the idea of gravity existing in an extra dimension, so it's possible that the revolution in physics of the 2020s will be the discovery that all the fancy things we've thought might be going on actually aren't.

Edited by Fighteer on Jan 6th 2020 at 6:39:13 AM

With the exponential growth in Tech year on year and the likelihood of calculations being far more precise and complex thanks to the ever expanding possibility of Quantum Computers going into vogue this decade, I can't wait for what discoveries they will help us find.

Its gonna be wild.

Not an expert either, but if there is in fact no dark energy, doesn't the average mass-energy of the universe have to be adjusted downward (by a factor of three or four)? That could imply a negative curvature to the universe (since the previous estimates concluded that the universe is most likely flat, I am assuming that adjusting the average density downward supports the negative curvature model). But I'm just guessing.

Dark energy doesn't contribute to the mass-energy distribution of the universe; it does contribute to the geometry, however, adding a negative term to offset mass-energy. It's a bit confusing; I'm not sure I have it completely accurate.

Our universe is calculated to be perfectly geometrically flat to within the limits of precision of our observations, but dark energy adds a term that makes its curvature negative. Take that out and we're back to flat.

Edited by Fighteer on Jan 9th 2020 at 2:51:00 PM

An old academic paper, but interesting approach to a vexing question: Did Smoke From City Fires in World War II Cause Global Cooling? TLDR: Most likely not, but it's not clear how much difference there is between that and a nuclear war scenario.

Without reading the paper, there would seem to be many similarities. My main thought is that nuclear weapons fling dust much higher in the atmosphere, allowing it to carry farther and remain longer.

Dont underestimate the power of a city-sized conventional fire storm. The real question is how many nuclear weapons, and of what magnitude?

@Fighteer: What do you mean the universe's expansion will slow to zero? I thought the prevailing hypothesis was the universe expands until heat death.

In this model, we will indeed suffer heat death. A geometrically flat universe is infinite in size and its gravitational potential energy is exactly equal to its expansion kinetic energy. This means its expansion will slow to zero at an infinite time in the future. Heat death is inevitable in this model.

Now see my impression is that under the Poincaré recurrence theorem such a static world would be cyclic over (humongously) long timescales.

The who whatsit now? PBS Space Time hasn't covered that yet. Define your terms, sir!

Edited by Fighteer on Feb 27th 2020 at 4:06:25 AM

Poincaré recurrence theorem. That article doesn't mention it but AFAIK it's not necessarily applicable to expanding universes.

I wouldn't think so. The total volume occupied by all matter and energy in the universe will expand until infinite time, so there is no static finite space in which recurrence could happen. If the universe has zero (or positive) curvature, then it is infinite in size even discounting expansion, so the same problem occurs.

Now, PBS Space Time did recently cover an interesting consequence of the universe being truly infinite. If there is a finite number of possible quantum states in any given volume of the universe at any given time, in an infinite universe, every possible state of any finite system must occur an infinite number of times (assuming that the underlying physical properties of the entire universe are identical everywhere). That would mean there is an infinite number of me typing this exact post right now, and we don't even need multiverse theory for it!

I hurt my brain a little thinking about that. I hope my identical copies also got headaches.

Edited by Fighteer on Feb 27th 2020 at 5:18:10 AM

There is a jellyfish that can carry out remote attacks on people. To whit, this jellyfish - known as the "upside-down jellyfish" - releases a mucus containing stinging cells that allow it to kill animals at a certain distance from the actual jellyfish. In humans, contact with mucus can provoke mild skin reactions which are called "stinging water", because hitherto it wasn't known that it's due to a remote attack by a jellyfish.

A jellyfish Ranger. Real Life: making D&D combos look unimaginative.

A biology question that might border of psychology: can someone with a high amount of stress eventually start being older than he or she looks?

Don't you mean the other way around? There is ample evidence that stress causes epigenetic effects that increase the rate of cellular aging. This is an established medical fact, nothing exotic or weird about it.