formation - Is there a mechanism that makes small moons more rounded than comets?

67P/Churyumov–Gerasimenko has a highly irregular dumbbell shape. But the sample of comet shapes observed is very small, so I wonder if irregular shape is the norm for comets and for small moons. Many known moons are no larger than this ~4 km diameter comet. The smallest moons imaged are modestly irregular, basically just elongated, at least they don't have a waist like 67/P. The most elongated moon is perhaps ~135/60 km Prometheus.

Is there reason to believe that moons which are too small for hydrostatic equilibrium get more rounded than comets of similar mass and composition? Moons differ from comets in several ways. AFAIK: Moons in general have a very different gravitational environment, a much more stable distance to the Sun, experience more frequent impacts, another formation history if not captured. Composition and density depends on the formation distance from the Sun, although even ~300 km Hyperion has a similar density as 67/P.

Should we expect the small moons in general, and the moons of Pluto especially, to be rounded or dumbbell shaped? If 67P is a merged binary, isn't it more likely for two objects to merge if they are moons instead of comets, since neighboring moons have low relative speed? ~100-200 km Janus and Epimetheus look as if they could merge fairly calmly. Does the lack of (observed) dumbbell shaped moons tell us something about 67P, that its shape is a rare outlier for example?

How early/late is the human race as intelligent life in the universe/milkyway?

I think this is a very subjective question depending on your point of view. If you assume that the history of the universe is 13.8 billion years old, then humans have only been around for 200,000 years which makes us very late at evolving. But of course the entire history of the universe hasn't been written yet!

I always find these sort of calendar/24hr clock representations very insightful too. If you look at this image below, modern "intelligent" humans have been around for the last 6 minutes of the year, if the age of the universe was 365 days long, so not very long at all!

That being said, I think there is another answer to your question, but becuase we don't know how long the universe/milky way will last for, its impossible to say or indeed ever know for how long intelligent life could actually evolve for.

I'm afraid i'm going to have to say somewhere in between too, as we simply cant see into the future.

Do both TSG and Proto-oncogenes have to suffer mutations to cause cancer?

The typical idea is that several "hits" are required. The difference between proto-oncogene and TSG is mainly in their heritability - TSG mutations are usually recessive (because a heterozygote will still express sufficient suppressor, e.g. p53) whereas proto-oncogenes are dominant (if a consitutively active agent e.g. Ras is present, it doesn't matter if the other allele is under normal control).

A single "hit" in this way (TSG or proto-oncogene) may just cause the cell to die, which isn't a bad thing (in fact, TSG such as p53 often work by inducing apoptosis because proliferative errors make them accumulute). A tumour only results when a single cell accumulates sufficient mutations and genomic damage to gain a reproductive advantage over the cells in its vicinity.

However, you are asking about cancer, which is not simply a tumour. Tumours are any sort of abnormal growth, i.e. neoplasms, but they can be benign! This means they stay in their tumour capsule, do not grow at a fast rate and do not invade or metastasise other tissues. The distinct characteristics that define a cancer are very well-known and were published in a well recognised paper by Weinberg & Hanahan, 2002, "The Hallmarks of Cancer".

The six primary hallmarks of cancer. The first two are the ones most people know, but the other ones are just as essential for

1. Independence from external growth signals: Cancer cells produce their on autocrine growth factors or have mutated signal pathways active without GF receptor stimulation (Oncogenes).


2. Resistance to anti-growth signals: Cancer cells do not respond to growth-inhibitory factors from outside or inside (Tumour suppressor genes).


3. Evasion of apoptosis: Cancer cells resist signals which cause normal cells to die (apoptose) (these are also tumour suppressor genes).


4. Limitless replication / Evasion of cell senescence: Apart from stem cells, all normal cells can only replicate their genome a certain number of times before the ends of the chromosomes known as telomeres are too short, disintegrate and cause the cell to enter senescence or die. Cancer cells express telomerase, which extends telomeres and maintains replicative potential.


5. Sustained angiogenesis: Tumours and cancers form massive cell heaps. Tumours may stall growth because blood vessels do not grow into the heap and supply the cells with the nutrients needed to proliferate. Cancer cells have found a way to induce blood vessel growth (VEGF) and sustain it in order to maintain nutrient supply.


6. Invasion and metastasis: This is the crucial, most distinguishing difference between benign neoplasm (tumour) and malign neoplasm (cancer). Cancer cells degrade the extracellular matrix around them (by secreting metallo-matrix-proteases, MMP), which allows them to move away from where they are and invade into neighbouring tissues. They can also spill into blood vessels this way (especially if the neoplasm is well-vascularised thanks to hallmark number 5), where they can travel to other sites in the body and grow new cancerous tumours in other locations.

There are four more emerging hallmarks and enabling characteristics (immune evasion, inflammation induction, modification of energy metabolism, genomic instability), which allow better cancer growth and make a cancer more dangerous if it acquires them, but these are outside the scope of this answer.

biochemistry - What are the biochemical processes occurring when food spoils?

During putrefaction of animal tissue, lysine is decarboxylated into cadaverine and arginine is decarboxylated into putrescine. These compounds are deemed to be toxic.

A serving of meat contains 8 g of protein, corresponding to 640 mg lysine and a little bit less of arginine. Let's go straight and say that a spoiled meat serving contains 640 mg cadaverine and a little bit less of putrescine.

In rats, the acute oral toxicity for both polyamines is around 2000 mg/kg, let'assume that this is valid for humans also. According to these rough calculations, to have an acute toxic effect, a 70kg man that is resistant to the direct toxic effects of microbes, should eat 140 grams of cadaverine, corresponding to 218 smelly rotten meat servings.

[composition and toxicity data taken from wikipedia]

telescope - Is it possible to use the stars to determine the passage of time?

In the night sky in 10,000 years, two things will have changed in relation to the stars. The first, the rotational axis of the Earth will have changed, shifting the celestial sphere. The second, the stars themselves will have moved a bit relative to each other due to proper motion. So, the night sky will be quite different in 10,000 years, but still recognizable, particularly the constellations which will have changed somewhat but will still be identifiable. I would posit that as long as the person or persons were at least casual star gazers or astronomy enthusiasts (not even necessarily professionals) they could estimate how much time has passed in the course of their slumber, I'd say with a margin of error of about +/-2000 years. Should they be trained astronomers that margin of error should fall.

Why does the eclipse in this video look annular?

In this article about the AS870 flight that flew through the umbra of the March 8-9 2016 solar eclipse, there is a link to a YouTube video showing the eclipse recored by a handheld camera in the cabin.

Of course this is personal video and not recorded for analysis, but the images - especially during the zoomed part - remind me of an annular eclipse, rather than a total eclipse. Below are some screenshots - the weak Fresnel reflections in the cabin window act a bit like attenuators (ND filters) and give less saturated, though distorted views. Basically they all look like donuts.

My first thinking was that if it was a total eclipse on the ground, it couldn't be annular at 35,000 feet closer to the moon. But thinking and looking again, the sun is near the horizon, and the plane at about 150 West longitude is not necessarily closer to the sun than observers on the ground were in Indonesia circa 120 East.

My question is - is that just corona, or is the plane farther away enough from the moon at this time and location to make the eclipse annular?

It may be helpful to read about hybrid eclipses.

note: I'm looking for a quantitative answer, not an opinion.

There is another version of the video on YouTube with more views, but the narrative doesn't hold a candle to double rainbow guy original and musical version.

Here is a screenshot of a typical AS870 flight from flightradar24.com, pretty much between 152 and 158 degrees west.

This is from the second link in the top line - the Alaska Airlines blog entry for the flight.

How an eclipse could possibly appear annular from a plane over one place on the planet while appearing total on the ground at another place on the planet 5,000 kilometers away (note, these occur at different times - the shadow is moving relative to earth and the earth is rotating):

asteroids - Is the Dwarf Planet class really necessary?

A lot of the naming conventions were originally "because they remind us of things we already called this", or simply "tradition". How we name things has slowly but surely adjusted with time as more objects were found, and a more robust classification system was needed.

Imagine it like having bins to sort your toys into. If you have a small number of balls, perhaps you'd stick them all into a single bin called "balls". But as you get more and more balls, you find they no longer fit into that bin. Looking at them, you notice they are all either quite small, or quite large. So you make two bins: small balls and large balls. Or maybe you notice they are all either very soft (stuffed or Nerf versions, perhaps), or very hard (baseballs, for example). So you could have a "soft balls" and "hard balls" bins. Keep collecting ever more balls, and you may need three, four, etc. boxes to fit them all in. And each time you will naturally try to order them so that each box contains balls that are similar to each other: these are all soft and green, these are all hard and white, these are all big and bouncy, etc. This applies equally well to all sorts of collections: baseball cards may start all together, but then get sorted into teams and years or even individual players as a collection gets very large, and so on.

This is basically what's happened as we've classified and reclassified objects we've found in our solar system. We started with a small number of objects, but as we found more and more of them it became too unwieldy to stick them all together, so we started to separate them more and more.

Ceres was labeled a planet because it seemed like a tiny version of, but otherwise very similar object to, existing planets. Then we eventually discovered there are a lot of things in the same general orbital region as Ceres, and if those were to also be planets then we'd soon have a gigantic list of planets. Since all these objects seemed pretty similar, and came from the same general region, they were given their own class of objects: asteroids.

Pluto was labeled a planet due in part to some initial errors in the data that suggested it was larger than it actually is. Despite a growing number of oddities about it that made it look increasingly un-planet-like, tradition left it as a "planet"; it wasn't particularly problematic for this one little odd-ball to be lumped with the others. Finding a host of new, similar, and sometimes—in the case of Eris, at least—bigger objects forced a reconsideration.

Incidentally, there are also comets, which are not the same as asteroids. Asteroids are rocky objects in the inner regions of the solar system. Comets are icy objects from the outskirts of the solar system: the Kuiper belt and Oort cloud, in particular. They are vaguely similar to each other: generally very small, lumpy, potato-like objects, but we noticed that asteroids were mostly rocks and metals between Jupiter and Mars, and comets were mostly ices beyond Neptune. So we separated them into their own groups.

Pluto is more comet than asteroid, and likely originated from either the Kuiper belt or Oort cloud. In this case, it likely got knocked into a closer orbit via gravitational interactions with the gas giants, or possibly a star that got close enough to the Oort cloud.