solar system - Is it odd that our Sun has so many planets?

From an exoplanet-finding point of view, the Sun has between one and three planets.

The major exoplanet-finding techniques in current use involve watching for either periodic Doppler shifts as the planet's gravitational pull causes the star to wobble, or periodic brightness shifts as the planet transits the star. Both require that the planet is large enough and close enough to generate a measurable signal and that the orbital period is short enough to let astronomers distinguish periodic variations from one-off variations; the transit method additionally requires that the planet's orbit crosses the star from the point of view of Earth (which favors close-in orbits). Looking at the Solar System with these techniques:

1. Mercury: too small


2. Venus: Maybe visible


3. Earth: Maybe visible


4. Mars: too small


5. Jupiter: Highly visible


6. Saturn: Orbital period too long


7. Uranus: Orbital period too long


8. Neptune: Orbital period too long


9. "Planet 9": Orbital period too long

If you look at this graph of exoplanet discoveries, Jupiter is solidly in the cluster of blue Doppler discoveries, Saturn is just past the "we've been watching for one full orbit" right-hand edge of that cluster, Earth and Venus are somewhat below the sloped minimum-period-mass line, and everything else is nowhere near the detection range.

The reason the Sun has far more known planets than any other star is simply because we've got a better look at it.

evolution - What animals stop other members of their species from mating and why?

As the comments suggest, I think a little basic reading so you understand the definitions involved here might be appropriate. The questions are a bit anthocentric, and I think that's why folks with a bit more biological culture might be concerned about the answers.

Alpha type structures can be found in all sorts of animals. Sperm competition, where many males simply mate with the female and let the sperm work it out are also v common from snakes to mice to primates.

Its hard to say without you asking a more specific question, but the essential question is whether the competition occurs between the animals themselves or between the intermixed sperm of the males inside the female. If that sounds gross, that's a typical reaction if you are not a monkey, snake, duck or mouse to name a few. Different species choose different social roles in mating and for reasons that may be difficult to divine.

For animals in an alpha troop modality, the alpha male will eventually get older or weaker and the younger ones will have their chance to mate. There is always tomorrow. That's my very brief answer.

It might be worthwhile to take some time to read some about this - a page of response to your questions is not going to really answer your questions. (I say this having answered several of them :). I would recommend "The woman that never evolved" by Sarah Hrdy. As a feminist in the 70s Hrdy decided to do a survey of primate male/female roles in mating, to try understand how human men and women became who they are (and who has not wondered this?). This book will give you an idea of how so many different animals have come to different roles and possibly why.

Since I have a little time today, I'm adding a couple of tangential references: Mice sperm have responded to sperm competition so much by evolving hooks on their heads and chain up together and swim together which enhances the chances of paternity. Ducks are quite different. they have a lot of forced copulation, but female choice of mate is still quite influential. Duck vaginas are very complicated, with corkscrews and dead ends to make it difficult to copulate without 'consent'.

evolution - How does "be altruist to those who are similar to you" evolve?

The above answers are good, but have unfortunately confused some of the concepts in the theory, I will do my best to explain.

What we are assessing is how does one behaviour evolve, links with cooperation and altruism are applications of this. The process of selection in evolution removes the the worst individuals from the gene pool, thus those with comparatively good genes survive to reproduce. With physical traits these mechanisms are well understood, with behaviour there are still multiple theories which have not been concluded but our understanding of them is reasonably complete.

Inclusive fitness is the combination of direct and indirect fitness, direct being your personal fitness, indirect being fitness gained from others. In general this is measured in terms of reproductive success (RS) (the number of offspring you successfully raise to reproductive maturity). Out of this understanding came Hamilton's Rule:

---

                               r.b > c

---

Where r is the relatedness, b is the benefit & c is the cost. In this scenario the cost is a reduction in RS, the benefit is a gain in RS. Benefits are multiplied by the relatedness to the offspring. In normal diploid organisms (Gets DNA from both parents) you are related by 0.5 (half from mother, half from father), but only related to your brother/sister's offspring by 0.25. Thus, if you have two children you have a direct fitness of 1, if your brother has two children you gain an indirect fitness of 0.5. Thus, you would prefer under normal circumstances to have your own children rather than raise your brothers.

Altruism is suffering a cost for someone else's benefit, @Winawer mentions the greenbeard theory, which rests on the assumption that if you can tell someone has the same genes as you then you know that you are related to them in someway and this will be on average be greater than to any other individual. Altruism is a behaviour, defined above, and not a specific action like giving up your own reproduction, thus it is a part of cooperation and not separate from it.

It is true that there are different forms of altruism however these are all just perspectives pertaining to the same theory. ALL behaviour is selfish, reciprocal altruism is just an example of this. Reciprocal altruism, is "If you scratch my back, I'll scratch yours" (You need help now, I may need help in the future), it is altruistic because you suffer a cost for another's benefit but it is selfish because it is still in the individual's interest to help. This is where prisoners dilemma comes in, this is basically asking the question "how do I pick the most optimal situation in this scenario?"

For simplicity, it is generally ill advised to study behaviours in humans because of the implicit bias we have in our judgment on ourselves. From political and religious associations that cloud judgment to the fact that we always strive to see ourselves differently. Also, there are all sorts of ethical difficulties in actually testing and manipulating theories on us. Thus we normally study animals to get around this. However your question specifically talks about people so I will try and answer this based on biological theory alone.

Based on the foundations above, why would someone behave altruistically to someone only 'similar' to you? The biggest difficulty is knowing that we understand all the costs and benefits involved, most of the time we only know some of them and its impossible that you can know all of them because you can't know what you don't know. Humans have effectively 'bootstrapped' behaviours which are 'for the good of society' building on from previously developed behaviours. However we are still fundamentally asking a question about Hamilton's Rule. Being seen as a part of society induces altruistic behaviour towards you (because you are seen as worth something), this is good for you and the costs associated with being altruistic are usually low. Thus you would never rationally die for 1000 unrelated individuals unless you had at least had all the children you were going to have and raised them to be independent. But you would vote, by voting you suffer a tiny cost, your time, for a huge benefit. Benefits might include:

• Being seen as caring for others (altruism given to you)


• Possible benefits to yourself (less tax, more support, better roads, clean air.. etc)


• Possible benefits to others related to you


• General good moral of your community, leading to a better life.

There could be thousands of other benefits that I can't, off the top of my head, think of. The cost is negligible and the benefit is intangible but probably higher than the cost. Relatedness isn't important (so long as it is greater than 0), if the cost is sufficiently low or the benefit is sufficiently high. I hope this has helped clarify your thinking and answer the question.

For further information:

Provides the foundations

Hamilton W.D. (1963) Evolution of altruistic behaviour. The American Naturalist 97 354

Hamilton W.D. (1964) The Genetical Evolution of Social Behaviour I . Journal of Theoretical Biology 7 1

Hamilton W.D. (1964) The Genetical Evolution of Social Behaviour II. Journal of Theoretical Biology 7 17

The current controversy mentioned in another answer is from this paper, it is widely dislike but does have some support. It is slightly off topic from from the question here, but eusociality is fundamental to our understanding of evolutionary behaviour:

Nowak M.A., Tarnita C.E. & Wilson E.O. (2010) The Evolution of Eusociality. Nature 466 1057

human biology - Do hot drinks cool you down?

It is quite the old wives tale that drinking a hot drink cools you down. If you don't really think about it it does seem somewhat logical: increasing temperature will cause your body to try and cool down faster. This is of course flawed by the fact that you have increased your temperature before cooling it back down again.

I have had a bit of a look, but have been unable to find any evidence that addresses the fact that drinking a hit drink may make you feel cooler after sweating a little bit, rather than actually changing anything about your net temperature. Basically, is the 'cool down' just the placebo effect (you feel cooler because you think you feel cooler), or is there any evidence for a 'real' effect of hot drinks cooling you down? Or is there evidence that hot drinks do nothing at all except heat you up a bit before you come right back to the same temperature?

amateur observing - Pinhole Projector: Can I use a specific solar optical eye piece to focus the Transit of Mercury?

The whole point of a pin hole projector is that it doesn't need any optics just a pin hole.

If you are after magnification then that is related to the distance you project the solar image behind the pin hole, with a projection distance of 1000mm the solar disc will have a diameter of about 9mm. Increasing the distance will increase the size of the image but also reduce its brightness. Increasing the size of the pin hole will increase the brightness but reduce the sharpness of the image.

I suppose you could use a handheld magnifying glass to look at a small image but would not personally recommend it as unless you are extremely careful there is always a risk of fire or even blinding yourself or someone else when using a lens near an unfiltered solar observation. There is a famous story of an experienced astronomer setting his beard on fire because he left the cap off his telescopes finder.

Life planets orbiting black-holes. Can/Do they really exist?

Well, first things first. It's not likely to have a planet orbiting near a black hole and in significant time dilation because the tidal effects would likely tear anything that close apart. Certainly a planet orbiting a stellar mass black hole would need to be quite far away so as to not be torn apart, so any time dilation would be pretty small.

Around a super-massive black hole, the tidal effects are smaller and a nearish orbit with some measure of time dilation is possible. (see link below for more specifics),

http://physics.stackexchange.com/questions/110044/time-dilation-factor-for-the-circular-orbit-at-3-2-schwarzschild-radius

But a stable planetary orbit, you probably max out at about 20% time dilation and only around a super-massive black hole, where there's only 1 per galaxy. The idea of 1 day to 100 years isn't practical, it's 80 days to 100 days if you're talking about a stable planetary orbit.

and, I'm not sure you'd want to be that close to the black hole in the center of the universe, not because the orbit isn't stable, but because stars are in that orbit too. It might not be a safe place to be.

So, in reality, you'd want a stellar mass black hole and a distant orbit, where the time dilation would be quite small, and in that scenario, yes, life is possible because of tidal energy, so a planet could have liquid surface water and an atmosphere, even if the black hole gave off very little light and heat.

Such a planet in a tidal-energy orbit would probably be tidally locked which would protect the far side from any gamma rays the black hole spits out when it eats, so it would in theory be a good place for life. No significant light source, unless it was a binary system, so, plants would have it harder, but there would be heat.

There's another problem. The creation of black holes tends to blow everything appart in a huge explosion. It's unclear that a planet would survive a black hole's birth, so you might need a captured planet.

Finally, intelligent life . . . we really don't know enough about how common intelligent life is on other planets. Life might be fairly enough, but intelligent life is far less clear and there's other factors than just time.

Today, we simply don't know enough to predict if there's intelligent life out there or not. There probably is life elsewhere in the universe, though even that isn't 100% certain, but intelligent life, there's far too many unknowns in that equation. But I think a black hole might not be optimal for the formation intelligent life because of the lack of light so, much less photosynthesis, so, slower oxygen formation (if it follows the same pattern the earth does) and the unlikeliness that a planet would survive the black hole's creation.

ecoli - What makes E. coli yellowish?

Bobthejoe's comment is the best answer so far. Despite many other types of bacterial colonies being "more" yellow than E. coli, E. coli is definitely not white.

Flavins, especially riboflavins, are the predominant compound responsible for this coloration.

biochemistry - During starvation, does the human body do anything to prioritize which organs receive nutrients?

The glycogen in the liver begins providing blood glucose. Muscle glycogen is used as fuel by the muscles, fat cells (adipose tissue) release fatty acids to manufacture ketone bodies in the liver and to be used by the brain as fuel, and body proteins are converted to glucose.

In short, the body's metabolism shifts to catabolic reactions.

If this continues for too long, you begin to see effects of starvation:

• Inadequate tear production


• Enlarged/tender liver


• Muscle atrophy


• Rashes, sores, or peeling skin

In short, deficiencies of energy, protein, iron, and zinc can really mess you up in the long term.

hawking radiation - How Does Black Hole Evaporation Look From the Inside?

The space itself is falling into the black hole. Below the event horizon - in the timelike zone - an observer is falling towards the singularity, together with the space.

Seen from this falling observer, space looks like vacuum outside the black hole. Close to the singularity tidal forces become an increasing problem. But for a sufficiently large and "benign" black hole, an observation can't locally distinguish between spacetime inside and spacetime outside the black hole.
Otherwise it would violate the principle of relativity.

So - seen from the falling observer - we get short-lived virtual particles, as in usual vacuum. Due to space-time curvature, the segment of vacuum in the black hole isn't perfectly symmetric, including quantum fluctuations.
This tiny asymmetry results in (few) real particles, when seen from outside the black hole, when applied to the (light-like) zone near the event horizon.
It should be fundamentally possible to probe the tiny asymmetry of the resonances with particle experiments.

An observer hovering just below the event horizon would be tachyonic in the in-falling spacetime.

hubble telescope - Is the Tombaugh Regio on Pluto visible from Earth?

Unfortunately making maps that have this level of detail from the ground is not possible with current telescopes. There are 2 problems; first, it takes a lot of magnification to resolve Pluto and even more to resolve surface features. Second, from the ground you need more than just magnification, you need EXTREMELY stable skies or that will wash out the surface features. Getting just one super sharp image is not enough, you need several to ensure that you have high enough signal to noise to believe the surface features are real.

This is why Marc Buie, who used the High Resolution Channel on the Advanced Camera for Surveys on HST to create the image you put in your question. Unfortunately, even that level of resolution is not possible anymore as HRC is no longer functional. These kind of maps can be very hard to make.

There have been other maps of pluto, both from the ground and using HST. Here is a compilation of several using a compilation of ground based photometry, the Fine Optical Camera on HST and the ACS HRC. As you can see from the ground based photometry you can make a map, but it is very poor resolution compared to what HST can do.

There have been other HST press releases about those other images

There is a good blog post about how they match up from the museum of applied arts and sciences at the Sydney Observatory. But the bottom line is that they match up pretty well, but not perfectly. This is expected as we expected volitle transport on the surface so the surface features will change. As you can see in the image below, that there were a lot of changes from the map made in 1994 to the one made in 2003. So one would expect changes going out to 2015.

So, yes your intuition is valid, but Pluto's surface is dynamic so it will be changing on you!

biochemistry - Evolutionary origin and exogenous cues of ~28 day infradian rhythm?

A double-blind, prospective study during the fall of 1979 investigated
the association between the menstrual cycles of 305 Brooklyn College
undergraduates and their associates and the lunar cycles.

.... Approximately 1/3 of the subjects had lunar period cycles, i.e.
a mean cycle length of 29.5 ± 1 day. Almost 2/3 of the subjects
started their October cycle in the light 1/2 of the lunar cycle,
significantly more than would be expected by random distribution. The
author concludes that there is a lunar influence on ovulation.

(Menstrual and Lunar Cycles, Friedmann E., American Journal of Obstetrics and Gynecology, 1981)

Another source supports this conclusion, finding that "a large proportion of menstruations occurred around the new moon."

Somewhat related, this study found that light exposure shortened menstruation cycles.

In summary, there seems to be a good amount of data suggesting that lunar cycles do in fact calibrate the length of human menstrual cycles to some degree.

surface - What is the color of Venus if it has no atmosphere?

According to the webpage from the Planetary Habitability Laboratory of the University of Puerto Rico: The Real Colors of Venus without the Clouds, did the following:

We combined radar topography and emissivity to generate the surface texture assuming a generalized basalt composition with gray to light brown tones, depending on the iron and sulfur content. In the images we also included the effect of the 'orange sky' of Venus thus given its surface a more dark brown appearance

As in the image below.
Additionally, according to the model the scientists made, they state that

Under white light the surface should look grayish and more similar to the Moon.

As an aside, the website also shows a fictional map of Venus with 70% surface water.

What is an efficient way to spike 10-50 cells to a culture

If you are you working with primary cell cultures or cell lines may be you could do this when cells are in suspension, after tripsinization, mix them well with a 5mL serologial pipete in a falcon 50mL tube and plate to a 100mm2 with a final volume of 7mL. And finaly draw an eight with the plate in the hood more than 3 times to mix them well.

Edit: For the addition of 10-50 cells, count these cells with trypan blue, and do a 1:100 dilution, for example if you have 1e6 cells in 10mL you could take 0.01 mL (10 microliters) to get 1, 000 cells

And then you add the 0.01mL into 1mL of cell media to get 1 cell per 1 microliter, and then if you wanna get 10 cells, take 10 microliters, and so on

orbit - What is the centre of rotation of Pluto?

As StephenG stated, this is not the reason why Pluto is no longer a planet.

The center of rotation of the two bodies is called the barycenter. It can be calculated with accuracy, knowing the mass of the two bodies and the distance separating them. See :

The little ring around Pluto in the center describes its path. The barycenter of this binary system is on the opposite side of the ring, starting from Pluto.

solar system - Open problems in astronomy that an amateur (with a PhD in some other field) would have a chance of solving?

What are some open problems in astronomy that an amateur would have a chance of solving? Suppose the amateur has a PhD in some other field, owns a basic telescope, a set of filters, diffraction gratings, cameras, and happens to know a lot about machine learning, signal processing, spectral estimation, statistics & design of experiments, and basic physics and chemistry.

Is there better tags available (where's "research")?

solar system - Why did Earth need material from comets to assemble the raw materials for life?

It's often speculated that matter from comets played a crucial role in the development of life on Earth. For example, Maps of Time says,

Many of the ingredients of the early atmosphere (including much of its water), together with many of the organic chemicals that formed the first life forms, may have been brought to Earth by the comets that bombarded its surface for the first billion years of its life (~Kindle location 1922).

Why the presumption that these materials must be brought by comets? Did Earth even have the right atoms to make water and those organic chemicals (hydrogen, oxygen, carbon)? And what are comets doing with heavier elements in the first place? My understanding is that comets are (for most of their lives) very far from the run, and my impression was most of the elements other than hydrogen and helium and are concentrated close to the sun, with T Tauri Wind having push hydrogen and helium further away.

What would the apparent size of the four stars in the Capella system be from the L1 point between the first pair?

Capella is a system with four stars in two binary pairs (source: Wikipedia). If an observer were located at the L1 LaGrange point between the larger pair, how many degrees of the sky would each of the stars - both the first and second pairs - occupy?

entomology - How do insects such as crickets circulate blood through their antennae?

Insects do not posses closed circulatory system, but a space where organs float in a fluid called hemolymph. They don't have blood vessels (but some arthropodes have pumps that act a like heart). The hemolymph allows nutrients and excretion products to diffuse, but usually doesn't serve as a means to transmit oxygen to the tissues.

In insects, the oxygen is pumped through a series of little tubes named tracheae. Trachae connect the tissue directly to the air, allowing gas diffusion efficiently.

Antennae and wings have very little metabolic needs, mainly because (in the first case) they're formed by some neurons. Movement is achieved by muscles located in the base of the antenna (where it doesn't have circulation issues). The nerve tissue has the neuron bodies located in the basis too, so the nutrients and oxygen can diffuse through the axon.

orbit - Orbital resonances and position of planets

Watched the video, and I thought it was really cool seeing the modeling of different young solar-systems. The orbital resonances they were talking about were for smaller objects that form debris fields in resonance with a giant planet. Since they only looked at models for the inner planets, the closest example to the bit in the video with our current solar-system would be Jupiter's Hildas. For that specific part of the video, they only showed one inner most giant planet. For more than one, Resonances like that are unlikely to form between giant planets, like in our solar system where most of the resonance objects fall inside Jupiter or outside Neptune.

The mathematics gets too complicated for me to know for sure, but as I understand it, planets in resonance is neither stable nor unstable, unless the aphelion of one planet is in resonance with the perihelion of another, in which case the planets could drawn together I would think. That's my amateur answer to your question. I wouldn't think orbital resonance affects stability.

When one planet is dominant and the other quite small, then resonances appear largely stable (Neptune/Pluto for example), provided they never get close to each other, which Neptune-Pluto don't.

Jupiter and Saturn were thought to have entered orbital resonance at one point in the early solar-system and that, from what I've read, affected other objects in the solar system but didn't affect their relation to each other much. I think the only way to get any kind of answer is to run long term simulations on various model. In short, planets can be stable both in resonance with each other, and not in resonance and planets can be unstable, again, either in resonance or not in resonance, though if they have unstable orbits, they won't stay in resonance for long.

gel electrophoresis - Is there a cheap and easy way to check for potentially unsafe UV exposure?

My lab has an older large Fotodyne tabletop UV transilluminator for visualizing gels. It has a UV blocking cover that hopefully reduces UV that passes through, but I've always been suspcious as to how effective it is. Obviously this part can be replaced with a new one, but short of guessing on the recommended 50 hr lifetime, how would one know the level of UV passsing through? I considered simply placing a gel on top, but that is far from quantitative. I am really just curious if there is an easy to make and/or obtain sensor that could be used to know when UV expose could be considered dangerous.

molecular genetics - Is ovum + ovum fertilization possible for human?

In humans is it possible to fertilize a ovum with another ovum from the same female subject?

I already found some works in which the ovum is fertilized by a somatic cell (see e.g. this ), but I am looking for fertilization specifically by another ovum.

Around a year ago I found in the internet a Japanese (ongoing) study on this, but cannot locate it any more.

I would greatly appreciate any help.