Earth Chauvinism is the state of thought where one assumes that alien life must be like us, on a planet like Earth, in a solar system like ours. This may or may not be incorrect. It is NOT Earth chauvinism to believe extraterrestrial life could be in a variety of forms.

In many cases, Earth Chauvinism may be well founded,

Ex: Carbon is a versitile element, and it is unlikely complex organic molecules could form without it.

Scientific notation is a shorthand expression of a potentially very large or small number.

The first part is a number between 1 and 10 that is expressed to the correct number of significant digits. The second part is how many powers of ten your should multiply by.

Ex: 1.5x10^10

1.5e10

both mean

15,000,000,000

or

15 billion

to 2 significant digits

An equation is a mathmatical relationship describing one or more mathematical variables.

T=0K here represents Temperature equalling zero Kelvin. This is a special case called "absolute zero," and represents the total absence of energy.

(Special note that you shouldn't care about: Absolute zero actually represents the lack of "thermal energy," or the random, non-uniform total kinetic energy of matter. Because of entropy, other forms of energy tend to convert into thermal energy, so we assume that at absolute zero, no energy is present, although it could also be said that no entropy is occuring and no thermal energy is present. This definition would allow for other forms of energy to be present, such as nuclear potential energy necessary for the matter to exist in the first place. But its a moot point because it doesn't happen anyway.)

A light year is the distance light travels in a year, about

9.5 × 10¹⁵ meters

This is a very large number used for measuring astronomical distances. Three examples include:

1.) Our Galaxy, the Milky way, is 1e5 light years in diameter

2.) though there are 12 galaxies in the local group, the next nearest group is the "Virgo Cluster", which is composed of 2500 Galaxies which are 3e7 light years away fromus.

3.) Alpha Centauri is the nearest solar system to us, at 4.37 light years distance.

A special note: When you see something that is, say, 100 light years away, you are actually seeing light that was emitted 100 years in the past. The image of a child born 100 light years away would be seen by us when that person was 100 years old.

1.5) Give the three definitions of life. What are the pro's/cons of each?

(Book page 3-5)

1.) Life in 5 steps

1.) Organic Molecules

2.) Metabolism

3.) Reproduction

4.) Mutation

5.) Sensitivity

2.) Way of the wordy one

"Life is that property of matter that results in the coupled cycling of bioelements in aqueous solution, ultimately driven by radiant energy to attain maximum complexity"

-Folsome

3.) Life Beyond Earth

"Life is fundamentally the activity of a biosphere. A biosphere is a highly ordered system of matter and energy characteriszed by complex cycles that maintain or gradually increase the order of the system through an exchange of energy with its environment."

-Feinberg and Shapiro, Life Beyond Earth

Now, for the pros and cons of each definition:

1.) Life in 5 steps

pro: it is clearly and absolutely defined, there being a checklist of 5 qualities, which, all being met individually classify a being as alive.

con: there are examples of life on earth that do not meet all 5 requirements. Ex, the mule does not reproduce.

2.) The way of the wordy one

pro: it avoids details that might be peculiar to individual situations (like the mule)

con: it expresses Earth Chauvinism by referring to "aqueous solution."

3.) Life Beyond Earth

pro: It characterizes life by a characteristic truly unique to life: Life tends to increase order, which is the opposite of entropy. For example, when determining whether a star and a plant are alive, it is clear the star is not and the plant is alive. The star continually and violently moves toward a low energy state (entropy) wheras the plant collects solar energy and continually binds it into a static state (sugar) for later use.

con: This definition is really complex, and might not hold true in some special situations. Ex: Venus also concentrates solar energy in its atmosphere, would it be alive?

Using the Life in 5 steps model:

1.) Organic molecules: traditional candles are made of beeswax, which is C₁₅H₃₁COOC₃₀H₆₁. This is obviously an organic molecule.

2.) Metabolism: The candle consumes energy from itself, which is not an exchange with the environment. It does however require air in order to carry out combustion, so that is a metabolism in a sense. (Not really.)

3.) Reproduction: A candle may be cut into two, identical, smaller candles. This is kind of like cell division.

4.) Mutation: As it melts, it may or may not melt into a shape better suited for its environment.

5.) Sensitivity: In order to ward off those that might blow it out, the candle constantly wafts smoke at the local predator's eyes, like its larger cousin the campfire.

4 necessary elements: Carbon (C), Oxygen (O), Hydrogen (H), and Nitrogen (N).

2 other necessary elements: Phosphorous (P) and Potassium (K)

crust of the earth: 60 percent Silicon Oxide (SiO₂) and 16 percent Aluminum (Al)

Atmosphere: 78% nitrogen

20% oxygen

.039% Carbon Dioxide

1% Argon

remember: 3/4 organic molecules present

Oceans: Full of organic matter, a lot of Water (H₂O) and salt (KCl) and a great deal of Phosphorous (P) giving 2/4 organic elements and both of the extraneous elements.

The Sun: 75% hydrogen and 24% helium. Not teneble for life.

At face value, the drake equation attempts to clarify the number of detectable civilizations in the milky way.

However, each part of the drake equation is a careful examination of what it takes for life to exist, and often in order to compose our drake equation, we must learn about the characteristics of life and what kind of environment it can live in.

Temperature is the mean kinetic energy of matter. The "heat" is caused by random vibrations of molecules.

The proton would move faster than the alpha particle, because it has less mass.

Remember:

Ke=.5*m*v²

Ke=kinetic energy

m= mass

v=velocity

So, we can see that velocity is  proportional to the inverse square of the mass:

v=SQRT(2Ke/m)

therefore the smaller the mass is, the greater the velocity. If this is confusing, try picking a constant for Ke (as they are at the same temperature) and substituting in the mass of a proton and then of an alpha particle and solve for v.

Additional note: I just found another equation from the text: v=SQRT(3kT/m)

again, v is proportional to the inverse square of the mass

2 hydrogen molecules fall into the star as it forms. The extreme conditions blow off the electrons, leaving 2 protons. The star then fuses them together like so:

p+p --> d+e⁺+γ

γ= a neutrino

e⁺= a positron (anti-matter electron)

d=deuteron (proton + neutron)

p= proton

In terms of potential energy:

two protons repel eachother, so their potential energy in total is U=2kq/r

As radius r approaches zero, their potential energy U approaches infinity. At some point, strong nuclear forces overpower electromagnetic repulsion, and bring the protons together. The resulting reaction consumes this extremely large value U and causes matter to do all sorts of cool stuff, like produce a "d" an "e+," and a neutrino.

The pressure produced by the fusion in the core of the star is matched by the gravitational potential energy of the gas in the outer layers of the star.

As time progresses, heavier and heaver nucleii form as a result of nuclear fusion, until iron is formed which is terrible fuel for fusion. Because the iron won't fuse, the core of the star runs out of energy and collapses. This causes the outer shell of the star to fall in, then "bounce" out. We aren't asked to understand the logic there, but I presume that as it falls in it causes unstable fusion reactions that produce enough energy for the outer layers of the star to blow out.

wikipedia explains core collapse

If you were to take an element, and cut it into smaller and smaller pieces, the smallest possible piece of that element that retains its properties would be an atom.

An Ion is an atom or a molecule with unequal numbers of protons and neutrons. This results in a net charge and the possiblility of ionic bonding, and important chemical bonding characteristic.

Molecules are multiple atoms bound together by electromagnetic forces which, together, have properties that may differ from the constituent elements.

The atom is composed of a nucleus with a positive charge, and a collection of electrons with a negative charge. Atoms tend to have neutral charges, as this is the lowest possible energy state of the atom. However, if multiple atoms are around eachother, together they can achieve an even lower energy state if the have a few electrons fill the outermost electron shells of both atoms. This "sharing" of atoms is often called ionic bonding, although covalent bonding can work on a similar principle.

Nuclear fusion is different in two ways: First, you must force particles together to cause fusion, whereas most molecular bonding requires only a modest activation energy to blow off an extra electron or 2.

Second, nuclear fused particles are bound by strong nuclear forces, whereas molecules are bound by electromagnetic forces.

Carbon is special in 3 ways:

First, its fairly abundant. While not as common as lighter elements, it is not so rare that it cannot be used as the basis of large, multi carbon molecules.

Second, it is extremely versitile. Having 4 covalent bonding spots, it can serve as a multi-purpose puzzle piece binding lots of atoms together in an exponentially huge number of ways.

Third, it is fairly stable. Some larger elements might have the prior two properties, but the more massive elements are subject to eventual decay.

1.) molecules with as many as 13 atoms have evolved in places other than Earth.

2.) Carbon is prevelant in complex molecules

3.) The formation and destruction of interstellar molecules is indicative of the challenges life faces as it forms on early Earth.

temperature: 10K

density:100 molecules/centimeter³

size: 1-300 light years

mass: between 1 and 10^6 solar masses

93% molecular hydrogen

6% atomic helium

<1% heavy elements

Hydrogen

Ocygen

Nitrogen

Carbon

R_* is the rate of star formation.

The first assumption is that no stars have died. This is untrue, but the mass of the stars that have died (all large stars) is small enough to be negligible. The second assumption is that stars form at a constant rate.

New mass estimates indicate 5e11 stars in our galaxy.

It appears that disks for quite commonly around small stars.

In binary star systems, it is possible to have planets for from the disks and maintain stable orbits if the ratio of the mean orbital radius is 7:1 or greater, where either the planet or the second star may  be either factor in the ratio.

If planets come from disks, as many as 1/3 of stars may have planets, or all of them if you say binary stars may have planets.

3.D.32) Describe the astrometric and spectroscopic methods for detecting planets around other stars. What are the advantages and drawbacks of each?

Which method works better for planets orbiting close to their star and which worsk better for planets with larger orbits?

Describe how searches for transits and microlensing can detect planets.

Which method was used to detect most of the planets detected so far?

Astrometric method: If a star is not the center of mass of its solar system, and the system is sufficiently perpindicular to our line of sight, we can detect a small "wobble" as it moves in circles.

Spectroscopic method: If a star is not the center of mass of its solar system and the system is sufficiently paralell to our line of sight, small fluctuations in the wavelength will occur. This is similar to if you rapidly move a speaker close and far from your head while listening to hinder's "lips of an angel." You will feel significantly less pain as the sound moves away.

In both cases, the sun is not the center of mass of the system because another mass is orbiting it. Based on astrometric and spectographic data, we can characterize the mass of the planet.

The spectographic method works best for small orbits, because many oscillations must occur for us to detect a doppler effect with a reasonable degree of certainty.

The astrometric method works best for large orbits.

The transit method looks for small dips in luminosity associated with a planet crossing in front of a star.

Microlensing is when star "A" and planet "B" are in front of star "C" relative to us. As the planet passes in front or behind the star (relative to us) the total gravitational effect of the system on the light from star C will increase slightly, magnifiying the amount of light reaching us. This increase in brightness is very rare, so many stars must be watched.

THe spectroscopic technique has detected most planets so far.

*I'm not sure this stuff is right

There are 1200 exoplanet candidates and 500 known exoplanets, of which 50 reside in the habitable zone.

Presumably, you could divide 1200 and 500 by the number of stars observed to reach this total, and extrapolate a mean and standard deviation number of planets per star. This would of course be an underestimate, because we cannot detect all the planetary bodies. Finally, I can't find good numbers on the number of stars surveyed to get these numbers.

Fp=.5

Our solar system formed from a disk.

This would explain why all the planets orbit the same direction, why the outer planets are gaseous, and why the inner planets are rocky.

• The inner planets are rocky. The outer planets are gaseous.

• We all orbit the same direction, but venus and Uranus rotate differently.
• the planets by pairs are spaced 1.5 to 2 times greater distance than the last pair.

The spacing between each pair of planets would be about twice the spacing between the last

all the planets would orbit in the same direction on on plane

Most the planets would rotate the same way

There would be gaseous outer planets and rocky inner planets

smaller stars would have gaseous planets in closer orbits because the dust that made the  planets would be able to hold ice at a smaller distance from the star.