KaiserScience

Produces bile to break down fats

Liver produces bile, a detergent that breaks up fat into small particles.

Bile is stored in the gallbladder, and released when you are digesting a meal.

Gallbladder Bile release GIF

Here we see bile salts emulsifying a globule of fat.

from pathwayz.org

Detoxification

“Almost all the blood in your body passes through the liver.”

US Dept of Veterans Affairs, Liver as Filter

“As blood passes through the liver, it breaks down substances, such as prescription or over-the-counter drugs, street drugs, alcohol, and caffeine.”

“Our bodies naturally produce some harmful (toxic) chemicals or poisons, and those are also broken down by the liver.”

“In this way the liver acts as a filter to clean your blood.”

Energy storage in glycogen

The liver takes excess sugars and links them together into a large molecule called glycogen.

Glycogen is stored until energy is needed.

Image from National 5 Biology, nat5biopl.edubuzz.org

Makes cholesterol

The liver makes cholesterol.

cholesterol

Contrary to popular belief, cholesterol is not bad for you: In fact, you’d instantly stop living if you didn’t have any in your body. All cell membranes in animals have some cholesterol as part of their structure. And many critical hormones are made by using cholesterol as a starting point.

Why do people think that cholesterol is bad? Over the last 200 years the American diet has changed. People now have vastly less whole foods, vegetables, whole grains, fruits, beans and legumes, and instead now eat more fatty foods, and more cholesterol-rich meats. As a result, most people now have far more cholesterol in their bodies than is necessary, and for some people, high levels of cholesterol increase the risk of many diseases.

The solution is not to make our bodies cholesterol-free; the solution is to change one’s diet to reduce the excess added cholesterol.

Cholesterol used to build bile

from Wikimedia by Mcstrother. CC BY 3.0

Cholesterol used to build hormones

Steroid hormones by Gianpiero Pescarmona

Cholesterol used in all cell membranes

Image from sliderbase.com/spitem-808-1.html

References

Cholesterol & heart disease – there is a relationship, but it’s not what you think

How does bile break up fat?

Think of washing dishes after dinner, without using detergent. Very hard to clean the plates. The fats in your food aren’t water soluble, so they clump together, stick to surfaces, and are hard to remove.

Now add detergent: that’s a two-sided molecule. One side attracts water, while the other side attracts a fat. Once the water, fat and detergent are all held together, it is easy for fats to dissolve. Dishes can be cleaned.

Same thing for digesting food. Your body can’t digest clumped up fats. Your digestive enzymes only touch the fats on the outside of clumps. But now that we add bile, it acts like a detergent. Water and fat are held together, so the clumps break up, and the small bits are now easily digested.

Diffraction

February 12, 2018 6:37 pm

(adapted from Giancoli Physics)

Waves spread as they travel. When waves encounter an obstacle, they bend around it and pass into the region behind it. This phenomenon is called diffraction.
$Wave diffraction$
The amount of diffraction depends on the λ (wavelength) of the wave and on the size of the obstacle:

$Water waves diffraction$

(a) λ is much larger than the object. Wave bends around object almost as if it is not there.

(b) and (c) the λ is shorter than the size of the object. There’s more of a “shadow” region behind the obstacle where we might not expect the waves to penetrate — but they do, at least a little.

(d) the obstacle is the same as in part (c) but the λ is longer. More diffraction around object.

Rule: Only when λ is smaller than the size of the object will there be a shadow region.

Water waves diffracting around an island

$wave-diffraction-around-island-by-marcelzijlema-a$

And then the next step

$wave-diffraction-around-island-by-marcelzijlema-b$

Sound waves can diffract in unusual and unexpected ways. See our article on anomalous sounds

Even light itself can diffract! See our article on light’s wave nature.

Fresnel diffraction

French scientist, Augustin-Jean Fresnel,

Discovering Fresnel diffraction: The Greatest Mistake In The History Of Physics

Example – diffraction in Boston Harbor

from bostonfoodandwhine.com

As part of the Central Artery/Tunnel project – the Big Dig – Applied Coastal Research and Engineering did research on wave diffraction in Boston Harbor, around Spectacle Island.

…A detailed beach nourishment design was developed for the southern shoreline of Spectacle Island, which is located within Boston Harbor… The propagation of waves from Massachusetts Bay into Boston Harbor was modeled using the refraction/diffraction model REF/DIF1. This model predicts the transformation of waves in areas where bathymetry is irregular and where diffraction is important, such as at Spectacle Island. The resulting wave heights, periods, and directions were used as input to both longshore and cross-shore sediment transport models. These models were employed to simulate the performance of several different beach fill designs…

Beach Nourishment Design for Spectacle Island

$Spectacle Island Boston Harbor Diffraction$

This map is from mass.gov/eea/images/dcr

Learning Standards

2016 Massachusetts Science and Technology/Engineering Curriculum Framework

HS-PS4-1. Use mathematical representations to support a claim regarding relationships among the frequency, wavelength, and speed of waves traveling within various media. Recognize that electromagnetic waves can travel through empty space (without a medium) as compared to mechanical waves that require a medium

HS-PS4-3. Evaluate the claims, evidence, and reasoning behind the idea that electromagnetic radiation can be described either by a wave model or a particle model, and that for some situations one model is more useful than the other. [Emphasis is on how the experimental evidence supports the claim and how a theory is generally modified in light of new evidence. Examples of a phenomenon could include resonance, interference, diffraction, and photoelectric effect.]

Anomalous sounds

February 11, 2018 4:17 pm

Here’s an actual news story: “Loud booms heard across Southern New Hampshire: Source of the noise still unclear.”

Nashua police say they don’t know what caused several loud “booms” Saturday afternoon that were heard across Southern New Hampshire. Many reports came from Nashua and surrounding towns, but the sounds were reported as far north as Manchester and as far south as Westford, Massachusetts. Some who heard it in Nashua said they felt their houses shake. Police and fire departments said they have not been alerted to any incidents related to the noise in the area. The cause is still unclear.
– WMUR 9 News. (An ABC affiliated TV station) 2/10/18

How is it possible that such loud, possibly building shaking sounds could be heard in some parts of this town – yet in other parts of the city other residents reported no sound? Also, in a town next door no reports have yet surfaced of anyone hearing them – yet in a town after that, some residents also reported these booming sound.

The answer? It’s complicated, but basically:

(a) there are a wide variety of ways that sounds are produced – including some bizarre ways that most people have never heard of

(b) Sound waves don’t always move in a straight path like many people imagine; changing temperature/density of the air can cause sound waves to bend and diffract, so:

(b1) sound can sometimes travel much further distances than one would expect

(b2) sound can come from a location very different from what “seems obvious” just by listening

(b3) local wind can mask sound, so the same loud sound might be heard in one neighborhood, yet be undetectable by people just a mile away.

Basic idea

Sound doesn’t move in a straight line: It spreads out radially, and then – because of a phenomenon known as diffraction – it can even bend around obstacles.

$Diffraction of sound Hyperphysics$

Source: Hyperphysics, Diffraction of sound, http://hyperphysics.phy-astr.gsu.edu/

“If the air above the earth is warmer than that at the surface, sound will be bent back downward toward the surface by refraction.” – Hyperphysics

$sound refraction Hyperphysics 2$

Normally, only sound initially directed toward the listener can be heard, but refraction can bend sound downward – effectively amplifying the sound.

This can occur over cool lakes.

$sound refraction Hyperphysics 3$

Sounds also can bounce off of objects, and come to our ears from a direction different than the original source.

sound-reflection

ABD Engineering writes:

…wind alters sound propagation by the mechanism of refraction; that is, wind bends sound waves. Wind nearer to the ground moves more slowly than wind at higher altitudes, due to surface characteristics such as hills, trees, and man-made structures that interfere with the wind.

This wind gradient, with faster wind at higher elevation and slower wind at lower elevation causes sound waves to bend downward when they are traveling to a location downwind of the source and to bend upward when traveling toward a location upwind of the source.

Waves bending downward means that a listener standing downwind of the source will hear louder noise levels than the listener standing upwind of the source.

Temperature gradients in the atmosphere. On a typical sunny afternoon, air is warmest near the ground and temperature decreases at higher altitudes. This temperature gradient causes sound waves to refract upward, away from the ground and results in lower noise levels being heard at the listener’s position.

In the evening, this temperature gradient will reverse, resulting in cooler temperatures near the ground. This condition, often referred to is a temperature inversion will cause sound to bend downward toward the ground and results in louder noise levels at the listener position.

How Weather Affects an Outdoor Noise Study by ABD Engineering and Design

Cheung Kai-chung, from Physics World (Hong Kong), (Translation by Janny Leung) offers this explanation

Sound wave will be refracted to the ground when traveling with the wind.

$Sound waves refracted 1$

Sound wave will be refracted upwards when traveling against the wind.

$sound waves refracted 2$

Source: Why can a distant sound be heard easier when it travels with the wind? Why does it become weaker if it travels against the wind?

Can wind mask even loud sounds?

A discussion to consider, from Physics forums, includes this phenomenon: “Yes. I have a freeway about 10 blocks South of my house. I can hear the traffic very clearly with no wind, or a South wind. If there is even a slight North wind, the traffic noise becomes almost inaudible. If there is a brisk North wind (over 15 MPH), the sound is completely gone.”

https://www.physicsforums.com/threads/does-wind-affect-how-far-sound-can-travel.149392/

Sound refraction due to cold air:

Also this “…if the air close to the ground is colder than the air above it then sound waves traveling upwards will be bent downwards. This is called Refraction. These refracted sound waves can act to amplify the sound to someone standing far away.”

http://sciencewows.ie/blog/does-sound-travel-faster-in-warm-or-cold-air/

Sound seems amplified when traveling over water.

In School-for-Champions we read

“If you are sitting in a boat, a sound coming from the shore will seem louder than the same sound heard by a person on land. Sound seems to be amplified when it travels over water. The reason is that the water cools the air above its surface, which then slows down the sound waves near the surface. This causes refraction or bending of the sound wave, such that more sound reaches the boat passenger. Sound waves skimming the surface of the water can add to the amplification effect, if the water is calm.”

$sound_amplified_over_water_refraction$

See their full lesson here School-for-champions.com: Sound_amplified_over_water

Can snow on the ground affect sound?

“When the ground has a thick layer of fresh, fluffy snow, sound waves are readily absorbed at the surface of the snow. However, the snow surface can become smooth and hard as it ages or if there have been strong winds. Then the snow surface will actually help reflect sound waves. Sounds seem clearer and travel farther under these circumstances.” – Colorado State Climatologist Nolan Doesken

“Hums” have been widely reported by national media in the UK and the United States. The Hum is sometimes prefixed with the name of a locality where the problem has been particularly publicized: e.g., the “Bristol Hum” or the “Taos Hum”. It is unclear whether it is a single phenomenon; different causes have been attributed. ”

Human reactions to infrasound –

https://en.wikipedia.org/wiki/Infrasound#Human_reactions

Skyquakes or mystery booms are unexplained reports of a phenomenon that sounds like a cannon or a sonic boom coming from the sky. They have been heard in several locations around the world. –

https://en.wikipedia.org/wiki/Skyquake

The microwave auditory effect, also known as the microwave hearing effect or the Frey effect, consists of audible clicks (or, with speech modulation, spoken words[citation needed]) induced by pulsed/modulated microwave frequencies. The clicks are generated directly inside the human head without the need of any receiving electronic device. The effect was first reported by persons working in the vicinity of radar transponders during World War II. (Wikipedia)

References

Our first article.

How Weather Affects an Outdoor Noise Study by ABD Engineering and Design

This following discussion has helpful images.

Why can a distant sound be heard easier when it travels with the wind? Why does it become weaker if it travels against the wind?

A discussion to consider, from Physics forums, includes this phenomenon:
“Yes. I have a freeway about 10 blocks South of my house. I can hear the traffic very clearly with no wind, or a South wind. If there is even a slight North wind, the traffic noise becomes almost inaudible. If there is a brisk North wind (over 15 MPH), the sound is completely gone.”

https://www.physicsforums.com/threads/does-wind-affect-how-far-sound-can-travel.149392/

Also this “…if the air close to the ground is colder than the air above it then sound waves traveling upwards will be bent downwards. This is called Refraction. These refracted sound waves can act to amplify the sound to someone standing far away.”

http://sciencewows.ie/blog/does-sound-travel-faster-in-warm-or-cold-air/

Sound seems amplified when traveling over water

https://www.school-for-champions.com/science/sound_amplified_over_water.htm#.WoBbQ5M-fVo

Diffraction of sound waves

https://katrinasiron21.wordpress.com/properties-of-sound-waves/diffraction-of-sound-waves/

Temperature inversion and sound waves

http://kxan.com/blog/2015/02/13/why-does-sound-carry-farther-on-cold-calm-mornings/

Also look into: Humans hearing infra sound waves

“Colorado State Climatologist Nolan Doesken says: “When the ground has a thick layer of fresh, fluffy snow, sound waves are readily absorbed at the surface of the snow. However, the snow surface can become smooth and hard as it ages or if there have been strong winds. Then the snow surface will actually help reflect sound waves. Sounds seem clearer and travel farther under these circumstances.””

Related topic: The Hum is a phenomenon, or collection of phenomena, involving widespread reports of a persistent and invasive low-frequency humming,rumbling, or droning noise not audible to all people. Hums have been widely reported by national media in the UK and the United States. The Hum is sometimes prefixed with the name of a locality where the problem has been particularly publicized: e.g., the “Bristol Hum” or the “Taos Hum”. It is unclear whether it is a single phenomenon; different causes have been attributed. ”

Human reactions to infrasound – https://en.wikipedia.org/wiki/Infrasound#Human_reactions

Skyquakes or mystery booms are unexplained reports of a phenomenon that sounds like a cannon or a sonic boom coming from the sky. They have been heard in several locations around the world. – https://en.wikipedia.org/wiki/Skyquake

Learning Standards

Skeptical analysis of unexplained phenomenon.

The Massachusetts STEM Curriculum Framework addresses “Understandings about the Nature of Science”

Scientific inquiry is characterized by a common set of values that include: logical thinking, precision, open-mindedness, objectivity, skepticism, replicability of results, and honest and ethical reporting of findings.

Science disciplines share common rules of evidence used to evaluate explanations about natural systems. Science includes the process of coordinating patterns of evidence with current theory.

Most scientific knowledge is quite durable but is, in principle, subject to change based on new evidence and/or reinterpretation of existing evidence.

The “College Board Standards for College Success: Science” addresses these same skeptical inquiry methods in Standard SP.1: Scientific Questions and Predictions. Asking scientific questions that can be tested empirically and structuring these questions in the form of testable predictions.

Students recognize, formulate, justify and revise scientific questions that can be addressed by science in order to construct explanations.

Students make and justify predictions concerning natural phenomena. Predictions and justifications are based on observations of the world, on knowledge of the discipline and on empirical evidence.

Students determine which data from a specific investigation can be used as evidence to address a scientific question or to support a prediction or an explanation, and distinguish credible data from noncredible data in terms of quality.

Students construct explanations that are based on observations and measurements of the world, on empirical evidence and on reasoning grounded in the theories, principles and concepts of the discipline.

The “Benchmarks for Science Literacy” (AAAS) addresses these same skeptical inquiry methods:

In science, a new theory rarely gains widespread acceptance until its advocates can show that it is borne out by the evidence, is logically consistent with other principles that are not in question, explains more than its rival theories, and has the potential to lead to new knowledge. 12A/H3** (SFAA)

Scientists value evidence that can be verified, hypotheses that can be tested, and theories that can be used to make predictions. 12A/H4** (SFAA)

Curiosity motivates scientists to ask questions about the world around them and seek answers to those questions. Being open to new ideas motivates scientists to consider ideas that they had not previously considered. Skepticism motivates scientists to question and test their own ideas and those that others propose. 12A/H5*

SAT subject test in Physics: Waves and optics

• General wave properties, such as wave speed, frequency, wavelength, superposition, standing wave diffraction, and Doppler effect

Binnacle

February 8, 2018 6:52 pm

Our school is right by Boston Harbor – learning about the sea is second nature to many of our staff. So we love to tie maritime history and science into our curriculum.

Photo by RK

As you enter our school, you pass by a binnacle – what was it used for?

A binnacle is a waist-high case, found on the deck of a ship, that holds the compass.

It is mounted in gimbals to keep it level while the ship pitched and rolled.

It also has a mechanism to compensate for errors in detecting the Earth’s magnetic field.

Every ship’s captain would use one, for navigating in and out of Boston Harbor, and around the world.

Here we see Boston Harbor – now let’s get in to how the binnacle works!

This map is from mass.gov/eea/images/dcr

Why did we need to develop the binnacle?

Excerpted from Magnetic Deviation: Comprehension, Compensation and Computation by Ron Doerfler

Today, radio navigational systems such as LORAN and GPS, and inertial navigation systems with ring and fiber-optic gyros, gyrocompasses and the like have reduced the use of a ship’s compass to worst-case scenarios. But this triumph of mathematics and physics over the mysteries of magnetic deviation, entered into at a time when magnetic forces were barely understood and set against the backdrop of hundreds of shipwrecks and thousands of lost lives, is an enriching chapter in the history of science.

The Sources of Compass Error

Ron Doerfler writes:

Compasses on ships fail to point to true (geographic) north due to two factors:

Magnetic variation (or magnetic declination) – the angle between magnetic north and geographic north due to the local direction of the Earth’s magnetic field, and

Magnetic deviation – the angle between the compass needle and magnetic north due to the presence of iron within the ship itself.

The algebraic sum of the magnetic variation and the magnetic deviation is known as the compass error. It is a very important thing to know.

Magnetic Variation

Magnetic variation has been known from voyages since the early 1400s at least. Certainly Columbus was distressed as he crossed the Atlantic to find that magnetic north and true north (from celestial sightings) drifted significantly…

We now know that the locations of the Earth’s magnetic poles are not coincident with the geographic poles—not even close, really—and they are always wandering around.

Image from commons.wikimedia.org, Magnetic_North_Pole_Positions. Red circles mark magnetic north pole positions as determined by direct observation, blue circles mark positions modelled using the GUFM model (1590–1980) and the IGRF model (1980–2010) in 2 year increments.

What’s the difference between where a compass needle points (magnetic north) and the geographic north pole? This is called the declination It’s smallest near the equator, but generally gets large as one moves towards the poles.

On this map, the green arrows – the direction from the compass – point towards the magnetic north. The red arrows point towards the geographical north pole.

Notice how the left location (in Pacific ocean) shows the compass point a bit east of where we’d hope it would point; in the right location (in Atlantic Ocean) it shows the compass point a bit west of where we’d hope it points.

There’s also a special line where the magnetic north and geographic north point in the same direction.

Image from Drillingformulas.com by Rachain J i

Here we can see how many degrees of deviation there are – the # of degrees between where the compass points, and where the north pole is. But – wait for it – the image is changing? The magnetic fields are significantly changing every year!

from USGS.gov, faqs, what is declination

Magnetic Deviation

Ron Doerfler writes

There is an additional effect on the compass needle that took much longer to appreciate and even longer to understand. This magnetic deviation is due to the iron in a ship…

The first notice in print of this effect was by Joao de Castro of Portugal in 1538, in which he identified “the proximity of artillery pieces, anchors and other iron” as the source.

As better compass designs appeared, a difference in compass readings with their placement on the same ship became more apparent. Captains John Smith and James Cook warned about iron nails in the compass box or iron in steerage, and on Cook’s second circumnavigation William Wales found that changes in the ship’s course changed their measurements of magnetic variation by as much as 7°.

Here we see a modern naval vessel, with it’s own magnetic field. As a metal ship moves through Earth’s magnetic field, an electric current is produced within all that metal – and that current produces it’s own magnetic field. This field can affect the ship’s compass. That’s why a binnacle is designed to be adjustable, to compensate for this field. – RK

image from slideplayer.com/slide/1632522/

Ron Doerfler writes

Captain Matthew Flinders (1774-1815) spent years in the very early 1800s on voyages to investigate these effects…. [he] eventually discovered that an iron bar placed vertically near the compass helped overcome the magnetic deviation. This Flinder’s bar is still used today in ships’ binnacles.

Apps & Interactives

NOAA Historical Magnetic Declination

Activities

Hands-on Activity: Nautical Navigation. Teachengineering.org

https://oceanservice.noaa.gov/education/lessons/plot_course.html

ASA 105, Coastal Navigation

Educational opportunities and museums

http://www.capecodmaritimemuseum.org/education/

https://timeandnavigation.si.edu/navigating-at-sea/longitude-problem/solving-longitude-problem/chronometer

http://abycinc.org/?page=standards

Important components

Quadrantal spheres (spherical quadrantal correctors)

Hood, over the compass bowl

flinders bar (vertical, soft iron corrector)

Learning Standards

Ocean Literacy Scope and Sequence for Grades K-12
6. The ocean and humans are inextricably interconnected: From the ocean we get foods, medicines, and mineral and energy resources. In addition, it provides jobs, supports our nation’s economy, serves as a highway for transportation of goods and people, and plays a role in national security.

Massachusetts 2016 Science and Technology/Engineering (STE) Standards
7.MS-PS2-5. Use scientific evidence to argue that fields exist between objects with mass, between magnetic objects, and between electrically charged objects that exert force on each other even though the objects are not in contact.

HS-PS2-1. Analyze data to support the claim that Newton’s second law of motion is a mathematical model describing change in motion (the acceleration) of objects when acted on by a net force….{forces can include magnetic forces}

HS-PS3-5. Develop and use a model of magnetic or electric fields to illustrate the forces and changes in energy between two magnetically or electrically charged objects changing relative position in a magnetic or electric field, respectively.

History standards

National Standards for History Basic Edition, 1996
5-12 Identify major technological developments in shipbuilding, navigation, and naval warfare and trace the cultural origins of various innovations.

Massachusetts History and Social Science Curriculum Framework
The Political, Intellectual and Economic Growth of the Colonies. Explain the importance of maritime commerce in the development of the economy of colonial Massachusetts, using historical societies and museums as needed.

National Curriculum Standards for Social Studies: A Framework for Teaching, Learning, and Assessment, National Council for the Social Studies, 2010.

PSAT Science questions

About the PSAT This is designed to measure the ability to understand and process elements of reading, writing, and mathematics…. The College Board now also offers two PSAT variations: the PSAT 10 for sophmores, and the PSAT 8/9 for freshmen and eighth graders. These variations generate score reports that measure students’ college readiness and skillsets. … Continue reading →

This gallery contains 3 photos.

February 8, 2018 12:18 pm

Good hypothesis vs bad hypothesis

In science, what is the difference between a good and a bad hypothesis A hypothesis is something actually testable. Consider these examples:

A. Someone claims “lightning is caused by angry ghosts.” If true then you’d predict that when ghosts are angry, there’d be more lightning.

But this can’t be tested.There is no way to determine whether ghosts are angry – or whether their wrath is correlated with thunderstorms.

We can’t measure ghosts so there are no testable predictions. It is thus not a good hypothesis.

B. Someone claims “lightning is caused by electrical charges moving from the ground to the clouds.” If true then you’d predict that when there is an imbalance of electrically charged particles (electrons) then electrons might move from one place to another.

We can measure electrical charges. The idea is testable so it is a good hypothesis.

C. Someone claims “Planets orbit the Sun at different speeds, because speed is related to the gravitational pull of the Sun, and the further away a planet from the Sun is, the less of a pull it feels. If its true then you’d predict that planets like Mercury are pulled more, and move faster.

This can be tested. We do have ways to measure gravitational pull, distance from the Sun, and speed. Since it makes testable predictions, it is a good hypothesis.

http://www.astro.wisc.edu/~mab/education/astro103/lectures/l2/l2.html

February 6, 2018 6:23 pm

Distinguishing Fact, Opinion, Belief, Prejudice, and Stereotypes

Adapted from: Fowler, H. Ramsey. The Little, Brown Handbook. Boston: Little, Brown, 1986

Neil Degrasse Tyson

Facts

are verifiable things that really occurred, or are actually true.

We can determine whether it is true by researching, by examining evidence. This may involve numbers, dates, testimony, etc. (Ex.: “World War II ended in 1945.”) The truth of the fact is beyond argument if the measuring devices, or records, or memories, are correct. Facts provide crucial support for the assertion of an argument.

In science, a fact is a repeatable careful measurement (by experimentation or other means), also called empirical evidence.

In history, a historical fact is a fact about the past. It answers the very basic question, “What happened?” Yet beyond merely listing the events in chronological order, historians try to discover why events happened, what circumstances contributed to their cause, what subsequent effects they had. – Norman Schulz

Facts by themselves are often meaningless until we put them in context, draw conclusions, and, thus give them meaning.

Opinions

are judgments based on facts. Opinions should be an honest attempt to draw a reasonable conclusion from factual evidence.

For example, we know that millions of people go without proper medical care, and so one could form the opinion that the country should institute national health insurance, even though it would cost billions of dollars.

An opinion should be changeable: in science we are actually supposed to change our views if we have new evidence

By themselves, opinions have little power to convince. You must let your reader know what your evidence is, and how it led you to arrive at your opinion.

Beliefs

are convictions based on cultural or personal faith, morality, or values. Statements such as “Capital punishment is legalized murder” express viewpoints, but are not based on facts or evidence. Beliefs cannot be disproved. Since beliefs are inarguable, they cannot serve as the thesis of a formal argument.

There is nothing wrong with having beliefs – we all have them. But we should be careful to distinguish between opinions and beliefs – or clearly explain to the reader what our view is, and what is based on. – RK

Prejudices

are opinions based on insufficient or unexamined evidence. Example “Most women are bad drivers.”

Unlike a belief, a prejudice is testable: it can be analyzed on the basis of facts.

To some extent, all people form some prejudices, or accept them from others – family, friends, the media, etc. – without testing their truth.

At best, prejudices are oversimplifications. At worst, they reflect a narrow-minded view of the world. They are not likely to win the confidence or agreement of your readers.

Also (not from the book by Fowler & Ramsey)

Stereotypes – a probabilistic assumption about individuals based on their group membership

While not universally valid, they can be statistically accurate generalizations about how a group of people behaves. Unlike a belief, a stereotype is testable: it can be analyzed on the basis of facts.

Bayes’ theorem provides a framework for understanding how individuals might update their beliefs about groups (stereotypes) based on new evidence or data: One can combine prior beliefs with new data to create updated posterior beliefs, However, even with new evidence, stereotypes can be resistant to change because individuals may prioritize information that confirms their prior beliefs and disregard conflicting evidence.

Some research suggests that many stereotypes demonstrate a high degree of accuracy when empirically tested, often exceeding the average effect size in social psychology. This perspective acknowledges that while stereotypes may be associated with negative social consequences, it does not mean they are inherently inaccurate.

– Jussim, L. (2012). Social Perception and Social Reality: Why Accuracy Dominates Bias and Self-Fulfilling Prophecy. Oxford University Press.

– Jussim, L., Cain, T. R., Crawford, J. T., Harber, K. D., & Cohen, F. (2009). The unbearable accuracy of stereotypes. In T. D. Nelson (Ed.), Handbook of prejudice, stereotyping, and discrimination (pp. 199–227). Psychology Press.

– Ryan, C. S. (2002). Stereotype accuracy. European Review of Social Psychology, 12(1), 75–109. https://doi.org/10.1080/14792772143000029

A problem arises when probability-based assumptions are applied rigidly to individuals, leading to biased judgments and unfair treatment. https://pmc.ncbi.nlm.nih.gov/articles/PMC9337700/

__________________________________

Here are the classic Greek philosophers, who developed rationalist philosophy: a critical, systematic system – reasoned argument – to distinguish between facts, beliefs and opinions.

Pindar_Xenophanes_Anaxagoras_Socrates_Plato_Aristotle_800

February 6, 2018 5:47 pm

Is evolution a theory or a fact

February 6, 2018 5:43 pm

Is evolution a theory or a fact?

“evolution” has 2 different uses:
‘facts’ of evolution, and the ‘theory’ of evolution.

Here are observable facts

* Many forms of life that used to exist, no longer exist today.
(We’ve found many fossils; more are discovered every day)

* Many forms of life exist now, that did not exist in the past.
(Many modern animals and plants are obviously different from fossils)

* DNA exists.

* Every time an organism reproduces, random changes (mutations) in DNA happen. (We actually explicitly see these with gene-sequencing)

* Some mutations help an organism survive – those genes pass on to the next generation.
(We actually see organisms survive and reproduce. We can sequence the DNA of the parent and of the offspring. We literally see the genes.)

* Some mutations don’t help an organism survive; those genes die out.
(We actually see that some organisms die before they reproduce. Their genes literally die with them.)

* Millions of different DNA samples show a relationship between all forms of life.

* As time goes by, some genes become more common, some become less common. (This has been directly observed in bacteria, some plants and some animals)

Here is the theory that connect such facts

1. Organisms produce more offspring than can survive to adulthood and reproduce.

2. All organisms have random mutations.

3a. Mutations that allow an organism to survive are passed on to their offspring.

3b. Mutations that don’t allow an organism to survive die off.

4. So over time, some mutations become more common.

The “theory” of evolution is the relationship between observations (“facts.”)

In this sense, the theory is just as true as the theory of gravity, or the theory of electricity.

Resources

Evolution 101. Univ of California Museum of Paleontology

http://www.pbs.org/wgbh/nova/labs/lab/evolution/

https://lifeonearth.seas.harvard.edu/learning-activities/

How do we know what DNA looks like

January 30, 2018 4:34 pm

Question: How do we know what DNA and genes really look like?

We see images in books that look like this, but each individual atom is only a nanometer (1 x 10 ^-10 m) wide.

No visible light microscope can view objects made with such small pieces.

dna-notes-7-728

So the real way that we figured out the atom-by-atom structure of DNA is through a technique called X-ray crystallography.

Our molecule of interest – in this case, DNA – is concentrated and crystallized.

It is placed in front of an X-ray source.

The X-rays scatter off the DNA’s atoms. We capture this diffraction pattern on film (or on a digital X-ray detector.)

$Photo 51 DNA Diffraction pattern$

X-ray diffraction image of the double helix structure of the DNA molecule, taken 1952 by Raymond Gosling, commonly referred to as “Photo 51”, during work by Rosalind Franklin on the structure of DNA (text Wikipedia)

This diffraction pattern is beautiful but doesn’t directly look like the original molecule.

There is a mathematical relationship between the placement of the atoms, and where the atoms deflect – just like there is a relationship between hitting pool balls and how they deflect:

When you know how a pool table is set up, what balls are made of, and see how the balls move after being it, you could use math to work backwards to figure out where the balls originally where.

from Banks and Kicks in Pool and Billiards, Dr. Dave Alciatore, Billiards and Pool Principles, Techniques, Resources

The same is true here: We can use math to figure out where each individual atom in the DNA is! Let’s follow the steps below:

On the left, we see X-rays leave a source. Some of these x-rays pass through a lead screen.

The X-rays hit a crystallized DNA sample.

The X-rays bounce off of the molecules, like how pool balls bounce off of each other.

Some of the x-rays bounce onto a film plate. This makes an image.

We end up with a diffraction pattern on film.

How does one physically interpret diffraction patterns in DNA?

Figure 11.4, Purves’s Life: The Science of Biology, 7th Edition

Once we have a diffraction pattern, we then use math to work backwards, and figure out where the atoms must have been.

The result is an electron density map which almost exactly traces out the shape of the molecule.

X Ray crystallography and electron density map

Left image: X-ray diffraction pattern, Wikimedia. Right upper image: electron density map. Right lower image: model fitting atoms to the density map.

Can we image DNA more directly?

Yes. One can use a scanning tunneling microscope (STM).) It shows detail at the the atomic level. Along with the following image please read Livescience: DNA directly-photographed-for-first-time.html

DNA’s double-helix seen in electron microscope photograph. By Enzo Di Fabrizio, Magna Graecia University in Catanzaro, Italy.

Here is another STM image of DNA. You can see how closely it matches the model from X-ray crystallography.

STM image of DNA

External resources

Are there true pictures of the DNA molecule (not synthetic images), showing the double helix?

On DNA’s Anniversary: How Rosalind Franklin Missed the Helix

Sexism in science: did Watson and Crick really steal Rosalind Franklin’s data?.

The Big Dig

January 29, 2018 4:37 pm

What are we learning?

We’re studying the engineering – applied physics – used in Boston’s Big Dig. We’ll study the effect of changing forces, loads, materials and shapes, on a structure.

Why are we learning this?

To learn how to break a complex real-world problem – building safe tunnels and related structures – into smaller parts that can be solved using scientific/engineering principles.

To learn how to use a simple computer simulation to model such systems.

Vocabulary goals

compression, tension, bending, shear, torsion, loads, dead load, live load, settlement load, thermal load, wind load, earthquake load, dynamic load, arch, brace, buttress

Historical background

The Central Artery/Tunnel Project (CA/T) – the Big Dig – was a megaproject in Boston that rerouted the Central Artery of Interstate 93, the chief highway through the heart of the city, into the 3.5-mile (5.6 km) Thomas P. O’Neill Jr. Tunnel. It also included the construction of the Ted Williams Tunnel (extending Interstate 90 to Logan International Airport), the Zakim Bunker Hill Memorial Bridge over the Charles River, and the Rose Kennedy Greenway in the space vacated by the previous I-93 elevated roadway. Planning began in 1982; construction work was carried out between 1991 and 2006.

Intro adapted from Wikipedia, The Big Dig, 1/18

Photo gallery

Here are before-and-after photos of downtown Boston, showing the removal of the Central Artery and it’s replacement with the Rose Kennedy Greenway.

Left-click on it to open in a new window, at higher-resolution.

Our app Building Big: Forces & Engineering app (from PBS)

Use the worksheet assigned by the teacher.

Building the tunnel under Forth Point Channel

William Harris, in “How Tunnels Work: The Big Dig” (How Stuff Works) writes:

A few miles west, Interstate 90 enters another tunnel that carries the highway below South Boston. Just before the I-90/I-93 interchange, the tunnel encounters the Fort Point Channel, a 400-foot-wide body of water that provided some of the biggest challenges of the Big Dig.

Engineers couldn’t use the same steel-tube approach they employed on the Ted Williams Tunnel because there wasn’t enough room to float the long steel sections under bridges… Eventually, they decided to abandon the steel-tube concept altogether and go with concrete tunnel sections, the first use of this technique in the United States.

…workers first built an enormous dry dock on the South Boston side of the channel. Known as the casting basin, the dry dock measured 1,000 feet long, 300 feet wide and 60 feet deep — big enough to construct the six concrete sections that would make up the tunnel…

The completed sections were sealed watertight at either end. Then workers flooded the basin so they could float out the sections and position them over a trench dredged on the bottom of the channel.

[They couldn’t] simply lower concrete sections into the trench [because] of the MBTA’s Red Line subway tunnel, which runs just under the trench. The weight of the massive concrete sections would damage the older subway tunnel if nothing were done to protect it. So engineers decided to prop up the tunnel sections using 110 columns sunk into the bedrock. The columns distribute the weight of the tunnel and protect the Red Line subway, which continues to carry 1,000 passengers a day.

Apps

Slider photo: Boston before- and after- Big Dig (10 years later, did the Big Dig deliver?, Boston Globe)

Documentaries

Extreme Engineering: Boston’s Big Dig (2003)

https://vimeo.com/30626123

Tour of the Big Dig in Boston, Bob Vila

National Geographic MegaStructures Boston Big Dig Documentary 2016

https://www.youtube.com/watch?v=R2HHmWxGRMQ

Big Dig The Construction Story of Boston Big Dig

Underground Utility Protection

In “The Big Dig: Learning from a Mega Project”, Virginia Greiman writes

To protect against losses caused by the disruption and failure of underground utilities, a Big Dig utility program relocated 29 miles of gas, electric, telephone, sewer, water, and other utility lines maintained by thirty-one separate companies in 1996.

Some of this infrastructure was more than 150 years old; a complete lack of knowledge on the age, condition, and location of most of the utilities required submission of “as-built” drawings by all project contractors—drawings of existing conditions rather than planned or proposed construction.

The project had to deal with utilities that were shown on as-built drawings but never installed, and damage and flooding caused by underground sewer pipes not identified on the drawings.

Resources

Wikipedia.org: Big Dig

PBS: Great Projects – The Building of America

Archaeology of the Central Artery Project: Highway to the Past. Website + 58 page PDF book.

Big Dig: Massachusetts Historical Commission, Archaeological Exhibits Online

Learning Standards

2016 Massachusetts Curriculum Framework High School Technology/Engineering

HS-ETS1-1. Analyze a major global challenge to specify a design problem that can be improved. Determine necessary qualitative and quantitative criteria and constraints for solutions, including any requirements set by society.

HS-ETS1-2. Break a complex real-world problem into smaller, more manageable problems that each can be solved using scientific and engineering principles.

HS-ETS1-3. Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, aesthetics, and maintenance, as well as social, cultural, and environmental impacts.

HS-ETS1-4. Use a computer simulation to model the impact of a proposed solution to a complex real-world problem that has numerous criteria and constraints on the interactions within and between systems relevant to the problem.

HS-ETS1-5(MA). Plan a prototype or design solution using orthographic projections and isometric drawings, using proper scales and proportions.

HS-ETS1-6(MA). Document and present solutions that include specifications, performance results, successes and remaining issues, and limitations.

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Start here

The liver is a multifunction organ. Has these jobs:

Part of the digestive system

Detoxification

Stores energy

Produces cholesterol

Produces bile to break down fats

Liver produces bile, a detergent that breaks up fat into small particles.

Bile is stored in the gallbladder, and released when you are digesting a meal.

Here we see bile salts emulsifying a globule of fat.

Detoxification

“Almost all the blood in your body passes through the liver.”

“As blood passes through the liver, it breaks down substances, such as prescription or over-the-counter drugs, street drugs, alcohol, and caffeine.”

“Our bodies naturally produce some harmful (toxic) chemicals or poisons, and those are also broken down by the liver.”

“In this way the liver acts as a filter to clean your blood.”

Energy storage in glycogen

The liver takes excess sugars and links them together into a large molecule called glycogen.

Glycogen is stored until energy is needed.

Makes cholesterol

The liver makes cholesterol.

Contrary to popular belief, cholesterol is not bad for you: In fact, you’d instantly stop living if you didn’t have any in your body. All cell membranes in animals have some cholesterol as part of their structure. And many critical hormones are made by using cholesterol as a starting point.

The solution is not to make our bodies cholesterol-free; the solution is to change one’s diet to reduce the excess added cholesterol.

Cholesterol used to build bile

Cholesterol used to build hormones

Cholesterol used in all cell membranes

References

How does bile break up fat?

(adapted from Giancoli Physics)

Waves spread as they travel. When waves encounter an obstacle, they bend around it and pass into the region behind it. This phenomenon is called diffraction. The amount of diffraction depends on the λ (wavelength) of the wave and on the size of the obstacle:

(a) λ is much larger than the object. Wave bends around object almost as if it is not there.

(b) and (c) the λ is shorter than the size of the object. There’s more of a “shadow” region behind the obstacle where we might not expect the waves to penetrate — but they do, at least a little.

(d) the obstacle is the same as in part (c) but the λ is longer. More diffraction around object.

Rule: Only when λ is smaller than the size of the object will there be a shadow region.

Water waves diffracting around an island

Sound waves can diffract in unusual and unexpected ways. See our article on anomalous sounds

Even light itself can diffract! See our article on light’s wave nature.

Fresnel diffraction

French scientist, Augustin-Jean Fresnel,

Example – diffraction in Boston Harbor

As part of the Central Artery/Tunnel project – the Big Dig – Applied Coastal Research and Engineering did research on wave diffraction in Boston Harbor, around Spectacle Island.

Learning Standards

Here’s an actual news story: “Loud booms heard across Southern New Hampshire: Source of the noise still unclear.”

The answer? It’s complicated, but basically:

(a) there are a wide variety of ways that sounds are produced – including some bizarre ways that most people have never heard of

(b) Sound waves don’t always move in a straight path like many people imagine; changing temperature/density of the air can cause sound waves to bend and diffract, so:

(b1) sound can sometimes travel much further distances than one would expect

(b2) sound can come from a location very different from what “seems obvious” just by listening

(b3) local wind can mask sound, so the same loud sound might be heard in one neighborhood, yet be undetectable by people just a mile away.

Basic idea

Sound doesn’t move in a straight line: It spreads out radially, and then – because of a phenomenon known as diffraction – it can even bend around obstacles.

“If the air above the earth is warmer than that at the surface, sound will be bent back downward toward the surface by refraction.” – Hyperphysics

Normally, only sound initially directed toward the listener can be heard, but refraction can bend sound downward – effectively amplifying the sound.

This can occur over cool lakes.

Sounds also can bounce off of objects, and come to our ears from a direction different than the original source.

ABD Engineering writes:

…wind alters sound propagation by the mechanism of refraction; that is, wind bends sound waves. Wind nearer to the ground moves more slowly than wind at higher altitudes, due to surface characteristics such as hills, trees, and man-made structures that interfere with the wind.

This wind gradient, with faster wind at higher elevation and slower wind at lower elevation causes sound waves to bend downward when they are traveling to a location downwind of the source and to bend upward when traveling toward a location upwind of the source.

Waves bending downward means that a listener standing downwind of the source will hear louder noise levels than the listener standing upwind of the source.

In the evening, this temperature gradient will reverse, resulting in cooler temperatures near the ground. This condition, often referred to is a temperature inversion will cause sound to bend downward toward the ground and results in louder noise levels at the listener position.

Cheung Kai-chung, from Physics World (Hong Kong), (Translation by Janny Leung) offers this explanation

Sound wave will be refracted to the ground when traveling with the wind.

Sound wave will be refracted upwards when traveling against the wind.

Can wind mask even loud sounds?

Sound refraction due to cold air:

Also this “…if the air close to the ground is colder than the air above it then sound waves traveling upwards will be bent downwards. This is called Refraction. These refracted sound waves can act to amplify the sound to someone standing far away.”

Sound seems amplified when traveling over water.

In School-for-Champions we read

See their full lesson here School-for-champions.com: Sound_amplified_over_water

Can snow on the ground affect sound?

Related topic: The Hum is a phenomenon, or collection of phenomena, involving widespread reports of a persistent and invasive low-frequency humming, rumbling, or droning noise not audible to all people.

Human reactions to infrasound –

Skyquakes or mystery booms are unexplained reports of a phenomenon that sounds like a cannon or a sonic boom coming from the sky. They have been heard in several locations around the world. –

References

Learning Standards

Our school is right by Boston Harbor – learning about the sea is second nature to many of our staff. So we love to tie maritime history and science into our curriculum.

As you enter our school, you pass by a binnacle – what was it used for?

A binnacle is a waist-high case, found on the deck of a ship, that holds the compass.

It is mounted in gimbals to keep it level while the ship pitched and rolled.

It also has a mechanism to compensate for errors in detecting the Earth’s magnetic field.

Every ship’s captain would use one, for navigating in and out of Boston Harbor, and around the world.

Waves spread as they travel. When waves encounter an obstacle, they bend around it and pass into the region behind it. This phenomenon is called diffraction.
$Wave diffraction$
The amount of diffraction depends on the λ (wavelength) of the wave and on the size of the obstacle: