Natural Science

Science tries to explain and understand the natural world, science works with testable ideas, and science relies on

evidence.

Compare the checklist to a prototypical case of science in action: Ernest Rutherford's investigation into the structure of the atom.

RUTHERFORD AND THE ATOMIn the early 1900s, Ernest Rutherford studied (among other things) the organization of the atom — the fundamental particle of the natural world.

RUTHERFORD AND THE ATOMThough atoms cannot be seen with the naked eye, they can be studied with the tools of science since they are part of the natural world.

We will use Rutherford's story to examine each item on the Science Checklist.

•See if Rutherford gets a tick in the “explain and understand” box.

RUTHERFORD AND THE ATOMErnest Rutherford's investigations were aimed at understanding a small, but illuminating, corner of the natural world: the atom.

He investigated this world using alpha particles, which are helium atoms stripped of their electrons.

Here is a picture of a helium atom.

But scientists didn’t know about this atomic structure at the time of Rutherford.

They just knew that small, positive charged particles flew out of radioactive substances.

Rutherford had found that when a beam of these tiny, positively-charged alpha particles is fired through gold foil, the particles don't stay on a straight line course, but are deflected (or "scattered") at different angles.

Rutherford wanted to figure out what this might tell him about the layout of an atom.

Let’s see the video

Science works with testable ideas.Only testable ideas are within the scope of science.

For an idea to be testable, it must logically generate specific expectations — in other words, a set of observations that we could expect to make if the idea were true and a set of observations that would be inconsistent with the idea and lead you to believe that it is not true.

Eg. the idea that a sparrow's song is genetically encoded and is unaffected by the environment in which it is raised, in comparison to the idea that a sparrow learns the song it hears as a baby.

Logical reasoning →

If the sparrow's song is genetically encoded, then a sparrow raised in the nest of a different species would grow up to sing a sparrow song like any other member of its own species. But if, instead, the sparrow's song were learned as a chick, then raising a sparrow in the nest of another species should produce a sparrow that sings a non-sparrow song. Because they generate different expected observations, these ideas are testable.

Logical reasoning →

If the sparrow's song is genetically encoded, then a sparrow raised in the nest of a different species would grow up to sing a sparrow song like any other member of its own species.

But if, instead, the sparrow's song were learned as a chick, then raising a sparrow in the nest of another species should produce a sparrow that sings a non-sparrow song.

Because they generate different expected observations, these ideas are testable.

Vocal LearnersTrue songbirds of the Oscine suborder of

Passeriformes, such as canaries, finches, sparrows and thrushes, are vocal learners that learn to sing by listening to adult birds of the same species. If young birds of these species are removed from members of their own species, they will still vocalize and produce songs, but the songs do not follow the normal species-specific patterns.

Read more: How Do Birds Learn to Sing? | eHow.com http://www.ehow.com/about_6729061_do-birds-learn-sing_.html#ixzz26e31Fplt

Inherited Vocal AbilitySome species of birds, including flycatchers, are born

with the species-specific song patterns genetically encoded in each individual bird's make-up.

Attempts to confuse young Alder flycatchers into learning the songs of another flycatcher species failed. Researchers played recordings of Willow flycatchers to 10-day-old Alder flycatchers that had been removed from the nest. The youngsters still sang the song of their own species. Experiments involving this bird group--the suboscines--demonstrates the inherent ability to produce the correct song even when raised away from their own species.

Stages of LearningSome songbirds, such as canaries and starlings, are

called open learners. They have the ability to learn new songs even after reaching adulthood. However, most juvenile songbirds learn to sing in two phases, with the sensitive--or critical--period being the time when they memorize new songs by listening to the adult males of their species. Once this period has passed and the birds enter the second learning phase, they begin to practice what they previously memorized. The two phases vary in length depending upon species.

DialectsBirds of the same species but living in different

geographical regions sing similar songs, but often produce distinct dialectic variations. Young birds learn to sing in these dialects, much like human babies learn dialects by listening to the accents of the adults around them.

Vocal OrgansBirds possess a unique vocal organ called the

syrinx, which allows them to produce a myriad of musical notes. However, unlike human beings who have only one voice box, songbirds have two voice boxes. This set-up gives them the ability to produce two different notes at once, with each syrinx sounding at the same time. By practising what they hear, baby birds learn to produce the proper sounds from these organs.

A scientific idea may require a lot of reasoning to work out an appropriate test, may be difficult to test, may require the development of new technological tools to test, or may require one to make independently testable assumptions to test — but to be scientific, an idea must be testable, somehow, someway.

assumptionIn science, an auxiliary hypothesis that is taken as true for the purposes of interpreting a particular test. All tests involve making assumptions. If an assumption of a test turns out to be inaccurate, it can cause the test results to be incorrectly interpreted. However, assumptions can be independently tested to help establish their accuracy.

• See if Rutherford gets a tick in the testable box.

Before 1910, Ernest Rutherford and many other scientists had the idea that the positive charge and the mass of an atom were evenly distributed throughout the whole atom, with electrons scattered throughout. You can imagine this model of the atom as a loosely packed snowball (the positive mass of the atom) with a few tiny grains of sand (the electrons) scattered throughout.

The plum pudding model of the atom by J. J. Thomson, who discovered the electron in 1897, was proposed in 1904 before the discovery of the atomic nucleus in order to add the electron to the atomic model. In this model, the atom is composed of electrons surrounded by a soup of positive charge to balance the electrons' negative charges, like negatively charged "plums" surrounded by positively charged "pudding". Instead of a soup, the atom was also sometimes said to have had a "cloud" of positive charge.

modelIn science, the term model can mean several different things (e.g., an idea about how something works or a physical model of a system that can be used for testing or demonstrative purposes). However, as a research method, modeling often means creating a mathematical model — a set of equations that indirectly represents a real system. These equations are based on relevant information about the system and on sets of hypotheses about how the system works.

model (cont..)Given a set of parameters, a model can generate expectations about how the system will behave in a particular situation. A model and the hypotheses it is based upon are supported when the model generates expectations that match the behavior of its real-world counterpart. Modeling often involves idealizing the system in some way — leaving some aspects of the real system out of the model in order to isolate particular factors or to make the model easier to work with computationally.

The idea that atoms are arranged in this way can be tested by firing an alpha particle beam through a piece of gold foil. If the idea were correct, then the positive mass in the gold foil would be relatively diffuse (the loosely packed snow) and would allow the alpha particles to pass through the foil with only minor scattering.

Science relies on evidence

Scientific ideas must not only be testable, but must actually be tested — preferably with many different lines of evidence by many different people. This characteristic is at the heart of all science. Scientists actively seek evidence to test their ideas.

Performing such tests is very important to science because the acceptance or rejection of a scientific idea depends upon the evidence relevant to it. In science, ideas that are not supported by evidence are ultimately rejected. They are not supported on the basis of dogma, popular opinion, or tradition.

• See if Rutherford gets a tick in the evidence box.

Ernest Rutherford's lab tested the idea that an atom's positive mass is spread out diffusely by firing an alpha particle beam through a piece of gold foil, but the evidence resulting from that experiment was a complete surprise.

Most of the alpha particles passed through the gold foil without changing direction much as expected, but some of the alpha particles came bouncing back in the opposite direction, as though they had struck something dense and solid in the gold foil.

Most of the alpha particles passed through the gold foil without changing If the gold atoms were really like loosely packed snowballs, all of the alpha particles should have passed through the foil, but they did not!

From this evidence, Rutherford concluded that their snowball model of the atom had been incorrect, even though it was popular with many other scientists. Instead, the evidence suggested that an atom is mostly empty space and that its positive charge is concentrated in a dense mass at its core, forming a nucleus.

When the positively charged alpha particles were fired at the gold foil, most of them passed through the empty space of the gold atoms with little deflection, but a few of them ran into the dense, positively charged nucleus of a gold atom and were repelled straight back (like what would happen if you tried to make the north poles of two strong magnets touch).

The idea that atoms have positively charged nuclei was also testable. Many independent experiments were performed by other researchers to see if the idea fit with other experimental results.

experimentA scientific test that involves manipulating some factor or factors in a system in order to see how those changes affect the outcome or behavior of the system. Experiments are important in science, but they are not the only way to test scientific ideas.