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Advantages of international collaboration in science
Wider source of funding, larger pool of experts, benefits of research shared widely across society, different perspectives
Confirmation bias
A type of cognitive bias that involves favoring information that confirms your previously existing beliefs or biases
Hypothesis
Explanatory statements about the natural world that could be true or false. Often suggest a causal relationship or a correlation between factors. Can be tested by experiments and observations
Law
A descriptive statement derived from observations of regular patterns of behavior. They are mathematical in form and can be used to calculate outcomes and make predictions. They cannot be proven nor do they necessarily explain why a phenomena occurs. Eg. Newton's Universal Law of Gravitation
Paradigm Shift
Fundamental change in the understanding of some part of the universe works due to better explanations, better evidence and better predictions
Post hoc, ergo propter hoc (false cause)
Refers to a logical fallacy that because two events occurred in succession, the former event caused the latter event ie. false cause
Scientific Method
There is no single process, however, they often involve hypotheses, experimentation, observations, repeated trials, interpretation of results, producing models drawing conclusions which often lead to more questions
What makes an idea scientific?
Must focus on the natural world, ideas must be testable/falsifiable, relies on evidence, can lead to ongoing research, benefits both the scientific and general community
What is science?
Science is both a body of knowledge and a process through which we understand the natural world
What causes a paradigm shift?
Scientists discover (significant) anomalies in the original paradigm which the new paradigm is able to explain, there is a large amount of evidence which supports the new paradigm over the old one, better predictions can be made and the 'old guard' of scientists simply die off
Theory
A scientific theory is a well substantiated explanation of some aspect of the natural world that is acquired through the scientific method and repeatedly tested and confirmed through observation and experimentation. Incorporates facts, laws and tested hypotheses, predictions can be made from theories
Occam's Razor
If there are two explanations which fit all the available evidence then the explanation with the least new assumptions is most likely to be correct
Quantitative data
Are measures of values or counts expressed as numbers (eg. how many, how much or how often)
Qualitative data
Are measures of which are not quantifiable in terms of numbers
Models
Models can be physical, conceptual or mathematical and are developed to explain processes that may not be observable. Mathematical models are used to make testable predictions, which can be especially useful when experimentation is not possible. Models tested against experiments or data from observations may prove inadequate, in which case they may be modified or replaced by new models
Observations
Obtaining knowledge either through through our senses (qualitative observation), or recording and collecting data using scientific tools and instruments (quantitative observation)
Fact
A basic statement established by experiment or observation
Belief
A statement that cannot be tested scientifically
Random errors
Have no pattern, they are unpredictable and can't be replicated by doing the experiment again. Readings can be both too large and too small. Random errors can be reduced by using an average measurement from a set of measurements, or increasing sample size
Systemic errors
Are generally consistent and repeatable errors. These errors are usually caused by measuring instruments that are incorrectly calibrated or are used incorrectly. The error is typically in the same direction (either always too large or too small). They are difficult to prevent because they are difficult to detect. To avoid these types of errors know the limitations of the equipment
Precise results
When the results which are used to calculate the average are very close together we say that the result is precise
Accurate results
When a measured value is very close to the accepted value then we say the the result is accurate
Uncertainty / Errors
Scientific uncertainty is a quantitative measurement of variability in the data. Uncertainty can be categorised in two ways: accuracy and precision
How has the growth in computing power made modelling more powerful?
Complex situations involving large amounts of data, a large number of variables with complex and lengthy calculations can be done quickly and cost effectively
Describe the different ways in which data can be obtained?
Data may be qualitative or quantitative. It can be obtained from observation, experimentation, remotely using electronic sensors
How does taking repeated measurements and having large numbers of readings improve the reliability of data collection?
Random errors can be reduced
How are models refined?
Through the collection of more data either from observation or experiments
What were some of the sources of errors encountered when comparing seismic data to mathematical data?
Accuracy of tools, issues of scale, misinterpretation of data, amount of data
Inductive reasoning
Down-Top. Starts with a very specific observation, from which conclusions are drawn to reach a broad generalisation
Deductive reasoning
Top-down. Starts with a general statement and examines the possibilities to reach a specific logical conclusion
Inductive reasoning and Deductive reasoning rely on premises. What is a premise?
A statement from which another statement or conclusion is inferred
Difference between cause and correlation (logical fallacy: post hoc ergo propter hoc)?
Correlation is a statistical link between two variables. To establish a causal relationship a significant amount of evidence as well as a scientific mechanism linking the factors is required
What does falsify mean?
To demonstrate that a statement, hypothesis or theory is false or incorrect
Independent variable
The experimental factor that is changed
Dependent variable
The variable which is measured
Control variable
A variable that is kept constant during an experiment
Peer review
A process which subjects the author's research to the scrutiny of others who are experts in the same field (peers) to ensure academic scientific quality BEFORE publication.
Scientists often work collaboratively, what are some of the advantages of this in a scientific context?
Double checking data and calculations, opportunity to debate and discuss conceptual understanding, efficiency
What is the current model of star creation?
Massive clouds of dust and gas coalesce under gravitational attraction, when the resulting extreme temperatures and pressures initiate the nuclear fusion of hydrogen.
How are brown dwarf stars formed?
If there is not enough gas, then it does not heat up enough to start fusion and it remains a brown dwarf.
How are planets formed?
Not all the gas in the cloud might be pulled into the star, some might be too far away and continue to circle it. This could eventually become planets, as in our solar system.
What are the main classes of stars?
Main sequence; red giants; blue giant; red super-giant; white dwarf; neutron star; black dwarf.
What is a Hertzsprung-Russell (HR) diagram?
A graph of star luminosity against temperature.
What are HR diagrams important?
Different classes of stars occupy different positions in the diagram.
What is a typical pattern of evolution of a star?
Most stars evolve from "main sequence" through red giants, white dwarves and neutron stars to form black holes, when their supply of hydrogen runs out.
What can happen to very massive stars?
Very massive stars undergo a catastrophic collapse known as a supernova.
What is a supernova?
A star that suddenly increases greatly in brightness (often brighter than all the other stars in the galaxy combined) because of a catastrophic explosion that ejects most of its mass.
Why are supernova's important in element formation?
As their formation would be endothermic, elements heavier than iron could not have been produced in main sequence or other kinds of stars and they are currently thought to result from extreme events such as supernovas. The dust from nova and supernova spreads throughout the universe and can eventually join with other dust to make new stars and planets - which contain the heavier elements made in the first star.
What element(s) are produced in main sequence stars?
Helium - from fusion of hydrogen atoms.
Where does the energy of a star come from?
Nuclear fusion (atoms fusing together to make heavier elements). The product atoms have slightly less mass than the atoms being fused together. This is converted into energy according to Einstein's equation E = mc2 .
How are element up to iron formed?
As stars run out of hydrogen they collapse and can start converting the helium into heavier elements.
How can the elements present in a star be determined?
From lines in their spectra - using a telescope and a diffraction grating. Each element produces a different pattern of lines.
What is dark matter?
An unknown substance which is believed to hold galaxies together, but doesn't emit any electromagnetic radiation. Its presence is required by current models of the universe.
What is 'dark energy'?
It is believed to be responsible for the accelerated expansion of the universe. It cannot be seen but is needed by current models of the universe.
How old is the universe?
Current models suggest about 13.8 billion years.
What is a light year?
The distance that light travels in one year.
What distinguishes a scientific account of the origin of the universe from creation myths?
Scientific claims must focus on the observational evidence and must be testable
What is Olber's paradox, and why is it important?
Olber realised that if the universe was infinite, the night sky should be infinitely bright. Therefore he concluded that the universe was not infinite.
What is the importance of Einstein's General Theory of Relativity to our understanding of the universe?
Relativity provides an explanation of Newton's Law of gravitation.
Who first detected the cosmic microwave background ratiation (CMBR)?
Penzias and Wilson in 1964 - by accident. They did not know what they had found.
Which model of the universe does not require it to have an origin?
The Steady-State model.
What was regarded as conclusive evidence of the Big Bang?
The detection of the CMBR in 1964 by Penzias and Wilson.
How have developments in computing speed helped our increase our understanding of the universe?
Present day astronomical observations generate vast amounts of data and rely on rapid computer processing to convert it into useful information. e.g. The first picture of a black hole was put together from 700TB of data collected by the Event Horizon Telescope.
Why is computer modelling important in examining theories of the universe?
Computer modelling of galaxy formation from the initial fluctuations in the density of the early universe as shown by COBE and WMAP satellite data help explain the appearance of the universe
Why are COBE and WMAP important?
They provided evidence of fluctuations in the CMBR, which in turn suggested that the early universe was not perfectly homogeneous. This allowed for matter to start to clump together ans so for star and galaxy formation.
What was the Big Bang?
About 13.8 billion years ago a cosmological event occurred that resulted in all of time, space, energy and eventually, matter being formed.
What was the Ptolemaic system?
An earth-centered (geocentric) view of the universe with the stars and planets orbiting the earth in spheres.
How was the motion of the planets a chalenge to the geocentric model?
The planets were noticed - and named - because they did not follow the rotation pattern of the fixed stars. Astronomers had to invent 'epicycles' - wheels within wheels -to try and explain why the planets had, at times, retrograde motion (they went backwards as well as forwards).
Why were improvements in technology important to the developing understanding of the solar system?
By eye, we can only see a few celestial objects - and not distinguish between the different types. Developments in telescopes allowed the discovery of moons around other planets, then other types of objects, and allowed far more accurate measuements of their movement and position.
What recent observations have suggested that other stars have planets surrounding them?
'Wobbles' in a star's motion and 'dips' in its brightness as a planet pass between the star and us. In 2008 scientists used an infra-red telescope to predict that a specific star had an exo-planet, then used the Hubble telescope to take a visible-light picture of the planet.
What was the contribution of Galileo to our understanding of the universe?
He developed telescope technology enough to see the moons of Jupiter - a challenge to the earth-centered system.
What was the contribution of Copernicus to our understanding of the universe?
He modeled the motion of the planets as circles around the earth - giving slightly incorrect positions. (A heliocentric model.)
What was the contribution of Brahe to our understanding of the universe?
He used measurements of a supernova to shown that (pace Aristotle) the celestial realm was not unchanging and 'perfect'. He used his measurements to posit a model where the planets moved around the sun, but the sun moved around the earth.
What was the contribution of Kepler to our understanding of the universe?
He improved the telescope and his more accurate measurement led to a modified Copernican system, where the planets (including the earth) moved around the sun in elliptical orbits - his 3 laws of planetary motion.
What was the contribution of Newton to our understanding of the universe?
His law of gravitation provides a mathematical basis for Keplers law and model - it mathematically models the change in velocity of the planets etc.
What was the contribution of Einstein to our understanding of the universe?
Models developed from his theory of relativity - based on the idea that space-time was curved - made predictions, which were confirmed by observation.
What is Hubble's constant?
It is the constant relating the speed of a galaxy away from us to its red shift, and so gives the expansion rate of our universe at present.
What is a 'red shift'?
When light rays moving away from us appear red, as the wavelength becomes stretched.
Who realised that there was more than one galaxy in the universe?
Hubble.
How are stars organised?
Stars are part of galaxies and galaxies are found in groups called 'clusters' (our 'local cluster' contains the Milky Way).
How have advances in observational technology enabled more detailed information to be obtained regarding the large scale structure of the universe.
Initially improvements in refracting telescopes, allowing more detail to be seen (e.g. moons of Jupiter). Then the development of large reflecting telescopes (e.g. the one Hubble used) allowing points of light that were previously thought of as individual stars to be seen as galaxies. Then telescopes using other parts of the electro-magnetic spectrum (e.g. the radio-telescope at Jodrell Bank) made bodies that do not emit in the visible spectrum become visible. In particular, it allowed the CMB to be discovered. Finally, the Hubble telescope (in space) where the earth's atmosphere does not absorb any 'light' has allowed billions of previously undiscovered galaxies to be seen. The most modern telescopes have shown that the CMB is not uniform and that the non-uniformity shows the Big Bang was not uniform - hence stars, galaxies, clusters could form.
What are Cepheid Variables and why are they important?
They are objects which pulse in a predictable way, and whose absolute luminosity is related to the time they take to pulse. Using values from these stellar 'candles' (Cepheid variables) to estimate how far away stellar objects were, Hubble linked their distance from us with the speed with which they were moving away.
This allowed Hubble to see that some objects were further away from us than the edge of our galaxy.
How did Hubble work out that there was more than one galaxy in the universe?
Using stellar candles to estimate distance, Hubble was the first to see that some objects were further away from us than the edge of our galaxy.
Is Hubble's constant constant?
The value of Hubble's constant depends on the wavelength of light used to calculate it. Measurements from space telescopes suggest that the rate of expansion is increasing (dark energy) and that Hubble's constant is changing - and has changed over time.
Why was the first estimates of the age of the earth problematic for evolution?
They did not leave enough time for evoution through natural selection to have occurred.
How has our estimate of the age of the universe changed in the last century?
The first estimate of Hubble's constant (which links the speed of expansion to distance) gave a very low estimate for the age of the universe. Developments in telescope technology (including X-ray telescopes) have lowered the agreed range for the value of Hubble's constant, which has increased the estimate of the age of the universe to about 13.8 billion years.
Why was the discovery of an expanding universe important to our understanding of cosmology?
If the universe was expanding, Hubble reasoned that at some time it must have been all at a single point. Measuring the rate of expansion allowed him to estimate the age of the universe.
What is the bais of the Steady State model of the universe?
Universe has always existed
As the Universe expands, new matter is created
What was the initial evidence for the Big Bang?
Doppler effect
Majority of galaxies seem to be racing away from us (red shift) and faster the further away they are.
At what elements do stars stop nuclear fusion?
At elements heavier than iron because the process is endothermic. Iron is the most stable nucleus.
What is the age of the earth?
At least 4.6 billion years.
What is the evidence for the age of the earth?
Quantitative data derived from radioactive emissions from meteorites found on the Earth and the moon.
What is the importance of studying the composition of meteorites and comets?
Models suggest that they were created at the same time as the earth and from the same material.
How was the solar system formed?
Scientists believe that the solar system was formed when a cloud of gas and dust in space was disturbed, maybe by the explosion of a nearby star (called a supernova). This explosion made waves in space which squeezed the cloud of gas and dust.
What techniques are used to study the interior of the earth?
It cannot be studied directly. Analysis of the veocity and refraction of seismic waves at different parts of the earth from the same source - S and P waves. Geometric and gravity measurements.
What are the two type of technique for dating rocks?
Relative and absolute dating.
What is involved in relative dating of rocks?
The assumption that lower layers of rock are older than upper layers.
What is involved in absolute dating of rocks?
Measurement of radioactive decay of LONG-LIVED isotopes. Relative aboundance of different isotopes of e.g. lead. Dating the age of fossils in rock.
Why are very old rocks scarce?
The earth's crust is constantly changing and they can be too deep in the earth's crust. The earth was only partially solid in its early stages If near the surface they may have eroded away.
What is the dating of rocks important?
Rock composition provides evidence for the earth's origin and the changes that it has undergons since formation.
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