Image library - Understanding Science (original) (raw)
Found 181 images:
DNA symmetry II
Watson and Crick realize that since DNA crystals could be flipped upside down and backwards, and still look the same.
Deuterium
A hydrogen atom has only a single proton in its nucleus, whereas deuterium, a rarer isotope of hydrogen, has a proton and a neutron.
Extinctions
Percentage of organisms that have gone extinct over the past 200 million years, based on the fossil record.
Even theories change (4 of 4)
General relativity seems up for a change. For example, it doesn't mesh with what we know about the interactions between extremely tiny particles. Will physicists develop a new theory that…
Even theories change (1 of 4)
Science is always a work in progress and even theories change. For example, in the 1600s classical mechanics was the accepted explanation of the movement of objects both in space…
Hypothesis of ozone depletion
Molina and Rowland's over-arching hypothesis (that releasing CFCs into the atmosphere would cause significant ozone depletion) was based on many supporting hypotheses, backed by their own lines of evidence.
How the base pairs match up
Students are given six knowledge statements and asked to rank them according to how scientific they feel the statements are. A group discussion ensues. This activity is adapted from Scharmann…
Image B 51
Franklin and Gosling's image confirmed the idea that DNA was helical in shape and that its bases were stacked pancake-style.
Peer review
Peer review of a scientific study submitted for publication provides assurance that someone who knows what they're doing has double-checked it.
Ozone fluctuation
Ozone levels fluctuate so widely that it is difficult to detect subtle trends over a short-term period, as shown by these ozone measurements for the atmosphere over Switzerland taken between…
Nuclear vs. mitochondrial DNA
Unlike nuclear DNA (left), mitochondrial DNA is only inherited from the maternal lineage (right) - a quirk which allowed Margulis to determine whether mitochondrial DNA encoded unique traits.
Magnetic flip-flops
As new seafloor forms, the igneous rock records the current state of the Earth's magnetic field. Sedimentary rock layers forming at the bottom of the ocean may also record these…
Untangling media messages
Media representations of science and science-related policy are essential for quickly communicating scientific messages to the broad public; however, some important parts of the scientific message can easily get lost…
Thymine and guanine
The visiting American chemist, Jerry Donohue, provided a key piece of evidence when he revealed that the forms given for thymine and guanine in most textbooks were wrong. Note the…
The supernova hypothesis
An existing hypothesis proposed that a supernova at the end of the Cretaceous had caused the extinction of dinosaurs. Supernovas throw off heavy elements like iridium - so the hypothesis…
Testing the supernova hypothesis
To further test the supernova hypothesis:If a supernova had occurred, it would have also released plutonium-244 as well as iridium. Original tests looked positive but replicating the analysis showed that…
Testing scientific ideas
Scientific testing occurs in two logical steps: (1) if the idea is correct, what would we expect to see, and (2) does that expectation match what we actually observe? Ideas…
Testing an idea (3 of 3)
When the entrance to the reward tunnel was blocked, most of the rats picked a tunnel that led in the direction of the food, supporting the idea that rats navigate…
Testing an idea (2 of 3)
Tolman and his colleagues trained rats in a maze which offered them many different tunnels to enter first. One of the tunnels twisted and turned but consistently led to the…
Testing an idea (1 of 3)
Psychologist Edward Tolman wanted to know how rats successfully navigate their surroundings - for example, a maze containing a hidden reward. Would they build mental maps of the maze as…
Rutherford’s argument (1 of 2)
In the early 1900s, Ernest Rutherford and his colleagues performed this experiment to test the hypothesis that an atom's mass and positive charge are spread diffusely throughout the atom and…
Testable ideas
A scientific idea may require a lot of reasoning to work out an appropriate test, but to be scientific, an idea must be testable.
Summing up scientific arguments
Scientific arguments are formed by figuring out what we would expect to observe if a particular idea were true and then checking those expectations against what we actually observe. A…
Revisiting Mendel
Gregor Mendel (left) showed that if you know the genotypes of the parents in a cross, you can predict the ratios of different offspring genotypes (right).
Building a scientific argument – cartoon 1
Scientific arguments involve three components: the idea (a hypothesis or theory), the expectations generated by that idea (frequently called predictions), and the actual observations relevant to those expectations (the evidence).
Behaving scientifically
Science is open to anyone and benefits tremendously from the expanding diversity of perspectives. However, science only works because the people involved with it behave "scientifically."
