Recently, as part of an ongoing effort to playfully engage the public in science, he chatted with DISCOVER contributor Darlene Cavalier (who moonlights as the Science Cheerleader) and shared his thoughts on the Large Hadron Collider, spiral galaxies, ROS suppression, and more.
Ecosystem is a term that refers to all of the living things in a specific area, together with the material surroundings. Plants and animals within as ecosystem often depend on each other in complex ways, so that it is not usually possible to change one part of the system without changing other parts as well. Study of the records of past ecosystems shows that both the kinds of plants and animals associated with it and the kinds of relationships between them change over time, so we should not think of ecosystems as rigid and unchanging, nor assume that any change in an ecosystem must be for the worst.
Lesson #17 of 18 in the Brain Makeover collaboration with Professor James Trefil/George Mason University, the 76ers Cheerleaders and the Science Cheerleader. See Brain Makeover Series.
17. All forms of life evolved by natural selection.
Scientists divide the development of life on Earth into two segments: chemical evolution, which involves the development of life from inorganic materials, and evolution by natural selection, which describes the process by which that early life form produced the diversity of modern life. The latter is what people associate with Charles Darwin and usually mean by the term ‘evolution’.
Evolution by natural selection depends on two things: first, that there are variations within populations (so that, for example, some rabbits can run faster than others) and, second, competition between individuals (so that fast rabbits are more likely to survive and reproduce). Over time, this selection process produces new species.
Evidence for evolution by natural selection comes from the fossil record and from the examination of genes in the DNA of modern life forms.
Lesson #15 of 18 in the Brain Makeover collaboration with Professor James Trefil/George Mason University, the 76ers Cheerleaders and the Science Cheerleader. See Brain Makeover Series.
All living things are made from cells, the chemical factories of life.
One of the most important discoveries of nineteenth century science was that life is based on chemical reactions, and that these reactions take place in complex structures called cells. In the twentieth century we learned that the instructions for carrying that chemistry are carried in DNA.
The best analogy for a cell is a complex factory—think of a big refinery. There is a front office where instructions for carrying out the factory’s activities are kept. DNA in the nucleus of cells plays this role. In a factory there is a place where energy is generated. In cells, this happens when complex molecules are combined with oxygen in organelles called mitochondria. There is a wall that separates the factory from its surroundings, and in a cell there is a flexible cell membrane that carries out this function. There must also be a way for material to enter and leave the factory, a function that in the cell is the job of large protein molecules called receptors in the cell membrane. The shape of these membranes matches that of molecules outside the cell.
The chemical reactions in a cell are run by protein molecules that serve as enzymes, and the information for building those molecules is coded in stretches of DNA called genes. Understanding how genes operate remains a major area of research in the sciences.
Lesson #13 of 18 in the Brain Makeover collaboration with Professor James Trefil/GMU, the 76ers Cheerleaders and the Science Cheerleader. See Brain Makeover Series.
The surface of the earth is constantly changing.
The Earth can be thought of as being separated into three layers. The core, at the center, consists of heavy materials like iron and nickel. At the very center the core is solid, but farther out it is liquid. The next layer is the mantle, composed of heavy minerals, and the outermost layer is the crust. The surface of the Earth is separated into tectonic plates, some 30-50 miles thick. These plates move around in response to convection in the Earth’s mantle. The continent are the uppermost layer of the tectonic plates. The constant motion of the plates causes a constant change in the surface features of the planet. Only the Earth among planets in the solar system has this kind of variability in its surface.
Where plates are moving away from each other, hot magma from the mantle comes to the surface to form mountain chains and deep sea vents. Where plates are moving together, one plate will slip beneath the other, forming mountain chains or deep ocean trenches, depending on whether or not there is a continent on the plate. If plates slide by each, as they do in the San Andreas Fault, their motion will cause frequent earthquakes.
The primary parts of the nucleus of the atom are the positively charged proton and the electrically neutral neutron. During the twentieth century it was discovered that there are literally hundreds of other particles—all unstable—that take part in various interaction at the atomic level. These can be divided into two major classes: there are hadrons that exist inside the nucleus and participate in the strong interaction, and leptons that do not. Protons and neutrons are both hadrons, while the electron is an example of a lepton. One way of thinking about atoms, then, is to say that their nuclei are made of hadrons, while leptons (electrons) in orbit complete the structure.
More recently, it was realized that all of the hundreds of hadrons can be understood as different combination of particles more fundamental still—particles called quarks. In this scheme, then, the quarks make up the hadrons that constitute the nucleus, while the leptons in orbit complete the atoms that make up all matter.
#8. Nuclear Energy Comes from the Conversion of Mass.
The nucleus of the atom is a dense collection of particles that carries most of the mass of the atom. In nuclear reactions, some of this mass may be converted to energy via Einstein’s famous equation E=mc2 . The chemical identity of the atom depends on the number of positively charged protons in the nucleus, but the nucleus can have different numbers of uncharged neutrons. Nuclei with the same number of protons but different numbers of neutrons are called isotopes of each other.
Most isotopes are unstable, and undergo a process of disintegration known as radioactive decay. The time it takes for half of a group of nuclei to decay is called the half life. Half lives can range from fractions of a second to billions of years. Measuring the number of decays that have occurred in a material allows us to estimate the age of the material.
The decay process can proceed by the emission of alpha particles (two protons and two neutrons), beta particles (fast electrons produced in the nucleus) or gamma rays (high energy electromagnetic radiation).
Energy can be derived from nuclei by fusion (the coming together of small nuclei to form larger ones) or fission (the splitting of large nuclei into smaller ones). In the case where the mass of the final products is less than that of the initial nuclei, the difference is converted into energy as outlined above. Fission energy supplies and appreciable fraction of American electricity, while fusion energy is what powers the sun.
#7. The Way a Material Behaves Depends on how its Atoms are Arranged.
Professor James Trefil (author of Science Matters, Why Science?, and 30 other books on science literacy) identified 18 key science concepts every adult should know to be a science literate. We’re here to reintroduce adults to science, in a fun way! It’s all part of our Brain Makeover project to increase adult science literacy. Here’s concept #4, presented by 76ers Cheerleader Lauren and explained by Professor James Trefil. We’ll post one each week (more or less) and it to the Brain Makeover collection.
The properties of a material depend on the type of bond holding atoms together as well as the arrangement of those atoms. For example, ionic bonds are often found in materials like minerals and ceramics, covalent bonds in the molecules of living systems, and metallic bonds (as the name implies) in metals. The difference between diamond and graphite—both made completely of carbon atoms–depends on the fact that in a diamond those atoms are arranged in a way that all the bonds of covalent, while in graphite some of the bonds are weaker, depending on polarization forces.
The electrical properties of materials depend on how strongly electrons are locked into their bonds. In a metal, for example, electrons are free to respond to outside forces. Such a material is called a conductor, because it allows electrical current to flow. In a plastic or ceramic, on the other hand, electrons are locked tightly into covalent or ionic binds and are not free to move. Such materials are called insulators.
In the twentieth century two other kinds of materials were discovered. Superconductors are materials through which electrical current can flow forever without loss. Normally, materials are superconducting only at low temperatures. Superconducting magnets are used extensively in MRI machines.
Semiconductors (like silicon) are materials in which electrons are occasionally shaken loose from covalent bonds, and so are available to carry electrical current. Two layers of semiconductors are the basic for solar photovoltaeic cells, in which sunlight shakes loose electrons to create electrical current. A transistor is a triple layer of semiconducting materials and is the basis of modern computers.
Brain Makeover #6: Atoms are Bound by Electron Glue.
Professor James Trefil (author of Science Matters, Why Science?, and 30 other books on science literacy) identified 18 key science concepts every adult should know to be a science literate. We’re here to reintroduce adults to science, in a fun way! It’s all part of our Brain Makeover project to increase adult science literacy. Here’s concept #4, presented by 76ers Cheerleader Lauren and explained by Professor James Trefil. We’ll post one each week (more or less) and it to the Brain Makeover collection.
Here’s Profession Trefil on Big Idea #6: Atoms are Bound by Electron Glue.
Most of the materials we encounter in our everyday life are compounds, made by putting different combinations of atoms together. The “glue” that holds these molecular together is supplied by the outermost electrons in the atom—chemists call them valence electrons”. There are basically three ways that valence electrons can interact to produce a bind between atoms.
1) One atom can transfer an electron permanently to another. This is called an ‘ionic’ bond.
2) Two atoms can share a pair of electrons—think of the electrons shuttling back and forth between the atoms. This is called a ‘covalent’ bond.
3) Each atom can give up an electron which is then shared by all the atoms in the material. This is called a ‘metallic’ bond.
In addition, bonds can form when the electrons in a neutral atom tend to cluster in one area, given that a negative charge and leaving other areas with a positive charge.
Big Idea #5: Everything Comes in Discrete Units and You Can’t Measure Anything Without Changing It.
Professor James Trefil (author of Science Matters, Why Science?, and 30 other books on science literacy) identified 18 key science concepts every adult should know to be a science literate. We’re here to reintroduce adults to science, in a fun way! It’s all part of our Brain Makeover project to increase adult science literacy. Here’s concept #4, presented by 76ers Cheerleader Lauren and explained by Professor James Trefil. We’ll post one each week (more or less) and it to the Brain Makeover collection.
Here’s Professor Trefil with Big Idea #5: Everything Comes in Discrete Units and You Can’t Measure Anything Without Changing It.
In our everyday world matter seems to be smooth and continuous, but in the world of the atom things are different. There everything—mass, energy, spin, and so on—comes in discrete bundles called quanta. (The word is from the Latin for ‘bundle’.) The branch of science that describes this world is called “quantum mechanics,” and it differs in fundamental ways from the laws that describe familiar objects.
The main difference comes from the fact that when you want to detect a quantum (an electron, for example), the only way you can do it is to bounce another quantum off of it, and this interaction will change the object being measured. The mathematical statement of this effect is called the Heisenberg Uncertainty Principle, and it tells us that there are certain things we cannot know about quantum systems. We cannot, for example, know exactly where an electron is and how fast it is moving at the same time. Because of the Uncertainty Principle, objects in the quantum world are described in terms of probabilities, and the totality of probabilities describing a given object is called its wave function.
Recently, scientists working in quantum mechanics have been investigating a phenomenon known as entanglement. The wave function of two particles that have interacted at some point in the past never really separate from each other, so that the particles can continue to influence each other even though no signals can pass between them. Entanglement is expected to form the basis for new technologies, including secure communication systems and quantum computers.
