History of the Universe

1. History of the Universe

2. Topics • The Big Bang: origin of the Universe • What is science and the scientific method? • Origin of the Elements • What is an element and what determines which element an atom is? • Origin of the Solar System and Planet Earth • Radioactive dating • Hadean Age

3. The Big Bang • The beginning of the scientific view of the Universe: we have no evidence for what (if anything) happened before this. • About 14 billion years ago • The Big Bang: All of a sudden, all the matter and energy present in today's Universe appeared as a single very hot and dense point. • Some evidence: We can detect the radiation from this explosion as cosmic background microwaves. The heat of the explosion has cooled down, leaving these radio waves behind. • It expanded rapidly, and continues to expand even now. • “Red shift”: just like a train whistle drops in pitch (wavelength gets longer) when the train is moving away from us, light from distant stars is at longer wavelengths (it’s redder). This implies they are moving away from us, and the further away they are, the faster they are moving away. • Matter and energy condensed out of this, going on to form stars and other things. • Matter and energy are the same thing, in different forms. That's what Einstein meant by E = mc2.

4. Why Study Science? • We humans are naturally curious: we want to understand how the world works, why things happen. • This is the really big thing that separates us from the animals. • Science is a method for understanding the physical world, and science has proven to be very successful. • The models generated by the science give us the ability to predict and control many events. • Which leads to technology: all the gadgets and ideas and methods that we use every day all the time. • Our technology very clearly has given us longer, healthier, and more comfortable lives, and it has caused our species to vastly increase in number and spread throughout the world. • And that, in my opinion, is why we study science.

5. What is Science? • It’s a belief: that the physical world is governed by a set of unchanging, cause-and-effect laws that we can discover through careful observation. • Not affected by your mental, emotional, moral, or spiritual state • Not affected by other beings with free will (gods, spirits, etc.) • Results are reproducible by anyone : scientists delude themselves (and occasionally commit fraud); reproduciblity is a check. • It’s a public activity: a body of knowledge accessible to anyone. Scientists are expected to publish their results for others to criticize, re-test, build upon. • Does science explain everything? I doubt it. But, it explains the physical world very well. • Doesn’t have much to say about morality or beauty or how you should live for life.

6. Sorting Out False Beliefs • Scientific method: a way of sorting true ideas from false ones. • Superstition: the untested belief that actions not logically connected to an event can influence its outcome. Rabbit’s foot, your lucky shirt. Story about the rats with a ten second delay between pressing the lever and getting the food pellet…..nose in each corner, backflips. • The point is, the scientific method is used to eliminate superstitious beliefs.

7. The Scientific Method • How to investigate phenomena in an objective and rational manner. • 1. Make some careful observations about some phenomenon you are interested in. • 2. Formulate a hypothesis (an educated guess) that explain the phenomenon in light of previous knowledge. • 3. Come up with some testable predictions derived from the hypothesis. • 4. Test the predictions through experiments. • 5. Revise your hypothesis based on the results of the experiments. • 6. Repeat steps 3-5 until you are satisfied you have a good explanation for your phenomenon. • 7. Publish your results so others can learn about them.

8. An Example: Shaving Eyebrows • If you shave your eyebrows (etc.), does the new hair come in coarser than the original? Is this true? The idea is clearly based on someone’s observations. • Hypothesis: if your shave your eyebrows, the new hair will be coarser than the old hair was. • In addition to the main hypothesis, sometimes a null hypothesis is used: a negative statement saying that there is no relationship between two things. Here: the new hair looks and feels the same as the old hair. • Experiment: shave one eyebrow, let it regrow, then get several observers to guess which is which. • The unshaved eyebrow is a control: it does not get the experimental treatment, but is otherwise treated identically to the experimental group.

9. More Example • A double blind experiment: If the experimenter knows who is getting the real treatment and who is getting the placebo, the subject can often (subconsciously) pick up cues and respond accordingly. • In a double blind experiment, neither the patient nor the doctor administering treatment knows who is getting the experimental treatment and who is getting the placebo (the control). • Here, neither the scientists nor the people who judge the eyebrows should not know the experimental subjects, and which eyebrow was shaved should be random. • Results: six months after shaving one eyebrow, the observers did no better than random in guessing which one had been shaved. • Revision: If you still think there might be something to the original idea, you could try legs, or people with different natural skin or hair color or hair thickness, or different ages of people. • But at some point, you need to give up ideas that have not proved to be correct, and do something else!

10. Formation of the Elements • First, what is an element? A substance that can’t be broken down by chemical methods. • More precisely: A substance consisting of atoms that all have the same number of protons. • Atoms are composed of protons, neutrons, and electrons. Protons reside in the nucleus. The number of protons determines which element it is: 1 proton = hydrogen, 2 protons = helium, 6 protons = carbon, 57 protons = iron, 92 protons = uranium, etc. • There are 92 naturally occurring elements, plus other, heavier ones created artificially. • Changing the number of protons in the nucleus can only be done at very high energies: these are nuclear reactions and they involve radiation. • Living things do lots of chemistry (movement of electrons) but they don’t alter the atomic nuclei. In biology, the atoms always stay the same.

11. Where the Elements Come From? • Initially all matter is hydrogen and helium (the two lightest elements). • Even now, these two make up 98% of the mass of the Solar System. • Stars produce their energy by fusing hydrogen into helium, a process that converts some of hydrogen's mass into energy. • However, other nuclear reactions inside stars produce heavier elements: carbon, oxygen, nitrogen, all the way up to iron (57 protons). • These reactions produce energy, but they require higher temperatures and pressures to start. • Oxygen and carbon are the third and fourth most abundant elements in the Universe. • Heavier elements can only be synthesized inside supernovas. • Supernovas occur when a star runs out of fuel. Gravity then collapses the star so much that new nuclear reactions occur, which blows up the star. • Radiation from nearby supernovas is a possible cause of some mass extinctions. The Crab Nebula, the remains of a supernova

12. Formation of the Solar System • About 4.6 billion years ago • that is, about 1/3 of the time the Universe has existed • Based on the radioactive dating of rocks, mostly from the Moon and meteorites • A large rotating mass of gas and dust slowly accretes under the influence of gravity • This idea came from Emanuel Swedenborg in 1734. He was both a scientist and a Christian mystic whose ideas came from dreams and visions. • Most of it forms the Sun at the center, with smaller bits forming the planets and large amounts of debris. • Gravity compresses the inner layers of the Sun enough to start fusion of hydrogen: the Sun starts shining. Swedenborg

13. Radioactive Dating • Atoms that have too many neutrons in the nucleus are unstable. They decay into other atoms, accompanied by radiation. • The rate of decay (the half-life) is constant: it isn’t affected by temperature, pressure, the chemical state of the atom, or anything outside the nucleus (except for extreme conditions like the interiors of stars). • So, if you start with a pure radioactive element, you can tell how long it has been since the element formed by seeing how much of the original element is present and how much of the daughter element is present. • For very old things, the decay of uranium goes through a whole series of steps that end up at lead (symbol=Pb). The ratios of the different intermediates gives you a good idea of how long ago the process started.

14. Hadean Era and Cosmic Bombardment • The Hadean Era was the time before Earth had a permanent solid surface, before about 3.8 billion years ago. • Very few rocks from then: some zircon crystals • Lots of objects in irregular orbits around the Sun. • A large object (about the size of Mars) hits the Earth, vaporizing a lot of it. This material slowly accretes to form the Moon. The "giant impact" hypothesis. • Also gave Earth its 23o tilt, which causes our seasons • Lots of other collisions occur, producing the craters on the Moon, Mars, Mercury, moons of Jupiter, etc. • Earth too, but weathering has erased most of them by now. • The collisions added a lot of water and gases to Earth--our oceans and atmosphere • Probably no oxygen in the atmosphere. Mostly nitrogen and carbon dioxide (as on Mars and Venus).

15. Time Lines • Geological eras end with mass extinction events, where a large percentage of living organisms die off rather suddenly.

16. Origin of Life on Earth • In the present time, all life comes from other life. There is no spontaneous generation of life from non-living material • But, at some point in the past, life must have arisen from inanimate matter. • So, what is life, and how could it arise? • NASA: life is a self-sustaining set of chemical reactions capable of reproducing similar copies of itself. • Metabolism: extracting energy and materials from the environment to maintain a constant internal state and to reproduce. • Reproduction: requires genetic instructions to create a copy of the original organism. • A key concept: natural selection. Organisms that can survive and reproduce better than others have more descendants. This increased fitness is caused by small changes in the genetic instructions (mutations). • The trick is to get both metabolism and reproduction started at once. • Metabolism only: can’t adapt to changing conditions • Reproduction only: where do the raw materials come from?

17. Theories • Primordial soup. Organic compounds, including many found in living organisms, can be formed from gases that existed on the primitive Earth by lightning, radiation, or heat. They also are found in comets: organic compounds are very common in outer space as well as on Earth. They were undoubtedly present from the beginning on Earth. • Darwin’s idea, still reasonable today: life may have begun in a "warm little pond, with all sorts of ammonia and phosphoric salts, lights, heat, electricity, etc. present, so that a protein compound was chemically formed ready to undergo still more complex changes….At the present day such matter would be instantly devoured or absorbed, which would not have been the case before living creatures were formed.“ • Deep sea vents (iron-sulfur word). Lots of chemicals that can be used to generate energy, catalysis maybe occurred on iron-sulfur crystals. The idea here is that maybe life started under harsh conditions: high temperatures and pressures, and not in a nice warm little pond.

18. More Theories • RNA world. RNA is a molecule similar to DNA that can both store genetic information and catalyze chemical reactions. Maybe self-reproducing RNA molecules were the first form of life. • Similar theories propose self-replicating lipids, polyphosphates, clay minerals • Panspermia. Maybe life originate elsewhere in the Universe and floated in as bacterial spores. For instance, Mars cooled faster than Earth and had water in the early days—maybe life started there. • Lots more! • There may have been many different types of simple organism alive in the early days, and they probably traded genes, merged together, and split apart in many different ways. • At some point there was a Last Universal Common Ancestor, an organism that all life on Earth are descended from. However, life probably existed long before this, and many organisms contributed to this LUCA.

19. How Long has Life been on Earth? • Earth formed about 4.6 billion years ago, and probably had a solid surface 3.8 billion years ago. • But, not many rocks exist from this long ago. • Early life was all microscopic, with no hard parts that fossilize easily. What fossils exist just look like small rods: microfossils. • Several examples of microfossils from about 3.4 billion years ago • Stromatolites are mats of bacteria with minerals incorporated. They still exist today, and fossil stromatolites are up to 3.4 billion years old. • Basically, life has been on Earth throughout most of its history,

20. Age of Prokaryotes • This era, from about 4 billion to 2 billion years ago, is called the Archaean Era. • Prokaryotes are simple, single celled organisms. Bacteria are prokaryotes. The other group of prokaryotes is the archaea, which usually live in extreme environments: high temperature, high salt, etc. • Prokaryotes are one of the two main forms of life: the other is eukaryotes. • The difference is that eukaryotes have their DNA in a nucleus (enclosed in a membrane separate from the rest of the cell) and prokaryotes don’t. • All plants, animals, and fungi are eukaryotes. There are also many unicellular eukaryotes.

21. Tree of Life Modern View  Older view

22. Energy in Biology • The first cells were probably chemotrophs, meaning that they got their energy from chemical reactions and not sunlight. • Energy is everywhere, but how can it be captured for use in living organisms? • Life is fundamentally a complex set of chemical reactions, which means the movement of electrons between atoms. Useful energy is captured by taking high energy electrons from one molecule and transferring them to another molecule that accepts lower energy electrons. This process is oxidation. • Technically, the compound that loses electrons is oxidized and the compound that gains electrons is reduced.

23. Oxidation • Fire is an example of rapid oxidation: high energy electrons are extracted from carbon compounds in whatever is burning, and given to oxygen, which has a strong affinity for electrons. This creates carbon dioxide and water, plus releases a lot of energy. • Rusting is another example of oxidation. Electrons are removed from iron atoms by oxygen atoms, which then form the compound iron oxide (rust). • Many living things, including both plants and animals, get their energy from the sugar glucose, which gets oxidized into carbon dioxide and water.

24. Energy Sources • Two basic sources of high energy electrons: sunlight and chemicals. Organisms using sunlight for energy (like plants) are phototrophs, and organisms using chemicals for energy (like animals) are chemotrophs. • Plants (and cyanobacteria) use the energy from sunlight to extract electrons from water and boost them up to high energy. This energy is then used to convert carbon dioxide into glucose, which the cell uses for the rest of its energy needs. • Starch and sugars are just glucose polymers, to store food for later use. • Animals convert a variety of compounds into glucose, and then oxidize it to generate energy. • Bacteria can use many different chemicals as sources of high energy electrons: hydrogen gas, sulfur, iron. methane, ammonia, carbon monoxide. • Early life probably used some of these energy sources: photosynthesis is a much more complicated process.

25. Photosynthesis and the Appearance of Oxygen: Global Extinction Event • Simple forms of photosynthesis have existed for a long time. • However, the type of photosynthesis that generates oxygen from water, the main type used today, appeared among the cyanobacteria about 3 billion years ago • This is called Z-scheme photosynthesis: it needs 2 separate photons of light to get the electrons up to a high enough energy level to run the Calvin cycle, which is what converts carbon dioxide to sugar. • note: oxygen is just a waste product of photosynthesis • Cyanobacteria have also been called “blue-green algae”, but this is outmoded: cyanobacteria are prokaryotes and all other algae are eukaryotes • Oxygen is very reactive, and it killed most of what was alive at that time. • bacteria that cause gangrene, botulism food poisoning, tetanus, etc. are killed by oxygen. These bacteria survived because they found ways of avoiding exposure to the air. • On the other hand, oxygen gas (O2) can be converted to ozone (O3), which absorbs UV light from the Sun. This allows organisms to live on the surface without constant UV-induced mutations.

26. Rise of Eukaryotes • All that oxygen was an opportunity: you generate 15 times as much energy from glucose if you can use oxygen than if you can't. The primary beneficiaries of this were the eukaryotes, which have much more complicated cells than the prokaryotes. • Eukaryotes are defined as cells that have their DNA enclosed in a membrane (the nucleus). • What all cells have: • DNA (genetic information) • Cell membrane (keeps the inside separated from the outside) • Protein synthesis machinery (proteins do most of the useful work) • Ability to extract usable energy • Biosynthesis machinery (convert chemical compounds into useful cell parts) • Eukaryotic cells only: • DNA in a membrane-bound nucleus • Other internal membrane-bound organelles • Cytoskeletons • Tightly regulated cell division (mitosis)

27. Prokaryotic and Eukaryotic Cells • .

28. Origin of Mitochondria and Chloroplasts • Mitochondria generate most of the cell’s energy, Chloroplasts do photosynthesis. Both organelles contain their own DNA. • Endosymbiont theory: a primitive eukaryote swallowed a bacterial cell that could use oxygen to generate energy, and they developed a symbiotic relationship. The eukaryote supplied the food, and the bacteria supplied the energy. The bacterial cell degenerated, with most of its DNA going into the nucleus, becoming the mitochondria. • Later, the same thing happened with chloroplasts: a primitive eukaryote swallowed a photosynthetic cyanobacterium, which became the chloroplasts found in plants and algae.

29. Appearance of Sexual Reproduction • A fundamental principle: to survive changing conditions and spread new useful traits, all organisms have some mechanism of exchanging DNA. • Each prokaryotic cell has a single parent: the cell simply replicates its DNA, then divides in half. • However, prokaryotes also trade short, random pieces of DNA between species very frequently. This is called horizontal gene transfer. • Eukaryotes have a much more regular mechanism for exchanging DNA: sex. Each organism has 2 parents, each of which contribute equally to the offspring. • Many eukaryotes have several generations of asexual reproduction between rounds of sexual reproduction. This is especially true in plants, which can often be propagated through cuttings (asexual) instead of seeds (which are the result of sex). • Sexual reproduction produces new combinations of genes. Combinations that work well survive, while combinations that don’t work well die or fail to reproduce. That is, sex produces the variation that natural selection works on.

30. Life Cycles: haploid and diploid phases • Definitions: • Haploid = one copy of every gene (typical in prokaryotes and lower eukaryotes). 1n • Diploid = two copies of every gene (higher eukaryotes, including most plants and animals). 2n • Sexual reproduction involves two steps: • First, two haploid cells fuse together: fertilization. The result is a diploid cell, the zygote. • Then, the diploid cell divides into haploid cells again: the special cell division called meiosis. • In the process of meiosis, one copy of each gene is chosen randomly to go into each offspring. This makes all the offspring slightly different from each other. • This lead to an acceleration of evolutionary change.

31. Rise of Diploidy • Originally, eukaryotes were haploid, and only became diploid during fertilization, which was immediately followed by meiosis. • Such organisms often have multiple mating types instead of two sexes. Fertilization occurs if the two cells have different mating types. • However, having 2 copies of each gene gives you a backup copy in case a mutation occurs. So, a diploid organism is much less sensitive to mutations than a haploid. • Virtually all large (i.e. visible to the naked eye) land-dwelling organisms are diploid • Mosses are mostly haploid • So are some seaweeds.

32. Cambrian Explosion and Multicellular Life The sudden appearance of multicellular fossils in the rocks, about 600 million years ago Almost everything was living in the sea back then All major groups of animal life that are around today appeared during the Cambrian Era. Plus many groups that are now extinct Cause is unknown. Maybe because of an arms race between predator and prey, with the development of hard parts: teeth, claws, shells. It is now known that animals existed previous to this time, but clearly something happened to rapidly expand their number and diversity. Plants were not affected much by the Cambrian Explosion, but they went through a similar phase about 400 million years ago, in the Devonian period.

33. Geological Ages • Geological ages end with mass extinction events. The causes are probably varied. • The most recent big event, the end of the Mesozoic era (age of dinosaurs), came when a large object (10 km diameter) hit the Yucatan peninsula 65 million years ago. The resulting dust seems to have stopped photosynthesis for several years, resulting in the death of virtually all large animals. • Other possibilities: massive lava eruptions, sustained periods of global warming or cooling, ice covering almost the entire Earth, nearby supernovas, release of methane from ice under the seas, release of hydrogen sulfide from the seas, and lots more. • Mass extinctions seem to affect plants much less than animals, probably due to dormant seeds, which can wait out the bad times. • Effect on microorganisms is unknown: they rarely fossilize. • Marine animals affected as well as terrestrial • Followed by adaptive radiations, as the survivors expand into new niches. Many species arise rather quickly from single species

34. Our Story So Far • We have come 5/6 of the way through the history of the Earth • Earth forms 4.6 billion years ago • Solid surface forms 4 billion years ago • Life starts (?) 3.8 billion years ago • Age of Prokaryotes • Oxygen atmosphere develops 2 billion years ago. • Eukaryotes develop. • Cambrian explosion: many new forms of animal life. 600 million years ago.

35. What is a Plant? • Seems like a good time to approach the subject matter of this class. • Traditionally, botany (the study of plants) included bacteria, fungi, and algae as well as what we would consider true plants today. • This is based on the idea that all life could be classified into either the Plant Kingdom or the Animal Kingdom. • Nowadays, bacteria are better classified as prokaryotes, while the others are all eukaryotes. This distinction is very fundamental, and no one would consider bacteria to be plants today. • One caveat to this: the cyanobacteria use the same form of photosynthesis used in plants today. This is because the chloroplast is derived from an ancient symbiosis between a cyanobacterium and a primitive eukaryote.

36. What is a Plant? • Like plants, fungi (at least many of them) live on the land and don't move around under their own power. Fungi don't have photosynthesis: they eat by secreting enzymes into their surroundings and then taking in the digested nutrients. • Like plants, fungi have cell walls, but the fungal cell wall is made of chitin, the same substance as the insect exoskeleton. The plant cell wall is mostly cellulose. • DNA studies have shown that fungi are actually more similar to animals than to plants. • Algae are photosynthesizing eukaryotes that live in water. They are less complex than plants, and some are unicellular. The big multicellular ones are called seaweeds. • Algae are a large and diverse group that includes the red algae, green algae, and various unicellular forms. • Plants evolved from green algae. • We will touch on algae and fungi in this class, but we will concentrate on the true plants.

37. Invasion of the Land Life started out in the sea. About 450 million years ago, plants and animals started moving onto dry land. It's dry out here, and you need to support yourself against gravity. Animal adaptations: Lungs. Gills need water to support them, absorption of oxygen through the skin isn’t fast enough Legs. Maybe originally to get their heads out of the water in oxygen-poor areas. Waterproof eggs (reptiles and later). Allow reproduction away from water. Plant adapations: Cuticle: waxy layer to prevent dessication Stomata: openings to let carbon dioxide in Vascular system: the plant’s circulatory system Roots to absorb water from the soil, and leaves to pick up more sunlight Move to mostly diploid plant body (and not haploid) Reproduction that doesn’t require water: retention of the embryo in the plant body, pollen, seeds Woody tissues to get taller and compete for sunlight better

39. The Origin of Plants • True plants all seem to have evolved from a single common ancestor. • Plants evolved from the green algae, the Chlorophytes, which contain chloroplasts and engage in photosynthesis. In fact, you could say that land plants are really just a specialized group of green algae that are adapted to life on land. • Plants are called Embryophytes, and the main distinguishing characteristic that distinguishes them from the green algae is that they retain the embryo (multicellular diploid product of fertilization) within the larger plant body. (i.e. fertilization occurs within a structure in the plant body, and the zygote stays there while it develops into a multicellular embryo). • In contrast, fertilization in the green algae occurs outside the body, and the zygote is a single-celled free living organism. • All plants are land-dwelling, multicellular eukaryotes. • However, there are some plants which evolved on land, but moved back into the water later • Algae, which live in the water, are more primitive and not considered plants • there are no single-celled plants.

40. Plant Evolutionary Trends • Dessication resistance: • The most primitive plants, the mosses, liverworts, and hornworts (bryophytes) mostly stay in wet areas, but they can also shut down their metabolism and survive drying out • higher plants have a cuticle (with stomata so gases can get in and out), and vascular tissue to move water and nutrients around • Move from mostly haploid (gametophyte) to mostly diploid (sporophyte), allowing more complex organisms. • Reproduction that doesn't need water,: ferns and below have sperm that swim through water. Above this, dessication-resistant pollen grains and seeds • Flowers: get animals to help reproduction

41. Alternation of Generations • A few definitions: • Spore vs. gamete. Spores will germinate into multicellular organisms on their own, but gametes need to combine with other gametes first. • Spore vs. seed. Seeds contain stored food and spores don't. This gives seeds more ability to survive bad conditions. • Means alternating between a multicellular haploid form (the gametophyte) and a multicellular diploid form (the sporophyte). • Note that animals have a multicellular diploid form (our bodies), but the the haploid stage (sperm and eggs) is just one cell, never multicellular. • All plants have alternation of generations, but so do other groups such as fungi and many protists. • The haploid gametophyte grows from a singe celled spore, and it produces gametes by mitosis. • The gametes fuse during fertilization to form the zygote, which develops into the multicellular diploid sporophyte. The sporophyte then produces haploid spores by meiosis.

42. Mass Extinction: the End of the Dinosaurs • There have been several mass extinction events. • The biggest, which killed 95% of all species, occurred 250 million years ago: the Permian extinction. Its cause is still debated. • More recently, 65 million years ago, a large object (like 10 miles in diameter) hit the Yucatan peninsula in Mexico. The dust generated seems to have shut down photosynthesis on Earth for several years. • This event killed all large animals, especially the dinosaurs. Plus quite a lot of other species. • And this made room for the major adaptive radiation of the mammals. • Before this, mammals were all small and uncommon animals. • The flowering plants (angiosperms) originated well before this time, but they also had a major expansion after the Cretaceous Extinction event

43. Origin of Flowering Plants • A lot of comparison of DNA sequences has led to the idea that Amborella, a shrub found on the Pacific Island of New Caledonia, was one of the first angiosperms (flowering plants) to appear. • Also very early: water lilies and magnolias • The first fossils that are unambiguously angiosperms come from 132 million years ago, the middle of the Mesozoic Era (dinosaurs). • However, DNA data suggests that the first angiosperm may have appeared as much as 50 million years earlier than that. Maybe the right fossils haven't been found yet. • An alternative theory places their origin at least 250 million years ago, in the Paleozoic era. Controversial, and lacking support from DNA. • Angiosperms had a major adaptive radiation in the Mesozoic era: many types appeared over a short time, leading to many different angiosperm fossils.

44. Mammals Take Over

45. Great Ape Adaptive Radiation

46. Hominids

47. Homo and Paranthropus

48. Neanderthals vs. H. sapiens

49. Prehistoric Humans Ice Ages

50. Agriculture, Art, Writing, Civilization Agriculture Animal domestication: dogs, horses how to live in cities writing art and music migrations: voluntary and involuntary war: cultural assimilation, and genetic too trade prostheletizing religion nationalism: belong to a larger group than just your relatives scientific rationalism steam engine: Industrial revolution printing press modern medicine: anaesthetics, antibiotics, studying animal and cadaver models, microbes long distance communication: information science democracy: works better than hereditary kingship, and change of leadership is less disruptive than strong man rule