Astronomy 1020-H Stellar Astronomy Spring_2016 Day-2

Snow-2, Education-0

Course Announcements Smartworks Chapter 1: Start on – it will be due next week. Make sure you hit “submit” to record your answers – AFTER you finish the entire assignment (not after each question). If you plan to do some and then come back, write your answers down on a piece of paper. Because of the snow (and ice) nothing will be due until after we return to the classroom.

 Modern astronomy is more than cataloging objects.  How do stars (matter and energy) work?  What is the universe?  How do humans fit in?

 The Universe is BIG!  Earth is a small planet,  orbiting a medium-sized star,  in a galaxy of 400 billion stars,  which is just one of billions of galaxies,  in a universe that is 13.7 billion years old. Size

The Universe is Strange

New Concept: Cold Dark Matter

 The universe is vast.  Billions of galaxies are separated by thousands of trillions of miles.  How do you visualize this?  Astronomers need to be able to talk about great distances.  We use the distance light will travel in a year as a basic “yard stick”. Size

 Light travels 300,000 km every second.  Universe’s greatest speed.  Light-year: distance light travels in one year – about 6 Trillion miles (9.4 Trillion km)  Light could travel around Earth in 1/7 second. Distance Measures

Light Travel Times  At this speed, light takes, on average: 1¼ seconds to arrive from the Moon. 8.3 minutes to arrive from the Sun. 5.5 hours to get to Pluto from the Sun.

 It will take: 4.2 years to arrive from the nearest star. 100,000 years to cross the galaxy. 2.5 million years to get to the nearest big galaxy. 10 billion+ years to come from distant galaxies. This can make studying objects difficult.

 But, studying the universe reveals many things.  For example, except for the hydrogen in water (H 2 O), all the atoms in our body were made in stars.  Stars generate energy by making heavier elements out of light ones.

 Dying stars eject those elements into space in massive explosions.  New stars and planets (and humans) form.  We are stardust, made from the materials provided by earlier generations of stars.

 Test scientific ideas by observation.  Space exploration has expanded our view of planets and the Solar System.  Telescopes, satellites, etc., extend it more.

 Science involves the use of theories, hypotheses, and principles.  A scientific hypothesis is an idea that leads to testable or falsifiable predictions.  The cosmological principle is a very important underlying assumption: “There is nothing special about our place in the universe.”

 Cosmological principle on one level: Our view from the Earth is not special or unique. Distant objects should be like nearby ones, which we can study in detail.  On another level: Matter and energy obey the same physical laws everywhere. We can learn about distant objects by studying nearby ones.

Science Is Creative Science is one of many creative human activities. It has its own rules for deciding what is right and wrong. It is an important way for achieving knowledge and insight. There are also other valuable ways to achieve understanding.

Science Is Subversive Old ideas can be falsified and rejected. New ideas must be supported by evidence. Authority often works by suppressing inquiry. Scientific authority can be overthrown by new or better evidence. Nature is the arbiter of science. It decides what ideas are good or bad. (Occam’s Razor)

Scientific Progress The scientific processes and investigations can be slow: many small steps and tweaks. Every now and then, there is a revolution and progress is very rapid in both new knowledge gain and understanding the implications and effects. Newtonian Mechanics Quantum Mechanics Evolution

Science Is a Process Science is a method for learning about nature. The scientific method works like this: Ideas are tested against nature. Tests come from observation or calculation. The tests falsify some ideas and support others. All scientific knowledge is provisional. Science involves Exploration & Discovery HST Curiosity

The Scientific Method To be accepted as valid, an idea must be testable and falsifiable. This separates “fact” from “faith”. We use the “Scientific Method”. The heart of the Scientific Method is making a testable prediction based on a valid hypothesis (or theory).

Cute and Science

Math: The Language of Science Review page 16 – Math Tools 1.1 box. You should feel comfortable working at this level. You’ll need at least these skills just to live in the modern world. Scientific Notation Ratios Geometry Algebra Proportionality

Dealing with very large and small numbers Scientific Notation 4,500,000,000,000,000 = 4.5x = 2.8x On calculators…look for the “EXP” key or the “EE” key

Common Prefixes Don’t let the units confuse you. centi = 0.01 = (c) milli = = (m) micro = = (m) nano = = (n) kilo = 1,000 = 10 3 (k) mega = 1,000,000 = 10 6 (M) giga = 1,000,000,000 = 10 9 (G) tera = 1,000,000,000,000 = (T)