Introduction to Physical Science Monday, Wednesday, Thursday Tom Burbine tomburbine@astro.umass

1. Introduction to Physical ScienceMonday, Wednesday, ThursdayTom Burbinetomburbine@astro.umass.edu

2. Atoms • Atoms are made up of 3 types of particles • Protons – positive charge (+1) • Electrons – negative charge (-1) • Neutrons – neutral charge (no charge) • Protons and Neutrons are found in the nucleus

3. Strong Nuclear Force • Keeps protons and neutrons together in the nucleus

4. Radioactivity • Radioactivity – decay of an atomic nucleus • All elements with an atomic number greater than 82 (lead) are radioactive

5. How old is the solar system?

6. How old is the solar system? • ~4.6 billion years • All meteorites tend to have these ages • Except:

7. How old is the solar system? • ~4.6 billion years • All meteorites tend to have these ages • Except: • Martian meteorites • Lunar meteorites

9. How old is the universe?

10. How old is the universe? • ~13.7 billion years (±200 million years)

12. Radiation dosage • 1 rad = 0.01 J of radiant energy absorbed by kilogram of tissue • Rem = rads x Q where Q is a quality factor which attempts to convert rads from different types of radioactivity into a common scale of biological damage.

13. Radon is a naturally occurring radioactive gas

14. Ages • Ages

15. How do you determine this age?

16. Radioactivity • The spontaneous emission of radiation (light and/or particles) from the nucleus of an atom

17. Some types of radiation • Alpha particle – 2 protons and 2 neutrons (Helium nucleus) • Do not normally penetrate clothing • High kinetic energy (due to high mass) ; can damage living tissue • Beta particle – electron (from a neutron when it becomes a proton) • Penetrate clothing and into skin • Gamma ray - High-frequency radiation • Penetrate into skin and can damage molecules in cells

19. http://www.darvill.clara.net/nucrad/types.htm

20. Radioactivity http://wps.prenhall.com/wps/media/tmp/labeling/2130796_dyn.jpg

21. Half-Life • The time required for half of a given sample of a radioactive isotope (parent) to decay to its daughter isotope.

22. Radioactive Dating • You are dating when a rock crystallized http://faculty.weber.edu/bdattilo/images/tim_rock.gif

23. Radioactive Dating n =no(1/2)(t/half-life) no = original amount n = amount left after decay

24. Exponential decay is where the rate of decay is directly proportional to the amount present. http://www.gpc.edu/~pgore/myart/radgraph.gif

26. Remember • Number of original atoms (parent atoms) • = number of daughter atoms today + number of parent atoms today

28. http://academic.brooklyn.cuny.edu/geology/leveson/core/topics/time/graphics/radio1.gifhttp://academic.brooklyn.cuny.edu/geology/leveson/core/topics/time/graphics/radio1.gif

31. What are the assumptions to get an age?

32. What are the assumptions? • No loss of parent atoms • Loss will increase the apparent age of the sample. • No loss of daughter atoms • Loss will decrease the apparent age of the sample. • No addition of daughter atoms or if daughter atoms was present when the sample formed • If there was, the age of the sample will be inflated • These can possibly be all corrected for

33. Commonly Used Long-Lived Isotopes in Geochronology

34. How do you determine isotopic values?

35. How do you determine isotopic values? • Mass Spectrometer

36. It is easier • To determine ratios of isotopic values than actual abundances

37. Carbon-14 • 99% of the carbon is Carbon-12 • 1% is Carbon-13 • 0.0000000001% is Carbon-14 • The half-life of carbon-14 is 5730±40 years. • It decays into nitrogen-14 through beta-decay (electron and an anti-neutrino are emitted).

38. Due to Carbon-14’s short half-life, can only date objects up to 60,000 years old

39. Plants take up atmospheric carbon through photosynthesis http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/cardat.html

40. When something dies, it stops being equilibrium with the atmosphere http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/cardat.html

41. Why is Carbon-14 still present if it has such a short half-life?

42. Why is Carbon-14 still present if it has such a short half-life? • Cosmic rays impact Nitrogen-14 and create Carbon-14 • Cosmic rays are energetic particles (90% are protons) originating from space. From the Sun (solar cosmic rays) or outside the solar system (galactic cosmic rays) • n + 14N → 14C + p

43. http://en.wikipedia.org/wiki/Image:Radiocarbon_bomb_spike.svghttp://en.wikipedia.org/wiki/Image:Radiocarbon_bomb_spike.svg

44. Any Questions?