Electromagnetic spectrum, light, astronom.ical tools. How we know about the stuff in space - by looking (i.e., using light and by analyzing other radiation). Astronomy is observational and technology-driven; we usually make new discoveries through improved instruments.
Light shares wave-particle duality with electrons and has wavelength, frequency, and speed. Speed is always c (in vacuum) but wavelength and frequency (related) can vary. (Light slows down in other media: atmosphere, water, etc., which changes wavelength, maybe 30%, must be corrected.) Experiments have slowed the speed of light with things like super-cooled cesium to less than speed of sound. Different colors of visible light correspond to different wavelengths.
Red dwarf star same spectrum as filament of incandescent light bulb (temperature about 3000 K). Landscape looks normal, not red. Don't see colors at light intensities either very high or very low.
Prism: light enters at angle, speed changes in crystal, disperses with red at one end and violet at the other. Spectroscopy is the "bread and butter" of astronomy. Visible light wavelengths range from 4,000 (blue) and 7,000 (red) Angstroms (used by astronomers) or 400-700 nm (nanometers used by physicists). Human eye decreases in efficiency at either end, with some variation; animals can see farther into infrared and ultraviolet than we can. Rods = b & w, more sensitive to low levels of light; cones perceive blue - green - red.
Spectrum - light of all possible wavelengths. Gamma - x rays - u/v - visible - micro - radio (UHF - VHF - FM - AM) = all travel at speed of light. Atmosphere is transparent only to visible light and radio, so we need to put x-ray telescopes in space, not on the ground. Water vapor (occurs at low altitudes) poses a particular problem, so put infrared telescope on airplanes or balloons. All light diminishes according to inverse-square law. Greenhouse gases absorb infrared radiation (need some, CO, CO2, H2O).
Light can behave as particles, e.g., photoelectric effect. The energy of a photon does not depend on the intensity of the light. Higher energy photons in uv = skin damage; threshold for chemical damage is proportional to number of photons above threshold.
Temperature/heat; thermal energy is "kinetic energy" of moving atoms and molecules. Hot material energy available for chemical or nuclear reactions (i.e., centers of stars), escape of gases from planetary atmospheres, creation of light. Temperature determines how tightly planet retains its atmosphere (Titan vs Earth).
Temperature scale, energy proportional to temperature, C and F not proportional, get negative degrees. Kelvin uses 0 = no energy, if double then doubled energy. -273 C = 0 Kelvin (don't use degrees for Kelvin.)
Hot objects emit light; some wavelengths go through glass better than others. Infrared goggles don't work through windows. (Glass is reflective in infrared.) The hotter a body, the more light it emits and the more high energy photons (blue flame is hotter!) We radiate in 10 microns in infrared. (Thermally, red is cooler, blue is hotter.) As stars get hotter, emitted light shifts toward higher frequency (blue). Our sunlight is not green because it's a mixture of frequencies that appear white. If we got close to a blue or red star and light saturates our retinas, they would appear white as well.
For a green star, put stuff in atmosphere to make star appear green by modifying its spectrum. Mars has a red sky because of iron oxides in atmosphere. Doubly-ionized oxygen (extremely rare, in space) called nebulium, first seen in nebulae, emits green at 5007 A.
Every element has "fingerprint" of energy levels, so we can determine chemistry of celestial objects by comparing spectra with known. Above a certain energy, electrons can escape (ionization).
Telescopes. Modern professional telescopes are often very large; we need different types to observe other forms of radiation. Aperture produces fringe rings, these are smaller with larger diameter telescopes, so more resolving power. Sharpness of images can also be limited by turbulence of atmosphere.
Mirror technology - thinner, honeycomb segments controlled by computers, can compensate for atmospheric turbulence via "adaptive optics." Multiple telescopes to "cheat" simulating increased diameter, using interferometry. Prisms or gratings to split up light produce spectrum.
Radio telescopes use satellite dishes as mirrors, radio waves focused and amplified to be converted into images, etc. Radio waves long wavelengths, so use interferometry to improve resolution (i.e., VLA = Very Large Array - 27 dishes combined to simulate large dish of 36 km diameter). VLBA combine telescopes all over earth, milli-arcsecond resolution, even though radio wavelengths longer because of size of array. Radio astronomy reveals things like neutral hydrogen clouds, molecules. Radio waves penetrate gas and dust clouds so we can observe regions from which visible light is heavily absorbed.
Infrared astronomy; most absorbed in lower atmosphere, so must do from altitude or space. Ultraviolet absorbed by atmosphere so must be done from space; traces hot or moderately ionized gas
Hubble launched 1990, avoids turbulence in atmosphere, extends imaging and spectroscopy to infrared and ultraviolet. Compton Gamma-ray observatory 1991-2000, traces most violent processes in universe. Chandra X-ray telescope, 1999- highly eccentric orbit that takes it 1/3 way to the moon; traces hot, highly ionized gas, like colliding galaxies, 1st to give resolution like optical telescope, extremely complex gold-covered mirrors. Spitzer, infra-red, traces warm dust, discovered new globular cluster seen through dust clouds, moving through Milky Way, detected by Wyoming student.
Dust: need to be outside atmosphere to see dust. Infrared is completely different from visible images. In a visible-light image of a galaxy, red center, blue disc. Shift wavelength perspective and look at dust, and get colors reversed. Dust: very small asteroid/meteorites? Major extinctions about 100 my (million years), hypothesis mysterious planet X in Oort cloud, perturbs comets and sends them toward Earth. Most explode in atmosphere. Tiny grains strike Earth at about 40 tons a day, 1 per square meter every hour.
Milky Way looks patchy, what's in "blank" areas? Dust blocks light from background stars, or can polarize or redden light. Ices, graphites, silicates, metals, carbon, iron, silicon mixed with or coated with water.
Reddening: eclipse of moon: Blue light more easily scattered; red light remains continues to illuminate the moon (like sunset), due to combination of atmosphere and dust. Reflection nebulae - cloud of gas and dust illuminated by nearby stars. If seen from side looks blue scattered blue light.
Milky Way filled with different types of dust: interstellar silicate, carbon; circumsteller, CO, silicon carbide, amorphous silicates, PAHs, water ice, polyformaldehyde; cometary silicates, water ice; asteroidal: carbonaceous chondrites. Polycyclic aromatic hydrocarbons (PAHs) are rings of carbon with hydrogen appendages. Also from charred meat, carcinogen. Dust particles last only a billion years or so, so must be replaced by random accretions in interstellar space.
Space Medicine: Major risks: loss of atmosphere (pressure, oxygen), exposure to toxins, mechanical trauma, acceleration/deceleration, extreme temperatures, meteoroids and space debris, disruption of circadian rhythms and sleep, psychological esp. longer duration, adverse biological effects of microgravity (removal healthy stress of gravity), radiation
Atmosphere loss: barotrauma: expansion of gas temporarily trapped in a body cavity (ear, sinus); pressure differences cause pain or injury; decompression sickness: ambient atmosphere pressure > partial pressure of inert gases (nitrogen); nitrogen forms bubbles in bloodstream: bends (pains in joints, muscles) chokes (gas emboli), neurological (weakness, convulsions, syncope); explosive decompression: rate of decompression is so great that transient overpressure occurs in lungs and other air-filled cavities, also esophagus, bladder, etc. pressure difference in lungs > 80 mm Hg causes rupture and possible air embolism.
Ebullism - "boiling" of body fluids occurs at an ambient pressure of 47 mm Hg, 19 km = Armstrong limit.
Exposure to vacuum - loss consciousness, 5-6 sec with heart stop, this happened accidentally, but revived, but more things going on like ebullism; consensus is couple of minutes, eyeballs do not pop, no icicles.
Loss atmosphere: Ambient pressure/composition like sea level (14.7 psi, 78 N%, 21% O2). EVA requires space suit pressure 4.3 psi. Pure oxygen toxic after period of time unless at lower pressure equivalent to air. If higher, can't move in suit. To prepare for EVA, must slowly reduce cabin pressure to 10.2 psi for 24 hr. then don suits and prebreathe 100% O2 at 4.3 psi to purge nitrogen from the blood. Takes time!
Toxins: ammonia used in shuttle environment and life-support, causes irritation of eyes, mucous membranes, dyspnea, vomiting, pulmon edema; freon: heat exchange system; hydrazine and mono methyl hydrazine, aux power unit, burns, liver kidney damage, seizures; nitro tetroxide, used in orbital maneuvering devices, burns and blindness, pneumonitis and pulmon edema
Trauma, conventional burns, abrasions, lacerations, electrical shock, fracture, deliberately inflicted injuries (long duration possibility);
fatalities: Soyuz 1 1967, parachute failed during re-entry; Soyuz 11 (1971), decompression during re-entry; Challenge, Columbia.
Acceler/deceleration; excessive 9 (> 9.8 m/sec2) lightheadedness, syncope; sustained upper limit of 4 g and briefly 18 g for control of movement. Mercury program, up to 8 g briefly and 11 g re-entry. Shuttle - 3 g launch, 1.2-1.4 re-entry.
Temperature control. Heat exchange in space solely radiation, not conduction or convection; have effective tech.
Meteoroids and space debris, risk of collision; meteoroids are stone and iron, total 200 kg within 200 k Earth's surface, velocity 16 k/sec, most < 0.1 mm (bullet); space debris 3 million kg within 2000 km surface, old rocket boosters, destroyed satellites, flecks of paint or particles of rocket fuel, collision velocity 10-13 km/sec. NORAD monitoring 7000 objects.
Biorhythm is 24 hours; sleep/activity, temperature, heart rate, BP, growth hormone, cortisol, melatonin rates vary, Rapid travel across time zones disrupts synchronization between internal and external clocks "jet lag" (desynchronosis) insomnia, loss appetite, fatigue. Low earth orbit 80-140 mins 30-40% darkness. Problems: insomnia, poor quality or prolonged sleep, can degrade performance and alertness during routine or emergency situations, half shuttle astronauts use sleep meds.
Psychosocial: isolation, loss social contacts, reduced sensory stimulation, anxiety, boredom, loss privacy, emergencies, overly busy work schedules. (Mir) decreased motivation, emotional hypersensitivity and lability, irritability or hostile toward control personnel and crewmates on extended missions (Skylab, Mir, ISS). 2 alphas is recipe for disaster; common interests or complementary interests, mixed-gender crews do better. Women seem to tolerate long missions better. Cultural differences; alcohol on Russian missions. Multi-national having language in common. 400 people in space by now. Space psychiatry book.
Radiation: serious hazard for both acute and long term injury during prolonged space missions. Pervasive in space. Sun produces gamma and x rays and particulate radiation (electrons, protons, heavier like helium), Earth atmosphere filters out. Solar wind increases dramatically during solar particle events to very high energy levels, up to 500 MeV, "solar particle events." Has happened during missions, ISS crew got 6 rem in 6 days. Cosmic radiation constant source, very high energy protons, alpha particles and heavier ions originating outside solar system, possibly old supernovas, up to 2 GeV. Astronauts see flashes in eyes. Much harder to shield against, interact with lead atoms to produce more radiation, increase cumulative dose.
Earth surface protected by atmosphere (uv light, x rays, gamma rays); Van Allen belts, extraterrestrial electrons and protons trapped.
Average exposure 0.2 to 0.2 rem; LEO 14-21 rem; EVA and solar events - solar particle events assoc w/coronal mass ejections - can increase exposure, potentially to hundreds of rem. (240 rem/hr as example.) Proper shielding use underground habitats on lunar and Martian missions would drastically decreased radiation exposure.
Acute effects whole-body exposure:
< 50 rems few symptoms
prodromal (50-150 rem) will survive, fatigue, light-headed, nausea/vomiting (bad in space suit)
Hematopoietic syndrome (150-400 rem) above plus damage to rapidly-dividing cells, bone marrow, lose WBC, platelets risk infection, clotting; hair loss 3 weeks later; mortality low but need care.
Hematopoietic-GI syndrome (400-800 rem) all the above plus damage to intestinal lining; diarrhea within a couple of days; die of dehydration, gut bacteria can invade abdomen cause peritonitis or sepsis; fatalities - LD50 about 400 rem
GI syndrome (800-2000 rem) above, more so, quicker fatalities
CNS syndrome (> 2000 rem) brain/heart low rate cell division, more resistant. Mortality 100% even with best of care above 800 rems, within days.
Long term effects: cataracts, infertility, defects in offspring (sperm cell 72 days), cancer (breast, thyroid, leukemia, lung)
Total recommended cumulative radiation should not increase lifelong risk of cancer more than 3%; depends on age, gender (women breast cancer) men 63, women 47 rems.
Micro and low gravity: neurovestibular: space adaptation syndrome (2/3 males > females) headache, nausea, vomiting, dizzy, malaise,
cardiovascular; made worse by head and body movements; shortly after entering orbit, peaks 1-2 days, usually resolves 4-7 days; responds well to motion sickness medications, reduced somewhat by repeated exposure. Sensory illusion ("inversion illusion"); postflight problems; feeling levitated over bed, ataxic gait (like drunk) or walking straight when trying to turn corner, feeling heavy or pushed to one side when standing, weeks to months to resolve.
Cardiovascular: shift 1.5 - 2 L fluid from lower to upper body within minutes from loss of gravity-induced hydrostatic pressure: jugular venous distention, facial puffiness, nasal congestion, headaches, nasal voice, reduction calf diameter up to 30%, enlargement of liver and other visceral organs (can alter effects meds); decreased sympathetic tone, orthostatic hypotension and syncope on return to Earth esp w/redistribution of 1 L reduced total body fluid volume to lower extremities.; heart size and mass incr sl, not sig; variable mild changes in heart rate, PB, minor arrhythmias.
Hemo: mild anemia, reversible takes up to 60 days; spherocytes and echinocytes increase (abn. Cells), changes WBC
Musculoskeletal; relaxed astronauts assume fetal position, with loss normal thoracolumbar curve. Increased height of disks but puts increased pressure spinal nerves; decrease muscle mass esp weight-bearing legs and back; need vigorous exercise program up to 3 hr/day of resistive exercises to stabilize muscle mass at 80-85%; if injured and can't exercise, stabilizes at 60% or lower; postflight weakness and soreness, muscle mass returns with exercise to normal. Increased demineralization of bone, total bone mass, incr urinary and fecal calcium loss (urolithiasis = kidney stones). Mechanism for bone loss not established, whether less laid down or more resorbed; can stabilize 15-20 % preflight esp weight bearing bones; but may not return to normal even years later. Treadmill, rowing, ergometer, isometric better than isotonic, supplements not proven of value; "penguin" suit with elastic straps to create resistance not established.
Postflight orthostatic hypotension, ingest salt and water before reentry; lower-body negative-pressure devices (Chibas suit), g-suit (compression of lower body to help adaptation); artificial gravity, rotation, tethered system, centrifuge for intermittent use. Need 2 rotation/min 225 m radiation for 1 g - cost factor. Adverse effects should be milder on Mars.
Crew live in restricted quarters for a week prior to launch to minimize exposure to communicable diseases. Medical officers paramedic level training if not physicians, training in space physiology, CPR
Nutrition, need 2500-3000 cal/day, more than on earth, negative nitrogen balance; fluid intake up to 4200 ml/day reduce chance kidney stone; changes in taste and odor esp due to nasal congestion; thermostabilized, etc. stored dry form, forced-air convection oven.
Personal hygiene difficult in microgravity; bathing difficult, boils, dermatitis; constipation; contamination by microorganisms, wastes, animals, payload items. Microbes continuously shed from skin, etc., droplets remain suspended and can be inhaled; increased bacterial resistance to antibiotics and reduced immune function.
Limited equipment and supplies; limited expertise and medications;
No rising air or layering of fluid on x-rays, no air-fluid levels in bowel obstruction; Trendelenberg position doesn't work to reduce bleeding or for CHF. Meds timing of dosing changes absorption etc.
Surgery: all individuals must be restrained; difficulty maintaining a sterile field, must secure drapes, airborne particles don't settle, special techniques for putting on gloves and gowns; special equipment for washing and disinfecting equipment; use inhaled anesthetic in confined area is dangerous; spinal anesthesia depends on gravity; spurting arteries produce blood droplets, venous blood forms hemispheric domes. Abdominal viscera float out of abdomen. IV fluids require pressure pump, as for arteries on Earth or squeeze bag manually. Collecting urine or blood doesn't settle to bottom of container.
Major health sequelae will most likely be due to radiation. Sample size is too small (400) to make good predictions.
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