Astronomy Test 4
cosmic haystack
1. Direction 1 in sky 2. Direction 2 in sky 3. Depth (signal strength) 4. Bandwidth 5. Frequency 6. Polarization 7. Modulation 8. Time
When we search for signals from other intelligent civilizations, one of the regions of the spectrum that we avoid is the ultraviolet (UV) portion of the spectrum. Give two reasons why it would probably be a waste of time to search this region of the spec
1. UV radiation causes biological damage. Humans and most mammals get burned from high exposure. So it is likely that the same would occur to other intelligent civilizations. 2. It takes too much energy to search this spectrum.
criteria for detection
1. must make sense 2. has to come from the sky 3. has to come from outside the earth 4. signal is confirmable 5. must confirm more than once with more than one team and more than one machine
Close encounters
1st a sighting of a ufo 2nd includes a physical effect 3rd an observation of animate beings 4th an abduction
general relativity
According to the General Theory of Relativity, a massive object warps or bends the spacetime around it. The gravity that we feel is the result of this bending. - A central idea in General Relativity is that space and time are related to one another and must be considered together, not separately.
The Drake Equation has two possible extreme interpretations, a pessimistic and an optimistic interpretation as to the value of "N". Briefly explain arguments against each of these two extreme interpretations.
An optimistic estimates that the number of intelligent civilizations in our galaxy could be as many as 3x10^7 . The optimist views things as if an organism can exist in a planet, then there is a possibility that it can evolve into an intelligent life form. A pessimist estimates that there could be a maximum of 10 intelligent civilizations. Based on his estimates, even if living organisms could exist at other planets, the likelihood that they could evolve into intelligent lifeforms is very unlikely. Pessimists are likely to think that the only living intelligent civilization in the Milky Way is ours.
Assuming that if any aliens are trying to contact us, they are using very narrow-bandwidth signals, explain why we would want to search the spectrum using very narrow bandwidth channels (even though such a search would be much more time consuming than splitting the spectrum up into fewer broad channels).
By restricting the signal to a narrow range of frequencies, the receiver can filter out much of its own noise by employing a filter that simply removes all the noise contained in frequencies that are not of interest. Hence, the narrower the range of frequencies, the more noise can be excluded, and the more favorable is the ratio of signal to noise. Radio receivers can be made very sensitive by this method, but the problem is that the more information a signal carries, the wider the range of frequencies of which it consists, and that limits how much filtering can be done. Filter out too much and you filter out the information the link is carrying.
Explain why it is that when we look out into the universe, we see into the past.
It takes time for light to travel from one place to another so we see distant places, like starts, as they were when the light left in the past
How is the kinetic equation used to understand the energy needs for interstellar travel?
Kinetic equation measures the energy needed to accelerate a mass to light speed.
Explain why the number of currently existing, intelligent and communicative civilizations in our galaxy is proportional to the average lifetime of such civilizations (I'm not asking you to restate the Drake equation...I'm asking you to explain it).
L (length of time a civilization tires to communicate, in years) is the most uncertain time in the Drake equation. A large uncertainty in any one number results in a large uncertainty for N. If any of the factors of the Drake equation is very small, than N is very small. The drake equation assumes that, whatever the other factors, the number of civilizations presently in our galaxy is simply proportional to their average lifetime. The longer they live, the more civilizations exist at a given time.
Critics of evolution wonder how a process based on random chance could result in extremely complex organisms. How do biologists respond to this argument?
Life selection is a process, so it keeps the variations that work and gets rid of the variations that dont work, so not purely random
What discovery did the Magellan spacecraft make about the recent geological history of Venus?
Magellan discovered a fuzzy appearance around Venus, which turned out to be clouds made of sulfuric acid. We also learned that Venus is a highly volcanic planet. also they discovered that it has gone through a dramatic change about 500 million years ago
Can you get younger by traveling at speeds near the speed of light? Explain.
No because no matter how fast you go, time still moves forward for you. Time seems to move normally for you, but others see it as slower
On the 5-km highway of time representing the history of Earth, what length accurately reflects all of recorded human history?
On a 5-km highway, one km would equal one billion years. So the length that replicates the beginning of human history being recorded would be equal to the last couple of millimeters.
What arguments can you make that evolution is very unlikely to result in intelligence? What is an emergent property? Explain this concept in general, and then give one example.
One argument that can be made is that there are 500,000 species of beetles on earth and none of them are intelligent, so perhaps intelligence is not an evolutionary advancement but merely an accident. An emergent property is a collect property among a group, such as something simple like migrating patterns. So while geese may not be considered an "intelligent" form of species, they may have a form of intelligence because they have the common property of migrating together.
Why do radio wavelengths work as the best way to communicate with potential extraterrestrials?
Radio spectrum has less noise than other spectrums, so the signals don't get scattered.
fermi paradox solutions
S1 they're visiting today S2 they visited in the past S3 they are us S4 the zoo hypothesis S5 indirect theory (they keep us because we product info) S6 planetarium hypothesis S7 they are god
Is it possible for a person with a 70-year life span to travel farther than light travels in 70 years? Explain.
Since time for the moving person slows down, a person traveling at speeds near the speed of light to travel several times farther than 70 light-years during their lifetime. To them, the trip still seems like 70 years, but relative to us (at rest), it might be several hundred years!
What is the Fermi Paradox, and explain fully three "answers" to this paradox and the pros/cons of each being the "right" answer.
The Fermi Paradox is the apparent contradiction between the high probability extraterrestrial civilizations' existence and the lack of contact with such civilizations. 1. They were here and they left material evidence: UFO's, alien artifacts, ancient astronauts. Pro: some ancient artifacts cannot be fully explained. Con: Evidence for aliens is non-existent. 2. Zoo scenario: the aliens are here and they are keeping us in a well-designed zoo or there is a treaty preventing concat with young races. Pro: it would explain why we are in the dark about their existence and why we have had no interaction with them. Con: this scenario can not be tested. Only one ET could break embargo 3. ET has no interest in communicating with lesser intelligences. Pro: It would explain why no aliens have contacted us. Con: with millions of possible civilizations, some of the extraterrestrial ones would be interested in our species.
What is the habitable zone? Explain how recent discoveries of life in extreme environments (e.g. black smokers, worms in methane ice, etc.) has affected our view of a habitable zone. What is a "gravitational" habitable zone?
The area around the system¹s star where liquid water would be found on the surface is referred to as the habitable zone. Discoveries of life in extreme environments had shown that life doesn¹t require sunlight. A gravitational habitable zone is an area where life could survive because of heat generated by gravitational or tidal forces.
What is the Fermi paradox, and what is three possible responses? (add two more)
The idea that if there were technologically advanced aliens out there, then they should have visited us by now, or we should have seen some evidence of them. In response to this, many scientists say that the absence of evidence isn't evidence, meaning just because we doesn't mean they aren't there.
What are the three ingredients necessary for life? What is a possible source for each ingredient?
The ingredients are energy, water, and organic molecules containing carbon. A possible source for energy is the sun. The possible sources for water and organic molecules are molecular clouds.
How and why does the lifetime of a civilization relate to the probability that we are not alone?
The lifetime of a civilization relates to the probability that we are not alone in that the longer life lasts, the more likely there will be an "overlap" civilization, giving the chance for discovery and encounter. The longer a civilization lasts, the more likely they will encounter another civilization.
What are the three ingredients necessary for life? What is a possible source for each ingredient?
The three ingredients necessary for life are energy, water, and organic molecules. For energy, a likely source could be the core of a planet or the interior of a volcano. The hydrogen compounds within an interstellar cloud could be the source for water. Lastly, molecules formed in clouds and other materials during the formation of the solar system could be the origin of organic molecules.
What does it mean to say that we are communicating with extraterrestrials already? What do our signals sound like at various distances from the Earth? Explain.
We have been inadvertedly sending radio signals into space for decades. THe farther away from earth the older the radio signals are. For example planet A is closest to earth and can hear 90s music on our radio while planet B is farther from earth than planet A an can heart 50s music over the radio signals.
UFO's have been seen for many years, describe three common object/effects that are commonly seen as UFO's
Weather balloons: they can be quite large with a highly reflective material and can fly at altitudes as high as 120,000 ft where winds aloft can sometimes push them along at hundreds of knots, giving them the illusion of moving at high speeds. Meteors-unlikely to be mistaken for a UFO. A fireball, or brightly lit meteor observed at close range, is very bright. They last several seconds, appear to split into smaller pieces and abruptly disappear from sight. As observers would observe, "zooming away at great speeds." Aircraft- blimps, helicopters, and VTOL aircraft. Frequently mistaken because of their unconventional flight patterns; their ability to hover, then suddenly fly away.
bandwidth
determines how much we can pick stuff up; how much of the frequency you want to pick up (want to pick up signal not noise)
FM vs AM
frequency modulation FM amplitude modulation AM
principle of mediocrity
if it happened here it can happen anywhere
special relativity
mass will be greater time seems to slow for that person no two events can occur simultaneously
difference scenarios of the drake equation
optimist - the principle of mediocrity conservative pessimist
fermi paradox
physical - space travel is difficult sociological - chosen not to visit temporal - have not had time to reach earth past visits - they were here, but we missed them
gravitational habitable zone
tidal forces to create heat and foster the creation of liquid waters
frequency
upper frequency - lower frequency/ bandwidth
In science fiction, many adventures are dependant on a "Warp drive". What is being warped?
warp space to move faster than the speed of light
