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Why Don't We Just Go There? A Teachable Moment
Dec. 04, 2003by Edna DeVore - Deputy CEO
Captain Picard and his crew captured the minds and hearts of many viewers as they explored the universe visiting extrasolar worlds and meeting exotic aliensall without doing harm. Warp speed made it possible. Ah, to travel at warp speed. Doesnt everyone want to be able to command a space ship to leap across the galaxy, to issue the order: "Make it so!" I sure do, but so far, no one beyond Hollywood has figured out how.
There may be numerous intelligent civilizations on planets throughout our galaxy. Thats the hypothesis that drives SETI research. We seek evidence of extraterrestrial technology using optical and radio telescopes to search for signals that emanate from other civilized worlds. These places are far, far away. But, when you discuss the search with school children, often they simply ask, "Why dont we just go there?"
Often, the best teaching and learning occurs when a good question is asked, and explored. The easy reply is that "its too far away." What does "too far away" mean to a sixth grade student who imagines standing on the deck of the Enterprise, searching for intelligent life on distant worlds? Her parents may have said the same thing about going to Disneyland for the weekend. In both cases, the travel time doesnt merit the trip. So, can the issues around space travel to distant worlds be made "real" or at least comprehensible when she asks, "Why dont we just go there?"
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Around the star Upsilon Andromedae, astronomers found the first multiple-planet system outside our own. The planets are all much closer in than Jupiter and larger than the inner planets of our solar system. |
Whether in classrooms or homes, good teaching and learning connects with shared experiences. For example, in thinking about traveling to other worlds, simply start from home and calculate the travel time to Disneyland, the Moon, Mars, the nearest star, and the nearest extrasolar planetary system. Go from the familiar to the unfamiliar. Pick some commonly experienced modes of transportation: walking, riding a bike, driving a sports car, flying in a jet, piloting a space shuttle, or hitchhiking on a planetary probe like Pioneer 10, Voyager I or Voyager II. Then consider the time it takes to get to the destination. The Pioneer and Voyager spacecraft are the first human-launched vehicles headed out of the solar system toward other stars, and they are barely beyond Pluto after a couple of decades.
The problem is timejust like driving around in California looking for Disneyland. Its not how far; its how long it takes to get there that matters the most. For example, if I walked to Disneyland (365 miles from my home) at a rate of 25 miles per day, Id get there in about 2 weeks. If I ride my bicycle for 100 miles per day, I could get there in less than 4 days. I can drive there in my car in just over 6 hours. Or I can fly there in about 1 hour. Disneyland is a real destination by ordinary means of travel.
What about the Moon? The Apollo astronauts took a couple of days to get there in a spaceship. The Moon is about 240,000 miles distant. Children walk a lot. They understand how long it takes to walk to school. If they walked to the Moon as I did to Disneyland, they would be plodding along for about 9,600 days (over 26 years) one way. Flying in a commercial aircraft (average of 500 miles per hour), the trip is only 480 hours (20 days)again, one way. The space shuttle is not designed to go to the Moon, but if it were, it could get there in just over half a day at its average speed of 17,580 miles per hour. A beam of light, or a radio signal, takes less than 2 seconds to travel from Earth to Moon. And, the Moon is the closest natural object to the Earth, barring the occasional asteroid. Everything else is farther away.
Now, consider traveling to another star. The nearest star system is Proxima Centarui, about 4.2 light years away. A light year is about 5.88 trillion miles5,880,000,000,000 milesthe distance that light travels in on year at a speed of 186,000 miles per second. That puts Proxima Centauri about 25 trillion miles away. At space shuttle velocity, youd be whizzing through space for just over 162,000 yearsone way. If you doubled the speedabout the velocity of Voyager as it leaves the solar systemthe travel time would drop by half to only about 81,000 years. If we want to explore a known planetary system, we have to look farther out. The 110 known extrasolar planetary systems are found around relatively nearby stars; the closest is Epsilon Eridani at just over 11 light years away. It has a couple of planets, but its not a comfy place for life. A more interesting place to visit would be Upsilon Andromedae, a solar-type star 44 light-years away that boasts 3 planets. Now how long would that trip take?
At first glance, it appears that the problem is our technology: We arent going fast enough. While true, there is a something more fundamental that, so far, high-powered physics hasnt cured. The problem is that outside of Hollywood, we havent figured out how to violate the universal speed limit, the speed of light. We cant travel faster than light, or even close to light speed. So whats the fastest thing in the galaxy? A beam of light. But even light takes time to travel to Earth from distant stars. A radio signal (a form of light) from a star 50 light years distant takes 50 years to traverse the space to Earth. So, even information encoded in electromagnetic energy (e.g. light, microwaves, radio, UV, etc.) takes time to travel through the universe. And for particles of matter (atoms, humans, spacecraft) that travel at much slower speeds, it takes a lot more time.
Travel time is at the heart of the simple answer to "Why dont we just go there?" But, as we work toward inventing spaceships that travel to the stars on generations-long trips, or even come to new understandings of physics that allow for quicker means of space travel, information arrives continuously at our telescopes from all across the distant universe. It comes here from near and distant stars in our own galaxy, and the galaxies beyond. For astronomers, light of all wavelengths is information to be collected and analyzed, to be sifted for clues about distant worlds, and to be searched for evidence of distant intelligence civilizations. We dont have to "go there" to discover other worlds, other beings. We simply have to seek out their signals amongst the steady stream of data that arrives daily at the speed of light.
Project Haystack Project Haystack: The Search for Life in the Galaxy is a SETI Institute teaching guide that explores the question of searching for evidence of life in our galaxy, the Milky Way. Are there any intelligent civilizations out there? Where might they be? If they are out there, how would they communicate with us and what would they say? How would we respond? Project Haystack is an investigation of these questions and others now being asked by scientists trying to determine our place in the cosmos. Through hands-on activities, middle school students learn about the scale and structure of the Milky Way galaxya cosmic haystack. They build a basic radio, and study SETI science by using simple astronomical tools to solve some of the problems of sending and receiving messages beyond our solar system. Visit the SETI Institutes web site to download Calculating Stellar Travel Times, a fun lesson that asks students to explore the question, Why dont we just go there? Its the sample lesson for Project Haystack. |