April 26, 2006

1. David Weaver: This is a fabulous effort! There are a few things missing and a few other minor comments. The whole biological (food, waste, air, etc.) issue is missing. Andrew Duncan Katherine Colla Joe Kempton April 26, 2006

2. Another Presentation

3. Project Description The object of Project 3 is basically to design a means by which the Physics Phreaks can travel to a planet in orbit around Alpha Centauri A. The group must vacation there for a year, and then come back to Earth with souvenirs. We need to take into consideration our means for living on a ship in order to live comfortably (or at all) for the amount of time we are going to be traveling. This would include propulsion (based on ship chosen), fuel, food, water, air, and relativistic effects. Upon deciding what type of ship the Physics Phreaks are going to use on their voyage into outer space, they must apply the relativistic effects in order to figure out how long they will be traveling. The ship will be traveling at a constant acceleration until they reach the midpoint of the journey, where they will begin deceleration until they reach their destination. We must take into consideration the effects, along with the known distance from earth to the star to determine the length of the trip.

4. Timeline The following Timeline is a representation of the hard work and dedication exemplified by the group, the “Physics Phreaks”. Wed., March 29th – We were introduced and reviewed P3 Mon., April 3rd – Group Meeting #1: Discussed concepts of Project and brainstormed some ideas Wed., April 5th – Group Meeting #2: Decided on type of ship Mon., April 10th – Discussion of Project in class. Work on gathering information. Fri., April 14th – Meeting # 3: Struggled with math, only to find out we were wasting or time. Sat., April 15th – Research continues. Andy discovers Space calculator used for relativistic calculations ….Jackpot! Mon., April 17th – Picked David’s brain concerning Time Dilation Fri., April 21 – Meeting to begin TIM and create graphics Sat., April 22nd – Complete TIM for presentation. Mon., April 24 – Cover some holes in the TIM / Prep presentation.

5. Destination Alpha Centauri is located approx. 4.4 light years away. It has a mass of 2.17 x1030 kg, a diameter of approx. 7.73 x 108 m, and a surface temperature of 5442 oC Alpha Centauri also known as: Rigil Kentaurus located in the foot of Centaurus Constellation

6. Final Destination Being that Alpha Centauri is much too hot to land on and explore, we are going to attempt to land on one of the three planets believed to be orbiting the star. The planets are named Curley, Moe, and Larry. We are planning to land on Curley, as it is the closest planet to Alpha Centauri, which will make it easier to observe. An exploratory pod, Mini C3 will be our means of travel from space to Curly.

7. Voyage Vehicle The Physics Phreaks have determined that the best interstellar travel can be accomplished using a solar sail, sometimes referred to as a light sail.

8. How does a Solar Sail work? Solar sails are composed of large flat smooth sheets of very thin film, usually covered with a reflective coating, and supported by lightweight structures attached to a central spacecraft (where we reside). The sails use aluminum Mylar (a strong, thin polyester film), which is very large and thin, not to mention hard to work with. The result is a huge mirror. The force generated by the sun shining on this surface, which is created by transferring the momentum from the light particles (photons), propels the object forward. This may show a tiny force, but this snail-like acceleration results in the achievement of velocities large enough to cover immense distances without using fuel. David Weaver: I thought you were going to accelerate at 1 g which isn’t quite snail-like, is it? During our voyage, we can change the angle of the sails to better propel the spacecraft toward the desired direction similar to wind pushing the sails of a sailboat.

9. CENTAURUS 3 We have named our Voyage Vehicle CENTAURUS 3 or C3. It was constructed in space over a span of many years. It consists of various materials, including conventional light sail film (mylar) with a thin film aluminum layer deposited on one side. The main body of the ship (center), consists of living quarters, a place to harvest food, and an exploratory vehicle, called MINI C3.

10. C3 Stats • Sail Configuration: Circular Spinner • Sail Information • 3600 m diameter • Area: 10,000,000 m2 • Total mass: 1000 kg • Top speed: 0.95 c

11. Lorentz Contraction Lorentz contraction is the shortening of an object along a direction of motion as speed approaches the speed of light. This contraction can be measured by both the observer, who is at rest with respect to the moving body, as well as the observer from inside the moving body with respect to objects outside the moving body. For instance if we had a meter stick on the side of the road and a car traveling along the road at a relativistic speed of .95 the speed of light, the measured length of the meter stick from inside the car would be .312m or 31.2cm. Likewise an observer on the sidewalk would measure the car at 31% of its at-rest length.

12. Contraction of space The Lorentz contraction can help us understand how distances contract at relativistic speeds. As C3 travels through space approaching a velocity near the speed of light (0.95c), our measured distance in space from us to Alpha Centauri contracts to give us a fraction of the original measured distance from earth. This changes our actual traveling distance from 4.16X1016m to 1.30X1016m, almost 1/3 of the original distance. This contraction would be correct if we maintained a constant velocity of 0.95c throughout the entire mission. For our mission we only reached 0.95c at the midpoint, therefore the distance will be incorrect for our mission.

13. Time Dilation Time dilation is the phenomenon where the observed rate of time from an observer's point of view is different from the rate of time recorded by an object with respect to its velocity. The following graph illustrates how insignificant the effect of time dilation is for velocities as great as half the speed of light, but how dramatic it becomes as we draw closer and closer to the speed of light. By the time we reach .90 the speed of light, for each day on board, two and a quarter days pass for an observer located on earth. If we continue to accelerate to 0.99999999999999 c, for every day on board, nearly twentythousand years pass for the observer on earth. David Weaver: You should consider how long your entire trip took for you and for earth-bound family and friends (and teachers).

14. Distance to Star Due to relativistic effects, you can see the distance change for observers on Earth versus travelers in C3. The graph also shows the difference in time. David Weaver: This would be a really good place (or nearby) to invoke one of the postulates of the Special Theory of Relativity: the constancy of the speed of light. If you divide the total distance by the time, you get the same average velocity in each case.

15. Velocity vs. Time It is important to mention that our data is a bit flawed based on the realization that our max velocity(0.95 c) is only reached at the midpoint of the mission. David Weaver: I did provide y’all with the Excel file to figure out the actual (?!) information. Please consider doing a couple of new slides with the corrected (?!) information as errata sheets that you can place at the end and refer to in the main presentation (like here).

16. Acceleration vs. Deceleration For the first half of the voyage we will be accelerating at one G or 9.8m/s2. For the second half of the voyage we will be decelerating at a 9.8m/s2.

17. Aberration of Light The effect of aberration describes how accelerating at relativistic speeds that the photons from these stars come in from all directions into the frontal view. We can see how the whole field of view seems to shrink in the direction of travel. Even photons from stars that we know are behind us come into view while traveling in a forward direction.  The pictures above show an example of the aberration of light aif you were going to travel to Orion.

18. Doppler Shift Image source www.astro.ucla.edu While we observe matter in space which enmities light that is moving away from us, we see light that has a longer wavelength than it had when it was emitted, causing that light to appear red. Also we can observe an approaching space matter and see light that is shifted to a shorter wavelength that would appear to be blue. Image source www.lcse.umn.edu

19. We captured this picture of Alpha Centauri as we were preparing to land on Curly.

20. David Weaver: As I will talk more about later, I’m giving a lecture at a national physics teachers meeting about project-based physics. I mentioned that I’ll be asking y’all to respond to a survey about project-based vs. traditional. I will also be asking those that are interested to answer a few questions on video to include in my presentation. But, be certain that this photo will have a prominent role in my presentation (it will likely be what is on the screen during the Q&A at the end). We wanted to have something to take with us to remind us of our journey and decided that a souvenir photo would be a good idea.

21. Credits Report Created By: Katherine Colla Andrew Duncan Joe Kempton Images From: Andrew Duncan Starry Night Pro Software Star Strider Software NASA www.astro.ucla.edu www.lcse.umn.edu Content based on: Relativistic star calculator- by Stephen R. Schmitt Solar Sail Mission Requirements document NASA A Relativistic Interstellar Traveller by Alexis Brandeker www.fourmilab.ch/cship/