The Light Barrier

1. State of technology for traveling near/faster than light TheLight Barrier By Michael Bryant And Laine Tennyson May 12, 2008 Modern Physics SRJC Background credit: http://www.rpi.edu/dept/phys/ScIT/InformationTransfer/reflrefr/rr_content/refraction_20.html

2. The obvious problem: “Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.”-Douglas Adams, The Hitchhiker's Guide to the Galaxy Fastest space craft humans have ever launched (New Horizons) would take 47000 years to reach Proxima Centauri (at 25000 m/s or .00833% c) We need to go much much faster unfortunately that’s no picnic

3. The other problem:Relativity • Relativistic effects make near light travel with conventional chemical rockets infeasible Using the above equation to graph the energy required vs. velocity to accelerate an object of the mass of the typical shuttle payload (~86000 kg) effectively illustrates this point PUSH ME! Background credit:http://www.scifair.org/images/ParticleTracks.jpg

4. Nuclear Propulsion • -Project Orion (1960’s, fission) • -NERVA (Nuclear Engine for Rocket Vehicle Application) (1963-1973, fission) • -Project Daedalus (1973-1978, by the Brit’s, fusion) • -Project Prometheus (2003-present) • Electric Propulsion • -Ion/Plasma Propulsion • -Hall Thruster • -Magnetoplasmadynamic (MPD) thruster • -VASIMER (existing technology, planned application in 2010) • Nuclear-electric Propulsion MPD Thruster Alternatives to Traditional Chemical Rockets “Orion Style” Nuclear Spacecraft images credit: http://www.daviddarling.info/encyclopedia/A/advanced_propulsion_concepts.html

5. Antimatter-Matter Annihilation • When matter hits antimatter the result is a huge amount of energy, • Only would need 10g to reach mars in 1 month • Unfortunately right now mass of antimatter is measured in atoms, not kg • Assuming industrial processes could be established to manufacture antimatter, significant technical challenges remain • Need to separate antimatter fuel from regular matter of the ship using magnetic storage rings. • Feed system needs to be separated magnetically as well • Magnetic nozzle is needed to direct energy away from ship in a controlled manner Credit: http://lpmpjogja.diknas.go.id/kc/a/animal/antimatter.htm

6. credit: http://www.nasa.gov/centers/glenn/research/warp/scales_prt.htm

7. Unconventional Propulsion • Solar Sails • Light has momentum, p=hƒ, solar sails take advantage of this fact. • Differential Sail • Similar to solar sail, however this uses a theoretical coating on one side that absorbs energy more than the other side, assumes there exists in space a constant background radiation that is constantly impinging on all sides of the sail. Diode Sail Solar Sail Differential sail images credit: http://www.daviddarling.info/encyclopedia/A/advanced_propulsion_concepts.html

8. More Propellant-less Ideas • Magnetic Sails • -M2P2 (Mini-Magnetospheric Plasma Propulsion, under study at University of Washington, Seattle, with NASA funding) • Beamed energy • -Like a solar sail but asymmetric radiation pressure is achieved by shining high powered laser light on the sail from earth • Interstellar ramjet • -Bussard Ramjet ( version of fusion rocket but gets reaction mass from interstellar medium) credit: http://www.daviddarling.info/encyclopedia/A/advanced_propulsion_concepts.html Magnetic Sail Bussard Ramjet credit: http://amygdalagf.blogspot.com/2005_08_21_archive.html

9. Faster Than Light Travel Lets first define what is meant by FTL http://www.wallpaperbase.com/movie-startrek.shtml • Misnomers • A shadow on a distant wall may move at faster than the speed of light. • Phase velocity of the interference of waves can move faster than c. • A laser on a distant object can go faster than light. • We will define FTL as sending information superluminally.

10. Hubble Effect • V=H*d Where H is Hubble's constant, and d is the distance between two objects • If you were if d>c/H then you would be moving superluminally away from the other object • Space time expands between all objects http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/FTL.html

11. EPR • Einstein, Podolsky, and Rosen thought experiment • Two particles (A and B) interact and spin, before moving apart in opposite directions • After a time, the z spin of particle A is measured and the x spin of particle B is measured so both spins on both particles are known exactly. • This violates Heisenberg's Uncertainty Principle, or the particles were able to communicate faster than light • There are explanations, and reasons why this is not FTL travel http://roxanne.roxanne.org/epr/einstein1.html http://en.wikipedia.org/wiki/EPR_paradox

12. Einstein-Rosen Bridges Commonly known as worm holes. • Bend space time • One theory says that negative energy would be needed to keep the worm hole open. • With sufficient bending any point in the universe could be right next to you • Einstein came up with the idea while trying to explain fundamental particles like electrons as space-tunnels threaded by electric lines of force. • A prediction of his findings was black holes. http://www.krioma.net/articles/Bridge%20Theory/Einstein%20Rosen%20Bridge.htm

13. www.phys.univ-tours.fr/~piotr/ www.zamandayolculuk.com/cetinbal/blackholesth.htm

14. Alcubierre Drives • Space stretches behind you and contracts in front of you, so you are constantly riding on a “downhill” slope. • How? In order to stretch space time like this you would need to be covered in a shell of negative energy. • Even if we could stretch space time like this it is still unknown whether or not you could surpass the speed of light http://en.wikipedia.org/wiki/Alcubierre_drive

15. Negative Mass • Negative mass could make Faster than light travel easy • The equivalence principle states that every object must also have a negative, therefore inertial mass and gravitational mass must also have a negative • Tachyons • Relativity states that no positive mass can be accelerated to the speed of light, but what about a particle of negative mass? The less energy it had the faster it would travel. These particles are called Tachyons. • Issues: Even if you could control a tachyon you might find it impossible to remove energy from it.

16. Proof of Negative Energy • The Casmir affect: • All fields even vacuum fields have fluctuations. • If you create a cavity (two metal plates very close together) in the vacuum then the vacuum fluctuations can resonate in between the plates, causing the plates to repel, or the can be out of resonance (negative energy density) causing the plates to attract. • The plates attract. • Duality: • The principle of duality predicts that if there is energy, there must also be negative energy http://physicsworld.com/cws/article/print/9747

17. Conclusion • Many ideas about space travel make it plausible to travel quickly and efficiently in space. • Propelling yourself to the speed of light remains impossible. • Some ideas of how to “cheat” the speed of light exist, but none of them are testable or achievable in the near future

18. Sources • http://www.nasa.gov/centers/glenn/research/warp/scales.html • http://www.quotationspage.com/quote/33085.html • http://en.wikipedia.org/wiki/New_Horizons • http://www.nasa.gov/centers/glenn/research/warp/ideachev.html • http://www.daviddarling.info/encyclopedia/A/advanced_propulsion_concepts.html