MIT Physics News Spotlight
Discover Science Interview with Sara Seager
Sara Seager, Professor of Physics; and Ellen Swallow Richards Professor of Earth,
Atmospheric, and Planetary Sciences
Could you explain string theory?
String theory is a mathematical description that aims to be the "theory of everything" for physics. In other words, string theory aims for a unified physics description of the very small, such as atoms, to the very large, such as black holes.
What are the different theoretical ways we could get space vehicles to achieve the speed of light or faster?
No one knows how to reach the speed of light, and certainly nothing can go faster than the speed of light according to the current understanding of physics. That said, popular theories on how space vehicles could approach one tenth the speed of light include matter-anti matter engines, nuclear-pulsed propulsion, and laser sails. A new group of space engineers want to see refueling from low-Earth orbit, so that precious fuel is not wasted getting out of Earth's gravity hold.
If neutrons are electrically neutral, what keeps them attracted to and held in the nucleus? If they're neutral, why can't they just float along freely?
Neutrons are held to the nucleus by a force called the strong interaction. This force overwhelms the electromagnetic forces (the forces that hold electrons and protons together) at small distances — distances as small as the size of a nucleus.
Do you think it's possible for life to evolve in the atmosphere of Jupiter or Saturn?
It would be tricky for life to survive and evolve on Jupiter or Saturn largely because of the very high temperatures beneath the atmosphere. Jupiter and Saturn have no solid surface and the atmospheres extend deep into the planet interiors. Not too far down from the top of the planet atmosphere the temperatures get too high for complex molecules that form life. Therefore, while life might be postulated to exist on water droplets inside clouds, long-distance downdrafts would bring the material down in the planet to the high temperatures that would destroy life.
Do you think the adaptation and evolution of life would be able to keep up with the relatively rapid changes of those super earths?
Definitely. Life can adapt very fast when there is a very strong push to adapt to a new environment. The best examples from here on Earth are animals' adaptation to what humans do. We have taken tomatoes from being small, bitter, poisonous fruit about the size of strawberries to the tomatoes you see in the supermarket in about 200 years, just by selecting them really strongly for being bigger and tastier. Bacteria can adapt even faster. Generally, the rate of adaptation depends on the number of generations that have passed, not the length of time, so bacteria (reproduce every 30 minutes) can out-evolve people (reproduce every 30 years).
Since we have been pumping radio waves out for over 50 years into space, when do we hope to hear back from our nearest neighbor?
If our nearest neighbors — three stars in the Alpha Centauri system at 4.2 light years away — have intercepted our radio signals they should have responded already (4.2 years there, 4.2 years back). The next 10 nearest star neighbors are out to about 10 light years, and we also should have heard back. Beyond that, the radio wave signal decreases as it spreads out such that civilizations more distant might not be able to detect our radio waves at all.
If we are made from a Super Nova, what happened to the space dust and the possible White Dwarf?
Some of the space dust from a super nova explosion is actually still floating around in space. White dwarfs do not form after supernova explosions; only neutron stars or black holes form. In addition, the phrasing "we are made from supernova" means that any element heavier from iron was created in a star and dispersed by many supernovae, not just one.
Reprinted with permission of MIT News.