Sunday, November 29, 2015

Mind/space/time-bending physics

Time and gravity are related in very interesting ways. Before learning about them, and doing research into it, it never occurred to me that they might be very fundamentally connected.

Objects with mass in the universe create warping of spacetime. In these warped regions, time runs slower, especially as you get closer to the center of the mass responsible. Other objects of mass tend towards these areas of slower time. The higher the mass, and therefore the greater the warping of time, the more intensely those objects are attracted to that area. This effect is known as gravity. In black holes, where spacetime is incredibly warped, objects are pulled violently in. Around the Sun the effect is not as extreme and so the pull that its mass creates is balanced by the centrifugal force of the planets orbits, keeping them carefully spinning around.

To give an idea of how incredibly dense black holes are, the .7in circle represents the size of the Earth if it were to collapse into a black hole today, retaining it's original mass.
Black holes are extremely dense, because they continuously pull in matter and compact it into infinity. Because of this density, time is warped large amounts as you approach the center of it. At its event horizon, time stops and gravity is so intense because of this that nothing can escape past that point, not even light. In Interstellar, this is why it cost them so much time to land on Millers planet. As the closest orbiting planet to the black hole, time slows down to seven years for every hour spent on its surface.

This time distortion can be measured even on a much smaller and more local scale. An atomic clock was sent up to 10,000km on a rocket, and radio signals were used to compare it to a clock kept on the ground. It was found that time flows by about 30 microseconds slower on the ground than at that altitude.

Because of the time difference between Earth's surface and its atmosphere, orbiting satellites must compensate in order to send accurate data. At 20,000 feet, time runs faster by 40 microseconds per day. For GPS triangulation to work, where signals are bounced off three or more satellites and the transmission time is carefully recorded to pinpoint your location, the satellites must convert the reading to "surface time".

Additionally, radio signals were sent to the Voyager missions as they orbited Mars. There was a discrepancy here as well. It took more time than expected for the signals to bounce back when they crossed closer to the Sun. Because radio waves travel at a constant speed, the only explanation is that the amount of space that they had to cross was a longer distance than what traditional methods would predict. Signals that passed closer to the sun were warped more than signals traveling farther from it.

This is also related to a phenomenon called gravitational lensing, where large masses cause light to bend around them. This allows us to see distant celestial objects that would otherwise be too dim or obscured by other bodies in our line of sight. It also sometimes causes multiple images of the same object to appear, at different points in time because of the difference in the distances the light traveled. In the case of Einstein's Cross, four distinct images of a distant quasar can be seen. Because of the time difference, when it went supernova scientists were able to watch it unfold four times over, over a period of several days,
 Hubble Space Telescope image showing the quadruple-lensed supernova

Because of the discovery of phenomena like this, we've come a long way in understanding what we're seeing when we look into the night sky, and how different forces in the universe affect each other. 


Saturday, November 21, 2015

Star Trek: sending things places really fast

The biggest issue in the plausibility of science fiction set in space is just the sheer distance that is being dealt with. Often, because it is such an obstacle to the plot, physics, in particularly relativity, are quietly cast aside. However, some creators attempt to tackle it in a way so that instead of directly violating known principles, they simply expand on currently theoretical concepts.

To support the rapid-action pace of Star Trek, a way to get from location A to location B in a timely manner is very necessary. If the crew of the Enterprise receives an emergency signal, they need to reach their target destination before the ship that sent the signal is long gone and whatever enemy that was threatening them is an extinct race. The series is set in the Milky Way, which is about 100,000 light years across. Traveling even a fraction of that distance at the speed of light would still see thousands of years passing from an outside perspective. The writers needed a way to get around this potentially huge plot hole while still maintaining a vague adherence to the laws of physics. Since they knew from the theory of special relativity that it's not possible to travel faster than the speed of light, they developed an alternative. Instead of the ship moving through space at an impossible speed, the ship pulls and bends space around it to reach its destination. This way, they can avoid the restrictions imposed by relativity. Relativity only applies to objects moving through space, not space itself. A theoretical "warp drive" would be able to contract spacetime in the direction of desired travel, while expanding it in the opposite direction. The ship, remaining stationary, can "warp" great quantities of spacetime around it to effectively "travel" immense distances fairly quickly.

The writers developed a system of "warp factors" to quantify this in terms of the speed of light:

Warp FactorNumber of times the speed of light
11
210
339
4102
5215
6392
7656
81,024
91,516
9.61,909
10Infinity

Even while using this highly theoretical method of travel, they imagined a limit for it, described as the impossible "Warp 10".

Is it possible outside of science fiction? NASA thinks maybe, eventually. Many scientists have done extensive research into it, as it would mean distances that were previously scientifically of the question could become possible. One such theoretical real-world equivalent that has been explored is the Alcubierre drive. Conceptually nearly identical to a warp drive, it has been proven to be mathematically sound, though that doesn't guarantee physical possibility. Initially, the calculation for it involved more energy than present in the observable universe, but has since been scaled down to about the energy equivalent of three solar masses, or around 3144 times the mass of Jupiter. 

A second technology that is necessary for the Star Trek universe to form a cohesive storyline is an ansible. When traveling distances of the scale allowed by warp drive, communication becomes an issue. Radio waves, which travel at merely the speed of light, would take the equivalent light years between ships or planets to be received. A distress signal could take tens or hundreds of years to reach its intended receiver even at many times the speed of light. This is circumvented by sub-space communication, with a device typically given the general name "ansible" in science fiction. An ansible could theoretically work by two methods. The first is by the creation of a "micro-wormhole", or a tiny shortcut through spacetime. Signals sent through this could reach their target in a fairly timely manner, depending on the location of the wormhole. The second option is through the phenomenon of quantum entanglement, where a pair of particles are "entangled" in such a way that a change in the state or orientation of one particle will affect the other, regardless of space or time. Measurements of the properties of entangled particles have found that they are appropriately correlated. For example, if one is spinning clockwise, the other will spin counterclockwise. Manipulating the spin of one would affect the spin of its counterpart, The particular usefulness of this is that messages could possibly be sent this way through a kind of binary system. At a delay of a hundredth of a percent of the speed of light, communication would be near-instantaneous. It has been argued that this would affect causality, and therefore would not be possible in practice, however predictions of the connection between entangled particles have been experimentally proven. It seems that the largest issue would be in developing meaningful communication through this method.

Sunday, November 8, 2015

Creation/Destruction of a Monster

Watching Fat Man Little Boy and Gojira back to back was an interesting experience, in the extreme contrast of both the style and moral positions. 

In Fat Man Little Boy, many of the scientists had the viewpoint that they were just doing their jobs, and were not responsible for any outcomes of the weapon that they create. This has a similar ring to it as the Nazi general's defenses during the Nuremberg Trials, that they were "only following orders", and therefore not responsible for the crimes they carried out. The scientists said that they simply carried out their assigned task, and what happened with the result was beyond their control.

Contrary, the scientist in Gojira took full responsibility for the weapon he created. He could have used a similar excuse, that he just discovered the method for developing the device, and was not liable for any uses it may be put to. Instead, he accepted ultimate responsibility and destroyed all knowledge of his research, including himself, so it could never be duplicated and used for more sinister things after taking down the monster. Unlike the american scientists, who could disassociate themselves from blame in their minds, he felt fully accountable for anything that it might be used for, even when out of his hands. 

However, if I were in the position of the american scientists, I feel as though it might not be quite as clear-cut as it seems from a broader outside view, like many things. By putting it on the executives who have the final decision of what application your research will have, you can easily personally relieve yourself of blame. The scientists probably realized at some level that what they were doing went against their morality, but rather than struggle with cognitive dissonance, they rationalized it to themselves so they wouldn't feel guilty. I can see how it would be exciting to be involved in something so monumental. In Fat Man Little Boy their awe at the massive mushroom cloud produced from the first major test demonstrates this; they were so caught up in the project that even seeing its power and destructive capability they were thrilled instead of horrified.

I can find other ways to rationalize it as well--if you turned down the opportunity because you were morally opposed to it, someone else would easily fill your place, and nothing would be different. Scientists, like many holders of technical jobs, are fairly replaceable. Someone will step up to the job, if not you, the next guy. And if it's going to happen regardless, it's almost like a cop-out to let someone else take your place just so you don't have to feel guilty. What if you could do a better job, make it safer?

It's scary that it is easy to think like this, because you are absolutely responsible for how your research is utilized. To not thoroughly consider the possible drawbacks and impacts is just careless. Unfortunately, many destructive things have been created by well meaning people. However, intent still doesn't factor into the outcome. And especially for the Manhattan Project, the scientists knew full well what they were developing and what it would be used for.

If I were a scientist and asked to take part in research that had weapons applications, I would like to say that I would absolutely decline. It isn't something that I could ever feel comfortable or good about doing. If it was my only career option, I would rather choose something that felt like I was affecting the world in a positive way to offset the people who chose the other path. 

Sunday, November 1, 2015

Global Climate Change: Yep We're Doomed

Global warming is an unnecessarily controversial issue. Many people look for any reason they can to deny it, on a range from accepting the data but believing it to be a natural part of the Earth's "temperature cycle", to outright choosing to think that the high ratio of scientists who support that humans are causing global climate change (97% is the figure popularly circulated) are somehow all in it together to create a giant conspiracy.

The most rational argument I've commonly heard is the one acknowledging that global warming is occurring, but it's not a "big issue" because it's a natural process. As my art history professor so eloquently said:

"Sure the Earth is warming a little. But, you are arrogant to think that humans could cause this. It is just a part of the natural cycle".
  
First - even if it was just a natural process, that doesn't automatically disqualify it as an issue of importance to humankind. However, data collected from ice and tree cores, as well as ongoing monitoring of aspects such as temperature, snowfall, rainfall, ocean surface temperature and deep sea currents, help put together a timeline of the earth's climate history.

What we can determine is that though there have been many periods of extreme temperature in earth's past--from ice ages to times when much of the planet existed as a tropical climate, there were always legitimate outside factors that contributed. The biggest of these is the effect of the Sun. The Earth's orbit goes through regular calculable changes which affect how long it is close to the sun, as well as what areas of the Earth are more exposed to it's heating effects. About every 100,000 years the Earth cycles through an elliptical eccentricity of orbit. The more elliptical the Earth's orbit, the more time it spends away from the Sun. Cycles such as these plunge the Earth into predictable temperature swings. There is no such thing as a "natural cycle" of temperature variation, there must be an external factor that's "forcing" the shift. At the moment, none of the historical factors line up. The Earth is not just happening to warm up--we are causing it.

Milankovitch Cycles Eccentricity, Obliquity Tilt, Precession w/caption


In just the last century or so....


However, we can go farther back than that:

Climate Forcing

GHG or greenhouse gas forcing, represented by the green line, has largely departed from the typical natural cycle of the past 800,000 years. This is not a natural event.


Over the past 100 years, we have been consistently increasing our production of these heat-trapping gases, such as carbon dioxide. Notice the correlation to the temperature index. It is extremely unlikely that the GHG forcing is being caused by anything other than humans. We are simply the only thing that has dramatically changed our output of these gases in this time scale.

Why does this upward trend in temperature matter? Well, at the moment we've been cozy in our coastlines for quite some time, but that might be changing soon


Glacial melt has been increasing dramatically recently, most notably since 2004. Though there is a regular melt-freeze cycle that normally balances the ice loss in the summers, the increase means that the ice can't be replaced fast enough. Additionally, as more ice melts, it triggers factors that only accelerate the process. One of these is the decrease in reflectivity--snow is extremely reflective, which partially shields the glaciers from the sun's energy. However, as the composition of the glaciers is changed by rapid melting, more of this heat is instead being absorbed as the reflectivity decreases. Another is meltwater--as the glaciers melt the runoff drains down and is actually creating a slippery layer between the ice and the land, encouraging parts the fragmenting ice shelf to slide into the ocean. The more these factors occur, the faster the ice melts and moves off the land, which only contributes back to them, creating a positive feedback loop. Because of this loop instead of sea levels rising at a constant pace, the rate is actually accelerating. Scientists estimate that by the year 2100 sea levels will rise as much as 23in, affecting millions of coastal populations. 

However, the strain of global warming won't be felt exclusively by these people. Rising temperatures and sea levels will also cause: changes in weather systems and frequency of extreme weather events, decrease in freshwater and water quality, land erosion, flooding from increasing evaporation, out of control wildfires and drought from over-dried land, food scarcity from affected agriculture, not to mention the ruin of the economy from all the damage to the infrastructure and massive loss of jobs and human life....

What can we do about it? Hah...well...it seems like really the best we can do is stop contributing to the speed of the process as much as possible. It's already been set in motion, we can only try to slow it down. 



Global warming amirite