When Lightning Touches Water

Why is it necessary to get out of the ocean during a storm? A lifeguard tells everyone to get out of the water immediately, but it shouldn’t matter because everyone is already wet. The answer is lightning. 

A flash of lightning, which has about 300 million volts and 30,000 amps, is deadly to humans (BBC News, 2014). Lightning occurs during storms when there is enough wind to cause charges inside clouds to separate. Electrons in the cloud peel off water particles, leaving the water particles positively charged and joining other particles to make them more negatively charged. Positive charges start to gather near the top of the cloud while negative charges gather near the bottom (Cappucci, 2022). The separation of these charges creates both an electric field between the negative and positive charges in the cloud, and between the negative charges in the cloud and the positive charges on the ground. The positive charges on the ground attract the negative charges at the bottom of a cloud, and they start to move toward each other. Once the charges from the ground and the cloud meet, the negative charges start to flow downward and an electric current is shot up to the cloud along the path that the negative charges came from (How Lightning, n.d.) For this to happen, the air has to reach 3 million volts per meter. At this point, the charge is no longer contained and creates a path downward as it continues to heat up the air around it. The charge moves in what is called a “stepped ladder” formation, a direct, fractal shaped path (Cappucci, 2022). The current is what we see as lightning. Because it happens so fast, it looks like the lightning is coming from the cloud, but it is actually coming from the ground. This type of lightning is most dangerous, but another type of lighting, that which occurs between the negative and positive charges within a cloud, happens much more often. Fascinatingly, lightning can also occur in circumstances beyond storms. Other environments, like dust storms, forest fires, or volcanoes can cause a similar motion between charged particles, leading to lightning strikes. (How Lightning, n.d.). 

The physics of lightning is already complicated, but its interaction with water adds another layer of complexity. Lightning hitting the sea is rare as most lightning strikes are on land. This is because over the ocean the air contains sea salt, which attracts charges but turns the charges into heavy droplets of water before they can come down as electric charges (Balthazaar, 2023). Using satellite technology, scientists have observed the patterns of lightning when interacting with oceans. They concluded that lightning flashes over the ocean are stronger, longer, and brighter than those over land. The experiments found that the greater the concentration of salt, the brighter the lightning. Lightning strikes on water are only about 10% of all strikes worldwide ("Why Is Lightning," 2020). However, once it does strike water, it spreads out because salt water is a good conductor of electricity. Because of this, objects in the ocean like fish or boats can get electrocuted (Ocean Today, 2011). A study in the Journal of Atmospheric and Solar-Terrestrial Physics found that the intensity of lightning over the ocean is directly correlated to the concentration of salt in the water. In other words, when salinity increases, because salt is a better conductor, lightning strikes are brighter and more intense.

Lightning is as interesting as it is dangerous. Despite being more likely to strike land, lightning striking water can be more risky out at sea. While electric fields and currents are not discussed day-to-day, understanding the impact of lightning on water and how it works can help to save people’s lives. Luckily, lightning fatalities are decreasing because of increased awareness and better weather-predictability. Nevertheless, it is important to be aware of how lightning behaves in order to stay safe.

References

Balthazaar, D. (2023, January 16). Lightning at Sea? Science World Scholastic. Retrieved December 19, 2024, from https://scienceworld.scholastic.com/issues/2022-23/011623/lightning-at-sea.html?language=english

Cappucci, M. (2022, August 5). What happens when lightning strikes -- and how to stay safe. The Washington Post. Retrieved December 23, 2024, from https://www.washingtonpost.com/climate-environment/2022/08/05/lightning-thunder-thunderstorm-facts-safety/

How lightning works. (n.d.). Canada.ca. Retrieved December 19, 2024, from https://www.canada.ca/en/environment-climate-change/services/lightning/science/how-lightning-works.html

When Lightning Strikes [Video]. (2011, July 5). Ocean Today. https://oceantoday.noaa.gov/lightning/

Who, what, why: What happens when lightning hits sea? (2014, July 28). BBC News. Retrieved December 23, 2024, from https://www.bbc.com/news/blogs-magazine-monitor-28521789

Why is lightning more intense over the oceans? (2020, March 31). Journal of Atmospheric and Solar-Terrestrial Physics. Retrieved December 23, 2024, from https://www.sciencedirect.com/science/article/abs/pii/S1364682620300766

The Physics of Bird Flight

The process by which a bird takes flight is majestic. However, it can be explained by simple physics – it is a matter of the bird's thrust and lift forces overcoming gravity and friction. Its flight begins with a conversion of the stored energy in its muscles into kinetic energy. Newton's Third Law, stating that every action has its equal opposite reaction, explains how the bird's motion gets it off the ground once it starts flapping. Air pushes back on the bird's wings flapping with an equal opposite force to create enough lift to push it upwards. Wings have to return to their initial position in order to repeat the flapping motion, but they are hinged and can change the angle of attack on the up stroke to reduce the wing's surface area and create less opposite force pushing down (Obermeier, 2022).

Once a bird has ascended, it transitions from a flapping motion to a gliding one. This position, assisted by the bird's biological construction and the forces of physics, is called airfoil, and is what airplanes and boomerangs are modeled after. Wings have less surface area on the top with tapered back ends, and their feathers are secured together by hooklets that help them hold this airfoil position comfortably (Obermeier, 2022). The air above wings stretches out, meaning there is lower air pressure above the wing than below it. Since air of higher pressure always moves towards air of lower pressure, the air under the wings moves upward and lends the bird lift even when its wings are still. Birds' bodies are also notably light-boned and streamlined, making them extremely aerodynamic, which helps mitigate frictional drag acting against their thrust and lift (UNC, 2010).

References

Obermeier, L. (2022, September 19). The Physics of Flight. Schlitz Audubon Nature Center. Retrieved November 5, 2024, from https://physicsofflight.webnode.page/the-mechanics-of-flying/

UNC Chapel Hill. (2010). Physics Of Flight: Birds. Retrieved November 5, 2024, from https://physicsofflight.webnode.page/the-mechanics-of-flying/

World Wildlife. (n.d.). Bird Flying [Photograph]. Stock Snap.

     https://stocksnap.io/photo/bird-flying-M2XM8CRVNI

The Cosmic Distance Ladder: How to Measure Distance in Space

How do astronomers determine how far away something is in space? People often take for granted the ability to tell how far away something is. If it is not clear to the plain eye, one can use rulers or other tools as reference points for measurement. In space, however, it is much more difficult to tell. Knowing distance is incredibly important since it is impossible to interpret data to see if, for example, a star appears brighter because it is more luminous (the actual amount of light it is emitting) or is just closer to the planet from which it is being observed. However, despite the minuscule amount of information astronomers can collect about objects in space, amazingly they do have a method of determining their distance. This method, or rather, a set of methods is called the cosmic distance ladder. It is a ladder in that the technique used changes depending on the object's distance which is split into multiple rungs. 

The first rung on this ladder is the parallax method. To understand this method,hold up a finger in front of you and close one eye, then switch which eye is closed. Your finger probably appeared to move a little. This happens due to the different angles from each eye to your finger shifting where the background appears relative to your finger. This can be applied by astronomers on a larger scale by using the movement of the Earth around the sun. Astronomers can measure the change in angle from the earth to an observed star between two opposite days of the year. With this data astronomers can make a triangle with the distance between Earth’s position A and B serving as the base, the measured angle being the opposite angle, and then can solve for height, which is the distance. Yet this method does have a major limitation: angles measured this way even for close stars are measured in fractions of arcseconds (1/3600 of a degree), and for farther stars that need measurements more precise than 0.01 arcsecond this method becomes ineffective. For objects where the effects of parallax become unreadable due to distance, astronomers must move to a higher rung in the ladder. 

The next two rungs consist of standard candles, objects of which the distance can be determined by observing their properties and then can be used as a landmark to measure the distance of other objects around them. Cepheid variable stars, for example, have a strange pulsating effect by which they appear to become brighter and dimmer. Prominently, the period between their brightest and dimmest points can be used to accurately determine their luminosity, or how much light they actually emit. With their luminosity and how bright they appear from Earth measured, their distance can be quite easily calculated with the equation b=l/4d2. Once the distance of the cepheid variable star is determined, the relative distance of other objects in formations with them can be inferred. Unfortunately, this method becomes unusable if the variable stars are too far to see, at that point, a brighter standard candle is needed.

Type IA supernovae are caused when a star that died but was not massive enough to become a supernova gains enough mass after its death (ex. by absorbing another star) to have a supernova anyway. These supernovae occur with very similar luminosity which can be more precisely determined by measuring the wavelengths of light emitted. The luminosity can then be used to determine distance in the same manner as before, so the supernova can be used as a standard candle. However, some objects are so far away, such as distant galaxies or galaxy clusters, that even the supernova explosions cannot be seen. 

For the farthest objects that astronomers can observe, the final rung is used: redshift in relation to the expansion of the universe. Redshift is the phenomenon of light waves becoming stretched out as the universe expands between them causing them to have a higher wavelength and appear more red. Since the vast majority of the mass in galaxies, and the universe, is hydrogen, the wavelength of light coming from far away galaxies can be compared to the wavelength of light observed when light passes through hydrogen on Earth, and the redshift of the galaxies can be determined. This can be compared with the Hubble constant, the rate of expansion of the universe, to determine distance. However this method is not only on the highest rung because it can be used for the farthest objects, but also because it is used only if none of the others are applicable due to it being the least accurate. This is not to say that is not accurate, however, it lacks the degree of precision of the others due to several factors, most prominently the debated value of the Hubble constant, with estimates ranging from 68 km/s/Mpc to 72 km/s/Mpc. Other galaxies can also cause minor interference due to their gravitational pull; however, for father objects, this affects the redshift to a lesser extent. 

Because the ability to determine how far away things are relative to each other is often taken for granted, in the great cosmic void it takes creativity to find ways to find where objects in space actually are. The methodologies contained in the cosmic distance ladder manage to help overcome this challenge in astronomy and allow astronomers to more deeply understand what they are looking at.

References

The American Association of Variable Star Observation. The Cosmic Distance Ladder. Aavso. https://www.aavso.org/cosmic-distance-ladder  

https://www.uwa.edu.au/science/-/media/Faculties/Science/Docs/Explanation-of-the-cosmic-distance-ladder.pdf

Strand, K. A. (2024, December 6). parallax. Encyclopedia Britannica. https://www.britannica.com/science/parallax 

https://www.atnf.csiro.au/outreach/education/senior/astrophysics/variable_cepheids.html 

This page no longer exists for whatever reason what should I do 

Preuss, P. (2015, June 1). Standard-candle supernovae are still standard, but why?. Berkeley Lab News Center. https://newscenter.lbl.gov/2014/03/03/standard-candle-supernovae/

Impey, C. (2012, September). Relating redshift and distance. Teach Astronomy. https://www.teachastronomy.com/textbook/The-Expanding-Universe/Relating-Redshift-and-Distance/ 
Warren, S. The Hubble constant, explained. University of Chicago News. https://news.uchicago.edu/explainer/hubble-constant-explained 

Gravitational Waves

Imagine someone cannonballs into a pool, what happens? Ripples are created and run through the entire pool. Now instead of a pool think about spacetime, and instead of someone canon-balling, think about two major stars colliding. Those ripples are gravitational waves. First discovered in Albert Einstein's general theory of relativity, gravitational waves are the disruptions in space-time that two accelerating objects create. These disruptions take place in the form of waves of space-time that disseminate in all directions away from the source. Gravitational waves travel at the speed of light and have many different causes, including black holes, supernovas, and colliding stars.

The first proof of gravitational waves was found in 1974 when two astronomers reported a change in the radio emissions from two stars and that the stars were getting closer and closer to each other at the rate of general relativity, proving Einstein’s theory. In 2015, scientists detected gravitational waves themselves from a collision of two black holes for the first time using an instrument called LIGO (Laser Interferometer Gravitational-Wave Observatory). While the collision of two black holes that LIGO detected happened 1.3 billion years ago, the ripples didn’t make it to Earth until 2015. LIGOs detect the squeezing and stretching that gravitational waves create. Each LIGO machine has two arms that are around 4 kilometers long, and a gravitational wave will cause the length of the arms to change marginally. The LIGO machine uses lasers, mirrors, and other tiny instruments to detect these tiny changes. While gravitational waves are initially very strong and dangerous, by the time they reach Earth they are much smaller. This is because the waves get smaller and smaller the farther away they are from the source, just as the ripples made by the cannonball decrease by the time they reach the edge of the pool. In fact, by the time the gravitational waves hit Earth from that collision of two black holes 1.3 billion light years away, the amplitude generated was 10,000 times smaller than the nucleus of an atom. While gravitational waves don’t have a large effect on Earth, they give scientists a new way to explore the universe. Scientists are able to learn more about black hole mergers, supernovas, and the birth of the universe all through gravitational waves. 

References

What are gravitational waves?. Caltech. (n.d.). https://www.ligo.caltech.edu/page/what-are-gw 

NASA. (2020, June 4). What is a gravitational wave?. NASA https://spaceplace.nasa.gov/gravitational-waves/en/ 

Planet 9

Evidence found by CalTech mathematicians suggests that there may be a ninth planet deep in the solar system. The research was published in January 2015 by CalTech astronomers  Konstantin Batygin and Mike Brown. Batygin and Brown have nicknamed the theoretical planet “Planet Nine,” however official naming rights are given to the people who actually discover the planet, so it is temporarily being referred to as “Planet X.” 

While this is just a theory, it could explain abnormal orbit patterns of smaller objects in the Kuiper Belt. The Kuiper Belt is a region far beyond the orbit of Neptune filled with icy debris. Astronomers who study the Kuiper Belt have noticed that dwarf planets and other debris follow orbits that cluster together, and the study of these abnormal orbits led some astronomers to hypothesize an additional planet beyond Pluto. Considering their estimations, the gravity of the potential planet could describe these unique orbits in the Kuiper Belt.

Planet X is believed to be large. It is speculated to be around the same size as Neptune or Uranus and 10 times the mass of Earth. The planet is also hypothesized to have an extremely extended orbit. It would be around 20 times farther from the sun compared to Neptune, and one complete revolution would take around 10,000 to 20,000 years. For reference, Neptune's orbit takes around 165 years to complete, and Earth’s is one year. 

This theory is based on modeling and simulations, rather than observation. The next step is exploration - searching for the planet. Astronomers, including Batygin and Brown, will use tremendously powerful telescopes to try and spot Planet X. 

References:

 NASA. (n.d.-b). Hypothetical planet X. NASA. https://science.nasa.gov/solar-system/planet-x/