Spaceships are a favorite among science fiction authors, be it the Star Destroyers from Star Wars or the massive Covenant fleets from Halo, it’s incredible to think of vehicles that can travel through galaxies.
If we are just talking about sending things into space, we’re already great at that. In fact, there are over 10,000 satellites orbiting Earth right now, and increasing. We even have an International Space Station where astronauts can live for years if they wanted to.
The real challenge is building something that can take people further than Earth’s orbit and not be a one way trip. Theoretically we could launch someone into space and have them go further than anyone before, but they’re probably not going to make it back. Engineers and scientists are trying to tackle this problem and have made several space shuttle iterations in the past, like Discovery.
Right now, development is focused on Orion, a shuttle designed to take people further than anyone else before and a voyage past the moon is being planned.
While this isn’t nearly traveling at or above light speed like in the movies, it’s still incredible that we are on the verge of actually being able to travel to other planets. Once we can achieve that, we will only continue to expand the domains we can explore. The future of space travel is very bright.
Tides rise and fall twice a day on Earth, and this is mostly due to the Moon’s gravitational pull on Earth. The Moon’s gravity pull on the Earth’s bodies of water squeezing it towards the Moon. The opposite side of the Earth is also receiving high tides due to this reason. I used the word “squeezing” because while the area of the Earth that the Moon is located near (and the opposite side) is receiving high tides due to the gravitational force from the Moon, the sides of the Earth is receiving low tides as the bodies of water moves towards the side where the Moon is located (and the opposite side).
Some people may wonder why the Moon’s gravitational pull is more influential to the tides than the Sun, as the Sun would have a greater gravitational force on the Earth due to how massive it is compared to the Moon and Earth. Well, this is due to the distance of the celestial bodies; since the Moon is much closer to the Earth than the Sun, the gravitational force of the Moon is not negligible. However, despite being closer, Newton’s Law of Universal Gravitation (and the formula) shows that the Sun’s gravitational force on the Earth is about 200 times greater than the Moon’s gravitational force on the Earth (calculated on homework 4; don’t think I can send that), but still the Moon’s pull on the Earth is more influential on the tides; this is because the difference in gravitational forces between the near and far side of Earth by the Moon is twice as greater than that of the Sun, and relatively the difference in the gravitational forces between the near and far side of Earth for the Sun is 0.0173% while for the Moon is 6.28% (calculations are at the bottom).
So the Moon has a greater influence on the tides than the Sun due to being closer to the Earth, causing a greater difference in gravity in the far side and near side of the Earth.
Top equation is the Sun’s percentage difference in gravitational force between the near and far side of Earth to the gravitational force the Sun exerts on Earth; bottom equation is the Moon’s. Calculated on Desmos.
Usually about every 12 hours coastal places around the world experience high and low tides in a constant cycle. This is due to the subtle pull of the Moon’s gravitational forces on the Earth’s water supply. Along the Earth/Moon line (The path at which the Moon orbits the Earth), water swells towards it. This pull is what causes waters to recede from shore as well as return after the moon leaves the vicinity.
But not only that, the Moon is constantly pulling at water along the opposite end of Earth as well. This is because the Moon’s gravity affects every point on Earth even when it’s not close to it and it just so happens that it along that same imaginary orbital line, the water is still affected by being so close to the moon.
Another fun fact is that about twice a month, the combined pull of both the Sun and Moon when lined up in a single direction facing Earth causes remarkably higher tides (but these only occur about every 2 weeks). Also, the maximum point of swell seen by the tides actually occurs before the point at which the moon is closest to the Earth. This is due to the fact that both the Sun and Moon rotate in the same direction and so it takes extra time for any point on our planet to be directly below the Moon. This phenomenon causes the tides to be around 50 minutes ahead of the actual path of the Moon.
Next time you’re by the sea, take some time to appreciate just how much we really are affected by our orbiting friend.
For this post I wanted to discuss the effect that satellites have on astronomical observations. There are many problems that limit our ability to make observations, such as light pollution, the diffraction limit, and technological limitations. Despite this, astronomers have steadily been improving their equipment and building new complex telescopes to overcome these limitations. However, one issue that is only going to get worse is the issue of artificial satellites. Companies such as SpaceX are sending tens of thousands of satellites into orbit, with the number only growing every year. Organizations such as the International Astronomical Union have expressed great concern, but these satellites remain largely unregulated. These satellites reflect sunlight, causing many issues for ground-based telescopes and observations. Recent models of Starlink satellites have included special equipment to prevent sunlight from reflecting off of them, however, many concerns remain such as the impact these satellites may have on the climate when deorbited.
While the role of light in our everyday lives is to make color and form visible, by studying light with spectroscopy, we can learn a surprising amount about the object that produces a certain spectrum of wavelengths.
In order to understand spectroscopy, first, we must understand what light physically is. Light is composed of photons, which behave like both particles and waves. Like particles, photons are discrete pieces that can be individually counted. Like waves, photons have specific wavelengths and frequencies that carry a determinable amount of energy. Secondly, we must know how energy is stored in electrons. Electrons store electrical potential energy, but only at specific values called energy levels. These energy levels are quantized, and it is not possible for electrons to have energy in between the particular energy levels for their atom (or molecule). In order for an electron to change energy levels—called an energy level transition—the electron must gain or release exactly how much energy differentiates the two levels. Furthermore, these energy levels are distinct for each atom, which gives each structure a chemical “fingerprint.”
Now that we have some foundational knowledge, we can begin to decode spectra. There are three basic types: (1) a continuous spectrum, a broad rainbow of colors, (2) an emission line spectrum, which features bright emission lines at specific wavelengths against a black background, and (3) an absorption line spectrum, which features dark absorption lines against a rainbow background. A continuous spectrum is produced by hot dense light sources that emit a wide range of wavelengths. Understanding where the lines originate from on the other two spectra is more involved.
Let’s first discuss emission line spectra. Imagine that the object we’re examining is a distant cloud of gas. The atoms of this cloud are constantly colliding with and transferring energy to each other. Some of these collisions happen to transfer the right amount of energy necessary for an energy level transition, bumping electrons to higher energy states. However, these electrons cannot maintain the higher levels and thus quickly release the extra energy in the form of photons. Due to the conservation of energy, these photos contain the same amount of energy that it took for the electrons to make the transition. These photons appear on the spectrum as bright bands at their corresponding wavelengths. Because the energy transition levels are unique for different atoms, by recognizing the patterns photons create on the spectrum, we can determine the chemical composition of the gas cloud.
Now imagine that a light bulb is placed behind the cloud. Most of the photons from the light source will pass through the cloud (creating a continuous spectrum), but the photons that have the exact energy needed to cause an energy level transition will be absorbed by the atoms. Since these photons don’t make it past the cloud to our spectrum, the specific wavelengths corresponding to those photons will be omitted, producing black bands across the rainbow background. This creates an absorption line spectrum, which is essentially an inverted emission line spectrum. The patterns of bands are the same for different atoms on both spectra because equivalent amounts of energy are absorbed or released to transition an electron to a higher or lower energy level.
In addition to chemical makeup, spectroscopy can also provide information about the temperature, speed, and rotation rate of distant objects—all with light!
Source: the Cosmic Perspective by Bennet, Donahue, Schneider & Voit
In the world of telescopes, there are two main types: refracting and reflecting. The first telescopes created by astronomers in the 1600s were refracting telescopes. These work much like eye glasses. A curved lens bends the light into the observer’s eye. The bigger the lens the further into space a person could see. These worked well in the olden days, and are great for backyard use, but big lenses are heavy, thick, and must be perfectly clean and smooth on both sides to work well. Introduce the reflecting telescopes. These are made using mirrors, usually in a paraboloid shape. These telescopes use these paraboloid mirrors to concentrate the light through the optics. These work better because a mirror only needs one side to be perfect in order to work, and they are much lighter than lenses. Some examples of these types are the Hubble Space Telescope and the James Webb Space Telescope.
Retrograde motion is when the motion of a planet seems to reverse direction in the sky. The name of this phenomenon is derived from the Latin word retrogradus, which means “going backward.” This motion, however, is purely an illusion as the planet’s motion does not actually change and start moving backward in its orbit. The reason for the apparent change in motion is because of the differences in the orbital speeds of the planets. For example, the planet Mars moves slower in its orbit than Earth, therefore when we pass Mars our Orbit, Mars seems to be moving backward since we are faster than it.
Here is an animation of the retrograde motion of mars:
Retrograde motion is when a planet appears to move backward in its orbit relative to the rest of the night sky. Planets such as Mars and Jupiter can be seen in retrograde motion. Retrograde motion occurs due to the movements and relative positions of other planets around the sun. Earths’s orbit occasionally catches up with other planets’ orbit, causing an effect in which the planet seems to move backwards . Throughout history retrograde motion has been used to prove a heliocentric model of the solar system
For a deeper exploration of retrograde motion, you can check out this detailed article on NASA’s website.
Exploring how gravity on different planets in our solar system is different.
Gravity definition: Gravity is the force that attracts items to a planet or other body’s core. Gravity keeps the planets in orbit around the sun.
Since all the planets weigh differently, and have different radius this causes the gravitational pull of each planet to be different.
For example, if you weigh 100 pounds on Earth, you may see how differing gravity can affect you while you are on different planets, from below.
Image credit:NASA ( 2nd imagine from ” what is gravity?”
Why?: Weight is defined as mass being drawn by gravity towards the center of the nearest object applying gravitational pull. Weight varies depending on location. On Earth, the difference is insignificant. However, in space, things are constantly pulled into another object’s gravity well (such as the Earth, Sun, Moon or any other planets in our solar system) and experience free fall. In this scenario, the things are weightless. Other planets’ gravity forces vary, so objects have different weights.
Gravity on moon Orbit: Gravity keeps the planets in orbit around the sun and the moon in orbit around the Earth. The moon’s gravitational pull attracts the waters, resulting in ocean tides. Gravity forms stars and planets by attracting the material from which they are made.
The stronger the planet’s gravity, the faster the moon travels in order to remain in orbit. For example, as compared to Jupiter, the Earth’s moon travels much slower. Furthermore, a planet’s gravity can influence how far the moon can go. Moons can sustain a stable orbit at varied distances based on the planet’s mass and gravitational field.
You throw something up in the air and it falls down. Why? Gravity, obviously, everyone knows that. But what really is gravity?
By most common knowledge, gravity is one of the four fundamental forces, and has a lot more to it than just making things fall. Gravity actually works as an attraction between two masses, and is stronger the larger the mass of one thing is. That’s why everything falls down on Earth, its so large that it attracts everything to it’s center, so things “fall”. They don’t go down necessarily, they go towards the center. Even people like you and me have gravity, ours is just so small you can’t notice it.
Different sized masses will have different gravitational pulls. Earth’s for instance has a gravitational acceleration of 9.8 m/s^2, which basically means everything on/near Earth is constantly accelerating towards it’s center at that rate. Jupiter, the largest planet, has an acceleration of 24.8 m/s^2 while Mercury, the smallest, has an acceleration of just 3.7 m/s^2.
That sounds a lot better right? Gravity is a force that attracts masses towards other masses, based on how large they are. This is what Isaac Newton, one of the most important figures in physics, was able to come up with and for the most part, was correct.
Enter Albert Einstein. Einstein developed the theory of general relativity, which stated that gravity is a property of four-dimensional space-time. Space-time curves around mass, and the larger the mass, the larger the curve. This curve causes objects to be affected by gravity, or to our perspective, fall. We cannot see the curve because it is in the fourth dimension so we see it as a straight line.
Newton’s gravity is still going to be accurate for virtually everything in day to day life, but if you are dealing with things traveling or near light speed, Einstein’s theories are going to be key.
