The Physics Behind “Interstellar’s” Visual Effects Was So Good, it Led to a Scientific Discovery

While he was working on the film Interstellar, executive producer Kip Thorne was tasked with creating the black hole that would be central to the plot. As a theoretical physicist, he also wanted to create something that was truly realistic and as close to the real thing as movie-goers would ever see.

On the other hand, Christopher Nolan – the film’s director – wanted to create something that would be a visually-mesmerizing experience. As you can see from the image above, they certainly succeeded as far as the aesthetics were concerned. But even more impressive was how the creation of this fictitious black hole led to an actual scientific discovery.

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How NASA and SpaceX are Working Together to Land on Mars

It is no secret that NASA is seeking out private space contractors to help bring some of its current plans to fruition. Naturally, these involve restoring indigenous launch capabilities to the US, but also include the more far-reaching goal of sending astronauts to Mars. Towards that end, NASA and SpaceX participated in an unprecedented data-sharing project that will benefit them both.

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Water On The Moon Was Blown in by Solar Wind

When they first set foot on the Moon, the Apollo 11 astronauts painted a picture of the landscape as a bone-dry desert. So astronomers were naturally surprised when in 2009, three probes showed that a lot of water is locked up in minerals in the soil. There has been some debate as to where the water came from, but now two researchers with the National Museum of Natural History in Paris, France, have determined that most of the water in the soil on the surface of the Moon was formed due to protons in the solar wind colliding with oxygen in lunar dust, rather than from comet or meteorite impacts.

The first hints that there was water on the Moon came when India’s Chandrayaan-1 found hints of water across the lunar surface when it measured a dip in reflected sunlight at a wavelength absorbed only by water and hydroxyl, a molecule that contains one atom of hydrogen and one atom of oxygen.

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NASA Investigating Deep-Space Hibernation Technology

Manned missions to deep space present numerous challenges. In addition to the sheer amount of food, water and air necessary to keep a crew alive for months (or years) at a time, there’s also the question of keeping them busy for the entirety of a long-duration flight. Exercise is certainly an option, but the necessary equipment will take up space and be a drain on power.

In addition, they’ll need room to move around, places to sleep, eat, work, and relax during their down time. Otherwise, they will be at risk of succumbing to feelings of claustrophobia, anxiety, insomnia, and depression – among other things.

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Bigelow Inflatable Module to be Added to Space Station in 2015

Astronauts aboard the International Space Station are going to be getting an addition in the near future, and in the form of an inflatable room no less. The Bigelow Expandable Activity Module (BEAM) is the first privately-built space habitat that will added to the ISS, and it will be transported into orbit aboard a Space X Falcon 9 rocket sometime next year.

“The BEAM is one small step for Bigelow Aerospace,” Bigelow representative Michael Gold told Universe Today, “but is also one giant leap for private sector space activities since the BEAM will be the first privately owned and developed module ever to be part of a crewed system in space.”

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What is the Milky Way?

Artist's conception of the Milky Way galaxy. Credit: Nick Risinger

When you look up at the night sky, assuming conditions are just right, you might just catch a glimpse of a faint, white band reaching across the heavens. This band, upon closer observation, looks speckled and dusty, filled with a million tiny points of light and halos of glowing matter. What you are seeing is the Milky Way, something that astronomers and stargazers alike have been staring up at since the beginning of time.

But just what is the Milky Way? Well, simply put, it is the name of the barred spiral galaxy in which our solar system is located. The Earth orbits the Sun in the Solar System, and the Solar System is embedded within this vast galaxy of stars. It is just one of hundreds of billions of galaxies in the Universe, and ours is called the Milky Way because the disk of the galaxy appears to be spanning the night sky like a hazy band of glowing white light. Continue reading “What is the Milky Way?”

What is the Difference Between Speed and Velocity?

What is the Difference Between Speed and Velocity?

When it comes to measuring motion, that is the relative passage of an object through space at a certain rate of time, several different things need to be taken into account. For example, it is not enough to know the rate of change (i.e. the speed) of the object. Scientists must also be able to assign a vector quantity; or in other words, to know the direction as well as the rate of change of that object. In the end, this is major difference between Speed and Velocity. Though both are calculated using the same units (km/h, m/s, mph, etc.), the two are different in that one is described using numerical values alone (i.e. a scalar quantity) whereas the other describes both magnitude and direction (a vector quantity).

By definition, the speed of an object is the magnitude of its velocity, or the rate of change of its position. The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval. Represented mathematically, it looks like this: ν=[v]=[?] = [dr/dt]•, where speed ν is defined as the magnitude of the velocity v, that is the derivative of the position r with respect to time. The fastest possible speed at which energy or information can travel, according to special relativity, is the speed of light in vacuum (a.k.a. c = 299,792,458 meters per second, which is approximately 1079 million kilometers per hour or 671,000,000 mph).

Velocity, on the other hand, is the measurement of the rate and direction of change in the position of an object. Since it is a vector physical quantity, both magnitude and direction are required to define it. The scalar absolute value (magnitude) of velocity is speed, a quantity that is measured in metres per second (m/s) when using the SI (metric) system. Mathematically, this is represented as: v = Δx/Δt, where v is the average velocity of an object, (Δx) is the displacement and (Δt) is the time interval. Add to this a vector (i.e. Δx/Δt→, ←, or what have you), and you’ve got velocity!

As an example, consider the case of a bullet being fired from a gun. If we divide the overall distance it travels within a set period of time (say, one minute), than we have successfully calculated its speed. On the other hand, if we want to determine its velocity, we must consider the direction of the bullet after it’s been fired. Whereas the average speed of the object would be rendered as simple meters per second, the velocity would be meters per second east, north, or at a specific angle.

We have written many articles about speed and velocity for Universe Today. Here’s an article about formula for velocity, and here’s an article about escape velocity.

If you’d like more info on speed and velocity, check out these articles:
Speed and Velocity
Angular and Linear Velocity

We’ve also recorded an episode of Astronomy Cast about the space shuttle. Listen here, Episode 127: The US Space Shuttle.


Dispersion of Light

Dispersion of Light

Look up into the rainy sky! What do you see? Well, if its just rained and the sun is once again shining, chances are you see a rainbow. Always a lovely sight isn’t it? But why is it that after a rainstorm, the air seems to catch the light in just the right way to produce this magnificent natural phenomenon? Much like stars, galaxies, and the flight of a bumblebee, some complicated physics underlie this beautiful act of nature. For starters, this effect, where light is broken into the visible spectrum of colors, is known as the Dispersion of Light. Another name for it is the prismatic effect, since the effect is the same as if one looked at light through a prism.

To put it simply, light is transmitted on several different frequencies or wavelengths. What we know as “color” is in reality the visible wavelengths of light, all of which travel at different speeds through different media. In other words, light moves at different speed through the vacuum of space than it does through air, water, glass or crystal. And when it comes into contact with a different medium, the different color wavelengths are refracted at different angles. Those frequencies which travel faster are refracted at a lower angle while those that travel slower are refracted at a sharper angle. In other words, they are dispersed based on their frequency and wavelength, as well as the materials Index of Refraction (i.e. how sharply it refracts light).

The overall effect of this – different frequencies of light being refracted at different angles as they pass through a medium – is that they appear as a spectrum of color to the naked eye. In the case of the rainbow, this occurs as a result of light passing through air that is saturated with water. Sunlight is often referred to as “white light” since it is a combination of all the visible colors. However, when the light strikes the water molecules, which have a stronger index of refraction than air, it disperses into the visible spectrum, thus creating the illusion of a colored arc in the sky.

Now consider a window pane and a prism. When light passes through glass that has parallel sides, the light will return in the same direction that it entered the material. But if the material is shaped like a prism, the angles for each color will be exaggerated, and the colors will be displayed as a spectrum of light. Red, since it has the longest wavelength (700 nanometers) appears at the top of the spectrum, being refracted the least. It is followed shortly thereafter by Orange, Yellow, Green, Blue, Indigo and Violet (or ROY G. GIV, as some like to say). These colors, it should be noted, do not appear as perfectly distinct, but blend at the edges. It is only through ongoing experimentation and measurement that scientists were able to determine the distinct colors and their particular frequencies/wavelengths.

We have written many articles about dispersion of light for Universe Today. Here’s an article about the refractor telescope, and here’s an article about visible light.

If you’d like more info on the dispersion of light, check out these articles:
dispersion of Light by Prisms
Q & A: Dispersion of Light

We’ve also recorded an episode of Astronomy Cast all about the Hubble Space Telescope. Listen here, Episode 88: The Hubble Space Telescope.


Diffraction of Light

Diffraction of Light

For some time, the behavior of light has baffled scientists. Initially, and in accordance with classic physics, light was thought to be a wave, an indefinable form of energy that simply flowed from a heated source. However, with the advent of quantum physics, scientists came to realize that photons, a tiny elementary particle responsible for all forms of electromagnetic radiation, was in fact the source. So you can imagine how confounded they were when, in the course of performing experiments, they discovered that it exhibited the behavior of both a particle and a wave! This rather unique behavior, the ability of light to behave as a wave, even though it is made up of tiny particles, is known as the Diffraction of Light.

By definition, diffraction refers to the apparent bending of waves around small obstacles and the spreading out of waves past small openings. It had long been understood that this is what happens when a wave encounters an obstacle, and by the 17th and 18th centuries, this behavior was observed through experiments involving light. One such physicist who observed this at work was Thomas Young (1773 – 1829), an English polymath who is credited devised the double-slit experiment. In this experiment, Young shone a monochromatic light source (i.e. light of a single color) through an aperture (in this case, a wall with a horizontal slits cut in it) and measured the results on a screen located on the other side. The results were interesting, to say the least. Instead of appearing in the same relative shape as the aperture, the light appeared to be diffracting, implying that it was made up of waves. The experiment was even more interesting when a second slit was cut into the screen (hence the name double-slit). Young, and those who repeated the experiment, found that interference waves resulted, meaning that two propagation waves occurred which then began to interfere with one another.

A more common example comes to us in the form of shadows. Ever notice how the outer edges do not appear solid, but slightly fuzzy instead? This occurs as a result of light bending slightly as it passes around the edge of an object, again, consistent with the behavior of a wave. Similar effects occur when light waves travel through a medium with a varying refractive index, resulting in a spectrum of color or a distorted image. Since all physical objects have wave-like properties at the atomic level, diffraction can be studied in accordance with the principles of quantum mechanics.

We have written many articles about diffraction of light for Universe Today. Here’s an article about visible light, and here’s an article about telescope resolution.

If you’d like more info on diffraction of light, check out these articles:
The Physics of Light: Diffraction
Experiments on Diffraction of Light

We’ve also recorded an episode of Astronomy Cast all about the Hubble Space Telescope. Listen here, Episode 88: The Hubble Space Telescope.


Angular Velocity of Earth

Angular Velocity of Earth

The planet Earth has three motions: it rotates about its axis, which gives us day and night; it revolves around the sun, giving us the seasons of the year, and through the Milky Way along with the rest of the Solar System. In each case, scientists have striven to calculate not only the time it takes, but the relative velocities involved. When it comes to the Earth rotating on its axis, a process which takes 23 hours, 56 minutes and 4.09 seconds, the process is known as a sidereal day, and the speed at which it moves is known as the Earth’s Angular Velocity. This applies equally to the Earth rotating around the axis of the Sun and the center of the Milky Way Galaxy.

In physics, the angular velocity is a vector quantity which specifies the angular speed of an object and the axis about which the object is rotating. The SI unit of angular velocity is radians per second, although it may be measured in other units such as degrees per second, revolutions per second, etc. and is usually represented by the symbol omega (ω, rarely Ω). A radian, by definition, is a unit which connects the radius of an arc, the length of the arc and the angle subtended by the arc. A full radian is 360 degrees, hence we know that the Earth performs two radians when performing a full rotation around an axis. However, it is sometimes also called the rotational velocity and its magnitude – the rotational speed – is typically measured in cycles or rotations per unit time (e.g. revolutions per minute). In addition, when an object rotating about an axis, every point on the object has the same angular velocity.

Mathematically, the average angular velocity of an object can be represented by the following equation: ωaverage= Δθ/Δt, where ω is the radians/revolutions per second (on average), Δ is the change in quantity, θ is the velocity, and t is time. When calculating the angular velocity of the Earth as it completes a full rotation on its own axis (a solar day), this equation is represented as: ωavg = 2πrad/1day (86400 seconds), which works out to a moderate angular velocity of 7.2921159 × 10-5 radians/second. In the case of a Solar Year, where ωavg = 2πrad/1year (3.2×107 seconds), we see that the angular velocity works out to 2.0×10-7 rad/s.

We have written many articles about the angular velocity of Earth for Universe Today. Here’s an article about angular velocity, and here’s an article about why the Earth rotates.

If you’d like more info on angular velocity of Earth, check out the following articles:
Angular Speed of Earth
Earth’s Rotation

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.