Expanding Our Minds: The Science Behind the Expansion of the Universe

You’ve probably heard of the name Hubble before. “Hey, isn’t that that big telescope that’s out in space taking pictures of the universe?” And, you would be right if you did ask such a question. But, like many things that are named and sent to space, these names have a meaning. The history of the name Hubble in our modern world begun with one man, just like you and me, called Edwin Hubble.

Hubble
Edwin Hubble, the pipe smoking legend himself. Sourced from Spacetelescope.org

Hubble was a noble man. As a WWI veteran who was born in Missouri, he simply went on to pursue his passions. His fate with physics, however, was not coincidence, as he earned a full scholarship to the University of Chicago and worked on Robert Milikan, who would later go on to win the Nobel Prize for his quantization of the electron via his oil-drop experiment. Surprisingly, Hubble ended up graduating from the University of Chicago with a degree in Jurisprudence. For the 99.9% of people who are unsure of what this degree is, it is simply a degree in the philosophy of law. Despite this, Hubble returned to the university to get a degree in astronomy and was later recruited to be part California’s Mount Wilson Observatory.

Mount wilson
California’s picturesque Mount Wilson Observatory. Sourced from the LA Times.

 

It was in this observatory that, while studying galaxies Hubble noticed something interesting. Hubble discovered that galaxies were moving away from each other. But, this movement was not random at all, but instead at a linear rate. Let me explain this by using arbitrary terms. Let’s say that there is a galaxy called “A” that is x kilometers away from us. Now, let’s say there is a galaxy “B” that is 2x kilometers away from us. x can be any value, but it’s value does not matter. What does matter is the fact that B is 2 times further away from us than A is. Therefore, since B is two times further away than A is it will appear to be moving away from us twice as fast as galaxy A is moving away from us. Edwin Hubble and his colleagues published this data, resulting in a revolutionary look at space and the universe itself.

hubbletrouble
From his observations, we coin the term of Hubble’s law and the Hubble constant. Hubble’s law shows how recessional velocity (the speed at which something is moving away) increases linearly the further away it is. The Hubble constant is simply the slope of this line. sourced from GCSE Astronomy (for all you Brits out there).

From this data we get the Hubble Law. Hubble’s Law simply states that the further away something is in space the faster it will appear to be moving away from us. From this we also derive the Hubble constant, which is this constant rate at which recessional velocity seems to increase as distance increases. Note, however, that this regards things not in our solar system that we are gravitationally locked to. This means that other things in our solar system, like the Sun and the planets, as well as other things in our galaxy, will not appear to be moving away from us because we are gravitationally locked with them. If this boggles you, think of it like this: every galaxy is in a car that is moving away from the other. If we welded those cars together, then they would still be moving, but moving together. Similarly, everything in our galaxy moves with the other, so this is not something you would see in the Milky Way.

The second thing to note is that these galaxies are not moving on their own accord, because according to the Hubble Constant at some point things really far away will appear to be moving away from us faster than the speed of light! However, this does not break physics, because the movement is caused by the expansion of space. Think of it like relaxing on top of a giant sheet of putty. If you pull it, you are not causing the motion, but rather the putty is. Similarly, the galaxies are not causing this motion but is a result of being carried away by the space under them. Since space is not matter, it does not violate any rules travelling faster than the speed of light or at any speed in general.

cosmic expansion
Space expansion illustrated. Sourced from Quora.

The second thing that is extremely important to point out is that the expansion of space does not create more matter, but rather just creates more space. This space is simply nothingness, so creating more nothing violates no conservation laws, including the conservation of energy or matter.

The most important thing to take away from this is that the universe is vast and continues to grow. As we try to learn more about space and space travel things are getting further away from us, and as the years go by feasible intergalactic travel becomes much more of an issue if we’re traveling by conventional distances. If humans truly want to explore the galaxy, we need to find a way to travel vast distances in short amounts of time. Maybe the answer lies in unlocking extra dimensions or other means, but the important thing to end with is that you, yourself, can ponder this and study this and one day profoundly change how we view things. Hubble was a simple man from a simple town and ended up profoundly changing the way we view space. Today there are so many astronomers that are tweaking Hubble’s predictions concerning the expansion of space. Even more, Hubble has inspired many with his work, including me. Whether or not astronomy is your inspiration, do not hold back. Take days to think and write and ponder, because only then will you be inspired to do something that you love and something the world will find amazing. Keep looking up.

starfield-why
Image sourced from Heavy.

Featured image sourced from The Astronomy Cafe.

1 Shift, 2 Shift, Redshift, Blueshift

Space is vast. In fact, vast enough to contains many million, billions, and trillions of galaxies and other celestial objects. So the ultimate question is, how do scientists keep track of all of the celestial bodies? How do we know that the Andromeda galaxy is coming toward us if we can’t tell if it is growing in size by using naked eye observation? These burning questions, my friend, can be answered thanks to the rise of technology and advancements in practices.

From physics, we know that:

Velocity = Distance / Time

Therefore, if we were astronomers in the past, all we would have to do is determine the distance that a a star or a celestial object travels, and records the times at which we determined these distances, and, by subtracting the difference between the final and initial distance and final and initial time to find the velocity. For those of you who have taken calculus, this may look like:

velocity

Now that we have established what velocity is (and learned a bit of calculus), how is it that astronomers collect data on an object’s position in space?

In astronomy, there is something that is famously known as the Cosmic Distance Ladder. That is, given how far away an object or body is estimated to be, a certain method or device will be used to try and accurately gauge its distance. The distance ladder is shown below

distance ladder
Sourced from The University of California, Berkeley

If we look at the figure then we can see that, for example, we can accurately tell how far away an object in our solar system is by using RADAR and LIDAR. By using this method, scientists shoot radio waves into space and check how long it takes for them to bounce back. They then take the time and multiply it by the speed of light (since radio waves travel at the speed of light) to determine an object’s distance. So, if we really wanted to determine an object’s velocity in the solar system relative to us, we could use this technology to determine the distance away an object is to us at several different times. We would then use this to determine whether an object is moving toward or away from us, as well as how fast it is moving. If an asteroid is in the solar system, this could really help in determining whether or not it will strike Earth!

asteriod
Yikes! Sourced from the Dailystar

However, what happens when we just want to know velocity? Well, we look at a celestial object’s absorption spectra. An absorption spectra is all of the visible light that an object absorbs in space, thus why it is called an absorption spectra. The absorption spectra for the Sun looks something like this:

sun
Sourced from bhs4

Those black lines tell us all of the wavelengths that our Sun absorbs. We can use these lines to then determine if an object is moving toward or away from us. If an object is moving toward us, the lines will all shift the same distance to the right. This is known as RedshiftIf an object is moving away from us, then these lines move to the left the same distance. This is known as a Blueshift. We can then determine if an object has it’s spectral lines moved left or right by finding its absorption spectra when its not moving. Since elements each have their own absorption spectra, if we know the elements a object is made out of, then we can determine the absorption spectrum for that element when it is not moving. A visual example of red and blue shift looks something like this:

redshift
Sourced from the California Institute of Technology

Finally, why does this shift in spectra even happen? Well, if you’ve ever heard an angry person honk their horn continuously while passing you on the freeway, you’ve probably experienced something known as a Doppler Effect. The Doppler Effect essential states that anything wave at a velocity greater than 0 relative to you will slightly bend. Thus, when that person passes you, the sound waves get bent and the sound gets distorted. There is a great video by altshift that explains this better visually. Therefore, since light is a wave, light that is moving toward or away from us will become distorted and essentially change in wavelength. Thus, that is why we see the shift in wavelength to the left or right with Redshift and Blueshift.

Note, however, that objects on Earth move too slow for us to see this distortion of light. However, we can still hear distorted sounds thanks to the Doppler Effect. And so, I leave you with this: Video on Doppler Effect Using Trumpets

Featured Image Sourced From news.softpedia

Just Because You’re Bulkier, Doesn’t Mean You Pull More

We’ve all seen and learned about the cosmos and the stars up above. We learned that the Earth revolves around the Sun because the Sun’s force on the Earth is greater than any of the other major celestial bodies near this. However, something that many people forget is that this process is facilitated by Newton’s Universal Law of Gravitation.

In terms of the realm of physics, Newton describes the Universal Law of Gravitation as:

F12 = G$\displaystyle{m_1 m_2 \over r^2}$

Now, I understand that the physics formulas can be a bit daunting, so let is break this down. First, let us define the variables in this formula:

F12 = Force exerted by one body on another

G = The Gravitational Constant (for those technically inclined, this number is 6.67408 × 10-11 m3 kg-1 s-2)

m1= Mass of one of the bodies

m2= Mass of the other body

r2= distances between the center of each body, squared

Okay, so now that we know what the equation means you’re probably asking

Okay, so now I know how the force between two bodies is measured. What does that have to do with anything?

Well, this is important because this clears up a common misconception in people’s minds about gravity and attraction, especially in space. Let us say that, for example, mis the mass of the Earth, mis the mass of the Sun, and r is the distance between the sun and the Earth. Then, our Law of Gravitation Equation would look something like this:

Gravitation1

This formula is then saying that, if we had all of these values, then we would know the gravitational force that the Earth exerts on the Sun. Now, let’s switch it around. Let’s say mis the mass of the Sun, mis the mass of the Earth, and r is STILL the distance between the sun and the Earth (in other words, r has NOT changed). Then, the force that the Sun exerts on the Earth would be characterized by:

Gravitation2

Now, if we employ our first grade multiplication rules (the Commutative Property of Multiplication), we notice that both forces are equal! Yes, this means that the force that the Sun exerts on the Earth is EQUAL to the force the Earth exerts on the Sun. This is important because it proves false the common misconception that more massive things pull stronger on an object than less massive things. We see that, by using the Universal Law of Gravitation, this is false. Therefore, we can conclude that all objects that attract each other exert an equal force on one another.

Now, this also generalizes to smaller objects as well. Yes, humans have a gravitational attraction to their phones just as their phones are gravitationally attracted to them. However, the force of this attraction is so weak that we simply do not notice it. This Veritasium video does well in explaining the mathematics behind this. However, now that you know this this means that the pasta you attracted toward your face for dinner had an equal gravitational attraction to you. And, for those of you looking for a Valentine, you can now be certain that your crush is equally attracted to you as you are to him or her (at least concerning gravitational attraction).

love
Sourced from theodysseyonline

Featured Image Sourced From ytimg

Progression of the Seasons? Thank Precession

Everyone knows that the Earth experiences seasons. In the Northern Hemisphere children rejoice as they enjoy the summer sun in the month of June, while in the Southern Hemisphere they embrace the cold, daydreaming of warm summer days that await them in six months. However, what if I were to tell you that in about 13,000 years Gemini’s will be born in the winter (in the Northern Hemisphere) and Aquarius’s will be born in the summer (in the Northern Hemisphere)?

Indeed, this is a phenomenon known as “Precession”.

 

precession
Sourced from gramhancock.com

Precession is a phenomenon in which Earth’s axis rotates in a circular pattern. This effect is actually caused by Earth’s rotation. See, if you go back to classical physics (which I know are skeletons in the closet), we know that something accelerates in a circular motion there is an equal and opposite reaction that occurs, or a centrifugal force. This centrifugal force fights the force of gravity, which is the force that keeps the Earth from splitting apart on itself while it rotates. If you’ve ever been in a car and made a turn, or you’ve been on a merry-go-round you’ve probably experienced a force that is trying to push you out of the car or off of the merry-go-round. This is centrifugal force.

 

circular_motion_car
The centrifugal force pushes against the force of gravity and causes the Earth to bulge, causing the shape of the Earth to be more bulged at the equator than at its poles. Sourced from ScienceLibrary

It is this centrifugal force that causes the Earth to bulge at the equator than at its poles. This bulging makes it so that Earth is not a perfect sphere. Now, since Earth is not a perfect sphere the sun will pull more on the bulge of the Earth that is closer to it than the other end of the bulge. This imbalance of force causes the Earth to rotate, with its axis as its center point. This rotation, as noted in the figure above, takes about 25,700 years to make a full 360 degree rotation. Now, what does this mean in terms of seasons?

Well, if we look at the first picture we can see that after approximately 13,000 years the Earth’s axis will be tilted the other way, or -23.5 degrees. This means that if we view things using our calendar then it will be winter in the northern hemisphere in the month of June and summer during Christmas! However, according to Cornell University Professor Jagadheep Pandian, humans will adjust the calendar so that it is always summer in June and always winter in Decemeber (sourced from Cornell University). I guess we will always have a white Christmas!

If you would like to see a video description of what I just described, I highly recommend watching this video by It’s Just Astronomical.

Always remember, look up, be curious, and be awed.

(Featured image sourced from epiphanies.com.au)

 

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