UNIVERSE W2

3. Calculate weight, compared to earth, on other astronomical bodies.

1.3e How strong?

View video: https://www.youtube.com/watch?time_continue=8&v=E43-CfukEgs [4.41 mins]

TASK 1.3a

Complete the slides between 12 and 29 from the PPT.

Blue slides/slides with blue writing are suggested extensions for students who have selected Physics for Years 11 and 12.

10 U 0 Digital INB EXT.pptx

TASK 1.3b

Use STTWS to develop DDL response to “You will weigh less on the moon than on Earth. T or F. Defend your position.”

1.4 How did the universe begin?

1.4 State the Big Bang Theory.

The Big Bang Theory

· to gain an overview of the theory of the origin of the universe, view video and deconstruct lyrics Big Bang Theory Theme [1.45]

Our whole universe was in a hot, dense state

Then nearly fourteen billion years ago expansion started, wait

The earth began to cool, the autotrophs began to drool

Neanderthals developed tools

We built a wall (we built the pyramids)

Math, science, history, unraveling the mysteries

That all started with the big bang! Hey!

Since the dawn of man is really not that long

As every galaxy was formed in less time than it takes to sing this song

A fraction of a second and the elements were made

The bipeds stood up straight, the dinosaurs all met their fate

They tried to leap but they were late

And they all died (they froze their asses off)

The oceans and Pangea, see ya wouldn't wanna be ya

Set in motion by the same big bang!

It all started with the big bang!

It's…

The Singularity

The Big Bang Theory is the leading explanation about how the universe began. At its simplest, it says the universe as we know it started with a small singularity, then inflated over the next 13.8 billion years to the cosmos that we know today. The Big Bang was not an explosion, as the name might suggest. Instead, it was the appearance of a very hot, very dense, single point (singularity) in space.

Because current instruments don't allow astronomers to peer back at the universe's birth, much of what we understand about the Big Bang Theory comes from mathematical formulas and models. Astronomers can, however, see the "echo" of the expansion through a phenomenon known as the cosmic microwave background (CMB).

When the universe was still very young — something like a hundredth of a billionth of a trillionth of a trillionth of a second — it underwent an incredible growth spurt. During this burst of expansion, which is known as inflation, the universe grew exponentially and doubled in size at least 90 times.

The first second, and the birth of light

In the first second after the universe began, the surrounding temperature was about 5.5 billion Celsius, according to NASA. The cosmos contained a vast array of fundamental particles such as neutrons, electrons and protons. These decayed or combined as the universe got cooler, and less dense as it spread out.

Inflation: the universe continued to grow, but at a slower rate. As space expanded, the universe cooled and matter formed.

This early soup would have been impossible to look at, because light could not carry inside it. "The free electrons would have caused light (photons) to scatter the way sunlight scatters from the water droplets in clouds," NASA stated.

3. The first 3 minutes to 380,000 years

Light chemical elements were created within the first three minutes of the universe's formation. As the universe expanded, temperatures cooled and protons and neutrons collided to make deuterium, which is an isotope of hydrogen. Much of this deuterium combined to make helium.

For the first 380,000 years after the Big Bang, however, the intense heat from the universe's creation made it essentially too hot for light to shine. Atoms crashed together with enough force to break up into a dense, opaque plasma of protons, neutrons and electrons that scattered light like fog.

4. Light

Over time, however, the free electrons met up with nuclei and created neutral atoms. This allowed light to shine through about 380,000 years after the singularity.

This phase is known as "recombination," and the absorption of free electrons caused the universe to become transparent. The light that was unleashed at this time, sometimes called the "afterglow", is detectable today in the form of radiation from the cosmic microwave background (CMB). It was first predicted by Ralph Alpher and other scientists in 1948, but was found only by accident almost 20 years later.

The era of recombination was followed by a period of darkness before stars and other bright objects were formed.

5. Stars and galaxies

Roughly 400 million years after the Big Bang, the universe began to come out of its dark ages. This period in the universe's evolution is called the age of re-ionization. This dynamic phase was thought to have lasted more than a half-billion years, but based on new observations, scientists think re-ionization may have occurred more rapidly than previously thought.

During this time, clumps of gas collapsed enough to form the very first stars and galaxies. The emitted ultraviolet light from these energetic events cleared out and destroyed most of the surrounding neutral hydrogen gas. The process of re-ionization, plus the clearing of foggy hydrogen gas, caused the universe to become transparent to ultraviolet light for the first time.

Source https://www.space.com/13320-big-bang-universe-10-steps-explainer.html

7. Our Solar System

Our solar system is estimated to have been born a little after 9 billion years after the Big Bang, making it about 4.6 billion years old. According to current estimates, the sun is one of more than 100 billion stars in our Milky Way galaxy alone, and orbits roughly 25,000 light-years from the galactic core.

Many scientists think the sun and the rest of our solar system was formed from a giant, rotating cloud of gas and dust known as the solar nebula. As gravity caused the nebula to collapse, it spun faster and flattened into a disk. During this phase, most of the material was pulled toward the center to form the sun.

8. Dark Matter

In the 1960s and 1970s, astronomers began thinking that there might be more mass in the universe than what is visible. Vera Rubin, an astronomer at the Carnegie Institution of Washington, observed the speeds of stars at various locations in galaxies.

Basic Newtonian physics implies that stars on the outskirts of a galaxy would orbit more slowly than stars at the center, but Rubin found no difference in the velocities of stars farther out. In fact, she found that all stars in a galaxy seem to circle the center at more or less the same speed.

The mysterious and invisible mass thought to be responsible for this became known as dark matter. Dark matter is inferred because of the gravitational pull it exerts on regular matter. (One hypothesis states the mysterious stuff could be formed by 'exotic' particles that don't interact with light or regular matter, which is why it has been so difficult to detect.)

Dark matter is thought to make up 23% of the universe. In comparison, only 4% of the universe is composed of regular matter, which encompasses stars, planets (and people).

9. Expanding Universe

In the 1920s, astronomer Edwin Hubble made a revolutionary discovery about the universe. Using a newly constructed telescope at the Mount Wilson Observatory in Los Angeles, Hubble observed that the universe is not static, but rather is expanding.

Decades later, in 1998, the prolific space telescope named after the famous astronomer, the Hubble Space Telescope, studied very distant supernovas and found that, a long time ago, the universe was expanding more slowly than it is today. This discovery was surprising because it was long thought that the gravity of matter in the universe would slow its expansion, or even cause it to contract. This is currently explained by "dark energy".

Dark energy is thought to be the strange force that is pulling the cosmos apart at ever-increasing speeds, but it remains undetected and shrouded in mystery. The existence of this elusive energy, which is thought to make up 73% of the universe, is one of the most hotly debated topics in cosmology.

Evidence in the CMB concerning gravitational waves, created as the universe expanded, was sought. Gravitational waves have been confirmed when talking about the movements and collisions of black holes that are a few tens of masses larger than our sun. These waves have been detected multiple times by the Laser Interferometer Gravitational-Wave Observatory (LIGO) since 2016. As LIGO becomes more sensitive, it is anticipated that discovering black hole-related gravitational waves will be a fairly frequent event.

10. What we still need to know

While much has been discovered about the creation and evolution of the universe, there are enduring questions that remain unanswered. Dark matter and dark energy remain two of the biggest mysteries, but cosmologists continue to probe the universe in hopes of better understanding how it all began.

Source https://www.sciencemag.org/news/2017/03/recharged-debate-over-speed-expansion-universe-could-lead-new-physics

TASK 1.4a How do we know what's in the universe?

https://www.pbs.org/deepspace/timeline/

* Click on each of the links below to view how our current understanding of the universe developed.

* Summarise the information into a table in your book with headings Time and Event.

1.5 Investigate the evidence that led to the prediction and discovery of the expansion of the universe by Hubble and Friedman.

In 1927, Hubble was moving beyond the Milky Way with what was then the world's biggest telescope, the 100-inch (2.5-m) Hooker telescope that loomed over Pasadena on top of Mount Wilson. He photographed the faint spiral smudges we know as galaxies and measured the reddening of their light as their motions Doppler-shifted it to longer wavelengths, like the keening of a receding ambulance. By comparing the galaxies' redshifts to their brightness, Hubble stumbled on something revolutionary: The dimmer and presumably farther away a galaxy was, the faster it was receding. That meant the universe was expanding. It also meant the universe had a finite age, beginning in a big bang.

To pin down the expansion rate—his eponymous constant—Hubble needed actual distances to the galaxies, not just relative ones based on their apparent brightness. So he began the laborious process of building up a distance ladder—from the Milky Way to neighboring galaxies to the far reaches of expanding space. Each rung in the ladder has to be calibrated by "standard candles": objects that shift, pulse, flash, or rotate in a way that reliably encodes how far away they are.

The first rung seemed reasonably sturdy: variable stars called cepheids, which ramp up and down in brightness over the course of days or weeks. The length of that cycle indicates the star's intrinsic brightness. By comparing the observed brightness of a cepheid to the brightness inferred from its oscillations, Hubble could gauge its distance. The Mount Wilson telescope was only good enough to see a few cepheids in the nearest galaxies. For more distant galaxies, he assumed that the brightest star in each had the same intrinsic brightness. Even farther out, he assumed that entire galaxies were standard candles, with uniform luminosities.

They weren't good assumptions. Hubble's first published constant was 500 kilometers per second per megaparsec—meaning that for every 3.25 million light-years he looked out into space, the expanding universe was ferrying away galaxies 500 kilometers per second faster. The number was way off—an order of magnitude too fast. It also implied a universe just 2 billion years old, a baby compared with current estimates. But it was a start.

By 1949, construction had finished on the 200-inch (5.1-m) telescope at Palomar in southern California—just in time for Hubble to suffer a heart attack. Hubble passed the mantle to Sandage, an ace observer who spent the subsequent decades exposing photographic plates during all-night sessions suspended in the telescope's vast apparatus, shivering and in desperate need of a bathroom break.

With Palomar's higher resolution and light-gathering power, Sandage could pluck cepheids from more distant galaxies. He also realized that Hubble's bright stars were in fact entire star clusters. They were intrinsically brighter and thus farther away than Hubble thought, which, in addition to other corrections, implied a much lower Hubble constant. By the 1980s, Sandage had settled on a value of about 50, which he zealously defended. Perhaps his most famous foil, French astronomer Gérard de Vaucouleurs, promoted a competing value of 100. One of the key parameters of cosmology was contested to an embarrassing factor of two.

It was the early 1990s, and the Carnegie Observatories in Pasadena, California, had emptied out for the Christmas holiday. Wendy Freedman was toiling alone in the library on an immense and thorny problem: the expansion rate of the universe.

Carnegie was hallowed ground for this sort of work. It was here, in 1929, that Edwin Hubble first clocked faraway galaxies flying away from the Milky Way, bobbing in the outward current of expanding space. The speed of that flow came to be called the Hubble constant.

Freedman's quiet work was soon interrupted when fellow Carnegie astronomer Allan Sandage stormed in. Sandage, Hubble's designated scientific heir, had spent decades refining the Hubble constant, and had consistently defended a slow rate of expansion. Freedman was the latest challenger to publish a faster rate, and Sandage had seen the heretical study.

"He was so angry," recalls Freedman, now at the University of Chicago in Illinois, "that you sort of become aware that you're the only two people in the building. I took a step back, and that was when I realized, oh boy, this was not the friendliest of fields."

In the late 1990s, Freedman, having survived Sandage's verbal abuse, was determined to solve the puzzle with a powerful new tool designed with just this job in mind: the Hubble Space Telescope. Its sharp view from above the atmosphere allowed Freedman's team to pick out individual cepheids (cepheid variable is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude) up to 10 times farther away than Sandage had with Palomar. Sometimes those galaxies happened to host both cepheids and an even brighter beacon—a Type Ia supernova. These exploding white dwarf stars are visible across space and flare to a consistent, maximum brightness. Once calibrated with the cepheids, the supernovae could be used on their own to probe the most distant reaches of space. In 2001, Freedman's team narrowed the Hubble constant to 72 plus or minus eight, a definitive effort that ended Sandage and De Vaucouleurs's feud. "I was done," she says. "I never thought I'd work on the Hubble constant again."

The acrimony has diminished, but not by much. Sandage died in 2010, and by then most astronomers had converged on a Hubble constant in a narrow range. But in a twist Sandage himself might savor, new techniques suggest that the Hubble constant is 8% lower than a leading number. For nearly a century, astronomers have calculated it by meticulously measuring distances in the nearby universe and moving ever farther out. But lately, astrophysicists have measured the constant from the outside in, based on maps of the cosmic microwave background (CMB), the dappled afterglow of the big bang that is a backdrop to the rest of the visible universe. By making assumptions about how the push and pull of energy and matter in the universe have changed the rate of cosmic expansion since the microwave background was formed, the astrophysicists can take their map and adjust the Hubble constant to the present-day, local universe. The numbers should match. But they don't.

It could be that one approach has it wrong. The two sides are searching for flaws in their own methods and each other's alike, and senior figures like Freedman are racing to publish their own measures. "We don't know which way this is going to land," Freedman says.

But if the disagreement holds, it will be a crack in the firmament of modern cosmology. It could mean that current theories are missing some ingredient that intervened between the present and the ancient past, throwing off the chain of inferences from the CMB to the current Hubble constant. If so, history will be repeating itself.

In the 1990s, Adam Riess, now an astrophysicist at Johns Hopkins University in Baltimore, Maryland, led one of the groups that discovered dark energy, a repulsive force that is accelerating the expansion of the universe. It is one of the factors that the CMB calculations must take into account.

Now, Riess's team is leading the quest to pin down the Hubble constant in nearby space and beyond. His goal is not just to refine the number, but to see whether it is changing over time in ways that even dark energy—as currently conceived—can't explain. So far, he has few hints about what the missing factor might be. "I'm really wondering what is going on," he says.

Debate over the Hubble constant, the expansion rate of the universe, has exploded again. Astronomers had mostly settled on a number using a classical technique—the "distance ladder," or astronomical observations from the local universe on out. But these values conflict with cosmological estimates made from maps of the early universe and adjusted to the present day. The dispute suggests a missing ingredient may be fueling the growth of the universe.

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