Universe + Astronomy Flashcards
What is the Universe?
The universe is everything that exists, including all matter and energy everywhere.
What is astronomy?
The study of what is beyond Earth is called astronomy.
What is the Geocentric Model and when did it take place?
Aristotle, It took place in the 4th century BC. It is an “Earth-centered” model. Aristotle Noticed that the sun and moon both rise and set
and Everything, including the Sun, orbit Earth in circular orbits
What is the Heliocentric Model and when did it take place?
Copernicus, It took place in the 1500s. “Sun-centered” model. Said the Sun in the center and all planets orbit around it. He still thought the universe was STATIC (unchanging) but now thinks it might be INFINITE as there are other stars (suns)
What did the Heliocentric model do differently that made it more accurate?
He found that the model would be more accurate if planets orbits were elliptical, not circular.
What was the popular thought?
Popular thought the universe was FINITE (has an end) and STATIC (unchanging)
How did Hubble discover there are galaxies beyond the Milky Way?
The discovery of galaxies beyond the Milky Way: Before Hubble, many astronomers thought the Milky Way was the entire universe. Hubble’s observations of the Andromeda galaxy and others proved that these were separate galaxies, far beyond our own.
Henrietta Leavitt discovered that the time it takes for certain stars to “blink” tells us how far away they are. Hubble used this method to measure the distance to galaxies, showing that some were so far away, they were outside the Milky Way. This proved that the universe is much bigger than we thought.
What were Hubble’s contributions to astronomy? (1889 - 1953)
HUBBLE’S CONTRIBUTIONS:
There are galaxies beyond our own (the universe is not finite)
Galaxies are moving away from each other. (the universe is not static)
How did Hubble discover galaxies are moving away from each other?
Hubble discovered that galaxies are moving away from each other by studying their light. He noticed that the light from most galaxies was “shifted” toward the red end of the spectrum. This is called redshift. The more distant a galaxy was, the more its light shifted. This shift happens because the universe is expanding, and as galaxies move farther away, their light stretches out, making it look redder. This showed that galaxies are moving away from each other, and the universe is growing.
What is the Big Bang theory?
If galaxies are moving apart, it means they were once very close together. This point in time is called “time zero.” At time zero, all the matter in the universe was packed into one tiny, extremely hot, and dense mass. The event where this mass started to expand is known as the Big Bang.
What is evidence 1 of The Big Bang Theory and what was it?
Sound travels in waves. The higher the frequency, the higher the pitch we hear.
Light also travels in waves, and the frequency of these waves affects the color we see. Purple and blue have the highest frequencies, while red has the lowest.
When we look at light from distant galaxies, it appears more red than it should. This is called a red shift and shows that these galaxies are moving away from us. us. The further away they are, the faster they are moving away. As something gets farther away, the light’s wavelength gets longer, making it look red.
What is the Doppler effect?
When the object producing sound moves, the pitch changes. The pitch is higher if the object gets closer, and lower if it moves away.
What was evidence 2 of The Big Bang Theory and what was it?
Light travels at a constant speed of about 5.8 trillion miles per year (1 light year). The farther we look into space, the further back in time we see, because light takes time to reach us. For example, if we look at something 100 light years away, we see it as it was 100 years ago.
We can detect light that started about 380,000 years after the Big Bang. This light is called the Cosmic Microwave Background (CMB). It’s made of microwaves, and its frequency is lower because space has stretched, stretching the radiation.
Microwave radiation comes from all directions in space with the same strength. This shows it’s leftover from the Big Bang and that the Universe has cooled to about -270°C, just as the Big Bang Theory predicted.
What is evidence 3 of The Big Bang Theory and what was it?
When the universe cooled, atoms formed, mostly hydrogen (1 proton, 1 electron) and helium (2 protons, 2 electrons, 2 neutrons).
There were more protons than neutrons, about 7 protons for every neutron, because neutrons turned into protons. Most neutrons ended up in helium atoms.
This created a ratio of 4 hydrogen atoms for every 1 helium atom. Since helium is 4 times heavier than hydrogen, this explains why we see about 75% hydrogen and 25% helium in the universe today.
The universe was much hotter in the past, and as it cooled, hydrogen and helium became the most common elements.
