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What's in our universe
Transcript of What's in our universe
Astrophysics is the application of physics to the study of the universe.
Bone sticks from locations like Africa and Europe from possibly as long ago as 35,000 BCE are marked in ways that tracked the moon's phases.
Stonehenge was constructed from 3000 BC to 2000 BC
Many aspects of Stonehenge, such as how it was built and which purposes it was used for, remain subject to debate.
The great trilithon are aligned to the sunset of the winter solstice and the opposing sunrise of the summer solstice.
The precise orientation of the Egyptian pyramids affords a lasting demonstration of the high degree of technical skill in watching the heavens attained in the 3rd millennium BC.
It has been shown the Pyramids were aligned towards the pole star (Polaris), which is the closest visible star to the Earth's north celestial pole.
In the renaissance Nicolaus
proposed a heliocentric system, in which the planets revolved around the Sun and not the Earth.
was an astronomer and mathematician. He believed that the Earth was the center of the Universe. The word for earth in Greek is geo, so we call this idea a "geocentric" theory.
Even starting with this incorrect theory, he was able to combine what he saw of the stars' movements with mathematics, especially geometry, to predict the movements of the planets.
- He, too, believed in a geocentric Universe and that the planets and stars were perfect spheres though Earth itself was not.
- created a telescope that could enlarge objects up to 20 times. He was able to use this telescope to prove the truth of the Copernican system of heliocentrism.
He published his observations which went against the established teaching of the Church. He was brought to trial and, although he made a confession of wrong-doing, he was still kept under house arrest for the rest of his life.
Phases of the moon
The moon produces no light of its own.
If any part of the moon’s surface is not in sunlight, we cannot see that part because space (the background) is black too.
The moon is then said to wane as it passes through the gibbous moon, third-quarter moon, crescent moon and back to new moon.
Only one side of the Moon is visible from Earth because the Moon rotates about its spin axis at the same rate that the Moon orbits the Earth, a situation known as
or tidal locking.
This means that one full ‘day’ of the moon (meaning the length of time it takes for the moon to rotate around itself once) is about 4 weeks long.
How did the moon become tidally locked?
Why do we look to space?
His ideas, including the revelation that the Earth rotates on its axis, were too different for most of the scholars of his time to accept.
A little history...
Because the moon revolves around the Earth, we see different amounts of its surface lit up during its 291⁄2-day cycle.
As the moon waxes (the amount of illuminated surface as seen from Earth is increasing), the lunar phases progress through new moon, crescent moon, first-quarter moon, gibbous moon, and full moon.
The barren surface of the moon has three main features. First, there are millions of craters ranging in size from a few metres to over 200 km across.
They are named after famous astronomers. For example, Tycho, the large crater at the top of the moon, is named after Tycho Brahe, a famous Danish astronomer.
Astronomers infer that most of the craters were formed when meteors collided with the moon.
Surprisingly, the near side has fewer craters than the far side... Why?
The large dark rounded areas are called maria (MA-ree-a) or seas.
Astronomers, based on basalt brought back from the moon, infer that the areas we call seas were once huge craters which filled with lava.
There are also long narrow valleys called
. One of these is more than 500 km long.
Astronomers are not sure how rills were formed. One theory is that they are lava tunnels, like those on Earth, whose roofs have collapsed.
What causes tides?
As the Earth rotates, the tidal bulges stay roughly in the same place relative to the moon, because the Earth rotates much faster than the moon revolves.
Both the sun and the moon exert a gravitational pulling force on the Earth.
As the Earth rotates, each place on Earth usually passes through two high tides and two low tides each day.