Prelim Physics Thread (2 Viewers)

[eyeseeyou]

Which ones lol?

For the time being help me with my short answer/extended response cosmic engine questions

 

[eyeseeyou]

For the time being help me with my short answer/extended response cosmic engine questions

The formula was T^2/r^3=4 pi^2/GM=keplers constant where:

G=gravitational constant
M=mass of sun

 

[InteGrand]

The formula was T^2/r^3=4 pi^2/GM=keplers constant where:

G=gravitational constant
M=mass of sun

If you know the formula, why do you need help with those Q's? Or do you know how to do them now?

 

[eyeseeyou]

If you know the formula, why do you need help with those Q's? Or do you know how to do them now?

Coz I'm stuck...

 

[1008]

Need help with cosmic engine questions:

1.What theory does the red-shift support?
2. Calculate the velocity of recession of a distant galaxy at 12.5 Mpc from us
3. Assess one of the models of the universe developed from the time of Aristotle to the time Newton to identify the limitations placed on the development of the model by the technology available at the time
4. Outline briefly how the accretion of galaxies occurred.

1) Assuming you're familiar with the Doppler effect, objects that are moving away from you tend to have a longer wavelength than objects that are stationary. This means that the red shift in galaxies (means that the light they release is red-shifted which has a longer wavelength than most other colours) is evidence of the Big Bang Theory (as it is proof galaxies and other celestial objects are moving away from us)
2) ? Sorry don't remember the formula for this from the top of my head (should be Hubble Law), will try to get back to you
3) You could just say that Aristotle and Ptolemy's model of the universe placed Earth in the centre of the universe, and this was because of the lack of telescopes and satellites. This caused Aristotle and Ptolemy to base their model of the universe based on observations made and data collected with the naked eye on Earth, which showed the Sun, Moon etc were travelling around a stationary Earth, which they interpreted as Earth being centre of their then "observable" universe.
4)

In short:
Accretion is the process of growth of a body by gravitational attraction of more matter.

After a few hundred thousand years after the Big Bang, the Universe was cooled down and atoms were formed. As the Unvierse was further expanding and cooling, the atom particles lost kinetic energy and gravity began to attract them together forming regions of high mass density. The regions of high mass density began to attract nearby material and gain mass. This process is known as accretion.

At some time or another, all matter in the universe formed discrete gas clouds known as protogalaxies. As further accretion occured, galaxies were formed. Accretion also occured inside galaxies, forming stars.

That should get you started, but if you need a more detailed explanation, I'll type one up later on tonight.

 

[InteGrand]

Coz I'm stuck...

It's just substituting numbers into a formula. Which part did you get stuck on?

 

[eyeseeyou]

1) Assuming you're familiar with the Doppler effect, objects that are moving away from you tend to have a longer wavelength than objects that are stationary. This means that the red shift in galaxies (means that the light they release is red-shifted which has a longer wavelength than most other colours) is evidence of the Big Bang Theory (as it is proof galaxies and other celestial objects are moving away from us)
2) ? Sorry don't remember the formula for this from the top of my head (should be Hubble Law), will try to get back to you
3) You could just say that Aristotle and Ptolemy's model of the universe placed Earth in the centre of the universe, and this was because of the lack of telescopes and satellites. This caused Aristotle and Ptolemy to base their model of the universe based on observations made and data collected with the naked eye on Earth, which showed the Sun, Moon etc were travelling around a stationary Earth, which they interpreted as Earth being centre of their then "observable" universe.
4)

V=HoD

Where V is the velocity at which galaxy is movign away (km/s)
Ho is hubble's constant ((67.8 km/s)/Mpc)
D is distance to galaxy (mega parasecs)

 

[eyeseeyou]

It's just substituting numbers into a formula. Which part did you get stuck on?

Um...I didn't know where to start

 

[eyeseeyou]

1) Assuming you're familiar with the Doppler effect, objects that are moving away from you tend to have a longer wavelength than objects that are stationary. This means that the red shift in galaxies (means that the light they release is red-shifted which has a longer wavelength than most other colours) is evidence of the Big Bang Theory (as it is proof galaxies and other celestial objects are moving away from us)
2) ? Sorry don't remember the formula for this from the top of my head (should be Hubble Law), will try to get back to you
3) You could just say that Aristotle and Ptolemy's model of the universe placed Earth in the centre of the universe, and this was because of the lack of telescopes and satellites. This caused Aristotle and Ptolemy to base their model of the universe based on observations made and data collected with the naked eye on Earth, which showed the Sun, Moon etc were travelling around a stationary Earth, which they interpreted as Earth being centre of their then "observable" universe.
4)

If possible could you try to make these answers more indepth

 

[1008]

V=HoD

Where V is the velocity at which galaxy is movign away (km/s)
Ho is hubble's constant ((67.8 km/s)/Mpc)
D is distance to galaxy (mega parasecs)

Thanks, so sub your data into the formula: v = 67.8 * 12.5 = 847.5km/s

 

[eyeseeyou]

Thanks, so sub your data into the formula: v = 67.8 * 12.5 = 847.5m/s

Cheers

 

[1008]

If possible could you try to make these answers more indepth

Umm, aren't they meant to be short answers...

 

[eyeseeyou]

Umm, aren't they meant to be short answers...

For question 3 and 4 its supposed to be long

 

[1008]

For question 3 and 4 its supposed to be long

Alright:
3) In Ancient Greece, Ptolemy was one of the first who attempted to create a model of the universe. This model was mainly created in order to explain the motion of heavenly bodies according to the Greek's understanding, and also to refine the model of the Greek astronomers before them. In this model, Ptolemy placed the Earth at the centre of the universe, with other heavenly bodies revolving around Earth in circular epicycles. The heavenly bodies included, the Sun, and The Moon, as well as other planets (but not all of them). As Earth was placed at the centre, this model is regarded as a geocentric model. However, as we know today, the model was flawed, as Earth is not the centre of the universe (not even the centre of our solar system).

One of the main reasons Ptolemy's model would've been flawed is due to the limitations in the technology available at the time. For the model, all of Ptolemy's data collected and observations made were on Earth and with his naked eye, which hindered his ability to identify all the planets and other celestial bodies in our solar system (e.g. the asteroid belt and the moons of other planets etc) and caused him to place the Earth at the centre of the then "observable universe". This is because on Earth, it looks like the Sun is revolving around Earth, causing day and night. However, it is Earth that revolves around the Sun, and its rotation causes day and night. Since then our understanding of our solar system and the universe has been enhanced due to technological innovations such as better telescopes, and our ability to send manned and unmanned ships into space has allowed us to gain a greater and more accurate understanding of the universe around us, which would've been impossible at the time. Nevertheless, Ptolemy remains one of the pioneers in mapping out a model for our universe and his contribution was crucial to the development in our knowledge of space.

EDIT: try to formulate a response for the accretion question on your own, post it here and I'll try and have a look

 

[eyeseeyou]

Alright:
3) In Ancient Greece, Ptolemy was one of the first who attempted to create a model of the universe. This model was mainly created in order to explain the motion of heavenly bodies according to the Greek's understanding, and also to refine the model of the Greek astronomers before them. In this model, Ptolemy placed the Earth at the centre of the universe, with other heavenly bodies revolving around Earth in circular epicycles. The heavenly bodies included, the Sun, and The Moon, as well as other planets (but not all of them). As Earth was placed at the centre, this model is regarded as a geocentric model. However, as we know today, the model was flawed, as Earth is not the centre of the universe (not even the centre of our solar system).

One of the main reasons Ptolemy's model would've been flawed is due to the limitations in the technology available at the time. For the model, all of Ptolemy's data collected and observations made were on Earth and with his naked eye, which hindered his ability to identify all the planets and other celestial bodies in our solar system (e.g. the asteroid belt and the moons of other planets etc) and caused him to place the Earth at the centre of the then "observable universe". This is because on Earth, it looks like the Sun is revolving around Earth, causing day and night. However, it is Earth that revolves around the Sun, and its rotation causes day and night. Since then our understanding of our solar system and the universe has been enhanced due to technological innovations such as better telescopes, and our ability to send manned and unmanned ships into space has allowed us to gain a greater and more accurate understanding of the universe around us, which would've been impossible at the time. Nevertheless, Ptolemy remains one of the pioneers in mapping out a model for our universe and his contribution was crucial to the development in our knowledge of space.

EDIT: try to formulate a response for the accretion question on your own, post it here and I'll try and have a look

You forgot Q4

 

[1008]

You forgot Q4

Alright:
3) In Ancient Greece, Ptolemy was one of the first who attempted to create a model of the universe. This model was mainly created in order to explain the motion of heavenly bodies according to the Greek's understanding, and also to refine the model of the Greek astronomers before them. In this model, Ptolemy placed the Earth at the centre of the universe, with other heavenly bodies revolving around Earth in circular epicycles. The heavenly bodies included, the Sun, and The Moon, as well as other planets (but not all of them). As Earth was placed at the centre, this model is regarded as a geocentric model. However, as we know today, the model was flawed, as Earth is not the centre of the universe (not even the centre of our solar system).

One of the main reasons Ptolemy's model would've been flawed is due to the limitations in the technology available at the time. For the model, all of Ptolemy's data collected and observations made were on Earth and with his naked eye, which hindered his ability to identify all the planets and other celestial bodies in our solar system (e.g. the asteroid belt and the moons of other planets etc) and caused him to place the Earth at the centre of the then "observable universe". This is because on Earth, it looks like the Sun is revolving around Earth, causing day and night. However, it is Earth that revolves around the Sun, and its rotation causes day and night. Since then our understanding of our solar system and the universe has been enhanced due to technological innovations such as better telescopes, and our ability to send manned and unmanned ships into space has allowed us to gain a greater and more accurate understanding of the universe around us, which would've been impossible at the time. Nevertheless, Ptolemy remains one of the pioneers in mapping out a model for our universe and his contribution was crucial to the development in our knowledge of space.

EDIT: try to formulate a response for the accretion question on your own, post it here and I'll try and have a look

This

 

[eyeseeyou]

This

Oh yeah didn't read that 1008. For the time being could you please answer my question in the prelim chem thread while I answer this question for the time being

Thanks

 

[eyeseeyou]

I don't know whether or not this answers the question directly but this is how I answered it:

As the universe was expanding and cooling, particles lost kinetic energy and began to attract each other through gravity. This formed regions of high mass and density. This region then began to attract each other nearby materials and gain mass. This process is called accretion. Due to accretion, matter in the universe formed as discrete gas clouds known as protogalaxies. As further accretion occured, galaxies were then formed. Accretion continued to happen inside galaxies to form stars i.e. our sun is formed in the milky way. To this day our universe continues to expand (14 billion years later)

 

[1008]

I don't know whether or not this answers the question directly but this is how I answered it:

As the universe was expanding and cooling, particles lost kinetic energy and began to attract each other through gravity. This formed regions of high mass and density. This region then began to attract each other nearby materials and gain mass. This process is called accretion. Due to accretion, matter in the universe formed as discrete gas clouds known as protogalaxies. As further accretion occured, galaxies were then formed. Accretion continued to happen inside galaxies to form stars i.e. our sun is formed in the milky way. To this day our universe continues to expand (14 billion years later)

Your last sentence sort of contradicts the rest of your answer. As you said, accretion is the process of matter being attracted towards each other due to gravity. This continues until the matter gets so close and compact that it starts to fuse together to make stars, planets etc. But, your last sentence refers to the Big Bang Theory, which states that everything has been moving apart and will continue to move apart. You could end your response by actually stating that the matter actually has to get extremely close to be able to fuse together to form stars, planets and other celestial bodies, the gravity of which in turn attracts more matter together and hence this process continues in certain clusters that may later form galaxies.

I don't know whether or not this answers the question directly but this is how I answered it:

As the universe was expanding and cooling, particles lost kinetic energy and began to attract each other through gravity. This formed regions of high mass and density. This region then began to attract each other nearby materials and gain mass. This process is called accretion. Due to accretion, matter in the universe formed as discrete gas clouds known as protogalaxies. As further accretion occured, galaxies were then formed. Accretion continued to happen inside galaxies to form stars i.e. our sun is formed in the milky way. To this day our universe continues to expand (14 billion years later)

This is sort of weird wording as well, as kinetic energy is the energy of movement. So if the particles "lost" kinetic energy they can't attract each other (because to attract each other, one has to "move" towards the other or vice versa). You could just say that as matter was released after the Big Bang, particles started to attract each other due to gravity.

As for the rest of the response, it's quite good You could also talk about the fact that stars would've been formed before the planets and the proof of accretion within our solar system is the asteroid belt, which is essentially "left over matter" after all the planets, moons and the Sun were formed.

 

[eyeseeyou]

Your last sentence sort of contradicts the rest of your answer. As you said, accretion is the process of matter being attracted towards each other due to gravity. This continues until the matter gets so close and compact that it starts to fuse together to make stars, planets etc. But, your last sentence refers to the Big Bang Theory, which states that everything has been moving apart and will continue to move apart. You could end your response by actually stating that the matter actually has to get extremely close to be able to fuse together to form stars, planets and other celestial bodies, the gravity of which in turn attracts more matter together and hence this process continues in certain clusters that may later form galaxies.



This is sort of weird wording as well, as kinetic energy is the energy of movement. So if the particles "lost" kinetic energy they can't attract each other (because to attract each other, one has to "move" towards the other or vice versa). You could just say that as matter was released after the Big Bang, particles started to attract each other due to gravity.

As for the rest of the response, it's quite good You could also talk about the fact that stars would've been formed before the planets and the proof of accretion within our solar system is the asteroid belt, which is essentially "left over matter" after all the planets, moons and the Sun were formed.

What would your response be 1008?