Been a great fan of this podcast as well. glad to see he continued after the ABC cancelled.
Space Daily is pretty good website as well
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Astronomy General Space Discussion
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Space Daily is pretty good website as well
- Mar 30, 2013
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Generic shooting star post, was there a noted breakup of something on Tuesday?
I remember reading Japan from memory had the best view of the show, still I managed to catch about three in which succession heading West coming from the North
I've tried looking for something detailed but all I can find are old Skylab articles
I remember reading Japan from memory had the best view of the show, still I managed to catch about three in which succession heading West coming from the North
I've tried looking for something detailed but all I can find are old Skylab articles
Crankyhawk
Hall of Famer
I'd visualised it as infinite bubbles bouncing around another undefined higher dimensional space with no current way to shift bubbles. Bubbles bud off for each decision made (quantum uncertainty)
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telsor
Hall of Famer
They decided not to do the burn, so still going with 53 day orbits (rather than 19).
They also shutdown everything they could after the last close approach resulted in the computer rebooting....problem found, but not patched yet.
They say they're still getting good science though, so all good there. (Mind you, they'd probably say that regardless)
Crankyhawk
Hall of Famer
Each universe is a bubble
- Apr 30, 2016
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Two cars driving towards each other. Car A is doing 60km/h, car B is doing 70km/h. They are approaching each other at 130km/h.
Galaxies aren't stationary.
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Saying they are moving away faster than the speed of light is not true, but I thought I'd try and help you out anyway.
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- Oct 30, 2010
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he's already explained this to you once.
Just a personal story.....
I have always had an interest in astronomy and science from a very early age.
My first recollection of astronomy was sitting out the back yard with my dear old Grand mother looking up at the summer night stars of the constellation of the "Three Sisters". It wasn't until decades later that I discovered the Orion nebular was the domain of these siblings. It left me wondering how many generations had passed on their unique stories about these 3 particular stars. They are nothing extra ordinary in astronomy except that they form a striking pattern that stands out amongst the Southern summer constellations. I now understand that they are only a line of sight phenomenon discernable only from our point of view. But when I was 8 years old I had no comprehension of this. These 3 stars had a special meaning for me.
My Grand Mother was a religious believer to the extent that she had a Jesus stature on her mantle piece. But never attended church...to my knowledge.
Other than that she was a very level headed but strict Matriarch of the family. My Grand Mother was born in the 1880s but was very interested in the night sky. Everything I knew about astronomy from an early age was learnt from those summer nights in the back yard.
As I got older I read books about science and astronomy written up until the mid 1960s. I must admit it was a lot easier in those days to number the moons of each planet of the solar system. I remember in the mid 60s jupiter had 12 known moons (currently 67) and saturn had 9 moons (53) orbiting the planet.
This of course was before the pioneer and Voyager spacecraft were launched towards the outer planets of the solar system. Back then our only kowledge of the stars and planets was gained from earth bound telescopes. So at the age of 8 years old I foolishly believed I knew as much as there was to know about astronomy. I kept reading and reading and found nothing new for a very long time. I could name each of the 9 planets (back then) in order of our solar system. I also knew all about Halleys comet and the year it would next appear(1986) I could also tell anyone who asked when it's previos sighting was(1910) or its next sighting would take place. I was a regular know it all when it came to space based facts. So I thought.
Fortunately for astronomy and knowledge in general discovery never ceases. 2017 is a completely different era to my humble recollection of the mid 60s.
The ammount of data now captured from the cosmos is extra ordinary. It's really a little daunting to someone like me with just a very basic knowledge of the sciences. The instruments to gather the information emitted from the cosmos are a quantum leap over the primitive means of the 60s.
I fondly remember my early childhood space instruments were nothing more than a pair of young sharp eyes and a deck chair. But made all the more interesting by an ederly lady astronomer who shared her 19th century understanding of the universe with her grand son.
I have always had an interest in astronomy and science from a very early age.
My first recollection of astronomy was sitting out the back yard with my dear old Grand mother looking up at the summer night stars of the constellation of the "Three Sisters". It wasn't until decades later that I discovered the Orion nebular was the domain of these siblings. It left me wondering how many generations had passed on their unique stories about these 3 particular stars. They are nothing extra ordinary in astronomy except that they form a striking pattern that stands out amongst the Southern summer constellations. I now understand that they are only a line of sight phenomenon discernable only from our point of view. But when I was 8 years old I had no comprehension of this. These 3 stars had a special meaning for me.
My Grand Mother was a religious believer to the extent that she had a Jesus stature on her mantle piece. But never attended church...to my knowledge.
Other than that she was a very level headed but strict Matriarch of the family. My Grand Mother was born in the 1880s but was very interested in the night sky. Everything I knew about astronomy from an early age was learnt from those summer nights in the back yard.
As I got older I read books about science and astronomy written up until the mid 1960s. I must admit it was a lot easier in those days to number the moons of each planet of the solar system. I remember in the mid 60s jupiter had 12 known moons (currently 67) and saturn had 9 moons (53) orbiting the planet.
This of course was before the pioneer and Voyager spacecraft were launched towards the outer planets of the solar system. Back then our only kowledge of the stars and planets was gained from earth bound telescopes. So at the age of 8 years old I foolishly believed I knew as much as there was to know about astronomy. I kept reading and reading and found nothing new for a very long time. I could name each of the 9 planets (back then) in order of our solar system. I also knew all about Halleys comet and the year it would next appear(1986) I could also tell anyone who asked when it's previos sighting was(1910) or its next sighting would take place. I was a regular know it all when it came to space based facts. So I thought.
Fortunately for astronomy and knowledge in general discovery never ceases. 2017 is a completely different era to my humble recollection of the mid 60s.
The ammount of data now captured from the cosmos is extra ordinary. It's really a little daunting to someone like me with just a very basic knowledge of the sciences. The instruments to gather the information emitted from the cosmos are a quantum leap over the primitive means of the 60s.
I fondly remember my early childhood space instruments were nothing more than a pair of young sharp eyes and a deck chair. But made all the more interesting by an ederly lady astronomer who shared her 19th century understanding of the universe with her grand son.
Better Loosen Up
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Strapping Young Lad
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Been there, done that.
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What we can see is finite due to the restriction of travelling light. There is no know limit to space only what we can see.
Space was thougt of as a bubble due to being able see in all directions with us in the centre, but this is like thinking the earth is the centre of the solar system.
So we can't say for certain that the universe is a round bubble, all we do know is that it appears to be expanding.
Taylor
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The speed of light is just a function of distance over time.
That distance being 1 unit of space per second, as an example. If that unit of space extends from the Earth to the Sun (one astronomical unit [AU]) or has 'extended' in the perspective of the observer to span the sun to Neptune then light still takes the same time to pass it.
There is a phenomena where electromagnetic waves lose energy the further they travel which means eventually the whole universe will be dark
One of the misnomers about Einstein's relativity is that the speed of light is an absolute speed limit. It largely is within spacetime, but not necessarily between two objects located within spacetime.
The main reason for this is the expansion of the Universe. As the Universe expands, spacetime is 'created' uniformly. This means that, between two celestial objects, more spacetime is created per unit time if the objects are further apart. It also means that, if a photon of light leaves one object (A) travelling towards another (B), it will have to transverse an ever expanding region of space to reach the object B.
If objects A and B are sufficiently distant from one another, the photon will never reach object B, as more spacetime will be created than a photon can traverse at its maximum speed (the speed of light).
This creates the phenomena known as the 'observable' universe, which is the Universe of objects close enough to us that we can 'see' them (i.e. Not too far away so their photons can't reach us). Outside of the observable universe lies the rest of our universe, which we can't observe directly as it is receding from us at too great a velocity.
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- Sep 29, 2016
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Kinda what I was saying also, but much better!
Further to what yo are saying about the universe expanding and it taking longer for light to reach us, would this explain the belief the the expansion of the universe is slowing down? Does it just appear to be slowing down because it is taking the light longer to reach us?
I think there is the assumption that the pull of gravity is slowing the expansion down, but that is on the assumption there isn't something exerting a gravitational pull in the other direction beyond the observable universe.
Ah hell my brains starting to melt again.
The rate of expansion of the universe is actually speeding up. The work that led to this discovery was done simultaneously by two teams of researchers using the Hubble Space Telescope in the mid 90's to observe distant type 1A supernovae (Sn1A), which are very bright standard candles (i.e. they have a known luminousity, so can be used to estimate distance - the dimmer they appear, the further away they are). Both teams found (unexpectedly) that the further away the Sn1A, the faster it was receding from us, thus showing that the rate of expansion of the universe has increased over time. The graph below shows their data; you will see that the relationship between distance (y-axis) and redshift (equivalent to rate of recessional velocity caused by expansion of universe) is slightly curved upwards. If the rate of expansion had been constant over time, this would be a straight line relationship.
This work won both teams the Nobel Prize for Physics in 2011; one of the recipients was Prof. Brian Schmidt from ANU. He gives public talks - usually free entry at universities and/or schools - all around Australia quite regularly, and is an excellent speaker; worth checking out if you have an opportunity. The summary from the Nobel committee of their work and its significance is worth reading - link here
The importance of their work was that it 'validated' the existence of 'dark energy' and revived the use of the cosmological constant (the Omega term shown on the graph) that Einstein had included in his initial equations for General Relativity, but later had disowned and called 'his greatest mistake' when Edwin Hubble showed that the universe was expanding at an apparently constant rate in the early 1930's.
It doesn't contradict the big bang theory at all, although both teams of researchers were expecting to find that the acceleration would be constant or slowing down (leading to a 'big crunch' in the future). Thus they waited, got extra data and double/triple checked their results before publishing to show that the acceleration is increasing over time; the revolutionary nature of the results is what earned them the Nobel Prize.
Subsequent work on cosmological modelling has 'normalised' this as the standard Big Bang model, supported by later data (e.g. the Cosmic Microwave Background radiation maps produced by the WMAP and Planck satellites). There are always those who question and query if this is the truth (there was a paper recently claiming that their model was incorrect that has been rebutted scientifically and mathematically by the Nobel Prize winners - good scientific practice to have questioning and rebuttal), but their findings haven't been significantly challenged as of the current day.
The graph below is based on the WMAP data, and shows four possible scenarios for the relative size of the universe over time based on different amounts of mass density (Omega m; mass density = 'normal' baryonic matter + dark matter; matter that is gravitationally attractive and slows down the expansion of the universe through gravitational attraction) and energy density (Omega v; 'dark energy'; the energy of spacetime that is 'repulsive', i.e. speeds up expansion as more spacetime is created). All four lines pass through the current size of the universe at the current time, but have different ages based on how the relative amounts of attractive vs. repulsive forces act on the universe. For example, the yellow line shows a 'closed' universe with no dark energy and more mass than our universe is thought to contain; this type of universe would have a deceleration of expansion over time, leading to a 'big crunch'. The blue line shows a universe with constant expansion and no dark energy; the most popular model before the discovery of accelerating expansion. The red line shows the current most likely model; a universe whose rate of expansion will increase over time due to more space being created, leading to an increase in 'dark energy', which creates a repulsive force based on the amount of space in existence; more space = more repulsive force = faster rate of expansion.
