Astronomy

[Funyarinpa]

Let's not forget one of the most beautiful sides of astronomy

 

[Eclipsed]

41 minutes ago, Rooke said:

You guys are organising a trip to witness a spectacle you can't watch directly? I dunno, seems a bit weird to me  

Yer just jealous 'cuz Tay rejected your butt when you tried to go on a golf date with him!


~~


This is the Einstein's Cross, apparently it's four separate images of the same galaxy cluster because the supernova that occurred 10-billion-years-ago-but-took-5-billion-years-for-the-light-to-reach-us-coincidentally-on-11 Dec 2015 had its light distorted by a single galaxy within the cluster via gravitational lensing.

 

HOSHI MEMO

 

[Funyarinpa]

Just now, Eclipsed said:

This is the Einstein's Cross,

Baeder-Meinhof strikes again, I bought a book about astronomy and cosmology last week and was slowly trodding through that and came across that today lol

[Eclipsed]

I'll keep my fun (obvious) facts to once a week to minimalize my burning at the stake  but probably the trippiest thing I learned this week was that objects that are like 100 million light years away, when observed by us, we're actually seeing the events as they were 100 million years ago- effectively seeing into the past, just because that's how long it took for the light to reach us.

An even trippier thought would be: what if you were moving towards that 100 million light year distance object at the speed of light? How would that affect your observation? Fast forward? 

Dsfglkrdhjerwagetghj

[Flutterz]

8 minutes ago, Eclipsed said:

An even trippier thought would be: what if you were moving towards that 100 million light year distance object at the speed of light? How would that affect your observation? Fast forward?

You'd arrive there instantly... at least from your perspective.

[Funyarinpa]

1 hour ago, Flutterz said:

You'd arrive there instantly... at least from your perspective.

Something something inverse square law something something 

[Down]

5 hours ago, Eclipsed said:

An even trippier thought would be: what if you were moving towards that 100 million light year distance object at the speed of light? How would that affect your observation? Fast forward? 

Aside from what Flutterz said, if you were going towards it at not the speed of light but a bit less (let's say 0.9 times the speed of light), it would actually appear to be slower. In special relativity there's this fucked up thing called time dilation.

[solidbatman]

My interest in astronomy is actually what led me to switch majors from history to geology. I loved studying how Earth, and other planets formed in the solar system, and its just neat to picture and see what Earth looked like hundreds of millions of years ago to billions of years ago. Astronomy, though, has a lot of aspects I wasn't too keen on making a career out of, so I decided to get into geology, and study the physical history of the Earth. Of course, I'll likely end up working in a hydrology field in the end anyway  

[Funyarinpa]

27 minutes ago, solidbatman said:

My interest in astronomy is actually what led me to switch majors from history to geology. I loved studying how Earth, and other planets formed in the solar system, and its just neat to picture and see what Earth looked like hundreds of millions of years ago to billions of years ago. Astronomy, though, has a lot of aspects I wasn't too keen on making a career out of, so I decided to get into geology, and study the physical history of the Earth. Of course, I'll likely end up working in a hydrology field in the end anyway  

I just don't understand how a person can enjoy geology in the slightest. Memorization to the max from what I've seen of it. Subject matter is only slightly short of chloroform for me as well. I just don't get how it can be remotely bearable let alone something I could try to make a future out of.

[solidbatman]

Just now, Funyarinpa said:

I just don't understand how a person can enjoy geology in the slightest. Memorization to the max from what I've seen of it. Subject matter is only slightly short of chloroform for me as well. I just don't get how it can be remotely bearable let alone something I could try to make a future out of.

I'm good at memorization. Hence why I enjoy history so much as well. Plop me over into math/engineering, and I'd have the same reaction you do to geology. 

[Fred the Barber]

4 hours ago, Down said:

Aside from what Flutterz said, if you were going towards it at not the speed of light but a bit less (let's say 0.9 times the speed of light), it would actually appear to be slower. In special relativity there's this fucked up thing called time dilation.

Also, more generally:

• You'd get squashed in the direction you're going (so if you're lying down in the direction of your motion, you'd get noticeably shorter)
• Time doesn't exist as a standalone coordinate system; you can only express simultaneity of two events using the complete coordinate system of spacetime. Or as Douglas Adams put it: time is relative, lunchtime doubly so.

https://en.wikipedia.org/wiki/Lorentz_transformation#Physical_implications

[Flutterz]

6 hours ago, Down said:

Aside from what Flutterz said, if you were going towards it at not the speed of light but a bit less (let's say 0.9 times the speed of light), it would actually appear to be slower. In special relativity there's this fucked up thing called time dilation.

Would it also be blue-shifted, or does that only apply when the other object it near light speed and the observer isn't?

[Down]

11 minutes ago, Flutterz said:

Would it also be blue-shifted, or does that only apply when the other object it near light speed and the observer isn't?

It would. You moving towards the object and it being still or you being still and the object moving towards you is exactly the same, it's only a matter of perspective.

[tymmur]

Great topic. Sadly I missed it until now.

On 14/6/2016 at 9:38 PM, Eclipsed said:

And that the seasons are actually not based on Earth's distance from the sun during its yearly orbital revolution, but rather by Earth's tilt on its axis.

ie. Earth's distance to the sun during its orbit is actually the closest during January, but the reason it is Winter is because the Earth is tilted away from the sun. Likewise during Summer, we're tilted towards the sun for them maximum heat

It's more complex than that and distance does matter, though not regarding seasons. There is this physics law (naturally I forgot the name), which states that in orbit, when a planet has moves from A to B in orbit, the area A-B-Sun-A is proportional with the time it takes. (A-B is the curved one, not strait). This mean as the planet gets further away from the sun, the distance it can travel to reach the same area decreases and the planet slows down it's orbit. This is why summer is a week longer than winter because at summer it is further from the sun. That is for the northern hemisphere. It's reversed on the southern because south tilts away from the sun when north tilts towards it.

 

What makes this complex is that the difference in closest and longest from the sun isn't constant. Sometimes the difference becomes much bigger, which will give earth a quick move near the sun and a long slow one away from the sun. Because the distance becomes so much greater than it is today, it actually does affect the global temperature. The term we generally use for this event is ice age.

 

There are plenty of other interesting facts about our solar system. Mercury is the smallest planet and it looks like it used to be a big one and some major event took place and ripped off everything and only the core remain. Venus is a young planet and the surface cooled down to solidify recently in astronomical terms. I can't tell how many millions of years ago it was without looking it up, but it's like 100-150 million after multi cell life turned up on earth. Venus is also the hottest planet, having a near constant temperate of around 450 °C. It's so hot that snow there isn't water. It is some sort of metal. It's the only planet with a sunrise in west because for some odd reason it turns the wrong way around. It rotates slower around itself than around the sun, meaning a day is longer than a year. There is speculation that Venus is the aftermath of a collision between two planets, hence the odd movement/rotation and lots of leftover heat, which is only slowly escaping.

 

Rings are quite common and half the planets have them, though only the ones on Saturn are clearly visible at a great distance. Mars has two moons and the inner moon is spiraling to it's own death. Within a few million years it will crash and crease a new ring and Mars will be the only rock planet in the solar system with rings.

 

Windspeed picks up the further you get from the Sun. The 4 outer planets (the gas giants) have wind speed, which would destroy everything on Earth with the maximum recorded of 250 m/s on Neptune. Neptune also once had a storm so powerful that it made a hole in the planet's surface, like a vortex. Some of the storms on the gas giants are bigger than earth.

 

Something kicked Uranus quite hard at some point. Despite being a big and heavy gas giant, something knocked it over and it is tilted 60°. It's also the only planet with a Greek name. The rest are from Roman mythology.

 

It would seem that the same processes takes place on multiple planets/moons. Take for instance volcanoes. It's lava on earth. It comes up from underground as a liquid, cools and becomes solid on the surface. The surface slowly sinks inwards, heats up and becomes lava again. On one of the moons furthest out, the very same process takes place, only it's too cold for lava. Instead it sprays liquid methane, which behaves like lava does on earth. In between under different pressures and temperatures, different elements acts as source of volcanism. Speaking of volcanoes, the most volcanic active place in the solar system is IO, the inner moon of Jupiter. The intense gravity between the huge planet and the other 36? moons twists IO constantly and the stretch is 300 meters. This movement causes lots of friction, which heats it up and the surface has constant volcanic eruptions, often quite violently. Voyager took a picture of it, which was examined because it looked like another moon was hiding behind IO, but it turned out that lava was spraying out high above the surface and then it went to all sides and fell back, causing a shape, which made it look like a moon was present.

 

Yeah astronomy is quite interesting. There are so many facts, which are far out and absolutely mindblowing.

[tymmur]

2 hours ago, Funyarinpa said:

I just don't understand how a person can enjoy geology in the slightest.

That's the wrong attitude towards learning. With that attitude we would still be stuck in the stone age.

 

Maybe this will give an idea of why geology is also an interesting topic. It's a bit off topic for astronomy, but not really because they interact quite a bit with each other.

Spoiler

 

Spoiler

 

Spoiler

 

 

[Funyarinpa]

1 hour ago, tymmur said:

That's the wrong attitude towards learning. With that attitude we would still be stuck in the stone age.

I do get it is important, but it's just that from a personal perspective (just like history) I cannot for the life of me a modicum of interesting bit of knowledge in geography as a whole.

[Flutterz]

Heh, "stone age"

[iamnoob]

By the way. Any opinions or ideas on the idea of Dark Matter/ Energy  AKA - wehavenoideawhatthehellisgoingonsowearegoingtosoundcoolandcallthisdarkmatter? 

 

I study mostly quantum/ particle ( still Uni level so not much ) so I'm not too good with astronomy but all I can think of is that those parts of the Universe have different physical constants? Total guess so feel free to explain and discuss.

[Down]

Different physical constants is a costly hypothesis, for two reasons.

The first one is that physical constants being, well, constant, is a very fundamental thing: if physical constants vary in space, then we no longer conserve linear momentum and that has huge implications on the very structures and symmetries of the laws of physics.

The second one is that, I don't know if the math has been done or not, but you'd probably need a fairly large difference (everything lies in what exactly is 'large') in order to account for dark matter and/or energy. And there are theoretical limits to how different physical constants can be without having a completely different universe.

Doesn't mean we should rule it out, but it's less costly to hypothesize currently unknown, weakly interacting matter. There's still a huge thorn in the side of that leading hypothesis though, namely the fact that although some theories predicted the existence of particles that seemed to fit, we haven't been able to find them experimentally in the LHC & co. So yeah, nothing's really certain.

(As for dark energy I know very little about it)

[Flutterz]

What little I remember about dark energy (and I'm not even an astronomy/physics student so take this with a grain of salt) is that it's basically a hypothesis for explaining why the universe is expanding and accelerating despite the fact that you'd assume gravity would be trying to contract it, or at least decelerate it. The way it "works" is that it's a constant energy in all of spacetime, so for a while it was actually weaker than gravity, but as the universe kept expanding gravity became less powerful due to its dependence on distance, but dark energy stayed unchanged because it's constant, so it got to the point where dark energy was more powerful than gravity in terms of expanding/contracting the universe, and as it continues to expand gravity will only become weaker in comparison.

[iamnoob]

33 minutes ago, Flutterz said:

What little I remember about dark energy (and I'm not even an astronomy/physics student so take this with a grain of salt) is that it's basically a hypothesis for explaining why the universe is expanding and accelerating despite the fact that you'd assume gravity would be trying to contract it, or at least decelerate it. The way it "works" is that it's a constant energy in all of spacetime, so for a while it was actually weaker than gravity, but as the universe kept expanding gravity became less powerful due to its dependence on distance, but dark energy stayed unchanged because it's constant, so it got to the point where dark energy was more powerful than gravity in terms of expanding/contracting the universe, and as it continues to expand gravity will only become weaker in comparison.

If i remember correctly it isn't that Dark energy is more powerful but just that there's so much more of it.

 

46 minutes ago, Down said:

Different physical constants is a costly hypothesis, for two reasons.

The first one is that physical constants being, well, constant, is a very fundamental thing: if physical constants vary in space, then we no longer conserve linear momentum and that has huge implications on the very structures and symmetries of the laws of physics.

The second one is that, I don't know if the math has been done or not, but you'd probably need a fairly large difference (everything lies in what exactly is 'large') in order to account for dark matter and/or energy. And there are theoretical limits to how different physical constants can be without having a completely different universe.

Doesn't mean we should rule it out, but it's less costly to hypothesize currently unknown, weakly interacting matter. There's still a huge thorn in the side of that leading hypothesis though, namely the fact that although some theories predicted the existence of particles that seemed to fit, we haven't been able to find them experimentally in the LHC & co. So yeah, nothing's really certain.

(As for dark energy I know very little about it)

1.  Agreed, hence a wild hypothesis. Though the locations that expeience it seem to have a much higher concentration of normal matter and black holes, it is also so much further and physical constants are one thing which is only tested on a very small scale hence the hypothesis.

2. Yup, a ridiculous amount, almost 100% I think

[Flutterz]

35 minutes ago, iamnoob said:

If i remember correctly it isn't that Dark energy is more powerful but just that there's so much more of it.

Well what I heard was that its power comes from it being constant, it doesn't matter if the universe is a meter wide or a trillion light years, it still expands at the same rate due to dark energy.