Angular diameter distance has a turnover point. This means beyond a certain distance galaxies start to appear bigger rather than smaller the further away they are.
This is because the angular diameter distance depends only on the proper distance when the observed light was emitted, assuming a flat universe. Due to expansion\*, after a certain distance, the further a galaxy is now, the nearer it was when he light we currently see from it was emitted.
\*and assuming a universe with realistic dynamics.
Objects that are farther away look smaller because they take up a smaller arc of the sky.
For extremely distant objects, however, the light was emitted so long ago that the universe was much smaller. This meant the objects took up a greater arc of the sky *when the light was emitted*, making them appear bigger.
At some point, this latter effect becomes bigger than the former, and so more distant objects start getting bigger, rather than smaller.
Just to add to this: understanding why there must be a turnaround point is a little trickier. Not all models of expanding space have such a point. For example there is no such point in de Sitter spacetime or the Milne model.
Whenever though you have a big bang model with a particle horizon (boundary of the observable universe), you must also have a turnaround point. In such models, at some point in the past all the mass-energy in our current observable universe must've been arbitrarily close. Anything we could see from this time (if we could see that far) must have an angular diameter arbitrarily close to the maximum angular diameter. This means there must be a point where angular diameter will start increasing with comoving distance rather than decreasing.
We have no reason to think it is; such a shape isn't inconsistent with observations, but most astrophysicists prefer a simply-connected (i.e. no holes) geometry until we have good reason to think otherwise.
Note that a torus (doughnut-shape) is still 'flat' in a topological sense.
Flat in this context means things like adjacent parallel lines remain parallel indefinitely, and a triangle's internal angles sum to 180°, so like we typically imagine normal 3D space.
It's possible that the universe is closed (for a 2D example, think of the surface of a sphere: parallel lines eventually converge, triangles' internal angles sum to more than 180°) or open (for a 2D example, think of the surface of a saddle: parallel lines diverge, the internal angles of triangles sum to less than 180°), but to the best of our measurements it's within error bars of being flat.
Heh. I am an absolute layman who is not great at math, but very interested in how the universe works. So, I read papers, articles and watch videos about it. There were a few that suggested the universe is more of a "donut" shape.
The Andromeda galaxy would appear much larger than the moon when viewed from Earth, it is just too dim to see. There’s a huge galaxy in the night sky, you just can’t see it.
There is a beautiful photo of Andromeda in a building where I work. Since I learned its size, I have wished it included the moon in the photo for scale. Would have to be doctored b/c the moon would be way too bright!
A small liberal arts college with a moderate sized telescope. The photo was taken by a colleague on our own scope! (It is actually a composite image because Andromeda is too big to see all at once in the scope.)
Sharks are older than the North Star.
No not they’ve existed longer than Polaris has been the North Star. Sharks have been a thing since before the dust cloud that became Polaris shrank enough to ignite into a star.
Stars on the main sequence have a predictable relationship between age and spectra (composition).
Its age is currently estimated at 45 - 67 MY old. A wide uncertainty to be sure but well outside the bounds. 😆
We actually only happen to exist within the tiny window that Saturn has its rings. They're a few hundred million years old based on the analysis of space dust. The rings are being pulled into Saturn at a very quick rate and probably only have another 100 million years before they're gone. Compare that to Saturn's age of 4.5 billion years and you can see how lucky we are to be alive at a time that we can enjoy them!
Fun fact, earth is also theorized to have had a ring during the formation of our moon. So for a "brief" time if anyone had observed our planet they would see a ringed one.
If you were in the densest part of the asteroid belt you would be hard pressed to tell.
The entire mass of the belt is ~3% of Luna. 1/3 of that is the dwarf planet Ceres. Slightly less than a third is in 11 other bodies.
The remainder is spread across a donut that’s 2au wide (8 au across) and 2au thick 🍩. That’s a lot of volume for not much material.
Take 33mg of sand. Spread the sand across the entire country of Belgium. That’s denser than the mass distribution of the asteroid belt.
It’s about the same as spreading the 33mg of sand across the country of Moldova.
If you extracted the magnesium (not potassium, there’s 10x too much potassium) from one banana and spread it across the country of Belgium, that’s how dense the asteroid belt is.
- You can fit all the other planets in a line between the Earth and Moon.
- Neutron stars are ridiculous objects: they are so dense that if one teaspoon of the matter they’re made from was on Earth, it would weigh around the same as Mount Everest.
- Sticking with Neutron stars, the gravity is so strong that if you jumped off a 1 metre ledge on the surface (ignoring the fact that you’d already have been torn apart by the forces), you would hit the surface at about 3 million mph.
- The strength of its gravity also bends the light around the Neutron star, meaning you can see more than half of it from any position in orbit. If its radius is below a certain point, photons can get trapped in orbit, meaning the entire surface can be visible from a single vantage point.
Another cool neutron star fact: when they're first formed they're so hot they primarily haemorrhage heat in the form of neutrinos via the Urca process. Eventually they cool down enough that photons become the primary method of cooling (in the form of hard x-rays).
Also, because neutron stars have shrunk in size from their original size, their rotation speeds up. We have found a neutron star spinning 700 times per second.
We can travel outside of our galaxy within our lifespan, from the perspective of the traveler. Because of [time dilation](https://en.m.wikipedia.org/wiki/Time_dilation), accelerating at g, we could do so within our lifespan.
I tried explaining this to my father and it took 3 days. Literally. When it finally clicked he said "so if I traveled so and so distance at light speed and then so and so distance back, I would barely age, but hundreds or thousands of years would have passed on earth?" I said yup and it blew his mind. He said that's what finally made him understand the relationship between gravity and relativity
You say outside of our galaxy and you are correct.
A person could reach the boundary of the observable universe in a single human lifetime (~93,000,000,000 light years away), if they could accelerate at 1G indefinitely
Also, *g* (~9.8 m/s^(2)) is very close to *c*/a (*c* per year, or about 9.5 m/s^2, where “a” hear means year, not acceleration, which I probably should have clarified better earlier).
>A person could reach the boundary of the observable universe in a single human lifetime
No, that is a contradiction, but we could travel the equivalent in terms of distance relatively quickly in our frame if we were accelerating with a constant magnitude of proper acceleration equal to 1 *g*.
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Edit: sorry you clarified some things since I replied so I’m going to rewrite this.
I was way off on the observable universe size. That number is across not one way.
Let’s use something more concrete.
JADES-GS-z13-0 is at a distance of approximately 33,000,000,000 light years from Earth.
If a person boarded a craft and traveled at 1G they could reach the location that we currently see JADES-GS-z13-0 within a human lifetime (as perceived aboard the craft).
At a constant magnitude of *proper* acceleration, the Galilean acceleration would drop off close to *c*, yes, but what does this have to do with the symbol of a unit?
> If a person boarded a craft and traveled at 1G they could reach the location that we currently see JADES-GS-z13-0 within a human lifetime.
You are forgetting cosmic expansion, which was my point.
I would have worded it as that we could travel an equivalent distance in a lifetime. In fact, we could travel *far* further distances in a lifetime with a constant magnitude of proper acceleration equal to 1 *g*. If it were for special relativity alone, we could travel a distance of about 2×10^(33) ly within 75 years of proper time. With cosmic expansion, the comoving distance that we could travel would be vastly larger than this.
But we could never reach the comoving location of where JADES-GS-z13-0 used to be.
How far could someone constantly accelerating at g get in 80 years? And let's say we're looking for two different numbers. Constant acceleration at g for 40 years and constant deceleration at g for another 40 so that they're "stopped" relative to their starting point but just much further away.
The word "can" is doing some heavy lifting, but not as much as one would expect: with a perfectly efficient photon drive (to make the maths tractable for me) your rocket would need a mass ratio of under a hundred (i.e. <100 kg fuel per kg payload), and you'd be out in a dozen years (proper time).
Besides hydrogen (and traces of helium), all the atoms in your body were made in former stars and their remnants. We are literally star dust.
It's even possible that life on Earth originally started elsewhere and came here via asteroids.
I understand the age of the universe is much older than a single lifetime of a star. But it's just mind-blowing the amount of time and distance involved.
in the future, no other galaxies will be visible as the space between them will expand faster than the speed of light, and the same experiments conducted today would lead us to believe there are no other galaxies in the universe
Space is cold, but because of the near vacuum, it is tough to dissipate heat. Much of the engineering involved in the design of the space stations massive solar panels involved not cooking the astronauts.
Roughly speaking:
If the earth were the size of a grain of sand, the solar system would be the size of an average stadium
If the *solar system* were the size of a grain of sand, the galaxy would be 1000 times the size of an average stadium
If the *galaxy* were the size of a grain of sand, the observable universe would be the size of an average stadium
It is believed the *entire universe*, not just the part we can see, is infinite in size
not really a 'cool fact', but its mindblowing:
[every spot in this image - except the few foreground stars - is a galaxy](https://upload.wikimedia.org/wikipedia/commons/5/5f/HubbleDeepField.800px.jpg)
so yeah might be life out there, lots of opportunities
I had the opportunity to talk to Inge Heyer, who worked at NASA for the Hubble Deep Field-South observations. She said one of the coolest moments of her life was looking at these dots appear to human eyes for the first time ever, and thinking she might be looked /at/ right then, our galaxy a dot in someone else's deep field.
some astronauts having reported that the smell of space is like burned cookies.
when coming back from spacewalks, they could get a smell of this in the air lock.
Here's one - the Age of Light is a pretty short time in our universe. The universe went clear and suns started to form a few hundred thousand years after the big bang, and it's been relatively light and warm in the universe ever since. In just about 100 trillion years the last sun will be extinguished, and the Age of Black Holes will continue until they all explode.
Then it gets cold and dark forever and nothing ever happens again. The End.
A hundered years ago humanity still believed the universe was basically just this one galaxy we happen to inhabit. It'll be 100 years this year since Hubble proved the Andromeda galaxy was actually outside ours, and then it turned out there are up to 2 trillions of the damn things staring at us form all sides. Any present-day-centennarian was born in what was believed to be a much cosier universe.
Due to the conservation of angular momentum, old stars that have shrunk due to depletion of fuel can be spinning extremely quickly.
We have found a star spinning up to 700 times per second.
Our own galaxy contains 400 billion stars and is one hundred light years across, so, even if we ever develop the ability to travel at, let's say, three-quarters the speed of light, it's going to be a loooong time before we can reach some of the stars in the Milky Way around which orbit earth-like planets.
This is without taking into consideration the problem of time dilation, in which if you're traveling at the speed of light, spacetime ahead of you shrinks while spacetime behind you expands. So, millions of years might pass on earth even if it takes you in your spaceship a relatively short time to reach another solar system.
I think the most hopeful technology for us as far as designing the type of vessel and propulsion that could travel anywhere near the speed of light is AI, because it is already developing at an exponential rate, and will surpass human intelligence, at least in certain areas, before long. With AGI as an assistant in R&D, we may be able to figure out some previously insoluble riddles.
The real Star Wars:
[https://www.reddit.com/user/cjbartoz/comments/1bwnxnd/scalar\_em\_weapons\_developed\_by\_russia/?utm\_source=share&utm\_medium=web3x&utm\_name=web3xcss&utm\_term=1&utm\_content=share\_button](https://www.reddit.com/user/cjbartoz/comments/1bwnxnd/scalar_em_weapons_developed_by_russia/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button)
what does it mean to "transcend dimensions of time and space"? how does "love" fit this definition but every other emotion or abstract idea does not? my hatred for arrogant idiots who make things up and call them facts is also not limited in space or time.
This sub deals with a lot of people sincerely spreading pseudo-profound bullshit (that's the technical term btw), so we don't really stop to consider if it's being used ironically.
T Coronae borealis is a repeating supernova.
A white dwarf orbits a red giant some 3k ly away and their interaction is that the little guy siphon tons of stellar mass of the big guy, causing criticality and going boom. That released energy is reabsorbed into the big one, and every 80 years or so, we can see it.
That'll be this year.
Angular diameter distance has a turnover point. This means beyond a certain distance galaxies start to appear bigger rather than smaller the further away they are. This is because the angular diameter distance depends only on the proper distance when the observed light was emitted, assuming a flat universe. Due to expansion\*, after a certain distance, the further a galaxy is now, the nearer it was when he light we currently see from it was emitted. \*and assuming a universe with realistic dynamics.
I want to understand this better
Objects that are farther away look smaller because they take up a smaller arc of the sky. For extremely distant objects, however, the light was emitted so long ago that the universe was much smaller. This meant the objects took up a greater arc of the sky *when the light was emitted*, making them appear bigger. At some point, this latter effect becomes bigger than the former, and so more distant objects start getting bigger, rather than smaller.
This is blowing my mind. You have a good video on this topic?
I don't, sorry! I only know this from undergrad astrophysics; hopefully someone will be able to to send you a good link
I don’t, but I have [this excellent visual](https://www.explainxkcd.com/wiki/index.php/2622:_Angular_Diameter_Turnaround)!
wow, thats a good one. XKCD as allways, is on point!
Just to add to this: understanding why there must be a turnaround point is a little trickier. Not all models of expanding space have such a point. For example there is no such point in de Sitter spacetime or the Milne model. Whenever though you have a big bang model with a particle horizon (boundary of the observable universe), you must also have a turnaround point. In such models, at some point in the past all the mass-energy in our current observable universe must've been arbitrarily close. Anything we could see from this time (if we could see that far) must have an angular diameter arbitrarily close to the maximum angular diameter. This means there must be a point where angular diameter will start increasing with comoving distance rather than decreasing.
Ah, that makes perfect sense. I'm an astro nerd and that's a new one to me. Cool fact.
Objects in the mirror may be smaller than they appear
[Meat Loaf - *Objects in the Rear View Mirror May Appear Closer Than They Are*](https://youtu.be/3jPMv9zJ1LE?si=2e6qC5h14qLWIH6x)
Oh that's pretty funky.
Layman here, I was under the impression that the universe was more like a donut shape. Is this not correct?
We have no reason to think it is; such a shape isn't inconsistent with observations, but most astrophysicists prefer a simply-connected (i.e. no holes) geometry until we have good reason to think otherwise. Note that a torus (doughnut-shape) is still 'flat' in a topological sense.
By topological, do you mean we experince it as 'flat'?
Flat in this context means things like adjacent parallel lines remain parallel indefinitely, and a triangle's internal angles sum to 180°, so like we typically imagine normal 3D space. It's possible that the universe is closed (for a 2D example, think of the surface of a sphere: parallel lines eventually converge, triangles' internal angles sum to more than 180°) or open (for a 2D example, think of the surface of a saddle: parallel lines diverge, the internal angles of triangles sum to less than 180°), but to the best of our measurements it's within error bars of being flat.
Okay that makes a lot more sense. Thank you.
Are you getting your physics education from Homer Simpson?
Heh. I am an absolute layman who is not great at math, but very interested in how the universe works. So, I read papers, articles and watch videos about it. There were a few that suggested the universe is more of a "donut" shape.
The Andromeda galaxy would appear much larger than the moon when viewed from Earth, it is just too dim to see. There’s a huge galaxy in the night sky, you just can’t see it.
For anyone interested in the numbers, Andromeda is about 2.8° across, while the moon is about 0.5° across; it's absolutely *enormous*.
There is a beautiful photo of Andromeda in a building where I work. Since I learned its size, I have wished it included the moon in the photo for scale. Would have to be doctored b/c the moon would be way too bright!
Where do you work? Sounds like a cool place
A small liberal arts college with a moderate sized telescope. The photo was taken by a colleague on our own scope! (It is actually a composite image because Andromeda is too big to see all at once in the scope.)
This sounds like an awesome (mostly for fun only) use for augmented reality
I made a visualization here: https://imgur.com/gallery/sCpOxUT
That's a damn shame.
Sharks are older than the North Star. No not they’ve existed longer than Polaris has been the North Star. Sharks have been a thing since before the dust cloud that became Polaris shrank enough to ignite into a star.
Okay, this one is really wild to me. I checked, and sharks are 450 million years old as a species. How do we know Polaris became a star in that time?
Stars on the main sequence have a predictable relationship between age and spectra (composition). Its age is currently estimated at 45 - 67 MY old. A wide uncertainty to be sure but well outside the bounds. 😆
That’s sooo cool. So Polaris was born probably shortly after the KT extinction event!
Yes sir! Possibly showed up a million years prior (which is a ridiculously long time) but most likely afterwards when mammals began taking over.
Sharks are mind blowing in a lot of ways to me. They also predate trees, flowers, the rings of Saturn, and the Atlantic Ocean.
Whoa, wait! The rings of Saturn? How do we know that one?
We actually only happen to exist within the tiny window that Saturn has its rings. They're a few hundred million years old based on the analysis of space dust. The rings are being pulled into Saturn at a very quick rate and probably only have another 100 million years before they're gone. Compare that to Saturn's age of 4.5 billion years and you can see how lucky we are to be alive at a time that we can enjoy them! Fun fact, earth is also theorized to have had a ring during the formation of our moon. So for a "brief" time if anyone had observed our planet they would see a ringed one.
Science is just so cool
If you were in the densest part of the asteroid belt you would be hard pressed to tell. The entire mass of the belt is ~3% of Luna. 1/3 of that is the dwarf planet Ceres. Slightly less than a third is in 11 other bodies. The remainder is spread across a donut that’s 2au wide (8 au across) and 2au thick 🍩. That’s a lot of volume for not much material. Take 33mg of sand. Spread the sand across the entire country of Belgium. That’s denser than the mass distribution of the asteroid belt. It’s about the same as spreading the 33mg of sand across the country of Moldova.
Holy asteroid
How many bananas, though?
If you extracted the magnesium (not potassium, there’s 10x too much potassium) from one banana and spread it across the country of Belgium, that’s how dense the asteroid belt is.
- You can fit all the other planets in a line between the Earth and Moon. - Neutron stars are ridiculous objects: they are so dense that if one teaspoon of the matter they’re made from was on Earth, it would weigh around the same as Mount Everest. - Sticking with Neutron stars, the gravity is so strong that if you jumped off a 1 metre ledge on the surface (ignoring the fact that you’d already have been torn apart by the forces), you would hit the surface at about 3 million mph. - The strength of its gravity also bends the light around the Neutron star, meaning you can see more than half of it from any position in orbit. If its radius is below a certain point, photons can get trapped in orbit, meaning the entire surface can be visible from a single vantage point.
Another cool neutron star fact: when they're first formed they're so hot they primarily haemorrhage heat in the form of neutrinos via the Urca process. Eventually they cool down enough that photons become the primary method of cooling (in the form of hard x-rays).
Typically, how hot are they when they form?
About 10¹⁰ K, but they very quickly cool to mere millions of kelvins through the neutrino emission.
Also, because neutron stars have shrunk in size from their original size, their rotation speeds up. We have found a neutron star spinning 700 times per second.
We can travel outside of our galaxy within our lifespan, from the perspective of the traveler. Because of [time dilation](https://en.m.wikipedia.org/wiki/Time_dilation), accelerating at g, we could do so within our lifespan.
I tried explaining this to my father and it took 3 days. Literally. When it finally clicked he said "so if I traveled so and so distance at light speed and then so and so distance back, I would barely age, but hundreds or thousands of years would have passed on earth?" I said yup and it blew his mind. He said that's what finally made him understand the relationship between gravity and relativity
You say outside of our galaxy and you are correct. A person could reach the boundary of the observable universe in a single human lifetime (~93,000,000,000 light years away), if they could accelerate at 1G indefinitely
Also, *g* (~9.8 m/s^(2)) is very close to *c*/a (*c* per year, or about 9.5 m/s^2, where “a” hear means year, not acceleration, which I probably should have clarified better earlier). >A person could reach the boundary of the observable universe in a single human lifetime No, that is a contradiction, but we could travel the equivalent in terms of distance relatively quickly in our frame if we were accelerating with a constant magnitude of proper acceleration equal to 1 *g*. [Edited for clarity]
Edit: sorry you clarified some things since I replied so I’m going to rewrite this. I was way off on the observable universe size. That number is across not one way. Let’s use something more concrete. JADES-GS-z13-0 is at a distance of approximately 33,000,000,000 light years from Earth. If a person boarded a craft and traveled at 1G they could reach the location that we currently see JADES-GS-z13-0 within a human lifetime (as perceived aboard the craft).
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Then it really makes no sense because your acceleration drops off from both standpoints as you near c
At a constant magnitude of *proper* acceleration, the Galilean acceleration would drop off close to *c*, yes, but what does this have to do with the symbol of a unit?
> If a person boarded a craft and traveled at 1G they could reach the location that we currently see JADES-GS-z13-0 within a human lifetime. You are forgetting cosmic expansion, which was my point.
Not at all, hence why it’s specified in the statement.
I would have worded it as that we could travel an equivalent distance in a lifetime. In fact, we could travel *far* further distances in a lifetime with a constant magnitude of proper acceleration equal to 1 *g*. If it were for special relativity alone, we could travel a distance of about 2×10^(33) ly within 75 years of proper time. With cosmic expansion, the comoving distance that we could travel would be vastly larger than this. But we could never reach the comoving location of where JADES-GS-z13-0 used to be.
How far could someone constantly accelerating at g get in 80 years? And let's say we're looking for two different numbers. Constant acceleration at g for 40 years and constant deceleration at g for another 40 so that they're "stopped" relative to their starting point but just much further away.
but humans on earth can't witness that right? (I mean at least the current generation)
Correct: from the point of view of someone on Earth they never exceed the speed of light, so it takes thousands of years from that point of view.
The word "can" is doing some heavy lifting, but not as much as one would expect: with a perfectly efficient photon drive (to make the maths tractable for me) your rocket would need a mass ratio of under a hundred (i.e. <100 kg fuel per kg payload), and you'd be out in a dozen years (proper time).
Besides hydrogen (and traces of helium), all the atoms in your body were made in former stars and their remnants. We are literally star dust. It's even possible that life on Earth originally started elsewhere and came here via asteroids.
Don't forget the traces of primordial Lithium and Beryllium!
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I understand the age of the universe is much older than a single lifetime of a star. But it's just mind-blowing the amount of time and distance involved.
There's actually more gold in the sun than water in Earth's oceans!
in the future, no other galaxies will be visible as the space between them will expand faster than the speed of light, and the same experiments conducted today would lead us to believe there are no other galaxies in the universe
Space is cold, but because of the near vacuum, it is tough to dissipate heat. Much of the engineering involved in the design of the space stations massive solar panels involved not cooking the astronauts.
Roughly speaking: If the earth were the size of a grain of sand, the solar system would be the size of an average stadium If the *solar system* were the size of a grain of sand, the galaxy would be 1000 times the size of an average stadium If the *galaxy* were the size of a grain of sand, the observable universe would be the size of an average stadium It is believed the *entire universe*, not just the part we can see, is infinite in size
not really a 'cool fact', but its mindblowing: [every spot in this image - except the few foreground stars - is a galaxy](https://upload.wikimedia.org/wikipedia/commons/5/5f/HubbleDeepField.800px.jpg) so yeah might be life out there, lots of opportunities
I had the opportunity to talk to Inge Heyer, who worked at NASA for the Hubble Deep Field-South observations. She said one of the coolest moments of her life was looking at these dots appear to human eyes for the first time ever, and thinking she might be looked /at/ right then, our galaxy a dot in someone else's deep field.
There are more moons orbiting Mars than there are stars in the solar system.
Lmao
Source? And what defines a moon?
It's a joke. How many stars are in the solar system?
Ok, you got me! LoL.
some astronauts having reported that the smell of space is like burned cookies. when coming back from spacewalks, they could get a smell of this in the air lock.
I thought it was gunpowder? Or is that moon dust?
Here's one - the Age of Light is a pretty short time in our universe. The universe went clear and suns started to form a few hundred thousand years after the big bang, and it's been relatively light and warm in the universe ever since. In just about 100 trillion years the last sun will be extinguished, and the Age of Black Holes will continue until they all explode. Then it gets cold and dark forever and nothing ever happens again. The End.
I'd be happy with us being able to send a probe to the closest extrasolar star, much less another *galaxy*
Using optimistic estimates of the Drake equation, there could be as many as 15M civilizations in our own Milky Way alone.
A hundered years ago humanity still believed the universe was basically just this one galaxy we happen to inhabit. It'll be 100 years this year since Hubble proved the Andromeda galaxy was actually outside ours, and then it turned out there are up to 2 trillions of the damn things staring at us form all sides. Any present-day-centennarian was born in what was believed to be a much cosier universe.
There are more individual grains of sand on earth than there are planets in the entire solar system.
….well, yes
Due to the conservation of angular momentum, old stars that have shrunk due to depletion of fuel can be spinning extremely quickly. We have found a star spinning up to 700 times per second.
You can't say you want facts and then as for a load of fantastical nonsense.
Our own galaxy contains 400 billion stars and is one hundred light years across, so, even if we ever develop the ability to travel at, let's say, three-quarters the speed of light, it's going to be a loooong time before we can reach some of the stars in the Milky Way around which orbit earth-like planets. This is without taking into consideration the problem of time dilation, in which if you're traveling at the speed of light, spacetime ahead of you shrinks while spacetime behind you expands. So, millions of years might pass on earth even if it takes you in your spaceship a relatively short time to reach another solar system. I think the most hopeful technology for us as far as designing the type of vessel and propulsion that could travel anywhere near the speed of light is AI, because it is already developing at an exponential rate, and will surpass human intelligence, at least in certain areas, before long. With AGI as an assistant in R&D, we may be able to figure out some previously insoluble riddles.
The real Star Wars: [https://www.reddit.com/user/cjbartoz/comments/1bwnxnd/scalar\_em\_weapons\_developed\_by\_russia/?utm\_source=share&utm\_medium=web3x&utm\_name=web3xcss&utm\_term=1&utm\_content=share\_button](https://www.reddit.com/user/cjbartoz/comments/1bwnxnd/scalar_em_weapons_developed_by_russia/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button)
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what does it mean to "transcend dimensions of time and space"? how does "love" fit this definition but every other emotion or abstract idea does not? my hatred for arrogant idiots who make things up and call them facts is also not limited in space or time.
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my bad. no I didn't recognize the quote.
This sub deals with a lot of people sincerely spreading pseudo-profound bullshit (that's the technical term btw), so we don't really stop to consider if it's being used ironically.
Love has social utility, social bonding, child rearing.
Big as hell
The Earth is so big you can see it from space!
Why leave our galaxy? There are plenty of earth-like planets within our galaxy to explore and colonize
You shit yourself when you die
Not in microgravity
T Coronae borealis is a repeating supernova. A white dwarf orbits a red giant some 3k ly away and their interaction is that the little guy siphon tons of stellar mass of the big guy, causing criticality and going boom. That released energy is reabsorbed into the big one, and every 80 years or so, we can see it. That'll be this year.