Astronomy & Space Exploration

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A supernova remnant captured by CSIRO’s Askap radio telescope. The remnant is about 100 light-years wide and could have exploded in the Neolithic era. Photograph: CSIRO’s ASKAP radio telescope

https://www.theguardian.com/austral...oduces-fantastic-picture-of-supernova-remnant
 
nimic said:
Surprisingly, no! There would still be some neutron stars still around, and black holes will last for a long, long time still. The largest could last for as long as 10^100 years, otherwise known as 10 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 years (I think I got that right).

There would be no star formation though, so it wouldn't be a very fun universe to hang out in.
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How do you know all this stuff......I have to read it a number of times just to get the context of what you are saying.
 
Badunk said:
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Thank you. I have watched it again even though I had seen it earlier. A beautiful but chilling insight into the future.

I do wonder and worry at the same time about the more short term future. In particular how humanity is going to deal with the absolute biggest problem staring us in the face; that of climate change which continually seems to get pushed to the back of the que due to constant emerging problems.

Politicians and people treat it as if we try to forget about it and it will quietly go away. Which of course it most certainly will not.

We are all living through extremely dangerous times and seem happy to sleep walk as if nothing is going to change.
 
nimic said:
I've read a few books, read some articles, watched a few lectures on YouTube. But mostly I know just enough to sound like I know what I'm talking about. I'm no kind of physicist or scientist, so I know my limitations.

There's actually a pretty solid Wikipedia article on this exact topic
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Similar for me.
Ever since I was a kid I have always been interested in the Cosmos. And grew up during the Apollo space flights.
And my interest has broadened out to attempt to comprehend how our Universe works and how it started.
I am a retired Gas Turbine (Military) engineer, so always want to understand the mechanics of things in relative detail; how they are supposed to work and why they didn't.

We live in an age where there is so much information available if only you know where to look.
I always read your inputs with great interest.
 
Buster15 said:
Similar for me.
Ever since I was a kid I have always been interested in the Cosmos. And grew up during the Apollo space flights.
And my interest has broadened out to attempt to comprehend how our Universe works and how it started.
I am a retired Gas Turbine (Military) engineer, so always want to understand the mechanics of things in relative detail; how they are supposed to work and why they didn't.

We live in an age where there is so much information available if only you know where to look.
I always read your inputs with great interest.
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Growing up during Apollo must have been quite something, I can only imagine.

Judging by your posts in this thread, I think you'd enjoy The End of Everything (Astrophysically Speaking) by Katie Mack. It's not about how the Universe started, but how it's (maybe) going to end. It's a fun, well-written book, and she makes some pretty complex stuff easy to understand.

I always read your inputs with great interest.
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I appreciate that! I do enjoy hearing what you have to say on things as well, particularly since you're from a different generation than most people on here.
 
nimic said:
Growing up during Apollo must have been quite something, I can only imagine.

Judging by your posts in this thread, I think you'd enjoy The End of Everything (Astrophysically Speaking) by Katie Mack. It's not about how the Universe started, but how it's (maybe) going to end. It's a fun, well-written book, and she makes some pretty complex stuff easy to understand.



I appreciate that! I do enjoy hearing what you have to say on things as well, particularly since you're from a different generation than most people on here.
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I will certainly take a look at that.
None of my friends and family are even remotely interested in this type of subject. And so this is one of my main sources of content and interest.

The space programme during the 1960's really want something. Looking back at that programme, from the Kennedy speech to Apollo 11 was just mind-blowing. A massive risk because of the timescales.

And during the '60/70's, everything seemed possible. Including supersonic flight in Concorde, where I had the privilege of working on (Olympus 593 engines).

Now, everything seems impossible or is too much of a risk.
 
Frosty said:
I can follow this stuff up to a level but I always end up getting hopelessly lost. I know that a lot of energy can produce a black hole - I presume all that energy would wipe out all stars and planets within a ridiculous area?
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Yep, for all intents and purposes. That bit was meant to underscore the ultimate illogicality of the thought experiment. You will need well-nigh infinite amounts of energy to accelerate matter that will have well-nigh infinite mass as it approaches the speed of light. No amount of concentrated energy will ever be enough; if you could somehow cannibalize every source of energy in a finite (in all probability) universe, it would still not be enough.
 
That'sHernandez said:
The same thing happens with the Earth and its orbit around the Sun when it reaches its perihelion, it’s the conservation of energy in the angular momentum of an elliptical orbit
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Or a constant parabola traveling through a curved geodesic in space time.
 
Invictus said:
Yep, for all intents and purposes. That bit was meant to underscore the ultimate illogicality of the thought experiment. You will need well-nigh infinite amounts of energy to accelerate matter that will have well-nigh infinite mass as it approaches the speed of light. No amount of concentrated energy will ever be enough; if you could somehow cannibalize every source of energy in a finite (in all probability) universe, it would still not be enough.
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So if one could travel at the speed of light for a small time and then come to rest would they -due to special relativity, see the end of time and the universe. It makes sense yet hard to digest, I suppose
 
giggs-beckham said:
So if one could travel at the speed of light for a small time and then come to rest would they -due to special relativity, see the end of time and the universe. It makes sense yet hard to digest, I suppose
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Sure, but the end is rather anticlimactic. Technically I guess you would say that the heat death of the Universe is also the end of time, as there would be no potential for change, and thus time becomes meaningless.
 
nimic said:
Sure, but the end is rather anticlimactic. Technically I guess you would say that the heat death of the Universe is also the end of time, as there would be no potential for change, and thus time becomes meaningless.
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So if no measurable change occurs in the universe no time passes? Not sure about that thought experiment to be honest.
I don't believe that if you could travel at the speed of light for a brief moment in your relative frame of refference you could reach any point in the universe instantly! And that if you got to that point in space you would be at the end of time itself!
 
giggs-beckham said:
So if no measurable change occurs in the universe no time passes? Not sure about that thought experiment to be honest.
I don't believe that if you could travel at the speed of light for a brief moment in your relative frame of refference you could reach any point in the universe instantly! And that if you got to that point in space you would be at the end of time itself!
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You could say that time does pass, but with no change the concept almost doesn't make sense. At that point nothing is ever going to happen again, forever. It's also not no measurable change, it's literally no change. Otherwise you're not quite at the heat death of the Universe. Although of course, if you're still around then there's still potential for change.

It's an interesting thought experiment. The immediately almost at the speed of light, then immediately not thing isn't very likely, but theoretically you can personally explore a large part of the galaxy if you've just got a ship that can accelerate at 1G for a few years - which we're very far from doing. And also if your ship can survive a collision with a micrometeoroid at nearly the speed of light - which we're also very far from doing. The closer you can get to the speed of light, the more you can explore. You'd need very close to like... get to Andromeda. You'd need 99.99999999% for that trip to take 35 years in your frame of reference, and that's... yeah it's a lot.
 
nimic said:
You could say that time does pass, but with no change the concept almost doesn't make sense. At that point nothing is ever going to happen again, forever. It's also not no measurable change, it's literally no change. Otherwise you're not quite at the heat death of the Universe. Although of course, if you're still around then there's still potential for change.

It's an interesting thought experiment. The immediately almost at the speed of light, then immediately not thing isn't very likely, but theoretically you can personally explore a large part of the galaxy if you've just got a ship that can accelerate at 1G for a few years - which we're very far from doing. And also if your ship can survive a collision with a micrometeoroid at nearly the speed of light - which we're also very far from doing. The closer you can get to the speed of light, the more you can explore. You'd need very close to like... get to Andromeda. You'd need 99.99999999% for that trip to take 35 years in your frame of reference, and that's... yeah it's a lot.
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What's the immediately almost at the speed of light then not thing? And if travelling at the speed of light your time would be zero so some on here say you could reach any point in space instantly but when you got there you'd arrive at the end of time.
In your andromeda mission 35 years would pass for you but how much would've passed for the observer in a stationary reference frame?
 
giggs-beckham said:
What's the immediately almost at the speed of light then not thing? And if travelling at the speed of light your time would be zero so some on here say you could reach any point in space instantly but when you got there you'd arrive at the end of time.
In your andromeda mission 35 years would pass for you but how much would've passed for the observer in a stationary reference frame?
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I meant the sci-fi "light speed at the press of a button". To get to "the end of time", or basically the heat death of the universe, you'd also have to be going extremely close to the speed of light. @Invictus pointed out that the energy required to get that close would be impossibly high.

In the Andromeda mission, 2.5 million years would pass for the observer (Andromeda being 2.5million light years away, and you travelling close to the speed of light).
 
nimic said:
I meant the sci-fi "light speed at the press of a button". To get to "the end of time", or basically the heat death of the universe, you'd also have to be going extremely close to the speed of light. @Invictus pointed out that the energy required to get that close would be impossibly high.

In the Andromeda mission, 2.5 million years would pass for the observer (Andromeda being 2.5million light years away, and you travelling close to the speed of light).
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I worded it wrong. Basically how far into the future would you go if you light sped it to Andromeda
 
giggs-beckham said:
I worded it wrong. Basically how far into the future would you go if you light sped it to Andromeda
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Infinitely, once you hit the speed of light time effecivetly stops in your frame of reference and would move infinitly fast outside of it. As far as every photon is concerned, they've just been created.
 
nimic said:
You would get 2.5 million years into the future, basically.
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Got to be this and not the end of time itself. I mean in the heat death of the Universe scenario time still ticks by doesn't it?
If we sent a craft out at light speed with a passenger, within a static warp bubble or something to a distance of 1 light year and it came back at c also, then for us 2 years would've passed from departure to return. The man on board would experience no time passing thus he's travelled 2 years into the future.
 
giggs-beckham said:
Got to be this and not the end of time itself. I mean in the heat death of the Universe scenario time still ticks by doesn't it?
If we sent a craft out at light speed with a passenger, within a static warp bubble or something to a distance of 1 light year and it came back at c also, then for us 2 years would've passed from departure to return. The man on board would experience no time passing thus he's travelled 2 years into the future.
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You would have to invent a complete set of laws of physics to be able to attempt this. And then fail.
As I am sure you know.
 
Buster15 said:
You would have to invent a complete set of laws of physics to be able to attempt this. And then fail.
As I am sure you know.
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To go the speed of light, yes. But it's theoretically possible to get very, very close. All we need is a source of power that can accelerate a ship constantly for a few years (probably quite a few years if you want to get really close to the speed of light, like "visiting Andromeda" close), and a ship that can handle collisions with everything that actually exists in a supposed vacuum. At 99.999% the speed of light, a tiny thing might hurt a lot. In lieu of sci-fi shields, you might put an iceberg on the front of your ship, for example. Or just make the front really, really, really thick with a really, really, really strong material.

Easy! :angel:
 
nimic said:
To go the speed of light, yes. But it's theoretically possible to get very, very close. All we need is a source of power that can accelerate a ship constantly for a few years (probably quite a few years if you want to get really close to the speed of light, like "visiting Andromeda" close), and a ship that can handle collisions with everything that actually exists in a supposed vacuum. At 99.999% the speed of light, a tiny thing might hurt a lot. In lieu of sci-fi shields, you might put an iceberg on the front of your ship, for example. Or just make the front really, really, really thick with a really, really, really strong material.

Easy! :angel:
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Is it really possible for something with mass to get that close to the SOL.

Maybe if under the gravitational pull of a Black Hole.
But I thought that it was only Photons that travel at that speed.
 
Buster15 said:
Is it really possible for something with mass to get that close to the SOL.

Maybe if under the gravitational pull of a Black Hole.
But I thought that it was only Photons that travel at that speed.
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Only photons travel at the speed of light, but there's nothing in the way of getting to 99%, or 99.9%, or even further. You just need enough acceleration for a long enough time. If you accelerate at 1G (nothing fundamental about it, just a nice way to simulate Earth gravity) for a year, you'd be at 77%, after two years 97% (trusting someone else's calculations here, but the math can be done . . . just not by me). After 12 years, you would apparently be going 99.999999996% the speed of light.

Of course, accelerating a starship for 12 years at 1G (9.8 meters per second per second) would take an absolutely stupid amount of power. You'd basically have to have nuclear fusion, or something better (like theoretical antimatter shenanigans). And also remember that if you want to stop somewhere, you'll have to decelerate for exactly as long as you accelerated. That's actually probably the ideal way of travelling space: accelerate half the way, then turn around and decelerate the rest. That way you get gravity for the entire trip.
 
Buster15 said:
You would have to invent a complete set of laws of physics to be able to attempt this. And then fail.
As I am sure you know.
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Practically speaking obviously not possible. I was more talking the principle of what would be experienced.
 
Tibs said:
When are the next JWST pics being released?
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I don't think that there will be that kind of schedule. JWST does science work and pictures will be released along scientific results based on them. It’s simply to expensive to regularly do PR images.
 
nimic said:
Only photons travel at the speed of light, but there's nothing in the way of getting to 99%, or 99.9%, or even further. You just need enough acceleration for a long enough time. If you accelerate at 1G (nothing fundamental about it, just a nice way to simulate Earth gravity) for a year, you'd be at 77%, after two years 97% (trusting someone else's calculations here, but the math can be done . . . just not by me). After 12 years, you would apparently be going 99.999999996% the speed of light.

Of course, accelerating a starship for 12 years at 1G (9.8 meters per second per second) would take an absolutely stupid amount of power. You'd basically have to have nuclear fusion, or something better (like theoretical antimatter shenanigans). And also remember that if you want to stop somewhere, you'll have to decelerate for exactly as long as you accelerated. That's actually probably the ideal way of travelling space: accelerate half the way, then turn around and decelerate the rest. That way you get gravity for the entire trip.
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Thank you and understood.
Always important to consider that even the new Artemis Rocket relies on rocket motors very similar to those of Saturn 5 which are essentially based on those of WW2 technology. We have not progressed the power source much in over 70 years apart from bigger versions.
In order for humanity to be capable of proper space exploration, we must first find a step change in propulsion.
 
Buster15 said:
Thank you and understood.
Always important to consider that even the new Artemis Rocket relies on rocket motors very similar to those of Saturn 5 which are essentially based on those of WW2 technology. We have not progressed the power source much in over 70 years apart from bigger versions.
In order for humanity to be capable of proper space exploration, we must first find a step change in propulsion.
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Solar sails, small unmanned craft that could reach 10% sol. That's the next step.
 
Buster15 said:
Thank you and understood.
Always important to consider that even the new Artemis Rocket relies on rocket motors very similar to those of Saturn 5 which are essentially based on those of WW2 technology. We have not progressed the power source much in over 70 years apart from bigger versions.
In order for humanity to be capable of proper space exploration, we must first find a step change in propulsion.
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I'd say the problem is sociological. We have the scientific know-how, but not the political or social will. Fission rocket systems will outperform chemical rockets by orders of magnitude. But no one wants to fly nuclear material in space. Thankfully NASA is now taking NTP proposals seriously after almost 70 years.

The next step would be fusion-based systems, though that poses some hurdles.
 
marcus agrippa said:
I'd say the problem is sociological. We have the scientific know-how, but not the political or social will. Fission rocket systems will outperform chemical rockets by orders of magnitude. But no one wants to fly nuclear material in space. Thankfully NASA is now taking NTP proposals seriously after almost 70 years.

The next step would be fusion-based systems, though that poses some hurdles.
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Thank you and an interesting post.
I may well be wrong but I was of the opinion that a number of the satellites sent into deep space used nuclear power because they would be too far away from the sun for solar power.
But I will check on that.

But that is different from using nuclear power as the launch power.
 
Buster15 said:
Thank you and an interesting post.
I may well be wrong but I was of the opinion that a number of the satellites sent into deep space used nuclear power because they would be too far away from the sun for solar power.
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Those aren't using nuclear reactors, but isotope batteries. They are just using the warmth of the natural decay, which is an extremely simple design without any moving parts etc. The power output of these is small and can't be used for propulsion, but to power the satellites themselves. This applies to all deep space missions (going further than Jupiter, and even most Jupiter missions)
 
stefan92 said:
Those aren't using nuclear reactors, but isotope batteries. They are just using the warmth of the natural decay, which is an extremely simple design without any moving parts etc. The power output of these is small and can't be used for propulsion, but to power the satellites themselves. This applies to all deep space missions (going further than Jupiter, and even most Jupiter missions)
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Thank you for this.
I was just about to post this but you beat me to it.
Totally correct. They do use Fissile material as you say and the Weak Force results in the decay of the radiation resulting in some heat energy to power the satellite systems.
The amount of Fissile material is very small. And the Voyager satellites have used up their tiny power source, as far as I understand.

But as you say, this is totally separate from any launch power source and for the medium term, we are talking conventional liquid fuelled rockets.
 
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