Astronomy & Space Exploration

carvajal said:
Like the rest, I also think these last few pages have been great.
I've been listening an astronomy podcast for a while and curiously these last months they are especially interested in matter and dark energy.
In any case, I have a question.
I have heard in this podcast, on YouTube and here on Red Café: @Invictus , in another thread "or all we know, this universe could be a lab experiment in a wider cosmos which is why we have such elegant physical laws".
what exactly means the term elegant?. To the precision of the laws? How do they fit together? or rather refers to how they are fair to promote life?
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I don't know what Invictus meant or the context, so just a few general remarks. I'll use terms like elegance or beauty interchangeable unless stated.

Theories in math or physics can be elegant just like fashion can be. Its ultimately hard to define, but depends on simplicity (making few assumptions), rigidity (theory is difficult to change), surprising consequences and in (high-energy) physics additionally naturalness (~no fine tuning of certain parameters necessary).

A theory that manages to unify forces would be almost always be considered elegant. Theories, that use supersymetry (SUSY) are extremely popular for the same reasons. General relativity is usually seen as a beautiful theory even so its not really natural. The standard model of particle physics is usually on the opposite end of the spectrum: not elegant/beautiful.

Naturalness means roughly how much one need to specify/"fine-tune" initial conditions and/or parameters to explain macro-states. Its a statistical assumption about probability distributions of phase spaces and/or parameter spaces. Its particularly important because at least some physicists, who research on fundamental physics, are adhering to it. In this context two parameters (mass of the Higgs and the cosmological constant) are very unnatural. Quantum Field Theories (QFTs) strongly suggest(ed) that the LHC should have found *something* new at the probed energy scales, if naturalness applies.

One of many reasons (and certainly a less important one) why string theory is popular is, because it at least could turn out to be beautiful in the sense, that it gets rid of/explains unnatural parameters. It also opens up the possibility of a very large cosmological multiverse, but thats a different topic.

In this sense, the best established theories are not as elegant as physicists would like them to be. It could be, that all of this get resolved once we understand physics better at higher energy and smaller scales. Most popular theories, that try to do that are certainly more beautiful. Yet at the same time that might not be the case. Its at least possible, that theories get refined and better measurements "just" find natural constants, that are inexplicable and fairly random in value.

to steal a quote from Feynman from wiki

There is a most profound and beautiful question associated with the observed coupling constant, e – the amplitude for a real electron to emit or absorb a real photon. It is a simple number that has been experimentally determined to be close to 0.08542455. (My physicist friends won't recognize this number, because they like to remember it as the inverse of its square: about 137.03597 with about an uncertainty of about 2 in the last decimal place. It has been a mystery ever since it was discovered more than fifty years ago, and all good theoretical physicists put this number up on their wall and worry about it.) Immediately you would like to know where this number for a coupling comes from: is it related to pi or perhaps to the base of natural logarithms? Nobody knows. It's one of the greatest damn mysteries of physics: a magic number that comes to us with no understanding by man. You might say the "hand of God" wrote that number, and "we don't know how He pushed his pencil." We know what kind of a dance to do experimentally to measure this number very accurately, but we don't know what kind of dance to do on the computer to make this number come out, without putting it in secretly!
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PedroMendez said:
I don't know what Invictus meant or the context, so just a few general remarks. I'll use terms like elegance or beauty interchangeable unless stated.

Theories in math or physics can be elegant just like fashion can be. Its ultimately hard to define, but depends on simplicity (making few assumptions), rigidity (theory is difficult to change), surprising consequences and in (high-energy) physics additionally naturalness (~no fine tuning of certain parameters necessary).

A theory that manages to unify forces would be almost always be considered elegant. Theories, that use supersymetry (SUSY) are extremely popular for the same reasons. General relativity is usually seen as a beautiful theory even so its not really natural. The standard model of particle physics is usually on the opposite end of the spectrum: not elegant/beautiful.

Naturalness means roughly how much one need to specify/"fine-tune" initial conditions and/or parameters to explain macro-states. Its a statistical assumption about probability distributions of phase spaces and/or parameter spaces. Its particularly important because at least some physicists, who research on fundamental physics, are adhering to it. In this context two parameters (mass of the Higgs and the cosmological constant) are very unnatural. Quantum Field Theories (QFTs) strongly suggest(ed) that the LHC should have found *something* new at the probed energy scales, if naturalness applies.

One of many reasons (and certainly a less important one) why string theory is popular is, because it at least could turn out to be beautiful in the sense, that it gets rid of/explains unnatural parameters. It also opens up the possibility of a very large cosmological multiverse, but thats a different topic.

In this sense, the best established theories are not as elegant as physicists would like them to be. It could be, that all of this get resolved once we understand physics better at higher energy and smaller scales. Most popular theories, that try to do that are certainly more beautiful. Yet at the same time that might not be the case. Its at least possible, that theories get refined and better measurements "just" find natural constants, that are inexplicable and fairly random in value.

to steal a quote from Feynman from wiki
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Thank you very much for your explanation Pedro. I think I will keep your post, like a few others in bookmarks, to be able to read calmly about everything you say.
Buster15 said:
I will leave it to those far more knowledgeable than me.

But as I have read a lot about the events during the very very first fractions of a second after what we term the big bang, it has always fascinated me how different our universe could have become.

The list is long. But would include:
Cosmic Inflation
Matter v Antimatter
How the Unified Force split.
The relative strength of the four forces.

I am sure there are many more.
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Thank you too
 
Matter vs anti-matter is very-fascinating and intriguing to me. Not the concept of anti-matter itself, that is easy and intuitive to grasp (and the math is simple). What is intruiging to me, is why the matter exists in the first place, where, from all accounts, matter and anti-matter should have been created in equal amounts, and soon afterwards, annihilate each other. However, it seems that for every 1 billion antimatter particles, there were 1 billion and 1 matter particles, with the 1s surviving, and essentially being the entire universe (or well, the matter in the universe, let's forget about DM and DE for a moment) that exists right there.

Seems a lot like a rounding error in the program :)
 
Raoul said:
Proxima-B observationally confirmed

Closest planet to earth.

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It is not peer-reviewed yet, so not officially confirmed. However looks quite good and it is huge news. I think it was expected that there are gonna be planets in Proxima centaury system, but it is different expecting them and finding them.

I wonder how long is gonna take humanity to reach that planet. Within a thousand of years?!
 
Not long ago, tonight I was sat in my new hot tub looking at the crescent moon. With a beer and just imagining travelling through the stars, I saw a star and thought, hang on that's moving. I quickly realised it was a satellite I'm almost certain the ISS travelling right over my head. A really special moment for me.
 
Revan said:
It is not peer-reviewed yet, so not officially confirmed. However looks quite good and it is huge news. I think it was expected that there are gonna be planets in Proxima centaury system, but it is different expecting them and finding them.

I wonder how long is gonna take humanity to reach that planet. Within a thousand of years?!
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Well being about 4.3 light years away at current top speeds say 70,000 years.
 
Raoul said:
Not particularly encouraging given that we've already forgotten how to get to the moon.
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Space exploration needs to be profitable IMO, for humanity to really start properly doing it. Though, the last few years have been encouraging, and hopefully on 10-15 years, some human will walk on March.
 
Revan said:
Sure, but the technology is gonna improve. A nice article starting from current technologies, to theoretical technologies to close to science fiction: https://www.universetoday.com/15403/how-long-would-it-take-to-travel-to-the-nearest-star/

I don't think that a travel which would last hundreds of years (let alone thousands) is gonna be feasible.
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We need Hyper-sleep technology, and some AI pilot to keep the ship from crashing.

If the ship can self sustain on such a trip, how many years it take wouldn't matter, because for someone in hyper sleep, it would feel like a one night sleep.

So please tell me we are not that far away from hyper sleep being a real thing.
 
George Owen said:
We need Hyper-sleep technology, and some AI pilot to keep the ship from crashing.

If the ship can self sustain on such a trip, how many years it take wouldn't matter, because for someone in hyper sleep, it would feel like a one night sleep.

So please tell me we are not that far away from hyper sleep being a real thing.
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I think it would be necessary, but I am not sure people would particularly fancy it. Reaching a planet in the middle of nowhere after 70k years is something that most people would probably not want to do. I assume that it might be a one-way ticket in any case but just looks scarier going 70k years in the future or so.

Actually, I am not sure why someone is gonna take that trip. We really need relativistic speeds for these travels to become desirable.
 
Imagine waking up from that and knowing thousands of years had passed on Earth and all your family are long gone by now. It's definitely a one-way mission, dare I say a suicide mission in some ways.

I'd go, maybe. Probably not.
 
Revan said:
I think it would be necessary, but I am not sure people would particularly fancy it. Reaching a planet in the middle of nowhere after 70k years is something that most people would probably not want to do. I assume that it might be a one-way ticket in any case but just looks scarier going 70k years in the future or so.

Actually, I am not sure why someone is gonna take that trip. We really need relativistic speeds for these travels to become desirable.
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Many people jump on inflatable boats to try cross an ocean. Don't worry. We gonna have plenty volunteers.

For many humans, dying a silent death in Space, would be a better way to go than dying from starvation.
 
MrMarcello said:
Imagine waking up from that and knowing thousands of years had passed on Earth and all your family are long gone by now. It's definitely a one-way mission, dare I say a suicide mission in some ways.

I'd go, maybe. Probably not.
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No way. I love science-fiction and all that shit, but I don't think I would take that trip even if it would take just 10 years to come and go (travel at 99% of c, and 1 year of exploration).

Coming back, everyone would be 9 years older, likely many people I know would have passed away, etc.
 
Revan said:
Sure, but the technology is gonna improve. A nice article starting from current technologies, to theoretical technologies to close to science fiction: https://www.universetoday.com/15403/how-long-would-it-take-to-travel-to-the-nearest-star/

I don't think that a travel which would last hundreds of years (let alone thousands) is gonna be feasible.
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I think solar sail technology would be the nearest we could reach centauri perhaps in our lifetime. But not manned. Space is too big the only way we can explore is through telescopes.
 
George Owen said:
Many people jump on inflatable boats to try cross an ocean. Don't worry. We gonna have plenty volunteers.

For many humans, dying a silent death in Space, would be a better way to go than dying from starvation.
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Ok true but their discoveries would be their own.
 
George Owen said:
We need Hyper-sleep technology, and some AI pilot to keep the ship from crashing.

If the ship can self sustain on such a trip, how many years it take wouldn't matter, because for someone in hyper sleep, it would feel like a one night sleep.

So please tell me we are not that far away from hyper sleep being a real thing.
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This reminds me of a next generation episode where they discover a drifting craft with chronically frozen people on it from the late 21st century. They thaw them and they are confused and lost in the future they find themselves in.
 
Revan said:
I think it would be necessary, but I am not sure people would particularly fancy it. Reaching a planet in the middle of nowhere after 70k years is something that most people would probably not want to do. I assume that it might be a one-way ticket in any case but just looks scarier going 70k years in the future or so.

Actually, I am not sure why someone is gonna take that trip. We really need relativistic speeds for these travels to become desirable.
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George Owen said:
They could communicate back to earth though. Any message would take a few years to arrive, but it's doable.
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True with proximate centauri but further out it's still going to be very hard. It's a rocky planet a few times bigger than earth.
Even with relativistic speeds it would take 100,000 years to traverse the galaxy.
 
George Owen said:
:lol:

Did they joined the crew or went back to sleep?
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They didnt join the crew. I cant remember but they sent them on somewhere. One guy was an oil millionaire and he was confused that there was no money or capitalism in the star trek future. I recommend that one.
 
giggs-beckham said:
They didnt join the crew. I cant remember but they sent them on somewhere. One guy was an oil millionaire and he was confused that there was no money or capitalism in the star trek future. I recommend that one.
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Imagine how depressed Trump would be. "So no wealth accumulation? No cocaine? Any teen Russian girls around?"
 
giggs-beckham said:
True with proximate centauri but further out it's still going to be very hard. It's a rocky planet a few times bigger than earth.
Even with relativistic speeds it would take 100,000 years to traverse the galaxy.
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Yeah, if we don't discover super-relativistic traveling (which is still totally unclear if it is theoretically possible or not), it is gonna be boring colonizing the galaxy. It might still be possible (after all you just need to colonize the next solar sytem and after a few million years the entire galaxy might be colonized), but it is just gonna be boring and not sure if people might be interested (though then, humanity colonized Polynesia tens of thousands of years ago) to do it.
 
I bet the cabins on the spaceships wouldn’t even windows. I’d rather focus on building a giant Halo ring to live on in orbit here.
 
giggs-beckham said:
True with proximate centauri but further out it's still going to be very hard. It's a rocky planet a few times bigger than earth.
Even with relativistic speeds it would take 100,000 years to traverse the galaxy.
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True, although from the perspective of the travellers it would be less. At 99% the speed of light you could cross the galaxy (120 000 light years) in "only" ~17 000 years, though in reality you'd want to accelerate until the half-way point, then turn around and accelerate in the other direction, which would make the trip longer (both because you have to slow down, and because you have to accelerate to said relativistic speed in the first place).

If you could get to 99.999999999% the speed of light, you could do it in half a year.
 
nimic said:
True, although from the perspective of the travellers it would be less. At 99% the speed of light you could cross the galaxy (120 000 light years) in "only" ~17 000 years, though in reality you'd want to accelerate until the half-way point, then turn around and accelerate in the other direction, which would make the trip longer (both because you have to slow down, and because you have to accelerate to said relativistic speed in the first place).

If you could get to 99.999999999% the speed of light, you could do it in half a year.
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One of the biggest if's ever.
Only massless particles can do that, which of course you know.
 
Buster15 said:
One of the biggest if's ever.
Only massless particles can do that, which of course you know.
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Only massless particles can travel at the speed of light, but there's no reason (except that it's really really really really really really really hard) why a space ship couldn't travel at 99% the speed of light. And the closer you get to 100% (which you will never reach, no matter how much energy you put into it), the more significant time dilation/length contraction is. You "only" need to get to ~75% of the speed of light to slow time down by ~33%, for example. If you get to 99.99999999999999% the speed of light (which is the furthest the calculator I am using will go), you could get to Andromeda in four hours (if I did it correctly). Or rather, you would have experienced four hours, while someone on Earth would have experienced two and a half million years.
 
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nimic said:
Only massless particles can travel at the speed of light, but there's no reason (except that it's really really really really really really really hard) why a space ship couldn't travel at 99% the speed of light. And the closer you get to 100% (which you will never reach, no matter how much energy you put into it), the more significant time dilation/length contraction is. You "only" need to get to ~75% of the speed of light to slow time down by ~33%, for example. If you get to 99.99999999999999% the speed of light (which is the furthest the calculator I am using will go), you could get to Andromeda in four hours (if I did it correctly). Or rather, you would have experienced four hours, while someone on Earth would have experienced two and a half million years.
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Indeed.
I wasn't trying to be clever. More that the fastest we have travelled is about 25,000 mph.
And that is using rocket technology based on WW2. And the latest NASA manned space mission uses that same rocket type.

Ok. I accept that we don't know what we don't know. And anything is potentially possible.

But even 1% PSOL is many many orders of magnitude beyond what is considered likely even for nano spacecraft.
But.... Who knows eh.
 
The hard part about going fast is a) the amount of energy needed and b) not exploding/imploding when you hit some dust. If we sort out fusion at some point, and think of some way to protect a ship, we could definitely accelerate a ship up to a decent percentage of the speed of light just by accelerating for long enough.
 
nimic said:
The hard part about going fast is a) the amount of energy needed and b) not exploding/imploding when you hit some dust. If we sort out fusion at some point, and think of some way to protect a ship, we could definitely accelerate a ship up to a decent percentage of the speed of light just by accelerating for long enough.
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Agree with the acceleration part.
I have read a fair bit about nuclear fusion and it is obviously a potential solution to the world energy requirements.

However, making it work by producing net energy output and making it small and light enough to power a spacecraft could be quite some way off.
But. Never say never.
 
nimic said:
True, although from the perspective of the travellers it would be less. At 99% the speed of light you could cross the galaxy (120 000 light years) in "only" ~17 000 years, though in reality you'd want to accelerate until the half-way point, then turn around and accelerate in the other direction, which would make the trip longer (both because you have to slow down, and because you have to accelerate to said relativistic speed in the first place).

If you could get to 99.999999999% the speed of light, you could do it in half a year.
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If you could travel at c then you'd get there instantly I think?? Some kind of static warp bubble maybe. But as I said previously your discoveries would be you're own as every one else would be long dead.
So an arc like craft of civilisation traversing the universe at c, I'm imagining a rotating craft to simulate gravity.
 
George Owen said:
Many people jump on inflatable boats to try cross an ocean. Don't worry. We gonna have plenty volunteers.

For many humans, dying a silent death in Space, would be a better way to go than dying from starvation.
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If I would not have a girlfriend with plans for the future, I would sign in with not much hesitation (would depend on the specifics on % of survivability)
 
4bars said:
If I would not have a girlfriend with plans for the future, I would sign in with not much hesitation (would depend on the specifics on % of survivability)
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Yea I've got two boys and a girlfriend. Without that would I go? Definitely.
 
giggs-beckham said:
This reminds me of a next generation episode where they discover a drifting craft with chronically frozen people on it from the late 21st century. They thaw them and they are confused and lost in the future they find themselves in.
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And they wake up like zombies - whole plot around what they saw, or dreamed, 8,000 years ago. Epic psychology sessions required :)
 
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