Science General Discussion

Started by Legend, Sep 02, 2014, 07:17 PM

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Legend


the-pi-guy


the-pi-guy

Someone on Reddit asked why astrology was ridiculous.  Why's it ridiculous that the gravity from a star could have an impact on development?


The gravity being tiny is the obvious answer.  

The force of gravity between Earth and the closest star was bigger than I expected, but even still.  It comes out to a tiny acceleration.  Like less than a quadrillionth of the acceleration the Earth gives objects on the surface.  

Basically even  if astrology wasn't bunk, it'd still be stupidly useless that it'd basically be bunk again.  

If the gravity from even the closest stars had an effect on development, so would the gravity of some large ships and buildings.  

Haven't done any calculations, but I'd guess that the effect of most stars in astrology would be even less than the effect of small buildings.  

Xevross

Someone on Reddit asked why astrology was ridiculous.  Why's it ridiculous that the gravity from a star could have an impact on development?


The gravity being tiny is the obvious answer.  

The force of gravity between Earth and the closest star was bigger than I expected, but even still.  It comes out to a tiny acceleration.  Like less than a quadrillionth of the acceleration the Earth gives objects on the surface.  

Basically even  if astrology wasn't bunk, it'd still be stupidly useless that it'd basically be bunk again.  

If the gravity from even the closest stars had an effect on development, so would the gravity of some large ships and buildings.  

Haven't done any calculations, but I'd guess that the effect of most stars in astrology would be even less than the effect of small buildings.  
Wait is the supposed 'science' of astrology claimed to be about gravity of the stars? How does that make any sense? I thought it was just spiritual shame.

the-pi-guy

Wait is the supposed 'science' of astrology claimed to be about gravity of the stars?
It's the psuedoscience I've heard of it in the past. The redditor made a similar "why couldn't gravity do such and such".  

Quote
How does that make any sense?
I mean it doesn't make any sense so...

But I always assume they'd say something like gravity in different directions would affect how the brain develops.  

But that'd be just as nonsensical. Maybe even more.  

Quote
I thought it was just spiritual shame.
I'm not sure how common the spiritual vs gravity explanations are.  

Legend

Someone on Reddit asked why astrology was ridiculous.  Why's it ridiculous that the gravity from a star could have an impact on development?


The gravity being tiny is the obvious answer.  

The force of gravity between Earth and the closest star was bigger than I expected, but even still.  It comes out to a tiny acceleration.  Like less than a quadrillionth of the acceleration the Earth gives objects on the surface.  

Basically even  if astrology wasn't bunk, it'd still be stupidly useless that it'd basically be bunk again.  

If the gravity from even the closest stars had an effect on development, so would the gravity of some large ships and buildings.  

Haven't done any calculations, but I'd guess that the effect of most stars in astrology would be even less than the effect of small buildings.  
Gravity is super weak compared to other forces but stars and space objects can be just so massive.

I never knew that astrology had a belief that gravity from stars caused it, but another flaw with that view is that the gravity on Earth would not change in a yearly cycle. Earth's orbit is so small that the relative velocities of those stars and our sun would make the year over year pull more varied than the month over month pull.

Legend

the Comet on Vimeo

I always like videos like this

the-pi-guy

Something that most people don't get is when people are doing research on obvious questions.  

Like questions that everyone thinks they know the answer to, just based off common sense or experiences.

One challenge is that common sense is often super wrong.  The obvious, seemingly clearly correct view can actually be wrong.  


Also just had a weird bug.  Was deleting some new lines and it was deleting characters from a word.  Added a new space and all the characters came back.

Legend

Something that most people don't get is when people are doing research on obvious questions.  

Like questions that everyone thinks they know the answer to, just based off common sense or experiences.

One challenge is that common sense is often super wrong.  The obvious, seemingly clearly correct view can actually be wrong.  


Also just had a weird bug.  Was deleting some new lines and it was deleting characters from a word.  Added a new space and all the characters came back.
The worst is that no one wants to fund those uninteresting studies/experiments, especially ones that just set out to replicate old studies. Science only works if everything is checked.

Weird.

Legend


the-pi-guy


Legend

https://www.quora.com/How-would-a-realistic-very-large-spaceship-look-like/answer/Dave-Consiglio
Quora tends to have weird answers. That wouldn't work at all.

It takes a lot of energy to launch stuff into space, the person is right that in situ resource utilization is important, but no one argues the resources should be used as is lol. Mine, refine, and manufacture all in space.

A hollowed out asteroid would make a horrible ship. Way too heavy to move and way too fragile. A purpose built ship with heat shields would handle aerobraking so so so much better. The massive asteroid would have no way to control itself in the air and would need to plunge into the thicker lower atmosphere to really slow down. It'd be nearly impossible to end up in a desired orbit. Every real world spaceship needs to fly like a "plane" to control where they go. This video from the sixties shows how it worked with Apollo:



Interestingly enough, SpaceX's BFR was actually designed to enter the Martian atmosphere upside down.

This would allow the rocket to stay in the upper atmosphere longer and bleed off more speed before entering the thick lower atmosphere. Without having this control, the rocket would have too much velocity and would "bounce" off.


the-pi-guy

Sep 17, 2019, 03:41 AM Last Edit: Sep 17, 2019, 03:48 AM by the-pi-guy
Quora tends to have weird answers. That wouldn't work at all.
Quora has a mix of answers from terrible to great.

Quote
It takes a lot of energy to launch stuff into space, the person is right that in situ resource utilization is important, but no one argues the resources should be used as is lol. Mine, refine, and manufacture all in space.

A hollowed out asteroid would make a horrible ship. Way too heavy to move and way too fragile. A purpose built ship with heat shields would handle aerobraking so so so much better. The massive asteroid would have no way to control itself in the air and would need to plunge into the thicker lower atmosphere to really slow down. It'd be nearly impossible to end up in a desired orbit. Every real world spaceship needs to fly like a "plane" to control where they go. This video from the sixties shows how it worked with Apollo:


Interestingly enough, SpaceX's BFR was actually designed to enter the Martian atmosphere upside down.
This would allow the rocket to stay in the upper atmosphere longer and bleed off more speed before entering the thick lower atmosphere. Without having this control, the rocket would have too much velocity and would "bounce" off.


But what if a space ship didn't have to go through an atmosphere?

Spoiler for Hidden:
<br>I don&#39;t think it&#39;d work for other reasons.&nbsp; <br>Wouldn&#39;t be very practical to move for one thing.<br>

Legend

Quora has a mix of answers from terrible to great.
But what if a space ship didn't have to go through an atmosphere?

Spoiler for Hidden:

I don't think it'd work for other reasons.  
Wouldn't be very practical to move for one thing.

Learning about spaceships and atmospheres has been a funny experience for me. First you think all the wings on spaceships in movies are cool cause sci fi, then you think all the wings are dumb cause physics, but then you think they're cool again cause rocket equation. In a super far future universe where rocket fuel works like car fuel alla epstein drive, dumb blocky spaceships make sense. They also make sense for generation ships or crafts with weak but highly efficient engines. For example a ship like this is freaking awesome.

A high powered laser is shot from Earth to propel the ship for the initial journey, making it circumvent the rocket equation. It would make no sense for it to ever enter an atmosphere.

A smaller ship for just our own solar system however all but needs aerobraking.



This delta v map (not sure if you've played kerbal space program) shows how much change in velocity is needed to move about the Earth, Moon, and mars. Without aerobraking, it'd take 19.5 km/s of delta v while with aerobraking it only takes 13.1 km/s of delta v. Because the fuel needed to accelerate that extra 6.4 km/s has mass, it takes even more fuel just to bring that extra fuel.

Say we have a rocket that weighs 100 tons when empty that has 100 tons of cargo and engines with a 350 ISP (this is kinda similar to SpaceX's Starship). To have 13.1 km/s of delta v, it needs 8,900 tons of fuel. However to have 19.5 km/s of delta v, it needs a whopping 58,500 tons of fuel. It's goes from insane but maybe possible in the future to ludicrous. Aerobraking can save so much fuel that I can't imagine any rocket with strong enough engines would ignore it. NASA's Mars transfer vehicle can't aerobrake for example because it would get stuck in the planet's gravity well.


Spoiler for Hidden:
<br>I think I like rockets too much.<br><br><div style="margin:20px; margin-top:5px"><div class="smallfont" style="margin-bottom:2px"><b>Spoiler</b> for <i>Hidden</i>: <input type="button" value="Show" style="width:60px;font-size:10px;margin:0px;padding:0px;" onClick="if (this.parentNode.parentNode.getElementsByTagName('div')[1].getElementsByTagName('div')[0].style.display != '') { this.parentNode.parentNode.getElementsByTagName('div')[1].getElementsByTagName('div')[0].style.display = ''; this.value = 'Hide'; } else { this.parentNode.parentNode.getElementsByTagName('div')[1].getElementsByTagName('div')[0].style.display = 'none'; this.value = 'Show'; }"></div><div class="alt2" style="margin: 0px; padding: 6px; border: 1px inset;"><div style="display: none;"><br>Nuclear rocket engines are about as good as we could hope for in any foreseeable future. With an ISP of 1,000, our theoretical single stage rocket would need only 600 tons of fuel with aerobraking to land on Mars. Without it would need 1,300 tons of fuel. Much nicer but still shows how aerobraking is still very important for near term sci fi ships.<br><br>Of course a light weight antimatter drive could do it with just .027 tons of fuel or .04 tons without aerobraking, but if you have a ship with those capabilities then all our notions about space travel are out the winder.<br><br><div style="margin:20px; margin-top:5px"><div class="smallfont" style="margin-bottom:2px"><b>Spoiler</b> for <i>Hidden</i>: <input type="button" value="Show" style="width:60px;font-size:10px;margin:0px;padding:0px;" onClick="if (this.parentNode.parentNode.getElementsByTagName('div')[1].getElementsByTagName('div')[0].style.display != '') { this.parentNode.parentNode.getElementsByTagName('div')[1].getElementsByTagName('div')[0].style.display = ''; this.value = 'Hide'; } else { this.parentNode.parentNode.getElementsByTagName('div')[1].getElementsByTagName('div')[0].style.display = 'none'; this.value = 'Show'; }"></div><div class="alt2" style="margin: 0px; padding: 6px; border: 1px inset;"><div style="display: none;"><br>All this is metric tons.<br></div></div></div><br></div></div></div><br>

delmiss

Sure things can. It's just that only light can travel at the speed of light in this universe.

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