Science General Discussion

[the-pi-guy]

Wow I can't believe I didn't realize this earlier.

As a kid I learned of the big bang as an explosion like a supernova. Pretty sure every layman thinks of it like that, yet I kept this understanding even after learning about cosmic background radiation, higher dimensions, expansion, etc. Wasn't till an hour ago that something caused me to think about it and realise what we learn as kids is wrong.

I feel like I'm learning lots of things.  
Definitely about the bolded.  Just search big bang explosion.  Lots of people asking about the big bang explosion, or articles writing about it and then someone or the article "it wasn't actually an explosion."

The universe was always infinite in size and practically infinite in energy at every single area. The big bang was more like a big stretch, where the infinite universe expanded and decreased density. No explosion

I'm not quite so sure about the bolded, but the rest of it is quite correct.

Now for my personal line of probably incredibly flawed thought, I wonder if the universe has cycles like stars. The initial state of the big bang sounds a heck of a lot like the eventual heat death of the universe, just with a different density value. It seems reasonable that before the big bang a super high energy low entropy state could have existed that slowly evened out, and a super low energy high entropy state could form after the heat death, with new physics emerging at every transition. All our forces were originally combined during the first moments. IDK, it's always fun thinking about this stuff before bed.

This is something that I've heard at least considered.  A TV show actually made some idea similar to this.  And I've heard about similar ideas in other places too.

Well in Futurama what happened is that after the universe dies, there is another big bang. One of the guys who worked on Futurama actually has a Physics degree from Harvard.  So while the show certainly takes unrealistic liberties, someone there actually has some experience to draw from.  

There are these ideas about the end of the universe like Big Crunch, Big Rip that might be interesting to you, if you haven't heard of them.  

I'm sure Xev will be able to tell us lot's of stuff once he's done.  

[Legend]

I'm not quite so sure about the bolded, but the rest of it is quite correct.

The universe might loop, but you can travel in every direction an infinite distance (excluding black holes). That's all I meant.
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This is something that I've heard at least considered.  A TV show actually made some idea similar to this.  And I've heard about similar ideas in other places too.

Well in Futurama what happened is that after the universe dies, there is another big bang. One of the guys who worked on Futurama actually has a Physics degree from Harvard.  So while the show certainly takes unrealistic liberties, someone there actually has some experience to draw from.  

There are these ideas about the end of the universe like Big Crunch, Big Rip that might be interesting to you, if you haven't heard of them.  

I'm sure Xev will be able to tell us lot's of stuff once he's done.  

I've read up on the Big Crunch and Big Rip, I just never made the connection that my childhood understanding of it starting with an explosion was wrong.

[Legend]

Didn't realise it had two failed attempts.

[Legend]

I have low standards for humor...

[Legend]

Oldest stars ever found discovered near the centre of Milky Way - Science - ABC News (Australian Broadcasting Corporation)

13.6 billion years old.

[DD_Bwest]

Didn't realise it had two failed attempts.

looks like me playing kerbals lol

[Legend]

It's very interesting that things can be mathematically modeled at all. Figuring out spring tension uses such a simple equation for example, even though on the micro level it's incredibly complex. Or traffic patterns. All the intricacies of human complexity fade away and a general math equation still works.

[the-pi-guy]

Math is incredible.  Unlike any other subject in my opinion.  
It evolved, and originally negative numbers didn't exist.  And over time stuff filled in.  
What's really cool are complex numbers. How they work seems so different from the normal number system, yet it came out of it.  Suddenly not only do negative numbers have square roots, but this opens up algebra with trigonometry.  
e^(ix) is a rotation in the complex plane.  So cool how the square root of negative one has so many trigonometric and algebraic uses.  

[the-pi-guy]

Suppose we have the vector {x,y} = x+iy   and we have {cos(z),sin(z)} = cos(z) + i*sin(z)
(x+iy)(cos(z)+isin(z)= xcos(z) + xisin(z) + iycos(z) -ysin(z) = {xcos(z) - ysin(z), xsin(z)+ycos(z)}

How crazy is that!?  
If it's not clear yet, I'll write it in a more common way.  

Code Select Expand

[x'] = [cos(z)  -sin(z)][x]
[y']   [sin(z)   cos(z)][y]
The rotation matrix works the same way as i does!  

[the-pi-guy]

[the-pi-guy]

Is it true that we have lost the technology to visit moon?

Why does it take 3 years to develop a new car, when it shares 90% of its "DNA" with the previous model?  Why does it take 6 years to develop a new airplane when it shares 90% of its "DNA" with the previous model?

The answer is that they are complex devices.  A launch vehicle and spacecraft destined to go to the moon is much more complex and operates at the edge of the envelope where there is little tolerance for imprecision and error.

When operating on the edge of the envelope, thousands and thousands of hours go into testing and tweaking.  The development and operations teams acquire expertise that no one else on the planet has.  The vehicle cannot be built or operated without that expertise.

Operating a space mission involves reams of paper in the forms of flight rules and operational procedures.  Those rules and procedures are drafted over thousands of hours of test and simulations.  A change in the vehicle can send ripples of changes through those documents.

The Saturn V rocket had over 3 million parts.  The command and service modules and lunar module were composed of millions of additional parts.  An individual person cannot contemplate the scale of detail needed to assemble and operate those vehicles.

So, when the Apollo program ended, the factories that assembled those vehicles were retasked or shut down.  The jigs were disassembled.  The molds were destroyed.  The technicians, engineers, scientists, and flight controllers moved onto other jobs.  Over time, some of the materials used became obsolete.

If we, today, said - "Let us build another Saturn V rocket and Apollo CSM/LEM and go to the moon!"  it would not be a simple task of pulling out the blueprints and bending and cutting metal.

We don't have the factories or tools.  We don't have the materials.  We don't have the expertise to understand how the real vehicle differed from the drawings.  We don't have the expertise to operate the vehicle.

We would have to substitute modern materials.  That changes the vehicle.  It changes the mass, it changes the stresses and strains, it changes the interactions.  It changes the possible malfunctions.  It changes the capabilities of the vehicle.

We would have to spend a few years re-developing the expertise.  We would have to conduct new tests and simulations.  We would have to draft new flight rules and procedures.  We would have to certify new flight controllers and crew.

We would essentially be building a new vehicle.

And that's what we are doing.  As similar as Orion looks to an Apollo Command Module, as much as we think we understand heat shields and parachute deploy systems - we have to understand these specific heat shields and parachute deploy systems.  NASA has people doing these tests, every day.

Ars Technica did an excellent story on the work NASA needed to do to reconstruct the F-1 engine from the Saturn V for use on the SLS.  How NASA brought the monstrous F-1 Moon Rocket Engine back to life

How did we lose the technology to go to the Moon? - Quora

[Raven]

Is it true that we have lost the technology to visit moon?

Lost the technology? Nah. More like someone who only drove a car once in their life decades ago and is now in a newer car and trying to relearn how to drive I'd say.

[Legend]

Yeah trying to "resurrect" the original launch plans/techniques would take so much freaking work.

[the-pi-guy]

[the-pi-guy]

You've got the wrong sky! How James Cameron altered night sky in reworked Titanic 3D after ten years of complaints from outspoken astronomer | Daily Mail Online

Did not know about that, kinda funny.