29 replies to this topic

[SammyBirdland]

http://www.theguardi...impact-recorded

 

The 400kg (63st) meteorite, travelling at 61,000 km/h (40,000 mph), punched a fresh crater on the moon's surface some 40 metres wide in what is thought to be the largest lunar impact ever recorded.

 

The rock, which was about a metre in diameter, ploughed into an ancient lava-filled basin called the Mare Nubium, producing a flash almost as intense as the Pole Star that took more than eight seconds to fade.

 

Unlike Earth, the moon has no atmosphere to protect it from incoming meteorites, so the surface is pocked with craters. The rock would have swiftly burned up in the Earth's atmosphere long before it reached the ground.

 

 

 

[NewMarketSean]

How did it create a flash if there's no atmosphere on the moon and there are no explosions in space?

[SammyBirdland]

How did it create a flash if there's no atmosphere on the moon and there are no explosions in space?

 

 

http://science.nasa....ay_lunarimpact/

 

The Moon has no oxygen atmosphere, so how can something explode? Lunar meteors don't require oxygen or combustion to make themselves visible.  They hit the ground with so much kinetic energy that even a pebble can make a crater several feet wide.  The flash of light comes not from combustion but rather from the thermal glow of molten rock and hot vapors at the impact site.

[Pedro Cerrano]

How did it create a flash if there's no atmosphere on the moon and there are no explosions in space?

 

Good question.  The answer may surprise you.

 

Lunar meteors actually don't require oxygen or combustion to make themselves visible.  In fact, they hit the ground with so much kinetic energy that even a pebble can make a crater.  This crater can be up to several feet wide. The flash of light comes from the thermal glow of molten rock and hot vapors at the impact site.  I'm assuming you thought it came from combustion, a common mistake indeed.

[Mackus]

Awesome.  Space kicks ass.

[Pedro Cerrano]

Sometimes when I get drunk I like to talk about space.

 

My biggest questions:

 

1) If space is expanding what is it expanding INTO?

 

2)  How has space (or matter, etc) been around forever.  How can there be no starting point?  It's just always been here, forever, that sort of thing I just can't wrap my head around.

[Mackus]

Sometimes when I get drunk I like to talk about space.

 

My biggest questions:

 

1) If space is expanding what is it expanding INTO?

 

2)  How has space (or matter, etc) been around forever.  How can there be no starting point?  It's just always been here, forever, that sort of thing I just can't wrap my head around.

 

I'm not much of a theoretical physicist, but I've read some.

 

1)  You gotta consider the expansion of the universe in more than 3 dimensions, and one of them isn't time.  The ant on a balloon analogy is the best one I've heard.  Here it is explained pretty well.

 

2)  Big bang.  There was nothing, and then something happened and there was everything, all at the same location.  Then that everything started expanding and colliding and interacting.  There are a few theories that go in tandem that explain how everything got smoothed out and cooled down.

 

You should read some Stephen Hawking.  They are pretty quick reads and he gives good analogies for some of the harder to grasp theories without being too technical.  Brief History of the Universe and Universe in a Nutshell.  I've got another book that goes a bit more into the advanced physics and how they proved or tested a lot of this stuff while still staying pretty high level, but can't remember the name or the authors.

[Mackus]

Ah, found it.  Brave New Universe by Paul Halpern.

[Pedro Cerrano]

Yea but where did that "something" come from with the Big Bang?  There had to have been "things" around before the Big Bang to make the Big Bang happen.

[DJ MC]

Sometimes when I get drunk I like to talk about space.

 

My biggest questions:

 

1) If space is expanding what is it expanding INTO?

 

2)  How has space (or matter, etc) been around forever.  How can there be no starting point?  It's just always been here, forever, that sort of thing I just can't wrap my head around.

 

[DJ MC]

Fortunately we've got the Cosmos remake to look forward to in a week.

 

EDIT: A week from Sunday. March 9.

[Mackus]

61,000 km/h = 17 km/s (actually kinda slow for a meteorite)

 

Energy  = 1/2 * Mass * Velocity ^ 2

 

E = .5 * (400 kg) * (17000 m/s) * (17000 m/s)

 

E = 57,800,000,000 kg * m^2 / s^2   ::  1 kg*m^2/s^2 = 1 Joule

 

E = 57.8 x 10^ 9 Joules

 

The Hiroshima bomb was ~63 Terajoules, whihc is 63 x 10^12 Joules.

 

So this metorite hitting was about 1/1000th the impact of the Hiroshima bomb.

 

Based on the relative speed, my guess would be that this meteorite was travelling in the same direction as the moon.  The Earth & Moon orbit the sun at about 30 km/s.  So this thing was probably travelling 47 km/s in the same direction, and hit with a relative velocity of 17 km/s (like if you hit a car on the freeway from behind as opposed to head on).  If it were going the opposite direction, it'd be a relative velocity of 77 km/s.  That would be a  over a terajoule.

[Mackus]

Yea but where did that "something" come from with the Big Bang?  There had to have been "things" around before the Big Bang to make the Big Bang happen.

 

Nope, nothing!  Whatever you would think that space is currently expanding into, it's probably the same nothing that was around before the Big Bang.  An entity with no physical meaning. 

 

At least that's the theory.

[DJ MC]

An entity with no physical meaning. 

 

Yeah, I know how it feels.

 

*Pops a Zoloft*

[mweb08]

61,000 km/h = 17 km/s (actually kinda slow for a meteorite)
 
Energy  = 1/2 * Mass * Velocity ^ 2
 
E = .5 * (400 kg) * (17000 m/s) * (17000 m/s)
 
E = 57,800,000,000 kg * m^2 / s^2   ::  1 kg*m^2/s^2 = 1 Joule
 
E = 57.8 x 10^ 9 Joules
 
The Hiroshima bomb was ~63 Terajoules, whihc is 63 x 10^12 Joules.
 
So this metorite hitting was about 1/1000th the impact of the Hiroshima bomb.
 
Based on the relative speed, my guess would be that this meteorite was travelling in the same direction as the moon.  The Earth & Moon orbit the sun at about 30 km/s.  So this thing was probably travelling 47 km/s in the same direction, and hit with a relative velocity of 17 km/s (like if you hit a car on the freeway from behind as opposed to head on).  If it were going the opposite direction, it'd be a relative velocity of 77 km/s.  That would be a  over a terajoule.

So I guess Mackus has permission to use advanced baseball stats around here.

[mweb08]

Sometimes when I get drunk I like to talk about space.
 
My biggest questions:
 
1) If space is expanding what is it expanding INTO?
 
2)  How has space (or matter, etc) been around forever.  How can there be no starting point?  It's just always been here, forever, that sort of thing I just can't wrap my head around.

I hope this doesn't cause problems, but when someone says something like you do in #2, I always wonder if they apply that thought process to a god as well.

[Pedro Cerrano]

 

 

Nope, nothing!  Whatever you would think that space is currently expanding into, it's probably the same nothing that was around before the Big Bang.  An entity with no physical meaning. 

 

At least that's the theory.

 

Ok, but where did that "entity" come from?  Obviously, the Big Bang happened, which, in its simplest terms was a massive chemical reaction, right?  Well, where did the chemicals come from to make this happen?  What materials were around to create those chemicals?  Did they just appear out of thin air?  What did they appear into?  Suppose I was chilling before the Big Bang?  Would I just be floating around in nothing?  What is that nothing?  What is it made out of?

[Pedro Cerrano]

BTW, lest anyone think I am trolling this thread (as I have been known to do).  I am not.  I am dead serious about these questions.

 

They fascinate/perplex me.

 

I guess it's because of my background (attorney, excelled in the humanities, struggled with science and math) that I have issues dealing with theoretical things like the origins of space...then again, a large part of the law is theoretical as well.

[Pedro Cerrano]

Also, Mackus, I may check out some of the literature you suggested but even that link you provided made my head hurt.

[Mackus]

You keep going back further and further, and at some point, something has to spring from nothing.  It, and I'm not exactly sure what it is, can't start if that's not the case.  Because the question is "how did the universe start", and the universe is everything that exists.  So the only way for the universe to start is if it sprang from nothing, otherwise whatever it sprang from would be part of the universe, and we'd have to ask where that sprang from.

 

If the link made your head hurt, then don't skip straight to Brave New Universe   I think you would enjoy some of the Hawking, though.  It's been years since I read it, but I remember it being pretty good at coming up with ways to describe the complicated physical processes.  Give A Brief History of Time a shot.