[QUOTE=sltungle;42073795]The highest speed you can get it going is entirely dependent on how high you put the thing in the first place. You could tow it off to some arbitrarily absurd distance, drop it, and let it accelerate under Earth's gravity from tens of thousands of kilometres away. At any given point I want to say the instantaneous velocity that you could achieve would be equal and opposite to the escape velocity at that distance from Earth, but you'd have to integrate over the whole distance between the rod and the surface of Earth (keeping in mind that g is a function of x, or h, whatever you want to call it) at to achieve the total speed it could fall at.
As an example,
[URL]http://www.wolframalpha.com/input/?i=velocity+of+object+dropped+from+50000+km[/URL]
31 km/s is faster than the escape velocity of Earth at its surface (about three times higher from memory). If you're thinking of using kinetic bombardment in terms of a mortar attack, then sure, v_f = v_i (assuming no friction of course), but for just dropping the damn things you have to think of energy conservation and whatever you use to take the rods up to space is most likely going to be larger than the rods itself (you need fuel after all) so on the way down the thing is going to have less mass, same energy, and as a result a higher speed.[/QUOTE]
I don't think I buy that. Especially considering that WolframAlpha calculation was flawed, and held g as a constant for the whole distance.
Upon further science-ing, I decided that an object that has zero velocity with respect to the Earth and starts at an infinite distance away will acquire a speed of 11,185.59 m/s (escape velocity). So I still stand by my original statement. If they were just dropping the rods (as opposed to launching them) they could never go faster than escape velocity.
[QUOTE=Falubii;42091220]Upon further science-ing, I decided that an object that has zero velocity with respect to the Earth and starts at an infinite distance away will acquire a speed of 11,185.59 m/s (escape velocity). So I still stand by my original statement. If they were just dropping the rods (as opposed to launching them) they could never go faster than escape velocity.[/QUOTE]
that is accurate
All this physics talk makes me wish I took physics at the start of the year.
Would it comfort you if I said that the density of tungsten and gold is close enough that you could make very convincing "solid gold" objects by electroplating tungsten?
[QUOTE=Falubii;42091220]Upon further science-ing, I decided that an object that has zero velocity with respect to the Earth and starts at an infinite distance away will acquire a speed of 11,185.59 m/s (escape velocity). So I still stand by my original statement. If they were just dropping the rods (as opposed to launching them) they could never go faster than escape velocity.[/QUOTE]
I still felt that seemed slightly weird considering how far the gravitational pull of Earth extends before being sort of overpowered by, for example, the sun, but after having a good hard long think about it (by which I mean about 5 - 10 minutes) I guess it's pretty much a case of the sum of an infinite geometric series with a ratio between successive terms being less than 1. The further away you get the more and more negligible the velocity gained from falling under Earth's gravity becomes to the point whereby it just converges on, like you said, the escape velocity.
[editline]7th September 2013[/editline]
I presumed Wolfram Alpha would have been smart enough to take into account changing values of g, but apparently not.
That thing can fluctuate between incredibly smart and retatdedly stupic.
[QUOTE=Cakebatyr;42106357]Would it comfort you if I said that the density of tungsten and gold is close enough that you could make very convincing "solid gold" objects by electroplating tungsten?[/QUOTE]
My method is superior. I just take some platinum and bombard with particles it until it turns into radioactive gold.
All I need to do now is find a lot of platinum...
Do you guys thing we'll ever reach the plasma energy breakeven point within our lifetimes?
[editline]23rd September 2013[/editline]
This is with conventional fusion reactors (nukes don't count).
[QUOTE=booster;42283234]Do you guys thing we'll ever reach the plasma energy breakeven point within our lifetimes?
[editline]23rd September 2013[/editline]
This is with conventional fusion reactors (nukes don't count).[/QUOTE]
I'm optimistic about ITER. I'm hoping it will provide break even fusion.
Might be doing a thesis about [URL="http://www.nature.com/nature/journal/v495/n7440/full/nature11971.html"]MR fingerprinting[/URL], that is, if the professor answers his fucking emails. I'm gonna go bother him IRL tomorrow...
Oh btw, why the fuck does the New Scientist site have a [URL="http://dating.newscientist.com/s/a/17833"]dating-tab[/URL]? I was considering switching from Scientific American to NS but fuck that. If only my university offered a cheap Nature subscription :(
[QUOTE=sltungle;42292973]I'm optimistic about ITER. I'm hoping it will provide break even fusion.[/QUOTE]
I too am optimistic about that project.
One of their goals is to reach Q10 or over.
I don't know why, but I'm more hyped over this project than I ever was with CERN.
Ruined my quantum physics lecturer's joke yesterday. He starts telling the joke by going, "a physicist, a mathematician and an engineer walk into a bar..." And then I shouted out, "and the engineer pays for everyone's drinks because he gets paid more!"
He seemed to get a pretty big kick out of it at least (as did the rest of the class). Then the burn set in that 75% of the class (myself included) are going to be making far less than the remaining 25% soon enough.
An experimental physicist sits down next to a mathematician at a bar. He turns to the mathematician and asks, "So, what sort of work do you do?" The mathematician says, "Knot theory." And the physicist says, "Me neither!"
Are you enrolled in a science jokes class?
What's the basis behind the theory, that time really fucks itself over when it's inbetween 2 black holes.
[QUOTE=booster;42325037]What's the basis behind the theory, that time really fucks itself over when it's inbetween 2 black holes.[/QUOTE]
Is there such a theory? It seems to me that there would be nothing special going on between two black holes.
I wish I could do science...
Oh man why does everyone do physics
Anyone else do bioengineering?
There's a lot more engineers and biologists than physicists.
[QUOTE=Laputa;42325368]Oh man why does everyone do physics
Anyone else do bioengineering?[/QUOTE]
Not everyone. Just the cool ones.
[QUOTE=JohnnyMo1;42325164]Is there such a theory? It seems to me that there would be nothing special going on between two black holes.[/QUOTE]
It's something I heard Neil DeGrasse Tyson talk about during a conference where a kid asked him what would happen if two black holes collided.
He then explained the unique properties of black holes orbiting eachother. He also mentions how these properties "might" allow for backwards timetravel.
[QUOTE=booster;42327463]It's something I heard Neil DeGrasse Tyson talk about during a conference where a kid asked him what would happen if two black holes collided.
He then explained the unique properties of black holes orbiting eachother. He also mentions how these properties "might" allow for backwards timetravel.[/QUOTE]
I've never heard of that particular solution, but backwards time travel is not really a feature unique to that scenario. Closed timelike curves, which can transport a massive particle back in time, appear in all sorts of spacetimes. I can't really think of anything that makes orbiting black holes super special in this regard. Single rotating black holes seem to exhibit them, but I just read a paper which suggests that that's a coordinate artifact.
You may be out of luck, though. Closed timelike curves are widely conjectured (but not yet proven) not to appear in reality, i.e. there is some condition we don't know about yet that forces realistic solutions to the Einstein field equations to be globally hyperbolic (which means no CTCs).
[editline]27th September 2013[/editline]
But yeah, the basis is that some solutions have allowed paths of massive particles which return to a previous point in time without needing the particle to travel locally faster than light. I've never heard of the solution he's referring to, though.
Man backwards timetravel is pure brainfuckery.
Also remember reading (not sure about the credibility of this though) in one of Michio Kaku's books, where he mentions a theory that all electrons in the universe is the same electron. It just has travelled a lot back&forth in time.
He mentioned that one support for this claim was that all electrons are indistinguishable from one another.
[QUOTE=booster;42328939]Man backwards timetravel is pure brainfuckery.
Also remember reading (not sure about the credibility of this though) in one of Michio Kaku's books, where he mentions a theory that all electrons in the universe is the same electron. It just has travelled a lot back&forth in time.
He mentioned that one support for this claim was that all electrons are indistinguishable from one another.[/QUOTE]
I believe it was Feynman (or a student or colleague of his maybe) that first postulated the 'one electron universe' hypothesis. All electrons could be the same electron travelling along different worldlines in the 'positive' time direction and all positrons could be that same electron moving backwards through time along different worldlines.
Well I guess the direction of time which you choose is kind of arbitrary - it just depends on which way you want to label things. It could be that the positron is actually moving forwards through time instead of backwards, but you wouldn't be able to tell because we're moving forwards so everything looks like it's going forwards to us.
I thought all subatomic particles were pretty much indistinguishable. Is that not true?
[QUOTE=Falubii;42334918]I thought all subatomic particles were pretty much indistinguishable. Is that not true?[/QUOTE]
Yes. Well, not all subatomic particles necessarily but all elementary particles yes. If they weren't we wouldn't be able to characterise anything. That's what the whole point of an elementary particle is - you start taking big shit apart until you reach a point whereby you can't quantify any differences.
[QUOTE=sltungle;42343124]Yes. Well, not all subatomic particles necessarily but all elementary particles yes. If they weren't we wouldn't be able to characterise anything. That's what the whole point of an elementary particle is - you start taking big shit apart until you reach a point whereby you can't quantify any differences.[/QUOTE]
You know what I meant. I don't think protons and neutrons are the same thing.
If there's one electron travelling back and forth in time shouldn't it appear to vanish at some point?
[QUOTE=Krinkels;42350143]If there's one electron travelling back and forth in time shouldn't it appear to vanish at some point?[/QUOTE]
Not if it oscillates back and forth between the beginning and end of time.
I can't wait until I can learn quantum field theory. It's a fuckin' neat subject. The way that it preserves causality is really elegant: A particle propagating faster than light from point a to point b looks exactly like its antiparticle propagating from b to a in another frame, and the probability of those events occurring exactly cancel.
Elegant as fuk.
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