General Questions

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If Superman held some Plutonium in his hand, could he make it go super critical by squeezing it?

More seriously, escape velocities.

We all know to escape the Earths gravity, a rocket needs to reach escape velocity.

Why is this?

If I was in a rocket, heading straight up at 10,000mph (for this experiment i have an infinite fuel supply), why can I not keep going at 10,000mph? The air is getting thinner, surely gravity isn't getting stronger is it?
 
Loon
I believe that's one of the perks of being a parent; you don't need a reason to say no.
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you better belive it

I can't say I've had that happen to me though, my mom is pretty cool about stuff like that. Plus I don't ever ask to do anything, so when I finally do, I'm almost guaranteed I'll be able to.
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your mum isn't as cool as Jacks mum though :)

Pupik
Explaining things takes too much of our time, and if you find holes in our hypothesis, theory, and explanation, you'll have to suffer The Higher Court of Mom and Dad. T.H.C.M.D. can have swift, final, and draconian punishments and you have no right to witnesses, attorneys, testimony, exhibits, phone calls, or dessert. But sometimes, you get 5 minutes of Time Out or can get off with an apology.
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Well said......Jack take note!
 
DQuaN
If Superman held some Plutonium in his hand, could he make it go super critical by squeezing it?
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Yes - that's how plutonium-based fission works. Especially in, you know, *bang*.

DQuaN
We all know to escape the Earths gravity, a rocket needs to reach escape velocity.

Why is this?

If I was in a rocket, heading straight up at 10,000mph (for this experiment i have an infinite fuel supply), why can I not keep going at 10,000mph? The air is getting thinner, surely gravity isn't getting stronger is it?
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Interesting question. I think I'll field this one to danoff.
 
Famine
Interesting question. I think I'll field this one to danoff.
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Famine doesn't know something. :eek:

It must be an April Fool's joke... 💡
 
I stumped Famine!! :cheers:


*edit*
wiki
Planetary or lunar escape velocity is sometimes misunderstood to be the speed a powered vehicle (such as a rocket) must reach to leave orbit; however, this is not the case, as the quoted number is typically the surface escape velocity, and vehicles never achieve that speed direct from the surface.

In fact a vehicle can leave the Earth's gravity at any speed. But at the instant the propulsion stops, the vehicle can only escape if its speed is greater than or equal to the local escape velocity at that position- at sufficiently high altitude this speed can approach 0 m/s.
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So it seems that escape velocity is the speed you must be travelling at when the propulsion stops in order not to fall back to Earth.
 
Infinite fuel supply makes escape velocity irrelevant. It's when the rocket engine stops and you're coasting (weightless) that you need to be at escape velocity to get out of the gravity well. If you're not coasting fast enough, you fall back.

Assuming your parents trust you enough to let you leave in the first place.
 
wfooshee
Infinite fuel supply makes escape velocity irrelevant. It's when the rocket engine stops and you're coasting (weightless) that you need to be at escape velocity to get out of the gravity well. If you're not coasting fast enough, you fall back.
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That's basically right. Escape velocity assumes that thrusting is over and done with. You're not using any propellant - you're simply on a ballistic trajectory. Escape velocity is a target for a rocket engine to achieve before shutting off. There's nothing really all that special about it.

Also, you'll notice from the escape velocity equation:

http://en.wikipedia.org/wiki/Escape_velocity

Vescape = sqrt(2gm/r)

The "r" in the bottom of that equation indicates that your escape velocity very much depends on how far you are out of the earth's gravity well. If you're at 1000km altitude, your escape velocity is much less than if you're at sea level. So the escape velocity target for a particular rocket to achieve before shutting off also depends on the distance the rocket achieves before shutting down.

Clear? It's simply how fast you have to be going so that gravity can't pull you back in.

Edit: Also note that g and m are valid for any gravity field. So there is an escape velocity for Mars (which will be much different than Earth), and there is one for the solar system.
 
V1P3R
:lol: Protection against Copyright. Oh Man, I might have to dub that the highlight of my day.
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Infringement! The shields came close to wrecking this modem twice now...

Not as bad as the Dallas comment I made:

That second state isn't Dallas?
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As for the question at hand, does this mean that Pioneer 10 was still fully operational when it left the solar system to enable a departure from the solar system?

Succeeding post: Never caught that!
 
Is it common to suddenly experience a lot of nosebleeds? I think for the last week I've had one every time I take a shower and about four randomly in that time out of the shower. I'm not really worried about it, but it's getting rather annoying.

The only things I can find that are different could be maybe spring coming (although I've never had any allergies) and that I've started using Ritalin.

Any ideas as to what's causing this?
 
Philly
Is it common to suddenly experience a lot of nosebleeds? I think for the last week I've had one every time I take a shower and about four randomly in that time out of the shower. I'm not really worried about it, but it's getting rather annoying.

The only things I can find that are different could be maybe spring coming (although I've never had any allergies) and that I've started using Ritalin.

Any ideas as to what's causing this?
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High blood pressure? Sudden change in temperature? Could be a number of things. This used to happen to me a lot. You could have developed some new allergies for all we know.
 
It's kinda happened before, but never to this extent. I've had like four happen over a period of a few days and have it go away. Just this time it's lasted much longer and getting really bothersome when I'm almost done with a shower and have to sit there for a few more minutes for it to stop. The drugs I'm taking mention only being more prone to bruising and bleeding, but it says those are very rare and serious, which this isn't, so that probably isn't it.
 
This is your first year in Michigan, right? The winter air in Michigan (well, the whole midwest, really) is much colder and much drier than you're used to. Dry air can easily cause nosebleeds. Could be that the capillaries in your nasal passages have finally given up after six months of torture. If this is the cause, your nosebleeds should disappear as the weather improves. You might also look into getting a humidifier for your bedroom.
 
That makes a lot of sense. I thought it was slightly odd that it should happen at the end of winter. Hopefully it'll get better.
 
Is it normal to have a recurring headache in the same spot? As in, it happens at one point or another almost every day over at least a week?
 
try to drink a little more water it might be that you are dehydrated at that point in time. or it might be that you a little stressed at a certain point in time each week in that case try reading a book about jokesl, or something to get a laugh.
 
I definitely get enough water, and I get more than enough laughs daily.

All I have to do for a laugh is log on to GTP and follow the indigo brick road. At least that's how easy it has been lately.

These headaches have been occurring almost every day for the past two and a half weeks. They're always at the very top of my head.


But thank you for the suggestions. :) I'll still try drinking more water.
 
Philly
Is it common to suddenly experience a lot of nosebleeds? I think for the last week I've had one every time I take a shower and about four randomly in that time out of the shower. I'm not really worried about it, but it's getting rather annoying.

The only things I can find that are different could be maybe spring coming (although I've never had any allergies) and that I've started using Ritalin.

Any ideas as to what's causing this?
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Have you tried stop picking at it?;)
 
Philly
Is it common to suddenly experience a lot of nosebleeds? I think for the last week I've had one every time I take a shower and about four randomly in that time out of the shower. I'm not really worried about it, but it's getting rather annoying.

The only things I can find that are different could be maybe spring coming (although I've never had any allergies) and that I've started using Ritalin.

Any ideas as to what's causing this?
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Nosebleeds can be chronic. Do you have a history of them?
 
Not really. There have been a couple instances where I've had three or four in a few days, but nothing like this.
 
Hey, my mom bought a set of one of those compact fluorescent bulbs. I tried screwing one in and it didn't work when I turned on the lights. When I went to take it out, I noticed that it had cracked.

Am I at risk for Mercury poisoning/contamination because of the crack or are CFLs only that dangerous when they break completely? I noticed some of the white part of the tubing had turned clear around the cracks, so I'm a bit worried.
 
Mayb you have a deficit of ascorbine acid? That can cause nosebleeds.


:)
 
Omnis
Hey, my mom bought a set of one of those compact fluorescent bulbs. I tried screwing one in and it didn't work when I turned on the lights. When I went to take it out, I noticed that it had cracked.

Am I at risk for Mercury poisoning/contamination because of the crack or are CFLs only that dangerous when they break completely? I noticed some of the white part of the tubing had turned clear around the cracks, so I'm a bit worried.
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I don't think so. I heard that 12,000 bulbs of that type would have to shatter and one would have to stand in the middle of it in order to possibly get an effect, though.

If that was the case, then fluorescent bulbs would be a regular health hazard. Not enough mercury is present in the bulbs to be the cause of any mercury-induced effects.
 
How did they decide which end of the Earth was North and which was South, and which end would be on top in maps?
 
MINICOOPER120
How did they decide which end of the Earth was North and which was South, and which end would be on top in maps?
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Probably alot to do with Britain...

Notice also that most maps have Britain right in the middle, and that the gaps between the latitude lines (which are supposedly equidistant) are much further apart around the UK.. the reasons for that are probably historical or have something to do with allowing more detail in these regions, but it also has the curious effect of making the UK look alot bigger than it actually is...

Also, it depends on what maps you are looking at - at which way round you decide to look at them!
 
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