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questions about planets

 
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I've few questions about planets. Hope I get logical answers to them here:

1. Have men reached to any planet other than moon? I think, no. Can anyone tell, why?
2. Why moon revolves around earth?
3. Why moon doesn't go towards sun or somewhere in universe (I think it's because of earth's gravity but then why it doesn't come towards earth?)

Thanks.
 
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1) Moon is not a planet. Its a satellite. Watch Star Trek for a detailed answer to this question
2) Because earth is the center of the universe
3) It does go and come back. Thats how we see the phases of the moon.
 
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1) Moon is not a planet. Its a satellite. Watch Star Trek for a detailed answer to this question


You can watch Star Trek on that satellite ? How much per month ?
 
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ankur rathi wrote:1. Have men reached to any planet other than moon? I think, no. Can anyone tell, why?


No. Why? Because it is not easy to get to another planet. NASA has been thinking about sending people to Mars, but such a mission would be very hard (much harder than going to the Moon) because Mars is much, much farther away than the Moon. It would also be very expensive (hundreds of billions of dollars!) and there are technological problems for which we don't have any good solutions yet. For example, there's a lot of dangerous radiation in space, and there's no good way to protect astronauts from that radiation. A mission to Mars would also take at least two years or so, because Mars is so far away. Maybe there will be humans on Mars sometime this century, but it won't be anytime soon.

ankur rathi wrote:2. Why moon revolves around earth?


Because the Moon is a natural satellite of the Earth. The current scientific idea of how the Moon came into existence is an interesting story: scientists think that in the early time of the Solar System, Earth collided with another large protoplanet, and the Moon came out of this collision; see Giant impact hypothesis.

ankur rathi wrote:3. Why moon doesn't go towards sun or somewhere in universe (I think it's because of earth's gravity but then why it doesn't come towards earth?)


Because of how the physics of gravity work. Things don't just fly anywhere by themselves, everything works according to the laws of physics.
 
ankur rathi
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Maneesh Godbole wrote:1) Moon is not a planet. Its a satellite. Watch Star Trek for a detailed answer to this question
2) Because earth is the center of the universe
3) It does go and come back. Thats how we see the phases of the moon.



Thanks Maneesh.

I just checked definition of satellite, it's: Man-made equipment that orbits around the earth or the moon. Anyway, let's say it's called satellite because it revolves. I'd watch the movie when I get a chance but any brief explanation of why men are not able to reach on any planets?
For 3, we see different phases because it revolves around earth - I mean, someone from earth should always (except during moon eclipse time) see complete moon...
 
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ankur rathi wrote:
I just checked definition of satellite, it's: Man-made equipment that orbits around the earth or the moon.



Time to get yourself a new dictionary!


1. Astronomy. a natural body that revolves around a planet; a moon.
. . .
5. a device designed to be launched into orbit around the earth, another planet, the sun, etc.


satellite

ankur rathi wrote: any brief explanation of why men are not able to reach on any planets?



The largest rockets we have can't lift enough payload to keep a man alive for the 9 months or so it would take to get to mars.

ankur rathi wrote: I mean, someone from earth should always (except during moon eclipse time) see complete moon...


Because the moon is rotating around the Earth and lit from the sun, it is not always fully lit. see here
 
Jesper de Jong
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ankur rathi wrote:I just checked definition of satellite, it's: Man-made equipment that orbits around the earth or the moon.


Natural satellite
 
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Mars is the most viable planet to travel to, and it's still 6-9 months away. Then they would have to stay there till the next cycle begins (two years I think. Maybe four). Think about that for awhile, and you will come up with numerous issues that need to be solved.
 
Jesper de Jong
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Can People Go to Mars?

NASA has a mystery to solve: Can people go to Mars, or not?

"It's a question of radiation," says Frank Cucinotta of NASA's Space Radiation Health Project at the Johnson Space Center. "We know how much radiation is out there, waiting for us between Earth and Mars, but we're not sure how the human body is going to react to it."

 
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Think of gravity as a string. There is a string between the Earth and the Moon. The moon keeps trying to fly away, but the string keeps pulling it back. It's just like tying a ball to a string and whipping it around your head. If at any point you let go, the ball would fly off.

the reason the moon doesn't fly off towards the sun, even though the Sun's gravity is stronger, is that the Sun is further away. It's so far away, it doesn't have much of an effect on the orbit of the moon (but it DOES have a small effect).

Planets are FAR away, compared to the moon. the Moon is anywhere from 360,000 km to 405,000 km.

Mars can be anywhere from 55,000,000 km to 401,000,000. It all depends on where they are in their orbits around the sun. So, at BEST, Mars is 100 times further.
 
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Steven Mann wrote:Mars is the most viable planet to travel to, and it's still 6-9 months away. Then they would have to stay there till the next cycle begins (two years I think. Maybe four). Think about that for awhile, and you will come up with numerous issues that need to be solved.



What cycle? For what they have to wait?
 
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Vikas Kapoor wrote:
What cycle? For what they have to wait?



It has to do with the relative position of the two planets. Sometimes they are very close. And sometime they are on opposite sides of the Sun. To get to Mars, you have to take off (from Earth) during a time period, so when you reach Mars' orbit, the planet is actually there. These periods, or windows, are very small, and they come at a cycle that are years apart.

Henry
 
Henry Wong
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Jesper Young wrote:Can People Go to Mars?

NASA has a mystery to solve: Can people go to Mars, or not?

"It's a question of radiation," says Frank Cucinotta of NASA's Space Radiation Health Project at the Johnson Space Center. "We know how much radiation is out there, waiting for us between Earth and Mars, but we're not sure how the human body is going to react to it."



Although Radiation is a problem, it can be solved with enough shielding. I always thought that the big issues were food, water, and air. You need enough for the trip there, for waiting to the next window, and for the trip back.

Henry
 
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Astronomy is full of surprises and imaginations and if you have read sci-fi books in your childhood then you might have found it captivating.

I think untill we have a super sonic photonic vehicle (~ Speed of light) it is very hard to *explore* universe.
 
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Vikas Kapoor wrote:...untill we have a super sonic vehicle

super sonic? Got those. You mean super-photonic!
 
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The cost of sending men to Mars is staggering. Fortunately, Mars needs women, so if we could get a substantial price break using female astronauts.
 
fred rosenberger
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I think the shuttle on re-entry is doing something like Mach 25. That's about 30,000 kph. That would take about 70 days to get to Mars, if you could travel in a straight line at a constant speed.

(my math could be off...)
 
marc weber
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In 1902, a projectile mishap agitated the moon. It has been revolving around the Earth since then, watching and waiting for an opportunity to strike back.


 
Bear Bibeault
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fred rosenberger wrote:I think the shuttle on re-entry is doing something like Mach 25. That's about 30,000 kph. That would take about 70 days to get to Mars, if you could travel in a straight line at a constant speed.

(my math could be off...)



Without any research on my part, I believe that a big portion of that speed comes from simple gravity pulling the shuttle towards Earth. I had a professor in college that simplified orbits to "controlled falling". Basically, the Earth's gravity has caught the moon and various man-made things, and they are falling toward Earth. However, the Earth is a constantly moving target, so as it falls we move out of the way and it just kind of continues to fall. Its not the most precise definition, but it makes sense.

Back to the point...getting a ship to sustain those speeds would be very difficult, unless Cmr. LaForge can divert power from the life support systems on decks 4-19 to the engines.
 
Bear Bibeault
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It would also entail decoupling the phase converters and shifting the bipolar tachyon pulse emitters to inverse polarities.
 
W. Joe Smith
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But first you have to get the tribbles out of the plasma injectors!
 
Bear Bibeault
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Didn't I tell you to do that last week?
 
W. Joe Smith
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Damn it Bear, I'm a programmer not an animal control specialist!
 
marc weber
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Bear Bibeault wrote:It would also entail decoupling the phase converters and shifting the bipolar tachyon pulse emitters to inverse polarities.


"We may go up in the biggest ball of fire since the last sun in these parts exploded, but we've got to take that one-in-ten-thousand chance!"
 
marc weber
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Of course, we've completed several manned expeditions to Pluto, but since it's no longer a planet...
 
ankur rathi
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Maneesh Godbole wrote:
2) Because earth is the center of the universe



This can't be a reason. If it is, then why sun doesn't revolve around earth?
 
marc weber
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ankur rathi wrote:...why sun doesn't revolve around earth?


Because it would crash into the moon.
 
Bear Bibeault
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marc weber wrote:

ankur rathi wrote:...why sun doesn't revolve around earth?


Because it would crash into the moon.



Well, it occasionally does -- that's what caused all those burn marks.
 
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fred rosenberger
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W. Joe Smith wrote:Without any research on my part, I believe that a big portion of that speed comes from simple gravity pulling the shuttle towards Earth.



From here, shuttle in orbit is 5 miles / sec == 18,000 mph

18 000 mph = 28 968.192 kph or roughly 30,000 kph.
 
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Newton's orbital thought expirement is still the best way to understand the concept of a stable orbit.
 
W. Joe Smith
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Bear Bibeault wrote:Newton's orbital thought expirement is still the best way to understand the concept of a stable orbit.



That's what I was trying to say....I guess Newton was much better at this gravity stuff than me.
 
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Jesper Young wrote: NASA has been thinking about sending people to Mars, but such a mission would be very hard (much harder than going to the Moon) because Mars is much, much farther away than the Moon. It would also be very expensive (hundreds of billions of dollars!) and there are technological problems for which we don't have any good solutions yet. For example, there's a lot of dangerous radiation in space, and there's no good way to protect astronauts from that radiation.



The real problem is that there is little reason to send humans to Mars. It would be insanely expensive. Not just very expensive, national budget busting expensive. NASA always thinks about manned exploration. They love sending men. But its a really bad idea. Humans are fragile, and raise the costs by several orders of magnitude. Just send robots. Oh, yeah, they did that, on a shoestring budget, with rovers that were supposed to last a few months. Four years later, we are still getting great science from the cheap rovers.

Rocket with rover on it blows, up, say "drat" and build another one. Rocket with astronauts on it blows up, nation goes into mourning, budgets go up by a factor of ten to prevent it. Yo NASA, rockets blow up, get used to it.

Look at the nearly 30 years NASA has wasted on the Shuttle to low earth orbit. There is nothing new in low earth orbit.

The key thing is that the race to the moon was a proxy race for the war with Russia/USSR. When the Soviets put Sputnik in orbit, everyone knew that they could put a nuclear bomb in orbit. While the race was wrapped in the American flag, it was a military effort with a thin veneer of science. Of course, most of the early scientists were Nazi scientists, but that did not matter. Beating the Russians was all that mattered.
 
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Even if we find a way to get around the radiation problem, how are we going to deal with Bigfoot if he catches us?
 
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Pat Farrell wrote:NASA always thinks about manned exploration. They love sending men. But its a really bad idea. Humans are fragile, and raise the costs by several orders of magnitude. Just send robots.


 
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Maneesh Godbole
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Pat Farrell wrote:NASA always thinks about manned exploration. They love sending men. ...


This sexual discrimination has to stop. Why is it that men get to go? Women too are up to the mark. Let us have a womanned expidition.
Feminists of the world, unite!
 
Devaka Cooray
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NASA has recently discovered water on Mars.
 
Pat Farrell
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Maneesh Godbole wrote:This sexual discrimination has to stop. Why is it that men get to go? Women too are up to the mark. Feminists of the world, unite!


They have sent some women, I meant "man" in the mankind sense. Woman are too fragile to send into space as well. I'm sure that there has been sex in space, but no one talks about that. I mean, six months in the ISS with women. Even blue water sailors get to make port calls.
 
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