Behold the Mountains of Mars!

Dubh Geannain

Scioch wrote: »

The notion that gravity is caused by the spinning of the earth is a pretty wide held view in my experience. Its a plausible answer to someone who hasnt looked into it.

I suppose the best way to quash that belief is to liken it to a spinning roundabout. You let go you get thrown off.

Without gravity we'd all be turfed out into space by the earth's rotation.

Scioch

Deleted User wrote: »

When you've put up with mumbo jumbo in the name of science for decades, you sometimes get a bit irritable about these matters.

When I want to get to grips with something I don't know I either work it out, look it up, or ask questions. I don't just wander in to a discussion somewhere and express whatever random opinion I happen to hold as if it were correct, in the vague hope that either (a) it just happens to be correct or (b) that if it isn't, someone reliable and knowledgeable will point me in the right direction.

That's my approach, and I happen to think it works. If it's not yours, that's a matter for you. 'n'all'n'anyways we are, as I said already, a long way off topic. So let's just agree to disagree and get back to the pictures from another planet.

You cant expect people to research everything you want to say before saying it on an internet forum. The poster wasnt aware they were wrong and I sincerely doubt they just posted whatever popped into their head in the hopes it was was. They simply had the wrong understanding and by the looks of it was happy to be corrected. There is nothing wrong with that. People are allowed to be wrong sometimes. Takes little effort to point them in the right direction. No more than it takes to ridicule them anyway. So personally I'd go for the former seeing as the latter achieves nothing.

I wont agree to disagree I'm afraid, I dont think it fair at all to expect people not to be wrong on anything ever. This is a discussion forum not a scientific journal. People are free to comment and say whatever they like and should not be ridiculed for being mistaken.

Captain Chaos

Dubh Geannain wrote: »

Without gravity we'd all be turfed out into space by the earth's rotation.

Without gravity a star cannot function and our sun would not exist, or any of the planets have formed at all.

Scioch

Scioch wrote: »

I wont agree to disagree I'm afraid....

No bother. That's not my call anyway.

Scioch

Dubh Geannain wrote: »

I suppose the best way to quash that belief is to liken it to a spinning roundabout. You let go you get thrown off.

Without gravity we'd all be turfed out into space by the earth's rotation.

Yeah its a handy one to set right, but its not that far fetched to think a spinning planet can affect a force on the things on it because it does. As ya say though the force would propel us outward so they would have it backwards and then think that must be gravity. But you can see why so many people would think thats what gravity was. A little common sense with a misunderstanding which leads to a false conclusion.

Queen-Mise

Dubh Geannain wrote: »

I suppose the best way to quash that belief is to liken it to a spinning roundabout. You let go you get thrown off.

Without gravity we'd all be turfed out into space by the earth's rotation.

This makes a lot of sense.

Is there a simple analogy that explains gravity? Is there any experiments you can do at home that could make it clearer?

Blowfish

Queen-Mise wrote: »

Is there a simple analogy that explains gravity? Is there any experiments you can do at home that could make it clearer?

This is a (very) simplistic explanation.

Queen-Mise

Queen-Mise wrote: »

This makes a lot of sense.

Is there a simple analogy that explains gravity? Is there any experiments you can do at home that could make it clearer?

Gravity is remarkably weak, but it doesn't seem that way to us. The easy ways to demonstrate this are to hold something in your hand (not something breakable) and then let it go - or to hold a pin with a magnet.

I'm not kidding with the above examples. Gravity is the weakest of the various forces that act on physical objects. Everything in the universe pulls on everything else - but the amount of pulling that an object does depends on how big it is and how far away it is from you. So where gravity gets its advantage over the other forces (electromagnetic force, the strong nuclear force and the weak nuclear force) is that it works at a bit of a distance. The Earth is far bigger than we are and far heavier, so it pulls on us a lot harder than we pull on it.

The force of gravity attracts objects. Yet even with the entire force of the Earth's gravity pulling on a weight, you can stop it working by simply putting your hand in the way - and if the object isn't too big you can do it effortlessly.

Electromagnetism is weaker than gravity, but at short distances gravity loses its advantage and electromagnetic forces take over. That's what the pin and the magnet experiment shows. Even a small magnet with a tiny force will hold a pin against the entire force of the Earth's gravity. But if you pull the pin an inch or two away, the magnet won't have enough force over that distance and the Earth's gravity will win out. But overall, electromagnetism is a far stronger force than gravity - I can't remember exactly, but you're talking a multiple of 1 with about 35 zeros after it.

The crucial reason why the spinning roundabout analogy is important is this: Gravity never repels, it can only attract. So if a force throws you away from something, it can't be like gravity.

Finally, if you fall off a wall or out of a tree (I don't recommend either), you fall towards the Earth. But the Earth also falls towards you. :eek:

--Kaiser--

While we're correcting stuff: gravity is not a force. Not in the same way that electromagnetic and weak and strong atomic forces are. Gravity is the acceleration of a body towards another one due to curvature of space-time

So does all of this mean there won't be a penis drawn on the surface of Mars?

Ho-hum.

ScumLord

Queen-Mise wrote: »

And this is why I am not a scientist & avoided this stuff in school - it made sense to me :o:o

Ah now, with that attitude you'll never learn anything. :pac:

On the face of it gravity looks quite simple. Everything has gravity but the bigger the thing is the more gravity it has (well the more mass (heavier) it has the more gravity it has) it can almost be thought of like magnets that work on everything not just some metals. The bigger the magnet the more power it has to pull things towards it.

When you get into the nitty gritty of what gravity actually is it get's complicated, odd and confusing because it's bending time and space and it's not really pulling things around at all.

Prick!

I can understand what gravity is, just not how it's created.

I know how the magnetic field is created, due to the iron core. But what makes gravity?

norrie rugger

ScumLord wrote: »

Ah now, with that attitude you'll never learn anything. :pac:

On the face of it gravity looks quite simple. Everything has gravity but the bigger the thing is the more gravity it has (well the more mass (heavier) it has the more gravity it has) it can almost be thought of like magnets that work on everything not just some metals. The bigger the magnet the more power it has to pull things towards it.

When you get into the nitty gritty of what gravity actually is it get's complicated, odd and confusing because it's bending time and space and it's not really pulling things around at all.

And that it could be a stronger force, in other dimensions, which would account for its relative weakness in ours

ScumLord

Prick! wrote: »

I can understand what gravity is, just not how it's created.

It's hard to say, my normal tactic of asking google and regurgitating the first answer only throws up this.

Actually, we can't say how gravity is created.

You're getting into the use of dark energy and other dark things and in science terms dark means they're guessing and don't really have an answer.

But if you image space to be water and then you put matter into that water the water has to move around the object. It's that movement of water around the object that is creating the gravity. I think, not sure though.

ScumLord

norrie rugger wrote: »

And that it could be a stronger force, in other dimensions, which would account for its relative weakness in ours

Well clearly we have to find these other dimensions and destroy them.

Scioch

ScumLord wrote: »

But if you image space to be water and then you put matter into that water the water has to move around the object. It's that movement of water around the object that is creating the gravity. I think, not sure though.

And the "water" is the higgs field ?

--Kaiser--

ScumLord wrote: »

But if you image space to be water and then you put matter into that water the water has to move around the object. It's that movement of water around the object that is creating the gravity. I think, not sure though.

I like Hawking's description of gravity using a trampoline (space-time), a bowling ball (a massive object such as the sun) and marbles (objects subject to the gravity of the massive object)

Prick!

Really hard to get my head around it. I want to know!!!!! :P

Queen-Mise

ScumLord wrote: »

Ah now, with that attitude you'll never learn anything. :pac:

On the face of it gravity looks quite simple. Everything has gravity but the bigger the thing is the more gravity it has (well the more mass (heavier) it has the more gravity it has) it can almost be thought of like magnets that work on everything not just some metals. The bigger the magnet the more power it has to pull things towards it.

When you get into the nitty gritty of what gravity actually is it get's complicated, odd and confusing because it's bending time and space and it's not really pulling things around at all.

I can work with the magnet analogy - it pulls everything not just metal. Does an object in space need an atmosphere to have gravity? Would a really, really, big asteroid have gravity?

Do gravity weaken the further into the sky/atmosphere you go?

KAGY

Queen-Mise wrote: »

I can work with the magnet analogy - it pulls everything not just metal. Does an object in space need an atmosphere to have gravity? Would a really, really, big asteroid have gravity?

Do gravity weaken the further into the sky/atmosphere you go?

Stick with the magnet analogy, gravity pulls things together. but gravity can only pull, not push. It doesn't have an opposite like the north and south pole.
Everything that has mass (is made up of stuff) has gravity, the more mass something has, the bigger the pull it has, but as was said before its a very weak force so you need a very big item before you can feel it.
If youre a 90kg man On Mars you'd feel as if you weighed 60 ( I think) on the moon you'd feel about 11kg.
You're right that the force of gravity lessens with distance ( from the centre of the planet) so you actually weight a few grams less when you're on an aeroplane. On an asteroid with weak gravity you could jump high enough that you wouldn't come down.
All this can be worked out with a few simple equations, but that's a different days work.

Gravity keeps the atmosphere in place.

KAGY

KAGY wrote: »

Everything that has mass has gravity...
All this can be worked out with a few simple equations, but that's a different days work.

Pretty sure that I worked out in leaving cert that the midwife has a bigger gravitational pull on a baby being born than the nearest star (sun excluded)

KAGY

--Kaiser--

Queen-Mise wrote: »

I can work with the magnet analogy - it pulls everything not just metal. Does an object in space need an atmosphere to have gravity? Would a really, really, big asteroid have gravity?

Do gravity weaken the further into the sky/atmosphere you go?

All things have gravity - one definition of gravity is that it's the attraction of every body in the universe to every other body due to the masses of each.

Gravity does weaken the farther you go from the body, that's why astronauts can float around up in orbit, not plummet towards earth (like Baumgartner or Kittinger)

Knifey Spoony

--Kaiser-- wrote: »

All things have gravity - one definition of gravity is that it's the attraction of every body in the universe to every other body due to the masses of each.

Gravity does weaken the farther you go from the body, that's why astronauts can float around up in orbit, not plummet towards earth (like Baumgartner or Kittinger)

That'll be Newton's Law of Universal Gravitation, which is that there is a force of attraction between every single thing in the Universe that has mass, as you said, but that we don't feel the force between us and, say, the desk you are sitting at or the person across the room from you because the force between us and the earth is much stronger.

Also, it's an inverse square law, that that the further you move away from an object, the more dramatic the decrease the gravitational force will be.

I love all this space physics stuff!

Queen-Mise

If gravity is directly connected to the mass of the body - then laws of physics must be different for everything in the universe... Would this be correct?

A rock & feather wouldn't fall at the same speed from a skyscraper on Mars...

This must make space physics extremely complicated.


Thanks for the cartoon - that is brilliant.

norrie rugger

Queen-Mise wrote: »

If gravity is directly connected to the mass of the body - then laws of physics must be different for everything in the universe... Would this be correct?

A rock & feather wouldn't fall at the same speed from a skyscraper on Mars...

This must make space physics extremely complicated.


Thanks for the cartoon - that is brilliant.

There is an atmosphere on Mars that would slow down the feather.
The reason that a hammer and feather fall at different rates, on Earth, is because of air resistance. The hammer is dense enough to push through the air.
You need to get to huge mass/density to affect the laws of physics, such as a black hole

Look at this video, from the moon. The moon exerts the same gravitational effect on both the hammer and feather. Because there is no air in the way to slow the feather, they fall at the same rate

https://www.youtube.com/watch?v=5C5_dOEyAfk

smash

Anyone know anything about this?

The image--taken by the right Mast Camera during the mission's 61st Martian day--shows Curiosity's robotic arm's scoop full of sand and dust, waiting to be deposited inside its analysis unit. But, after looking closer at the photo, someone noticed that unusual bright piece.

The scooping operation was then halted and the rover was instructed to take a closer look of the object, which hasn't arrived yet to ground control.

Knifey Spoony

Queen-Mise wrote: »

If gravity is directly connected to the mass of the body - then laws of physics must be different for everything in the universe... Would this be correct?

A rock & feather wouldn't fall at the same speed from a skyscraper on Mars...

No, the laws of physics are the same in all parts of the Universe.

Since the mass of Mars is different to the Earth's, we know that gravity must be different on both planets, which is correct.Also, take the strength of this gravitational field to be equal to the acceleration of objects in this field (i.e. how fast you would accelerate back to the surface of the Earth after jumping off something high).

So, if we have different planetary masses then there must be a different acceleration due to gravity on Earth and Mars. This acceleration effects all objects equally on a given planet, so if you dropped two items from a height on Mars, both of them would accelerate at the same speed and thus, hit the ground at the same time, just like on Earth. But, because of the different masses and radii of Earth and Mars, this acceleration is smaller on Mars than on Earth, so the rock and feather would take a longer time to hit the ground on Mars than on Earth for the same height.

This is assuming that air resistance is not taken into account, as this effects the feather more than the rock and is why a rock will hits the ground before a feather if they are dropped from the same height. But, this is also as true on Earth as it is on Mars.

But, ideally (ignoring air resistance), a rock and a feather will hit the ground at the same time on both Earth and Mars, just it will take longer to happen on Mars then on Earth.

Here's the formula for that acceleration if you are interested:

g = (G*m)/r^2, where g is the acceleration due to gravity, G is a constant, m is the mass of the planet and r is the radius of the planet.

g = 9.81 m/s^2 on Earth and 3.8m/s^2 on Mars.

I really hope that I haven't confused you now

norrie rugger

smash wrote: »

Anyone know anything about this?

Here's hoping that something has not broken off of the rover



*EDIT*
Looks to be natural and they are hitting it with the ChemCam laser

BBC wrote:

Engineers have been concerned at the number of small pieces of man-made debris they are seeing around the rover. These are likely bits of plastic that have fallen off the vehicle, or were deposited on to it by its landing crane and have since dropped to the ground during the drive.

The team is not worried that these debris items indicate a major breakage on Curiosity; rather, the issue is that the objects could accidentally be picked up in the scoop and be ingested by the laboratories, seriously skewing their analyses.

Engineers commanded the rover to dump one scoop when a bright fleck was seen during the dig.

However, later imaging suggested this item was probably natural Martian material, and the scientists will now hit the 2mm-wide grain with the ChemCam laser spectrometer to probe its properties further and to work out why it appears so much brighter than all the material around it

ScumLord

Queen-Mise wrote: »

I can work with the magnet analogy - it pulls everything not just metal. Does an object in space need an atmosphere to have gravity? Would a really, really, big asteroid have gravity?

Everything has gravity, it's just the bigger it is the more gravity it has. You can take it that anything smaller than mount everest probably isn't big enough to have enough gravity that you'd notice.

--Kaiser-- wrote: »

All things have gravity - one definition of gravity is that it's the attraction of every body in the universe to every other body due to the masses of each.

Yet everything in the universe is moving away from each other.

Knifey Spoony

ScumLord wrote: »

Yet everything in the universe is moving away from each other.

There is obviously some force causing this expansion that must be much greater than the gravitational force acting on everything.

My guess is that the force of the big bang is is causing this expansion (this is my own thoughts, nothing really to back it up). What is interesting though is the possible scenarios that this expansion vs. gravitational force could result in.

There is the Big Freeze, where everything in the Universe just keeps expanding and eventually just reaches a state of entropy. What that means for the Universe I'm not really sure.

Then, there is the Big Crunch, where if there is another mass in the Universe, then eventually the expansion would stop and everything would start contracting. I've seen it suggested that the crunch could lead to all matter reducing to a singularity and the Big Bang could happen again. Which could propose that this expansion and contraction could be a regular occurrence. Which is a bit mind blowing!

Then there is the Big Rip, where the Universe just keeps expanding and everything just tears itself apart.

I find this stuff really fascinating.

ScumLord

You could get the same results as the big bang if our universe was shot out of a canon. It would explain expansion and dark flow.

How do I go about submitting my thesis? That's it up there, do I need to bulk it out more for the sciency types?

Prick!

What about a gas like helium? Lighter than air. What point is there against that anything heavier than air drops?

Queen-Mise

Knifey Spoony wrote: »

No, the laws of physics are the same in all parts of the Universe.

Thank you for the explanation. I followed all of it up to the formulas :rolleyes:

So physics as we know it - is applicable to any planet taking into account that planet's gravity & air density.

On another note - my 11 year old son told me yesterday, that they discovered trees on a planet somewhere. I think he may have gotten something mixed up though.

KAGY

Prick! wrote: »

What about a gas like helium? Lighter than air. What point is there against that anything heavier than air drops?

You actually answered your own q there, helium is lighter than air so it floats up. A balloon with helium somewhere with no atmosphere would fall to the ground like everything else. The same as a ship would fall to the bottom of the ocean if there was no water.
As far as what height do things start falling, there is no definite answer, it depends on when the gravity from something else is greater,
The reasons satellites stay up there is because they're spinning and because of that trying to move away.

Prick!

KAGY wrote: »

You actually answered your own q there, helium is lighter than air so it floats up. A balloon with helium somewhere with no atmosphere would fall to the ground like everything else. The same as a ship would fall to the bottom of the ocean if there was no water.
As far as what height do things start falling, there is no definite answer, it depends on when the gravity from something else is greater,
The reasons satellites stay up there is because they're spinning and because of that trying to move away.

What about space where there is no atmosphere? wouldn't it just float?

Knifey Spoony

Queen-Mise wrote: »

Thank you for the explanation. I followed all of it up to the formulas :rolleyes:

So physics as we know it - is applicable to any planet taking into account that planet's gravity & air density.

On another note - my 11 year old son told me yesterday, that they discovered trees on a planet somewhere. I think he may have gotten something mixed up though.

I probably should have stopped before the formula, but I was on a roll. :P
But, yeah, all the laws of physics that apply here on Earth, apply anywhere in the Universe.

Don't think the tree thing has happened. Would be a huge deal if it was, proving that there is life on other planets. Even the discovery of something much, much less evolved than a one celled organism anywhere outside of Earth would be huge.

KAGY

smash wrote: »

Anyone know anything about this?

There's gold in them thar hills...*

* not an actually scientific opinion, all resemblance to truth is purely coincidentual

KAGY

Prick! wrote: »

What about space where there is no atmosphere? wouldn't it just float?

It depends on all the forces working on it. if it was far enough away from anything it would just sit there. Not exactly float because that means it's lighter than what it's sitting in. So it would sit there until something moved it ( like the gravity from a large passing ufo or a nudge from a comet) then it'd keep moving in that direction forever.

KAGY

ScumLord wrote: »

You could get the same results as the big bang if our universe was shot out of a canon. It would explain expansion and dark flow.

How do I go about submitting my thesis? That's it up there, do I need to bulk it out more for the sciency types?

Yes you would need to show a rigorous scientific process. E.g.

Experiment to show the universe was shot out of a canon
Apparatus

• Canon
• Baby universe seed
• retort stand (you always have to have one of these for some reason)

Expected Results
The universe will keep expanding
Method

• Light fuse
• Stick fingers in ears
• Measure expansion with universe measuring device (patent pending)
• Plot results on graph, 1 millon light years to one box

Actual Result
Strange growth on small part of universe, seems to be spreading to other planets
Conclusion
Equipment was not sterile enough, discard experiment and repeat in different dimension.

You have to list me as co-author now!

KAGY

smash wrote: »

Anyone know anything about this?

I'll get me coat...

Capt'n Midnight

Queen-Mise wrote: »

I can work with the magnet analogy - it pulls everything not just metal. Does an object in space need an atmosphere to have gravity? Would a really, really, big asteroid have gravity?

Do gravity weaken the further into the sky/atmosphere you go?

Magnets are weird.
Bismuth is nearly as dense as lead. It is repealed by strong magnetic fields, if the field is strong enough it will float. Frogs can be levitated by even stronger magnetic fields. When you start looking at quantum levitation it gets even stranger.

In short magnets can be used as anti-gravity, but only for ridiculously strong magnetic fields compared to the normal sort you get in something like an MRI scanner.


Gravity is weak.
It's only strong because it's cumulative and there is no repulsive force. It takes a lot of energy to remove all the electrons from an atom of copper. To remove all the electrons from 1 Kg of copper is about the same energy as needed to split the earth in two.