Behold the Mountains of Mars!

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.