Ask a physicist anything.

[laconicstudent]

Resident physicist: There is someone in this thread: http://www.christianforums.com/t7419509/

Who is either trolling (likely) or genuinely believes that acceleration due to gravity is affected by mass when in media... Apparently if things are put in water, gravitation changes so that acceleration due to gravity is due to mass. It pains me.

 

[catzrfluffy]

What happens if you press the red button?

 

[Wiccan_Child]

Resident physicist: There is someone in this thread: http://www.christianforums.com/t7419509/

Who is either trolling (likely) or genuinely believes that acceleration due to gravity is affected by mass when in media... Apparently if things are put in water, gravitation changes so that acceleration due to gravity is due to mass. It pains me.

Density does actually play a role in how fast things sink through a fluid: two objects of the same shape but different densities will move differently. A solid lead pellet will sink very fast, while a hollow, air-filled pellet of lead will sink more slowly (or may even float).
Effectively, in a viscous medium such as water, objects hit their terminal velocity very quickly. If the density of the object is less than the fluid, it will float. If it's more dense, it will sink. The greater the discrepancy, the quicker it moves.

But it's not gravity that changes. Gravity is always the same.

Plus, I think he's a troll.

 

[Wiccan_Child]

What happens if you press the red button?

The world reboots.

 

[Wiccan_Child]

Here's a question for everyone: do you know why things go darker when wet?

 

[Wiccan_Child]

Oh, and this thread is the fifth most viewed, and top most replied to thread in the whole P&LS forum! That deserves some sort of award, I'm sure.

 

[Cabal]

Here's a question for everyone: do you know why things go darker when wet?

Doesn't water scatter all wavelengths of light?

 

[Chesterton]

Here's a question for everyone: do you know why things go darker when wet?

I think, more light is absorbed by the extra water molecules present?

On a related note, I was going to ask why plants are green. There are a few plants which are dark purple, and it seems that cholorphyll should produce that pigment most, or a dark grey or black, in all plants, because that would be using the available light most efficiently, right? So why aren't plants black?

Oh, and this thread is the fifth most viewed, and top most replied to thread in the whole P&LS forum! That deserves some sort of award, I'm sure.

Your virtual prize is virtually on the way.

 

[Tinker Grey]

Here's a question for everyone: do you know why things go darker when wet?

The Straight Dope: Why do wet things look darker than dry things?

Essentially, the answer as given by Cabal and Chesterton seems correct. Water scatters the light. And, the more scattered it is the more the energy is absorbed.

 

[Cabal]

Similar reasoning as to why clouds are white/optically broadband emitting....

 

[Gracchus]

On a related note, I was going to ask why plants are green. There are a few plants which are dark purple, and it seems that cholorphyll should produce that pigment most, or a dark grey or black, in all plants, because that would be using the available light most efficiently, right? So why aren't plants black?

Chlorophyll absorbs primarily in the red band. That is just a fact of physical chemistry. In plants with red or purple leaves the cholorophyll is masked by other pigments. There may be other pigments than chlorophyll that would be more efficient at capturing energy in a form that could be released by metabolic processes, but chlorophyll won the race.

A designer might have hunted around for the most efficient pigment, but evolution works on what is already at hand.

 

[Chesterton]

Chlorophyll absorbs primarily in the red band. That is just a fact of physical chemistry. In plants with red or purple leaves the cholorophyll is masked by other pigments. There may be other pigments than chlorophyll that would be more efficient at capturing energy in a form that could be released by metabolic processes, but chlorophyll won the race.

The race is over? Efficiency should win in the long run. How long is the run?

A designer might have hunted around for the most efficient pigment, but evolution works on what is already at hand.

No, I think evolution would have done what is most efficient, but a designer might have done what is pretty.

Hi, how are you?

 

[TerranceL]

Oh, and this thread is the fifth most viewed, and top most replied to thread in the whole P&LS forum! That deserves some sort of award, I'm sure.

Grats man, it is an awesome thread.

 

[catzrfluffy]

How many roads must a man walk down, before you can call him a man?

 

[pgp_protector]

How do I enable cookies in a form using the System.Windows.WebBrowser COM Object in C Sharp or C++ ?

 

[Doveaman]

Oh, and this thread is the fifth most viewed, and top most replied to thread in the whole P&LS forum! That deserves some sort of award, I'm sure.

Yes, for all of us.

 

[JusSumguy]

Loaded questions......

Is the earth really warming? And if so, is man's input making any difference?

Bonus question...

If man had not been pumping greenhouse gasses, would we be deeply locked in an ice age right now?


-

 

[canehdianhotstuff]

Density does actually play a role in how fast things sink through a fluid: two objects of the same shape but different densities will move differently. A solid lead pellet will sink very fast, while a hollow, air-filled pellet of lead will sink more slowly (or may even float).
Effectively, in a viscous medium such as water, objects hit their terminal velocity very quickly. If the density of the object is less than the fluid, it will float. If it's more dense, it will sink. The greater the discrepancy, the quicker it moves.

But it's not gravity that changes. Gravity is always the same.

Plus, I think he's a troll.

Incorrect, gravity is only constant at a certain elevation...the deeper you go into the earth (eg. mine shafts and such) gravity actually changes as you now have mass above you and mass below you. Gravity at the centre of the earth should be zero. Things floating is not density dependent, but if the object is able to displace enough water equal to its weight without sinking. (eg. I can have a block of lead of density 11.35g/cm3 that will sink, or I can take the same block and mold it into a larger surface area so it can displace more water and now float, the density of the lead is still the same.

 

[Cabal]

Loaded questions......

Is the earth really warming? And if so, is man's input making any difference?

As far as I know the earth is warming - and while I personally don't think we're on the brink of disaster as such, the simple facts are CO2 absorbs and traps infrared, it can't escape the Earth's atmosphere, we make a lot of it, and if that causes heating it will make a lot more greenhouse gas by evaporating more water.

We may not be having an input now, but carrying on at the rate we're going and we will do - but I suspect we may have the increasing scarcity of fossil fuels to moderate that somewhat, who knows.

Bonus question...

If man had not been pumping greenhouse gasses, would we be deeply locked in an ice age right now?


-

Hard to say as we've hardly been giving up those gases in significantly large amounts on geological timescales.

 

[Doveaman]

Loaded questions......

Is the earth really warming?

Mars is warming too.

And if so, is man's input making any difference?

Not on Mars for sure.

Bonus question...

If man had not been pumping greenhouse gasses, would we be deeply locked in an ice age right now? -

Probably not. We are not pumping any greenhouse gasses on Mars.