gravity

[Douglass]

Are there studies that show that earths gravity and consequently earths mass has changed significantly? I wonder if this could link to the death of the giant dinosaurs.

[studiot]

There is no evidence of significant mass change for the Earth since the original accretion phase in the history of the solar system 4 billion+ years ago.

 

This accretion phase cleared most of the available material in our vicinity so we only get the odd wanderer or loose the odd atmospheric molecule nowadays.

.

Edit, Note the dinosaurs died out about 60 million years ago, a mere eyeblink in relation to the Earth's age. Also this was not the biggest mass extinction event, which occurred nearly 200 million years before the dinosaurs

Edited July 8, 2016 by studiot

[Strange]

About 100 tons of dust fall on the Earth every day. This is, as studiot says, a minute amount.

 

Overall, the Earth loses a tiny amount of mass each year. A nice analysis here: http://www.bbc.co.uk/news/magazine-16787636

[Douglass]

Can the same be said for change of density / diameter of earth?

[studiot]

To the best of our knowledge, yes.

[Sensei]

Radius of the Earth is 6371000 meters,

area of sphere is

[math]A=4 \pi r^2[/math]

 

so

[math]4*3.14159265*6371000^2 = 510,064,471,909,788 m^2[/math]

 

Every increase of radius by d=1 mm = 0.001 m

would increase volume by approximately

[math]A*d=510,064,471,909 m^3[/math]

 

Density of water is 1000 kg/m^3,

ice is 934 kg/m^3,

average density of the Earth is ~5505 kg/m^3,

density of iron is ~7874 kg/m^3.

 

So if it would be just ice comet.

It would have to have mass:

[math]m=p*V=476,400,216,763,006 kg[/math]

(double as much as Halley's Comet according to wikipedia)

 

We can reverse question and equation.

"What would have to be radius of comet/asteroid to have such volume/mass?"

[math]V=\frac{4}{3} \pi r^3[/math]

[math]r=\sqrt[3]{\frac{3 V}{4 \pi}}[/math]

[math]r=4956 m[/math]

Diameter ~10 km

 

Halley's Comet has mean diameter 11 km..

 

According to

https://en.wikipedia.org/wiki/Asteroid

there is ~12000 objects with diameter larger than 10 km in the solar system.

Edited July 9, 2016 by Sensei