17 replies to this topic

[big eye]

Get your head around this. The temperature and distance of Alpha Centauri is the equivalent of a powerful 6-inch diameter spotlight at a distance of 3000 miles WOW. Share some scale and facts with us.

[Couder]

Each of us is insignificant when looking at the or compared to the Universe, but then we are the ones doing the looking.

[Gipht]

There could be 5 billion habitable planets in the Milky Way.

[big eye]

There could be 5 billion habitable planets in the Milky Way.

And there might only be one inhabited?

[Steve OK]

On a scale in which the distance between Earth and the Moon were reduced to the thickness of a sheet of paper, the Sun would be an inch away, and a light year would be a mile.  The nearest star would be 4.6 miles away.  So far, humans have traversed the thickness of a sheet of paper.

 

Steve

[big eye]

On a scale in which the distance between Earth and the Moon were reduced to the thickness of a sheet of paper, the Sun would be an inch away, and a light year would be a mile.  The nearest star would be 4.6 miles away.  So far, humans have traversed the thickness of a sheet of paper.

 

Steve

And on that scale one mile = one light year.

[Dave Mitsky]

There are 1,625,000 grains of salt in a typical 26oz package of Morton's Salt. To account for all the stars in the Milky Way, one would have to purchase approximately 18,462 boxes of salt.  One bathtub filled with Morton's table salt will hold about 1 billion grains of salt so approximately 300 bathtubs full of salt would be needed. No two grains of salt can be any closer than seven miles to each other. The model will fit into the area encompassed by Mercury's orbit around the Sun.

[big eye]

There are 1,625,000 grains of salt in a typical 26oz package of Morton's Salt. To account for all the stars in the Milky Way, we would have to purchase approximately 18,462 boxes of salt.  One bathtub filled with Morton's table salt will hold about 1 billion grains of salt so approximately 300 bathtubs full of salt would be needed. No two grains of salt can be any closer than seven miles to each other. The model will fit into the area encompassed by Mercury's orbit around the Sun.

This would be like 1 billion atoms spread out on a football field.

[Gregrox]

"If an apple were magnified to the size of the Earth, then the atoms in the apple would be approximately the size of the original apple."

[Tony Flanders]

If Earth was at the center of the Sun (and didn't evaporate), the Moon's orbit would fit inside the Sun with ample room to spare.

[Dave Mitsky]

Let the Earth be represented by a peppercorn with a diameter of 0.08 inch.  One inch would then equal 100,000 miles (160,934 kilometers) in this model.  The distance from the Sun, which would be the size of a bowling ball, to the Earth would be 26 yards (24 meters) and the average distance from the Sun to Pluto would be about 1,109 yards (932 meters).  The distance from the Sun to Proxima Centauri would be approximately 4,000 miles (6,437 kilometers).

https://www.noao.edu...orn/pcmain.html

 

[beatlejuice]

If an atom were blown up to the size of a football field the nucleus would look like a pea at midfield with the electrons buzzing around the outer reaches of the stands. We are all empty-headed 

 

Eric

[Dave Mitsky]

Snapple cap fact #206

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[russell23]

Here is an interesting one which should make sense: an Earth composition planet (~1/3 Fe and 2/3 silicates by mass) cannot have the same density as the Earth unless it has a mass close to the Earth’s.   As planet mass increases, density increases for a given composition.  The Earth’s density is 5.51 g/cm^3.   Using published mass-radius models here are some examples:

 

2.0 Earth mass  & composition planet would have a radius of 1.22 Earth radii and a density of 6.07

 

8.0 Earth mass & and composition planet would have a radius of 1.75 Earth radii and a density of 8.23

 

One of the most massive Earth-like composition planets is Kepler 131b which has a mass of 16.13 Earth masses and a radius of 2.1 Earth radii.  This puts it on the 20% Fe and 80% silicates composition line - so a little less iron rich than Earth.  But its density is 9.61 g/cm^3

 

So watch out for density when you see reports on exoplanet discoveries.  An Earth density does not mean an Earth composition.  As an example, there is K2-180b:  Mass = 11.45 Earth, Radius = 2.24 Earth, Density = 5.61 which is close to Earth’s density.  However, it falls close to the 25% H2O and 75% silicates/iron composition line on the Mass-Radius relation so decidedly un-Earth like.  

 

Perhaps K2-180b is more Ganymede-like in composition.  However, one recent paper showed that these super-Earth to Neptune mass exoplanets with a Ganymede-like composition will not have the separate rock and water layers in the interior.  At the pressure/temperature conditions inside these massive planets the rock and water are >99% miscible and therefore the interior may have density gradients but not distinct layers of different composition as is seen in the icy Satellite planets of the Solar System.  The water and rock in these planets will be fully mixed.

 

Anyway, the point is, in terms of scale, that for a given composition, density increases with planet mass.   So an Earth density planet will not be Earth-like in composition if it has a significantly different mass.  

Edited by russell23, 25 November 2020 - 11:55 PM.

[Bill Weir]

The temperature of the core of Earth is approximately the same as the surface of the Sun.

 

Bill 

[ButterFly]

1) Degenerate stars (white dwarfs, neutron stars) get smaller the more mass you add.

 

2) The surface gravity at the event horizon of [non-rotating] supermassive black holes is much much less than that of stellar sized black holes.

 

And, 3) one of my favorite WikiMedia pictures:

 

Edited by ButterFly, 26 November 2020 - 06:38 AM.

[MajorTom2017#]

The cameras in the Kepler Space Telescope have to be incredibly sensitive to see the dimming of a star during a planet transit. It can "see" a light reduction of about 20 parts per million. This is equivalent to seeing a flea pass in front of a car head light at a distance of several miles away.

[MajorTom2017#]

I believe it was Carl Sagan (or maybe Stephen Hawking) who said with every breath you take you probably inhale at lease one atom from Julius Caesar's last breath as he exclaimed "Et tu Brute?"