Newton's Gravity
The force that attracts every object with mass to every other object.
Gravity
The shape of every planet's orbit.
An ellipse
This unit measures distances inside the solar system.
The AU (astronomical unit)
The innermost layer, where fusion happens.
The core
In the Sun, four nuclei of this element fuse into one helium nucleus.
Hydrogen
If the mass of one object triples, the gravitational force between the objects does this.
It triples
The point in an orbit that is closest to the Sun.
Perihelion
The distance light travels in one year.
A light-year
The visible 'surface' of the Sun that gives off the light we see.
The photosphere
The process in which light nuclei combine to form a heavier nucleus.
Nuclear fusion
If the distance between two objects doubles, the force becomes this fraction of what it was.
1/4 as strong
A planet moves slowest at this point in its orbit.
Aphelion
One AU is about this many million kilometers.
149.6 million km (the average Earth-Sun distance)
In this layer, energy is carried outward by rising and sinking hot plasma.
The convective zone
The small amount of 'missing' mass that becomes energy in fusion.
The mass defect
This law says gravitational force is inversely proportional to the square of the distance.
The inverse square law
The farther a planet is from the Sun, the longer its this.
Orbital period
Sunlight takes about this long to reach Earth.
About 8 minutes
This thin, irregular layer separates the chromosphere from the corona.
The transition region
Fusion only happens in the core because only the core has these two extreme conditions.
High temperature and high pressure
Two objects pull on each other with 100 N. The distance triples. The new force is about this many newtons.
About 11 N (100 divided by 9)
Astronauts appear weightless because they and their spacecraft are in this.
Free fall
Mars takes 1.88 Earth years to orbit and Venus takes 0.62.What does this reveal about Mar's distance from the Sun compared to Venus?
Mars is much farther from the Sun
The correct order of the first four layers from the core outward.
Core, radiative zone, convective zone, photosphere
The equation that shows mass can become energy.
E = mc²