Isaac Newton's first law of motion states that an object at rest tends to stay at rest, while an object in motion tends to stay in motion unless an external force acts upon it. When a basketball player shoots, it would appear that there is nothing to obstruct the ball.

On an uncharacteristically tropical morning in the San Francisco Bay Area, the ground shimmers with waves of heat, and it’s impossible to look to the sky without squinting. But the real heat is inside the Lockheed Martin Solar and Astrophysics Laboratory in Palo Alto. There, in a dark room stacked with computer processors, a high-definition view of the Sun fills nine conjoined TV screens to create a seven-foot-wide, theater-quality solar extravaganza.

According to Newton's first law, an object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force. It is the natural tendency of objects to keep on doing what they're doing. All objects resist changes in their state of motion. In the absence of an unbalanced force, an object in motion will maintain its state of motion. This is often called the law of inertia.

The First Law of Motion means that objects that have greater momentum also have greater inertia. A stationary object will require a push or a pull to set it in motion. When the net force on an object is zero, its speed and direction of motion will remain unchanged. This is true for both stationary objects as well as those already in motion.

The discovery that the expansion of space is accelerating presents one of the most important scientific problems of our time. The implication that the universe is dominated by an unknown entity, now called "dark energy," that counters the attractive force of gravity, may revolutionize our understanding of cosmology and fundamental physics.

One of the most exciting problems in physics today is the fact that there is far more matter in the universe than we can see. The motion of stars in galaxies and the motion of galaxies in clusters imply that there is about 10 times as much mass as in the luminous objects we can see.

The law of reflection states when light reaches a mirror, it reflects off the surface of the mirror:
the incident ray is the light going towards the mirror the reflected ray is the light coming away from the mirror. Ray diagrams show what happens to light in mirrors and lenses.

The Physics Classroom discusses the physics of mirrors, plane, concave and convex. Reflection and image formation for mirrors, ray diagrams and image characteristics are discussed.

Telescopes are meant for viewing distant objects, producing an image that is larger than the image that can be seen with the unaided eye. Telescopes gather far more light than the eye, allowing dim objects to be observed with greater magnification and better resolution. Although Galileo is often credited with inventing the telescope, he actually did not. What he did was more important. He constructed several early telescopes, was the first to study the heavens with them, and made monumental discoveries using them. Among these are the moons of Jupiter, the craters and mountains on the Moon, the details of sunspots, and the fact that the Milky Way is composed of vast numbers of individual stars.

A force can be a push or a pull. For example, when you push open a door you have to apply a force to the door. You also have to apply a force to pull open a drawer.

Different forms of energy can be transferred from one form to another. Energy transfer diagrams show each form of energy - whether it is stored or not - and the processes taking place as energy is transferred.
The energy transfer diagram below shows the useful energy transfer in a car engine. You can see that a car engine transfers chemical energy, which is stored in the fuel, into kinetic energy in the engine and wheels.

The popular British astrophysicist, now touring Down Under, says cutting back on our energy use by turning off lights and air conditioning is not the answer. And neither is commissioning extra power plants.
Instead, he says we should move the production of energy away from Earth and into outer space, and our planet should become purely residential.

ARCTIC THAW - Across nine million square miles at the top of the planet, climate change is writing a new chapter. Arctic permafrost isn’t thawing gradually, as scientists once predicted. Geologically speaking, it’s thawing almost overnight. As soils like the ones at Duvanny Yar soften and slump, they’re releasing vestiges of ancient life—and masses of carbon—that have been locked in frozen dirt for millennia. Entering the atmosphere as methane or carbon dioxide, the carbon promises to accelerate climate change, even as humans struggle to curb our fossil fuel emissions.

Plastics travel on ocean currents and through the air to the far north and accumulate—sometimes inside the animals that live there.