A spaceship is propelled by burning fuel at a rate of 1000 pounds per second at launch. But as we on earth observe the ship approaching the speed of light, the faster the ship goes, the more the acceleration decreases. And the observed acceleration decreases exactly enough to ensure that it will never reach the speed of light. Why does the acceleration decrease?
Underlined. They only cancel if division by 0 is permissible, which of course it isn't. If the equatorial circumference is 24,000 miles, the gap will be ~2". It's tidally locked, so its angular velocity WRT its own center of mass equals its angular velocity WRT Earth's CoM. The simplest solution is to note that the arrow does in fact cover a finite distance in a finite amount of time; but if one insists on breaking it down further, just as there is an infinitude of points between any two points in space, there is an infinitude of moments in any timespan, so that while there is an infinitude of points, the time required to get from one to the next is infinitesimal. One could go into dx/dt and so on, but I think I've probably taken it too far already. My guess is there aren't as many colors of paint as there are wavelengths in the visible spectrum, and manufacturers are producing colors that sell rather than taking care that all colors are represented.
Centre of mass of the Earth, or the universe ? (after all, every mass exerts a force on every other - albeit that the inverse square law ensures that very distant objects exert a negligible force)
Paints reflect light. Mixing light of the primary colours will give near white light. Mixing of the primary colours of paint will give near black but won't be seen without that white light - is that green door green if you don't look at it
In particular, paint and other objects reflect the color that their not. The colors of light are additive. Paints subtract.
What is interesting about THAT is that the circumference of the earth doesn't matter. You get the same answer if you use a 6" ball... or a point and 1 foot of string.
Hold your hand about six inches from your face. Extend your index finger and align it with your line of sight using one eye. Align a bright light source [like a light bulb across the room] with your line of sight and finger - along the edge of your finger, just below your fingertip. Note how the edge of your finger becomes fuzzy [not well defined] when you look along your finger at the light. What is this?
If you have bad vision and can't read some fine print, you can punch a small hole [a pinhole just big enough to see through] in a piece of paper and read the print through the hole. The print will magically appear in focus. Why?
What is the difference between the force of gravity, and the force you feel when you accelerate in your car - assuming you could accelerate quickly enough to match the force of gravity.
