Hubble noticed that the galaxies were moving away from us, which meant the universe was expanding.
This is why constellations change over time. In some years, the Big Dipper won't actually look like a dipper anymore.
Answer:
D. a person pulling a sled.
Explanation:
contact force only occurs when something directly comes in contact with another object.
a. is wrong because that is called magnetic force.
b. gravitational force
c. is an electrical force
Answer:
T = 0.003 s
(Period is written as T)
Explanation:
Period = time it takes for one wave to pass (measured in seconds)
frequency = number of cycles that occur in 1 second
(measured in Hz / hertz / 1 second)
Period : T
frequency : f
So, if we know that the frequency of a wave is 300 Hz, we can find the period of the wave from the relation between frequency and period
T = 
f = 
to find the period (T) of this wave, we need to plug in the frequency (f) of 300
T = 
T = 0.00333333333
So, the period of a wave that has a frequency of 300 Hz is 0.003 s
[the period/T of this wave is 0.003 s]
Answer: To focus on a near object – the lens becomes thicker, this allows the light rays to refract (bend) more strongly. To focus on a distant object – the lens is pulled thin, this allows the light rays to refract slightly.
Explanation:
Answer: It would destroy the Earth's surface.
I remember reading this questions in What If? by Randall Munroe. Great book, I suggest you check it out. Anyway, the answer. The Earth is revolving as well as spinning on its axis at the same time. This basically means that thee atmosphere is also spinning at the same speed. But due to the frame of reference, we don't notice anything. If the Earth suddenly stops spinning, then the atmosphere, going according to the first law of motion will still be spinning at the same speed. This would produce supersonic winds at such a scale that it will be compared to an atomic explosion. Anything not in a nuclear bunker will probably be ripped apart by the force of the wind.
