Astronomers use doppler shifts to calculate precisely how fast stars and other astronomical objects move toward or away from earth. for example the spectral lines emitted by hydrogen gas in distant galaxies which is normally found at a wavelength of 21 centimeters on earth, might be observed at 21.1 centimeters instead. what would this difference indicate to astronomers?

Galaxy is moving away from Earth.

Explanation:

Doppler shifts in the spectrum indicate about the motion of celestial bodies. Doppler effect is the apparent change in wavelength or frequency when there is relative motion between the source and the observer. Red-shifted light indicates that celestial body is moving away and blue-shifted light indicates that it is moving closer.

When astronomers observe a wavelength of 21 cm to be shifted to 21.1 cm - it means the light is red-shifted because the apparent wavelength is longer. Thus, astronomers can conclude that from the difference in the wavelengths that the galaxy is moving away from the Earth.

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.

this would be about 43%