__ is the apparent in the position of an object when viewed from two locations

What would the difference of spectral lines emitted by hydrogen gas in distant galaxies which is normally found at a wavelength of 21 cm on earth, be observed at 21.1 centimeters?

Which of the following could represent a single-replacement reaction? a. element + compound = element + compound b. element + element = compound c. compound +compound = compound + compound d. compound = element + element

When conducting this experiment, some procedures call for heating the substance several times and recording the mass after each heating, continuing until the mass values are constant. explain the purpose of this process and how it might reduce errors.